Limbics

Question 1

Papez ciruit:

Answer 1

hippocampus, fornix, mammilary bodies, (hypothalamus), anterior thalamus, cingulate gyrus

Question 2

What are the 2 structures that make up the hippocampal formation? How are they arranged in relation to one and other?

Answer 2

the dentate gyrus and the hippocampus proper

arranged as 2 interdigitating Cs with a lamellar organization.

Question 3

What are the major cell types of the hippocampus?

Answer 3

granule cells of the dentate (small) and large pyramidal neurons of the hippocampus proper.

Question 4

Describe the layered organization of the hippocamputs. What kind of cortex is the hippocampus

Answer 4

3 layered = allocortex
molecular layer (dendrites), compact layer (cell bodies), and polymorphic layer (interneurons)

Question 5

What are the divisions of the hippocampus proper?

Answer 5

4 subfields CA1, CA2, CA3, CA4

Question 6

What are the major inputs of the hippocampus? Where do they come from?

Answer 6

cholinergic input from the medial septal nucleus via the fornix (dentate gyrus and the CA fields)
glutamatergic input from the entorhinal cortex via the perforant path (dentate gyrus only)

Question 7

What are the 3 major outputs of the hippocampus?

Answer 7

1. CA fields to the septal nuclei and anterior hypothalamus via the precommissural fornix
2. from CA fields to mammillary bodies via the postcommissural fornix.
3. CA1 to the enterhinal cortex (directly or via the subiculum)

Question 8

What is the tri-synaptic loop?

Answer 8

1. glutamatergic inputs from the enterhinal cortex synapse on the granule cells of the dentate gyrus via the perforant path.
2. Granule cells project to CA3 via mossy fiber system
3. CA3 projects to CA1 via Schaffer Collateral System
4. CA1 project to the enterohinal cortex.

Question 9

What are the 2 major nuclear groups of the amygdala? What is the direction of information flow?

Answer 9

Basolateral division and the cortico-medial division.
Basolateral: cortex like and neo cortex associated nuclei.
cortico-medial: non-cortex-like nuclei.
information flow: from the basolateral to the medial division

Question 10

What is the input to the amygdala?

Answer 10

processed sensory input from the cortex, thalamus, hypothalamus, and some brainstem areas for autonomic and viscero/sensory function to the basolateral division.

Question 11

What are the efferents of the amygdala?

Answer 11

sends reciprocal efferents to most of the parts of the cortex that it gets projections from. but, central nucleus (part of cortico-medial) has a very strong connection with the hypothalamus and brain stem.

Question 12

What are the major fiber systems of the amygdala?

Answer 12

Stria terminals: from median division (medial-cortical group) to many places, but especially hypothalamus
ventral amygdalofugal pathway: projects to the prefrontal cortex and mediodorsal thalamus, as well as the hypothalamus, brainstem, and spinal cord. also largely medial-cortical (central nucleus).
Both pathways are bidirectional

Question 13

What is the orbital and medial prefrontal cortex? Connections?

Answer 13

ventral surface of the frontal lobe. lots of connections with hippocampus and the parahippocampal complex.

Question 14

What is the hippocampus main function?

Answer 14

declarative memory/conscious recollection (as opposed to procedural or working memory or storage of long-term memories/familiarity).
Also may be important for spatial memory: place fields fire APs when rat passes through a particular part of the environment

Question 15

What diseases is the hippocampus especially susceptible to?

Answer 15

ischemia, Alzheimer’s, and epilepsy, which selectively attack CA1.

Question 16

What should I know about the hippocampus and epilepsy?

Answer 16

many seizures come from the temporal lobe. in autopsy studies, many pts with epilepsy have hippocampal sclerosis– loss of principal neurons of the hippocampus. but cause/effect sequence is not clear.

Question 17

What should I know about adult neurogenesis and the hippocampus?

Answer 17

adult neurogenesis does occur in the hippocampus.

Question 18

What are the experiments showing that the amygdala is involved in fear?

Answer 18

kluver-bucy- monkeys with bilateral temporal lesions show flat affect and decreased fear response
stim to the amygdala in humans = instant feelings of fear; damage = flat affect
Urbach-Wiethe = lesions to the amygdala
Emotional learning circuit in animals: sound + shock response experiment.

Question 19

What parts of the amygdala cause loss of fear when lesioned?

Answer 19

lateral amygdala, central amygdal

Question 20

What are the orbitofrontal cortex/medial prefrontal cortex associated with?

Answer 20

reward, conflict, and emotional processing, especially when connected with the amygdala.
also associated with personality changes, including disinhibition

Question 21

What diseases might be importantly associated with cingulate cortex?

Answer 21

depression. overly high levels may also produce anxiety that is treatable with antidepressants. may treat depression with deep brain stimulation