Functional synergism between putative y-aminobutyrate-containing neurons and pyramidal neurons in prefrontal cortex ( fast spike / monkey / memory / interneurons / vislon )

The responses of putative -aminobutyratergic interneurons (fast-spiking) and pyramidal (regular-spiking) cell pairs were compared in monkeys performing visual and memory-guided oculomotor tasks. Both fastand regularspiking neurons had similar receptive fields, indicating that 'yaminobutyratergic interneurons carry a specific informational signal, as opposed to providing nonspecific modulation. However, the responses of the pairs were inverted and the timing of excitatory and inhibitory responses appeared to be phased, a property consistent with -aminobutyrate-mediated shaping of receptive fields. These observations (i) provide evidence that interneurons and pyramidal cells can be differentiated in vivo and (ii) begin to elucidate the role of y-aminobutyratergic mechanisms in cognition. y-Aminobutyric acid (GABA) is an inhibitory neurotransmitter crucial for the stimulus selectivity of receptive fields in visual and somatosensory cortices (1-3). Infusions of bicuculine, an antagonist of GABA receptors, transform the stimulus selectivity into nonspecific responsiveness, suggesting that GABAergic inhibitory interneurons shape receptive fields. However, the properties of GABAergic interneurons (2) are largely unknown, and this lack ofinformation impedes the analysis of local circuit operations underlying receptivefield properties and therefore sensory, motor, and cognitive function. In vitro intracellular studies have, however, physiologically identified a type of neuron possessing smooth dendrites characteristic of interneurons and possessing the immunohistochemical signature of GABA (4, 5). These fastspiking (FS) interneurons have brief action potentials and high firing rates distinguishable from those of pyramidal (RS) neurons (4-11). The objective of the present study was to determine the functional relationship, if any, between FS and RS neurons recorded in the prefrontal cortex of monkeys performing oculomotor tasks.