Which structure in the limbic system is responsible for learning and maintenance of a link between a stimulus and its emotional value?
amygdala
What is the output tract of the amygdala called (as a structure) and where is its termination?
stria terminalis
terminates in thalamus/hypothalamus
What are the output fibers of the hippocampus called (as a structure) and where does it terminate?
fornix (fimbria anteriorly)
terminates in hypothalamus
What are the components of the limbic system?
1. limbic lobe
2. septal nuclei
3. amygdala
4. hippocampus
5. (nucleus accumbens)
What structure is just deep to the uncus?
amygdala
What structure is immediately deep to the parahippocampal gyrus?
hippocampus
What are the components of the "reward system"?
1. nucleus accumbens
2. medial forebrain bundle (MFB)
3. septal nuclei
4. hypothalamus
5. frontal cortex
6. ventral tegmental area (VTA) in midbrain
Which structure is the dentate gyrus associated with?
hippocampus
dentate gyrus = characteristic dark staining "spiral" formation in cross-section
What structure in the limbic system is responsible for learning and declarative memory (memory for facts, events, faces, places, etc.)?
hippocampus
What happens when a person undergoes a bilateral medial temporal lobotomy? Which damaged/lesioned structure in specific is responsible for the effects?
syndrome: Kluver-Bucy
symptoms:
-placid, flat affect
-fearless
-inappropriate social and sexual behavior (hypersexuality in animals, not humans)
-hyperoral and overly curious
-visual agnosia
-memory loss
damaged/lesioned structure responsible for effects: amygdala
True or false: The hippocampus (especially CA1 cells) and the globus pallidus are particularly vulnerable to damage by anoxia.
true
Which of the following statements about the hippocampus is FALSE?
C. bilateral removal of the hippocampus affects a person's IQ and their
ability to consolidate/lay down new declaritive memories
What is the function of the hypothalamus?
Homeostasis via
Endocrine system regulation
ANS regulation &
Limbic system regulation
What gives input to the hypothalamus?
- non-neuronal inputs
- brainstem (input/output)
- retina
- rostral limbic structures (input/ouptput)
- cerebral cortex (ouput via thalamus)
In what area of the brain is the limbic lobe?
- most medial part of temporal lobe
- C-shaped medial border of hemisphere
What structures make up the limbic lobe?
- septal nuclei
- subcallosal gyrus
- cingulate gyrus
- isthmus of the cingulate gyrus
- parahippocampal gyrus
- uncus
What are the two major sources of ACH in the brain?
septal nuclei
basal nucleus of forebrain
What types of behavior are affected by lesioning the septal nuclei?
rage behavior
hyperemotionality
foraging
alteration in sexual behavior
ANS effects
What are some of the functions of septal nuclei?
sexual behavior
role in developing plasticity (learning and memory)
source of cholinergic input to hippocampus
What are some of the functions of the nucleus accumbens?
role in addictive behaviors
receives (dopaminergic) input from ventral tegmental area (VTA) of midbrain --> "rewards"
Which nucleus appears to connect the lenticular/lentiform nucleus (i.e. putamen and globus pallidus) to the caudate nucleus in certain ventral cross-sections?
nucleus accumbens
What are 2 effects cocaine and/or methamphetamine have on the dopamine pathway?
more dopamine in the synaptic cleft at nucleus accumbens
(some addicts) adaptive increases in some DA receptor subtypes (e.g. D3) in nucleus accumbens
(tend to normalize in remission)
Which of the following is considered part of both the limbic system and the basal ganglia?
A. nucleus accumbens
What are the components and ordering of the "limbic loop"?
central nucleus: cognitive events or emotional signals from ANS input; hypothalamus and brainstem output
basolateral nucleus: cortex input; hypothalamus and brainstem output
What are the inputs and outputs of the amygdala?
inputs: highly processed
-sensory
-prefrontal cortex
-hippocampus
-brainstem
-all cortex areas
-visceral afferents (hypothalamus and brainstem)
-olfactory stria (olfactory input)
outputs: widespread
-cortex
-hippocampus
-hypothalamus
-brainstem
What is the function of the amygdala?
responsible for learning and maintenance of link between a stimulus and its emotional value
stimulation --> fear, anxiety
if lesioned --> Kluver-Bucy syndrome
orchestrates emotional and drive-related behavior through connections with brainstem, hypothalamus, and cord
If the amygdala is lesioned unilaterally, will the subject be able to undergo aversive conditioning?
