The time course of learning: Neurophysiologic changes during speech training

Abstract

The ability of normal-hearing adults to identify and discriminate novel speech sounds improves with training. Neurophysiological changes associated with this improvement include increased duration and area, as well as shortened onset latency, of the mismatch negativity (MMN) [N. Kraus et al., J. Cog. Neurosci. 7, 25–32 (1995); K. Tremblay et al., J. Acoust. Soc. Am. 102, 1–12 (1997)]. The MMN is a passively elicited, preattentive, auditory event-related potential that reflects auditory discrimination and echoic memory [R. Naatanen et al., Acta Psychol. 42, 313–329 (1978)]. To date, little is known about the time course of neurophysiological change and the manifestation of learning. The present study examined the time course of perceptual learning and its relation to changes in the MMN with the expectation that cortically evoked potentials could provide insight into the biological processes underlying perceptual learning and serve as a clinical tool for evaluating change during efforts of (re)habilitation in the communicatively impaired. Specifically, it was found that neurophysiological change is apparent in the MMN preceding behavioral improvement. This suggests that auditory training alters the neural activity that provides the necessary coding of the speech stimuli and those changes are later integrated into functional behavior.