Intracortical and interhemispheric excitability changes in arm amputees: A TMS study
Gabriella Musumeci1, Marco D'Alonzo2, Federico Ranieri3
1Research Unit of Neurology, Department of Medicine and Surgery, Università Campus Bio-Medico di Roma, Via Alvaro del Portillo, 21, 00128 Roma, Italy; NeXT: Neurophysiology and Neuroengineering of Human-Technology Interaction Research Unit, Campus Bio-Medico University of Rome, via Alvaro del Portillo, 5, Rome 00128, Italy.
Trans-radial amputees show increased motor cortex excitability in the affected arm hemisphere, with preserved intracortical inhibition. This contrasts with trans-humeral amputees, highlighting differences in brain reorganization after limb loss.
Area of Science:
- Neuroscience
- Motor Cortex Plasticity
- Rehabilitation Science
Background:
- Upper limb amputation leads to significant neuroplastic changes in the motor cortex.
- Understanding these changes is crucial for optimizing prosthetic rehabilitation strategies.
Purpose of the Study:
- To investigate motor cortex excitability and intracortical circuits in upper limb amputees.
- To compare the affected arm (AH) and unaffected arm (UH) hemispheres.
Main Methods:
- Recorded motor evoked potentials (MEP) in 17 upper limb amputees (11 trans-radial, 6 trans-humeral).
- Evaluated motor thresholds (MT), short interval intracortical inhibition (SICI), and interhemispheric inhibition (IHI).
Main Results:
- Trans-radial amputees exhibited higher MEP amplitudes in the AH compared to the UH.
- Short interval intracortical inhibition (SICI) was preserved in the trans-radial group but not in the trans-humeral group.
- No significant difference in motor thresholds (MT) was found between hemispheres.
Conclusions:
- Trans-radial amputees demonstrate increased corticospinal excitability in the affected arm hemisphere with preserved intracortical inhibition.
- These neuroplastic changes were not observed in the trans-humeral amputee population.
- Findings suggest differential cortical reorganization based on amputation level.
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