Medicine > Limbic > Flashcards

Limbic Flashcards

(47 cards)

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1
Q

what does the limbic system do

A

-processes emotion and related brain activity, memories, environmental cues and state of the individual

-act on this info to maximise survival strategies

eg.
sensory input into cerebral cortex
leads to
reaction/response
-fight/flight, freeze, rest and digest
-heart rate, sweating, resp. rate, defecation, micturition, evacuation, facial expression

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2
Q

what are the core processing components of the limbic system

A

amygdala
hippocampus
septal area
thalamus
limbic cortex

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3
Q

what are the effectors (output) of the limbic system

A

hypothalamus
brain stem structures

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4
Q

what are important white matter bundles found in the limbic system
what do they connect to

A

STRIA TERMINALIS
FORNIX

amygdala via stria terminalis

hippocampus via the fornix to mammillary bodies

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5
Q

where is the amygdala found

A

grey matter
in anterior TEMPORAL lobe
tail of caudate nucleus and rostral to hippocampus
with nuclei (central, corticomedial, basolateral)

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6
Q

what is Kluver-bucy syndrome

A

rare syndrome in humans produces behavioural impairment
associated with damage to the anterior temporal lobes

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7
Q

what are common effects of kluver-bucy syndrome

A

hyperorality
lack of fear

less common
-hypersexuality
-visual agnosia
-xs attentiveness to visual stimuli
-memory loss
-enhanced aggressino
-seizures
-dementia

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8
Q

what are causes of kluver-bucy syndrome
treatment

A

herpes encephalitis
trauma
tumours
hypoxia
pick’s disease

symptomatic
may use psychotropic medicatoins

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9
Q

what is Urbach-Wiethe disease
what is main symptoms

A

temporal lobes have calcification causing amygdala to degenerate
rare recessive genetic disorder

NO FEAR
difficulty building memories
defect in judgement in facial expressions

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10
Q

what happens if there is electrical stimulation of the amygdala

A

anxiety and fear

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11
Q

what does fear activate in the brain (fMRI)

A

central nucleus
bed nucleus of stria terminalis (BST)

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12
Q

what are the functions of the nuclei in the amygdala

A

sensory input into basal lateral nuclei

output from central nucluus

corticomedial receives olfactory input (not very well developed)

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13
Q

what happens in creating an emotional response eg. snake in room

A

stimulus
-fast track via thalamus to amygdala (lateral nuclei) does not reach consciousness– rapid response (may SAVE LIFE)
-longer route via cerebral cortex (realise theyre not as bad)

concept (idea of snake)
-cerebral cortex

context
-HIPPOCAMPUS (space/time)

input-lateral
output-central

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14
Q

what does subliminal mean

A

below consciousness

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15
Q

how does amygdala learn a modified fear response

A

fear stimulus to a noise (eg.)

Pavlovian type learning experience

then dont need fear stimulus just noise to elicit fear

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16
Q

where does the amygdalas output go
(main output)

A

stria terminalis to hypothalamus and brain stem
reward centre in septal area and BST

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17
Q

what are the direct outputs from the amygdala to the brain stem

A

Periaqueductal grey matter
locus coeruleus
parasympathetics
ventral tegmental area

drive autonomic response

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18
Q

what is a summary of the amygdala

A

controls emotional reactions (threat/fear)
via effectors (hypothalamus, brain stem through to autonomic nervous system, endocrine and motor system)

emotional learning resetting according to threat level and experience

it does simple codes of value (good/bad) for a threat/emotional trigger
-more refined mechanism for evaluating the survival value of emotional response

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19
Q

which part of the cingulate gyrus is found in the limbic cortex

Study These Flashcards
A

-anterior cingulate cortex
-anterior portion of middle cingulate cortex
(also posterior cingulate cortex)

INVOLVED IN EMOTIONS

20
Q

what does the anterior cingulate area encode
and what does it do in response to amygdala

Study These Flashcards
A

happiness
sadness
fear
emotional memory
pain/anticipated pain
unpleasant experiences

