title: Fast bowling

text: A ball rotating around the seam moves either right or left when it hits the pitch, depending on which way the ball is spinning. A ball bouncing to the right is said to be an off cutter as it is travelling from off stump to leg stump for a right-handed batsman. Conversely, a ball that bounces to the left is a leg cutter, travelling from leg to off stump for a right-handed batsman. Cutters are usually aimed so that they hit the pitch just outside the batsman's off stump and move away from the wicket. This makes the ball catch the outside edge of the bat instead of the middle, and fly up to be caught in the slips.


title: Fast bowling

text: To bowl a cutter, the bowler uses a different grip. The two grips are shown to the right, with the uppermost one producing a leg cutter while the lower one shows the grip required for an off cutter. As well as changing the grip, the bowler must pull his or her fingers down the appropriate side of the ball as it leaves their hand to impart the required spin. The action of bowling a cutter also increases drag on the ball as it leaves the hand, causing the ball to slow in the same way as a slower ball and this can also help to confuse the batsman.


title: Fast bowling

text: Swing bowlers cause the ball to move laterally through the air, rather than off the pitch like seam bowlers. Normal or conventional swing bowling is encouraged by the raised seam of the ball, and conventional swing is usually greatest when the ball is new and therefore has a pronounced seam. As the ball gets older, the wear makes swing more difficult to achieve, but this can be countered if the fielding team systematically polishes one side of the ball while allowing the other to become rough. When the ball has been polished highly on one side and not on the other and if the ball is bowled very fast (over ), it produces a reverse swing such that the ball swings in the opposite direction as in conventional swing. Contrary to popular opinion, this swing is not produced by air flowing faster over the smooth or "shiny" side as compared to the rough side.


title: Fast bowling

text: Swing is produced due to a net force acting on the ball from one side; that is, the side with the more turbulent boundary layer. For conventional swing bowling, the raised seam and the direction it points governs the direction of swing. Due to the angled seam of the ball, air flowing over the seam produces turbulence on the side that the seam is angled toward. This causes the boundary layer to separate from the surface of the ball later (farther toward the rear of the ball) than the other side where it separates earlier (farther forward on the surface). The resulting net force acts so as to move or swing the ball in the direction of the angled seam. Conventional swing bowling is delivered with the seam angled such that the smooth or polished side of the ball faces forward to move the ball in the direction of the seam "i.e." toward the rough side.


title: Fast bowling

text: A swinging ball is classed as either an outswinger, which moves away from the batsman, or an inswinger, which moves in toward the batsman. In most cases the outswinger is seen as the more dangerous ball because, if the batsman fails to recognise it, it catches the outside edge of the bat instead of the middle and fly up to be caught in the slips. Inswingers have their place too, especially combined with the yorker as this can result in the ball either breaking the wicket (by going clean "through the gate" or getting an inside edge) or hitting the pad rather than the bat (resulting in a possible LBW decision).


title: Fast bowling

text: Swing bowling can also be roughly categorised as early swing or late swing, corresponding to when in the trajectory the ball changes direction. The later the ball swings, the less chance the batter has of adjusting to account for the swing.


title: Fast bowling

text: Bowlers usually use the same grip and technique on swing balls as fast balls, though they usually keep the seam slightly rather than straight, and may use the slower ball grip. It is difficult to achieve swing with a cutter grip since the ball spins in flight, varying the orientation of the shiny and rough surfaces as it moves through the air. Many players, commentators on the game, and fans agree that swing is easier to achieve in humid or overcast conditions, and also that the red ball used in Test cricket swings more than the white ball used in the one-day game.


title: Fast bowling

text: Reverse swing is a phenomenon that makes the ball swing in the opposite direction to that usually produced by the orientation of the shiny and rough sides of the ball. When the ball is reverse swinging, the ball swings towards the shiny side. Balls that reverse swing move much later and much more sharply than those swinging conventionally, both factors increasing the difficulty the batsman has in trying to hit the ball. At speeds of over 90 mph a ball always exhibits reverse swing, but as roughness increases on the leading side, the speed at which reverse swing occurs decreases. This means that an older ball is more likely to be delivered with reverse swing as its surface is roughened through use.


title: Fast bowling

text: In reverse swing the seam is angled in the same way as in conventional swing (10–20 degrees to one side) but the boundary layer on both sides is turbulent. The net effect of the seam and rough side is that the ball swings in the direction opposite to where the seam is pointing to. The turbulent boundary layer separating later is similar to the effect produced by dimples in a golf ball. In case of the golf ball, turbulence is produced on both sides of the ball and the net effect is a later separation of the boundary layer on both sides and smaller wake in the back of the ball and a lower net drag due to pressure differential between the front and the back – this enables the golf ball to travel farther.


title: Fast bowling

text: The discovery of reverse swing is credited to Pakistan's cricketers, with Sarfraz Nawaz and Farrukh Ahmed Khan, both named as originators of the delivery.


title: Fast bowling

text: Now, in one-day cricket the mandatory two new balls rule (which states that two new balls must be used at the start of each innings; one from each end) means that the chances of reverse swing are reduced drastically. With two new balls being used, the amount of wear that each ball is subject to is half as compared to usual.


title: Fast bowling

text: A dipper is a swinging ball deliberately bowled as a yorker or a full toss, the latter not normally being a ball that a fast bowler would choose to bowl. The indipper moves in to the right-handed batsman while the outdipper moves away.


title: Fast bowling

text: To be effective, a dipper has to generate a lot of swing to make up for the variation in movement lost because the ball is not bouncing on the pitch. However, because the batsman usually expects a full toss to be an easy ball to score off, dippers have huge surprise value and can be extremely difficult to play especially if the bowler is very accurate and manages the yorker rather than a genuine full toss. Chaminda Vaas' bowling to Yuvraj Singh in the 2007–08 Commonwealth Bank Series is a classic example.


title: Fast bowling

text: Intimidatory or aggressive bowling is a legitimate tactic of bowling with the intent of hitting the batsman with the ball. This is somewhat restrained by some of the laws of cricket, including those that disallow excessive use of bouncers and any use of the "beamer", which is aimed directly at the head on the full. Successful intimidatory bowling usually employs a mixture of bouncers and short-pitched deliveries aimed at the batsman's head, chest, and rib cage. The intention is to disrupt a batsman's focus, and ultimately induce a mistake that leads to the loss of the batsman's wicket. Often the eventual wicket doesn't fall to a bouncer or short-pitched ball, but instead to a more standard delivery that the batsman is no longer expecting, or is rendered temporarily unable to play in his usual way (by fear, pain, surprise, or some combination of the three).


title: Fast bowling

text: One classic approach is to deliver several short balls into the batsman's chest, forcing the batsman onto the back foot to defend with a high bat, and then fire in a fast yorker, aimed at the base of the stumps. If the batsman is expecting to play a high back foot defensive, the time it takes to shift their weight to play the ball at their feet may just be enough for the delivery to surprise the batsman and cause him or her to panic, and thus cause the loss of their wicket.


title: Fast bowling

text: A fast bowler can also employ intimidatory tactics to anger (or frustrate) a batsman into playing a rash shot, by directing the ball to strike the batsman. Intimidatory bowling plays a part in every fast bowler's attack to some degree, and even the best batsmen sometimes sustain serious injuries that can force them off the field and out of the game. In almost all instances verbal 'sledging' accompanies the attack.


title: Fast bowling

text: Excessive use of intimidatory tactics by elite fast bowlers is considered unsportsmanlike, and is shunned by many teams and players. One instance of excessive use was the Bodyline series, where the English Cricket Captain at the time (1932–1933), Douglas Jardine, employed a tactic to restrain the skills of the Australian cricket team, and their star player, Donald Bradman. The tactic was to bowl, very fast and very short, at the batsman's body. After the Bodyline series, as it became known, several laws of cricket were altered to prevent such a tactic being used again, such as a restriction on the number of fielders that can occupy the rear leg-side quadrant of the cricket to two (excluding the wicketkeeper).


title: Fast bowling

text: Because nearly all cricket teams contain several fast bowlers of differing speeds and styles, the tactics of fast bowling depends not only on changing the field placements but on changing the bowler and the types and sequences of deliveries bowled as well. The precise tactics are determined by many factors including the state of the game, the state of the pitch, the weather and the relative energy and skill levels of the various players available to bowl.


title: Fast bowling

text: Fast bowling requires a great deal of energy and most fast bowlers can be expected to bowl a spell of 4–6 overs in a row before requiring a rest. Depending on conditions, they may be required by the team to bowl a longer spell although this usually results in drop in effectiveness toward the end of the spell as the bowler tires. Choosing which balls to bowl as part of a spell and what order to bowl them in is a tactical discipline all of its own.


title: Fast bowling

text: Most sides contain a mixture of fast bowlers who specialise in aggressive or seam techniques and those who specialise in swing. When the ball is new it usually swings very little, but generates a lot of speed, bounce and variation off the seam (because the seam on a new ball stands out more than that on an old ball). So, seam bowlers are usually chosen to bowl with the new ball either at the start of an innings or when a new ball has been taken, an option the fielding side has once a ball is 80 overs old. In contrast, swing bowlers are more effective once the ball has started to wear and reverse swing requires a well worn ball. Reverse swing bowlers can continue to extract large amounts of movement from balls well over 80 overs old.Then again according to conditions the new ball can swing too.


title: Fast bowling

text: Two seam bowlers are usually expected to bowl in tandem for the first 10 or so overs, after which time the ball may begin to swing and one or both of them are substituted for a swing bowler or a spin bowler. This is why most sides opt to include at least two seam bowlers who are known as "opening bowlers". Seam bowling usually becomes very ineffective with older balls and is virtually useless after 60 overs or so and as a result the bowling places in the side are filled with swing or spin bowlers.


