Research report Age and experience-related improvements in gap detection in the rat Jennifer T. Friedman a, * , Ann M. Peiffer b , Matthew G. Clark c,1 , April A. Benasich a , R. Holly Fitch b a Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Avenue, Newark, NJ 07102, USA b Department of Psychology, Behavioral Neuroscience Division, University of Connecticut, 3107 Horse Barn Hill Road, Unit 4154, Storrs, CT 06269-4154, USA c Walter Reed Army Institute of Research, Division of Neuroscience, United States Accepted 2 June 2004 Available online 22 July 2004 Abstract The ability to accurately process brief, successive acoustic signals rapidly presented to the central nervous system is believed to underlie successful language development. The limits of temporal resolution of the auditory system, often assessed using gap detection tasks, has been widely studied in relation to developing and decoding speech. In the present study, a reflex modification paradigm was used to investigate potential shifts in gap detection thresholds in rats across development, with test sessions beginning on postnatal day (P) 15, P35 and P64. We found that thresholds decreased over the course of development. These thresholds were determined to lie between 10 and 20 ms for the P15 and P35 groups, and between 5 and 10 ms for the P64 group. Moreover, we observed improvements in gap detection thresholds in all age groups over 5 days of testing, including the youngest age group (P15). These later results suggest that experience-dependent plasticity mechanisms at the level of sensory processing are operational and observable both very early in development, and also in adult animals. The present findings also demonstrate maturational improvements in silent gap detection using a pre-pulse inhibition paradigm. D 2004 Elsevier B.V. All rights reserved. Theme: Development and regeneration Topic: Sensory systems Keywords: Auditory; Gap detection; Development; Experience; Plasticity 1. Introduction It is thought that fine auditory acuity, including the ability to detect brief silent gaps, is critical for accurate decoding of the speech stream. Moreover, the ability to process brief, successive and rapidly changing stimuli is believed to underlie the timely acquisition of early language. Slowed or inaccurate auditory processing may cause essential information to be missed, resulting in difficulty deciphering the speech stream. Individuals with auditory processing difficulties may thus exhibit deficits in phono- logical, syntactic and/or grammatical processing, and indeed, there is accumulating evidence that impaired auditory processing is characteristic of developmental language delays and impairments (for reviews, see Refs. [23,38]). One of the most widely used paradigms in the study of auditory temporal acuity is gap detection, classically defined as the ability to detect a brief silent period in otherwise continuous auditory background (typically white noise). Gap detection is an accepted and reliable behavioral 0165-3806/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.devbrainres.2004.06.007 * Corresponding author. Tel.: +1 973 353 1080x3213; fax: +1 973 353 1760. E-mail address: thomas@axon.rutgers.edu (J.T. Friedman). 1 This research was conducted in accordance with the principles stated in the Guide for the Care and Use of Laboratory Animals, National Research Council, National Academy Press, 1996, and the Animal Welfare Act of 1966, as amended. The views of the authors do not purport or reflect the position of the Department of the Army or the Department of Defense (para. 4-3, AR 360-5). Developmental Brain Research 152 (2004) 83 – 91 www.elsevier.com/locate/devbrainres