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Unit 4 > Limbic System > Flashcards

Limbic System Flashcards

1
Q

Le Grande Lobe Limbique

A
  • Described by Broca
  • Cortical areas forming a rim around the diencephalon on the medial surface of the brain
  • Cingulate cotex, parahippocampal gyrus, olfactory cortex
  • Originally though to have primary role in olfaction
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2
Q

Papez Circuit

A
  • James Papez hypothesized the limbic system is involved in emotions
  • Components: Hippocampus connected to mammilary bodies (hypothalamus), mammilary bodies connected to the anterior nucleus of the thalamus, anterior nucleus connected to the cingulate cortex, cingulate cortex back to the hypothalamus
  • KEY missing part: amygdala
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3
Q

Klucy-Buver Experiment

A
  • Removal of temporal lobes of aggressive monkey

- Became docile, over ate, ate inappropriate things, hyperoral, hypersexual

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4
Q

Modern limbic system primary components

A

-Amygdala, anterior and mid-cingulate cortex, mediodorsal nucleus of thalamus, prefrontal cortex

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5
Q

Anterior cingulate cortex

A
  • Store emotional/valenced information and recode the amygdala
  • Involved in AFFECT
  • Stores long-term emotional memory
  • Operates through ANS projections to the nucleus of the solitary tract and dorsal motor nucleus of vagus
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6
Q

Mid cingulate cortex

A
  • Select responses (mental or motor), predict outcomes and resolve ambiguity, improvise new behaviors for new problems
  • Involved in motivated behavior and response selection
  • Anterior part activated during fear
  • Operates through spinal projections to the skeletomotor system
  • Projections to the striatum, red nucleus, pontine nuclei, and CN nuclei for somatomotor driving of Alpha motor neurons
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7
Q

Amygdala

A

-Invests sensory experience with emotional significance (valence), most prominently in fear

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8
Q

Hypothalamus

A

-Autonomic/hormonal control

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9
Q

Periaqueductal gray

A
  • Coordinate behaviors, autonomic/skeletal
  • Surrounds aqueduct in the midbrain between 3rd and 4th ventricle
  • Stimulating different parts produce different classes of behavior
  • Ventral area: rest and digest, dorsal: fight or flight
  • Has none of its own memory
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10
Q

Autonomic nervous system

A

-Skeletal motor output and memory enhancement

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11
Q

Locus Coeruleus

A
  • Coordinates responses and enhances storage of emotional memories, helps to remember responses
  • Critical for fight or flight response
  • Located in pons
  • Extensive projections throughout the cortex, especially the limbic parts
  • Driven by input from the amygdala and limbic cortex
  • Releases norepi that is critical for storage of emotionally valenced memories
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12
Q

Dorsal Raphe Nucleus

A

-Helps to regulate mood, produces serotonin

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13
Q

Two types of emotion

A
  • Primary: fear, surprise. Reflexive emotions linked with autonomic reflexes (amygdala, hypothalamus, PAG)
  • Secondary: conscious emotions (cortical limbic structures and hippocampus)
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14
Q

Basal-lateral nucleus of amygdala

A
  • Input: thalamus, sensory, entorihinal, and association cortex
  • Output: cortex and striatum
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15
Q

Central nucleus of amygdala

A
  • Input: brainstem, sensory and prefrontal cortex
  • Output: brainstem and hypothalamus
  • Connects to basal lateral to mediate fear response
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16
Q

Urbach-Weithe Disease

A
  • Loss of amygdalas due to calcification (hippocampus left intact)
  • Example patient SM could not recognize fear
17
Q

Inputs to the amygdala

A
  • MGN
  • Auditory cortex
  • Thalamus
  • Receives primary and sensory input from all modalities
  • Direct input from thalamus critical to the role of the amygdala in fear response
18
Q

Primary emotion (fear) response steps

A
  • Fear evoking stimulus (visual)
  • Stimulus perceived
  • Input goes directly from LGN to the amygdala, activating fear response (activates cortex and output pathways)
  • Expression of fear somatically and viscerally through ANS activation
  • Memory of event encoded in the amygdala and cortex
  • Memory enhanced by presence of norepi for the LC
19
Q

Sham rage

A
  • Lesion to the hypothalamus/PAG can produce a rage without external control (primary emotion)
  • Activation of the lateral hypothalamus is the cause
  • So losing the descending control to PAG can be dangerous
20
Q

PAG projections

A

-Regulates projections to the nucleus of the solitary tract, dorsal motor nucleus of vagus, intermediolateral nucleus–activates ANS during emotional events

21
Q

HPAA Axis

A
  • Amygdala and limbic cortex and NE from LC cause paraventricular hypothalamic nucleus (PVN) to secrete cortisol releasing hormone (CRH) into portal veins.
  • CRH evokes release of ACTH from pituitary, then evokes release of cortisol from adrenal cortex
22
Q

Effects of the release of cortisol by adrenal cortex

A
  • Binds to glucocorticoid receptors
  • Increases glucose levels and metabolism
  • Increases AA metabolism
  • Increases fat breakdown
  • Increases memory (amyg, insula, acc)
23
Q

Reciprocal projections from amygdala to ACC

A

-Helps form the conclusion that the ACC is mainly involved in emotion and may be vulnerable to emotional diseases

24
Q

Different regions of cingulate activation with memory of emotional events

A
  • Fear: anterior MCC
  • Sadness: ventral ACC
  • Happiness: rostral ACC
25
Q

Electrical stimulation of MCC results

A
  • Complex motor outputs that are emotionally relevant

- Ex: lip puckering, finger kneading

26
Q

Site of emotional facial awareness and expression

A
  • Anterior cingulate cortex, called the facial region
  • Projects to the facial motor nucleus
  • Allows us to read each others emotions, also explains why we “wear our emotions on our sleeves”
27
Q

Points at which the LC intercedes in limbic systems to coordinate motor outputs

A
  • NTS/paraventricular nucleus in the thalamus mediates heart responses from ACC/central amyg
  • PAG: NE selects fight or flight
  • PVN drives HPA axis: NE, ACTH, Cortisol
  • Enhances amygdala processing and memory
28
Q

Disorders of the limbic system

A
  • Conduct disorders, sociopathies, mood disorders, neuropsychiatric disorders
  • Most prevent are depression and anxiety
29
Q

Evidence of limbic involvement in depression

A
  • Increased amygdala volume in depressed patients
  • Reduced glucose metabolism in ACC in major depression
  • Decreased ACC volume in patients with major depression
30
Q

Depression and 5HT in limbic system

A
  • Serotonin produced in raphe nucleus, near PAG
  • 5HT is an important modulator of mood through limbic pathways
  • Determines tonic activity of the system
31
Q

Deep brain stimulation

A
  • Targets the ACC
  • Can be used to treat depression
  • Long lasting effects

Unit 4 (17 decks)

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