title: Fast bowling

text: Fielding for a fast bowler is usually aggressive, that is to say that it is set up for the purpose of getting a wicket rather than preventing the flow of runs. On occasion, particularly when the fielding team is batting last and is chasing a total, a defensive field is required. As a general rule it is difficult to bowl defensive fast bowling – that task is better suited to spin bowlers.


title: Fast bowling

text: The various techniques of fast bowling lend themselves to three ways of getting the batsman out. They may be bowled or caught LBW either by speed, the yorker or by seam or swing causing the ball to move in toward them, in which case placement of fielders is irrelevant. Swing or seam may be employed to move the ball away from the batsman in which case the ball strikes the outside edge of the bat and may be caught in the slips. A badly-played bouncer will either fly off the outside edge as above or may result in a mistimed shot that can be caught near the boundary.


title: Fast bowling

text: It follows that the most effective field placements for aggressive fast bowling are to pack the outfield and the slips cordon and gully since these are the positions in which the batsman is most likely to be caught. Placing fielders in the outfield has the additional benefit of limiting the number of places where a batsman can score a boundary. Other close fielding positions such as silly mid on/off and the various midwicket and cover positions are generally redundant.


title: Fast bowling

text: In contrast, a defensive field for fast bowling packs the positions—such as gully, point, and cover—in a full circle round the batsman. One or two slips and one or two outfielders remain in case of a catch. Because batsmen usually try and play shots down on to the ground rather than risking being caught this field can stop most boundaries while remaining close enough to the pitch to attempt to run out the batsmen if they attempt a single. Defensive fast bowling is difficult because a skilled batsman set this type of field simply trusts in technique and scores from boundaries that they hit over the midwicket ring and away from any outfielders present.


title: Fast bowling

text: The primary goal of any bowler is to take the wicket of the batsman. The secondary goal is to prevent the batsman scoring runs. The latter is often a route to the former as a batsman deprived of runs often becomes frustrated and more likely to attempt risky shots to score. In addition, stopping the batsman from scoring keeps the same batsman at the crease to face consecutive balls, which can form a tactical sequence.


title: Fast bowling

text: Counter-intuitively, the best approach for a fast bowler is not to bowl constantly at the wicket as such predictability allows the batsman to simply defend his or her wicket and pick off the occasional bad ball. A far more effective approach is to introduce variation of line and length, leaving the batsman unsure as to whether to attack, defend or leave. The majority of balls in a well-bowled spell are usually swinging or seaming balls that pass at waist height, just outside the off stump and move away from the batsman because this is the area where it is most difficult for the batsman to choose the most appropriate response. Common variations and their tactical application are discussed below.


title: Fast bowling

text: The precise balls the bowler chooses during an over depend on the situation of the match, skill of the batsman, and how settled the batsman is at the crease. It is common to attack batsmen who have recently come to the wicket with successive short-pitched balls or bouncers with the dual aim of getting them out and stopping them from settling into an attacking mode of play for as long as possible. Short balls are more risky against batsmen who have settled at the crease since they make easy boundaries, but most bowlers still mix a few in during a spell, just to keep the batsman guessing.


title: Fast bowling

text: Most batsmen prefer to play shots off either the front or back foot and this influences the bowlers' choice of balls. It is difficult to play short balls off the front foot so bowlers bowl more short balls at batsmen who prefer the front foot. Likewise, it is hard to play yorkers and full pitched balls off the back foot so those are the deliveries of choice against back foot players. If a bowler can successfully get a batsman playing off his or her less-favoured foot with a sequence of appropriately pitched balls he can then gain an element of surprise by suddenly throwing down the "opposite" kind of ball – a yorker after a succession of short balls or a bouncer after a succession of full balls. An unobservant or complacent batsman can easily be caught unawares and lose their wicket.


title: Fast bowling

text: Another variation, especially against batsmen who have settled at the wicket and are starting to score more freely, is to switch the line of attack from the area just outside the off stump to bowling directly at leg stump. The batsman has to react to these balls as he otherwise runs a high risk of being bowled or trapped LBW but as he or she does so his or her bat moves over to the leg side, leaving the off side vulnerable. If the bowler can induce enough movement to the off side with swing or seam techniques, it often catches the outside edge of the bat, offering a catch or strike the stumps directly.


title: Fast bowling

text: Surprise is a big element in bowling, and bowlers often shun common tactical approaches in the hope of simply confusing the batsman into playing the wrong shot. For example, bowling a yorker at a new batsman who likely expects bouncers or at least standard line and length balls has made many batsmen lose their wicket first ball.


title: Fast bowling

text: In most cricketing countries, fast bowlers are considered to be the mainstay of a team's bowling attack, with slower bowlers in support roles. On the Indian subcontinent, Bangladesh and Sri Lanka, the reverse is often true, with fast bowlers serving mainly to soften the ball up for the spinners. This is largely due to the condition of the pitches used in those countries, which gives more help to spinners than to fast bowlers, but at international level it also reflects the skills of their spinners compared to their pace bowlers.


title: Fast bowling

text: Fast bowlers typically experience the highest incidence of injury of all player roles in cricket. The largest time-loss injuries are typically associated with overuse at the site of the lumbar spine. Common injuries include spondylolisthesis (stress fracture of the lower back), navicular stress fractures in the foot, SLAP tears or lesions, side strains or intercostal strains and muscular strains of the calves, hamstrings or spinal erectors. Popular media and commentators are often critical of the number of injuries suffered by fast bowlers. However, as of 2019, injury rates are at their lowest in decades, in many parts thanks to advances in physical conditioning, sport science, and load management interventions.


title: Fast bowling

text: Held by the Australian television station Channel 9 in a year in which the winner, Jeff Thomson, was banned from playing professional cricket due to punching a soccer umpire, Thomson had his maximum speed measured at 147.9 km/h using the same method as employed during a 1975 study at the WACA, where he was recorded bowling at 160.45 km/h using accurate, high-speed photo-sonic cameras. A follow-up study in 1976 put him at 160.6 km/h—he was the fastest of those tested in both studies. He also came top for accuracy in the competition. Four decades on, Thomson mentioned in an episode of "Cricket Legends" that he had intentionally (and wisely) bowled full tosses for the competition in order to improve his score. There was a $5,000 cash prize for the fastest bowler, and there was an additional $5,000 for the most accurate bowler (three points for the middle stump, and one point for either leg stump or off stump); Thomson scooped the entire A$10,000 prize pool (approximately A$50,000 in 2022 terms).


title: Fast bowling

text: Thomson recalled:If you bowl a bouncer, it's gonna come off slower anyway. So I'm thinking this is gonna be takin', you know, candy from a baby. And I've put my beer down, I come out, and I bowled a few balls—and I was bowling full tosses and that, because I knew they'd be quick. So I won the 5 grand, I hit the stumps three times out of six or whatever [in fact, the bowlers had 8 deliveries in total], and I've cleaned up. And I've come back out, and Kerry said: "How did you go?". I said, "I won, boss"; he said, "good".Final standings after 8 balls (in km/h):


title: Android 18

text: She and her twin brother, Android 17, were forcibly turned into cyborgs by Dr. Gero to serve his vendetta against Goku. The main-timeline version of the character has very little to no interest in fulfilling Gero's orders and becomes a major character in the series after marrying Goku's best friend Krillin.


title: Android 18

text: In an alternate future timeline, Android 18 is a ruthless killer who started a reign of terror along with Android 17 over Earth that lasted for twenty years until they are both killed by adult Trunks.


title: Android 18

text: Android 18, along with Android 17, were conceived after Akira Toriyama's former editor Kazuhiko Torishima expressed disapproval with Androids #19 and #20 as villains. Following their introduction into the series, Torishima soon afterward became dissatisfied with her and 17 as well, resulting in the creation of Cell. Toriyama stated that he was pleased with Android 18 because she was a type of girl he had not drawn before, and that he liked her slanted eyes. In 2014, he revealed her real name was .


title: Android 18

text: Yūsuke Watanabe, who wrote the screenplay for the film "", had originally written the film to take place at Android 18 and Krillin's wedding, but Akira Toriyama wrote it to take place at Bulma's birthday party. Watanabe thought Toriyama made the change because he wanted fans to imagine the wedding for themselves. In promotional material for "Battle of Gods", Toriyama drew her with purple hair.


title: Android 18

text: In the Japanese version of the entire "Dragon Ball" anime series and subsequent related media, Android 18 is voiced by Miki Itō.


title: Android 18

text: In English, Android 18 is voiced by Meredith McCoy in the Funimation dub of "Dragon Ball Z" and "Dragon Ball GT" except for "Dragon Ball Z Kai", where she is voiced by Colleen Clinkenbeard. However, since "," Meredith has returned to the role. In Bang Zoom! dub, Android 18 is voiced by Tamara Ryan.


title: Android 18

text: Despite being labeled an "Android", she is still Human and completely organic, so instead she was genetically altered given superhuman abilities in the process, and can still grow in skills and power through training like the superhumans.


title: Android 18

text: With her genetic enhancements she has super strength, speed, agility, reflexes, the ability to fly with telepathy, telekinesis, generate energy from her very being, produce energy blasts, absorb energy blasts, absorb energy, create force fields.


