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IMS: Neuroanatomy > Limbic System > Flashcards

Limbic System Flashcards

1
Q

Limbic System

Structures

A

Consists of interconnected cortical and subcortical brain structures:

  1. Limbic lobe:
    • uncus
    • parahippocampal gyrus
      • formation of spatial memory
    • cingulate gyrus
      • autonomic functions
      • pain related emotions
      • cognitive and attentional processing
    • hippocampus
      • consolidation of long term memories
    • amygdala
      • emotion, aggression, fear
    • medial temporal gyrus
  2. Orbitofrontal cortex
    • emotion, memory, decision making
  3. Anterior insular cortex
  4. Thalamus
    • medio-dorsal nucleus
    • anterior nucleus
  5. Hypothalamus
    • regulation of ANS via hormones
    • ∆ BP, HR, hunger, thirst, sexual arousal, sleep/wake
    • Mammillary bodies
      • ​formation of memory
  6. Septum
  7. Nucelus accumbens
    1. ​reward, aversion, pleasure, addiction
  8. Ventral pallidum
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2
Q

Papez Circuit

A

Areas involved in expression and experience of emotion.

Added hippocampus, anterior nucleus of thalamus, most of hypothalamus, and mammillary bodies in addition to limbic structures.

Hippocampus → bodily expression of emotion.

Limbic system → mediating autonomic functions.

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3
Q

Limbic System

Circuits

A

Involved in memory, emotion, reward, motivation, goal directed behavior, and various autonomic functions.

3 most important circuits:

  1. Memory circuit
    ⟾ involves hippocampus
  2. Emotion circuit
    ⟾ involves amygdala
  3. Reward circuit
    ⟾ involves nucleus accumbens and ventral tegmental area (VTA)

Extensive reciprocal connections between circuits.

Dysfunction associated with psychiatric disorders including schizophrenia, OCD, anxiety, depression, PTSD, and mania.

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4
Q

Memory

Definition

A

Memory = ability to store, retain, and retrieve information.

Divided into short term/working memory & long term memory.

Long term memory subdivided into declarative and procedural memory.

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5
Q

Short-term / Working Memory

A
  • recall of recent events for a short time
  • recall of moment-to-moment results of mental processing
  • recall of info needed to accomplish a specific task
  • prefrontal cortex plays a central role
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6
Q

Declarative Memory

A

The ability to store and recall info for days, years, or lifetime.

Type of long term memory:

  • Explicit / Declarative
    • memory of facts and events
    • prefrontal cortex → working memory buffer
    • hippocampus involved in consolidation
    • Also involves MD thalamus, basal forebrain, other limbic structures
    • storage spread over associative cortical areas
    • storing and recalling is conscious
    • episodic memory → specific moment in time and place
    • semantic memory → fact knowledge without context
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7
Q

Procedural Memory

A

The ability to store and recall info for days, years, or lifetime.

Type of long term memory:

  • Implicit / Non-declarative / Procedural
    • memory for procedures and abilities
      • motor skills
      • habits
      • conditioning
      • emotional association
      • priming
    • storing and recalling is unconscious
    • dependent on striatum, cerebellum, amygdala, brainstem, spinal motor outputs, and neocortex
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8
Q

Memory Classification

Summary

A
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9
Q

Anmesia

A

A loss or disruption of memory.

Divided into 2 components:

  1. Anterograde amnesia:
    • impaired memory for info acquired after onset of memory loss
  2. Retrograde amensia:
    • impaired memory for info acquired before onset of memory loss
    • less common
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10
Q

Hippocampus

Overview & Blood Supply

A
  • C-shaped in horizontal and coronal sections
    • hippocampus proper named Ammon’s horn
  • Blood supply
    • mainly from posterior cerebral artery
    • hippocampal head partly from anterior choroidal artery
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11
Q

Hippocampus

Location

A

Found in medial surface of temporal lobe next to inferior horn of lateral ventricle.

Anterior end near amygdala.

