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Med Neuro > Limbic System > Flashcards

Limbic System Flashcards

1
Q

The limbic system is the site where ________ information and ____________ impulses are integrated

  • What are the limbic system’s general functions?
A

cortical information and hypothalamic impulses

  • HOME
    • ​Homeostasis (autonomic regulation)
    • Olfaction
    • Memory
    • Emotion
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2
Q

Papez’s “circuit”:

A

cingulate ⇒ hippocampus ⇒ fornix ⇒
mammillary bodies ⇒ anterior thalamus ⇒ cingulate

  • emotion was a product of the limbic circuit
  • Input is elaborated as emotion and ultimately influence the hypothalamus to release appropriate hormones
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3
Q

D. McClean coined the term “limbic system” and included which structures in it?

A

Expanded Papez’s circuit to include:

  1. parts of the hypothalamus
  2. septal area
  3. orbitofrontal cortex
  4. nucleus accumbens (part of the striatum)
  5. amygdala
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4
Q

What Justifies the Concept of the Limbic System?

A
  1. Common physiologic and neurochemical properties
  2. Intricate anatomic connections
  3. Common behavioral associations
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5
Q

Limibic System:

Common physiologic and neurochemical properties

A
  • High density of cholinergic innervation and opiate receptors
    • memory
    • perception of pain and pleasure
  • Septal nuclei and nucleus basalis of Meynert:
    • cholinergic input for the brain (memory)
  • Mesocorticolimbic Dopamine system:
    • critical for positive reinforcing brain mechanisms
      • drugs and pleasure
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6
Q

What are the limbic structures susceptible to?

A
  1. herpes virus has a special affinity for these regions
    • leads to severe memory and behavioral disturbance
  2. susceptible to kindling and development of seizure foci
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7
Q

What does the hypothalamus coordinate?

A

drive-related behaviors

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8
Q

What are the Cortical Structures in the Outer Core?

A
  1. cingulate gyrus
  2. orbital frontal lobe
  3. subcallosal area
  4. parts of temporal lobe
    • hippocampus
    • parahippocampal gyrus
    • uncus
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9
Q

Outer Core-Cortical Components:

  • Cingulate cortex:
  • Orbital Frontal lobe:
  • Temporal lobe:
A
  • Cingulate cortex
    • **rostral **⇒ emotions and motor
    • **caudal **⇒ visual spatial and memory
  • Orbital Frontal lobe
    • personality, behavioral control, and self awareness
  • **Temporal lobe **
    • memory
    • hippocampus, parahippocampus, entorhinal cortex
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10
Q

Inner Core Structures:

A
  • Hypothalamic nuclei
  • Anterior thalamic nucleus
  • Mammillary body
  • Septal nuclei
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11
Q

Inner Core: Subcortical Components

Hypothalamus

A

Hypothalamus

  1. pleasure center, autonomic, endocrine integration
  2. neurons project to the pituitary ⇒ regulate ACTH and TSH secretion
  3. involved in maternal behavior, blood pressure, feeding, temperature regulation and immune response
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12
Q

Inner Core: Subcortical Components

Amygdala

A

Amygdala

  1. “preservation of self” behaviors
  2. emotion
  3. social behavior
  4. aggression and defense response
  5. sexual behavior
  6. affective significance of visual stimuli
  7. affect of faces
  8. affective regulation
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13
Q

Inner Core: Subcortical Components

Septum

A

Septum

  1. “preservation of species” behaviors
  2. sexual behavior
  3. emotionality
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14
Q

Most anatomical connections are __________.

