Introduction to Issues concerning Afternystagmus.

Afternystagmus, the concept of which has not yet been clearly defined, may be interpreted as a phenomenon which fits in phase II, or the reversal phase, of experimentally-induced nystagmus such as rotational or postrotational nystagmus or caloric nystagmus, in addition to optokinetic afternystagmus and its reversal phase and headshaking (after-) nystagmus including the reversal phase. A feature common to these phases of nystagmus may be the appearance of a temporary nystagmic reaction following, either immediately or after a definite interval of time (“latent period”), the elimination of an optokinetic stimulus or a physical vestibular stimulus that induces deviation of the cupula and then following the subsequent disappearance of excitement of the peripheral sensory organs, i.e., optic organ and vestibular labyrinth, that respond to these stimuli. Afternystagmus in this sense has never been generalized and the phenomenon may not actually be so simple. A panel discussion of this phenomenon and the neural mechanisms involved was held at the 51st Annual Meeting of the Japan Society for Equilibrium Research, which opened in Maebashi, Gunma prefecture on November 7, 1992