There's more to auditory cortex than meets the ear

The auditory cortex is typically defined as that portion of the cortex containing neurons that respond to sound. This definition is adequate in a narrow context, but does not take into account sufficiently the subtleties associated with more complex behaviors and cognitive processes. Thus, it is easy to demonstrate that cortical regions essentially unrelated to sound processing may nevertheless be activated by an auditory stimulus; conversely, it is possible to demonstrate responses within classical auditory cortical regions in the complete absence of sound. We give several examples that indicate that responses in auditory cortex cannot be predicted based solely on knowledge of stimulus features. Rather, factors such as memory, attention, and mental imagery can be shown to play a major role in modulating or producing neural responses within auditory cortex. We argue that the interactions between classically defined auditory regions and other sensory, motor, and cognitive systems underlie many behaviors of interest; and that a more complete understanding of these processes will emerge from a consideration of the distributed nature of auditory cortical function.