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Med Neuro Block 4 > 5 - Limbic System > Flashcards

5 - Limbic System Flashcards

1
Q

What is the function of the limbic system and where is it located?

A

Interconnected cortical and subcortical structures that link visceral states and emotion to cognition and behavior.

Limbic structures are interposed between the neocortex and the brainstem. (Limbis means border)

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2
Q

What is integrated within the limbic system?

A

Cortical information and hypothalamic impulses. The goal of this is homeostasis (autonomic regulation), olfaction, memory, and emotion (HOME).

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3
Q

What is the funciton of each area?

A

Limbic areas in green.

Higher-order (heteromodal) associated areas in pink.

Modality-specific (unimodal) association areas in yelllow.

Primary sensory and motor areas in blue.

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4
Q

What is Papez’s circuit?

A

Cingulate

Hippocampus

Fornix

Anterior thalamus

Mammillary bodies

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5
Q

What contribution did MacLean make to the understanding of the limbic system?

A

Coined term limbic system and incorporated Papez’s ideas into a model that hasn’t changed much since.

Expaned it to include: parts of hypothalamus, septal area, orbitofrontal cortex, nucleus accumbens, and the amygdala.

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6
Q

What is considered the outer core of the limbbic system? What is the function of each region?

A
  1. Cingulate cortex: rostral - emotions; caudal - visual spatial and memory
  2. Orbital frontal lobe: personality, behavior control, self-awareness
  3. Temporal lobe (hippocampus, parahippocampus, entorhinal cortex): memory
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7
Q

What are the inner core structures of the limbic system?

A
  1. Hypothalamus
  2. Amygdala
  3. Septum
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8
Q

What part of the limbic lobe is the hypothalamus in? What is it’s function?

A

Inner core

Pleasure center, autonomic, endocrine integration, neurons project to the pituitary, maternal behaviour, BP, feeding, temperature regulation, and immune response.

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9
Q

What part of the limbic system is the amygdala in? What is it’s function?

A

Inner core structure.

Preservation of self behaviors, emotion, social behavior, aggression and defense response, sexual behavior, affective significance of visual stimuli, affect of faces, and affective regulation.

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10
Q

What part of the limbic system is the septum in? What is it’s function?

A

Inner core structure.

Preservation of species behaviors, sexual behavior, emotionality.

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11
Q

What connects the hippocampus to the mammillary, the anterior thalamus, the septal nuclei, and the nucleus accumbans?

A

The fornix.

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12
Q

What connects the mammillary bodies and the hypothalamus to the anterior thalamus, hypothalamus, and the septum?

A

The mammillothalamic tract.

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13
Q

What connects the entorhinal cortex and the cingulate gyrus to the dentate, parahippocampal gyrus, hippocampus, the amygdala, and the midbrain?

A

The perforant path.

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14
Q

What is the function of the fornix?

A

It’s the main projection tract connecting the hippocampus and the mammillary boy.

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15
Q

What is the function of the mamillothalamic tract?

A

Originates from the mammillary bodies and terminates in the anterior and dorsal nuclei of the thalamus.

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16
Q

What is the major efferent path from the limbic system?

A

The fornix: connects the hippocampus with the septum and the mammillary bodies.

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17
Q

What is the major afferent path to the hippocampal formation?

A

Perforant path: connects the entorhinal cortex with the dentate gyrus

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18
Q

What is the funcion of the anterior thalamic projections?

A

Connect to the orbitofrontal and anterior cingulate cortex. (green)

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19
Q

What is the path of the cingulum fibers?

A

Run from the amygdala and parahippocampus to the frontal lobe/cingulate. (red)

20
Q

What is the path of the uncinate fasciculus?

A

Connects the anterior part of the temporal lobe with the orbital and polar frontal cortex. (light blue)

21
Q

What justified the concept of the limbic system being a true system?

A
  1. Common psychiologic and neurochamical properties
  2. Intricate anatomic and mostly reciprocal connections
  3. Common behavioral associations
22
Q

What virus has specific affinity for the limbic regions? Shat are other common psycsiologic and neurochemical properties of the region?

A

Herpesvirus

Susceptible to kindling and development of suizure foci.

High density of cholinergic innervation and opiate receptors.

23
Q

What effect can herpesvirus have on the brain?

A

Herpes encephalitis in the orbito-temporal-frontal regions.

Results in severe behavioral abnormalities and memory impairment.

24
Q

What are the three overlapping functional sections of the limbic system?

A

Hippocampal and parahippocampal regions: memory and spatial orientation

Temporal-amygdala-orbitofrontal: integration of visceral sensation and emothion with semantic memory and behavior

Medial “default network”: autobiographical memory and introspection/self-directed thinking

25
Q

What occurs with Kluver-Bucy syndrome in humans?

A

Bilateral temporal lobe lesion resulting in:

Increased oral activity

Hypersexuality

Hypermetamorphosis - attend and react to every visual stimulus and compulsively handling objects

Placidity - flattended affect, lack of fear or aggression

Visual agnosia - loss of recognition of simple objects

Bulimia

26
Q

What can result in Human Kluver-Bucy syndrome? What do they all have in common?

