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OS III > Basal Ganglia & Cortico-striate Loops > Flashcards

Basal Ganglia & Cortico-striate Loops Flashcards

1
Q

Are basal ganglia bundles of white or gray matter? What hemisphere are they in? What are they?

A 
masses of gray matter in cerebral hemispheres that surround the thalamus
include: 
caudate
putamen
nucleus accumbens
globus pallidus
subthalamic nucleus
substantia nigra, ventra tegmentum
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2
Q

Corpus striatum= _________= ________

A

striatum= caudate plus putamen

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3
Q

Where does the caudate extend into? What nucleus does it include

A

Head, body & tail extend into temporal lobe

Nucleus accumbens= ventral & anterior portion of caudate

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4
Q

What is the putamen separated from and by what?

A

separated from caudate by internal capsule (passes through windows b/w cell bridges)

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5
Q

What are the two globus pallidi and where are they in relation to putamen?

A

internal & external; medial to putamen

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6
Q

What is the subthalamus?

A

midbrain nucleus that interconnects w/globus pallidus

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7
Q

What structure contain pigmented cells & project to striatum?

A

substantia nigra, pars compacta (SNpc)

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8
Q

Why is the substantia nigra pars reticulata similar to GPi?

A

they both receive striatal input & inhibit thalamus via GABA in pathway

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9
Q

The basal ganglia form a _____

A

FEEDBACK LOOP

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10
Q

Motor/cognitive cortical programs are funneled through what?

A

striatum & globus pallidus

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11
Q

Globus pallidus projects to _____ which in turn conveys info back to _____ motor & _______ programs

A

thalamus, frontal cortex, refine cognitive

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12
Q

What are the roles of the substantia nigra and subthalamus in this loop?

A

both modulate loop activity to select or reinforce certain motor/cognitive outputs

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13
Q

What is used to excite and thus balance the activity of direct & indirect pathways in relation to motor/cognitive outcomes? What about to inhibit it?

A 
excitatory= gluatmate
inhibitory= GABA
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14
Q

What structure inhibits motor/behavioral output of the thalamus & cortex?

A

internal globus pallidus

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15
Q

What structures modulate impact of GPi on thalamus via direct or indirect pathways?

A

cortex, striatum & subthalamus

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16
Q

In relation to the cortex, striatum & subthalamus modulating the impact of GPi on the thalamus, what is the direct vs indirect pathway?

A

both are from the striatum
direct pathway goes to internal GB & facilitates behavioral responses
indirect pathway goes through external GP & subthalamus then depresses behavioral responses
*they are antagonists to e/o

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17
Q

How does the direct pathway of motor/cognitive modulation work?

A

cortex activates striatal neurons–> inhibit GPi–> less inhibition of thalamus by GPi= more activity in cortex= more movement!

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18
Q

How does the indirect pathway of motor/cognitive modulation work?

A

cortex activates different set of striatal neurons–> inhibit GPe
STh activates GPi to inhibit thalamus but GPe inhibits STh
disinhibition of GPi= general inhibition of thalmo-cortical activity

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19
Q

To determine onset, offset & scaling movements the striatal output does what 2 things?

A

permits intended movements (inhibits parts of GPi via direct path)
inhibits unintended movements (increasing GPi activity via indirect path)

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20
Q

What neurotransmitter activates direct & indirect pathways?

A

DOPAMINE!

activates pathway via D1 type DA receptors and inhibits indirect pathway via D2 type DA receptors

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21
Q

Where does dopamine come from? Where does it this structure project axons to to regulate direct & indirect pathways?

A

substania nigra; it projects axons to striatum

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22
Q

Besides activating or inactivating pathways how else does DA regulate direct & indirect pathways?

A

increases signal-to-noise ratio in striatum= enhances strong inputs & suppresses weak ones

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23
Q

By balancing direct & indirect pathways, what does this lead to in relation to DA?

A

this organizes & builds internally generated behaviors= can be reinforced by DA= become stereotypic behaviors

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24
Q

The distinct loops formed by the cortex, basal ganglia & thalamus allow what? What 4 things are these reliant on?

A

parallel processing of affective, cognitive & motor components of behavior
vision, motivation, execution, motor/premotor

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25
Q

What makes up the motivational loop?

A

vmPFC, orbitofrontal & anterior cingulate cortex, amygdala, hippocampus & all of them projecting onto nucleus accumbens/ventral striatum

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26
Q

What does the motivational loop do?

A

regulates motivational-emotional aspects of behavior
translates motivation into action by transferring reinforcing signals to motor & executive cortico-striage loops= habits form

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27
Q

What makes up the executive loop?

A

dorsolateral PFC & association cortices which project to caudate

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28
Q

What form of memory is involved in the executive loop?

A

working memory

29
Q

What is executive function?

A

selection of appropriate movements, allocation of attention, planning, organizing, regulating, monitoring of goal related behavior, switching behavior set
internally generated movements

30
Q

What makes up the motor/premotor loop?

Which three structures of the motor/premotor loop project updated info back to the same cortex?

A

primary, premotor, supplementary & somatosensory cortex which all project to putamen (putamen, GP & thalamus project updated programs back to same cortex)

31
Q

What is the motor/premotor loop for?

A

programming & initiation of internally generated movements

controls movement direction & scaling (hammering a nail)

32
Q

What makes up the visual loop?

