Investigating the Relationship between Subcortical and Cortical Auditory Processing

The auditory system is highly integrative, with feedforward and feedback connections from periphery to cortex (and stages in between). In order to understand how the different levels of the human auditory system interact, it is necessary to simultaneously measure responses from multiple auditory levels. A novel stimulus was paired with electroencephalography (EEG) in 29 young, normal-hearing participants (17-34 years) to examine interactions among stages of the auditory pathway. Temporal regularity was manipulated by continuously accelerating and decelerating the rate of a click-train stimulus (i.e., ~3.5 Hz frequency modulation of the click rate). Adaptation of the brainstem (cochlear nucleus and inferior colliculus) response latencies was observed simultaneously with cortical phase-locking and sustained low frequency activity to the temporal regularity. However, no correlations were found between subcortical adaptation and cortical regularity responses, suggesting that these phenomena may be independent of one another