In the somatosensory 'barrel' cortex (where each barrel represents an individual whisker) the receptive fields of cortical spiny neurons show considerable specificity for the direction of whisker displacement, as do the receptive fields of thalamocortical (TC) neurons that provide input to the barrels. In contrast, putative fast-spike inhibitory interneurons in layer 4 of the barrel cortex lack directional preference, but are exquisitely sensitive to low stimulus intensities. Here we show, in adult rabbits, that these sensitive and broadly tuned inhibitory receptive fields are generated by an unselective pooling of convergent functional inputs from topographically aligned TC neurons with very diverse response properties.