Representation of head and face in postcentral gyrus of the macaque

Abstract

The receptive field and submodality characteristics of individual neurons within the cytoarchitectural and topographic subdivisions of the head and face areas of the postcentral gyrus (SI) were determined with the technique of extracellular recording. Correlation of the single-unit data with the intracortical location of the recording electrode provided a detailed description of the functional organization within each of the several cytoarchitecturally distinct regions contributing to the representation of the head and face in SI. The data indicate that the functional organization of the SI cortex which receives its principal input from trigeminal mechanoreceptors is comparable to the organization within those SI regions which receive their input from the mechanoreceptors of the limbs, trunk, and tail. In each topographic subdivision of the SI cortex 1) a single region in the periphery is represented several times in widely separated locations, each time in a context of different submodalities and peripheral receptive fields; and 2) neurons belonging to the different submodality classes are segregated so that projections from cutaneous afferents terminate mainly in cytoarchitectural area 3 in the adjacent anterior portion of area 1, while projections from the afferents innervating deep tissues terminate mainly in cytoarchitectural area 3a, area 2, and the posterior part of each 1. Although the mechanoreceptor input to SI is segregated according to submodality and the mechanoreceptors from most body regions project to multiple widely separated regions within SI, neurons with receptive fields confined to the ophthalmic division of the trigeminal peripheral innervation field are found within a restricted region of the anterior postcentral gyral crown which is positioned symmetrically about the junction of cytoarchitectural areas 1 and 3. Neurons with receptive fields confined to the maxillary division of the trigeminal innervation field are found within a ring of cortex which a) completely surrounds the representation of the ophthalmic field, and b) includes parts of cytoarchitectural area 2, 1, 3, and 3a. SI neurons with receptive fields restricted to the mandibular division of the trigeminal innervation field occupy the largest portion of the SI face area and form a ring of cortical cell columns which completely surrounds that cortical region which receives its input from the maxillary peripheral innervation field.

Ipsilateral Hand Input to Area 3b Revealed by Converging Hemodynamic and Electrophysiological Analyses in Macaque Monkeys

“…In area 3b, the overt hand representation thus far appears to be exclusively contralateral, despite the fact that it can be modulated by stimulation of the ipsilateral hand (Calford and Tweedale, 1990). In this regard, the hand representation in primate area 3b contrasts strongly with that in carnivores (Towe et al, 1964) and rodents (Shin et al, 1997), as well as with the primary cortical representations of the face, oral cavity (Dreyer et al, 1975;Manger et al, 1996;Jain et al, 2001;Disbrow et al, 2003), and midline trunk ) that commonly incorporate and/or cross the midline. These physiological findings mirror known anatomical constraints, because the hand representation in area 3b appears to lack direct thalamic inputs driven by the ipsilateral hand and has few callosal connections (Jones and Hendry, 1980;Killackey et al, 1983).…”

Evocation and characterization of percepts of apparent motion on the face

“…Two widely separated stimuli activate different populations of cortical neurons, and it has been suggested that percepts of apparent motion may arise from higher order central neural mechanisms that are sensitive to the rate at which and to the direction in which the activity shifts across the primary somatosensory cortex in response to their successive delivery (Costanzo & Gardner, 1980;Sherrick & Rogers, 1966). In the present study, it is likely that two stimuli separated by even the maximum separation fell within the RFs of many somatosensory cortical neurons (see Dreyer, Loe, Metz, & Whitsel, 1975). Thus, the central neural basis for percepts ofsmooth apparent motion evoked by the successive activation of two discrete stimuli remains unclear.…”

The Ventral Primary Somatosensory Cortex of the Primate Brain: Innate Neural Interface for Dexterous Orofacial Motor Control

“…In addition, at least in area 3b, such convergence is considered to be rare, because of the presence of the hand-face border. An earlier study of the vSI reported that several neurons in areas 3b or 1 had discrete RFs on both the radial hand and the lateral part of the face [37]. Since those neurons had face RFs that were remote from the oral slit, they are unlikely to relate to feeding behavior.…”