Crossmodal plasticity in core auditory cortex following deafness: An evaluation of evidence for and against.

Over the past few decades, a great deal of evidence from studies of humans and animal models has demonstrated crossmodal plasticity in higher-order auditory cortical areas of the deaf. However, whether crossmodal plasticity occurs in core auditory cortex following deafness remains controversial. This review critically examines evidence for and against crossmodal plasticity in core auditory cortex following deafness in both humans and animals. First, we define core auditory cortex and discuss evidence for crossmodal inputs to these regions during normal development. Then, neuroanatomical and functional evidence for and against crossmodal reorganization in the deaf auditory cortical core, drawn from electrophysiological, neuroimaging, and cryogenic deactivation studies is presented and discussed. On balance, the available evidence suggests that crossmodal reorganization can occur in core auditory cortex in some species and experimental models, although the extent, functional significance, and generality of these effects remain incompletely understood. Future studies that account for anesthetic effects, and which include primate models will be critical to settling this debate and better understanding the nature of plasticity following sensory loss.