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HNNS > HNS48 Limbic System And Central Autonomic Function > Flashcards

HNS48 Limbic System And Central Autonomic Function Flashcards

1
Q

Emotion

A

Primary (reflexive): fear, anger, surprise, disgust, happiness, sadness

Secondary (cognitive): envy, shame, guilt

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2
Q

Emotion and reward

A

Emotional experience and ability to reflect upon our emotions:
—> Enrich sense of satisfaction, Guide actions

Rewards (Good / Bad):
—> Modulate emotions + Motivated behaviour

Emotions: mediated by Limbic system

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3
Q

***Limbic system

A

Interconnected brain areas:
Integrate information about sensory stimuli, memories, cognitive plans
—> Produce emotional learning + emotional experince

Diencephalon components:

  1. ***Anterior group of thalamic nuclei
  2. ***Hypothalamus
  3. Mamillary body (of Hypothalamus)

Cerebrum components:

  1. ***Cingulate gyrus
  2. ***Hippocampal formation (Hippocampus + Dentate gyrus + Subicular complex)
  3. Parahippocampal gyrus
  4. Entorhinal cortex

Other components:

  1. Fornix + Fimbria
  2. ***Amygdala (negative emotion)
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4
Q

Cannon-Bard theory of Emotion and Sham rage

A

Forebrain outflow pathway (Cerebral cortex) transected
—> Rage response (e.g. hissing, increased BP, HR) despite innocuous stimuli / no stimuli (Sham rage)
—> Animals retained emotional responses but responses lack aspects of emotional behaviour that was normally observed during rage
—> Sham rage also subside rapidly upon stimulus removal / undirected
—> animals may even bit themselves

Progressive transaction of Anterior / Posterior hypothalamus
—> NO coordinated rage response
—> Show that emotions are ***regulated in Hypothalamus

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5
Q

Limbic system anatomy

A

Limbic lobe (Initial emotion circuit):

  • **Ring (環狀) of “primitive” cortex around brainstem:
    1. Cingulate cortex
    2. Parahippocampal gyrus (Entorhinal cortex)
    3. Hippocampal formation (Dentate gyrus)
    4. Mamillary body (of Hypothalamus)
    5. Anterior nucleus of Thalamus
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6
Q

Functions of Emotions

A
  1. Internal feelings
  2. Behaviour patterns
  3. ***Autonomic control
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7
Q

***Papez circuit

A 
Cingulate gyrus (Emotional experiences)
—> Parahippocampal gyrus
—> Entorhinal cortex
—> Hippocampus (Dentate gyrus)
—> Fimbria
—> Fornix
—> Mamillary body (Emotional expression)
—> Mammillothalamic tract
—> Anterior nucleus of Thalamus
—> Cingulate gyrus (posterior)
—> Parahippocampal gyrus
—> Hippocampus

N.B.: NO Amygdala / Hypothalamus

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8
Q

***Paul MacLean: Amygdala + Hypothalamus

A

Extend neural circuits to include additional interconnected brain areas:

  • **Amygdala
  • Key coordinator
  • Linking Cortex to Hypothalamus + other subcortical brain structures
Proposed additional neural circuit for emotion (Maclean加埋Amygdala + Hypothalamus):
Emotion stimulus
—> Association cortex
—> Hippocampal formation (Hippocampus + Dentate gyrus + Subicular complex) OR Cingulate gyrus (Papez circuit)
—> ***Amygdala
—> ***Hypothalamus
—> ***Prefrontal cortex
—> Association cortex
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9
Q

Amygdala and Kluver-Bucy syndrome

A

Removal of temporal lobes including Amygdala (and Hippocampus) bilaterally
—> dramatic change in emotional behaviour

  1. Tame, fearless, “blunted” emotions
  2. Increased oral activity, placing inedible objects in mouth
  3. Increased sexual behaviour, mounting inappropriate objects

Subsequent studies:
- Stimulation of Amygdala can produce **fear and anxiety
- Imaging studies: show more activity in Amygdala when viewing expressions of fear
- Amygdala activated differentially by emotional facial expressions —> identify emotions (眉頭眼額)
- Amygdala respond to emotionally arousing stimuli (e.g. seeing a spider)
—> Conclusion: Amygdala is a **key structure in ***mediating emotional effects

  • **Temporal lobe ablation (木頭人):
    1. Loss of fear
    2. Less aggression
    3. Hyperorality
    4. Forget rapidly

Examples:

  1. Kluver-Bucy syndrome: Amygdala damage (reduces fear)
  2. Autistics have problems identifying emotions of other people (abnormal Amygdala)
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10
Q

***Neural pathways for emotional stimulus

A
  • Central component: Cerebral cortex (evaluative components of emotion)
  • Peripheral component: Hypothalamus (autonomic)

Pathway:
Emotional stimulus

—> ***Thalamus —>

  1. Direct pathway
    —> **Amygdala (—> Emotional responses)
    —> **    Hypothalamus + Brainstem nuclei
    —> Autonomic NS

OR

2. Indirect pathway
—> ***Cortex
—> ***Amygdala (—> Emotional responses)
—> ***Hypothalamus + Brainstem nuclei
—> Autonomic NS
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11
Q

Peripheral (Autonomic) control

A

Emotionally significant stimuli
—> Hypothalamus
—> act on Autonomic NS by modulating visceral reflex circuitry (organised at level of brainstem)
—> HR, BP, respiration changes

Hypothalamus:

