Rethinking the Body in the Brain after Spinal Cord Injury

Abstract

Spinal cord injuries (SCI) are disruptive neurological events that severly affect the body leading to the interruption of sensorimotor and autonomic pathways. Recent research highlighted SCI-related alterations extend beyond than the expected network, involving most of the central nervous system and goes far beyond primary sensorimotor cortices. The present perspective offers an alternative, useful way to interpret conflicting findings by focusing on the deafferented and deefferented body as the central object of interest. After an introduction to the main processes involved in reorganization according to SCI, we will focus separately on the body regions of the head, upper limbs, and lower limbs in complete, incomplete, and deafferent SCI participants. On one hand, the imprinting of the body’s spatial organization is entrenched in the brain such that its representation likely lasts for the entire lifetime of patients, independent of the severity of the SCI. However, neural activity is extremely adaptable, even over short time scales, and is modulated by changing conditions or different compensative strategies. Therefore, a better understanding of both aspects is an invaluable clinical resource for rehabilitation and the successful use of modern robotic technologies.

Exoskeletons for Mobility after Spinal Cord Injury: A Personalized Embodied Approach

“…Both clinicians and engineers have recognized the possibility that people with SCIs could reject their bionic legs, because they do not yet feel like biological ones [ 48 , 49 , 80 , 83 ]. However, little attention has been paid to how the human body responds to and supports such technological innovations in terms of active body control and sensing [ 48 , 49 , 80 , 83 , 84 ]. These concerns are particularly relevant for patients with body paralysis and numbness due to SCIs.…”

Spinal Cord Injury and Loss of Cortical Inhibition

“…A physiological process closely tied to disinhibitory mechanisms is the rewiring of cortical circuits after SCI. Like other injuries involving deafferentation of the central nervous system, SCI involves the rewiring of cortical and subcortical areas, as well as the shift of somatotopic representations and changes in competence of motor areas, which relay on significant events of network plasticity [ 124 ]. Decreases in GABAergic inhibition appear crucial for network remodeling [ 125 , 126 ] because plasticity and learning are tightly related to changes in cortical GABA [ 127 ].…”

“…Since disinhibition is integral to plastic rewiring in the central nervous system [ 124 , 125 , 126 ] and supports motor recovery in pathophysiological conditions [ 130 ], it is tempting to hypothesize that therapy after SCI may benefit from actively modulating the balance of excitation and inhibition in cortical and corticospinal networks. Indeed, efforts to improve interventions against SCI have provided encouraging breakthroughs and better understandings of the interconnection between brain plasticity and motor recovery involving the phenomenon of cortical disinhibition.…”

The Role of Body in Brain Plasticity

“…Our bodily experience arises primarily from the integration of sensory, interoceptive, and motor signals and is mapped directly into the sensorimotor cortices [ 1 ]. This view predicts major changes in body representation with changes in sensorimotor experience generated directly by current sensory input and motor control.…”

“…To compensate for sensorimotor loss, central nervous system remodeling may occur in the brain’s white and gray matter by aberrant signaling [ 2 , 3 , 4 ]; progressive atrophic, microstructural, and biochemical changes [ 5 , 6 , 7 , 8 ]; an imbalance in excitation or inhibition [ 9 ], or a spatial shift in functional sensorimotor representation [ 10 ]. Cortical areas become muted when they fail to respond to stimulation, as occurs following brachial plexus and spinal cord damage, or they become maladaptive, as happens with the development of neuropathic pain and phantom sensations such as those associated with amputations [ 1 , 11 , 12 , 13 ]. However, despite this reorganization, the missing limbs remain strongly represented [ 14 , 15 ].…”