Caudal end near splenium of corpus callosum.

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12
Q

Hippocampus

Efferents

A

Hippocampal pyramidal neurons:

  • Axons exit via fimbria of fornix
  • Curve around and continue as crus and body of fornix
  • At anterior commissure, fibers split into pre and post commissural fibers
  • Precommissural fibers → septum
  • Postcommissural fibers → descend ventrally as columns of fornix → mammillary bodies
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13
Q

Hippocampus

Structures

A

Hippocampal formation refers to 3 structures:

  1. Hippocampus proper (Cornu Ammonis)
  2. Dentate gyrus
  3. Subiculum​

Hippocampus proper and dentate gyrus arranged as 2 interlocking C-shaped structures in cross section.

Contains rows of glutamatergic pyramidal cells and sparse GABAergic interneurons.

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14
Q

Hippocampus Proper

(Cornu Ammonis)

A

Divided into 4 Cornu Ammonis areas:

CA1, CA2, CA3, and CA4

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15
Q

Hippocampus

Layers

A

Entorhinal cortex (neocortex) contains 6 layers.

Hippocampus proper and dentate gyrus (archicortex) contains 3 layers.

Transition occurs within subiculum.

  • Hippocampus proper:
    • polymorphic layer
    • pyramidal layer
    • molecular layer
  • Dentate gyrus:
    • polymorphic layer
    • granular layer
    • molecular layer
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16
Q

Hippocampus

Molecular Layer

A

Molecular layer is most superficial layer in entorhinal cortex (neocortex).

Becomes deepest layer in hippocampus proper.

Returns to most superficial layer in dentate gyrus.

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17
Q

Hippocampus

Polymorphic Layer

A

Polymorphic layer is deepest layer within neocortex.

Considered an output layer.

Becomes most superficial layer in hippocampus proper.

Returns to deepest layer in dentate gyrus.

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18
Q

Hippocampus

Internal Loop

A

Information to be consolidated into long term memory:

cortical association areas → entorhinal cortex → internal circuit loop

1) Entorhinal cortex via perforant path ⟾ dentate gyrus granule cells
2) Dentate gyrus granule cells via mossy fiber system ⟾ CA3 pyramidal neurons
3) CA3 via Schaffer’s collaterals ⟾ CA1 pyramidal neurons ⟾ subiculum
4) Subiculum ⟾ entorhinal cortex & cortical association areas for storage

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19
Q

Hippocampus

External Loop

A

Pyramidal neurons in CA3, CA1, and subiculum receive inputs from entorhinal cortex.

Send axons in alveus which exit to form fornix

Fornix ⟾ septum and mammillary body

Mammillary body via mammillothalamic tract (MTT) ⟾ anterior nucleus of thalamus

⟾ cingulate gyrus

⟾ entorhinal cortex and cortical association areas for storage.

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20
Q

Memory Consolidation

A

Involves hippocampus, entorhinal cortex, and various medial temporal structures.

Process unclear but classic hypothesis:

  • structures temporarily store complete copy of memory
  • memory gradually duplicated over time to various neocortical storage sites
  • temporal lobe lesion ⟾ anterograde amnesia
    • some retrograde amnesia seen
      • info still in medial temporal region at time of lesion lost
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21
Q

Spatial Memory

A

Hippocampus likely involved in storing and processing spatial memory.

  • Rodents:
    • Hippocampal neurons called “place cells” have spatial firing fields
      • as animal moves along circular track, different cells fire at different locations
      • creates a spatial or contextual map
      • serves as framework for event memories created in that environment
  • Humans:
    • Also have place cells
    • hippocampus most activated during learning and recalling of specific routes
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22
Q

Flashbulb Memory

A

Highly detailed, exceptionally vivid “snapshot” of the moment and circumstances in which a piece of surprising and consequential new was heard.

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23
Q

Hippocampus

Long Term Potentiation

A

LTP extensively studied in hippocampus.

Model of synaptic plasticity and sustained ∆ in neural transmission.

