Functional Asymmetries in the Rodent Barrel Cortex

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Abstract
Neurophysiological and 2-deoxyglucose (2DG) studies of the rodent whisker barrel cortex have demonstrated asymmetries in its functional organization. To examine the possibility that the activity gradients observed in metabolic studies can be attributed to subtle rostral-caudal and dorsal-ventral asymmetries in electrophysiologically measured surround or cross-whisker inhibition, we compared 2DG results with predictions generated from quantitative single-cell receptive field data. Despite differences in the two experimental approaches, there is remarkable agreement between the findings. (1) The distribution of 2DG activity declines across the barrel cortex of the behaving animal from anteromedial barrels to posterolateral barrels, and is qualitatively and quantitatively similar to the values predicted from neurophysiology. (2) The strength of surround inhibition in barrel neurons predicts the twofold increase in activation of the C3 barrel following acute clipping of adjacent whiskers. And (3) within a cortical column, the decrease in metabolic activity associated with adjacent whisker stimulation is greatest in layer IV and least in the infragranular layers; this corresponds to the laminar distribution of inhibitory interactions observed electrophysiologically.