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Abstract:
There is considerable evidence that many of the same brain
areas become active during overt and imagined movements. But does
this activity arise from similar computations in both cases, e.g.,
running similar motor programs? If the same brain areas are
performing similar computations, then one might expect them to
exhibit analogous temporal patterns of activation during overt and
imagined movements. To test this prediction for cortical brain
areas, we examined the spatiotemporal patterning of current source
density (CSD) recorded from the scalp. The experiment involved
synchronizing an overt or imagined movement by one or both index
fingers to the presentation of a temporally predictable signal.
Event-related potentials were recorded from 59 electrode sites
across the scalp and then transformed to CSD in order to enhance
spatial resolution and minimize the contribution of noncortical
sources. Electromyographic activity was recorded from the finger
flexor muscles and used to reject trials on which imagined
movements were accompanied by muscle activity. The results provide
evidence of similar computations during overt and imagined
movements. Both types of response were accompanied by similar CSD
topographies that developed in similar ways over time. Activation
of the supplementary motor area was followed by activation of
primary motor cortex and then by somatosensory cortex. Additional
findings, concerning the moment-by-moment "functional coupling"
between cortical areas, will also be presented. (Supported by NINDS
NS37528)
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