Plasticity in the frequency representation of primary auditory cortex following discrimination training in adult owl monkeys

TLDR

Tonotopic organization of primary auditory cortex can reorganize after cochlear lesions, and cortical reorganization in somatosensory areas correlates with perceptual acuity. Adult owl monkeys were trained over several weeks to discriminate small frequency differences, after which multi‑unit recordings across 70–258 cortical sites mapped tonotopy and were compared to normal and tactile‑control monkeys. Training increased the cortical area, tuning sharpness, and response latency for behaviorally relevant frequencies, and the expanded area was the only parameter correlated with behavioral performance, showing that attention‑driven stimulation alters tonotopic organization and perceptual acuity.

Abstract

Previous studies have shown that the tonotopic organization of primary auditory cortex is altered subsequent to restricted cochlear lesions (Robertson and Irvine, 1989) and that the topographic reorganization of the primary somatosensory cortex is correlated with changes in the perceptual acuity of the animal (Recanzone et al., 1992a-d). Here we report an increase in the cortical area of representation of a restricted frequency range in primary auditory cortex of adult owl monkeys that is correlated with the animal's performance at a frequency discrimination task. Monkeys trained for several weeks to discriminate small differences in the frequency of sequentially presented tonal stimuli revealed a progressive improvement in performance with training. At the end of the training period, the tonotopic organization of Al was defined by recording multiple-unit responses at 70-258 cortical locations. These responses were compared to those derived from three normal monkeys and from two monkeys that received the same auditory stimuli but that were engaged in a tactile discrimination task. The cortical representation, the sharpness of tuning, and the latency of the response were greater for the behaviorally relevant frequencies of trained monkeys when compared to the same frequencies of control monkeys. The cortical area of representation was the only studied parameter that was correlated with behavioral performance. These results demonstrate that attended natural stimulation can modify the tonotopic organization of Al in the adult primate, and that this alteration is correlated with changes in perceptual acuity.