Psy 123_Lec 10 Action

The net consequence is reduced inhibitory output from

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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! Parkinson’s Disease! 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 into play. 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. ! Different p...
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