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Neurology Week 3 > 23B: Limbic > Flashcards

23B: Limbic Flashcards

1
Q

Where is the limbic lobe?

A

-surrounds the lateral ventriccles

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2
Q

What are the parts of the limbic lobe?

A

cingulate gyrus

subcallosal gyrus

parahippocampal gyrus

hippocampal formation

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3
Q

What is the main function of the limbic lobe?

A

emotion (amygdala especially) and cognition (more hippocampus)

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4
Q

What are the roles of the amygaloid nuclei?

A

important for regulating emotions and autonomic function, as well as olfaction

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5
Q

Where are the amygdaloid nuclei located?

A

anterior temporal lobe, just anterior to the hippocampal formation (basically at the level of the anterior termination of the inferior horn of the lateral ventricle)

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6
Q
A

Amygdala- note that it is composed of several nuclei, not all of which are functionally related

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7
Q

What are the three main groups of amygdaloid nuclei?

A

-Corticomedial (Co: the olfactory part)

Central (C: the principle output nucleus; striatum-like in structure; important for autonomic control)

Basolateral: (the principle input nucleus; associated with neocortex and thalamus; B= basal; L= lateral)

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8
Q

What does the corticomedial amygdaloid nuclei group include?

A

anterior, medial, and cortical nuclei

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9
Q

What does the central amygdaloid nuclei group include?

A

has a close relationship with the striatum

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10
Q

What is the main cell type in the central amygdaloid nucleus?

A

medium spiny GABAergic neurons with a high density of dopamine containing axons

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11
Q

What does the basolateral amygdaloid nuclei group include?

A

basal, lateral, and accessory basal nuclei (this is the largest, best differentiated nucleus in the human body)

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12
Q

What are the main neurons in the basolateral amygdaloid nuclei group?

A

pyramidal cells (glutamatergic), similar to neocortex and hippocampus

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13
Q

What is the major input into the corticomedial nucleus?

A

mainly from the olfactory bulb (this is aka the olfactory amygdala)

also from the parabrachial nucleus (a taste processing nucleus), and the medial dorsal (MD) and ventromedial (VM) thalamus

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14
Q

What is the major output from the corticomedial nucleus?

A

hypothalamus via the stria terminalis and back to the olfactory bulb

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15
Q

What is the major input into the central nucleus?

A

basolateral nuclei of the amygdala and from the hypothalamus

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16
Q

What is the major output from the central nucleus?

A

to the brain stem nuclei and hypothalamus (regulate autonomic systems), and

the striatum and midline (non-specific) thalamic nuclei (effects on arousal)

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17
Q

What is the major input into the basolateral nucleus?

A

input from many areas of association cortex (including highly processed sensory info)

olfactory cortex

thalamus

hippocampal formation

septal area

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18
Q

What is the major output from the basolateral nucleus?

A

mainly to the central nucleus of the amygdala

some to the hypothalamus

many areas of the cortex (prefrontal)

thalamus (especially dorsomedian, DM)

reward circuits in the nucleus accumbens and striatum

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19
Q

How does the basolateral amygdala project to the hippocampal formation?

A

entorhinal cortex (ERC) and subiculum

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20
Q

What is the main function of the central amygdaloid nucleus?

A

autonomic control (e.g. blood pressure, heart rate), arousal, and subjective experience

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21
Q

Again, the amygdala is considered crucial for regulating what emotions?

A

emotional and social behavior (different responses seen in different animals)

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22
Q

How do bilateral amygdala lesions present in animals (monkeys)?

A
  • hypersexual
  • tame
  • lack of fear to predators
  • feeding disorders (if the basolateral is lesioned, the animals have hyperphagia; if the central nucleus is lesioned, they have hypophagia and starve)
  • hyperorality (put things in their mouth)
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23
Q

Bilateral loss of the anterior temporal lobe is called what?

A

Kluver-Bucy syndrome (rare)

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24
Q

How does Kluver-Bucy syndrome present?

A

pts are hypersexual,

overly oral,

tame,

exhibit hyperphagia,

are hyperactive, and

express psychic blindness (they dont recognize the emotional content of facial expressions)

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25
Q

What is Urbech-Wiethe disease?

A

This disease results in clacification of neural tissue (can be the amygdaloid nuclei) resulting in the patient being bad at recognizing faces expressing FEAR (this inhibits one’s to act appropriately toward others)

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26
Q

Note that the amygdala, especially the _______ nuclei is thought to control fear response

A

basolateral

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27
Q

The basolateral nuclei is also important for:

A

the emotional component of learning and memories

28
Q

Where is the hippocampal formation found?

A

within the temporal lobe, posterior and inferior to the amygdala (telencephalon)

close to the inferior horn of the lateral ventricle (the formation is medial and superior to the ventricle)

29
Q

What is the alveus?

A

the collected axons of the hippocampal pyramidal cells

30
Q

The collected axons of the hippocampal pyramidal cells, aka the alveus, collect and form ________

A

the fimbria, which turn becomes the fornix

31
Q
A
32
Q

Much of the gray matter in the parahippocampal gyrus is what?