A

Post-traumatic encephalopathy

Herpetic viral encephalitis

Anoxia

Subarachnoid hemmorrhage

Pick’s disease or alzheimers

Bitemporal infarction

Focal status epilepticus

All show extensive lesions involving bilateral temporal cortex and amygdala.

27
Q

What is Geschwind Syndrome? Who is it seen in?

A

Sensory limbic hyperconnection with strengthening of synaptic connections.

Interictal personality in temporal lobe epilepsy.

28
Q

What are symptoms of Geschwind syndrome?

A

Increased concern with philosophical issues.

Altered sexual behavior (hyposexuality)

Hypergraphia: extensive writing that is typically religious or philosophical in nature

Viscosity: tendency towards interpersonal stickiness or difficulty breaking off conversation

29
Q

What is the basic characteristic of people with Geschwind syndrome?

A

Progressive overinvestment of perception and thought with affective significance resulting in a bizarrely emotionalized concept of the world.

Basically the opposite of Kluver-Bucy.

30
Q

What is the difference between Interictal personality and Kluver-Bucy syndrome?

A

Interictal personality - hyperconnection

Kluver-bucy syndrome - disconnection

31
Q

What is the funciton of the amygdala?

A

Major role in integration of emotions, fear, and memory.

Modulation and experience of emotional reactions and attributes affective significance to visual stimuli.

32
Q

What results from lesions of the amygdala? What disorder is associated the amygdala?

A

Lesions: tameness and reduced emotionality

Supports classical fear conditioning and plays a role in PTSD, a disorder characterized by inability to extinguish fear memories.

33
Q

What is the amygdala critical for? What do monkeys with no amygdala do?

A

Critical for social interactions.

With no amygdala monkeys become social isolates, show indiscriminate hypersexuality, and have devastating effects on maternal behavior.

34
Q

The amount of activity in the amygdala is associated with what?

A

The amount of emotional significant and degree of ambiguity of a social interaction (firing increases as emotional significant and level of ambiguity increases because you’re trying to figure out what’s occurring)

Some cells response selectively to faces.

Involved in fear conditioning.

35
Q

What results from orbital frontal lobe syndrome?

A

Disinhibitied, tactless, boastful, grandiose, restless, impulsive, inattentive, and a tendency to dress carelessly and eat gluttonously.

Problems with starting, stopping, and switching. All important for behavior.

36
Q

What results from frontal lobe syndrome of the frontal/convexity or dorsolateral region?

A

Apathetic, slow, little initiative or spontaneity, responsing in an automated manner, vacant expression.

37
Q

What results from a frontal lobe syndrome in the medial frontal region?

A

Akinetic mutism, inert, speechless, with intact sleep wake cycle. Motionless, mindless, wakefullness. Loss of drug to move or speak.

38
Q

What occurs with hippocampal lesions?

A

Hippocampal lesions lead to amnestic states such that the person can no longer encode new memories and only knows their past.

The hippocampus is required for acquisition of facts and events (declarative memory)

39
Q

What is Wernicke Korsakoff’s Syndrome caused by? What are characteristics of this syndrome?

A

Caused by chronic alcoholism and nutritional deficiency (thiamine).

Acute state ie Wernicke’s encephalopathy: confusion, disorientation, oculomotor dysfunciton, and ataxia.

Chronic: anterograde and temporally-graded retrograde amnesia

Lesions are in mammillary bodies and thalamus.

40
Q

What results from lesions of the septal region in humans?

A

Increased sexual activity following septal damage.

41
Q

What are the brain centers for pleasure, pain, and punishment? What substances are implicated in the location of effective self-stimulation?

A

Lateral septal region

Lateral hypothalamus

Medial forebrain bundle

Nucleus accumbens

Catecholamines and dopaminergic systems implicated in self-stimualtion.

42
Q

What effect do addictive drugs have on the limbic system? What effect do heroin and cocain have on these systems?

A

The mesolimbic dopamine system is important for motivational processes.

Some drugs have their effects by enhancing mesolimbic dopamine activity.

Heroin increases the nruonal firing rate of dopamine cells while cocain inhibits the reuptake of dopamine.

43
Q

What are the functions of the “default mode” regions, the posterior cingulate and the anterior cingulate?

A

Posterior: visuospatial and memory functions.

Anterior: hemi-attention (contralateral neglect)

44
Q

What diseases are associated with the cingulate gyrus? What part of the gingulate gyrus is associated with each?

A
  1. Tourette’s syndrome: anterior cingulate region
  2. OCD: cingulotomy has been successful treatment
  3. Chronic pain: cingulotomy are no longer bothered by pain
  4. Sociopathy: sociopathic pts show blunted autonomic resposne to emotional stimuli
  5. Akinetic Mutism: associated with bilateral anterior cingulate cortex lesions
45
Q

What is the function of the anterior cingulate? What can excessive amplification of emotional and motor signals lead to? What can excessive filtering of emotions and motor behavior lead to?

A

Integration of thought, motivation, and emotional with movement.

Excessive amp of emotional signals: anxiety and OCD

Excessive amp of motor behavior: tics impulsive behavior

Excessive filtering: apathy, akinesis, mutism.

Med Neuro Block 4 (10 decks)

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