Corticospinal circuit neuroplasticity may involve silent synapses: Implications for functional recovery facilitated by neuromodulation after spinal cord injury

IBRO Neuroscience Reports, 2023 · DOI: https://doi.org/10.1016/j.ibneur.2022.08.005 · Published: January 1, 2023

Spinal Cord Injury Neurology Neuroplasticity

Simple Explanation

Spinal cord injury (SCI) disrupts the corticospinal system, leading to sensorimotor dysfunction. However, the CNS exhibits plasticity, enabling recovery. This review explores how neuromodulation can harness beneficial neuroplasticity in spared corticospinal circuits to improve functional outcomes in SCI rehabilitation. Silent synapses, implicated in neurological disorders, might play a role in corticospinal motor circuit neuroplasticity after SCI. The review aims to inform novel therapeutic strategies by exploring the mechanisms of silent synapse-mediated neuroplasticity exploited by neuromodulation. The review focuses on beneficial neuroplasticity induced by electrical stimulation in the corticospinal motor circuitry after SCI. It discusses potential mechanisms mediated by silent synapse regulation, offering a prospective insight into synaptic-level remodeling for SCI therapeutic and rehabilitative research.

Study Duration

Not specified

Participants

Experimental animals and humans

Evidence Level

Review Paper

Key Findings

1
Spinal cord injury (SCI) leads to severe sensorimotor dysfunction by damaging the corticospinal system, but the CNS possesses considerable plasticity that can be harnessed for recovery.
2
Beneficial corticospinal plasticity in spared circuits can be therapeutically harnessed by neuromodulatory approaches, especially electrical stimulation, to improve functional outcomes after SCI.
3
Silent synapse generation and unsilencing contribute to neuroplasticity and may be involved in corticospinal motor circuit neuroplasticity following SCI.

Research Summary

This review explores the potential role of silent synapses in corticospinal motor circuit neuroplasticity following spinal cord injury (SCI) and how neuromodulation can be used to facilitate functional recovery. The review discusses the concept of neuroplasticity, both spontaneous and activity-dependent, occurring in the corticospinal motor circuitry after SCI, and the potential for electrical stimulation-induced neuroplasticity to facilitate functional recovery. The review proposes that silent synapses may play a role in the strengthening of neurotransmission in the intact corticospinal motor circuits in SCI, and that further research is needed to elucidate the temporal and spatial characteristics of spinal silent synapse generation and recruitment after SCI.

Practical Implications

Therapeutic Strategies

Optimizing neuromodulatory therapeutic protocols by understanding the role of silent synapses in SCI.

Rehabilitative Research

Opening a novel avenue for future SCI therapeutic and rehabilitative research by elucidating the mechanisms of silent synapse regulation.

Clinical Translation

Translating benchtop studies into clinical applications for sensorimotor function rehabilitation following SCI.

Study Limitations

1
Lack of direct evidence supporting SCI-induced silent synapse regulation in the corticospinal motor circuitry.
2
The proposed involvement of silent synapses in corticospinal motor circuitry is still a hypothesis and needs to be tested.
3
Underlying mechanisms of ESS are not fully determined.

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