Second somatic sensory cortical area (sii) in a prosimian primate, galago crassicaudatus

Abstract

The cortex adjacent to and along the upper bank of the lateral sulcus (UB-LS) of a prosimian primate, Galago crassicaudatus, was explored to determine the topographical representation of low-threshold cutaneous inputs to this region. The somatic sensory projections to this cortex were considered homologous to those defined in other species as the second somatosensory cortical area (SII). Multiple and single neuron recordings were obtained with tungsten microelectrodes in animals anesthetized with sodium pentobarbital or ketamine hydrochloride; receptive fields were determined by means of manually applied tactile stimuli. The area of SII was located approximately 1-1.5 mm rostral to the posterior limit of LS, extended rostrally approximately 4 mm, and occupied nearly all of the upper bank of the sulcus throughout this region. Receptive fields (RFs) in SII were primarily contralateral except for some bilateral input in the cortex representing portions of the trunk, head, and face. The boundaries of RFs were well defined, especially where recordings were located in the middle layers of the cortex. The distribution of RFs across SII was somatotopically organized into a single, relatively erect representation of the body that involved inputs from the face rostral and medial (superficially along the UB-LS) surrounding an enlarged forelimb area; the latter, in turn, lies rostral and medial to the hindlimb zone. Projections from the tail and sacrum are located furthest caudal and lateral (deeper along UB-LS). Separate regions that were devoted to the glabrous skin surfaces of the distal limbs formed the rostral and lateral boundaries of the distal fore- and hindlimb representations, respectively. In the zone for the glabrous surfaces of the forelimb digits, individual digits dominated discrete components of the SII map, especially medially where digit 1 was represented. The glabrous tip of digit 5 was represented caudal and lateral to the tip of digit 1. A similar radial to ulnar medial to lateral sequence was noted in the area representing the palm. Except for a possible medially located toe 1 zone in the hindlimb representation, separated representations for the glabrous skin of individual toes were not noted. The dorsal hairy surfaces of the digits and toes were, respectively, amalgamated within the representations for the dorsal surfaces of the hand and foot. In these regions, which were found superficial and slightly caudal to their respective glabrous zones, some RFs were found that were devoted only to the distal extremities, but most RFs included more proximal portions of the hand or foot dorsum.(ABSTRACT TRUNCATED AT 400 WORDS)

Bilateral Plasticity of Vibrissae SII Representation Induced by Classical Conditioning in Mice

“…In mice, the localization of SII was discovered by Woolsey (1967) and the area was mapped by Carvell and Simons (1987). SII contains the entire body representation in a somatotopic map, but receptive fields are larger than in primary somatosensory area (Burton and Carlson, 1986;Carvell and Simons, 1987). It is reciprocally connected with the ipsilateral somatosensory (SI) and motor cortex (Carvell and Simons, 1987;Miyashita et al, 1994), ventral posterolateral (VPL), ventral posteromedial (VPM), and posterior (PO) nucleus of the thalamus (Burton and Kopf, 1984;Theyel et al, 2010), and the prefrontal cortex (Kostopoulos et al, 2007).…”

Parallel Processing of Nociceptive and Non-nociceptive Somatosensory Information in the Human Primary and Secondary Somatosensory Cortices: Evidence from Dynamic Causal Modeling of Functional Magnetic Resonance Imaging Data

“…There is compelling anatomical evidence from primates that S1 and S2 are reciprocally connected through extensive corticocortical projection neurons arising from superficial layers (I-III) (Friedman et al, 1980;Burton and Carlson, 1986;Pons and Kaas, 1986;Kandel et al, 2010). Importantly, both S1 and S2 receive direct projections from multiple thalamic nuclei such as the ventral posterior nucleus (VP) (including ventral posterior lateral and ventral posterior medial nuclei), the ventral posterior inferior nucleus (VPI), and the centrolateral nucleus (CL) (Jones and Leavitt, 1974;Burton and Jones, 1976;Friedman and Murray, 1986;Krubitzer and Kaas, 1992;Jones, 1998).…”

Tactile discrimination capacity in relation to size and organization of somatic sensory cortex in primates: I. Old-World prosimian, Galago; II. New-World anthropoids, Saimiri and Cebus

“…In the Asian prosimian Nycticebus, we reported a minor second glabrous projection within the major projection of the hairy hand to area 1 . Our subsequent studies of secondary somatic sensory cortex (SII) in Galago demonstrated a single hand and body projection pattern (Burton and Carlson, 1986) with features similar to the single area defined in SII of Macaca (Robinson and Burton, 1980). Like Macaca, the NW anthropoids Aotus (Merzenich et al, 1978), Cebus (Fellernan et al, 1983) and Saimiri (Sur et al, 1982) have separate projections from glabrous hand and other body surfaces in areas 3b and 1 (Fig.…”

“…Eight adult Galago garnetti served as subjects in these studies (Table 1). This is the same species used in our previous studies of SI and SII and referred to as G&go crassicaudutus (Carlson and Welt, 1980;Burton and Carlson, 1986). The species designation of the greater Galago has changed over the past decade.…”

“…Surgical and recording procedures were as described in Carlson and Welt (1980) and Burton and Carlson (1986). All procedures were performed under surgical levels of anesthesia.…”