title: Android 18

text: Prior to their introductions and present in both timelines, Androids 17 and 18 were converted into androids by Dr. Gero with the intent of murdering Goku. In the main timeline, Android 18 is activated by Dr. Gero along with Android 17 after he returns to his laboratory following his unsuccessful attempt to defeat Goku's allies. After Gero is killed by Android 17, Android 18 activates Android 16 following surviving a blast meant to kill her from Trunks and the three begin their quest to find and kill Goku. When they encounter Vegeta, Android 18 decides to fight him and easily bests him in battle, receiving only damages to her clothing and breaking his arm. When Trunks, Tenshinhan and Piccolo become involved, she and Android 17 easily defeat the trio. Before leaving to continue her quest, she kisses Krillin on the cheek. The androids go to Goku's home and do not discover him there, leading them to journey to Kame-Sennin's house, but they do not find him there either due to his having departed not long before. 18 watches Android 17's battle against Piccolo, at one point becoming impatient and offering her assistance to her brother's decline, until Cell arrives, who reveals his intent to absorb the pair. Piccolo is dispatched by Cell and Android 17 is absorbed, Android 18 nearly being convinced to be absorbed as well by Cell's impersonation of Android 17 until he mistakenly mischaracterizes him. Androids 18 and 16 are given time to escape thanks to Tenshinhan holding Cell back. She and Android 16 hide on an island after this, where she refuses to leave his side and watches Vegeta's fight against Cell before Krillin approaches her with a remote to turn her off. He destroys it, realizing his love for her, and Android 18 is soon afterwards absorbed by Cell who blinds everyone with , allowing him to reach his final form. For the next ten days, until the Cell Games tournament that Cell sets up following his disillusion with the strength of both Vegeta and Trunks, 18 remains trapped and unconscious inside of his body. However, a strong blow from Gohan causes him to regurgitate her. After Gohan defeats Cell, she is healed and declines Krillin's advances for the time-being, despite him using the Dragon Balls to have her self-destruct device removed.


title: Android 18

text: In the timeline that Future Trunks comes from, 17 and 18 are mass murderers whereas the main timeline versions of the pair never killed innocents. They are identical in appearance to the versions of the two in the present timeline, Android 18 wearing the ensemble she wore in the main timeline upon her activation by Dr. Gero. Within the months of their release, shortly after the death of Goku, they kill their timeline's versions of Piccolo, Vegeta, Krillin, Yamcha, Tien and Yajirobe, Gohan managing to escape. Several years later, they kill Gohan and then nearly kill Trunks three years later when he confronts the pair during one of their killing sprees. When Trunks returns from the past, now vastly stronger than he was in their previous encounter as a result of his training, she shows interest in finally ending his life after he confronts her and Android 17, but is killed by him instead.


title: Android 18

text: Seven years later in the main timeline, she has married Krillin and has a daughter with him named . She convinces Krillin to participate in the 25th Tenka'ichi Budōkai for the money along with her. Thanks to a lack of interest in being exposed as super-powered, she disguises her strength in hitting the Punching Machine, hitting it lightly and thereby altering who she is matched to fight. During the competition, she competes against Goten and Trunks when the pair enter the competition as , having stolen the identity of another competitor. After the duo reveal themselves by transforming into Super Saiyans, Android 18 wins the match by default, advancing to the next round against Mr. Satan, who she outclasses in strength, but throws the fight nonetheless after she secretly arranged to have the prize money shared with him so as not to ruin his reputation. After Majin Boo is released, thanks to the energy used by both Goku and Vegeta while the two fought, Android 18 joins the others in searching for the Dragon Balls to resurrect everyone killed by Vegeta and resides at Dende's while taking refuge. After Boo finds them the following day, kills the majority of people on Earth and escapes the Room of Spirit and Time, leaving Gotenks and Piccolo inside, Android 18 is killed alongside her daughter when they are simultaneously turned into chocolate, being eaten by him afterward. She is later brought back to life and gives energy to Goku's "Genki-dama", successfully destroying Majin Boo. Ten years later, 18 is last seen attending another Tenkaichi Budōkai.


title: Android 18

text: in the film "", Android 18 is present at Bulma's birthday party, attempting to fight Beerus following him being enraged by Boo taking his pudding, but being defeated with a single strike to the neck; in "", she shaves Krillin's head before he goes off to fight a resurrected Freeza, being killed after Freeza destroys the planet but having her death undone when the timeline is reversed. After the events of the last two films, she informs Krillin of a supposed space picnic, leading to his investigation into the matter and she later travels off Earth to watch the tournament between the fighters from her universe and those of Universe 6. After Trunks returns from the future, he discovers Android 18 and Krillin's marriage, meeting 18 again and preparing to engage her before she greets him. Android 18 later wants to get a gift for Krillin and unsuccessfully tries using the Dragon Balls. Android 18 scolds Krillin for being injured by a bullet while he is reluctant to train with Goku, later citing her as a factor in his choice to resume training.


title: Android 18

text: Android 18 and Krillin are approached by Goku and Gohan to join the Tournament of Power, 18 agreeing due to the 10 million Zeni reward and revealing Android 17's location. During the tournament Android 18 chooses to fight on her own, defeating Universe 9's Sorrel, Universe 4's Shosa, and Universe 11's Tupper. Rozie and Ribrianne launch a combined attack at Goku that Androids 17 and 18 deflect, the two then battling Rozie and Ribrianne. Android 18 knocks Ribrianne out of her transformation and she reverts to Brianne, who catches Android 18 in an energy trap while her comrades from Universe 2 send their love to her and enable her transforming back into Ribrianne but with an increase in size. Android 18 concedes that she is finished before hearing Krillin screaming her name from the sidelines and breaking through Ribrianne's trap. With assistance from Android 17, 18 blasts through Ribrianne's giant form and eliminates her. Universe 3's Paparoni and Koichiarator merge to form Anilaza and Goku, Gohan, Vegeta, Frieza, 17, and 18 attempt coordinating their attacks against the being. Anilaza attempts to eat 18 before Goku intervenes, and Anilaza corners Android 17 with a series of beams that lead him off the ledge of the arena. Android 18 jumps off and grabs him, telling him that the rest is up to him before kicking him back to the arena while descending to her own elimination. She apologizes to Universe 7 for being eliminated and tells Android 17 he better not lose.


title: Android 18

text: Shortly after the Tournament of Power, 18, along with 17, help the Z fighters fight off henchmen that Moro has sent to Earth.


title: Android 18

text: Android 18 appears in "" alongside Krillin, to assist Gohan and company in countering the resurrected Red Ribbon Army.


title: Android 18

text: Android 18 appears in two non-canonical "Dragon Ball Z" films; she briefly appears at the beginning of the ; In the , Android 18 tries to retrieve money from Mr. Satan that he owed her from their deal that she would lose the tournament so she would not publicly upstage him, later fighting against Bio-Broly along with Krillin, Goten and Trunks and saves civilians from being killed by him.


title: Android 18

text: In a filler episode of "Dragon Ball Z", Android 18 attends a party with her family. Android 18 is featured in the special "", being saved by Krillin from having a building collapse on both her and her daughter after it was hit by Aka's .


title: Android 18

text: In the anime-only sequel, "Dragon Ball GT", Android 18 falls under Baby's control when the latter takes over Earth, avoiding being killed by Baby despite being caught in a blast from his "Super Galick Gun". She is freed of his control with the use of the Sacred Water, though has to abandon Earth the following year to avoid the planet's explosion thanks to a wish he made with the unstable Black Star Dragon Balls. Later she is nearly possessed by Android 17 to merge with him, but is helped out of his control by Krillin, who is then killed. Android 18 tries to fight him, but is defeated and left for dead. Android 18 comes to Goku's aid when he is fighting Super 17, the combination of Android 17 and Hell Fighter 17, a clone of her brother, in retaliation to Krillin's death which Goku was unaware of until she mentioned it. It is through her intervention that Goku is able to defeat him as she goads Super 17 to finish them both off and in doing so causes him to undergo an internal struggle that Goku exploits by attacking him while he is distracted by 18. After being assured that Krillin would be resurrected with the Dragon Balls, Android 18 is last seen at Capsule Corporation.


title: Android 18

text: Android 18 has made several appearances in music. Her voice actress Meredith McCoy recorded vocals for a theme song by Bruce Faulconer for Android 18, the track being named after her. The American soundtrack also had a 2003 release titled "Dragonball Z American Soundtrack Best of Dragonball Z: Android 18", dedicated to the character. The band Seraphim has a song titled "Android 18", describing her mixture of human and machine. Android 18 is also referenced in the song "Blessing" by Chance the Rapper when the lyricist raps that he laughs when Krillin mentions blonde hair.


title: Android 18

text: Android 18 also made a guest appearance in an episode of the hit YouTube show "Death Battle". In the episode, her weapons, skills and abilities were analyzed against the "Marvel Comics" hero "Captain Marvel (Carol Danvers)". In the end, Android 18 proved herself the better fighter and beat her opponent.


title: Android 18

text: She is one of the main villains in the video series "Dragon Ball Z: Light of Hope", portrayed by Amy Johnston.


title: Android 18

text: Her first appearance in a "Dragon Ball" game was "". She is a playable character in most "Dragon Ball Z" fighting games, including the "Budokai" series and "Raging Blast" series. Android 18 is the only playable android in both "" and "", having an original story in "Shin Budokai" where she defeats Freeza, who intended to kidnap her so she could assist him in his acquiring of the Dragon Balls on Namek and has her programming to terminate Goku erased after summoning Shenlong. In the 2010 arcade game "Dragon Ball Heroes", after Super 17 is defeated by Android 18, Gohan, Vegeta and Goku, she is forcefully merged with her brother by Towa to power him up against the three Saiyans. In addition to her role as a playable character, she has also served as a boss in other games.


title: Android 18

text: In the 2015 game "Dragon Ball Xenoverse", Androids 17 and 18 experience an increase in power from Demigra and attack Trunks in the alternate timeline, the possible fatality of Trunks through their encounter causing him to start disappearing. The player travels to Trunk's timeline and helps him fight 17 and 18, the latter being the first to notice. The combined force of Trunks and the player cause 17 and 18 to flee, and are later absorbed by Cell. Android 18 can be a mentor to the player character and teach "Power Blitz", "Endless Shoot", "Deadly Dance" and "Dual Destructo-Disc" She explains her motives for helping out are only due to having agreed to pay her in exchange for training the player.