Likely cellular basis of memory formation.

LTP results from high frequency stimulation of afferent pathways:

  • Perforant path (PP) ⟾ granule cells of dentate gyrus
  • Mossy fibers (MF) ⟾ pyramidal cells of CA3
  • Schaffer collaterals (SC) ⟾ CA1 in hippocampus proper

Causes long-lasting ↑ in synaptic strength.

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24
Q

Hippocampal Lesion

A

Results in Kluver-Bucy Syndrome

  • Anterograde amnesia
    ⟾ inability to transfer new short-term memory into long term memory
    • explicit or declarative memory affected
      • semantic memory ⟾ conscious memory of facts
      • episodic memory ⟾ conscious memory of events
  • Short-term or working memory intact
    • can keep info in memory for several seconds
  • Implicit or non-declarative memory intact
    • can form motor skill, pattern recognition, habits, conditioning, emotional association, priming
    • retain learning for as long as normal subjects
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25
Q

Hippocampus

in

Alzheimer’s Disease

A
  • hippocampus among 1st damaged
  • memory problems and disorientation among 1st symptoms
  • CA1 region particularly affected
    • extracellular plaques
    • intracellular tangles
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26
Q

Hippocampal

Ischemia

A

Hypothalamus very susceptible to ischemia.

Selectively attacks CA1.

See pyramidal cell death d/t ischemia or stroke.

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27
Q

Hippocampus

&

Seizures

A

Hippocampus very electrically excitable.

Often the focus of epileptic seizures.

Presence of strong glutamatergic transmission contributes.

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28
Q

Temporal Lobectomy

Rhesus Monkeys

A
  • Results in:
    • visual agnosia ⟾ psychic blindness
    • oral tendencies ⟾ examine surroundings with mouths
    • hypermetamorphosis ⟾ compulsion to explore
    • emotions dulled
    • loss of normal fear
    • placidity
    • hypersexuality
  • Herpes simplex encephalitis most common cause in humans
    • visual agnosia, hypersexuality, loss of fear/anger
    • anterograde amnesia
    • dementia
    • distractibility
    • seizures
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29
Q

Korsakoff’s Syndrome

A

Brain disorder caused by chronic alcoholism, malnutrition, and thiamine (B1) deficiency.

Likely damages medial thalamus, hippocampus, and mammillary bodies.

Major symptoms:

  • anterograde amnesia
  • retrograde amnesia
  • confabulation ⟾ making up stories

Often occurs along with Wernicke encephalopathy:

  • ataxia
  • confusion
  • vision changes
30
Q

Memory Circuit

Summary

31
Q

Cortical Association Areas

A

Interacts with parahippocampal region for memory formation but mechanism unclear.

Prefrontal cortex

Temporal lobe

Parietal lobe

Cingulate gyrus

Olfactory bulb

32
Q

Amygdala

Functions

A
  1. attaching emotional significance to incoming stimuli
  2. form/store implicit (non-declarative) memory associated with emotional events
  3. unconscious emotional responses
  4. conscious feelings
  5. modulation of attention
  6. involved in explicit memory via processing of emotional meaning
33
Q

Amygdala

Altered Function

A

∆ in amydala function associated with:

  • stress
  • psychiatric conditions
    • anxiety disorders ⟾ PTSD, phobias, panic
    • depression
    • schizophrenia
    • autism
34
Q

Amygdala

Damage

A

B/l temporal lobectomy ⟾ ∆ emotional behavior

tame and fearless

Animals ⟾ loss of fear conditioning

Humans ⟾ impaired perception of emotional stimuli & emotional expression

Electrical stimulation in humans ⟾ feelings of fear and apprehension

35
Q

Amygdala

Location

A

Small almond-shaped subcortical structure.

Buried in anterior-medial portion of temporal lobe.

Near anterior end of hippocampus.

Found beneath uncus in CS @ thalamus.

36
Q

Amygdala

Nuclei

A

Deep group ⟾ responsible for collecting input from sensory corticies.

