Age of Onset and Duration of Deafness Drive Brain Organization for Biological Motion Perception in Non-Signers

Abstract

We used fMRI to characterize the neural responses to biological motion in adults who became deaf at a wide range of ages, none of whom were fluent sign language users. Although hearing people showed stronger activation for communicative than non-communicative gestures throughout the occipito-temporal biological motion and frontal-parietal action perception networks, deaf people showed equivalent levels of activation to both types of stimuli, suggesting an enhanced sensitivity to biological motion. Deaf people exclusively showed responses to communicative gestures in the left superior temporal gyrus (associated with speech processing) and right inferior parietal lobe. Further, earlier onset and longer duration of deafness led to stronger cortical responses in the biological motion and action perception networks, and extended into left superior temporal lobe areas associated with speech and other auditory processing. Together these results demonstrate that auditory deprivation, in the absence of sign language experience, can profoundly change the sensitivity of cortical networks for communicative biological motion processing. Furthermore, we demonstrate for the first time that neuroplastic reorganization of the visual system can occur even in people who became deaf after childhood.