SM_89b: Limbic System

Question 1

List components of the limbic system

Answer 1

Components of the limbic system

• Limbic lobe: ring of cortex outside of corpus callosum - parahippocampal, cingulate, subcallosal gyri
• Amygdala
• Hippocampal formation and associated structures
• ± olfactory (piriform cortex)
• ± hypothalamus (mamillary bodies) ± parts of thalamus connected above

Question 2

Describe organization of limbic cortex

• Hippocampal formation (limbic core, 3 layers, archicortex)
• Paralimbic cortex (transitional cortex, 6 layers, mesocortex)

or (allocortex, paleocortex, archicortex)

Question 3

Limb cortices ____ have the 5-6 layered structure of the rest of the cerebral cortex (neocortex)

Answer 3

Limb cortices do NOT 5-6 layered structure of the rest of the cerebral cortex (neocortex)

Question 4

Limbic cortex forms a ____

Answer 4

Limbic cortex forms a ringlike limbic lobe around the edge of the cortical mantle, which surrounds the corpus callosum and upper brainstem

Question 5

Functions of the limbic system are ____, ____, ____, and ____

Answer 5

Functions of the limbic system are homeostatic functions including autonomic and neuroendocrine control, olfaction, memory, and emotions / drives

Question 6

Paralimbic cortex serves as a ____

Answer 6

Paralimbic cortex serves as a mediator between association cortex and limbic system

Question 7

Describe the paralimbic cortex pathway

Answer 7

Paralimbic cortex pathway

1. Cingulate gyrus
2. Paraolfactory cortex
3. Orbitofrontal cortex
4. Insula
5. Uncus
6. Parahippocampal gyrus
7. Cingulate gyrus

Question 8

Hippocampal formation is ____ containing the ____, ____, and ____ submerged deep in the ____

Answer 8

Hippocampal formation is primitive cortical structure containing the dentate gyrus, hippocampus, and subiculum submerged deep in the parahippocampal gyrus

Question 9

Describe the pathway of the hippocampal formation

Answer 9

Hippocampal formation

1. Cortex
2. Entorhinal cortex (medial temporal lobe)
3. Perforant pathways
4. Dentate gyrus (input station)
5. Hippocampus

Question 10

Hippocampus extends the length of the floor of the ____ and becomes continuous with the ____ below the splenium of the corpus callosum

Answer 10

Hippocampus extends the length of the floor of the inferior horn of the lateral ventricle and becomes continuous with the fornix below the splenium of the corpus callosum

Question 11

___ through ___ are sectors of the hippocampus

Answer 11

CA1 through CA4 are sectors of the hippocampus

(subiculum is the mesocortex from the 3rd-6th layers)

Question 12

____ of the hippocampus is most susceptible to ischemia

Answer 12

Sommer sector (CA1 and CA2) of the hippocampus is most susceptible to ischemia

Question 13

Describe hippocampal input and output

Answer 13

Hippocampal input and output

1. Cortical areas
2. Alvear pathways and perforant pathways
3. Dentate / hippocampus
4. Mossy fibers go to CA3
5. Fornix
6. Fibers bend around thalamus and axons terminate in the mamillary bodies of the hypothalamus or septal area / anterior thalamus

Question 14

Papez circuit provides an anatomic substrate for convergence of ____, ____, and ____

Answer 14

Papez circuit provides an anatomic substrate for convergence of cognitive (cortical) activities, emotional experiences, and expression

(ties the cerebral cortex and hypothalamus)

Question 15

Papez circuit consists of the ____, ____, ____, ____, and ____

Answer 15

Papez circuit consists of the parahippocampal gyrus, hippocampus, mamillary bodies, anterior thalamus, and cingulate gyrus

Question 16

Describe pathway of the Papez circuit

Answer 16

Papez circuit

1. Hippocampal axons to fornix
2. To mamillary bodies
3. Via mamillothalamic tract to anterior thalamus
4. Cingulate gyrus
5. Parahippocampal gyrus

Question 17

Papez circuit ends in the ____

Answer 17

Papez circuit ends in the parahippocampal gyrus

Question 18

Principal connections to limbic system include ____ and ____

Answer 18

Principal connections to limbic system include hippocampal system / limbic lobe and olfactory / amygdaloid connections

Question 19

Describe connections between the amygdala and hypothalamus

Answer 19

Connections between the amygdala and hypothalamus

• Hippocampus to mamillary bodies of thalamus via fornix
• Amygdala to hypothalamus and vice versa via stria terminalis and amygdalofugal pathway
• Cingulate gyrus to hypothalamus via medial forebrain bundle

Question 20

Lesions in lateral amygdala induce ____

Answer 20

Lesions in lateral amygdala induce unrestrained eating (bulimia)

Question 21

Lesions in medial amygdala induce ____ and ____

Answer 21

Lesions in medial amygdala induce anorexia and hypersexuality

Question 22

Electrical stimulation of amygdala results in ___, ___, ___, and ___

Answer 22

Electrical stimulation of amygdala results in fear, anxiety, rage, and aggression

Question 23

Hippocampus converts ____ to ____ and contains ____ that encode ____

Answer 23

Hippocampus converts short-term memory to long-term memory and contains place cells that encode spatial memory

Question 24

Bilateral damage to hippocampus / fornices can cause ____

Answer 24

Bilateral damage to hippocampus / fornices can cause anterograde amnesia (no new memories can be formed)

Question 25

Alzheimer's disease commonly results from degeneration in parts of the \_\_\_\_

Answer 25

Alzheimer's disease commonly results from degeneration in parts of the Papez circuit * Impaired * Unable to learn new information * Difficulty naming people, objects, etc

Question 26

Transient global amnesia is a rare disorder involving ____ due to damage in the ____ and \_\_\_\_

Answer 26

Transient global amnesia is a rare disorder involving episodic memory problems due to damage in the hippocampus and other medial temporal lobe structures in the Papez circuit

Question 27

Wernicke-Korsakoff results from ____ and commonly occurs in \_\_\_\_

Answer 27

Wernicke-Korsakoff results from thiamine/B1 deficiency and commonly occurs in alcoholics

Question 28

Wernicke-Korsakoff results in triad of \_\_\_\_, \_\_\_\_, and ____ acutely

Answer 28

Wernicke-Korsakoff results in triad of ataxia, eye movement abnormalities (horizontal gaze paresis / nystagmus / ophthalmoplegia), and confusional states (anterograde and retrograde amnesia after acute stage, poor judgement / initiative / impulse control / sequencing tasks, lack of awareness, confabulate when answering questions)

Question 29

Wernicke-Korsakoff results from ____ necrosis of \_\_\_\_

Answer 29

Wernicke-Korsakoff results from bilateral necrosis of mamillary bodies

Question 30

HSV-1 has tropism for the ____ and can cause \_\_\_\_

Answer 30

HSV-1 has tropism for the limbic cortex and can cause severe encephalitis involving predominantly the limbic areas

Question 31

Limbic encephalitis is \_\_\_\_

Answer 31

Limbic encephalitis is autoimmune (inflammatory)