A

the entorhinal cortex (mesocortex), with characteristic deep white matter and superficial grey matter

33
Q

What are the main components of the hippocampal formation?

A

subiculum

the CA fields (CA1-4) (considered the hippocampus proper)

dentate gyrus

34
Q

What are the two major input pathways of the hippocampal formation?

A

the ‘perforant’ pathway’ from the lateral entorhinal cortex

‘alvear’ pathway from the medial entorhinal cortex

note the fine cell bodies of the granular cells that are in the dentate gyrus

35
Q

Golgi-filled neuron types in each part of the hippocampal formation. Note the fornix at the bottom of the picture

A
36
Q

What are the principle cells in the entorhinal cortex (ERC)?

A

pyramidal cells (glutamergic, excitatory)

37
Q

What are the principle cells in the subiculum and CA (“Cornus Ammoni”) fields?

A

pyramidal cells (glutamatergic, excitatory)- note the numerous dendritic spines (primary site of excitatory inputs)

Below: Golgi stain on left; photomicrograph of fluorescence filled cell to show spines and apical dendrites on right)

38
Q

What are the principle cells in the dentate gyrus?

A

small granule cells (glutamatergic, excitatory)

39
Q

The _______ are considered the hippocampus proper

A

CA fields

40
Q

coronal section of the hippocampus

A
41
Q

The cellular distributions of all of the hippocampal formation subregions are highly laminar and regular. Describe the CA fields and subiculum

A

they are considered to be 3 layered allocortex (with molecular, pyramidal, and polymorphic layers).

The molecular layer is cell poor, the pyramidal cell layer contains the cell bodies of the principle, pyramidal neurons, and the polymorphic layer contains many cell types (mainly interneurons)

42
Q

Describe the dentate gyrus composition

A

also 3-layer (molecular, granular, and polymorphic)- note the granular difference (no pyramidal cells)

43
Q

What is the main input into the dentate gyrus?

A

from the entorhinal cortex

44
Q

What is the main output from the dentate gyrus?

A

to CA3

45
Q

Describe the trisynaptic circuit

A

1) Main input to the hippocampal formation is an excitatory (glutamatergic) projection from the entorhinal cortex to granule cells in the dentate gyrus (perforant path)
2) Granule cells in the dentate gyrus project (excitatory, glutamatergic) to CA3 pyramidal cells via mossy fibers
3) CA3 pyramidal cells project (excitatory, glutamatergic) to CA1 pyramidal cells via Shaeffer collaterals

46
Q

What is the Alvear path?

A

alternative to the trisynaptic circuit, in which the ERC projects directly to CA1

47
Q

What is another source of input into CA fields?

A

CA1 and CA3 both receive inputs and project to the septal nuclei and the contalateral hippocampus (via commissural fibers)

48
Q

All areas involved in the trisynaptic circuit receive modulatory input from where?

A

brain stem nuclei containing nor, serotonin, and ACh

49
Q
A
50
Q

Almost all inputs to the hippocampal formation come via where?

A

the entorhinal cortex

51
Q

Almost all output from the hippocampal formation goes where?

A

the subiculum (which projects widely throughout the cortex)

52
Q
A
53
Q

The hippocampus receives highly processed info about most our existence. How?

A

the entorhinal cortex receives inputs from widespread areas of cortex, thalamus, and brainstem

54
Q

Hippocampal pyramidal cells (especially CA1) are highly susceptible to many insults, including:

A
55
Q

As in the neocortex, the less numerous _____________ play an important role in downregulating excitability in the hippocampus

A

GABAergic inhibitory interneurons

56
Q
A
57
Q
A
58
Q

The hippocampal formation is very important for certain forms of learning and memory. What kinds in particular?

A

spatial learning and spatial memories (possibly via “place cells”, whose activity is related to positioning and orientation in relation to the external environment)

59
Q

What is declarative memory?

A

available to the conscious mind and the materal can generally be encoded in language. The hippocampal formation is essential for the formation of declarative memories

60
Q

What is implicit memory?

A

not available to the conscious mind. Note that there are several types of implicit memories, such as priming, muscular conditioning, emotional memory, and procedural memory (aka riding a bike, playing an instrument, complex motor action, etc.)

61
Q

What is priming?

A

a process whereby subjects show improved performance on tasks for which they have been subconsciously prepared.

62
Q

The ______ and ______ are crucial for implicit memory formation

A

basal ganglia and cerebellum

63
Q

The ________ is essential for the emotional content of memories

A

basolateral amygdala

64
Q

Where are most long-term memories stored?

A

neocortex, although the hippocampus may be necessary for recall (projections from the subiculum to widespread areas of cortex may be the substrate for distribution and storage of long-term memories)

65
Q
A
66
Q

In addition to the hippocampal formation, damage to what other structures results in memory deficits?

A

midline thalamic and hypothalamic structures (e.g. mammillary bodies, also fornix)

Neurology Week 3 (8 decks)

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