Mechanism of perceptual transition: A study by dichotic presentation

Abstract

The perceptual transition occurs when a person hears a repeated single word without pause, illusory changes of the physically unchanging word are induced. We have been studying the conditions under which perceptual transitions occur. So far, it is unclear whether the perceptual transition occurs in the auditory system or in the brain processing. To elucidate this, we examined whether the perceptual transition occurred upstream or downstream of the superior olivary complex by dichotic presentation. Thirteen Japanese subjects were presented with six Japanese words. There are three types of presentation methods: (1) diotic presentation, (2) diotic presentation with ISI = stimulus length, and (3) dichotic presentation to the left and right ears alternately. We measured the time (T) until the perceptual transition occurred. If T in (3) is close to T in (1), the perceptual transition is thought to occur upstream of the superior olivary complex, and if T in (3) is close to T in (2), it is thought to occur downstream of the superior olivary complex. The results in (3) were almost equal to those in (1), suggesting the possibility that it occurs upstream from the superior olivary complex.