Basal Ganglia

Question 1

Location

Answer 1

Between cortex - brainstem, interconnected between each other

Question 2

What structures make up basal ganglia?

Answer 2

Caudate nucleus
Putamen
Striatum (C + P)
Globus pallidum (external & internal segments)
Lentiform nucleus = Putamen + Pallidum
Subthalamic nucleus
Substantia nigra, just below the subthalamic nucleus

Question 3

Basal ganglia are part of

Answer 3

Inf loop: take info from cortex, process and analyze it (filter it) —> pass it back to cortex

Mediate all automatic activity (habitual control)

Question 4

Functions of basal ganglia

Answer 4

Learning + selecting most appropriate motor/behav programs

Control of voluntary but automatic motor movements
Eye movements
Procedural learning (new abilities)
Habit learning
Cognition and emotion

Question 5

Basal ganglia loops

Answer 5

Motor loop: control of movement

Oculomotor loop: eye movement control

Lateral orbitofrontal loop: social behaviours

Dorsolateral prefrontal loop: executive function (perform several activities at the = time, planning and “working memory”)

Anterior Cingulate loop: reinforces the previous BG loops

Question 6

Basal ganglia motor loop starts in

Answer 6

Motor cortex

Question 7

Motor + associative + limbic loops have

Answer 7

Spatial topographic organization

Question 8

Motor + associative + limbic loops provide

Answer 8

Topographically ordered input to
- post putamen (motor circuit)
- ventral striatum (limbic)
- caudate & ant putamen (associative circuit)

Question 9

Motor circuit

Answer 9

Starts w/ 1st motor neuron in precentral cortex (1ary motor cortex).

Descends and connects with basal ganglia

Then goes to nuclei in the thalamus

From there, back to the cortex

Question 10

If motor loop is activated

Answer 10

Thalamus will activate the cortex

Question 11

If we want to stop motor loop

Answer 11

Thalamus will stop firing to the cortex

Question 12

In the motor circuit, the associated nucleus is

Answer 12

Post putamen

Question 13

In the associative circuit, the associated nucleus is

Answer 13

Caudate

Question 14

In the limbic circuit, the associated nucleus is

Answer 14

Striatum

Question 15

Each area of the precentral cortex will be connected to

Answer 15

A specific corresponding region in the putamen (specific topographic organization)

Question 16

Main input

Answer 16

Striatum (C + P) —> reach post Putamen —> main action = inhibit structures it projects to

Question 17

Main output

Answer 17

Int segment of the globus pallidum (GPi) —> main action = inhibition thalamus

Question 18

Gpi

Answer 18

Inhibitory structure

Projects to thalamus —> projects back to cortex (closing the loop) through excitatory neurons

Question 19

Gpi activated =

Answer 19

inhibits thalamus, thalamus stops the movement

Question 20

Gpi not activated =

Answer 20

thalamus activates, increases activity in the cortex (“go”)

Question 21

Pathways of the motor loop

Answer 21

direct, indirect and hyperdirect pathways

Question 22

Direct pathway

Answer 22

Cerebral motor cortex —> excitatory act over input: striatum activates, through putamen.

Main role of putamen = inhibit Gpi: striatum connect w/ main output -> Gpi (inhibitory action over thalamus).
Inhibit inhibition = block Gpi = no thalamus inhibition.

Thalamus activate the cortex

Question 23

Direct pathway is a

Answer 23

“GO” pathway

Question 24

Indirect pathway

Answer 24

Cortex projects to Striatum and act it —> inhibit structures (Striatum) to which it projects.

Gpe also inhibits Subthalamic nucleus (excitatory structure that act Gpi)
(Gpe is inhibited by Striatum = Subthalamic nucleus not inhibited = it act Gpi)

   - When subthalamic nucleus works = act Gpi = block the thalamus = NO movement
   - When subthalamic nucleus doesn’t work= won’t act Gpi = thalamus activate = GO movement

Question 25

Indirect pathway is a

Answer 25

“STOP” pathway

Question 26

Hyperdirect pathway is even shorter than direct pathway because

Answer 26

We won’t have info entering basal ganglia through striatum.

Question 27

Hyperdirect pathway

Answer 27

Cortex enters basal ganglia in hyperdirect fashion by contacting Subthalamic nucleus directly, without passing through the Striatum.

Subthalamic nucleus contacts Gpi —> activate it

Gpi = INHIBITORY = inhibits thalamus

Question 28

Hyperdirect pathway is a

Answer 28

“STOP” pathway

Question 29

Main neurotransmitter in the loops of basal ganglia is

Answer 29

Dopamine

Question 30

Dopamine effects

Answer 30

Opposite ones on Direct and Indirect motor pathways

Question 31

Dopamine binds to

Answer 31

D1 receptors = direct pathway —> activated
D2 receptors = indirect pathway —> inhibited

Question 32

Net result of dopamine in the brain

Answer 32

Promote movement

Question 33

Párkinson disease

Answer 33

No dopaminergic neurons = difficult to move
(lack of dopamine)

Question 34

Basal ganglia location

Answer 34

centre of the brain