Learning to promote recovery after spinal cord injury

Exp Neurol, 2020 · DOI: 10.1016/j.expneurol.2020.113334 · Published: August 1, 2020

Spinal Cord Injury Neuroplasticity Neurorehabilitation

Simple Explanation

This article discusses how the principles of learning can be applied to neurorehabilitation after spinal cord injury (SCI). It challenges the traditional view that the adult spinal cord is hardwired and incapable of learning, presenting evidence that neurons within the spinal cord can support learning even after communication with the brain has been disrupted. The article highlights that noxious stimulation can sensitize circuits within the spinal cord, similar to brain-dependent learning and memory. However, after a spinal contusion injury, pain input can worsen the injury and hinder long-term recovery. Conversely, exposure to rhythmic stimulation, treadmill training, and cycling can enhance the expression of brain-derived neurotrophic factor (BDNF) and reduce nociceptive sensitization. Pairing epidural stimulation with activation of motor pathways also promotes recovery after SCI. The authors suggest that a neurofunctionalist approach, which focuses on how specific stimuli and training methods impact spinal function, can be used to develop strategies that promote recovery after SCI.

Study Duration

Not specified

Participants

Rats

Evidence Level

Review

Key Findings

1
Spinal cord injury enables plasticity by down-regulating the Cl− co-transporter KCC2, which reduces GABAergic inhibition, enabling learning but also fueling over-excitation and nociceptive sensitization.
2
Noxious stimulation after spinal cord injury induces sensitization, fosters hemorrhage, and impairs recovery, whereas controllable or predictable stimulation increases BDNF and promotes adaptive plasticity.
3
Neurorehabilitative strategies that involve relational learning, such as pairing epidural stimulation with cortical stimulation or establishing instrumental relations between muscle activity and spinal stimulation, have a lasting effect.

Research Summary

The review explores the concept of learning within the context of neurorehabilitation after spinal cord injury (SCI), challenging the traditional view of the spinal cord as hardwired and immutable. Research shows that noxious stimulation can sensitize nociceptive circuits within the spinal cord, engaging pathways similar to those in brain-dependent learning, but can also undermine recovery after spinal contusion injury. Conversely, rhythmic stimulation, treadmill training, and cycling enhance BDNF expression and counter nociceptive sensitization. Pairing epidural stimulation with motor pathway activation promotes recovery. The authors advocate for a neurofunctionalist approach to discover and harness processes that foster recovery after SCI.

Practical Implications

Targeting GABAergic Inhibition

Treatments that re-establish GABAergic inhibition could have therapeutic value for reducing chronic pain and spasticity after SCI.

Protecting Against Noxious Input

Attenuating pain soon after injury, possibly through local anesthetics like lidocaine, could improve patient wellbeing and long-term recovery by blocking nociception-induced tissue loss.

Employing Relational Learning

Neurorehabilitation strategies should incorporate relational learning principles, such as pairing stimulation with motor activity, to enhance and prolong treatment effects.

Study Limitations

1
The review primarily focuses on animal studies, particularly rats, which may not fully translate to human physiology and clinical outcomes.
2
The review acknowledges that spinal learning is limited compared to brain-dependent learning, especially in terms of flexibility and complexity.
3
The effectiveness of various interventions, such as BDNF treatment, depends on the stage of injury and the specific circumstances, requiring a nuanced approach.

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