Mechanisms and Treatment of Motion Illness

The question of why man develops motion sickness may be approached from several points of view. The human species is not alone in being susceptible to motion sickness: an equivalent pattern of symptoms can be induced by appropriate types of motion in a wide range of mammals (e.g. monkeys, horses, dogs, cats, seals) in birds, and even in fish. To the evolutionist, the problem is to understand what the survival value is of a pattern of symptoms evoked by certain types of motion stimulus that culminates in vomiting. From the practical point of view, it is necessary to know what the characteristics of those forms of motion are which lead to motion sickness as compared with those that do not. Such information also gives some indication of the likely neurophysiological mechanisms involved in motion sickness. From the point of view of the physiologist, interest is focussed on the mechanisms by which orientation and motion are sensed and on the sequence of events both within the central nervous system (CNS) and in other body systems that constitute the syndrome of motion sickness. Individual susceptibility in man varies widely and attempts have been made to find psychological and physiological measures that correlate with susceptibility. A further insight into the causal mechanisms of motion sickness comes from observation of the drugs which offer some protection. Such prophylactic drugs are drawn from several pharmacological groups, an indication that several neurotransmitters may be involved in the sequence of events leading to motion sickness.