Limbic System -Bales

Question 1

What is the Papez circuit? What will bilateral lesions to this circuit cause?

Answer 1

hippocampus → hypothalamus (mammillary body) → thalamus → cortex (cingulate) → hippocampus

open circuit*

bilateral lesions=inability to acquire new memories

Question 2

What is the septal region thought to play a part in?

Answer 2

emotion, thirst, learning, autonomic inhibitory functions and sexuality and orgasm

Rats will stimulate this over eating or drinking!

Question 3

What does the septal nuclei connect with? (5)

Answer 3

cingulate gyrus
habenular nuclei (stria medullaris thalami)
hypothalamus (medial forebrain bundle -MFB)
hippocampus ( fornix)
amygdala (stria terminalis)

Question 4

What are the functions of the anterior and posterior cingulate cortex?

Where do these limbic fibers go?

Answer 4

anterior=motor

posterior=sensory

hippocampus

Question 5

What is Korsakoff syndrome? What symptoms will be seen?

Answer 5

Mammillary bodies preferentially degenerate in chronic alcoholism

amnesia

Question 6

Where is the entorhinal cortex?

Where does this cortex receive and send info?

Answer 6

anterior half of the parahippocampal gyrus (BA 28)

receives cingular fibers and inputs to the hippocampus

Question 7

What seahorse shaped structure dominates the medial temporal lobe?

What are its components from bottom to top?

Answer 7

hippocampal formation

Bottom: subiculum (next to the entorhinal cortex) –> hippocampus proper-> dentate gyrus

Question 8

What are the sectors of the hippocampus? Which layer is extremely susceptible to hypoxia-ischemia (most sensitive brain tissue)?

Answer 8

CA1-CA4

Layer 1 (Sommer’s sector) is susceptible

Question 9

What are Schaefer collaterals? What do they likely function in?

Answer 9

Schaefer collaterals are the hippocampus pyramidal branches that project to CA1 through the subiculum back to the entorhinal cortex to form a closed feedback loop

probably important in memory consolidation

Question 10

How many synapses are in the hippocampal formation?

Answer 10

3!

entorhinal cortex–> dentate granule cells (synapse 1) –> (perforant path through the subiculum)–> hippocampus pyramidal cell dendrites (CA3) (synapse 2)–> (form the alveus and the fimbria)

hippocampal pyramidal brs. (Schaefer collaterals) project to CA1 –> entorhinal cortex (synapse 3)

Question 11

What does the fimbria become when it leaves the dorsal surface of the hippocampus?

Answer 11

the fornix

Question 12

What would a hippocampal lesion cause?

Answer 12

anterograde amnesia (short and short to long consolidation), especially for declarative memory (facts, names, places)

Question 13

Where do stimulus associations occur in the brain?

Answer 13

amygdala

Question 14

How does afferent to efferent information flow through the amygdala?

Answer 14

lateral –> medial

Question 15

What are the 2 major efferent fiber bundles of the amygdala?

Answer 15

stria terminalis (to the septal area and hypothalamus)

ventral amygdalofugal pathway (to the hypothalamus and the thalamus)

Question 16

What is the “mesolimbic system”?

Answer 16

Dopamine from the ventral tegmental area of the midbrain project to the frontal cortex and regulates emotional behavior movement

Question 17

Where can some drugs of abuse modulate dopamine in the mesolimbic system?

Answer 17

at the VTA or at the nucleus accumbens

Question 18

What is the blood supply to the amygdala?

Answer 18

anterior choroidal br. of ICA

Question 19

What is the blood supply to the hippocampus?

Answer 19

branches of the PCA

Question 20

What can amygdala lesions cause?

Answer 20

short term memory, placidity, and sexual changes

in pt SM, the amygdala is damaged bilaterally and she cannot recognize fear or show normal signs of fear

Question 21

What is Klucer-Bucy syndrome and what can cause it?

Answer 21

Certain bilateral medial temporal lobe lesions in experimental animals produce a constellation of signs called Kluver-Bucy syndrome (K-B) including, loss of fear, compulsive oral exploratory behavior, and hypersexuality.

in humans, pts are very placid and have changes in their sexuality

Question 22

What happened to pt Henry Molaison when he had a bilateral anterior medial temporal lobectomy for intractable epilepsy?

Answer 22

permanently without short-term memory for names, faces, events, etc.–> no anterograde memory

he was stuck in the past

Question 23

What happened to pt Clive Wearing who developed problems with his medial temporal lobe and inferior frontal lobe after contracting HSV1 encephalitis?

Answer 23

he had significant retrograde memory loss and only 20 seconds of useful anterograde memory

he was stuck in the present!