A

reciprocal

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15
Q

Efferent fiber bundles of the limbic system (3):

A
  1. Fornix:
    • connects hippocampus with septum and mamillary bodies
  2. Stria terminalis:
    • connects amygdala with septum, hypothal, bed nuc, and nuc acc
  3. Ventral amygdalofugal pathway:
    • connects amygdala with hypothal, brainstem, septum
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16
Q
  1. What is the major efferent pathway of the limbic system?
  2. What is the major afferent pathway of the limbic system?
A
  1. Efferent:
    • ​​Fornix connects hippocampus with septum and mammillary bodies
  2. Afferent
    • ​​Perforant path connects entorhinal cortex with dentate gyrus
    • major afferent to the hippocampal formation
17
Q

Medial forebrain bundle:

A

connects hypothalamic nuclei and amygdala and brainstem nuclei

18
Q

Kluver-Bucy Syndrome in rhesus monkeys:

A

bilateral large temporal lobe lesions including amygdala, hippocampus, uncus

  1. Psychic blindness - lost ability to detect the meaning of objects based on visual criteria
  2. Oral tendencies - examine all objects by mouth
  3. Hypermetamorphosis – notice and react to every visual stimulus
  4. Tameness – no motor or vocal reactions with fear or anger
  5. Hypersexuality
19
Q

Human Kluver-Bucy Syndrome:

A
  1. Increased oral activity
    • examine objects with mouth
  2. Hypersexuality
    • indiscriminate sexual advances
  3. Hypermetamorphosis
    • attend and react to every visual stimulus within the visual field
    • subsequent compulsive handling of the object
  4. Placidity
    • ​​flattened affect, lack of aggressive behavior, absence of fear
  5. Visual agnosia
    • ​​loss of recognition of simple, familiar objects (e.g., eating utensils) or people
  6. Bulimia
20
Q

Etiology of Human Kluver-Bucy Syndrome:

A

All autopsied cases have extensive lesions involving bilateral temporal cortex and amygdala

  1. Post traumatic encephalopathy
  2. Herpetic viral encephalitis
    • probably the most common
  3. Anoxia
  4. Subarachnoid hemorrhage
  5. Pick’s disease
  6. Alzheimer’s disease
  7. Bilateral temporal infarction
  8. Focal status epilepticus
21
Q

Geschwind syndrome:

A

sensory limbic hyperconnection-strengthening of synaptic connections

  • Increased concern
    • philosophical, cosmic, or religious issues
  • Altered sexual behavior (usually Hyposexuality)
  • Hypergraphia
    • ​extensive writing that is typically religious or philosophical in nature
  • Viscosity
    • ​a tendency towards interpersonal stickiness, difficulty in breaking off conversation
  • progressive overinvestment of perception and thought with affective significance ⇒ bizarrely emotionalized concept of the world
22
Q
  1. Geschwind syndrome (or Interictal personality) is caused by what?
  2. Kluver-bucy syndrome is caused by what?
A
  1. Geschwind Syndrome ⇒ Hyperconnection
  2. Kulver-bucy Syndrome ⇒ Disconnection
23
Q

Brain Pleasure Regions:

A
  1. Lateral septal region
  2. Portions of amygdala
  3. Parts of hippocampus:
    • Lateral hypothalamus
    • Medial forebrain bundle
    • Nucleus accumbens
  4. Anterior cingulate cortex
24
Q

What is most important for motivational processes and what drugs affect this region of the brain?

A

Mesolimbic dopamine system

  1. Heroin increases the neuronal firing rate of dopamine cells
  2. Cocaine inhibits the reuptake of dopamine
25
Q

What is the function of the amygdala?

A

Modulation and experience of emotional reactions

  • thought to play a major role in the integration of emotions, fear, and memory
  • primates and humans have cells in the amygdala that respond selectively to faces
  • Amydala is critical for normal social interactions
26
Q

What will happen if the amygdala is lesioned?

A
  • tameness or reduced emotionality
    • most frequently associated with affective phenomena in patients with epilepsy
  • support classical fear conditioning and plays a role in PTSD
    • inability to extinguish fear memories
  • indiscriminate hypersexuality
  • devastating effect on maternal behavior
27
Q

Septal Region:

A
  1. Sexual behavior
    • ​​Septal lesions
      • enhancement of social contacts
      • hypersexuality
  2. Emotionality
    • ​​Septal lesions
      • ​rage-like attacks
      • increased irritability
28
Q

Hippocampus:

A

declarative memory

  • Crucial for the formation of episodic memories in humans
    • acquisition of facts and events
  • Lesions in hippocampus, dorsal medial nucleus of the thalamus, mammillary nuclei alone or in combination can lead to amnestic states
29
Q

What are the two types of declarative memory?

