ACTIVATION OF A WIDE-SPREAD NETWORK OF INHIBITORY NEURONS IN BARREL CORTEX

The one-to-one correspondence of whiskers to barrels in layer IV of ro dent somatosensory cortex can be demonstrated by a precise match betwe en columns of heavy 2-deoxyglucose (2DG) label in layer N barrels and other layers which correspond to stimulated whiskers. While there is s pecificity of peripheral-to-central mapping the extent to which integr ation and/or modulation are generated by circuitry within or interacti ons between the barrel-defined whisker columns is not clear. Following stimulation of selected whiskers, large cells at the layer IV-V bound ary throughout the barrel field are heavily labeled by 2-deoxyglucose (2DG) at high resolution. Many of these cells are outside the barrel c olumns of the stimulated whiskers. Further, the number of cells labele d is not directly related to the number of activated barrel columns. T hese neurons are not labeled in animals anesthetized before 2DG inject ion and are not as heavily labeled in barrel fields of somnolent anima ls. Most of the heavily labeled neurons immunolabel for glutamate deca rboxylase (GAD) and are presumed to be inhibitory, while a smaller num ber of labeled neurons, presumed to be excitatory, immunolabel for glu tamate (Glu). Similar populations of large, heavily 2DG-labeled neuron s are found in other cortical areas. These relatively few neurons are exceptionally active and may modulate integrative functions of cerebra l cortex.