When the vestibular system and the visual system report incongruous states of motion, the result is often nausea and other symptoms of disorientation known as motion sickness. According to contemporary sensory conflict theory, such conditions happen when the vestibular system and the visual system do not present a synchronized and unified representation of one's body and surroundings. This theory is also known as neural mismatch, implying a mismatch occurring between ongoing sensory experience and long-term memory rather than between components of the vestibular and visual systems, emphasizing "the limbic system in integration of sensory information and long-term memory, in the expression of the symptoms of motion sickness, and the impact of anti-motion-sickness drugs and stress hormones on limbic system function. The limbic system may be the neural mismatch center of the brain." At present a "fully adequate theory of motion sickness is not presently available" but at present the sensory conflict theory, referring to "a discontinuity between either visual, proprioceptive, and somatosensory input, or semicircular canal and otolith input", may be the best available. Main health effects of sleep deprivation.<unk>  or<unk>  sickness is a kind of motion sickness that can occur when one's surroundings visually appear to be in motion, but without a corresponding sense of bodily motion. This incongruous condition can occur during<unk>  travel when changes in g-forces compromise one's spatial orientation. According to Science Daily, "Gravity plays a major role in our spatial orientation. Changes in gravitational forces, such as the transition to weightlessness during a<unk>  voyage, influence our spatial orientation and require<unk>  by many of the physiological processes in which our balance system plays a part. As long as this<unk>  is incomplete, this can be coupled to nausea, visual illusions, and disorientation." Sleep deprivation can also increase susceptibility to<unk>  sickness, making symptoms worse and longer-lasting. According to the sensory conflict hypothesis,<unk>  sickness is the opposite of the kinds of motion-related disorientation that occur in the presence of gravity, known as terrestrial motion sickness, such as becoming carsick, seasick, or airsick. In such cases, and in contrast to<unk>  sickness, one's surroundings seem visually immobile (such as inside a car or airplane or a cabin below decks) while one's body feels itself to be in motion. Contemporary motion sickness medications can counter various forms of motion disorientation including<unk>  sickness by temporarily suppressing the vestibular system, but are rarely used for<unk>  travel because it is considered better to allow<unk>  travelers to adapt naturally over the first one to seven days rather than to suffer the drowsiness and other side effects of medication taken over a longer period. However, transdermal dimenhydrinate anti-nausea patches are typically used whenever<unk>  suits are worn because vomiting into a<unk>  suit could be fatal by obscuring vision or blocking airflow.<unk>  suits are generally worn during launch and landing by NASA crew members and always for extra-vehicular activities (EVAs). EVAs are consequently not usually scheduled for the first days of a mission to allow the crew to adapt, and transdermal dimenhydrinate patches are typically used as an additional backup measure.
Space adaptation syndrome
Foreign accent syndrome
Serotonin syndrome
Cannabinoid hyperemesis syndrome
Adrenergic storm
Vasoplegic syndrome
Cholinergic crisis
Monofixation syndrome