Distributions of single neurons related to body parts in the lateral striatum of the rat.

Single unit recordings in awake, unrestrained rats confirmed and extended previous findings regarding the functional organization of the lateral striatum. In individual electrode tracks, clusters of neurons related functionally to an individual body part were interspersed with clusters related to other body parts. The overlapping distributions of these neurons were arranged somatotopically in the dorsal-ventral dimension. The distribution of hind limb neurons was most dorsal and showed no overlap with the distribution of neurons related to oral sensorimotor activity. Oral representation was most ventral of all body parts and extended to the ventral boundary of the lateral striatum. Representations of other body parts overlapped with that of the hind limb dorsally but differed primarily in the degree to which they extended ventrally. Forelimb representation extended farther ventrally than that of the hind limb, but did not extend as far ventrally as that of the neck. Despite substantial overlap in the dorsal-to-ventral order of hind limb-forelimb-neck-face representations, single neurons showed no evidence of overlap, or convergence, of body parts. These data provide a more complete description of the dorsal-ventral somatotopy in the lateral striatum of the rat, which as shown previously, extends throughout the medial-lateral, and much of the anterior-posterior dimensions of the lateral striatum.