Changes in the cortical map of the hand following postnatal median nerve injury in monkeys: modification of somatotopic aggregates

Abstract

Median nerves to the hands of 8-15-d-old marmoset monkeys were transected and precluded from regeneration by ligation. Following periods of 0.4-1.5 years, features of organization in the cortical area 3b hand map were assessed neurophysiologically, and compared to features in normally reared monkeys. Cortical features in monkeys with both histories were similar in certain respects. (1) Receptive field organization was similar in terms of tactile thresholds and receptive field size, continuity, and glabrous-hairy specificity. (2) Somatotopic organization was similar in terms of the continuity of the glabrous representation, and progressions of receptive field shifts across some parts of the hand map. (3) Finally, the overall size of the hand map did not change. In contrast, other cortical features clearly differed following these developmental histories. (1) Neurons at virtually all recording sites in normal hand maps responded to light mechanical stimulation, whereas, following injury, neurons at about 8% of the recording sites responded only to high-intensity stimuli. (2) Somatotopic organization differed in terms of the presence or absence of the representation of skin autonomously innervated by the median nerve, the number and continuity of representations of hairy skin, and the spatial interfacing of representations. (3) Finally, there were differences in the areas and widths of representations of parts of the hand. The overall impression is that there is a correspondence between the cortical features that changed most after injury, and the features that varied most in individual normal monkeys: in both circumstances the most variable features involved properties of spatial patterning across large aggregates of neurons as reflected by the size, shape, continuity, and interfacing of representations. A hypothesis is proposed that suggests that the cortical hand map normally consists of a number of representations that are capable of developing and surviving somewhat autonomously of each other. The features of spatial patterning in the mosaiclike map of these representations are influenced by postnatal availability of inputs from intact hand nerves.

The effects of neonatal median nerve injury on the responsiveness of Tactile neurones within the cuneate nucleus of the cat

“…This form of reorganization, in which there is an expansion in the central representation of body regions around the zone of deafferentation into areas of the central map that previously represented the deafferented body part, has been reported in response to nerve injury or local anaesthetic‐induced deafferentation at each level of the dorsal column–lemniscal pathway, including the dorsal column nuclei, thalamus and cortex (e.g. Dostrovsky et al 1976; Merzenich et al 1983; Calford & Tweedale, 1988, 1990; Wall et al 1992; Nicolelis et al 1993; Pettit & Schwark, 1993). It has also been reported in several studies on the spinal dorsal horn (e.g.…”

“…However, the clinical assessments are often based on simple detection tasks and may not reveal more subtle discriminative disturbances that reflect impaired transmission and signalling, and which might result either from the incomplete anatomical regeneration of the peripheral nerve, or from some form of functional reorganization or ‘plasticity’ within the central pathways that has been reported to follow partial deafferentation brought about by nerve injury or local anaesthetic blockade (e.g. Dostrovsky, Millar & Wall, 1976; Lisney, 1983; Merzenich, Kaas, Wall, Nelson & Sur, 1983; Calford & Tweedale, 1988, 1990; Wall, Huerta & Kaas, 1992; Nicolelis, Lin, Woodward & Chapin, 1993; Pettit & Schwark, 1993; Koerber & Brown, 1995). The reorganization described involves an alteration in body maps at the levels of the dorsal horn, the dorsal column nuclei, thalamus and cortex, in which there is an expansion in the central representation of body regions around the zone of deafferentation into areas of the map that previously represented the deafferented body part.…”

Extensive Divergence and Convergence in the Thalamocortical Projection to Monkey Somatosensory Cortex

“…The detailed somatotopic representation demonstrable physiologically in the primate somatosensory cortex (Powell and Mountcastle, 1959;Werner and Whitsel, 1968;Nelson et al, 1980) is subject to activity-dependent expansions and contractions that can occur under the influence of behavioral or surgical manipulations of peripheral input C lark et al, 1988;Jenkins et al, 1990;Recanzone et al, 1992;Wall et al, 1992;Florence et al, 1994). The rapidity with which changes occur implies a considerable degree of divergence of preexisting thalamocortical and, potentially, of ascending brainstem connections.…”

Errors of somatosensory localisation in a patient with right-hemisphere stroke

“…Examples in which deafferentation leads to a change in the brain's representation of the body include amputation (Elbert et al, 1994;Merzenich et al, 1984;Ramachandran et al, 1992), nerve injury (Braune & Schady, 1993;Wall, Huerta, & Kaas, 1992) and local anaesthesia (Björkman, Weibull, Rosén, Svensson, & Lundborg, 2009;Kew et al, 1994;Waberski, Gobbelé, Kawohl, Cordes, & Buchner, 2003). Note that cortical changes associated with local anaesthesia may be immediate.…”