What is the function of auditory cortex without auditory input?

Abstract

This scientific commentary refers to ‘Cross-modal activation of auditory regions during visuo-spatial working memory in early deafness’, by Ding et al. (doi:10.1093/brain/awv165). When a sensory input is absent during development, regions of the brain usually dedicated to processing input from that modality can be engaged to process input from a replacement sense. This is referred to as cross-modal plasticity, and studying it can provide rich and unique insights into the biological versus environmental constraints that act on brain development and brain function (Merabet and Pascal-Leone, 2010). For example, numerous studies report greater activation of typically ‘auditory association cortices’ in the superior temporal gyrus (STG), sulcus and planum temporale, in those born profoundly deaf than in their hearing peers when processing visual or somatosensory input (e.g. Karns et al. , 2012). There is also a wealth of research reporting enhanced behavioural performance on visuo-spatial tasks in deaf versus hearing participants (Bavelier et al. , 2006). Although it is tempting to make the intuitive assumption that these two findings must be linked, no studies with humans have yet demonstrated a clear link between the extent of cross-modal plasticity in auditory cortices in those born deaf and enhanced performance on visuo-spatial tasks. This is the question addressed by Ding and co-workers in this issue of Brain (2015). In their study, Ding e t al . asked hearing and congenitally deaf participants to perform a visuo-spatial working memory task while functional MRI data were collected. Deaf participants showed faster responses than hearing participants, although there was no group difference in task accuracy. In support of previous studies, Ding et al. report evidence of cross-modal plasticity (greater activation in deaf than hearing participants) in auditory …