A

extrastriate cortex (inferotemporal & fusiform gyrus) & projects to body & tail of caudate

33
Q

In the visual loop, where does the caudate project back to?

A

through globus pallidus & thalamus to visual & prefrontal cortex (esp executive portion)

34
Q

What does the visual loop form?

A

more elaborate visual categories (more elaborate than those of simple/complex cells in visual cortex)

35
Q

What does the visual loop do?

A

integrates visual input into declarative & procedural learning of tasks

36
Q

Visual info from visual association cortices is looped to where?

A

into body & tail of caudate & then back to cortex (reinforced by DA)
*pathways from visual to executive/motor loops is part of basis for learning to associate appropriate response w/each stimulus alternative

37
Q

What are the three types of memory?

A

declarative, emotional, procedural (non-declarative) memory

38
Q

Declarative memory: part of brain, what is it for?

A

hippocampus-limbic

episodic memories are stimulus-stimulus associations that are consolidated into semantic memory in cortex

39
Q

Emotional memory: part of brain, what is it for?

A

amygdala

fear conditioning by association of stimulus & aversion

40
Q

Procedural memory: parts of brain, what are the parts of the brain for procedural memory for?

A

cerebellum: combines learned movements to produce well-executed motor skill behavior
basal ganglia: habit formation= association of motor responses w/reinforcing stimuli to build repertoire of motor actions to be triggered by appropriate environmental stimuli

41
Q

What are the 4 characteristics of procedural memory?

A

are implicit, rigid, procedural &suitable to guide cue-based & egocentric navigation

42
Q

Parallel loops of procedural memory operate to facilitate what three things?

A

category representation
action selection
instrumental & reward learning

43
Q

What is category representation associated with?

A

stimulus categories derived from association sensory cortex & then linked to appropriate behaviors

44
Q

What is action selection?

A

loops select & group neuronal populations that focus on desired motor response

45
Q

What is instrumental & reward learning?

A

conditioning behavior to novel cognitive or emotional cues; task switching to more appropriate behavior, DA reinforced

46
Q

What is category representation crucial for?

A

SURVIVAL! essentially being able to tell not harmful from harmful; link determination to appropriate behavior

47
Q

Declarative visual categories depend on ____ & _____ regions involved in working memory & executive attention

A

hippocampus & prefrontal regions

48
Q

Declarative visual categorizing skills are usually attained within how many trials?

A

ONE

49
Q

Procedural visual categories depend on _____ using ______

A

visual cortico-striate loop, tail of caudate

50
Q

Visual cortico-striate loop of procedural visual categories branches to what two other loops and integrates w/what?

A

executive & premotor loops & integrates w/executive control

51
Q

How does action selection work?

A

phasic DA activity to striatum selects responses from motivational, executive & sensorimotor loops & combines them to form goals, actions & movements

52
Q

Instrumental learning involves ____ & action; ____

A

goal & action; stimulus reponses

53
Q

How do habits develop in relation to instrumental learning?

A

w/a shift from goal-directed action to stimulus-response association & behavior becomes inflexible

54
Q

What are the three DA pathways that project from midbrain (and where do they project to) and modulate behavior responses by associative learning & reinforcement?

A

nigrostriatal: SN projects to striatum
mesolimbic: ventral tegmentum projects to nucleus accumbens
mesocortical: ventral tegmentum projects to prefrontal cortex

55
Q

DA alter both _____ & _____ cells to increase their _______ which ______ corticostriatal connections & = conditioning of a stimulus to a motor pathway

A

presynaptic & postsynaptic; excitability; strengthening

56
Q

Before learning occurs, the mosaic of broken mirrors model allows for what?

A

association of any environmental cue w/any action!

57
Q

Under incorrect learning, inappropriate plasticity in indirect pathway leads to what?

A

inappropriate inhibition & diminished facilitation= talk-related elements become increasingly noisy & less distinct against background compared even to naive processing

58
Q

What is naive, pre-learned state?

A

processing through basal ganglia is undifferentiated

59
Q

Reward learning is condition by _____ instead of _____.

A

stimulus w/a reward or outcome rather than w/motor response itself

60
Q

Reward learning is mediated by what other loop?

A

motivational loop (vmPFC, orbitofrontal cortex & nucleus accumbens)

61
Q

The vmPFC receives info about what from what other regions?

A

info about ‘value’ of response from OFC, amygdala & hippocampus

62
Q

What is the OFC the majory sensory cortex for?

A

taste & small, affective aspects of touch & temp, & vision

63
Q

What neurons located where respond to food, water & success?

A

mesolimbic dopamine neurons in ventral tegmentum

64
Q

What interacts to provide top down reward & reinforcement along successive spiraling connections?

A

three frontal loops (motivational to executive to motor loops of basal ganglia)

65
Q

In learning a task subjects use _____ & _____ loops to learn through following instructions

A

motivational & executive

66
Q

New instructions initiate what?

A

prefrontal activity again

67
Q

External stimuli stimulates what? What is it associated with?

A

stimulates mostly sensorimotor loop & are associated w/willful behavior

68
Q

Internal triggers stimulate what? And are associated with what?

A

activity mostly in associative & limbic loops & associated w/motivationally derived behavior

69
Q

Predominance of motivation-based, internally cued actions leads to what?

A

actions that are repetitive, internally guided, aimless, resistant to interferenceby external stimulus= stereotypic= TOURETTE’S SYNDROME

OS III (12 decks)

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