Auditory areas are recruited for naturalistic visual meaning in early deaf people

Abstract

Early deafness enhances responses of auditory cortices to non-auditory tasks, yet the nature of the reorganization is not well understood. Here, naturalistic stimuli were used to induce neural synchrony across early deaf and hearing individuals. Participants watched a silent animated film in an intact version and three versions with gradually distorted meaning. Differences between groups were observed in higher-order auditory cortices in all stimuli, with no significant effects in the primary auditory cortex. Comparison between levels of scrambling revealed a heterogeneity of function in secondary auditory areas. Both hemispheres showed greater synchrony for the intact movie than for low-level variants. However, the right hemisphere showed an increased inter-subject synchrony for the low-level movie variants, which was not present on the left. An event segmentation validated these results: the dynamics of the right secondary auditory cortex unfolded as shorter length events with more transitions than the left. It also uncovered a further left-right asymmetry: Only left-hemisphere patterns matched the patterns of the hippocampus, a brain region situated at the top of cortical hierarchy. Our results reveal how deaf subjects use their auditory cortex to process visual meaning.