TOP-DOWN INFLUENCE–RECONDITIONS AMYGDALA

eg. next time see snakes– reconditioned to not freak out so much
-computes relevance/outcome (appropriate behaviour)
-provides conflict resolution)
-part of pain network

21
Q

does cingulate gyrus drive motor functions from motor cortex

Study These Flashcards
A

yes

drives OWN responses via the brainstem and hypothalamus
direct connections to brain stem

either through amygdala or separately

motor reactions complex and context dependent– approach/avoidance behaviour, desire to leave room, vocalisation, facial expression, kissing, lip puckering, pushing

specific zone for driving face muscles

direct outputs from ACC to autonomic system

22
Q

summary of anterior cerebral cortex

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A
  • Has reciprocal connections with the amygdala
  • Heavy direct connections to autonomic centres
    including brainstem (bypass amygdala)
  • Classified as the primary limbic cortex
  • Attentional system, monitors conflict and
    resolves it
  • Pain activates complex interaction with
    emotion here
  • Motivates behaviours, mediates orientation
    towards or away from emotional stimuli
  • Recodes value of stimulus on amygdala
23
Q

what does the insula do

Study These Flashcards
A

works with the ACC in evaluating emotional contexts- role in EMPATHY
light up in pain and others pain

  • Anterior portion considered to work with the ACC
  • Input -> Visceral sensory information including pain (like distended tummy- pain)
  • Patients with lesions have defects including in
    awareness of other people’s pain (empathy)
  • Classified as limbic “sensory” cortex

EMOTIONAL AWARENESS

24
Q

difference between amygdala and ACC

Study These Flashcards
A

amygdala-simple emotion codes

ACC- recodes amygdala
-modify good/bad
-drive motor responses directly
-avoidance mechanisms
-work with insula

