The representation of the body surface in S-I of cats.
In both cats and monkeys, the traditional region of the first somatosensory area of cortex, S-I, has been described as containing four strip-like architectonic fields, areas 3a, 3b, 1, and 2. In monkeys, a number of recent studies have provided evidence that each of these architectonic fields constitutes a separate representation of the body. Because of the observations in monkeys, we decided to re-examine the S-I region of cats to determine whether the evidence supported the traditional concept of a single representation, or the existence of several representations related to the described architectonic fields. Microelectrode multiunit mapping techniques were used to determine the somatotopic organization of the S-I region of 10 cats. The results indicate that a single representation of the body surface occupies most or all of the traditional S-I region including cortex defined as area "3b," area "1," and much of area "2," but excluding area "3a." Neurons throughout this single representation were activated by cutaneous stimuli, indicating that all parts of S-I receive input from cutaneous receptors. Neurons in area 3a were activated by inputs from deep receptors, as reported by others. Neurons caudal to S-I were activated by cutaneous stimuli and appeared to constitute the additional body surface representations of S-II and possibly S-III. Thus, the significance of the architectonic fields "3b," "1," and "2" is quite different in cats than in monkeys. We propose that most or all of these three fields, as described in cats, constitute the homologue of area 3b in monkeys.
D000818:Animals; D001931:Brain Mapping; D002415:Cats / Q000033:anatomy & histology*; D005121:Extremities; D005260:Female; D005528:Foot; D005552:Forelimb; D006614:Hindlimb; D008297:Male; D013003:Somatosensory Cortex / Q000033:anatomy & histology*; D014110:Touch