cognition is defined as information processing in one s brain and ability to judge and make 
 decisions , and it covers various concepts such as attention , memory , executive planning , 
 insight , and problem solving1 , 2 . for normal cognitive function ,
the integration of sensory 
 information , visual perception , and language ability is required first , and loss of 
 attention and of memory impair cognitive function , such as problem solving and reasoning 
 ability3 . in rehabilitation training program ,
the adaptive approach , which focuses on recovery of 
 damaged cognitive function in the brain , is one of the common approaches in cognitive 
 rehabilitation .
it is based on the theory that neuroplasticity reorganizes the damaged 
 cerebral cortex , and it focuses on recovery of the damaged cognitive function and minimizing 
 the effects of the damage4 . as a method of functional brain imaging for brain wave testing ,
many different innovative 
 methods of radiological examination including the electroencephalogram , positron emission 
 tomography , magnetic resonance imaging , functional magnetic resonance imaging , and 
 single - photon emission computerized tomography have been used , and these methods can be used 
 to confirm the brain s functional changes by comparison with normal brains5 . compared with other experimental brain 
 imaging methods , brain wave measurement is a commonly used as a noninvasive method for 
 analyzing the changes in brain functions directly within a short period of time , and 
 providing a variety of useful information with data from a short examination6 .
it is also an electronic neurophysiological 
 experiment method that can be used to investigate the brain s functional status in real - time 
 while focusing on a specific assignment .
this is applicable to various patients suffering 
 from brain damage , alcoholism , and/or depression , and it can be used to analyze brain 
 functions objectively .
it makes it especially easy to observe the process of spatiotemporal 
 changes , and therefore , it is very useful for measuring cognitive load in real time7 .
neurofeedback ( nfb ) brain wave training based on the principle of brain plasticity is a 
 relatively novel method for cognitive rehabilitation .
this method involves training to 
 adjust brain waves within a specific range , and the optimum brain wave adjustment improves 
 the level of awakening and affects various functional elements of the patient .
therefore , 
 understanding brain waves should be among the highest research priorities8 , 9 .
the beta wave improves concentration and reaction time when activated with a brain wave 
 between 1235  hz . through beta wave activation , nfb training aims to improve cerebral 
 function by enabling patients to activate this brain wave by reinforcing or suppressing 
 certain frequencies based on visual and auditory feedback7 , 10 .
previous research has 
 shown that nfb is effective in improving cognitive functions including visual perception , 
 memory , and concentration in patients with brain injuries , such as traumatic brain injury or 
 stroke11 , 12 .
however , research on cognitive rehabilitation through nfb on 
 existing stroke patients has been limited to single case studies , and sufficient studies on 
 its effectiveness and clinical usability have not been conducted .
this study investigated the changes of a brain wave and visual perception following nfb and 
 the manner in which these changes affect daily life in stoke patients . also , we aimed to 
 indicate the effective therapeutic method to clinicians engaged in the cognitive 
 rehabilitation of patients with stroke .
the participants were recruited from among 28 stroke patients who received occupational and 
 physical therapy and were hospitalized at a general hospital in kyeongki province , republic 
 of korea , from june to july 2013 .
participant selection criteria included that the patient 
 should be hemiparalytic from a stroke within the previous 3 months to 1  year , be able to 
 follow verbal instructions , and be able to communicate at a certain level .
in addition , 
 participants were chosen from among patients who were able to perform all the tests and had 
 experienced light cognitive function failure that was scored between 18 and 23 on the 
 mini - mental state examination ( mmse ) .
a subject was eliminated if he / she had diplegia , never 
 attended a school , was biased , or had experienced nfb within the past year .
furthermore , all 
 subjects who participated in this trial provided a signed written consent form after having 
 the expected result and the side effects fully explained .
a total of 27 subjects eventually completed the 
 intervention and testing : 13 from the nfb group and 14 from the control group .
nfb training 
 was conducted over a period of 6 weeks , considering the hospitalization period .
as the 
 participants were recruited successively , the training was conducted over a 9-week period . 

the control group 
 received occupational and physical therapy for half an hour 5 times a week for 6 weeks .
the 
 nfb group received the same number of traditional rehabilitation sessions as the control 
 group with extra nfb training , respectively , for half an hour 5 times a week for 6 weeks . 

all of the protocols used in this study were approved by sahmyook university . before 
 participation
, the procedures , risks , and benefits were explained to all of the 
 participants , who gave their informed consent .
the participants rights were protected 
 according to the guidelines of sahmyook university . to perform the nfb training , a neurocomp system ( neurocybernetics inc . ,
encino , ca , usa ) , 
 composed of a repeater , a monitor for the clinician and the patient , computer , 
 electroencephalography ( eeg ) sensor , cables , and poles , was used for nfb .
the poles used in 
 nfb training were attached to the scalp , and data were recorded on an oscillograph .
the 
 location of the poles followed the international 1020 electrode system , and the distance 
 between each pole was 1020% of the whole circumference5 , 13 .
the nfb training method 
 used in this research was a beta - smr training method and was conducted with the patient s 
 eyes open .