they are the processes of emotion

25
What happens in PTSD to limbic system
* Part of ACC is hypo-responsive in PTSD * Reduction in size of ACC * Amygdala becomes hyper-responsive to trauma related stimuli * Top-down control of Amygdala by ACC is therefore missing in PTSD
26
what are the effectors of the limbic system what do they do
hypothalamus locus coeruleus periaqueductal grey dorsal raphe nucleus mediate emotional reactions via ANS modulating learning/memory
27
what is the major limbic system effector
hypothalamus direct input: limbic cortex, amygdala input from: olfactory, sensory systems, viscera, retina, internal signals outputs: brainstem, spinal cord autonomic endocrine behavioural basic homeostasis
28
what is the locus coeruleus
a midbrain nucleus involved in physiological responses to panic and stress generates huge blanket of noradrenaline neuron fibers -ALERTNESS, WAKEFULNESS (eg. if see snake need to be alert) promote anxiety and formation of emotional memories (projections from LC to amygdala) projections to hypothalamus maintain arousal projections FROM PAG selects fight or flight mode
29
what are the different PAG pathways
amygdala communicates with PAG to do different things ventrolateral PAG-- vagal path (parasympathetic in FREEZING) dorsolateral PAG-- LC and BSTem (fight or flight) projects to nucleus of solitary tract, dorsal nucleus of vagis, intermediolateral column
30
intensity different pathways
far vs close snake gauge extent of response far: less serious with PAG -striatum involved (initiating movement) CG through basolateral amygdala to striatum -independent to PAG close -central amygdala drives PAG and other brainstem centres to panic/freeze mode -autonomic nervous system engaged
31
what is the dorsal raphe nucleus
project an ascending system projects to and receives from amygdala and ACC regulate dynamic mood state theory of 5HT and depression/mood high levels of 5HT=MANIA low levels of 5HT=DEPRESSION
32
what are the changes that occur in limbic system structures in established depression
-reduced metabolism in ACC -reduced size of ACC -amygdala hyperactive and medial output region increased in size
33
what is the connection with 5HT processing and a predisposition to depression?
In normal individuals with: * Variant polymorphism in 5HT transporter gene (5HTT) * Diminishes transcription efficiency and expression * Possible increased risk of depression (especially in reaction to previous stress) * Reduced communication between ACC and amygdala * Reduced size of amygdala and increased reactivity of amygdala to emotional stimuli
34
reward centre and depression
* Amygdala pathways partially overlap with those that regulate reward * Reward centres are located in the NUCLEUS ACCUMBENS and prefrontal area * Amygdala is connected to the ventral striatum (Nuc accumbens) via stria terminalis * In some types of depression blunted activation of the reward centres * Suggests targets for deep brain stimulation nucleus accumbens
35
what is the role of the hippocampus and the limbic system and where is it located
CONTEXT VERY IMPORTANT indirect influence on emotion -important in establishing EPISODIC MEMORY SPATIAL AND TEMPORAL EMOTION WITH -emotional -sensory -cognitive information to establish new episodic memory This framework allows the experience to be stored in such a way that it can be later retrieved as a conscious recollection of that experience. very close to amygdala looks like a seahorse deep in temporal lobes elongate structure in the floor of the lateral ventricle output is fornix
36
what makes up the hippocampal formation
hippocampus and associated cortex (parahippocampal gyrus) around hippocampus: perirhinal cortex neocortex entorhinal cortex parahippocampal cortex
37
what is the main gateway of the hippocampal formation
entorhinal area (for input with the neocortex) bring in sensory input
38
what are some major clues to the function of the hippocampus
EARLY hippocampal damage difficult to remember events of their daily lives, but seem to have an intact semantic memory, being able to learn school subjects such as languages and acquiring factual knowledge Patients with hippocampal damage can retain memories of events that occurred years before to the onset of their brain damage. Sparing of remote memory - undergoes consolidation gradient, memories gradually become independent of hippocampus as they are consolidated in other brain regions (neocortex). Hippocampal amnesic patients displayed a deficit in their ability to imagine new experiences. This inability to construct from its individual components a mental narrative may reflect the synthetic defect (episodic memory amnesia)
39
what is involved in declarative memory
episodic memory (recollection about a specific event in one's past, tied to a specific time and place) AND sematic memory (general knowledge about the world)
40
What are place cells (found in the hippocampus) what do other cells do
provide clue about importance of spatial information - become active when in a certain area- recording spatio info other cells response to other modalities such as odours, tactile info, timing to give overall picture of context CA3- temporary consolidation CA1- more permanent consolidation
41
what are the 3 inputs into hippocampus (through related cortex for memory processing)
1. Dorsal stream processes spatial context culminates in PARAHIPPOCAMPAL CORTEX SCENE RECOGNITION, LOCATION, TEMPORAL CONTEXT 2. Ventral stream processes object recognition and culminates in PERIRHINAL CORTEX OBJECT, FACE RECOGNITION, CONCEPTUAL IDENTITY, SALIANCE 3. Rostral hippocampus processes interoceptive signals for emotional and motivational modulation EMOTIONAL INFORMATION 1. and 2. go to caudal hippocampus -processes exteroceptive signals for scene learning
42
What diseases is atrophy of the hippocampus found in
alzheimers hypertension depression epilepsy cushings stress genetic disorders chronic alcohol use sensitive to stress (GLUCOCORTICOIDS) ISCHAEMIA SENSITIVE
43
WHAT IS WILLIAMS SYNDROME
(1/10,000 births) genetic deletion syndrome in which there is developmental hippocampus effects
44
what is Wernicke's- Korsakoff syndrome
thiamine deficient alcohol related hippocampal damage decrease in hippocampal learning
45
what is the fornix
(arch)- white matter bundle output structure of hippocampus project to mammillary bodies which is connected to the anterior nucleus of the thalamus
46
what are the functions of the fornix
language visiospatial emotional/motivational learning scene learning output segregated according to hippocampus processing
47
what happened to patient who had glioma in LV that obliterated fornix
clear memory defect and delayed recall
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