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The left hemisphere and the selection of learned actions
M F Rushworth1, P D Nixon, D T Wade
1Department of Experimental Psychology, University of Oxford, UK. matthew.rushworth@psy.ox.ac.uk
Neuropsychologia
|April 9, 1998
Summary
Left hemisphere (LH) damage impairs response selection, not just movement sequencing. This finding clarifies the basis of left hemisphere dominance for motor control.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Motor Control
Background:
- Left hemisphere (LH) dominance for motor control is established, but its underlying mechanisms remain unclear.
- Previous research identified distributed neural systems crucial for motor and object-oriented response selection.
Purpose of the Study:
- To investigate the specific cognitive deficits associated with left hemisphere damage.
- To determine if LH deficits in motor tasks are due to impaired response selection or other factors like sequencing or kinematics.
Main Methods:
- Tested 16 LH patients, 17 RH patients, and 12 controls on five motor tasks.
- Tasks assessed response selection, sequencing, and object-oriented responses.
- Compared performance on tasks with and without response selection demands.
Main Results:
- LH patients were impaired on tasks requiring response selection, including joystick movements and object-oriented responses.
- LH damage did not impair a task with high memory load but no response selection component.
- Deficits were not attributable to disorganized movement kinematics.
Conclusions:
- Left hemisphere deficits in motor tasks are best explained by impaired response selection, not solely by sequencing issues.
- Distributed systems in the dorsolateral frontal and parietal cortices, striatum, thalamus, and white matter are critical for response selection.