What are the input, intermediate, and output nuclei of the basal ganglia?
input: caudate, putamen
intermediate: GPe, subthalamic nucleus
output: GPi (to thalamus), SNr (to thalamus and superior colliculus)
For which parts of the basal ganglia does the GPi function as output nuclei? Where does the GPi project?
the GPi functions as output nuclei for limb-related regions of the basal ganglia
the GPi projects to the thalamus
For which parts of the basal ganglia does the SNr function as output nuclei? Where does the SNr project?
the SNr function as output nuclei for the eye-movement-related areas of the basal ganglia
the SNr project to the thalamus and the superior colliculus
What are the inputs and outputs of the subthalamic nucleus? What type of basal ganglia nucleus is this?
outputs: GPi and Snr
type: intermediate nucleus
What are the two kinds of major spiny neurons (MSN) in the striatum of the basal ganglia?
1. those that express D1 dopamine receptors; excited by dopamine (direct pathway)
2. those that express D2 dopamine receptors; inhibited by dopamine (indirect pathway)
What does dopamine do to D1 and D2 receptors in the stiatum and how does this effect thalamocortical projections?
dopamine stimulates D1 (direct pathway) and ultimately increases thalamocortical projections by decreasing their inhibition
dopamine inhibits D2 (indirect pathway) and ultimately decreases thalalmocortical projections by increaseing their inhibition
What are treatments for Parkinson's disease?
L-dopa: replaces dopamine in striatum that has been diminished by SNc damage
pallidotomy (i.e. permanent damage to GPi): reduces inhibitory input to thalamus from GPi
electrical stimulation of subthalamic nucleus: mechanism unclear; reduces GPi inhibition of thalamus
True or False: There is a paradoxical relationship between the subthalamic nucleus and the GPi: the subthalamic nucleus both stimulates it directly and also inhibits it indirectly, but the net effect is to reduce GPi projections.
What are characteristics of Huntington's Disease?
results from decreased inhibition of the thalamus --> increase in thalamocortical projections
preferential degeneration of D2 medium spiny neurons in striatum (indirect pathway)