Evoked potentials to auditory movement sensation in duplex perception

Objective: The purpose of this study was to examine the processing of auditory movement sensation accompanying duplex perception in binaural hearing. Methods: Stimuli were formant transitions (presented to the front, left or right of the subject) and base (presented to the front), that fused to result in vowel–consonant–vowel (V–C–V) sequences /aga/ and /ada/. An illusion of auditory movement (duplex sensation) accompanied the fusion of these V–C–V sequences when the spatial locations of the formant transitions and base were different. Ten right-handed, adult, native Hebrew speakers discriminated each fused stimulus, and the brain potentials associated with performance of the task were recorded from 21 electrodes. The processing of auditory movement was studied by a factorial design (ANOVA) and statistical non-parametric mapping (SnPM) of low resolution electromagnetic tomography (LORETA) images of the net-fusion response. Brain regions implicated in auditory movement processing were expected to be associated with the lateralized formant location, which gave rise to duplex perception. In addition, the time-course of significant activation in brain areas that differentiated between fusion conditions was determined. Results: The posterior parietal, anterior cingulate and premotor cortices were found to be implicated in duplex processing. Auditory cortex involvement was also evident, and together with the latter two brain regions was affected by right-ear advantage. Conclusions: Duplex perception resulting from fusion of spatially separate sounds forming an auditory object results in activation of a network of brain regions reflecting enhanced allocation of attention and the effect of language processing.