Auditory evoked potentials dissociate rapid perceptual learning from task repetition without learning.

Performance improvement during an hour of auditory perceptual training is accompanied by rapid physiological changes. These changes may reflect learning or simply task repetition independent of learning. We assessed the contribution of learning and task repetition to changes in auditory evoked potentials during a difficult speech identification task and an easy tone identification task. We posited that only task repetition effects would occur in the tone task but that task repetition and learning would interact in the speech task. Speech identification improved with practice (increased sensitivity d' with a constant response bias β). This behavioral improvement coincided with a decrease in the amplitude of sensory evoked responses (N1, P2) and a decrease in the amplitude of a slow wave (peak=320 ms after onset) over the left frontal and parietal sites. Results show rapid physiological changes associated with learning, distinct from changes related to task repetition.