  1. Lateral nucleus (LA)
    • major input nucleus for sensory info
  2. Basal nucleus (B)
    • major input nucleus for contextual info from hippocampus
  3. Accessory basal nuclei

Dorsal group ⟾ receives projections from deep group & sends signal out to autonomic centers.

  1. Central nucelus (CE)
    • main output nucleus
  2. Medial nucleus
37
Q

Amygdala

Afferents

A

Receives 5 main types of input:

  1. Olfactory input
  2. Sensory input from sensory thalamic relay nuclei
    • vision, audition, gustation, somatosensation
  3. Contextual input from hippocampus
  4. Cortical input
  5. Visceral sensory input from hypothalamus and brainstem
38
Q

Amygdala

Efferents

A

Must be able to control ANS.

Projects to hypothalamus and brainstem autonomic centers incuding vagal nuclei and SNS neurons.

Fibers leave via 2 main pathways:

  1. Stria terminalis (ST) ⟾ hypothalamus
  2. Ventral amygdalofugal pathway (VAFP) ⟾ hypothalamus & MD thalamus

Also involved in mood and conscious emotional response to an event.

Has projections to cortical areas, hippocampus, medial striatum.

39
Q

Amygdala

Input Pathways

A

Visual, auditory, gustatory, and somatosensory inputs to amygdala via 2 pathways:

  1. Short route:
    • sensory thalamus (VPL, VPM, LGN, MGN) directly to amygdala
    • shorter and faster
    • provides low-level info about objects and events (crude representation)
    • designed to start fight-or-flight response
    • info processed at unconscious level
  2. Long route:
    • sensory thalamus ⟾ sensory cortex ⟾ amygdala
    • slower d/t processing time
    • provides more complex and accurate info
    • confirms or denies a threat

Entire process occurs unconsciously.

Involves implicit processing and implicit learning.

Olfactor inputs directly from olfactory bulb and olfactory cortex.

40
Q

Fear System

A

Amygdala works at subconscious level:

  • identify potential threats
  • initiate behavioral responses and autonomic reactions
  • freeze, fight, or flight
  • increases likelihood of surviving danger

1. See a spider

2. Info ⟾ thalamus

3a. Short route:

  • crude representation of potential danger ⟾ amygdala
  • lateral nucleus ⟾ central nucleus
  • info processed subconsciously
  • many outputs:
  • hypothalamus, memory center, motor structures, reflex centers
  • recognized as a threat (implicit memory store)
  • fight-or-flight response initiated

3b. Long route:

  • crude representation ⟾ visual cortex
  • quality of representation improved d/t processing by primary and associative cortical areas (what & where regions)
  • more complex and accurate representation of object ⟾ amygdala
  • if threat confirmed, fight-or-flight strategy persued
41
Q

Associative Emotional Learning

A

Learn by associating situation, object, or event with an emotional experience.

Associative process for emotional memories occurs in amygdala.

Involves LTP-related synaptic plasticity.

Lesion of amygdala ⟾ loss of fear conditioning.

42
Q

Modulation of Explicit Memory

A
  • Events linked to strong negative emotional experience are better recalled
  • Amygdala facilitates hippocampal consolidation of explicit memories tied to emtional situations
  • Too much stress ↓ explicit memory performance
    • maybe d/t stress hormones
      • disrupts hippocampal and prefrontal pathways
      • enhances amygdala’s contribution to fear
43
Q

Emotional Memory Storage

A

Emotional implicit memories (e.g fear) stored:

  • directly in amygdala
  • in adjacent regions requiring amygdala for access

Amygdala lesions abolishes emotional component of learned fear responses.

