Phylogenetic view of the compensatory mechanisms in motor and sensory systems after neuronal injury

Current Research in Neurobiology, 2022 · DOI: https://doi.org/10.1016/j.crneur.2022.100058 · Published: October 17, 2022

Neurology

Simple Explanation

This review discusses how ancient neural circuits can take over the function of newer, damaged circuits to enable some functional recovery. However, the recovery is limited by the capacity of the ancient circuits. The first example explored is the recovery of hand movements after damage to the corticospinal tract, where other motor pathways compensate, but recovery depends on the location of damage. The second example is visual function recovery after V1 damage, where alternative pathways take over, but visual awareness is altered, reflecting the compensatory pathways' limited capacity.

Study Duration

Not specified

Participants

Nonhuman primate models (Macaques)

Evidence Level

Review

Key Findings

1
After corticospinal tract lesions at C4-C5, propriospinal neurons contribute to the recovery of fractionated finger movements.
2
The SC-pulvinar pathway contributes to the recovery of visually guided saccades after V1 lesions.
3
Visual awareness is impaired but not completely lost in monkeys with unilateral V1 lesions, similar to human blindsight.

Research Summary

This review examines functional compensation following neural injury, focusing on motor and visual systems in nonhuman primates. After injury to novel neural systems, phylogenetically older systems can compensate for their functions through rehabilitative training, though the recovered functions are not identical to the intact state. The double viral vector-intersectional manipulation method is a powerful tool to uncover compensatory circuits.

Practical Implications

Neuromodulatory Therapies

Identifying compensatory circuits can inform the application of transcranial magnetic stimulation or transcranial direct current stimulation to facilitate their activity.

Realistic Treatment Goals

Understanding the limitations of compensatory circuits can help set realistic goals for treatment and rehabilitation.

Combination Therapies

Combining regenerative/neuromodulatory therapies with rehabilitative training can enhance functional restoration after neural injury.

Study Limitations

1
The transfection efficiency of viral vectors for pathway-selective manipulation techniques is still not very high and needs to be improved.
2
Effects of pathway-selective perturbation might be difficult to be interpreted if the target pathway includes some fibers which were spared from blockade or if there exist parallel indirect pathways.
3
Closer investigation of behavioral and physiological parameters revealed that the recovered sensorimotor and cognitive functions are not the same as in the intact state.

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