the reward brain wave was set with either an smr wave ( 1215  hz ) or mid - beta wave ( 1518  hz ) 
 depending on the location of the cerebral cortex .
the inhibitory brain wave was set with 
 both a delta wave ( 0.54  hz ) and high - beta wave ( 2236  hz)7 , 8 , 12 .
the training time for a single trial was set at 30 minutes , during 
 which a 3-minute training module was conducted 10 times . for monopolar type training , a pole or nfb sensor was attached to a certain part of the 
 scalp ( c5 or c6 ) within the lesion area , and the remaining 2 poles were attached to both 
 ears with the participant seated on a comfortable chair .
we used 4 games that had a low level of difficulty and were 
 intriguing including space race , mazes , island , and boxlight .
participants played the games 
 by watching the monitor with the poles attached , and his / her awakening level was controlled . 

for the space race game , the spaceship was set to move forward and backward depending on 
 his / her level of brain wave activation .
a quantitative analysis of the brain wave data was performed using the complexity 2.0 
 software ( laxtha inc . ,
checked for any artifact inflow , and data for 180 seconds obtained from pattern observation 
 with the nfb system from the raw data of the measured brain excluding the first 10 
 seconds - were used for the analysis .
since delta waves between the 0.54  hz are likely to be 
 contaminated with noise such as eye blinking ( 24  hz ) and head movement due to an unstable 
 body position ( 0.51  hz ) , the range of 450  hz from the entire brain wave domain was also 
 extracted for the analysis .
the fast fourier transform ( fft ) filtering method was conducted 
 to convert the raw data into frequencies .
the x axis 
 represents the frequency and y axis represents the power value , which shows spectral 
 analysis of evoked potentials in brain .
the output value is the absolute band power , which 
 is the square of the signal amplitude .
the relative band power is the absolute power ratio 
 of a particular frequency band on values of absolute band power between 0 and 1 , and could 
 be in percentage ( 0100% ) .
this relative band power analysis was used to adjust for the 
 difference in skull thickness between test subjects and individual brain waves due to the 
 degree of tension during measurement .
the motor - free visual perception test ( mvpt ) was used for visual perception evaluation .
it 
 contains a total of 36 items with four multiple - choice response options worth 1 point each , 
 adding up to a maximum score of 36 .
the mvpt is a standardized evaluation tool for 
 individuals 1880  years of age and measures six different parts of visual perception 
 functions .
there are 5 items for visual discrimination ( vd ) , 5 items for form constancy 
 ( fc ) , 8 items for visual memory ( vm ) , 11 items for visual closure ( vc ) , and 4 items for 
 spatial relation ( sr ) .
moreover , the processing time to complete each item is measured for 
 all items ( 35 items ) except for item 4 .
the mvpt can be used on patients with damaged 
 physical function who have difficulty with writing , and the confidence level of test - retest 
 reliability for the mvpt r=0.770.8315 .
the differences 
 in the brain wave and visual perception within a group before and after the treatments were 
 tested using the paired t - test , whereas differences between groups were tested using the 
 independent t - test . for all data ,
the general characteristics of participants are shown in table 1table 1.general characteristics of the subjectsnfbcongender ( male / female)8/511/3age ( years)62.97.263.69.3lesion side ( right / left)9/48/5duration ( months)10.63.212.52.7mmse ( score)19.82.520.53.7all variables are presented as the meansd .
nfb : neurofeedback training group ; con : 
 control group ; mmse : mini - mental state examination . the brain wave values and
visual perception changes before and after nfb 
 training are shown in table 2table 2.comparison of brain waves and mvpt in each groupitemsubtestnfbconprepostprepostbrain waverelative beta wave*11.324.5215.455.51 * 8.583.8011.327.37(%)relative mid - beta wave2.171.022.811.32**1.530.612.171.61relative high beta wave*4.221.716.082.03 * 3.371.904.433.60acq * ( hz)0.20850.07770.34170.25230.19170.04510.29220.2976mvptraw score***20.764.3423.464.48**24.005.4325.215.17**(score)vd5.691.647.150.89**5.851.796.001.70fc2.530.963.150.80 * 3.211.053.640.84*vm4.301.794.691.93**5.351.445.501.45vc6.001.776.691.75**6.571.606.921.89sr2.231.012.690.85**3.001.173.140.86time ( second)*7.761.316.991.38***7.222.066.872.07**all variables are presented as meansd . *
nfb : 
 neurofeedback training group ; con : control group ; acq : attention concentration 
 quotient ; mvpt : motor - free visual perception test ; vd : visual discrimination ; fc : form 
 constancy ; vm : visual memory ; vc : visual closure ; sr : spatial relation ; time : visual 
 perceptual processing time .
brain wave measurement before and after nfb training revealed a statistically 
 significant difference for the nfb group s relative beta wave value and attention 
 concentration quotient ( acq ) ( p<0.05 ) .
comparison of the difference before and after the 
 interventions between the two groups revealed that the nfb group s relative wave values and 
 acqs were significantly different ( p<0.05 ) . for the nfb group ,
there were differences in 
 vd , fc , vm , vc , and sr before and after the experiment .
