Abstract

Previous studies showed reorganised and/or altered activity in the primary sensorimotor cortex after a spinal cord injury (SCI), suggested to reflect abnormal processing. However, little is known about whether somatotopically specific representations can be activated despite reduced or absent afferent hand inputs. In this observational study, we used functional MRI and a (attempted) finger movement task in tetraplegic patients to characterise the somatotopic hand layout in primary somatosensory cortex. We further used structural MRI to assess spared spinal tissue bridges. We found that somatotopic hand representations can be activated through attempted finger movements in the absence of sensory and motor hand functioning, and no spared spinal tissue bridges. Such preserved hand somatotopy could be exploited by rehabilitation approaches that aim to establish new hand-brain functional connections after SCI (e.g. neuroprosthetics). However, over years since SCI the hand representation somatotopy deteriorated, suggesting that somatotopic hand representations are more easily targeted within the first years after SCI.

Highlights

  • A spinal cord injury (SCI) refers to damage of the spinal cord caused by a trauma, disease, or degeneration of vertebral discs

  • We investigated what clinical and behavioural determinants may contribute to preserving S1 hand somatotopy after chronic SCI

  • In this study we investigated whether hand somatotopy is preserved and can be activated through attempted movements following tetraplegia

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Summary

Introduction

A spinal cord injury (SCI) refers to damage of the spinal cord caused by a trauma, disease, or degeneration of vertebral discs. Research in non-human primate models of chronic and complete cervical SCI has shown that the S1 hand area becomes largely unresponsive to tactile hand stimulation after the injury (Jain et al, 2008; Kambi et al, 2014; Liao et al, 2021). The physiological hand representation appears to largely be altered following a chronic cervical SCI in non-human primates, the anatomical isomorphs of individual fingers are unchanged (Jain et al, 1998) This suggests that while a hand representation can no longer be activated through tactile stimulation after the loss of afferent spinal pathways, a latent and somatotopic hand representation could be preserved regardless of large-scale physiological reorganisation

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