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Brain and Behavior Exam 3 > Lec 40 Limbic System Anatomy > Flashcards

Lec 40 Limbic System Anatomy Flashcards

1
Q

What are the four main components of limbic system?

A
  1. limbic cortex [limbic lobe + prefrontal cortex]
  2. subcortical structs: amygdala, hippocampal formation, thalamic nuclei, habenular nuclei
  3. cholinergic cells of basal forebrain and septal nuclei
  4. DA reward paths
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2
Q

What is function of limbic system?

A

memory
emotion
motivational drive
homeostasis

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3
Q

What 4 structures comprise limbic lobe?

A
  • cingulate gyrus
  • isthmus
  • parahippocampal gyrus
  • subcallosal/subgenual gyri
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4
Q

What are the major functions of prefrontal cortex?

A
  • attention; concentration; executive control; cognition; planning; working memory; decision making

emotion; motivation; personality

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5
Q

What happens if damage to PFC?

A

behavioral disinhibition = individuals show exaggerated impulsivity and compulsivity

implicated in dementia and most psychiatric syndromes –> schizophrenia, depression, ADD

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6
Q

What is function of cingulum?

A

fiber bundle that contains major efferents from cingulate cortex

learn to correct mistakes + reinforce behaviors that reduce pain

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7
Q

What are the major outputs of cingulate cortex?

A
  • to subicular and entorhinal cortex [temporal lobe]
  • to association neocortex/ventral striatum/thalamic nuclei
  • to amygdala, hypothalamis
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8
Q

What is function of cingulate gyrus?

A

learn to correct mistakes/reinforce behaviors that reduce pain

–> receives pain/temp input from spinothalamic tract and outputs to temporal lobe

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9
Q

What is the entorhinal cortex?

A
  • inferior surface of parahippocampal gyrus

- major afferents to hippocampal formation pass through it

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10
Q

What are two main parts of the hippocampal formation?

A

hippocampus proper [ = cornu ammonis fields 1-4]

and dentate gyrus

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11
Q

What is the subiculum?

A

output structure of the hippocampal formation

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12
Q

What is function of hippocampus?

A

formation of new declarative memories [but not storage]

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13
Q

What happens if lesion of hippocampal formation?

A

anterograde amnesia = can recall old memories but can’t make new ones

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14
Q

What is contained in dentate nucleus?

A

granule cells

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15
Q

What is contained in CA region?

A

large pyramidal neurons

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16
Q

What type of neurons in main circuit of hippocampus?

A

glutamate

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17
Q

What is major input to hippocampal formation?

A

entorhinal cortex –> dentate gyrus

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18
Q

What does dentate gyrus project to?

A

CA3

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19
Q

What is path of internal processing of inputs to hippocampal formation?

A

entorhinal cortex –> dentate gyrus –> via mossy fibers to CA3 –> via shcaefer collaterals to CA1 –> to subiculum –> post-commissural fornix –> mammillary bodies

majority CA3 also:
–> pre-commissural fornix –> nucleus accumbens septi

20
Q

What are inputs to hippocampal formation via entorhinal cortex?

A
  • association cortices [limbic regions of temporal/frontal]
  • ACh from basal forebrain and septal nuclear region
  • subcortical inputs from amygdala and thalamus
21
Q

What are schaffer collaterals?

A

fiber system of CA3 collaterals that go to CA1

22
Q

What is major output structure of hippocampus? to where?

A

subiculum sends output via fornix to many areas [hypothalamus, mamillary, septal nuc. NAc, PFC]

23
Q

What is implicated in “timing” of memories?

A

adult hippocampal neurogenesis of granule neurons in the dentate gyrus

24
Q

Alzheimers is associated with degeneration of what input to hippocampal function?

A

azlheimers associated with degeneration of ACh neurons from septal nuclei that promote glu circuits in hippocampal formation

25
Q

What are limbic inputs to mammillary bodies of hypothalamus?

A
  • from subiculum via postcommissural fornix

- from VTA DA neurons

26
Q

What is main output from mammillary bodies?

A

to thalamus anterior group and MD

27
Q

What are major inhibitory and excitatory control of HPA axis?

A

inhibitory: hippocampus
excitatory: amygdala

28
Q

What happens to temporal lobe hippocampal formation in alzheimers?

A

atrophy

29
Q

What are symptoms of fronto-temporal dementia?

A

dramatic changes personality, socially inappropriate behavior, impulsivity, emotional indifference, language deficits

30
Q

What are hippocampal place cells? what happens if damaged?

A

cells responsible for cognitive map of external environment

trouble path finding, localizing self in external space

31
Q

Where do pre-commisure fornix projections from hippocampal formation go? what about post-commisure?

A 
pre-commisure = septal nuclei
post-commisure = mammillary bodies
32
Q

How does acute high glucocorticoids affect hippocampus?

A

enhances inhibitory control over HPA axis [negative feedback]

33
Q

how does chronic high glucocorticoids affect hippocampus?

A

damages hippocampus –> disruption feedforward HPA inhibition –> continued HPA output –> further hippocampal damage

this may be one mech by which sustained high level stress can increase risk for stress-related illnesses

34
Q

What is function of lateral habenula?

A

receives input from basal forebrain for mood regulation

sends outputs throughout limbic cortex, thalamus, hypothalamus, brainstem

35
Q

Where do mammillary bodies project?

A

thalamus [anterior group] –> which then project back to cingulate cortex

36
Q

What paart of brain degenerates in korsakov dementia?

A

mamillary bodies and anterior group of thalamus

37
Q

What is importance of ACh innervation from septal nuclei to hippocampus?

A

cognition as related to path finding

38
Q

What is the function of amygdala?

A

associative memory = associating neutral cue with reward or punishmnt = fear conditioning

39
Q

What is kluver-bucy syndrome?

A

bilateral lesion of amygdala leads to absence of fear, placidity, hyperphagia, hypersexuality

40
Q

What are outputs of amygdala?

A

basolateral amygdala –> PFC, hippocampus, striatum

central amygdala –> PAG, monoamine nuclei, HPA axis = major excitatory control of HPA axis = ANS

41
Q

What are two main output paths from amygdala?

A

ventral amygdalo-fugal path

stria terminalis

42
Q

What is function of ventral amygdalo-fugal path?

A

projects from amygdala to basal forebrain, hypothalamus, ventral striatum, thalamus

43
Q

What is function of the stria terminalis?

A

carries reciprocal connections between centromedial amygdala and hypothalamus

  • excitatory projection to HPA axis to regulate stress hormone response

project to hypo regions important for control of eating, sex, HPA

also projects to septal nuclei and thalamus

44
Q

What is function of bed nucleus of stria terminalis?

A

bed = sex

45
Q

What is the mesolimbic path? function?

A

DA path from VTA to nucleus accumbens septi [and amygdala, hippocampus, bed nucleus, septal nuclei] via MFB [median forebrain bundle]

function = responds to reward and punishment

VTA –> NAS –> VP –> MD

46
Q

What is the mesocortical path? function?

A

dopamine path from VTA to dorsal lateral prefrontal cortex, ventro medial prefrontal cortex, cingulate cortex, olfactory bulb

= cognition/motivation/emotional responses

Brain and Behavior Exam 3 (32 decks)

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