44
Q

Face Fearfulness

A
  • Amygdala response ↑ as fearfulness ↑ and happiness ↓
    • extract expression from eye shape
  • Perceive fearful expression faster than neutral or happy face
    • happy face signals safety
    • do not need immediate action
45
Q

Urbach-Wiethe

Disease

A
  • Genetic disease causing b/l calcification & atrophy of anterior-medial temporal lobes
  • Results in b/l destruction of amygdala
  • Presenation:
    • pt judges face showing fear to be much less intense
    • unable to link visual representations of facial expressions with fear emotion
    • no motor/sensory or intellect ∆
    • no declarative memor ∆
    • no language function ∆
    • no difficulty recognizing people by faces
    • can rapidly learn new faces
46
Q

Amygdala

&

Autism

A
  • Theory for social deficits
    • Amygdala damaged
    • Unable to link emotional meaning with stimuli
    • Babies unable to connect faces with comfort/food
    • Early social bonds needed for normal development not formed
  • Pt w/ autism bad at judging emotional state of a person from a picture
    • little amygdala activation
  • Eye-gaze processing deficit
    • inability to use gaze to spontaneously to understand others
  • Amygdala much smaller in size
47
Q

Amygdala

&

PTSD

A
  • In PTSD:
    • fragment of a experience“flashback” triggers full force of original emotion
      • b/c implicit memory well preserved
  • Pt’s with PTSD show exaggerated amygdala responses to neg. stimuli by fMRI
  • Normal fear extinction d/t brain regulation of fear response
    • Not forgetting emotional response
    • Fear, stress, and trauma form permanent memories
      • survival strategy
  • Actual mech. for PTSD unknown
  • Treat with psychotherapy or antidepressants
48
Q

Amygdala

&

Prefrontal Cortex

A

Amygdala ↔ Neocortex

  • memory & imagination can cause emotional response
    • promotes use of emotional info in cognitive processing
  • cortex → amygdala
    • conscious thoughts can suppress emotional responses
    • ability to stop initial reaction judged inappropriate
  • amygdala → cortex
    • too much emotion from amygdala to working memory can disrupt prefrontal cortex function
    • leads to bad decisions
    • ex. stressful situations
  • amygdala → cortex >> cortex → amygdala
    • anxiety often control thoughts
    • thoughts have trouble supressing anxiety
49
Q

Klüver-Bucy

Syndrome

A

Most commonly caused by herpes simplex encephalitis.

  • Damage to b/l hippocampi & temporal association cortices
    • anterograde & graded retrograde amnesia
    • dementia
    • seizures
  • Damage to amygdala
    • emotional deficits
      • fearless
      • decreased affect
      • docile
      • placid
  • Loss of decending cortical control over hypothalamus
    • hyperphagia
    • hypersexuality
    • distractibility
  • Damage to “what” portion of visual pathway
    • visual agnosia/psychic blindness
      • can see but cannot recognize or interpret visual information
    • inability to recognize faces/objects
50
Q

Emotion Circuit

Summary

51
Q

Reward Circuit

Overview

A
  • Promotes pleasure associated with certain actions
    • Encourages repetition of behaviors
    • May or may not be essential for survival
  • Involves:
    • Ventral tegmental area ↔ Nucleus accumbens ↔ Prefrontal cortex, ventral pallidum, thalamus
  • Reward ↔ Memory ↔ Emotion
  • Major component from limbic structures
    • motivation, goal directed behavior, memory, emotion, and autonomic functions
  • Rewarding experience or anticipation releases dopamine
    • brain forms implicit (amygdala) and explicit (hippocampus) memories
    • drugs of abuse ∆ release → addiction
52
Q

Reward Circuit

Functions

A
  1. Learning
    • via positive reinforcement
  2. Appropriate behavior
    • taking rewards as goals of behavior
  3. Positive emotion (hedonia)
    • reward elicits pleasure and mood changes,
53
Q

Reward Circuit

Associated Brain Processess

A

Involves:

  • attention
  • anticipation
  • perception (visual and sensation)
  • motivation
  • emotion
  • judgement
  • movement coordination
  • thinking and decision making
  • short and long term memory
54
Q

Reward Circuit

Neurontransmitters

A
  1. Dopamine → well-being, arousal, reward
  2. Opiods → reward and reinforcement
  3. Serotonin → behavioral inhibition
  4. GABA → inhibitory
  5. Glutamate → excitatory
  6. Ach → addiction to nicotine and other drugs
55
Q

Ventral Tegmental Area (VTA)

Location

A

Found near midline in midbrain.

