Competition between Tool and Hand Motion Impairs Movement Planning in Limb Apraxia.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Motor Control

Background:

• Tool use relies on complex motor planning and resolving action representation competition.
• Incongruent tool-hand motions may exacerbate action competition during planning.

Purpose of the Study:

• To investigate if tool-hand incongruence impairs motor planning in individuals with left hemisphere stroke (LCVA).
• To examine the relationship between apraxia severity and planning deficits with incongruent tools.

Main Methods:

• 34 individuals with chronic LCVA and 16 controls used novel congruent and incongruent tools.
• Apraxia severity was assessed, and lesion-symptom mapping was performed.
• A second experiment assessed gesturing of conventional tools based on incongruence ratings.

Main Results:

• Individuals with LCVA exhibited increased planning time for incongruent tools, correlated with apraxia severity.
• Impairments were most prominent early in the task, especially with novel tools.
• Lesions in posterior temporal and inferior parietal areas were linked to planning deficits for incongruent tools.

Conclusions:

• Tool-hand incongruence triggers action competition, impacting tool-use planning in individuals with apraxia.
• These findings highlight the role of action competition in apraxia and tool use difficulties.