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MICHAEL
GRAZIANO
Professor of Psychology
Ph.D., Princeton University, 1996 |
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| CASE
STUDY |
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| RESEARCH
SUMMARY |
| How does the brain monitor
the location of the limbs and guide movement ? We use a range
of techniques to study sensorimotor integration in the monkey
brain, including single neuron physiology, electrical stimulation,
chemical activation and deactivation, and anatomical tract tracing
to address these questions. We study parietal areas such as
area 5, the ventral intraparietal area, and the medial intraparietal
area, and motor areas such as M1, lateral premotor cortex, and
the supplementary motor area. In a recent set of studies of
the motor cortex, we electrically stimulated cortical sites
using 500 ms trains of electrical pulses. These stimulation
trains were longer than those typically used in studies of motor
cortex, but they approximated the time scale of reaching and
grasping movements. The stimulation trains evoked complex, coordinated
movements that appeared to match common gestures in the monkey’s
repertoire. For example, stimulation of one site caused the
arm to reach to the space about 10 cm in front of the chest
while the hand shaped in an apparent grip posture. Stimulation
of another site caused the hand to move to the mouth and close
in a grip posture and caused the mouth to open. Stimulation
of yet another type of site caused an apparent defensive gesture
including a squint and grimace, a turning aside of the head,
and a thrusting of the hand into lateral space as if to block
a nearby threatening object. These movements were reliable and
could even be evoked under anesthesia. Our current focus is
on studying these complex movement programs that are triggered
by motor cortex stimulation, to better understand the neuronal
circuits that underlie them. |
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