Emergence of functionally aberrant and subsequent reduction of neuromuscular connectivity and improved motor performance after cervical spinal cord injury in Rhesus

Front. Rehabil. Sci., 2023 · DOI: 10.3389/fresc.2023.1205456 · Published: June 12, 2023

Spinal Cord Injury Neurology Rehabilitation

Simple Explanation

After a spinal cord injury, paralysis during early recovery (around 6 weeks) stems from the inability to properly activate motor pools. Later in recovery, motor task difficulties arise from abnormal activation patterns among motor pools, leading to poor coordination. This study tested this hypothesis by recording EMG activity in Rhesus monkeys before and after a cervical spinal cord injury.

Study Duration

24 weeks

Participants

Four adult male Rhesus monkeys

Evidence Level

Not specified

Key Findings

1
Around 6-8 weeks post-injury, the monkeys began to perform tasks, showing elevated activation of most motor pools beyond pre-lesion levels.
2
As the chronic phase progressed, there was a slight reduction in EMG burst amplitudes and less co-contraction of agonist and antagonist muscles.
3
Even at the initial recovery stages, the activity level of most muscles remained higher than pre-lesion levels.

Research Summary

The study investigates motor performance limitations after partial spinal cord injury, linking them to abnormal coordination among motor pools rather than the inability to recruit them. Neural reorganization of functional connectivity along the sensorimotor axis occurs due to the injury, with elevated activation levels in motor pools. Recovery is continuously dynamic for months post-injury, involving mechanisms such as increased motor unit activation and functional connectivity among interneurons.

Practical Implications

Rehabilitation Strategies

The potential for recovery highlights the importance of rehabilitative strategies that embrace neuroplasticity in the neuromuscular system.

Activity-Dependent Learning

Activity-dependent learning and training can facilitate pruning and selective guidance of network connectivity, leading to better motor pool coordination.

Proprioceptive Input

Ensembles of proprioceptive input to spinal interneurons play a major role in defining activation patterns among motor pools.

Study Limitations

1
The study involved only four subjects.
2
Specific anatomical mechanisms underlying changes in functional connectivity were not identified.
3
The extent to which supraspinal networks contribute to motor recovery remains uncertain.

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