Interhemispheric transfer of post-amputation cortical plasticity within the human somatosensory cortex

Area of Science:

• Neuroscience
• Neuroplasticity
• Somatosensory Cortex Research

Background:

• Deafferenting injuries in animal models show somatosensory cortex reorganization.
• The extent and functional impact of this reorganization in humans remain unclear.
• Previous research has not established if cortical changes occur in human amputees.

Purpose of the Study:

• To investigate sensory cortical reorganization in chronic upper extremity amputees.
• To map the sensory representation of the intact hand and lower face using functional magnetic resonance imaging (fMRI).
• To compare cortical activity between amputees and healthy controls.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to map cortical representations.
• Participants included 19 chronic unilateral upper extremity amputees and 29 healthy controls.
• Cutaneous stimulation of the intact hand and lower face was delivered during fMRI.

Main Results:

• Amputees showed increased activity in the deafferented former sensory hand territory (S1f) when their intact hand was stimulated.
• This heightened S1f activity was specific to somatosensory stimulation, not visual.
• No differences in tactile acuity were found between amputees and controls, and S1f responses did not correlate with pain or prosthesis use.

Conclusions:

• The former sensory hand territory (S1f) in human amputees becomes responsive to stimulation of the intact hand.
• This modality-specific cortical reorganization persists for many years post-amputation.
• The functional significance of this long-lasting neural change remains to be determined.