Cortical voice processing is grounded in elementary sound analyses for vocalization relevant sound patterns

Abstract

A subregion of the auditory cortex (AC) was proposed to selectively process voices. This selectivity of the temporal voice area (TVA) and its role in processing non-voice sounds however have remained elusive. For a better functional description of the TVA, we investigated its neural responses both to voice and non-voice sounds, and critically also to textural sound patterns (TSPs) that share basic features with natural sounds but that are perceptually very distant from voices. Listening to these TSPs, first, elicited activity in large subregions of the TVA, which was mainly driven by perpetual ratings of TSPs along a voice similarity scale. This similar TVA activity in response to TSPs might partially explain activation patterns typically observed during voice processing. Second, we reconstructed the TVA activity that is usually observed in voice processing with a linear combination of activation patterns from TSPs. An analysis of the reconstruction model weights demonstrated that the TVA similarly processes both natural voice and non-voice sounds as well as TSPs along their acoustic and perceptual features. The predominant factor in reconstructing the TVA pattern by TSPs were the perceptual voice similarity ratings. Third, a multi-voxel pattern analysis confirms that the TSPs contain sufficient sound information to explain TVA activity for voice processing. Altogether, rather than being restricted to higher-order voice processing only, the human “voice area” uses mechanisms to evaluate the perceptual and acoustic quality of non-voice sounds, and responds to the latter with a “voice-like” processing pattern when detecting some rudimentary perceptual similarity with voices.