Perception modulates auditory cortex activation.

Event-related functional magnetic resonance imaging signal change in Heschl's gyrus and the planum temporale was found to reflect sensory decisions about target presence. In a dichotic listening task, activation was higher for target present responses, irrespective of actual target presence. In fact, activation was highest for false alarms, that is, 'present' responses in the absence of a target stimulus, and lowest for missed targets. This shows that activity at the earliest stage of cortical auditory processing reflects subjective perceptual decisions. Whether this activation is driven by bottom-up or top-down factors remains to be investigated.