Receptive field size for certain neurons in primary somatosensory cortex is determined by GABA-mediated intracortical inhibition

Multibarrel micropipette assemblies with a carbon fiber-containing central barrel were used to examine the receptive fields of single neurons from areas 3a and 3b of the cat's somatosensory cortex. Microiontophoretic ejection of bicuculline methiodide from one or more of the other barrels altered the responses evoked by natural cutaneous stimulation. This drug produced an enlargement of the receptive field areas of 14 of 18 cells situated in regions expressing rapidly adapting submodality backgrounds. However, this action of the GABA antagonist was noted only in 4 of 18 cells located within cortical regions characterized by slowly adapting or deep backgrounds. Glutamate and GABA did not alter receptive field size, although these amino acids did change the threshold and magnitude of the response to tactile stimulation. No change in modality or submodality properties of any neuron was observed with any of the compounds tested.