Neural Basis of Touch and Proprioception in Primate Cortex

Abstract

The sense of proprioception allows us to keep track of our limb posture and movements and the sense of touch provides us with information about objects with which we come into contact. In both senses, mechanoreceptors convert the deformation of tissues-skin, muscles, tendons, ligaments, or joints-into neural signals. Tactile and proprioceptive signals are then relayed by the peripheral nerves to the central nervous system, where they are processed to give rise to percepts of objects and of the state of our body. In this review, we first examine briefly the receptors that mediate touch and proprioception, their associated nerve fibers, and pathways they follow to the cerebral cortex. We then provide an overview of the different cortical areas that process tactile and proprioceptive information. Next, we discuss how various features of objects-their shape, motion, and texture, for example-are encoded in the various cortical fields, and the susceptibility of these neural codes to attention and other forms of higher-order modulation. Finally, we summarize recent efforts to restore the senses of touch and proprioception by electrically stimulating somatosensory cortex. © 2018 American Physiological Society. Compr Physiol 8:1575-1602, 2018.

Postural Representations of the Hand in Primate Sensorimotor Cortex

“…Similar transformations of coordinate frames have revealed parsimonious descriptions of otherwise complex neural response properties in macaque face patches (Chang and Tsao, 2017). A major challenge moving forward is to understand how hand postures are encoded along the somatosensory neuraxis and how these postural representations interact with cutaneous representations of object contacts to give rise to stereognosis (Delhaye et al, 2018;Hsiao, 2008).…”

“…Ultimately, these two streams of information -tactile and proprioceptive -must be integrated. Indeed, local features of the object at each point of contact must be interpreted in terms of the relative positions of the contact points in three dimensional space, to culminate in stereognosis, a three dimensional percept of the object (Delhaye et al, 2018). That individual neurons signal the postures of joints distributed over the entire hand is consistent with a view that the hand representation in SC and M1 emphasizes the configurations of the digits relative to one another, a representation that is ideally suited to support stereognosis.…”

Sensory information from a slipping object elicits a rapid and automatic shoulder response

“…Processing of sensory information from the hand and the upper limb have been largely studied in isolation (Delhaye et al 2018;Scott, 2016); however, the integration of these two sources of information for limb control suggest a confluence of these sensory sources on motor structures. For example, spinal, subcortical (i.e., thalamus), and cortical (i.e., somatosensory cortex) structures are known to receive information from both tactile sensors and muscle spindles (Delhaye et al 2018;Scott, 2016;Kim et al, 2015;Picard and Smith, 1992). Thus, one possibility is that the observed integration might take place in regions that receive both types of information.…”

Functional Organisation and Connectivity of the Dorsal Column Nuclei Complex Reveals a Sensorimotor Integration and Distribution Hub

“…Areas 1 and 2 have larger RFs and complex response properties. For an excellent recent review on these systems in primates see Delhaye, Long, and Bensmaia (2018). Reports vary, but thalamic-projecting neurons appear to make up the largest proportion of DCN neurons in rats, cats, and monkeys (Bermejo et al, 2003;Blomqvist, 1980;Ellis & Rustioni, 1981;Gordon & Seed, 1961;Kemplay & Webster, 1989;Rustioni, Hayes, & O'Neill, 1979;Rustioni, Schmechel, Cheema, & Fitzpatrick, 1984).…”