Age-related differences in auditory evoked responses during rapid perceptual learning Claude Alain a,b, * , Joel S. Snyder c a Rotman Research Institute, Baycrest Centre for Geriatric Care, 3560 Bathurst Street, Toronto, Ont., Canada M6A 2E1 b Department of Psychology, University of Toronto, Ont., Canada c Department of Psychology, University of Nevada Las Vegas, USA Accepted 31 October 2007 Abstract 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 vow- els. In young adults, learning was paralleled by enhanced amplitudes of early (130 ms) and late (320 ms) ERP waves over the right tem- poral 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 pari- etal 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. Ó 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. Keywords: Auditory cortex; Plasticity; Learning; Evoked potential; Attention; Speech; Streaming; Aging 1. Introduction During the last decade, converging evidence from ani- mal and human research has revealed a remarkable degree of brain plasticity in the sensory and motor systems during adulthood. For instance, animal studies have revealed rapid and highly specific changes in the response properties of cells following classical conditioning (Bakin and Wein- berger, 1990; Edeline et al., 1993), instrumental avoidance conditioning (Bakin et al., 1996) and auditory discrimina- tion learning (Fritz et al., 2003). These rapid changes in the receptive fields were either smaller or absent when ani- mals listened passively to the same sounds (Fritz et al., 2003, 2005a,b), highlighting the importance of top–down attentional processes in rapid learning. However, as the training regimen continued over several daily practice ses- sions, the changes in receptive fields could be accompanied by changes in the topographical organization representing the trained sensory attributes (Recanzone et al., 1992, 1993; 1388-2457/$32.00 Ó 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2007.10.024 * Corresponding author. Address: Rotman Research Institute, Baycrest Centre for Geriatric Care, 3560 Bathurst Street, Toronto, Ont., Canada M6A 2E1. Tel.: +1 416 785 2500x3523; fax: +1 416 785 2862. E-mail address: calain@rotman-baycrest.on.ca (C. Alain). www.elsevier.com/locate/clinph Clinical Neurophysiology 119 (2008) 356–366