Limbic System -Bales Flashcards
What is the Papez circuit? What will bilateral lesions to this circuit cause?
hippocampus → hypothalamus (mammillary body) → thalamus → cortex (cingulate) → hippocampus
open circuit*
bilateral lesions=inability to acquire new memories
What is the septal region thought to play a part in?
emotion, thirst, learning, autonomic inhibitory functions and sexuality and orgasm
Rats will stimulate this over eating or drinking!
What does the septal nuclei connect with? (5)
cingulate gyrus
habenular nuclei (stria medullaris thalami)
hypothalamus (medial forebrain bundle -MFB)
hippocampus ( fornix)
amygdala (stria terminalis)
What are the functions of the anterior and posterior cingulate cortex?
Where do these limbic fibers go?
anterior=motor
posterior=sensory
hippocampus
What is Korsakoff syndrome? What symptoms will be seen?
Mammillary bodies preferentially degenerate in chronic alcoholism
amnesia
Where is the entorhinal cortex?
Where does this cortex receive and send info?
anterior half of the parahippocampal gyrus (BA 28)
receives cingular fibers and inputs to the hippocampus
What seahorse shaped structure dominates the medial temporal lobe?
What are its components from bottom to top?
hippocampal formation
Bottom: subiculum (next to the entorhinal cortex) –> hippocampus proper-> dentate gyrus
What are the sectors of the hippocampus? Which layer is extremely susceptible to hypoxia-ischemia (most sensitive brain tissue)?
CA1-CA4
Layer 1 (Sommer’s sector) is susceptible
What are Schaefer collaterals? What do they likely function in?
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
How many synapses are in the hippocampal formation?
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)
What does the fimbria become when it leaves the dorsal surface of the hippocampus?
the fornix
What would a hippocampal lesion cause?
anterograde amnesia (short and short to long consolidation), especially for declarative memory (facts, names, places)
Where do stimulus associations occur in the brain?
amygdala
How does afferent to efferent information flow through the amygdala?
lateral –> medial
What are the 2 major efferent fiber bundles of the amygdala?
stria terminalis (to the septal area and hypothalamus)
ventral amygdalofugal pathway (to the hypothalamus and the thalamus)
What is the “mesolimbic system”?
Dopamine from the ventral tegmental area of the midbrain project to the frontal cortex and regulates emotional behavior movement
Where can some drugs of abuse modulate dopamine in the mesolimbic system?
at the VTA or at the nucleus accumbens
What is the blood supply to the amygdala?
anterior choroidal br. of ICA
What is the blood supply to the hippocampus?
branches of the PCA
What can amygdala lesions cause?
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
What is Klucer-Bucy syndrome and what can cause it?
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
What happened to pt Henry Molaison when he had a bilateral anterior medial temporal lobectomy for intractable epilepsy?
permanently without short-term memory for names, faces, events, etc.–> no anterograde memory
he was stuck in the past
What happened to pt Clive Wearing who developed problems with his medial temporal lobe and inferior frontal lobe after contracting HSV1 encephalitis?
he had significant retrograde memory loss and only 20 seconds of useful anterograde memory
he was stuck in the present!
