GABAERGIC NEURONS AND THEIR ROLE IN CORTICAL PLASTICITY IN PRIMATES

GABA neurons and GABA receptors are conspicuous elements of cerebral c ortical organization. They serve to shape the stimulus-response proper ties of neurons in the sensory areas and undoubtedly play a comparable role in the nonsensory areas as well. Although non-GABAergic local ci rcuit neurons exist in the cerebral cortex, the variety of forms adopt ed by the GABAergic neurons and their important functional role have s erved to focus attention on the latter in investigations of local cort ical circuitry. In primate neocortex, GABAergic neurons constitute app roximately 25-30% of the neuronal population. In addition to their kno wn or postulated functions in shaping neuronal receptive fields and re sponse profiles, some of which are still controversial (Sillito, 1984; Ferster, 1986), their transmitter, GABA, and the major class of recep tor upon which it acts are regulated in an activity-dependent manner e ven in the adult (Jones, 1990). In this, there is a potential mechanis m for the plasticity of representational maps that is demonstrable in somatic sensory, motor, auditory, and visual cortex (Merzenich et al., 1983; Sanes et al., 1988; Robertson and Irvine, 1989; Kaas et al., 19 90).