Chapter 18- Basal Ganglia

Question 1

what are the 6 functions of basal ganglia ?

Answer 1

1) regulation of muscle contraction and force
2) initiation and termination of mvmt
3) regulate multi-joint mvmt
4) control movement sequencing
5) oculomotor control
6) habit learning

Question 2

what parts of the basal ganglia are for input ? where is the input usually from ?

Answer 2

caudate nucleus and putamen

input usually from cortex

Question 3

what parts of the basal ganglia are for output ?

Answer 3

globus pallidus

Question 4

what parts of the basal ganglia have the information “bounce around” ? where does it connect to ?

Answer 4

substantia nigra

connected to striatum and also projects to thalamus

Question 5

does the basal ganglia communicate with the spinal cord ?

Answer 5

nope

Question 6

which part of the basal ganglia goes wrong in Parkinson’s ?

Answer 6

substantia nigra

Question 7

which neurotransmitter is involved in basal ganglia ?

Answer 7

dopamine

Question 8

what does the basal ganglia like ? what drives it ?

Answer 8

reward (dopaminergic)

therefore, will favor motor programs that lead to reward

Question 9

what are the input parts of the basal ganglia involved in ? 3 names and roles

Answer 9

putamen and caudate nucleus
1- some related to movement (phasic cells)
2- some related to movement but only with reward (tonic cells)
3- some related to movement only in right context, like in sequences (phasic cells)

Question 10

what are the cells in the substantia nigra involved in ?

Answer 10

reward itself or cues to reward (guide for which movement to encode)

Question 11

what is the majority of cells in striatum

Answer 11

phasic cells (80%)

Question 12

what do the spines of the phasic cells do ?

Answer 12

they seem to support movement production

Question 13

when do phasic cells fire ?

Answer 13

only when movement is going to be produced

therefore they are quasi-silent

Question 14

when do tonic cells fire ?

Answer 14

more perpetually

always firing AP

Question 15

how can the tonic cells firing pattern be modified ?

Answer 15

they can be conditioned to modulate firing pattern in relation to movement. tonic cell modulates firing in relation to learned behavior (with reward)

Question 16

how exactly will tonic cells fire after they’ve been conditioned to associate a “click” with a reward ?

Answer 16

tonic cells continuously fire for a fact. however, after the click reward, there is a pause and then a rebound in the firing AP. this indicates that they need to pause in order to increase firing after.

Question 17

in the substantia nigra, when will the cells fire ?

Answer 17

to predict reward

Question 18

with classical conditioning, how will the firing pattern in the substantia nigra change ?

Answer 18

at first, the SN will only fire when the reward is presented.
however, when it is learned that the light is the trigger for reward, they will fire during the trigger, and then, after more time, will learn to fire even before the trigger.

Question 19

how do striatum cells preferentially fire ? how is this demonstrated

Answer 19

inside a sequence.
if a rat cleans itself, it does so in a natural sequence of events. neurons will fire preferentially in different phases of this sequence, and will fire more in a sequence.

Question 20

what kind of movement is the basal ganglia best suited to represent ?

Answer 20

representation of SUCCESSFUL motor programs

Question 21

do we need the basal ganglia to move ?

Answer 21

nope

Question 22

what does the striatum consist of ?

Answer 22

caudate and putamen

Question 23

what happens when the striatum is at rest ?

Answer 23

since the striatum inhibits the globus pallidus, the globus pallidus is tonically active. this inhibits the VA/VL complex of the thalamus which then cannot excite the upper motor neurons in the cortex.

Question 24

what happens when the striatum is transiently excited ?

Answer 24

this transiently inhibits the globus pallidus, which means that we’re inhibiting the inhibition effect the globus pallidus has on the VA/VL complex of the thalamus, meaning the frontal cortex can be excited

Question 25

what happens when spiny cells in the caudate nucleus are transiently activated ?

Answer 25

this transiently inhibits the cells in the substantia nigra, meaning we’re inhibiting the inhibition on the superior colliculus, and saccadic eye mvmt can be observed

Question 26

what is the purpose of the direct pathway ?

Answer 26

to facilitate the initiation of voluntary movement

Question 27

in the direct pathway, which cells are activated transiently and which are tonic ?

Answer 27

the only tonic ones are in the VA/VL complex of the thalamus

Question 28

what does the substantia nigra pars compacta use to excite the striatum (caudate and putamen) in the direct pathway ?

Answer 28

D1

Question 29

what input does the caudate and putamen receive in the direct pathway ?

Answer 29

from the cortex and the substantia nigra pars compacta

Question 30

what is the struggle between the indirect and direct pathway ?

Answer 30

direct wants mvmt

indirect wants to inhibit it

Question 31

in the indirect pathway, which cells are tonic ?

Answer 31

subthalamic nucleus

Question 32

what is the purpose of the indirect pathway ?

Answer 32

This second pathway serves to increase the level of
tonic inhibition
& modulates the disinhibitory actions of the direct pathway.

Question 33

what happens when signals from the cortex activate the indirect pathway ?

Answer 33

• medium spiny neurons inhibit the external globus pallidus
• subthalamic cells become more active since they are no longer tonically inhibited
• excitatory synapse between subthalamic cells and internal globus pallidus
• increase inhibitory outflow of basal ganglia

Question 34

what are GABA-ergic inhibitory cells in the basal ganglia ?

Answer 34

medium spiny neurons

Question 35

in Parkinson’s, which pathway wins ?

Answer 35

bradykinesia, indirect pathway wins

Question 36

in Huntington’s, which pathway wins ?

Answer 36

the direct pathway, causing excessive movement

Question 37

how are direct and indirect pathways organized ?

Answer 37

center-surround

Question 38

how does center-surround organization explain the course of action of the indirect pathway ?

Answer 38

With activation of the indirect pathway, neurons In a surround region of the internal segment of the globus pallidus are driven by excitatory inputs from the subthalamic nucleus; this reinforces the suppression of a broad set of competing motor programs.

Question 39

how does center surround organization relate to the direct pathway ?

Answer 39

Simultaneously, activation of the direct pathway leads to the focal inhibition
of a more restricted center cluster of neurons in the internal segment; this in turn results in the disinhibition of the VA/VL complex and the
expression of the intended motor program.

Question 40

what happens with the inactivation of tonically active cells of substantia nigra pars reticulata ?

Answer 40

causes saccades

Question 41

what could we observe in a brain of a Huntington patient ?

Answer 41

reduced size of striatum

Question 42

what part of the pathway is degenerated in Parkinson’s

Answer 42

between the substantia nigra and the globus pallidus

Question 43

what part of the pathway degenerates in Huntington’s ?

Answer 43

between the globus pallidus and the subthalamic nucleus (the indirect pathway)

Question 44

what does deep brain stimulation do ?

Answer 44

targets certain areas of the brain, like globus pallidus internal segment, thalamus, subthalamic nucleus

influences circuits, create a much more regular discharge rate

Question 45

in the case where saccades happen if tonically active cells of substantia nigra pars reticulata are inhibited, what will cure it ?

Answer 45

GABA agonist injection - it will inhibit the inhibition

Question 46

does basal ganglia only modulate motor aspects of behavior ?

Answer 46

nope

Question 47

what are the 4 different loops the basal ganglia is involved in ?

Answer 47

1) body movement loop
2) oculomotor loop
3) prefrontal loop (regulate the initiation and termination of cognitive processes such as planning, working
memory, and attention)
4) limbic loop (emotional component)