Anatomy and function of the basal ganglia Flashcards
Areas of the brain associated with strategy
- Association areas of neocortex and basal ganglia
Areas of the brain associated with tactics
- Motor cortex
- Cerebellum
Areas of the brain associated with execution
- Brainstem
- Spinal cord
What forms the lentiform nucleus
- Putamen
- Globus pallidus
Location of lentiform
- lateral to thalamus
What does the corpus striatum consist of
- Basal ganglia
- Internal capsule
Main components of the basal ganglia
- Ventral striatum
- Dorsal striatum
- Globus pallidus
- Ventral pallidum
- Substantia nigra
- Subthalamic nucleus
Components of the ventral striatum
- NAcc
- Olfactory tubercle
What does the pallidum refer to
- Consists of a large structure called globus pallidus together with a smaller ventral extension called the ventral pallidum
What can the globus pallidus be divided into
- GPe
- GPi
What is the lateral geniculate body
- Is a relay centre in the thalamus for the visual pathway - receives a major input from the retina
What is the dorsal striatum also known as
- Neostriatum
- Motor striatum
- Caudate + putamen
What is the corpus striatum divided by
- Divided by internal capsule white matter of ascending and descending tracts
How does the basal ganglia interact with the cortex
Basal ganglia –> Thalamus –> Cerebral cortex
General steps of any basal ganglia loop
1) Cortical input
2) Striation
3) Pallidum
4) Thalamus
5) Cortical targets
Motor loop steps
1) Motor, premotor, somatosensory cortex
2) Putamen
3) Lateral globus pallidus, internal segment
4) Ventral lateral and ventral anterior nuclei
5) Primary motor, premotor, supplementary motor cortex
Direct pathway
Cortex –ex–> Striatum –in–> GPi –in–> thalamus –ex–> cortex
What does activation of the direct pathway promote
- Movement
Indirect pathway
Cortex –ex–> Striatum –in–> GPe –in–> STN –ex–> GPi –in–> thalamus –ex–> cortex
What does the activation of the indirect pathway do
- Withold movement
Hyperdirect pathway
Cortex –ex–> STN –ex–> GPi –in–> thalamus –ex–> cortex
What does the activation of the hyperdirect pathway do
- Pauses movement
Effect of thalamus inhibition on movement
- Prevents movement
Effect of reducing inhibition of thalamus on movement
- Reducing inhibition of thalamus facilitates movement
What is dopamine released by
- Released by the substantia nigra
What are the two populations striatum neurons
Striatum medium spiny neurons with specialised dopamine receptors
1) Direct D1
2) Indirect D2
Effect of DA on direct D1 neurons
- DA ramps up MSN excitation
Effect of DA on indirect D2 neurons
- DA dampens down MSN excitation
What interneurons are present in the striatum
- Striatum interneurons that use ACh
- ACh opposes effects of DA
What does ACh tip the balance of pathways towards
- tips pathways towards prevention of movement
What is the balance of movement activity based on
- The balance of activity between the 2 medium spiny neuron spiny neuron populations determines the likelihood of movement taking through the direct and indirect pathways
- This balance is regulated by dopamine and ACh and influenced by the cortical inputs to the striatum