title: Android 18

text: In the 2016 game "Dragon Ball Xenoverse 2", Android 17 charges Cell after his Villainous Mode allows him to defeat Piccolo and Android 16, causing him to fall back into Android 18 and knock both of them out, allowing Cell to absorb both. In downloadable content, Android 18 assist Dabura in his fight against Krillin and the player after Dabura admits that he cannot fight the two by himself. Android 18 says that she is surprised to see Krillin there as she had ordered him to look after Marron, leading Krillin to state his intent to leave the battle before realizing that he had said the same thing to 18, and Android 18 reveals that she purposely said that to trick him. As the pair fight, Android 18 admits that her personal feelings for Krillin are going to make it harder for her to fight him, and states that she will protect the Krillin and Marron of her timeline no matter the costs.


title: Android 18

text: In the 2018 game "Dragon Ball FighterZ", Krillin and Goku come across Android 21 and an unconscious Android 18 as Cell hovers over them preparing to attack. Android 21 pleads for Cell to spare 18, and Goku decides to fight Cell while Krillin checks on 18. While Krillin tends to her, Android 21 explains that 18 stood up for her against Cell. In another story, 18 begins having a headache she believes is brought on by Krillin being in trouble when she is encountered by Android 16, passing out shortly thereafter. She wakes up in a laboratory with Androids 16 and 21 hoovering over her, Android 16 revealing that the player is now in control of 18's body while the latter's actual soul is internally deep inside. The player makes contact with 18's soul, who admits trying to force the player out and recounts the story before requesting the player interact with 16 and 21 to find out what's happened. Android 21 admits her culpability in linking the player and 18 together for the purpose of defeating the Red Ribbon Army's clone fighters, and Android 16 stipulates that the two will return to their normal selves following all of the clones being disposed of. During the matches, Android 21 has repeated instances of losing her composure as she breaks down, culminating in her ordering 18 to fight Krillin when he stumbles across the group. After the group defeats Cell and Android 21 tries to kill him, Android 18 makes an unsuccessful attempt at linking with her to stop the murder. After 21 splits with her evil half, the evil half kills Android 16 and merges with Cell, Android 18 travels off planet to participate in the fight against 21's evil half. Goku fires a Spirit Bomb at the evil half, and Android 21 requests Android 18 look after the player before the player returns to Android 18 and 21 sacrifices herself to kill her evil half.


title: Android 18

text: Android 18 is a generally well-liked character, praised for her status as the sole female character to physically compete with the male cast for a time as well as her personality. In a 2004 poll among Japanese fans, Android 18 was voted the tenth most popular character in the series. Her relationship with Krillin has also been met with favorability among commentators. Sheldon Pearce of "Complex" dubbed her the "most compelling" of the androids and credited her with keeping Krillin a relevant character after her introduction. David F. Smith of "IGN" believed the subplot of the relationship between Android 18 and Krillin helped to keep the Cell arc "a little more interesting". Smith ranked the development of the relationship #6 on his list "Dragon Ball Z: Top 10 Plot Twists". However, Android 18's role in the franchise past the Cell storyline has been met with mixed reception. Android 18 was ranked #4 on Santiago Rashad's list "Top Ten Misused Dragon Ball Characters" who felt that she was underused barring two later films, "Bio-Broly" and "Battle of Gods", and that she was possibly used less due to not being a Saiyan. Aaron Hubbard of Moviepilot observed her shift from fighter to mother and wife as "unjust" given that she had been a threat to the protagonists in her first appearances, though still thought highly of the character. Chris Homer of "The Fandom Post" felt Android 18's "getting in the spotlight" was one of the decent moments in the Super 17 storyline.


title: Android 18

text: Android 18 is a popular subject for cosplay activities by "Dragon Ball" fandom. Japanese mixed martial artist Itsuki Hirata is nicknamed "Android 18" due to her alleged resemblance to the character, and has cosplayed as the character on at least one occasion. She was the visual inspiration for the "Fatal Fury" and "The King of Fighters" character Blue Mary. American mixed martial artist Ronda Rousey revealed in 2015 that she wanted to be Android 18 when she was a child.


title: William Lindsay Gresham

text: William Lindsay Gresham (; August 20, 1909 – September 14, 1962) was an American novelist and non-fiction author particularly well-regarded among readers of noir. His best-known work is "Nightmare Alley" (1946), which was adapted to film in 1947 and 2021.


title: William Lindsay Gresham

text: Gresham was born in Baltimore, Maryland. As a child, he moved with his family to New York, where he became fascinated by the sideshow at Coney Island. Upon graduating from Erasmus Hall High School in Brooklyn in 1926, Gresham drifted from job to job, and worked as a folk singer in Greenwich Village.


title: William Lindsay Gresham

text: His parents divorced when he was 16. His own first marriage also ended in divorce, as well as his second to a New Jersey socialite which fell apart after nine years when he returned to America, embittered by his experiences in Spain. In 1937, Gresham had served as a volunteer medic for the Abraham Lincoln Brigade forces during the Spanish Civil War. There, he befriended a former sideshow employee, Joseph Daniel "Doc" Halliday, and their long conversations inspired much of his work, particularly Gresham's two books about the American carnival, the nonfiction "Monster Midway" and the fictional "Nightmare Alley".


title: William Lindsay Gresham

text: Returning to the United States in 1939, after a troubling period that involved a stay in a tuberculosis ward and a suicide attempt, Gresham found work editing true crime magazines. In 1942, Gresham married Joy Davidman, a poet, with whom he had two children, David and Douglas.


title: William Lindsay Gresham

text: In 1946 he published "Nightmare Alley", his first and most successful novel. It was purchased by Hollywood for $60,000 and made into a film of the same name in 1947 starring Tyrone Power. Gresham and Davidman moved into a sprawling fourteen-room house in Staatsburg, New York.


title: William Lindsay Gresham

text: Gresham was an unfaithful and alcoholic husband. Davidman, an ethnically Jewish atheist, became a fan of the writings of C. S. Lewis, which led eventually to her conversion to Christianity. Within a year or so Gresham was calling himself a Christian, which influenced his second and last novel, Limbo Tower. However, the couple struggled financially and Gresham would have tax problems for many years to come. Davidman complained to friends of his frequent drinking, serial infidelity, and even occasional eruptions of violence. At this time Gresham also became interested in Dianetics, the 1950 self-help book by science fiction writer L. Ron Hubbard. Although an early enthusiast of Scientology, he later denounced it as another kind of spook racket.


title: William Lindsay Gresham

text: Suffering from an illness, Davidman decided to go to England in 1952 to seek out C.S. Lewis, with whom she'd been corresponding. She invited her cousin, Renée Rodriguez—who was fleeing an abusive husband with her two small children—to keep house for her family in her absence. Gresham and Rodriguez soon began an affair.


title: William Lindsay Gresham

text: Gresham wrote to Davidman in January 1953 saying that he and Rodriguez had become lovers and Davidman returned to New York, enduring an awkward period where all three of them were living under the same roof because none could afford to go anywhere else.


title: William Lindsay Gresham

text: Davidman sold the house to pay off the Internal Revenue Service and moved to England with the boys. Later she married Lewis, their relationship forming the inspiration for the play and movie "Shadowlands".


title: William Lindsay Gresham

text: Gresham married Rodriguez as soon as the divorce was finalized. After Davidman's untimely death, Gresham visited England to see his sons. When it became apparent that they were well cared for, he left them with Lewis.


title: William Lindsay Gresham

text: Gresham joined Alcoholics Anonymous and developed a deep interest in Spiritualism, having already exposed many of the fraudulent techniques of popular spiritualists in his two sideshow-themed books and having written a book about Houdini with the assistance of noted skeptic James Randi. Twenty-four of his articles and stories on fairgrounds, spookshows and hucksters were republished in 2013 as "Grindshow: the Selected Writings of William Lindsay Gresham".


title: William Lindsay Gresham

text: In 1962, Gresham's health began to take a turn for the worse. He had started to go blind and was diagnosed with tongue cancer. On September 14, 1962, he checked into the Dixie Hotel, Manhattan—which he had often frequented while writing "Nightmare Alley" over a decade earlier. There, 53-year-old Gresham took his life with an overdose of sleeping pills. His death went generally unnoticed by the New York press but for a mention by a bridge columnist. Business cards were found in his pocket, reading "No Address. No Phone. No Business. No Money. Retired."


title: Cohort (military unit)

text: A cohort (from the Latin "cohors", plural "cohortes", see wikt:cohors for full inflection table) was a standard tactical military unit of a Roman legion. Although the standard size changed with time and situation, it was generally composed of 480 soldiers. A cohort is considered to be the equivalent of a modern military battalion. The cohort replaced the "maniple" following the reforms attributed to Gaius Marius in 107 BC. Shortly after the military reforms of Marius, and until the middle of the third century AD, ten cohorts (about 5,000 men total) made up a legion. Cohorts were named "first cohort,” "second cohort," etc. The first cohort consisted of experienced legionaries, while the legionaries in the tenth cohort were less experienced.


title: Cohort (military unit)

text: A legionary cohort of the early empire consisted of six "centuriae", or centuries, each consisting of 80 legionaries, for a total of 480 legionaries. Prior to the Marian reforms, each "centuria" consisted of 100 men, hence their name. Each "centuria" was commanded by a centurion, who increased in seniority from the sixth to the first centuries; thus, the centurion of the sixth century was the most junior in the cohort, while the centurion of the first century was the most senior. In order of increasing seniority, the six centurions were titled "hastatus posterior", "hastatus prior", "princeps posterior", "princeps prior", "pilus posterior", and "pilus prior". The "pilus prior" would command the cohort overall. The nomenclature of the ranks was derived from the Republican "manipular" legions, where troops were grouped into three rankings; "hastati" for the most inexperienced, followed by "principes", and finally "triarii" for the most experienced. "Pilus" was a rare alternative name for "triarius", reflecting their use as spearmen, "pilus" being the Latin word for spear.


