Motor demand-dependent activation of ipsilateral motor cortex.
The role of ipsilateral primary motor cortex (M1) in hand motor control during complex task performance remains controversial. Bilateral M1 activation is inconsistently observed in functional (f)MRI studies of unilateral hand performance. Two factors limit the interpretation of these data. As the motor tasks differ qualitatively in these studies, it is conceivable that M1 contributions differ with the demand on skillfulness. Second, most studies lack the verification of a strictly unilateral execution of the motor task during the acquisition of imaging data. Here, we use fMRI to determine whether ipsilateral M1 activity depends on the demand for precision in a pointing task where precision varied quantitatively while movement trajectories remained equal. Thirteen healthy participants used an MRI-compatible joystick to point to targets of four different sizes in a block design. A clustered acquisition technique allowed simultaneous fMRI/EMG data collection and confirmed that movements were strictly unilateral. Accuracy of performance increased with target size. Overall, the pointing task revealed activation in contralateral and ipsilateral M1, extending into contralateral somatosensory and parietal areas. Target size-dependent activation differences were found in ipsilateral M1 extending into the temporal/parietal junction, where activation increased with increasing demand on accuracy. The results suggest that ipsilateral M1 is active during the execution of a unilateral motor task and that its activity is modulated by the demand on precision.
Department. of Neurology, West Virginia University, Morgantown, West Virginia; Department of Physiology, West Virginia University, Morgantown, West Virginia; Department of Neurology, Emory University, Atlanta, Georgia; Department of Rehabilitation Medicine, Emory University, Atlanta, Georgia; and cathrin.m.buetefisch@emory.edu.
Cathrin M
CM
Buetefisch
Center for Advanced Brain Imaging, Georgia State University/Georgia Institute of Technology, Atlanta, Georgia.
Kate Pirog
KP
Revill
Department of Speech Pathology, West Virginia University, Morgantown, West Virginia;
Linda
L
Shuster
Department. of Neurology, West Virginia University, Morgantown, West Virginia;
Benjamin
B
Hines
Department of Behavioral Medicine, West Virginia University, Morgantown, West Virginia;
Michael
M
Parsons
D000368:Aged; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009048:Motor Skills; D013003:Somatosensory Cortex / Q000502:physiology
fMRI; motor control; motor cortex; motor performance