Functional MRI cerebral activation and deactivation during finger movement.
OBJECTIVE
To examine interhemispheric interactions of motor processes by using functional MRI (fMRI).


BACKGROUND
Despite evidence of interhemispheric inhibition from animal, clinical, and transcranial magnetic stimulation (TMS) studies, fMRI has not been used to explore activation and deactivation during unilateral motor tasks. fMRI changes associated with motor activity have traditionally been described by comparing cerebral activation during motor tasks relative to a "resting state." In addition to this standard comparison, we examined fMRI changes in the resting state relative to a motor task.


METHODS
Thirteen healthy volunteers performed self-paced sequential finger/thumb tapping for each hand. During fMRI data acquisition, four epochs were obtained; each comprised of 30 seconds of rest, 30 seconds of right hand activity, and 30 seconds of left hand activity. Resultant echoplanar images were spatially normalized and spatially and temporally smoothed.


RESULTS
As expected, hand movements produced activation in the contralateral sensorimotor cortex and adjacent subcortical regions and, when present, the ipsilateral cerebellum. However, hand movement also produced a significant deactivation (i.e., decreased blood flow) in the ipsilateral sensorimotor cortex and subcortical regions, and when present, the contralateral cerebellum. Conjunction analysis demonstrated regions that are activated by one hand and deactivated by the contralateral hand.


CONCLUSIONS
Unilateral hand movements are associated with contralateral cerebral activation and ipsilateral cerebral deactivation, which we hypothesize result from transcallosal inhibition.
Allison
J D
JD
Department of Radiology, Medical College of Georgia, Augusta 30912, USA.
Meador
K J
KJ
Loring
D W
DW
Figueroa
R E
RE
Wright
J C
JC
D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002531:Cerebellum / Q000098:blood supply / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D005385:Fingers / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000098:blood supply / Q000502:physiology; D009068:Movement / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D013003:Somatosensory Cortex / Q000098:blood supply / Q000502:physiology