Evoked-potential changes following discrimination learning involving complex sounds

ObjectivePerceptual sensitivities are malleable via learning, even in adults. We trained adults to discriminate complex sounds (periodic, frequency-modulated sweep trains) using two different training procedures, and used psychoacoustic tests and evoked potential measures (the N1–P2 complex) to assess changes in both perceptual and neural sensitivities.MethodsTraining took place either on a single day, or daily across eight days, and involved discrimination of pairs of stimuli using a single-interval, forced-choice task. In some participants, training started with dissimilar pairs that became progressively more similar across sessions, whereas in others training was constant, involving only one, highly similar, stimulus pair.ResultsParticipants were better able to discriminate the complex sounds after training, particularly after progressive training, and the evoked potentials elicited by some of the sounds increased in amplitude following training. Significant amplitude changes were restricted to the P2 peak.ConclusionsOur findings indicate that changes in perceptual sensitivities parallel enhanced neural processing.SignificanceThese results are consistent with the proposal that changes in perceptual abilities arise from the brain’s capacity to adaptively modify cortical representations of sensory stimuli, and that different training regimens can lead to differences in cortical sensitivities, even after relatively short periods of training.

► Progressive training with complex sounds leads to more extensive behavioral and neural changes than constant training.
► Continuous sound presentations facilitate the measurement of learning-related plasticity of responses to change rather than responses evoked by transient onsets.
► Learning-related changes are evident after a single training session and can be directly observed using a single electrode.