Disentangling motor execution from motor imagery with the phantom limb

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Human Motor Control

Background:

• Phantom limb movements in amputees are typically viewed as motor imagery, not execution.
• Amputees report distinct perceptions for executed versus imagined phantom limb movements.
• Behavioral differences exist: executed movements involve stump contractions and slower speeds than imagined movements.

Purpose of the Study:

• To investigate the distinct cerebral networks underlying executed and imagined phantom limb movements.
• To provide neuroimaging evidence for the dual ability of phantom limb movement.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to examine brain activity.
• Dynamic causal modelling (DCM) analyzed changes in functional connectivity.
• 14 upper-limb amputees performed imagined and executed movements of their intact and phantom hands.

Main Results:

• Distinct, partially overlapping cerebral networks were activated for executed and imagined phantom limb movements.
• Execution showed greater activity in primary somatosensory cortex, primary motor cortex, and anterior cerebellum.
• Imagination showed greater activity in parietal/occipital lobes and posterior cerebellum; opposite effects on SMA-M1 network.

Conclusions:

• Phantom limb movements activate neurophysiological networks similar to executed movements of intact limbs, distinct from imagination networks.
• The dual capacity for execution and imagination of phantom limb movements involves separate cortical networks.
• Understanding these distinct networks is vital for developing effective phantom limb pain rehabilitation programs.