title: Cohort (military unit)

text: The Marian reforms established by Gaius Marius in the 1st century BC formalised the command structure and composition of the legions. A century of 80 men was divided into ten "contubernia", each of eight men, who shared a single A-frame tent together. A contubernium was led by a decanus, appointed from within the contubernium, and was most likely the longest-serving legionary of the eight. The decanus organised the erection of the unit's marching tent, and ensured his tent-mates kept things tidy. A contubernium was assigned one to two pack mules, which would carry heavier equipment and the contubernium's mill, for grinding their daily grain ration into flour. These duties would be carried out by camp slaves, of which one to two would be assigned to each contubernium. They tended to the pack mule, ensured legionaries had water on the march, and camp duties such as cooking, washing, and other specialised skills such as smithing or carpentry. While encamped, younger legionaries may be sent out to fetch fodder, firewood, and water for the contubernium.


title: Cohort (military unit)

text: A century of 80 men would be commanded by a centurion, assisted by four junior officers. The pay of a centurion fluctuated depending on their seniority; the most junior centurion in a legion received around ten times the standard rate of pay, while the most senior legionary centurion could receive some forty times the standard rate of pay. The centurion was assisted by an optio, who served as his second-in-command, and typically received double the legionary rate of pay. Third in seniority was a tesserarius, who exercised command over the nightly guard duties, and were responsible for distributing the watchwords for the camp. A tesserarius was typically paid one-and-a-half times the standard rate of pay. A century also had a signifer, who carried the century's standard into battle, and also served as the unit's treasurer, keeping track of the pay and expenses of the men. Signifers typically received double pay. Lastly, a cornicen, equipped with a cornu, served as a signaller, and received double pay. These officers would have their own support staff, tents, and mules. Thus, a cohort would consist of, on paper, 480 legionaries, 6 centurions, and 24 junior officers, with logistical support provided by 60-120 slaves, and 60-120 mules.


title: Cohort (military unit)

text: Ten cohorts of 480 legionaries would comprise a legion. Like the ranks of the centurions, cohorts would also follow a pattern of seniority; a legion's tenth cohort was its most junior, while the first cohort was the most prestigious, with its ranks filled with either veteran troops, or the best recruits. The commander of the first cohort's first century was known as the "primus pilus" or "first spear", a legion's most senior centurion. The "primus pilus" was eligible for promotion to "praefectus castrorum" or camp prefect, the third most senior officer in a legion, responsible for the day-to-day administration of a legion.


title: Cohort (military unit)

text: The first cohort was an aberration in that it consisted of five double-strength "centuriae", each of 160 men, for a total of 800 men, as opposed to six centuries of 80 men. It was the unique honour of the first cohort's aquilifer to carry the legion's "aquila", or eagle, standard into battle, which possessed a quasi-religious importance to the legionaries. Loss of an eagle was considered a mark of extreme shame and disgrace for a legion. A legion's first cohort also had an imaginifer, who carried an "imago" of the reigning Emperor, typically a three-dimensional relief of their likeness made of beaten metal.


title: Cohort (military unit)

text: Each cohort also had a small artillery corps. According to Vegetius, each century was equipped with a "scorpio", a small torsion-powered ballista, for a total of six per cohort. A contubernium would be deputed to operate the weapon, when required. Like most ancient artillery, these weapons were likely used in fixed positions for infantry defence, or in sieges. Each cohort also had one "onager", a stone-throwing torsion-powered catapult. Vegetius stipulates that they were transported fully-assembled on ox-drawn carts, to ensure the onager was ready for immediate use. Additional equipment, such as rams, towers, or larger ballistae were added as needed. Thus, by extrapolation, a legion had an artillery train of some sixty "scorpios" and ten "onagers".


title: Cohort (military unit)

text: Furthermore, the Latin word "cohors" was used in a looser way to describe a rather large "company" of people (see, for instance, "cohors amicorum").


title: Volleyball at the Summer Olympics

text: Volleyball has been part of the Summer Olympics program for both men and women consistently since 1964.


title: Volleyball at the Summer Olympics

text: Brazil, the United States and the former Soviet Union are the only teams to win multiple gold medals at the men's tournament since its introduction. The remaining six editions of the Men's Olympic Volleyball Tournament were won each by a different country including Japan, Poland, Netherlands, Russia, France, and the defunct Yugoslavia.


title: Volleyball at the Summer Olympics

text: Gold medals are less evenly distributed in women's volleyball than in men's; the fifteen editions of the Women's Olympic Volleyball Tournament were won by only six countries: Brazil, Cuba, China, Japan, the United States and the former Soviet Union.


title: Volleyball at the Summer Olympics

text: The history of Olympic volleyball can be traced back to the 1924 Summer Olympics in Paris, where volleyball was played as part of an American sports demonstration event. Its addition to the Olympic program, however, was given only after World War II, with the foundation of the FIVB and of some of the continental confederations. In 1957, a special tournament was held during the 53rd IOC session in Sofia, Bulgaria, to support such request. The competition was a success, and the sport was officially introduced in 1964. The International Olympic Committee attempted to drop volleyball for the 1968 Olympics, but this was met with protest.


title: Volleyball at the Summer Olympics

text: The volleyball Olympic tournament was originally a simple competition, whose format paralleled the one still employed in the World Cup: all teams played against each other team and then were ranked by number of wins, set average and point average. One disadvantage of this round-robin system is that medal winners could be determined before the end of the games, making the audience lose interest in the outcome of the remaining matches.


title: Volleyball at the Summer Olympics

text: To cope with this situation, the competition was split into two phases: a "final round" was introduced, consisting of quarterfinals, semifinals and finals. Since its creation in 1972, this new system has become the standard for the volleyball Olympic tournament, and is usually referred to as the "Olympic format".


title: Volleyball at the Summer Olympics

text: The number of teams involved in the games has grown steadily since 1964. Since 1996, both men's and women's indoor events count 12 participant nations. Each of the five continental volleyball confederations has at least one affiliated national federation involved in the Olympic Games.


title: Volleyball at the Summer Olympics

text: The first two editions of the volleyball Olympic tournament were won by the Soviet Union team. Bronze in 1964 and silver in 1968, Japan won gold in 1972. In 1976, the introduction of a new offensive skill, the back row attack, helped Poland win the competition over the Soviets in a very tight five-setter.


title: Volleyball at the Summer Olympics

text: In 1980, many of the strongest teams in men's volleyball belonged to the Eastern Bloc, so the American-led boycott of the 1980 Summer Olympics did not have as great an effect on these events as it had on the women's. The Soviet Union collected their third Olympic gold medal with a 3–1 victory over Bulgaria. With a Soviet-led boycott in 1984, the United States confirmed their new volleyball leadership in the Western World by sweeping smoothly over Brazil at the finals. In that edition a minor nation, Italy, won their first medal, but Italy would rise to prominence in volleyball in later decades. A long-awaited confrontation between the US and Soviet volleyball teams came in the 1988 final: powerplayers Karch Kiraly and Steve Timmons pushed the United States to a second gold medal setting the issue in favor of the Americans.


title: Volleyball at the Summer Olympics

text: In 1992, Brazil upset favorites Unified Team, Netherlands, and Italy for their first Olympic championship. Runners-up Netherlands, with Ron Zwerver and Olof van der Meulen, came back in the following edition for a five-set win over Italy. In spite of their success in other major volleyball competitions in the 1990s, Italy did not fare well at the Olympics. After winning bronze in Atlanta, Serbia and Montenegro, led by Vladimir and Nikola Grbić, beat Russia at the final in 2000 to secure the gold (in 1996 and 2000 they played under the name Federal Republic of Yugoslavia).


title: Volleyball at the Summer Olympics

text: In 2004, Brazil beat Italy in the final, adding a second gold medal to their record and confirming their role as the men's volleyball superpowers of the 2000s. In 2008, United States beat Brazil in the final, winning their third gold medal. Russia won the bronze for the second time by defeating Italy. In the 2012 final, Russia came back from a 0–2 set deficit, not letting the Brazilians take advantage of any of their 2 match points in the third set. Dmitriy Muserskiy scored 31 points, which is an Olympic Games record in a final. Italy defeated Bulgaria and took Bronze.


title: Volleyball at the Summer Olympics

text: After coming up short in the previous two editions of the Olympics as runners-up, the Brazilians captured their third gold medal in the history of the competition playing home in 2016 after their straight-set victory against Italy in the final. The United States pulled off a comeback from a 0–2 deficit to claim the bronze medal with a victory over Russia.


title: Volleyball at the Summer Olympics

text: The 2020 tournament, held in 2021 due to the COVID-19 pandemic causing a delay, had the French team of Earvin N'Gapeth win it all over the Russians. In a repeat of the 1988 bronze medal match, Brazil were upset by neighbor Argentina.


title: Volleyball at the Summer Olympics

text: Gold medals appear to be more evenly distributed in men's volleyball than in women's: former Soviet Union (three titles), United States (three) and Brazil (three) are the only teams to have won the tournament more than once. The remaining six editions were won each by a different country. Despite being a major force in men's volleyball since the 1990s, and never missing a tournament since 1976 Italy are still the only volleyball powerhouses that lack a gold medal at the Olympic Games.


title: Volleyball at the Summer Olympics

text: The opening edition of the volleyball Olympic tournament, in 1964, was won by the host nation Japan. There followed two victories in a row by the Soviet Union, in 1968 and 1972. South Korea were expected to get their first gold after beating Japan in the 1975 Pre-Olympic Games, but Japan came back again in 1976 for one last Olympic gold before losing their status of women's volleyball superpowers.


title: Volleyball at the Summer Olympics

text: The American-led boycott of the 1980 Games left many strong volleyball nations like Japan and South Korea out of the games. As a result, the Soviet Union easily secured a third Olympic gold medal. In 1984, the Eastern bloc was, in its turn, boycotting the games, and the Soviet Union did not participate. As a result, host nation United States won its first medals in volleyball, losing the finals to China. With eastern and western nations again involved in the Olympics, the Soviet Union obtained a remarkable victory over Peru after trailing 0–2 in 1988's marking one of the most dramatic female matches of the 20th century. The 1988 games were, however, boycotted by Cuba, who would become the next dominating force.