A
  1. Episodic:
    • Personal events in one’s life, actively remembered, embedded in time and place
    • Ex: yesterday I went to a baseball game
  2. Semantic:
    • Facts, known rather than actively remembered
    • Ex: Madrid is the capital of Spain, the square root of 9 is 3
30
Q

Hippocampal Formation:

  1. Major efferent is the _________.
  2. Major afferent is the _________.
A
  1. Major efferent is the fornix
  2. Major afferent is the perforant path
31
Q

Perforant path connects _________ _________ with the _______.

A

Perforant path connects entorhinal complex (EC) with the dentate

  1. Neurons from EC project to dentate ⇒ synapse with granule cells and then with hippocampal pyramidal cells
  2. These cells extend toward lateral ventricle where they form the alveus, then fimbria, then fornix
32
Q

Other causes of Memory Disorders (4):

A
  1. Head Trauma
  2. Stroke
  3. Wernicke Korsakoffs
  4. Dementia
33
Q

Wernicke Korsakoff’s Syndrome:

A
  • Due to chronic alcoholism and nutritional deficiency (thiamine)
  • Acute state is Wernicke’s encephalopathy:
    • confusion, disorientation, oculomotor dysfunction, ataxia
  • Chronic anterograde and temporally-graded retrograde amnesia
  • Lesions are in mammillary bodies and thalamus
34
Q

What are the Functions of the Cingulate Gyrus? What will happen if it is lesioned?

A
  • Anterior cingulate: emotion and motor functions
  • Posterior cingulate: visuospatial and memory functions

Lesions

  • Contralateral motor neglect (attention)
  • Behavioral changes after lesions of the anterior cingulate
35
Q

What are the behavioral changes associated with an anterior cingulate gyrus lesion?

A
  • emotional blunting, decreased motivation, disruption of mating behavior, impaired maternal-infant interactions, impatience, lowered threshold for fear or startle
  • Abolish conditioned emotional vocalizations,
  • Decreased pain
  • In humans: apathy, disinhibition, placidity, depression, anxiety, obsessive compulsive behaviors, heightened sexuality, bulimia
36
Q

What is the Role of the Anterior Cingulate?

A

Integration of thought, motivation and emotion with movement:

  1. Excessive amplification of emotional signals:
    • anxiety
    • obsessive compulsive behaviors
  2. Amplification of motor behavior:
    • tics
    • impulsive behavior
  3. Excessive filtering of emotions and motor behavior:
    • Apathy
    • akinesis
    • mutism
37
Q

How is the Cingulate Gyrus Assocated with Psychopathology?

A
  • Cingulotomy has been used to successfully treat OCD
  • Association with sociopathy:
    • ​Sociopathic individuals who show blunted autonomic response to emotional stimuli
  • Akinetic mutism
    • ​most commonly associated with bilateral anterior cingulate cortex lesions
38
Q

Gilles de la Tourette Syndrome:

A
  • Abnormalities in AC is postulated because of its role in affective vocalizations
  • Complex coordinated movement patterns are evoked by electrical stimulation of the AC
  • Lesions of AC can relieve obsessive compulsive behaviors, an associated feature of GTS
  • Reduced TS symptoms seen after disconnection of AC from thalamus
39
Q

Frontal Lobe Syndromes (3):

A
  1. Orbital frontal
    • disinhibited, tactless, bawdy, boastful, grandiose, restless, impulsive, inattentive, perseverative, tendency to dress carelessly dress and eat gluttonously.
  2. Frontal/convexity or dorsolateral
    • apathetic, slow, demonstrating little initiative or spontaneity, responding in an automaton like manner, vacancy of expression
  3. Medial frontal
    • akinetic mutism, inert, speechless, with intact sleep wake cycle, “motionless, mindless, wakefulness,” loss of drive to move or speak

Med Neuro (10 decks)

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