Finger somatotopy is preserved after tetraplegia but deteriorates over time

eLife, 2021 · DOI: https://doi.org/10.7554/eLife.67713 · Published: October 19, 2021

Spinal Cord Injury Neurology Rehabilitation

Simple Explanation

This study investigates how the brain represents the fingers in individuals with tetraplegia, a condition causing loss of motor control and sensation, by using functional MRI to look at brain activity when patients attempt finger movements. The study found that even without sensory feedback or the ability to move their hands, tetraplegic patients could still activate the brain areas corresponding to individual fingers. However, this finger representation in the brain deteriorated over time since the spinal cord injury, suggesting that interventions targeting these representations may be most effective soon after the injury.

Study Duration

Not specified

Participants

14 chronic tetraplegic patients and 18 age-, sex-, and handedness-matched healthy control participants.

Evidence Level

Observational study

Key Findings

1
Somatotopic hand representations can be activated through attempted finger movements in tetraplegic patients even without sensory or motor hand function and no spared spinal tissue bridges.
2
Typical inter-finger representational distance patterns are found in the S1 hand area of tetraplegic patients, indicating preserved hand somatotopy.
3
The typicality of hand somatotopy deteriorates over time since the spinal cord injury, suggesting that these representations are more easily targeted within the first years after SCI.

Research Summary

The study used functional MRI (fMRI) to investigate whether hand somatotopy is preserved in tetraplegic patients following a disconnect between the brain and the periphery. Results indicated that detailed hand somatotopy can be preserved following tetraplegia, even in the absence of sensory and motor hand function and a lack of spared spinal tissue bridges. However, the finger maps deteriorated over time since SCI, suggesting that the hand somatotopy became less typical.

Practical Implications

Rehabilitation Strategies

The preserved S1 finger maps could be exploited in a functionally meaningful manner by rehabilitation approaches that aim to establish new functional connections between the brain and the hand after a tetraplegia.

Neuroprosthetic Limbs

Brain-controlled neuroprosthetic limbs or advanced exoskeletons could leverage the preserved somatotopic representations to restore hand function.

Timing of Intervention

Rehabilitation approaches may be most effective within the first years after SCI, as the hand representation typicality deteriorates over time.

Study Limitations

1
Limited sample size, which may affect the predictive modeling results.
2
The study did not probe body parts other than the hand, so it could not investigate whether remapping of other body part representations may have taken place.
3
The experiment did not allow us to tease apart potential processes, and it is likely that various processes simultaneously influence the preservation of S1 somatotopy and elicited the observed somatotopic S1 activity.

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