Postnatal Changes in Vestibular Reactions

Abstract

The difference in behaviour between post-rotatory sensation and nystagmus in a normal individual leads to the hypothesis of a central Inhibitory mechanism. Its activity can be shown in test subjects who are often submitted to strongly variable movements, e.g. fighter-pilots. In these pilots both sensation and nystagmus are even more reduced in duration than in normal individuals under normal circumstances. At the other end of the scale, the total lack of inhibition leads to extreme sensitivity to motion-sickness. The development of this inhibitory system is demonstrated in a new-born infant; 9 days after birth nystagmus has a very low threshold of 1°/sec and a rate of decline of 20 sec. In the following period the rate of decline decreases, attaining a value of 7 sec after 3 months, which is already nearly a normal value.