week 6 lectures (basil ganglia)

Question 1

where does the basil ganglia recieve its input from?

Answer 1

the cortex

Question 2

what is the name of the loop that goes cortex-basil ganglia- thalamus- cortex?

Answer 2

the re-entrant loop

Question 3

what are 4 sections of the basal ganglia? visualise where they are

Answer 3

Question 4

visualise where the internal capsule is in a horizontal view

Answer 4

Question 5

what is the striatum composed of?

Answer 5

the caudate nucleus

the putamen

Question 6

what is the putamen + globus pallidus called?

Answer 6

the lentiform nucleus

Question 7

where does information from the cortex land in the basal ganglia?

Answer 7

the striatum

Question 8

where in the basal ganglia does information go to the thalamus from

Answer 8

the globus pallidus

Question 9

is the basal ganglia output continuous or discreet?

Answer 9

there is a continuos inhibitory output that can either be increased or decreased

Question 10

what are the two pathways running from the striatum to the globus pallidus

Answer 10

the indirect and the direct pathway

INDIRECT- striatum to globus pallidus internal segment to globus pallidus external segment

DIRECT - striatum to globus pallidus external segment

Question 11

do the direct and indirect pathway do the same thing?

Answer 11

• they work against each other
• this is called balanced opposition
• direct pathway inhibits
• indirect pathway excites

Question 13

how does the direct pathway make the thalamus more responsive

Answer 13

• it inhibits the basal ganglia which is inhibitive
• therefore it inhibits the inhabition leading to an excitatory change overall

Question 14

how does the indirect pathway make the thalamus less responsive

Answer 14

striatum to Gpe cells inhibit the inhibitory output of GPe

this increases the activity in GPI

this means there is greater inhibtory output from the gpi

so the thalamus is less respnoive

Question 15

does increased output from the basal ganglia lead to the thalamus being more or less responsive

Answer 15

more responsive, as basal ganglia output is inhibitory

Question 16

where do dopaminergenic axons come from?

Answer 16

the substantia nigra (midbrain)

Question 17

what is the effect of increaased dopamine on the thalamus?

Answer 17

• when dopamine levels increase the inhibition on the thalamus drops

Question 18

how does dopamine decrease the inhibition on the thalamus?

Answer 18

• there are dopamine receptors on the direct (D1) and indirect (D2) neurons in the globus pallidus
• D1 receptors are excitatory- so increases the direct pathways
• D2 receptors are inhibitory- so decrease the indirect pathway
• this makes the thalamus more responsive

Question 19

are the neurons of the striatum and globus pallidus spontaneously active

Answer 19

striatum no- only activated when stimulated by cortex

globus pallidus yes

Question 20

how is dopamine related to parkinsons

Answer 20

• parkinsons disease is associated with a loss of dopamine
• this means the thalamic activity is less
• this meansthreshold for activity is raised
• it is difficult to iniate movement
• this loss of dopamine is due to the loss of the substantia nigra

Question 21

what is the cause of huntingtons disease?

Answer 21

• a loss of striatal neurons in the indirect pathway
• as a result the balance switches to favour the direct pathway
• this means the thalamus is over responsive
• this can result in exaggerated movements

Question 22

what are 4 other circuits influenced by the basal ganglia?

Answer 22

other motor circuits

dorsolateral prefrontal circuit

lateral orbitofrontal circuit

anterior cingulate circuit

Question 23

what does the dorsolateral prefrontal circuit do?

Answer 23

cognition and problem solving

Question 24

what does the lateral orbitofrontal circuit do?

Answer 24

empathy, social controls

Question 25

what does the anterior cingulate circuit do?

Answer 25

motivational responses procedural learning