BASAL GANGLIA and ATTENTION

BASAL GANGLIA and ATTENTION - BASAL GANGLIA: 1. REVIEW THE...

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BASAL GANGLIA: 1. REVIEW THE BASAL GANGLIA PAPER ONLINE. 2. Parkinson’s: a. Direct pathway: Substantia nigra + Striatum #1 - external globus pallidus - thalamus. Facilitates movement b. Indirect pathway: Substantia nigra - Striatum #2 - internal globus pallidus - subthalamic nucleus (right below thalamus) - thalamus. Inhibits movement. Pathway Path # inhibitory pathways (-) Description Dopamine receptors Direct striatum - →GPi/SNr - →thalamus + →cortex 2 (even) Cortical activity that excites cells in the striatum that participate in the direct pathway leads to inhibition of areas of the GPi and SNr, which in turn removes their tonic inhibition from the thalamus. (This removal of inhibition by inhibition is called "disinhibition".) D1 (stimulatory) Indirect striatum - →GPe - →STN + →GPi/SNr - →thalamus + →cortex 3 (odd) In contrast, cortical activity that excites the striatal cells in the indirect pathway is thought to inhibit the thalamus (by inhibiting the disinhibition). D2 (inhibitory)
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c. More clearly, DA starts in the substantia nigra, projects to 2 areas of the striatum (one inhibitory, one excitatory), then to 2 areas of the globus pallidus (internal and external). Then it goes on to the thalamus. d. With Parkinson’s you get 80% of loss of DA cells in the Substantia nigra before showing effects and there is a larger excitatory signal from the subthalamus leading to a larger inhibitory signal to the ventral lateral nucleus of the thalamus leading to a net reduction of excitatory signal sent to cortex (get hypokinesia). e. Behavioral: Rigidity: increased tone/ stiffness in muscles. Mask-like expression. Tremor Bradykinesia: slowness of movement Poor balance Shuffling gait. Cognitive problems: with DA depletion, have problems learning reward associations, motivation problems, ahedonia (like drug withdrawal with DA downregulation) ‘Habit systems problems’: trouble forming automatic motor sequences. Things don’t become easily learned. f.
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This note was uploaded on 04/23/2008 for the course COGS 107C taught by Professor Chiba during the Spring '07 term at UCSD.

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BASAL GANGLIA and ATTENTION - BASAL GANGLIA: 1. REVIEW THE...

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