Interaural temporal and coherence cues jointly contribute to successful sound movement perception and activation of parietal cortex

The perception of movement in the auditory modality requires dynamic changes in the input that reaches the two ears (e.g. sequential changes of interaural time differences; dynamic ITDs). However, it is still unclear as to what extent these temporal cues interact with other interaural cues to determine successful movement perception, and which brain regions are involved in sound movement processing. Here, we presented trains of white-noise bursts containing either static or dynamic ITDs, and we varied parametrically the level of binaural coherence (BC) of both types of stimuli. Behaviorally, we found that movement discrimination sensitivity decreased with decreasing levels of BC. fMRI analyses highlighted a network of temporal, frontal and parietal regions where activity decreased with decreasing BC. Critically, in the intra-parietal sulcus and the supra-marginal gyrus brain activity decreased with decreasing BC, but only for dynamic-ITD sounds (BC by ITD interaction). Thus, these regions activated selectively when the sounds contained both dynamic ITDs and high levels of BC; i.e. when subjects perceived sound movement. We conclude that sound movement perception requires both dynamic changes of the auditory input and effective sound-source localization, and that parietal cortex utilizes interaural temporal and coherence cues for the successful perception of sound movement.