Unformatted text preview: onsequence is reduced
inhibitory output from the GPi and thus an increase in cortical
excitation and movement.!
The disease occurs in the straitum and can lead to many symptoms - clumsiness in motor movements, and eventually cognitive impairments. What happens
is this inhibitory pathway in striatum is greatly reduced, leading to increases in cortex activation. Disorders of Motor Pathways and Structures!
A degenerative disorder of the basal
ganglia in which the pathology results
from the loss of dopaminergic cells in the
substantia nigra. Primary symptoms
include difﬁculty in initiating movement,
slowness of movement, poorly articulated
speech, and, in some cases, resting
tremor.! PD primarily reduces the inhibitory activity along the direct pathway,
resulting in increased inhibition from the GPi to the thalamus and
thus a reduction in cortical activity and movement.!
Parkinson's has the opposite problem, leading to decrease in cortex activity. Neural Coding of Movement! The activity from a single neuron for 8 directions.! The preferred direction for that neuron is tuned to 180
degree leftward movement.! Each neuron’s preferred direction can be plotted as a
vector. The population vector is the sum of the
individual neurons.! For each direction, the solid lines are the individual
vectors for each of 241 motor cortex neurons; the
dotted line is the population vector calculated over the
entire set of neurons. The population vector closely
corresponds to the actual movement.! Selective for movement in one direction Neighboring neurons tend to work together as a population. Can compute
preferred direction of population of neurons by averaging vectors together. More accurate of actual movement of the monkey in population than
each neuron individually. Goal Selection and Action Planning! Affordance Competition
Hypothesis: How other
components of the system come
For example if you have the visual
cortex, each one of those inputs
(say looking at diff. objects) each
one will have different pathways.
Eventually different action plans,
one will win out. All plays into the
actual execution of that action;
Visual feedback goes back into the
system, and then may cause bias
for the next movement. Affordance Competition Hypothesis!
Inputs from the visual cortex proceed dorsally across the parietal lobe, transforming visual information into
representations of potential actions. !
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- Fall '11
- motor cortex, motor pathways