comparison of the differences before 
 and after the interventions between the two groups revealed significant differences in mvpt 
 raw score and processing time ( p<0.05 ) .
nfb : neurofeedback training group ; con : 
 control group ; mmse : mini - mental state examination all variables are presented as meansd . * p<0.05 ; * * p<0.01 ; * * * p<0.001
. nfb : 
 neurofeedback training group ; con : control group ; acq : attention concentration 
 quotient ; mvpt : motor - free visual perception test ; vd : visual discrimination ; fc : form 
 constancy ; vm : visual memory ; vc : visual closure ; sr : spatial relation ; time : visual 
 perceptual processing time
nfb is developing along with technical development of quantitative eeg , computer devices , 
 and individual medical protocols . while performing assignments that require more attention 
 than in a steady state , alpha waves
are controlled and beta waves are increased ; 
 vitalization of beta wave reflects cognitive function improvement14 , 16 .
the smr waves 
 in beta waves were found to be in an appropriately steady state and to maintain attention 
 and wakefulness .
promotion of smr wave activity is also used in a treatment to relieve 
 impulsivity and involuntary movements17 . 

smr - beta wave training is an effective interventional approach for treatment of attention 
 and cognitive impairment , whereas nfb training supports and improves the neurophysiological 
 function level .
performance of eeg before and after nfb training revealed statistically significant 
 differences in the nfb group s relative beta wave value and acq ( p<0.05 ) .
comparison of 
 the differences before and after the interventions between the two groups revealed 
 significant differences in the nfb group s relative beta wave values and acqs compared with 
 the control group ( p<0.05 ) .
relative beta wave value went up when attention increased , 
 and acq reflects improvements in attention .
the results of this study indicate that the 
 increased relative beta wave value and aco resulted in significant improvement compared with 
 the control group .
lopez - larraz et al.18 reported that nfb increased cognitive 
 ability and concentration for various diseases , and gevensleben et al.19 claimed that nfb using the beta wave is effective for 
 improvement of concentration , although their research was performed with adhd patients . in 
 this study , we observed that nfb led to notable differences in attention and concentration 
 after the intervention .
this difference may have been due to the neurobiological reaction to 
 nfb , which affects the beta wave and the concentration brain waves .
thus , nfb would be a 
 prevailing choice for patients who require attention and concentration training .
visual perception is a process in which the central nervous system integrates visual 
 information to adapt to the environment and converts the information to cognitive concepts 
 for decision - making .
this process has a hierarchical structure consisting of oculomotor 
 control , visual fields , visual acuity , visual attention , visual scanning , pattern 
 recognition , and visual memory , and the highest visual percptual process in the hierarchy is 
 visual cognition2 . through training of 
 visual scanning , visuospatial orientation , and visual judgment ,
the damaged visual 
 perception functions of stroke patients can be improved to enhance recognition ability and 
 activities of daily living .
regarding visual perception before and after nfb , both the nfb group and control group 
 showed statistically significant differences in mvpt raw score and processing time .
for the 
 nfb group , there were differences in vd , fc , vm , vc , and sr before and after the 
 intervention .
comparison of the differences between the two groups revealed significant 
 differences in the mvpt raw score and processing time ( p<0.05 ) .
nfb training was found to 
 be more effective in changing visual perception change compared with traditional 
 rehabilitation training ( p<0.05 ) .
the nfb program is considered to have been more 
 effective in improving visual perception ability because the training was on watching and 
 focusing with the eyes .
more research into the development of an attention and concentration training program that 
 fits the rehabilitation purpose of not only stroke patients but also patients with other 
 illnesses is necessary .
in addition , post - test check - ups should be performed to determine 
 how long the changes last . standardized and more elaborate eeg measurement and analysis are 
 required to provide sufficient evidence for neurofeedback brain wave training .
 [ purpose ] this study investigated a brain wave and visual perception changes in stroke 
 subjects using neurofeedback ( nfb ) training . 
 [ subjects ] twenty - seven stroke subjects were 
 randomly allocated to the nfb ( n = 13 ) group and the control group ( n=14 ) . 
 [ methods ] two 
 expert therapists provided the nfb and con groups with traditional rehabilitation therapy 
 in 30 thirst - minute sessions over the course of 6 weeks . 
 nfb training was provided only to 
 the nfb group . 
 the con group received traditional rehabilitation therapy only . before and 
 after the 6-week intervention 
 , a brain wave test and motor free visual perception test 
 ( mvpt ) were performed . 
 [ results ] both groups showed significant differences in their 
 relative beta wave values and attention concentration quotients . 
 moreover , the nfb group 
 showed a significant difference in mvpt visual discrimination , form constancy , visual 
 memory , visual closure , spatial relation , raw score , and processing time . 
 [ conclusion ] 
 this study demonstrated that nfb training is more effective for increasing concentration 
 and visual perception changes than traditional rehabilitation . 
 in further studies , 
 detailed and diverse investigations should be performed considering the number and 
 characteristics of subjects , and the nfb training period . 