Hemispheric specialization for movement control produces dissociable differences in online corrections after stroke

Area of Science:

• Neuroscience
• Motor Control
• Human Movement Science

Background:

• Motor control exhibits hemispheric specialization, with the right hemisphere (RH) potentially handling online adjustments and the left hemisphere (LH) managing predictive mechanisms.
• Understanding how left hemisphere damage (LHD) and right hemisphere damage (RHD) differentially impact online movement corrections is crucial for rehabilitation strategies.

Purpose of the Study:

• To investigate the distinct effects of LHD and RHD on the ability to correct ongoing movements when task goals change unexpectedly.
• To test the hypothesis that RH is critical for online correction processes, while LH relies more on predictive control.

Main Methods:

• A reaching task was designed where targets unexpectedly shifted mid-movement.
• Participants included 14 stroke survivors (7 LHD, 7 RHD) and 14 healthy controls.
• Movement initiation, correction timing, final position, and intersegmental coordination were analyzed.

Main Results:

• RHD subjects exhibited significant delays in initiating corrective responses compared to controls and LHD subjects.
• Both LHD and RHD groups demonstrated substantial final position errors when targets jumped.
• LHD-related position deficits were linked to impaired intersegmental coordination, whereas RHD deficits involved difficulties in movement termination.

Conclusions:

• RHD specifically impairs the timing of online movement corrections, supporting the RH's role in real-time adjustments.
• Both LHD and RHD lead to position deficits, but through different underlying mechanisms related to hemispheric specialization.
• Further research is required to elucidate the specific neural circuits involved in these distinct hemispheric functions during motor control.