Basal Ganglia

Question 1

what are the major structures of the basal ganglia?

Answer 1

the caudate and putamen (striatum), globus pallidus and substantia nigra (lenticular nucleus), subthalamic nuclei

Question 2

where are the subthalamic nuclei located?

Answer 2

the midbrain diencephalic junction

Question 3

what are the main basic functions of the basal ganglia?

Answer 3

INITIATION AND EXECUTION OF MOVEMENT

• regulates contraction, force, multijoint movement, sequencing)
• preventing unwanted movements via inhibitory ctrl
• direct and indirect pathways for the desired movement

Question 4

what are the secondary functions of the basal ganglia?

Answer 4

eye movement loop, goal-directed behavior loop, social behavior loop, emotion loop

Question 5

what are the 2 cortices that do not have basal ganglia projections?

Answer 5

the primary visual and primary auditory cortices

Question 6

where does the caudate receive input from?

Answer 6

heteromodal association cortices, motor areas of frontal lobe involved in eye movements

Question 7

where does the putamen receive input from?

Answer 7

primary and secondary sensory cortices in the parietal lobe
higher-order visual cortices in occipital and temporal lobes
premotor cortices and PriMC
auditory assn cortices temporal lobe

Question 8

What are the specific origins of input to the basal ganglia?

Answer 8

the striatum (the putamen and caudate)

Question 9

What are the specific destinations of output from the basal ganglia?

Answer 9

• ventral lateral and ventral anterior nucleus (project to entire frontal lobe)
• intralaminar nucleus ( additional motor relay)
• mediodorsal nucleus (limbic basal ganglia loop)
• superior colliculus

Question 10

List the steps and structures involved in the direct pathway of the basal ganglia

Answer 10

1. Thalamus sends constant excitement to the cortex
2. GPi, SNpr intervene to prevent unwanted movement
3. When movement is needed, the cortex tells the striatum to inhibit GPi and SNpr

Question 11

List the steps and structures involved in the indirect pathway of the basal ganglia. (when movement is no longer needed)

Answer 11

1. via the striatum, the cortex inhibits the global pallidus EXT, stopping it from inhibiting subthalamic nuclei
2. cortex then activates subthalamic nuclei
3. Subthalamic nuclei signals globus pallidus internus and substantia nigra
4. GPi and SN become better inhibitors to the thalamus.

Question 12

what is contribution to the direct and indirect pathways of the basal ganglia?

Answer 12

it’s secreted in the substantia nigra pars compacta and released to modulate the pathways. Its excitatory to the striatum in the direct pathway and inhibitory in the indirect» dual effects of in decreasing thalamic suppression (facilitating movement)

Question 13

What does ACh contribute to the basal ganglia pathways? Where is it mostly located?

Answer 13

large amounts stored in nm junction; it inhibits dopamine when appropriate and can quickly interrupt ongoing motor behavior in response to salient environmental stimuli

Question 14

list the neurotransmitters relevant to the basal ganglia pathways

Answer 14

dopamine
ACh
GABA (primary)
glutamate (primary)

Question 15

what is the function of the oculomotor loop in the basal ganglia?

Answer 15

higher control of eye movement, spatial attention , saccadic initiation and smoothness

Question 16

list the 3 non-motor BG loops and their locations

Answer 16

goal-ddirected behavior loop (dorsolat pre-frontal cortex)
socail behavior loop (dorsolat pre-frontal cortex)
limbic /emotional loop (ant cingulate cortex)

Question 17

What is the function of the goal-directed loop? Structures involved?

Answer 17

fn: decision making, goal-directed behavior, planning, action-selection, learning
structures: global pallidus internus

Question 18

What is the function of the social behavior loop? Structures involved?

Answer 18

fn: recognizing social cues, regulate self control, evaluating relevant and irrelevant info
structure: substantia nigra pars reticulata

Question 19

What is the function of the limbic/emotion loop? Structures involved?

Answer 19

fn: links emotions to cog and motor systems; reward seeking; outcome predictions
structures: input from ventral tegmental area

Question 20

Describe Parkinson’s disease and the structures that can cause this impairment.

Answer 20

there is a gradual decrease in dopamine levels>no dual effect on thalamus> small, slow, choppy movement, tremors, stooped posture, and motor freezing

Question 21

Describe Huntington’s disease and the structures that can cause this impairment.

Answer 21

damage to the movement suppressors (striatum: caudate and putamen) >huge ballistic, dancelike movements