Age-related differences in auditory evoked responses during rapid perceptual learning

Objective: Young and older adults can learn to rapidly discriminate between elementary visual and auditory features. While growing evidence supports the notion that such behavioral improvement is paralleled by neuroplastic changes in corresponding sensory areas during adulthood, studies have not examined practice-related improvement in older adults and the corresponding changes in neural activity. Methods: We used event-related potentials (ERPs) to investigate the effects of age on rapid learning-related changes in listeners' ability to identify two phonetically different vowels presented simultaneously. Results: During the first hour of testing, young and older listeners showed comparable behavioral improvement in identifying both vowels. In young adults, learning was paralleled by enhanced amplitudes of early (130 ms) and late (320 ms) ERP waves over the right temporal lobe, as well as an increased negative wave over the midline parietal region, peaking at about 400 ms after sound onset. The practice-related changes over the right temporal lobe were not present in older adults whereas the learning effect observed over the parietal region was present in both young and older adults. In older adults, behavioral improvement was also associated with reduced N1 amplitude recorded at inferior and posterior temporal/occipital scalp sites while no such changes were observed in young adults. Conclusions: Age-related differences in neural activity during learning suggest that neural networks supporting behavioral improvements in speech segregation and identification change during the course of aging. Significance: This research highlights the role of practice on concurrent sound perception and may facilitate the development of training programs that may help older listeners to parse the auditory scene into component sound sources. (c) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.