Effect of Context on Brainstem Encoding of Speech

Abstract

The dynamic nature of the brainstem response to speech allows for a means to examine how plasticity occurs at the level of brainstem in humans. It is not well understood if plasticity occurs as a result of long term experience or whether it is a continuous process. To obtain information on the extent to which plasticity is operational online, brainstem response to speech syllable /da/ was elicited in four conditions, which included one repetitive condition and three stimulus context conditions. Results showed that the latencies of onset and sustained responses were prolonged in the stimulus context conditions when compared to repetitive condition. Since the generators of the onset and the sustained responses (CN, LL and IC) fall within the feedback loop of the corticofugal pathway, the ability of the corticofugal pathway to identify spectral differences between the target stimulus and contextual stimulus is hypothesized to influence the brainstem responses. The results of the study suggest a possibility of online plasticity at the level of brainstem regulated by the corticofugal network.