  1. Autonomic control
  2. Internal homeostasis
  3. Motivation

(Many nuclei in Hypothalamus and each for specific function:

e. g.
- Posterior hypothalamus —> ↑ BP, pupil dilation, shivering
- Posterior preoptic / Anterior hypothalamic area —> body temperature, panting, sweating
- Dorsomedial nucleus —> GI stimulation
- Perfornical nucleus —> rage, hunger, ↑ BP)

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12
Q

Flow of information controlling Autonomic nervous system

A

Major descending inputs to Brainstem autonomic nuclei

  1. Amygdala
  2. Hypothalamus

Visceral sensation (sensory information esp. from visceral organs, taste receptors)
—> ***Solitary nucleus
—> Brainstem (+ Hypothalamus)
—> Brainstem nuclei
—> Preganglionic efferents
—> Sympathetic (T1-L2) + Parasympathetic (CN3, 7, 9, 10 + S2-4)

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13
Q

Feeding behaviour

A
  • **Lateral hypothalamus (Hunger / Feeding centre)
  • Set point + Internal drive for food intake
  • Lesions in lateral hypothalamus —> ↓ in food intake (Hypophagia)
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14
Q

***Septal region, Hypothalamus, Ventral tegmental area

A
  1. Septal region:
    Structure of Limbic system closely connected to Hypothalamus, Hippocampal formation, Amygdala
    —> **Pleasure centre
    —> part of Mesolimbic pathway (Dopaminergic)
    —> project to **    Nucleus accumbens (Rewarding, Addiction)

Electrical self-stimulation experiment:
- Stimulation of septal region
—> Pleasant sensation
—> rats continuously press bar to experience euphoric feeling

  1. Ventral tegmental area:
    Brain stimulation activates neurons in Ventral tegmental area (Midbrain, next to Substantia nigra)
    —> ***Dopamine neurons (forming most of Mesolimbic and Mesocortical pathway involved in reward)
    —> Dopamine release
    —> rats choose self-stimulation over food / sex
  2. Hypothalamus:
    Brain stimulation to parts of Hypothalamus (and related structures)
    —> ***Reinforcer
    —> work independently of drive state (e.g. hunger)
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15
Q

Ventral tegmental neurons and experiment

A

Wolfram Schultz:
Rewards can be learned to be expected (Reward predicted)
- even though the association between stimulus and reward is unknown initially

When reward is predicted —> VTA neurons fire

Conclusion:

  1. VTA neurons provide a learning signal that reflect reward expectation
  2. Cell’s firing rate is modulated when reward received differ from expectation

—> this learning signal can be used by other brain areas to

  1. Guide behaviour
  2. Modulate emotional responses to reward-predicting stimuli
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16
Q

***Drug abuse and addiction

A

Cocaine, Amphetamines:

  • ↑ dopamine release in brain esp. in shell of Nucleus accumbens
  • block dopamine reuptake transporter

Nicotine:
- ↑ dopamine release by acting on presynaptic cholinergic receptors

Nucleus accumbens shell:
receives Dopaminergic input from VTA (midbrain dopamine neurons)
—> project to Hypothalamus + Limbic structure
—> mediate emotional responses

17
Q

Self-stimulation experiment

A

Cocaine and nicotine:
- ↑ rate of self-stimulation by rats for a given stimulation frequency compared to baseline

Conclusion:
Cocaine and nicotine enhance pleasure produced by self-stimulation

18
Q

***Brain reward circuitry and self-stimulation

A
  • **Medial forebrain bundle:
  • Descending myelinated fibres innervating VTA
  • most effectively site for stimulation
  • activates VTA directly

Different drugs can intervene at different levels of brain-reward circuitry:
Amphetamine, Cocaine, Nicotine, Opiates, Ketamine —> act on Nucleus accumbens

19
Q

Monoamine and Emotion

A

ALL in brainstem

  1. Dopamine (VTA, Substantia nigra):
    - **Reward (motivation)
    - **    Pleasure, euphoria
    - ***Motor function (fine tuning)
    - Compulsion
    - Perseveration
  2. Serotonin (Raphe nucleus):
    - ***Mood
    - Memory processing
    - Sleep
    - Cognition
  3. Norepinephrine (Locus coeruleus)

Others: ACh (Basal forebrain)

20
Q

Major depression

A

Based on Diagnostic and statistical manual of mental disorder (DSM-5)

  1. Anxiety, ↓ mood
  2. Anhedonia (lack of pleasurable feeling)
  3. Insomnia / hypersomnia
  4. Fatigue
  5. Appetite changes
  6. ↓ Motivation
  7. Worthlessness
  8. Suicidal thought

60% of patients inadequate response to pharmacological / deep brain stimulation / talk therapies

21
Q

Monoamine hypothesis of depression

A

Depression caused by low levels / deficit in functions of NT

22
Q

Anxiety

A

Lower-grade form of fear, generalised and often non-referential (being afraid of nothing in particular but still feeling the nervousness)

  1. Panic disorder
  2. GAD
  3. PTSD
  4. Social phobia / social anxiety disorder
  5. Simple phobias
  6. OCD
23
Q

Psychosurgery - Deep brain stimulation

A

Surgical treatment involving implantation of brain pacemaker
—> send electrical impulses to specific part of brain
—> modulate neural transmission by:
1. ↑ / ↓ firing of neurons
2. ↑ / ↓ neurogenesis

24
Q

***Mesolimbic pathway and Mesocortical pathway

A

Mesolimbic pathway:
VTA —> ***Nucleus Accumbens —> Hypothalamus + Limbic structure —> mediate emotional responses

Mesocortical pathway:
VTA —> ***Prefrontal cortex

HNNS (58 decks)

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