Motor Areas of the Cerebral Cortex
There seems to be an insuperable objection
to the notion that the cerebral hemispheres are for movements. The
reason,
I suppose, is that the convolutions are considered to be not for moving
but for ideas. -- J. Hughlings Jackson (1870)
The cortex must be regarded as a great
network
of reverberatory circuits, constantly active. A new stimulus, reaching
such a system, does not excite an isolated reflex path but must produce
widespread changes in the pattern of excitation throughout a whole
system
of already interacting neurons. -- Karl Lashley (1951) The problem
of
serial order in behavior
Primary motor cortex
(Broadman's
area 4)
Premotor cortex (Broadman
area
6 - lateral)
-
Anatomy
-
Neuron functional properties
- Sensory (visual, tactile, auditory). Anticipatory activity
Supplementary motor area
(Broadman
area 6 - medial)
- Anatomy
-
Effects of electrical stimulation
- Electrical stimulation evokes more organized movements than
does stimulation
of primary motor cortex
-
Neuron functional properties
-
PET studies
- SMA active for imagined as well as executed movements
-
Readiness potential
- Change in electrical potential measured over SMA before
movements
- RP can begin as much as 1000 ms before movement initiation
- RP of lower amplitude for unconsciously executed movements
- RP decays before aborted movements
-
The rich variety of results obtained in SMA has spawned exhuberant
speculation
about its role in voluntary movement,
Last edited 9-9-09