Movement-dependent electrical stimulation for volitional strengthening of cortical connections in behaving monkeys

PNAS, 2022 · DOI: https://doi.org/10.1073/pnas.2116321119 · Published: June 27, 2022

Neurology Neuroplasticity Rehabilitation

Simple Explanation

This study explores how combining voluntary movements with electrical stimulation can strengthen connections in the brain's motor cortex of monkeys. The researchers found that movement-gated stimulation, followed by repetition of those movements, led to substantial gains in the strength of cortical connections. This suggests that behavior plays a crucial role in brain plasticity and supports combining movement-gated stimulation with physical rehabilitation to strengthen weakened connections after injuries.

Study Duration

2 weeks of behavioral sessions after conditioning

Participants

Two adult male Macaca nemestrina monkeys

Evidence Level

Not specified

Key Findings

1
Movement-gated stimulation combined with postconditioning behavior produces further strengthening of cortical connections.
2
Conditioning alone or behavior alone is ineffective in modulating cortical connectivity.
3
Cortical strengthening produced by combining conditioning and behavior is direction specific.

Research Summary

The study investigated the effect of movement-dependent electrical stimulation on strengthening cortical connections in behaving monkeys. Movement-gated stimulation, paired with further repetition of the movements, resulted in significant increases in the strength of cortical connections, in a use-dependent manner. The findings suggest a critical role for behavior in cortical plasticity and provide support for combining movement-gated stimulation with use-dependent rehabilitation for strengthening connections weakened by injury or disease.

Practical Implications

Rehabilitation Strategies

Combining movement-gated stimulation with use-dependent physical therapies could enhance motor recovery after stroke or spinal cord injury.

Clinical Applicability

The study suggests that the stimulation protocol, which uses a noninvasive gating signal (movement), could be clinically applicable using less-invasive surface electrodes or superficial scalp electrodes for delivery of conditioning stimulation.

Future Research

Augmenting motivation through electrical stimulation of dopaminergic neurons in the nucleus accumbens or the ventral midbrain may further enhance motor recovery promoted by movement-gated stimulation and physical rehabilitation.

Study Limitations

1
The study only investigated plasticity propagation in outgoing connections from the presynaptic and postsynaptic sites.
2
Experimental time constraints precluded measurement of changes in incoming connections to the presynaptic and postsynaptic sites or secondary connections.
3
The population of cortical cells contributing to the measured variable (i.e., EP amplitude) is unknown.

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