Grant: Operating Grant

Good processing of sound is critical for development of normal communication through music and language. Sound is processed in the ear and then through multiple subcortical and cortical regions in the brain. In addition to feedforward connections, there are massive feedback connections from cortex to subcortical regions. Subcortical structures maintain robust representations of basic features of incoming sounds (e.g., frequency, timing) whereas cortex uses this spectrotemporal information to form meaningful representations of complex sounds, including voices and musical instruments. In adults, through feedback connections, cortex is able to instruct or prime subcortical regions to provide better processing of sound features that are critical for the next expected meaningful sound input. We test the hypothesis that because auditory cortex is very immature in early infancy, information flow is largely bottom up, but that with increasing cortical maturation, the downward influence of cortex increasingly affects subcortical processing. Using electrophysiology (EEG) we have developed a method to probe responses to sound in various cortical and subcortical regions at the same time. We will first track the normal development of and interaction between cortical and subcortical responses to sound over the first year after birth. We will then examine how this affects the development of attention and learning by examining how cortical and subcortical responses and their interactions are modified through specific listening experiences at different ages. This work will be significant and unique in providing the first comprehensive normative database of the timing and interaction of subcortical and cortical development and how it is affected by experience with particular sounds. It will also have clinical application for understanding conditions such as autism, central auditory processing deficits, and language impairment, in which auditory processing is compromised.