Basal Ganglia - Core Systems

Question 1

What is the basal ganglia?

Answer 1

Group of brain structures that help control movements

Question 2

What does the basal ganglia do for movements?

Answer 2

Chooses the right action for a goal, whilst stopping unnecessary movements. Acts as a “filter” letting the best go through

Question 3

What happens if the basal ganglia is not working properly?

Answer 3

Conditions like Parkinson’s and Huntington’s disease happen

Question 4

What parts are in the basal ganglia?

Answer 4

Striatum (has caudate nucleus and putamen), global pallidus (GP), subthalamic nucleus (STN) and substantia nigra (SN)

Question 5

What is the striatum?

Answer 5

Main input structure of the basal ganglia, recieves info from the cortex and regulates/does voluntary movement

Question 6

Where does information come from to the striatum?

Answer 6

info comes from brain’s higher centres like prefrontal cortex and gets sent to the striatum to prepare for movement

Question 7

what is the caudate nucleus?

Answer 7

it is in the striatum and is involved in cognitive and emotional functions

Question 8

what is the putamen?

Answer 8

plays a role in motor control

Question 9

what is the globus pallidus (GP)

Answer 9

key output structure of the basal ganglia

Question 10

what does the globus pallidus do?

Answer 10

signals to the thalamus which sends the informaton to motor areas of the cortex

Question 11

there are segments in the globus pallidus (GP) what are they?

Answer 11

internal segment (GPi) and external segment (GPe)

Question 12

What does the internal segment do (GPi)

Answer 12

inhibits movement by sending inhibitory signals to the thalamus = suppress motor activity

Question 13

what does the external segment do (GPe)?

Answer 13

helps regulate the inhibition and controls motor movement by interacting with other brain areas e.g., cerebellum, prefrontal cortex

Question 14

what is a subthalamic nucleus (STN)?

Answer 14

regulates motor activity of the basal ganglia pathways

Question 15

what are the pathways?

Answer 15

Direct and indirect pathways

Question 16

what does the direct pathway mean?

Answer 16

allows movement to go through by reducing inhibition in the thalamus = movement and dopamine from the SN activates pathway through D1 receptors

Question 17

What about indirect pathway?

Answer 17

leads to the inhibition increasing in the thalamus = inhibits unwanted movements and dopamine blocks this pathway through D2 receptors

Question 18

what if the balance between the pathways is bad or disrupted?

Answer 18

clinical disorders such as parkinsons and huntingtons can happen

Question 19

what is parkinsons

Answer 19

when the direct pathway is inhibited and not active, hard to do movements, dopamine doesnt go through

Question 20

what is huntingtons disease

Answer 20

happens when the indirect pathway is disrupted, excessive dopamine that increases movement rather than stopping

Question 21

what is the substantia nigra (SN)

Answer 21

small region in the brainstem that produces dopamine which allows for movement

Question 22

is there evidence for the role of basal ganglia?

Answer 22

yes = neuroimaging (aron et al) + clinical disorders + animal studies

Question 23

So why is neuroimaging a strength?

Answer 23

fMRI scans can show when brain activity is used during motor goal selection and how BG is involved

Question 24

whats the study for neuroimaging

Answer 24

aron et al (2007)

Question 25

what did aron et al (2007) say

Answer 25

he found that participants who had to suppress their automatic responses (stopping reflexes) the brain scan would show the STN light up

Question 26

what about clinical disorders showing evidences?

Answer 26

parkinsons shows the SN loses dopamine producing cells = lack of D1 receptors in the basal ganglia = bradykinesia occurs which is slowness of movement

Question 27

and another disorder?

Answer 27

huntingtons which is when the striatum is damaged which means the connection between the other areas for movement is disrupted = leading to hyperkintetic symptoms like chorea (fast movements uncontrolled) in the indirect pathway

Question 28

what about tourettes?

Answer 28

tourettes syndrome means that the basal ganglia circuit is disrupted leading to tics (involuntary movements)

Question 29

are there any animal studies?

Answer 29

yes alexander et al, (1990)

Question 30

what he find?

Answer 30

found that monkeys with lesions to their basal ganglia were unable to pick the correct motor action leading to show BG involved in selecting motor actions

Question 31

strengths?

Answer 31

lots of various rm + neuroimaging + animal studies + clinical observations and disorders = real life application

Question 32

another strength?

Answer 32

real world validation and lab based research = validity

Question 33

weaknesses?

Answer 33

neuroimaging is correlational data but doesnt show causation between different parts of the brain, fmri shows basal ganglia but other areas can cause movements

Question 34

another weakness?

Answer 34

animal models lack generalisability to humans, more simpler nervous systems so we cant put that onto humans cuz humans are complex = oversimplification

Question 35

another weakness?

Answer 35

basal ganglia doesnt work alone, maybe it interacts with other brain regions e.g., prefrontal cortex and cerebellum (motor co-ordination)

Question 36

any future directions to help find out?

Answer 36

optogenetics (light to control neurons) + connectomics (study of brain connects) can help find out BG role in motor control and in real time

Question 37

another future direction?

Answer 37

basal ganglia might have role to play in cognition and emotions, look more deeply to see if the BG plays a role as PD has a cognitive and motor decline, not just motor