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Abstract:
Using echoplanar fMRI, we examined somatosensory and motor
cortex during simple hand movements. Each run alternated a task
with rest: passive movement (P), in which we flexed participants'
fingers in time to magnet switching, endogenous control with low
force requirement (ELF), in which participants produced the flexion
pattern themselves against low resistance, and endogenous control
with higher force requirement (EHF). S1 activity increased during
ELF and EHF relative to P, but did not differ significantly between
the two endogenous tasks. Thus somatosensory processing is more
involved in control of pattern than regulation of force. Turning to
joint activity of S1 and M1, both were activated contralateral to
the moving hand in all 12 participants during ELF and EHF -- and
also during P. The latter shows that feedback from passive movement
engaged contralateral sensorimotor cortex as a system, not just its
somatosensory component, highlighting the impact of
interconnectivity among structures. Ipsilateral activity, however,
was more restricted. During P only 4 participants showed activity
in both S1 and M1 ipsilaterally. Finally, the cluster most
correlated with task regardless of brain region was usually in M1,
even during P, again highlighting interconnectivity and the
systemic properties of sensorimotor cortex.
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