The time course of

Listening training can change the neurophysiological responses of the human central auditory system. We and others have measured behavioral and neurophysiologic responses preand post-training and found that the magnitude of neurophysiological responses increases as perception improves.1–3 However, the relative time course of the neurophysiological changes and behavioral learning is unknown. Some visual training studies propose that changes in neurophysiology may precede changes in behavior.4,5 That is, if a time lag exists between neural changes and improved behavioral performance, there may be a period of consolidation when neural networks are thought to assemble to form meaningful codes which are later retrieved and manifested as behavior.6 However, no neurophysiological data exist to support this theory. Pre-perceptual learning in people has been a challenge to evaluate because non-invasive recording techniques are required in order to monitor changes in neurophysiology. By using event-related cortical potentials, which provide a means for measuring learning-related neural changes objectively, we examined the time course of learning neurophysiologically and behaviorally. Our hypothesis was that trainingassociated neurophysiological changes would precede behavioral learning.