The Oculo-Gyral Illusion: A Form of Apparent Motion Which May Be Observed Following Stimulation of the Semicircular Canals

摘要

Conclusions: Rotatory acceleration may give rise to a visual illusion of movement which we have termed the oculo-gyral illusion. It is the result of nystagmus produced reflexly by stimulation of the sensory receptors in semicircular canals. In the light, and especially if visual cues are plentiful, relatively strong stimulation is required to produce even weak illusory effects. If an object is viewed in darkness, relatively weak stimulation will produce strong illusory effects. The threshold for stimulation in the case of the horizontal canals is in the neighborhood of 0.3 degrees per second per second. When the fixation object consists of a single light the oculogyral illusion is complicated by the phenomenon of autokinesis. The latter is largely abolished by using a three-dimensional target. The direction of the apparent movements of induced afterimages both during and following rotation is exactly opposite to that observed when a real target is fixated. The relationship between head position or change in head position and the direction of apparent movement indicates the relatively simple reflex character of the phenomenon. Hyoscine hydrobromide in doses as large as 3/200 of a grain had no appreciable effect on the oculo-gyral illusion. The oculo-gyral illusion offers a simple means of studying the sensitivity of the sensory receptors of the semicircular canals, the reflexly produced nystagmus and related phenomena. (Author)