A fresh look at propriospinal interneurons plasticity and intraspinal circuits remodeling after spinal cord injury

IBRO Neuroscience Reports, 2023 · DOI: https://doi.org/10.1016/j.ibneur.2023.04.001 · Published: April 3, 2023

Simple Explanation

Spinal cord injury disrupts communication between the brain-derived descending commands and the intraspinal circuits, the central pattern generator (CPG), that execute movements. After SCI, at both brain and spinal cord levels, detour circuits formation and neuronal plasticity have been linked to functional improvement under the condition of spontaneous recovery as well as electrical stimulation- and rehabilitative training-assisted recovery. The current review will focus primarily on the intraspinal mechanism of motor recovery, especially the plasticity of interneurons and circuits after SCI revealed by some recent discoveries.

Study Duration

Not specified

Participants

Rodent and zebrafish SCI models

Evidence Level

Review paper

Key Findings

1
After SCI, the ratio of excitatory to inhibitory interneurons increases, indicating a reorganization of the spinal CPG neural circuit with more pronounced excitatory interneurons than inhibitory interneurons.
2
The reestablished de novo circuit is organized into a modular design with axon-regrown fast and slow V2a interneurons rostral to the lesion, selectively driving caudal fast V2a/motor neurons and slow V2a/motor neurons, respectively
3
A group of V2a interneurons transforming information from brainstem locomotor regions and large-diameter afferents into executive commands was shown to be responsible for the production of walking after EFS with neurorehabilitation

Research Summary

Spinal cord injury (SCI) disrupts communication between the brain and spinal circuits, affecting movement execution. Recovery involves neural circuit remodeling and neuronal plasticity at both brain and spinal cord levels. Intraspinal propriospinal neurons (PSNs) play a crucial role in reconstructing detour circuits after SCI. These interneurons facilitate the re-establishment of functional excitatory circuits necessary for restoring locomotor ability. Re-establishing spinal excitability is key to SCI treatments. Strategies like pharmacological agents and electrical stimulation augment excitation of intact intraspinal neurons, promoting locomotion recovery.

Practical Implications

Targeted Therapies

Future treatments should focus on specific neuron subtypes involved in motor recovery after SCI.

Rehabilitation Strategies

Neurorehabilitation therapies can promote reorganization of cortico-reticulo-spinal circuits post-injury.

Understanding Spinal Circuits

Further investigation into the plasticity of spinal CPGs interneurons is needed to govern motor control after SCI.

Study Limitations

1
Limited regeneration capacity of the central nervous system in adult mammals
2
Current understanding of the organization of reestablished de novo spinal circuits is elusive.
3
Investigation of reconstructed neuronal circuits after SCI in mammals is limited.

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