Abstract
There is evidence that the left hemisphere is more competent for motor control than the right hemisphere. This study investigated whether this hemispheric asymmetry is expressed in the latency/duration of sequential responses performed by the left and/or right hands. Thirty-two right-handed young adults (16 males, 16 females; 18-25 years old) were tested in a simple or choice reaction time task. They responded to a left and/or right visual target by moving their left and/or right middle fingers between two keys on each side of the midline. Right hand reaction time did not differ from left hand reaction time. Submovement times were longer for the right hand than the left hand when the response was bilateral. Pause times were shorter for the right hand than the left hand, both when the responses were unilateral or bilateral. Reaction time results indicate that the putatively more efficient response preparation by the left hemisphere motor mechanisms is not expressed behaviorally. Submovement time and pause time results indicate that the putatively more efficient response execution by the left hemisphere motor mechanisms is expressed behaviorally. In the case of the submovements, the less efficient motor control of the left hand would be compensated by a more intense attention to this hand.
Highlights
Cortical and subcortical motor areas in the left hemisphere differ both structurally and functionally from those in the right hemisphere, in right-handed individuals, which comprise about 90% of the population
For the simple task, the left hand and the right hand reaction times were shorter for the bilateral mode than for the unilateral mode (P=0.004 and P=0.001, respectively) and that for the choice task the left hand and the right hand reaction times were longer for the bilateral mode than for the unilateral mode (P=0.016 and P,0.001, respectively)
This study was conducted to investigate whether the dominance of the left hemisphere for motor control in right-handed individuals, indicated by anatomical [1,2], physiological [4,5,6,7,8], and clinical [9,10,11] evidence, is matched by consistent faster right hand responses in reaction time tasks
Summary
Cortical and subcortical motor areas in the left hemisphere differ both structurally and functionally from those in the right hemisphere, in right-handed individuals, which comprise about 90% of the population. In addition to impairing movement sequencing, lesions involving the left but not right areas (lateral premotor cortex, parietal cortex, thalamus, striatum, and white matter fascicles) were shown to impair response selection in a variety of tasks [11]. These findings have been interpreted as indicating that the left hemisphere motor mechanisms of right-handers play a dominant role in response selection [11], and in the programming and initial execution of responses with sequencing requirements [9,10]
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