Next to substantia nigra and red nucleus.

56
Q

Ventral Tegmental Area (VTA)

Function

A
  • Contains dopaminergic neurons
  • Origin of two major dopamine pathways:
    1. Mesolimbic pathway
      • VTA → nucleus accumbens
    2. Mesocortical pathway
      • VTA → prefrontal cortex
  • Rewarding activities activates VTA → dopamine release to all targets
57
Q

Nucleus Accumbens

A

Part of the ventral striatum (basal ganglia).

Important role in reward, pleasure, and addiction.

Part of the cortico-striato-thalamo-cortical loop.

  • Includes a core and shell
  • 95% of neurons are medium spiny neurons secreting GABA.
    • main output neuron
  • Large aspiny cholinergic interneurons fewer
  • N. accumbens activated by:
    • dopaminergic afferents from VTA
      • via mesolimbic pathway
    • amygdala
    • hippocampus
    • prefrontal cortex
  • Output:
    • inhibitory to ventral pallidum
      • VP is also inhibitory
        • ⟾ disinhibition of MD thalamus
          • ⟾ excitation of prefrontal cortex
    • inhibitory to substantia nigra and pontine reticular formation
58
Q

Reward Center

A
  • N. accumbens is part of the “reward center”
  • Direct relationship b/t [DA] released at VTA/NA synapse & rewarding effect
  • Natural reinforcers (food, sex, eating) have some rewarding effect by ↑ DA transmission
  • Drugs of abuse tap into system
    • produce reinforcing effect by ↑ DA transmission
    • ∆ chemistry of system​
59
Q

Cocaine

A

Dopamine Reuptake Inhibitor

  • prolonged ↑ [DA] at VTA/n. accumbens synapse
  • causes rewarding effects
  • Tolerance
    • repeated use → ↓ DA receptors → ↓ 2nd messenger signaling → tolerance
    • ∆ sensitivity of reward system
      • natural reinforcers less rewarding
  • Dependence
    • cocaine use stops → low [DA] in reward circuit → withdrawal
      • depression, insomnia, fatigue, restlessness
  • Craving
    • prefrontal cortex hyperresponsive to stimuli releated to drugs
    • overstimulates nucleus accumbens
    • promotes goal-directed behaviors for drug seeking → relapse
  • Implicit emotional memories tied to drug use can activate prefrontal cortex and amygdala years later
60
Q

Drugs of Abuse

Mechanisms

A

Directly or indirectly enhance DA signaling in nucleus accumbens.

  • Cocaine, amphetamines, related stimulants
    • block DA reuptake
    • increase DA release by VTA
  • Nicotine
    • stimulates VTA release of DA
  • Alcohol and opiates
    • inhibits local interneurons normally inhibitory to VTA
    • indirectly promotes VTA release of DA

Drugs can also ∆ response of n. accumbens to glutamate input from other regions.

DA circuits more involved in “wanting” → incentive salience

Mu-opioid circuits more involved in “liking” → hedonic aspect

61
Q

Reward Circuit

Summary

A
  1. Pleasurable thoughts, memories, and activities activate VTA dopaminergic neurons
  2. DA released into reward circuit → activates GABA neurons in nucleus accumbens
  3. GABA neurons in n. accumbens inhibit GABA neurons in ventral pallidum
  4. GABA neurons in ventral pallidum inhibition on MD thalamic neurons decreased
  5. MD thalamic neurons disinhibited and excitation to prefrontal cortex increased
  • Activation associated with pleasure and goal-directed behaviors
  • Drugs of abuse tap into circuit and ↑ DA
  • Memories of past drug experiences & stress
    • from amygdala, hippocampus
    • can directly affect circuit
    • promotes relapse
  • Prefrontal cortex influence over VTA & n. accumbens
    • allows throughts to be rewarding
    • way to exert cortical control over pleasure and goal directed behaviors
62
Q

Stress

HPA-axis & SAM-axis

A

Regulates metabolic, immune, and brain function in response to stressors.

