Does Ipsilateral Remapping Following Hand Loss Impact Motor Control of the Intact Hand?

Area of Science:

• Neuroscience
• Neuroplasticity
• Human motor control

Background:

• Cortical territories can become functionally redundant after limb loss.
• Previous research indicated differing brain activity patterns in amputees versus individuals with congenital limb differences (one-handers).
• The functional significance of observed brain remapping in amputees remains unclear.

Purpose of the Study:

• To investigate brain function and behavior in the remaining hand of individuals with a missing hand (congenital or amputation).
• To explore if neural resource recruitment in the missing hand's territory supports motor control demands in amputees.
• To compare brain activity and structural connectivity between amputees, one-handers, and controls during a complex motor task.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to analyze brain activity during a complex finger task.
• Both univariate and multivariate fMRI analyses were employed to assess brain representation and activity.
• White matter tractography was conducted to evaluate structural connectivity between hand representation areas.

Main Results:

• Amputees exhibited increased ipsilateral (missing hand territory) activity with higher motor demand, but without behavioral task improvement.
• Multivariate fMRI revealed stronger, more typical contralateral hand representation in amputees compared to one-handers, suggesting collaborative processing.
• No significant differences in univariate or multivariate brain activity were found in one-handers compared to controls, despite learning difficulties.

Conclusions:

• Enhanced brain activity in the missing hand territory post-amputation may not directly reflect improved intact hand function.
• Neuroplasticity appears more restricted than previously assumed and might be influenced by early-life pathway availability.
• Structural connectivity between hand areas does not differ across groups, indicating that functional remapping, not structural change, is key.