title: Volleyball at the Summer Olympics

text: 1992 saw a new force go down in Olympic history: organized under the name Unified Team, the nations of the former Soviet Union that chose to form a combined team easily reached the gold medal game, but did not resist the power play of the young, rising Cuban squad. Led by superstars Mireya Luis and Regla Torres, Cuba would eventually set the record for consecutive wins in the Olympic Games by also taking the gold in 1996 and 2000 against China and Russia, respectively.


title: Volleyball at the Summer Olympics

text: In 2004, the winners were once again China. Second were Russia who beat Brazil in a very tough and dramatic semifinal match after being down 1–2, 19–24 in the fourth set.


title: Volleyball at the Summer Olympics

text: In 2008, Brazil finally won the gold, beating the United States in the final and losing only one set in the competition. China were awarded the bronze by beating Cuba. After a troubled start, Brazil secured the double gold in 2012 after beating the United States once again in the final. Japan won the bronze medal after defeating South Korea.


title: Volleyball at the Summer Olympics

text: In 2016, home team Brazil were favorites to once again win the title, thus equalling Cuba's three consecutive gold medals between 1992 and 2000. After winning all of their preliminary round matches without dropping a set, the team was, however, stunned by a young Chinese squad in a tiebreaker in the quarterfinals. China went on to win the title, their third in Olympic history, by beating Serbia in four sets in the gold medal match. In the process, Lang Ping became the first person to win a gold medal as a player in Los Angeles 1984 and repeat the feat now as a coach in Rio de Janeiro. China also became the first team to win the Olympics after losing three matches in the preliminary round. The United States defeated Netherlands 3–1 to capture the bronze medal.


title: Volleyball at the Summer Olympics

text: In the fifteenth edition of the games in 2020, the United States faced Brazil for the third final in four editions, only this time they broke the long title drought. Thus the Americans became only the sixth country to win the women's tournament, after Brazil, China, Cuba, Japan, and the former Soviet Union. Serbia got the bronze, beating South Korea.


title: Neural oscillation

text: Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.


title: Neural oscillation

text: Neural oscillations in humans were observed by researchers as early as 1924 (by Hans Berger). More than 50 years later, intrinsic oscillatory behavior was encountered in vertebrate neurons, but its functional role is still not fully understood. The possible roles of neural oscillations include feature binding, information transfer mechanisms and the generation of rhythmic motor output. Over the last decades more insight has been gained, especially with advances in brain imaging. A major area of research in neuroscience involves determining how oscillations are generated and what their roles are. Oscillatory activity in the brain is widely observed at different levels of organization and is thought to play a key role in processing neural information. Numerous experimental studies support a functional role of neural oscillations; a unified interpretation, however, is still lacking.


title: Neural oscillation

text: Richard Caton discovered electrical activity in the cerebral hemispheres of rabbits and monkeys and presented his findings in 1875. Adolf Beck published in 1890 his observations of spontaneous electrical activity of the brain of rabbits and dogs that included rhythmic oscillations altered by light detected with electrodes directly placed on the surface of the brain. Before Hans Berger, Vladimir Vladimirovich Pravdich-Neminsky published the first animal EEG and the evoked potential of a dog.


title: Neural oscillation

text: Neural oscillations are observed throughout the central nervous system at all levels, and include spike trains, local field potentials and large-scale oscillations which can be measured by electroencephalography (EEG). In general, oscillations can be characterized by their frequency, amplitude and phase. These signal properties can be extracted from neural recordings using time-frequency analysis. In large-scale oscillations, amplitude changes are considered to result from changes in synchronization within a neural ensemble, also referred to as local synchronization. In addition to local synchronization, oscillatory activity of distant neural structures (single neurons or neural ensembles) can synchronize. Neural oscillations and synchronization have been linked to many cognitive functions such as information transfer, perception, motor control and memory.


title: Neural oscillation

text: Neural oscillations have been most widely studied in neural activity generated by large groups of neurons. Large-scale activity can be measured by techniques such as EEG. In general, EEG signals have a broad spectral content similar to pink noise, but also reveal oscillatory activity in specific frequency bands. The first discovered and best-known frequency band is alpha activity (8–12 Hz) that can be detected from the occipital lobe during relaxed wakefulness and which increases when the eyes are closed. Other frequency bands are: delta (1–4 Hz), theta (4–8 Hz), beta (13–30 Hz), low gamma (30–70 Hz), and high gamma (70–150 Hz) frequency bands, where faster rhythms such as gamma activity have been linked to cognitive processing. Indeed, EEG signals change dramatically during sleep and show a transition from faster frequencies to increasingly slower frequencies such as alpha waves. In fact, different sleep stages are commonly characterized by their spectral content. Consequently, neural oscillations have been linked to cognitive states, such as awareness and consciousness.


title: Neural oscillation

text: Although neural oscillations in human brain activity are mostly investigated using EEG recordings, they are also observed using more invasive recording techniques such as single-unit recordings. Neurons can generate rhythmic patterns of action potentials or spikes. Some types of neurons have the tendency to fire at particular frequencies, so-called "resonators". Bursting is another form of rhythmic spiking. Spiking patterns are considered fundamental for information coding in the brain. Oscillatory activity can also be observed in the form of subthreshold membrane potential oscillations (i.e. in the absence of action potentials). If numerous neurons spike in synchrony, they can give rise to oscillations in local field potentials. Quantitative models can estimate the strength of neural oscillations in recorded data.


title: Neural oscillation

text: Neural oscillations are commonly studied from a mathematical framework and belong to the field of "neurodynamics", an area of research in the cognitive sciences that places a strong focus upon the dynamic character of neural activity in describing brain function. It considers the brain a dynamical system and uses differential equations to describe how neural activity evolves over time. In particular, it aims to relate dynamic patterns of brain activity to cognitive functions such as perception and memory. In very abstract form, neural oscillations can be analyzed analytically. When studied in a more physiologically realistic setting, oscillatory activity is generally studied using computer simulations of a computational model.


title: Neural oscillation

text: The functions of neural oscillations are wide-ranging and vary for different types of oscillatory activity. Examples are the generation of rhythmic activity such as a heartbeat and the neural binding of sensory features in perception, such as the shape and color of an object. Neural oscillations also play an important role in many neurological disorders, such as excessive synchronization during seizure activity in epilepsy or tremor in patients with Parkinson's disease. Oscillatory activity can also be used to control external devices such as a brain–computer interface.


title: Neural oscillation

text: Oscillatory activity is observed throughout the central nervous system at all levels of organization. Three different levels have been widely recognized: the micro-scale (activity of a single neuron), the meso-scale (activity of a local group of neurons) and the macro-scale (activity of different brain regions).


title: Neural oscillation

text: Neurons generate action potentials resulting from changes in the electric membrane potential. Neurons can generate multiple action potentials in sequence forming so-called spike trains. These spike trains are the basis for neural coding and information transfer in the brain. Spike trains can form all kinds of patterns, such as rhythmic spiking and bursting, and often display oscillatory activity. Oscillatory activity in single neurons can also be observed in sub-threshold fluctuations in membrane potential. These rhythmic changes in membrane potential do not reach the critical threshold and therefore do not result in an action potential. They can result from postsynaptic potentials from synchronous inputs or from intrinsic properties of neurons.


title: Neural oscillation

text: Neuronal spiking can be classified by their activity patterns. The excitability of neurons can be subdivided in Class I and II. Class I neurons can generate action potentials with arbitrarily low frequency depending on the input strength, whereas Class II neurons generate action potentials in a certain frequency band, which is relatively insensitive to changes in input strength. Class II neurons are also more prone to display sub-threshold oscillations in membrane potential.


title: Neural oscillation

text: A group of neurons can also generate oscillatory activity. Through synaptic interactions, the firing patterns of different neurons may become synchronized and the rhythmic changes in electric potential caused by their action potentials will add up (constructive interference). That is, synchronized firing patterns result in synchronized input into other cortical areas, which gives rise to large-amplitude oscillations of the local field potential. These large-scale oscillations can also be measured outside the scalp using electroencephalography (EEG) and magnetoencephalography (MEG). The electric potentials generated by single neurons are far too small to be picked up outside the scalp, and EEG or MEG activity always reflects the summation of the synchronous activity of thousands or millions of neurons that have similar spatial orientation. Neurons in a neural ensemble rarely all fire at exactly the same moment, i.e. fully synchronized. Instead, the probability of firing is rhythmically modulated such that neurons are more likely to fire at the same time, which gives rise to oscillations in their mean activity (see figure at top of page). As such, the frequency of large-scale oscillations does not need to match the firing pattern of individual neurons. Isolated cortical neurons fire regularly under certain conditions, but in the intact brain cortical cells are bombarded by highly fluctuating synaptic inputs and typically fire seemingly at random. However, if the probability of a large group of neurons is rhythmically modulated at a common frequency, they will generate oscillations in the mean field (see also figure at top of page). Neural ensembles can generate oscillatory activity endogenously through local interactions between excitatory and inhibitory neurons. In particular, inhibitory interneurons play an important role in producing neural ensemble synchrony by generating a narrow window for effective excitation and rhythmically modulating the firing rate of excitatory neurons.


title: Neural oscillation

text: Neural oscillation can also arise from interactions between different brain areas coupled through the structural connectome. Time delays play an important role here. Because all brain areas are bidirectionally coupled, these connections between brain areas form feedback loops. Positive feedback loops tend to cause oscillatory activity where frequency is inversely related to the delay time. An example of such a feedback loop is the connections between the thalamus and cortex – the thalamocortical radiations. This thalamocortical network is able to generate oscillatory activity known as recurrent thalamo-cortical resonance. The thalamocortical network plays an important role in the generation of alpha activity. In a whole-brain network model with realistic anatomical connectivity and propagation delays between brain areas, oscillations in the beta frequency range emerge from the partial synchronisation of subsets of brain areas oscillating in the gamma-band (generated at the mesoscopic level).


