Intensive training in adults refines A1 representations degraded in an early postnatal critical period

Xiaoming Zhou*,^† and
Michael M. Merzenich*,^‡

*The W. M. Keck Center for Integrative Neuroscience, The Coleman Laboratory, and Department of Otolaryngology, University of California, San Francisco, CA 94143; and
^†College of Life Sciences, East China Normal University, Shanghai 200062, China

Contributed by Michael M. Merzenich, August 3, 2007 (received for review June 20, 2007)

Abstract

The spectral, temporal, and intensive selectivity of neurons in the adult primary auditory cortex (A1) is easily degraded in early postnatal life by raising rat pups in the presence of pulsed noise. The nonselective frequency tuning recorded in these rats substantially endures into adulthood. Here we demonstrate that perceptual training applied in these developmentally degraded postcritical-period rats results in the recovery of normal representational fidelity. By using a modified go/no-go training strategy, structured noise-reared rats were trained to identify target auditory stimuli of specific frequency from a set of distractors varying in frequency. Target stimuli changed daily on a random schedule. Consistent with earlier findings, structured noise exposure within the critical period resulted in disrupted tonotopicity within A1 and in degraded frequency-response selectivity for A1 neurons. Tonotopicity and frequency-response selectivity were normalized by perceptual training. Changes induced by training endured without loss for at least 2 months after training cessation. The results further demonstrate the potential utility of perceptual learning as a strategy for normalizing deteriorated auditory representations in older (postcritical-period) children and adults.

Footnotes

^‡To whom correspondence should be addressed. Email: merz{at}phy.ucsf.edu
Author contributions: X.Z. and M.M.M. designed research; X.Z. performed research; X.Z. and M.M.M. analyzed data; and X.Z. and M.M.M. wrote the paper.
The authors declare no conflict of interest.
Abbreviations:

BW20,

bandwidth measured at 20 dB above threshold;

CF,

characteristic frequency;

CON,

naive control;

EXP,

experimental;

NR,

noise-reared;

Pn,

postnatal day n;

PNR,

passively stimulated NR;

SPL,

sound pressure level.
Freely available online through the PNAS open access option.