Abstract
Primary motor (M1), primary somatosensory (S1) and dorsal premotor (PMd) cortical areas of rhesus monkeys previously have been associated only with sensorimotor control of limb movements. Here we show that a significant number of neurons in these areas also represent body position and orientation in space. Two rhesus monkeys (K and M) used a wheelchair controlled by a brain-machine interface (BMI) to navigate in a room. During this whole-body navigation, the discharge rates of M1, S1, and PMd neurons correlated with the two-dimensional (2D) room position and the direction of the wheelchair and the monkey head. This place cell-like activity was observed in both monkeys, with 44.6% and 33.3% of neurons encoding room position in monkeys K and M, respectively, and the overlapping populations of 41.0% and 16.0% neurons encoding head direction. These observations suggest that primary sensorimotor and premotor cortical areas in primates are likely involved in allocentrically representing body position in space during whole-body navigation, which is an unexpected finding given the classical hierarchical model of cortical processing that attributes functional specialization for spatial processing to the hippocampal formation.
Highlights
Reaching and wheelchair kinematics in egocentric coordinates, M1, S1 and PMd neurons allocentrically represent the monkey’s body location, as well as head and body orientation
A monkey sat in a motorized wheelchair and navigated from one out of three possible starting locations in a room towards the location of a grape dispenser (Fig. 1A). This whole-body navigation was performed under brain-machine interface (BMI) control, where a linear decoding algorithm transformed cortical ensemble activity into translational and rotational velocity components responsible for the wheelchair movements[9]
Two rhesus monkeys employed a BMI to control the movements of a motorized wheelchair in order to navigate to a fixed target location in a room
Summary
Reaching and wheelchair kinematics in egocentric coordinates, M1, S1 and PMd neurons allocentrically represent the monkey’s body location, as well as head and body orientation. Of the neurons with significant mutual information to position or orientation parameters that were used in the GAM analysis, 30.4 ± 17.6% (mean ± std across sessions) in monkey K (S1, M1, and PMd) and 25.7 ± 18.5% in monkey M (S1 and M1) showed significant tuning to both parameters (see Table S2–3).
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