  1. Hypothalamic-Pituitary-Adrenal (HPA) Axis
    1. Stress ⟾ ⊕ paraventricular nucleus (PVN) of hypothalamus ⟾ CRH release
    2. CRH ⟾ anterior pituitary ⟾ ACTH release
    3. ACTH ⟾ adrenal cortex ⟾ cortisol release
    4. Anti-inflammatory and immunosuppressive actions
  2. Sympathetic-Adrenal-Medullary (SAM) Axis
    1. Stress ⟾ ⊕ postganglionic SNS fibers⟾synaptic norepi release⟾adrenal medulla⟾ systemic norepi & epi release
    2. ∆ immune function
63
Q

Autoregulation of HPA-axis

A

↑ [cortisol]plasma ⟾ ⨂ hypothalamus/pituitary/adrenals ⟾ ↓ cortisol production via negative feedback

64
Q

Central regulation of HPA/SAM

A

Corticolimbic, hypothalamic, and brainstem centers have regulatory influence on HPA/SAM axes.

Hippocampus mostly ⊖

Amygdala mostly ⊕

65
Q

HPA-axis dysregulation

A

Chronic stress ⟾ prolonged cortisol secretion ⟾ ↓ glucocorticoid receptors ⟾ glucocorticoid resistance ⟾ inability to shutdown immune responses ⟾ ↑ [inflammatory cytokines]

66
Q

SAM-axis dysregulation

A

Acute activation of SAM-axis for fight-or-flight response

SNS fibers & circulating norepi/epi ∆ immune function including:

cell proliferation, cytokine/Ab production, cell trafficking

Chronic activation of SAM ⟾ dysregulaton of SAM effects on immune system

67
Q

Stress

&

Psychiatric Disorders

A

Stressful life events & HPA-axis dysfunction ∝ risk, onset, and course of pyshiactric orders.

  • Chronic ± HPA/SAM function ⟾ ∆ regulatory feedback mechs ⟾ dysfunction
  • ↑ cortisol common w/ depression, anxiety, substance abuse, psychosis
    • normal neg. feedback mech impaired
    • toxic to limbic structures
      • ex. ↓ hippocampus size
        • impaired inhibition of HPA-axis
        • memory loss
  • HPA-axis functional tests with depression
    • ↓ dexamethasone suppression
    • ↓ CRF stimulation
68
Q

Psychoneuroimmunology

A

Stress, emotion, disease ↔ ∆ immune system ↔ ∆ brain

  • Stress
    ⟾ pro-inflammatory cytokines in children
    ⟾ risk of mental illness in adults
    ⟾ ⊕ neuroinflammation markers in limbic regions
    • Induces sick sx, depression, anxiety
    • Ass. w/ bipolar d/o, schizophrenia, neurodegenerative diseases
  • Bipolar & schizophrenia linked to:
    • childhood autoimmune diseases
    • maternal infecitons
    • inflammation during pregnancy
  • Targeting immune system for treatment of psychiatric d/o being studied
69
Q

Depression

&

Inflammation

A
  • Proinflammatory cytokines / bacterial endotoxins ⟾ sickness/depression ⟾ better w/ antidepressants
  • Cytokines interact w/ depression pathways
    • neuroendocrine & central neurotransmitter ∆
    • similar to depression
  • Severe depression w/ signs of immune activation & ↑ cytokines
    • > inflammatory response to stress ⟾ > chance of developing depression
  • Cytokines ↓ DA release ⟾ ↓ reward circuit ⟾ anhedonia & no motivation
  • ↑ inflammation ⟾ ↑ activation of threat/anxiety circuits
70
Q

Limbic System

Summary

IMS: Neuroanatomy (23 decks)

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