title: Neural oscillation

text: Scientists have identified some intrinsic neuronal properties that play an important role in generating membrane potential oscillations. In particular, voltage-gated ion channels are critical in the generation of action potentials. The dynamics of these ion channels have been captured in the well-established Hodgkin–Huxley model that describes how action potentials are initiated and propagated by means of a set of differential equations. Using bifurcation analysis, different oscillatory varieties of these neuronal models can be determined, allowing for the classification of types of neuronal responses. The oscillatory dynamics of neuronal spiking as identified in the Hodgkin–Huxley model closely agree with empirical findings. In addition to periodic spiking, subthreshold membrane potential oscillations, i.e. resonance behavior that does not result in action potentials, may also contribute to oscillatory activity by facilitating synchronous activity of neighboring neurons. Like pacemaker neurons in central pattern generators, subtypes of cortical cells fire bursts of spikes (brief clusters of spikes) rhythmically at preferred frequencies. Bursting neurons have the potential to serve as pacemakers for synchronous network oscillations, and bursts of spikes may underlie or enhance neuronal resonance.


title: Neural oscillation

text: Apart from intrinsic properties of neurons, biological neural network properties are also an important source of oscillatory activity. Neurons communicate with one another via synapses and affect the timing of spike trains in the post-synaptic neurons. Depending on the properties of the connection, such as the coupling strength, time delay and whether coupling is excitatory or inhibitory, the spike trains of the interacting neurons may become synchronized. Neurons are locally connected, forming small clusters that are called neural ensembles. Certain network structures promote oscillatory activity at specific frequencies. For example, neuronal activity generated by two populations of interconnected "inhibitory" and "excitatory" cells can show spontaneous oscillations that are described by the Wilson-Cowan model.


title: Neural oscillation

text: If a group of neurons engages in synchronized oscillatory activity, the neural ensemble can be mathematically represented as a single oscillator. Different neural ensembles are coupled through long-range connections and form a network of weakly coupled oscillators at the next spatial scale. Weakly coupled oscillators can generate a range of dynamics including oscillatory activity. Long-range connections between different brain structures, such as the thalamus and the cortex (see thalamocortical oscillation), involve time-delays due to the finite conduction velocity of axons. Because most connections are reciprocal, they form feed-back loops that support oscillatory activity. Oscillations recorded from multiple cortical areas can become synchronized to form large scale brain networks, whose dynamics and functional connectivity can be studied by means of spectral analysis and Granger causality measures. Coherent activity of large-scale brain activity may form dynamic links between brain areas required for the integration of distributed information.


title: Neural oscillation

text: In addition to fast direct synaptic interactions between neurons forming a network, oscillatory activity is regulated by neuromodulators on a much slower time scale. That is, the concentration levels of certain neurotransmitters are known to regulate the amount of oscillatory activity. For instance, GABA concentration has been shown to be positively correlated with frequency of oscillations in induced stimuli. A number of nuclei in the brainstem have diffuse projections throughout the brain influencing concentration levels of neurotransmitters such as norepinephrine, acetylcholine and serotonin. These neurotransmitter systems affect the physiological state, e.g., wakefulness or arousal, and have a pronounced effect on amplitude of different brain waves, such as alpha activity.


title: Neural oscillation

text: Oscillations can often be described and analyzed using mathematics. Mathematicians have identified several dynamical mechanisms that generate rhythmicity. Among the most important are harmonic (linear) oscillators, limit cycle oscillators, and delayed-feedback oscillators. Harmonic oscillations appear very frequently in nature—examples are sound waves, the motion of a pendulum, and vibrations of every sort. They generally arise when a physical system is perturbed by a small degree from a minimum-energy state, and are well understood mathematically. Noise-driven harmonic oscillators realistically simulate alpha rhythm in the waking EEG as well as slow waves and spindles in the sleep EEG. Successful EEG analysis algorithms were based on such models. Several other EEG components are better described by limit-cycle or delayed-feedback oscillations. Limit-cycle oscillations arise from physical systems that show large deviations from equilibrium, whereas delayed-feedback oscillations arise when components of a system affect each other after significant time delays. Limit-cycle oscillations can be complex but there are powerful mathematical tools for analyzing them; the mathematics of delayed-feedback oscillations is primitive in comparison. Linear oscillators and limit-cycle oscillators qualitatively differ in terms of how they respond to fluctuations in input. In a linear oscillator, the frequency is more or less constant but the amplitude can vary greatly. In a limit-cycle oscillator, the amplitude tends to be more or less constant but the frequency can vary greatly. A heartbeat is an example of a limit-cycle oscillation in that the frequency of beats varies widely, while each individual beat continues to pump about the same amount of blood.


title: Neural oscillation

text: Computational models adopt a variety of abstractions in order to describe complex oscillatory dynamics observed in brain activity. Many models are used in the field, each defined at a different level of abstraction and trying to model different aspects of neural systems. They range from models of the short-term behaviour of individual neurons, through models of how the dynamics of neural circuitry arise from interactions between individual neurons, to models of how behaviour can arise from abstract neural modules that represent complete subsystems.


title: Neural oscillation

text: A model of a biological neuron is a mathematical description of the properties of nerve cells, or neurons, that is designed to accurately describe and predict its biological processes. The most successful and widely used model of neurons, the Hodgkin–Huxley model, is based on data from the squid giant axon. It is a set of nonlinear ordinary differential equations that approximates the electrical characteristics of a neuron, in particular the generation and propagation of action potentials. The model is very accurate and detailed and Hodgkin and Huxley received the 1963 Nobel Prize in physiology or medicine for this work.


title: Neural oscillation

text: The mathematics of the Hodgkin–Huxley model are quite complicated and several simplifications have been proposed, such as the FitzHugh–Nagumo model, the Hindmarsh–Rose model or the capacitor-switch model as an extension of the integrate-and-fire model. Such models only capture the basic neuronal dynamics, such as rhythmic spiking and bursting, but are more computationally efficient. This allows the simulation of a large number of interconnected neurons that form a neural network.


title: Neural oscillation

text: A neural network model describes a population of physically interconnected neurons or a group of disparate neurons whose inputs or signalling targets define a recognizable circuit. These models aim to describe how the dynamics of neural circuitry arise from interactions between individual neurons. Local interactions between neurons can result in the synchronization of spiking activity and form the basis of oscillatory activity. In particular, models of interacting pyramidal cells and inhibitory interneurons have been shown to generate brain rhythms such as gamma activity. Similarly, it was shown that simulations of neural networks with a phenomenological model for neuronal response failures can predict spontaneous broadband neural oscillations.


title: Neural oscillation

text: Neural field models are another important tool in studying neural oscillations and are a mathematical framework describing evolution of variables such as mean firing rate in space and time. In modeling the activity of large numbers of neurons, the central idea is to take the density of neurons to the continuum limit, resulting in spatially continuous neural networks. Instead of modelling individual neurons, this approach approximates a group of neurons by its average properties and interactions. It is based on the mean field approach, an area of statistical physics that deals with large-scale systems. Models based on these principles have been used to provide mathematical descriptions of neural oscillations and EEG rhythms. They have for instance been used to investigate visual hallucinations.


title: Neural oscillation

text: The Kuramoto model of coupled phase oscillators is one of the most abstract and fundamental models used to investigate neural oscillations and synchronization. It captures the activity of a local system (e.g., a single neuron or neural ensemble) by its circular phase alone and hence ignores the amplitude of oscillations (amplitude is constant). Interactions amongst these oscillators are introduced by a simple algebraic form (such as a sine function) and collectively generate a dynamical pattern at the global scale. The Kuramoto model is widely used to study oscillatory brain activity and several extensions have been proposed that increase its neurobiological plausibility, for instance by incorporating topological properties of local cortical connectivity. In particular, it describes how the activity of a group of interacting neurons can become synchronized and generate large-scale oscillations. Simulations using the Kuramoto model with realistic long-range cortical connectivity and time-delayed interactions reveal the emergence of slow patterned fluctuations that reproduce resting-state BOLD functional maps, which can be measured using fMRI.


title: Neural oscillation

text: Both single neurons and groups of neurons can generate oscillatory activity spontaneously. In addition, they may show oscillatory responses to perceptual input or motor output. Some types of neurons will fire rhythmically in the absence of any synaptic input. Likewise, brain-wide activity reveals oscillatory activity while subjects do not engage in any activity, so-called resting-state activity. These ongoing rhythms can change in different ways in response to perceptual input or motor output. Oscillatory activity may respond by increases or decreases in frequency and amplitude or show a temporary interruption, which is referred to as phase resetting. In addition, external activity may not interact with ongoing activity at all, resulting in an additive response.


title: Neural oscillation

text: Spontaneous activity is brain activity in the absence of an explicit task, such as sensory input or motor output, and hence also referred to as resting-state activity. It is opposed to induced activity, i.e. brain activity that is induced by sensory stimuli or motor responses. The term "ongoing brain activity" is used in electroencephalography and magnetoencephalography for those signal components that are not associated with the processing of a stimulus or the occurrence of specific other events, such as moving a body part, i.e. events that do not form evoked potentials/evoked fields, or induced activity. Spontaneous activity is usually considered to be noise if one is interested in stimulus processing; however, spontaneous activity is considered to play a crucial role during brain development, such as in network formation and synaptogenesis. Spontaneous activity may be informative regarding the current mental state of the person (e.g. wakefulness, alertness) and is often used in sleep research. Certain types of oscillatory activity, such as alpha waves, are part of spontaneous activity. Statistical analysis of power fluctuations of alpha activity reveals a bimodal distribution, i.e. a high- and low-amplitude mode, and hence shows that resting-state activity does not just reflect a noise process. In case of fMRI, spontaneous fluctuations in the blood-oxygen-level dependent (BOLD) signal reveal correlation patterns that are linked to resting states networks, such as the default network. The temporal evolution of resting state networks is correlated with fluctuations of oscillatory EEG activity in different frequency bands.


