Spectral features control temporal plasticity in auditory cortex

Cortical responses are adjusted and optimized throughout life to meet chang ing behavioral demands and to compensate for peripheral damage. The choline rgic nucleus basalis (NB) gates cortical plasticity and focuses learning on behaviorally meaningful stimuli. By systematically varying the acoustic pa rameters of the sound paired with NB activation, we have previously shown t hat tone frequency and amplitude modulation rate alter the topography and s electivity of frequency tuning in primary auditory cortex. This result sugg ests that network-level rules operate in the cortex to guide reorganization based on specific features of the sensory input associated with NB activit y. This report summarizes recent evidence that temporal response properties of cortical neurons are influenced by the spectral characteristics of soun ds associated with cholinergic modulation. For example, repeated pairing of a spectrally complex (ripple) stimulus decreased the minimum response late ncy for the ripple, but lengthened the minimum latency for tones. Pairing a rapid train of tones with NB activation only increased the maximum followi ng rate of cortical neurons when the carrier frequency of each train was ra ndomly varied. These results suggest that spectral and temporal parameters of acoustic experiences interact to shape spectrotemporal selectivity in th e cortex. Additional experiments with more complex stimuli are needed to cl arify how the cortex learns natural sounds such as speech. Copyright (C) 20 01 S. Karger AG, Basel.