T2L8 structure and function of the basal ganglia

Question 1

basal ganglia basics

Answer 1

the filter of the brain

highest order hierarchy of motor control - tactics

Question 2

anatomy

Answer 2

• globus pallidus
• putamen
• caudate nucleus
• thalamus

s7/10/11/12/13/14

Question 3

globus pallidus

Answer 3

split into pars externa and pars interna

both = pallidum

Question 4

lentiform nucleus

Answer 4

putamen + globus pallidus

Question 5

corpus striatum

Answer 5

caudate + putamen + pallidum

- divided by internal capsule

Question 6

internal capsule

Answer 6

white matter ascending and descending tracts

Question 7

neostriatum

Answer 7

dorsal striatum (motor striatum) + caudate + putamen

Question 8

basal ganglia interface with cortex

Answer 8

s15

Question 9

4 basal ganglia loops

Answer 9

1. motor loop
2. oculomotor loop
3. prefrontal loop
4. limbic loop

all go from cortical inputs (eg motor) to striatum (eg caudate body) to pallidum (eg ventral pallidum) to thalamus (eg mediodorsal nucleus) to cortical targets

act as filters

Question 10

motor loop

Answer 10

movement filter

thalamus&raquo_space; cerebral cortex&raquo_space; basal ganglia (striatum and pallidum)&raquo_space; back 2 thalamus

Question 11

the direct pathway

Answer 11

s20

PROMOTE MOVEMENT

Question 12

the indirect pathway

Answer 12

s21

WITHHOLD movement

Question 13

the hyperdirect pathway

Answer 13

pause movement s22

all is on s22

Question 14

LEARN THIS SLIDE

Answer 14

S22

Question 15

pathway q

Answer 15

hoe does the striatum know if a motor plan is to be promoted (by direct pathway) or prevented (indirect pathway)?

there are 2 populations of striatum cells with specialised dopamine receptors: (medium spiny neurons) (MSN) s49,50

substantia nigra releases dopamine
Direct D1- increase MSN excitation
indirect D2- decrease MSN excitation

balance
» release of DA promotes movement
» release of ACh from interneurons opposes effects of DA&raquo_space; prevents movement

so the balance of the 2 types of MSN populations determines the likelihood of a movement

regulated by dopamine and acetylcholine

influenced by cortical inputs to striatum

see s54 for relation to direct and indirect pathways

Question 16

substantia nigra

Answer 16

releases dopamine