title: Neural oscillation

text: Ongoing brain activity may also have an important role in perception, as it may interact with activity related to incoming stimuli. Indeed, EEG studies suggest that visual perception is dependent on both the phase and amplitude of cortical oscillations. For instance, the amplitude and phase of alpha activity at the moment of visual stimulation predicts whether a weak stimulus will be perceived by the subject.


title: Neural oscillation

text: In response to input, a neuron or neuronal ensemble may change the frequency at which it oscillates, thus changing the rate at which it spikes. Often, a neuron's firing rate depends on the summed activity it receives. Frequency changes are also commonly observed in central pattern generators and directly relate to the speed of motor activities, such as step frequency in walking. However, changes in "relative" oscillation frequency between different brain areas is not so common because the frequency of oscillatory activity is often related to the time delays between brain areas.


title: Neural oscillation

text: Next to evoked activity, neural activity related to stimulus processing may result in induced activity. Induced activity refers to modulation in ongoing brain activity induced by processing of stimuli or movement preparation. Hence, they reflect an indirect response in contrast to evoked responses. A well-studied type of induced activity is amplitude change in oscillatory activity. For instance, gamma activity often increases during increased mental activity such as during object representation. Because induced responses may have different phases across measurements and therefore would cancel out during averaging, they can only be obtained using time-frequency analysis. Induced activity generally reflects the activity of numerous neurons: amplitude changes in oscillatory activity are thought to arise from the synchronization of neural activity, for instance by synchronization of spike timing or membrane potential fluctuations of individual neurons. Increases in oscillatory activity are therefore often referred to as event-related synchronization, while decreases are referred to as event-related desynchronization.


title: Neural oscillation

text: Phase resetting occurs when input to a neuron or neuronal ensemble resets the phase of ongoing oscillations. It is very common in single neurons where spike timing is adjusted to neuronal input (a neuron may spike at a fixed delay in response to periodic input, which is referred to as phase locking) and may also occur in neuronal ensembles when the phases of their neurons are adjusted simultaneously. Phase resetting is fundamental for the synchronization of different neurons or different brain regions because the timing of spikes can become phase locked to the activity of other neurons.


title: Neural oscillation

text: Phase resetting also permits the study of evoked activity, a term used in electroencephalography and magnetoencephalography for responses in brain activity that are directly related to stimulus-related activity. Evoked potentials and event-related potentials are obtained from an electroencephalogram by stimulus-locked averaging, i.e. averaging different trials at fixed latencies around the presentation of a stimulus. As a consequence, those signal components that are the same in each single measurement are conserved and all others, i.e. ongoing or spontaneous activity, are averaged out. That is, event-related potentials only reflect oscillations in brain activity that are phase-locked to the stimulus or event. Evoked activity is often considered to be independent from ongoing brain activity, although this is an ongoing debate.


title: Neural oscillation

text: It has recently been proposed that even if phases are not aligned across trials, induced activity may still cause event-related potentials because ongoing brain oscillations may not be symmetric and thus amplitude modulations may result in a baseline shift that does not average out. This model implies that slow event-related responses, such as asymmetric alpha activity, could result from asymmetric brain oscillation amplitude modulations, such as an asymmetry of the intracellular currents that propagate forward and backward down the dendrites. Under this assumption, asymmetries in the dendritic current would cause asymmetries in oscillatory activity measured by EEG and MEG, since dendritic currents in pyramidal cells are generally thought to generate EEG and MEG signals that can be measured at the scalp.


title: Neural oscillation

text: Neural synchronization can be modulated by task constraints, such as attention, and is thought to play a role in feature binding, neuronal communication, and motor coordination. Neuronal oscillations became a hot topic in neuroscience in the 1990s when the studies of the visual system of the brain by Gray, Singer and others appeared to support the neural binding hypothesis. According to this idea, synchronous oscillations in neuronal ensembles bind neurons representing different features of an object. For example, when a person looks at a tree, visual cortex neurons representing the tree trunk and those representing the branches of the same tree would oscillate in synchrony to form a single representation of the tree. This phenomenon is best seen in local field potentials which reflect the synchronous activity of local groups of neurons, but has also been shown in EEG and MEG recordings providing increasing evidence for a close relation between synchronous oscillatory activity and a variety of cognitive functions such as perceptual grouping and attentional top-down control.


title: Neural oscillation

text: Cells in the sinoatrial node, located in the right atrium of the heart, spontaneously depolarize approximately 100 times per minute. Although all of the heart's cells have the ability to generate action potentials that trigger cardiac contraction, the sinoatrial node normally initiates it, simply because it generates impulses slightly faster than the other areas. Hence, these cells generate the normal sinus rhythm and are called pacemaker cells as they directly control the heart rate. In the absence of extrinsic neural and hormonal control, cells in the SA node will rhythmically discharge. The sinoatrial node is richly innervated by the autonomic nervous system, which up or down regulates the spontaneous firing frequency of the pacemaker cells.


title: Neural oscillation

text: Synchronized firing of neurons also forms the basis of periodic motor commands for rhythmic movements. These rhythmic outputs are produced by a group of interacting neurons that form a network, called a central pattern generator. Central pattern generators are neuronal circuits that—when activated—can produce rhythmic motor patterns in the absence of sensory or descending inputs that carry specific timing information. Examples are walking, breathing, and swimming, Most evidence for central pattern generators comes from lower animals, such as the lamprey, but there is also evidence for spinal central pattern generators in humans.


title: Neural oscillation

text: Neuronal spiking is generally considered the basis for information transfer in the brain. For such a transfer, information needs to be coded in a spiking pattern. Different types of coding schemes have been proposed, such as rate coding and temporal coding. Neural oscillations could create periodic time windows in which input spikes have larger effect on neurons, thereby providing a mechanism for decoding temporal codes.


title: Neural oscillation

text: Synchronization of neuronal firing may serve as a means to group spatially segregated neurons that respond to the same stimulus in order to bind these responses for further joint processing, i.e. to exploit temporal synchrony to encode relations. Purely theoretical formulations of the binding-by-synchrony hypothesis were proposed first, but subsequently extensive experimental evidence has been reported supporting the potential role of synchrony as a relational code.


title: Neural oscillation

text: The functional role of synchronized oscillatory activity in the brain was mainly established in experiments performed on awake kittens with multiple electrodes implanted in the visual cortex. These experiments showed that groups of spatially segregated neurons engage in synchronous oscillatory activity when activated by visual stimuli. The frequency of these oscillations was in the range of 40 Hz and differed from the periodic activation induced by the grating, suggesting that the oscillations and their synchronization were due to internal neuronal interactions. Similar findings were shown in parallel by the group of Eckhorn, providing further evidence for the functional role of neural synchronization in feature binding. Since then, numerous studies have replicated these findings and extended them to different modalities such as EEG, providing extensive evidence of the functional role of gamma oscillations in visual perception.


title: Neural oscillation

text: Gilles Laurent and colleagues showed that oscillatory synchronization has an important functional role in odor perception. Perceiving different odors leads to different subsets of neurons firing on different sets of oscillatory cycles. These oscillations can be disrupted by GABA blocker picrotoxin, and the disruption of the oscillatory synchronization leads to impairment of behavioral discrimination of chemically similar odorants in bees and to more similar responses across odors in downstream β-lobe neurons. Recent follow-up of this work has shown that oscillations create periodic integration windows for Kenyon cells in the insect mushroom body, such that incoming spikes from the antennal lobe are more effective in activating Kenyon cells only at specific phases of the oscillatory cycle.


title: Neural oscillation

text: Neural oscillations are also thought be involved in the sense of time and in somatosensory perception. However, recent findings argue against a clock-like function of cortical gamma oscillations.


title: Neural oscillation

text: Oscillations have been commonly reported in the motor system. Pfurtscheller and colleagues found a reduction in alpha (8–12 Hz) and beta (13–30 Hz) oscillations in EEG activity when subjects made a movement. Using intra-cortical recordings, similar changes in oscillatory activity were found in the motor cortex when the monkeys performed motor acts that required significant attention. In addition, oscillations at spinal level become synchronised to beta oscillations in the motor cortex during constant muscle activation, as determined by cortico-muscular coherence. Likewise, muscle activity of different muscles reveals inter-muscular coherence at multiple distinct frequencies reflecting the underlying neural circuitry involved in motor coordination.


title: Neural oscillation

text: Recently it was found that cortical oscillations propagate as travelling waves across the surface of the motor cortex along dominant spatial axes characteristic of the local circuitry of the motor cortex. It has been proposed that motor commands in the form of travelling waves can be spatially filtered by the descending fibres to selectively control muscle force. Simulations have shown that ongoing wave activity in cortex can elicit steady muscle force with physiological levels of EEG-EMG coherence.


title: Neural oscillation

text: Oscillatory rhythms at 10 Hz have been recorded in a brain area called the inferior olive, which is associated with the cerebellum. These oscillations are also observed in motor output of physiological tremor and when performing slow finger movements. These findings may indicate that the human brain controls continuous movements intermittently. In support, it was shown that these movement discontinuities are directly correlated to oscillatory activity in a cerebello-thalamo-cortical loop, which may represent a neural mechanism for the intermittent motor control.


title: Neural oscillation

text: Neural oscillations, in particular theta activity, are extensively linked to memory function. Theta rhythms are very strong in rodent hippocampi and entorhinal cortex during learning and memory retrieval, and they are believed to be vital to the induction of long-term potentiation, a potential cellular mechanism for learning and memory. Coupling between theta and gamma activity is thought to be vital for memory functions, including episodic memory. Tight coordination of single-neuron spikes with local theta oscillations is linked to successful memory formation in humans, as more stereotyped spiking predicts better memory.