Visual and somatosensory integration in the anterior ectosylvian cortex of the cat

We recorded from single neurons in both banks of the posterior two-thirds of the anterior ectosylvian sulcus. All neurons were tested with visual and tactile stimulations. In each bank of the anterior ectosylvian sulcus the majority of neurons were bimodal, i.e. responded to both visual and tactile stimuli (B cells); the remaining population was strictly unimodal, responding either to visual (V cells) or to somatosensory (T cells) stimulation. Bimodal and unimodal neurons were recorded at all explored cortical sites and were consistently intermixed. Unlike bimodal neurons, unimodal neurons showed an asymmetric localization: the V cells were significantly more numerous in the ventral bank while the T neurons were preferentially found in the dorsal bank of the sulcus. We could not detect an orderly somatotopic or visuotopic representation, nor was it possible to find a systematic spatial correspondence between somatic and visual receptive fields. The functional organization of the anterior ectosylvian cortex is discussed in terms of a hierarchical processing of sensory information.