Functional organization of receptive fields in the cat somatosensory cortex. II: Second representation of the forepaw in the ansate region.

The receptive fields (RF) of the neurons in the ansate region of the first somatosensory cortex (SI) were studied in unanesthetized paralyzed cats. Along the ansate sulcus, the forepaw dorsum was represented laterally, and the ventral surface of the paw was represented medially. These representations of the distal forepaw were found to be different from those in the coronal region in that they take parts of the larger and elongated receptive fields along the forearm axis. The principle of multiple representation of the forepaw on SI proposed in the preceding paper was thus confirmed and extended in this study. Many units in the ansate region showed complex receptive characteristics different from those in the coronal region. The convergence of skin and deep submodality was observed in units recorded in area 2 in the deep fold along the ansate sulcus, border zone along area 5. The functional organization of SI in terms of its cytoarchitectonic differentiation and thalamocortical relationships was discussed.