No, there must be bilateral lesioning of the amygdala in order for aversive conditioning to be disrupted. A subject may undergo aversive conditioning if only one amygdala region is lesioned.
Which of the following is NOT an effect of bilateral amygdala damage?
B. can retain old memories but cannot form new ones
Where is the hippocampus?
medial temporal lobe (part of cortex --> layered arrangement)
deep to parahippocampal gyrus
postero-lateral to amydala
medial to inferior horn of lateral ventricle
What is this structure and what are its main components?
What is the function of the entorhinal cortex of the hippocampus?
EC (entorhinal cortex): funnels input from all sensory cortices to hippocampus
What is the function of the hippocampus?
role in long term potentiation (LTP): perforant path
learning and declarative memory (memory for facts, places, faces, etc.)
Hippocampal cells produce BDNF (brain-derived neurotrophic factor) that has some protective function (e.g. against cortisol) but defense is overwhelmed in chronic stress
involved in "place" memory
involved in navigation (especially right hippocampus)
new neurons are born in adult hippocampus
Match each of the following types of memory (letter) with their associated cortical input/output (number).
A) Declarative
B) Procedural
C) Emotional
1. striatum (basal ganglia); cerebellum
2. amygdala; limbic system
3. hippocampus; parahippocampal region
A:3
B:1
C:2
What are the effects of bilateral hippocampus removal, as seen in the famous patient HM?
inability to lay down (i.e. consolidate) new declarative memories
old memories intact (probably cortex related)
no change in intellect/IQ
no problems with procedural memory
(
dysfunctional navigation/"place" memory)
What is long term potentiation (LTP) and what cortical structure is often associated with it?
LTP is the molecular process which strengthens groups of synapses that are repeatedly used.
LTP is associated with the hippocampus (perforant pathway)
What structure is this? What pathway do the lines represent? What part of the pathway does each line refer to? What mental process is this pathway associated with?
structure: hippocampus with dentate nucleus
lines represent: perforant pathway
(1)yellow line: entorhinal cortex to dentate nucleus
(2)pink line: dentate nucleus to CA3
(3)purple line: CA3 to CA1
(4)green line: CA1 to subiculum
(5)red line: subiculum back to entorhinal cortex
the perforant pathway is associated with Long Term Potentiation (LTP)
What is the "basic limbic circuit"?
-Basic limbic circuit is a loop involving 4 structures mainly
-2-way connections, except hypothalamus to thalamus
-Output to body via hypothalamus, for ANS control
-Can get somatic actions thru projections to cortex
-As an aside—can think of septal nuc and hypothal as siamese twins when it comes to connections—basically same for each.
What is the "hippocampal circuit" (i.e. Papez circuit)?
Consider hippo circuit—output via fornix to hypothal, specifically mamm—remember we said mam involved in memory—then info relayed to ant nuc of thal by mamm-thalam tract, thence to cing cortex and through entorhinal back to hippo. Also, intimate connections between hippo and amygdala—allowing for influence of emotions on learning—This is papez circuit—he got circuit right but messed up on function—not really emotion/but laying down of new declarative memories.
What is the function of the stria terminalis? Where are its origin and termination?
The function of the stria terminalis is to transmit signals from the amygdala to the septal nuclei, hypothalamic, and thalamic areas of brain (and vice versa).
origin: corticomedial division in amygdala
termination: ventral medial nucleus of thalamus
What is the "amygdala circuit"?
REMEMBER THERE are strong connections between amygdala and hippocampus—learning is often easier if there is some emotional content/context...
Where are the septal nuclei located?
both sides of the midline where the septum pellucidum extends ventrally to the anterior commissure
neurons blend imperceptibally with frontal cortex (region of subcallosal gyrus)
anterior to hypothalamus
What are some examples of what you would expect to change in a lab rat that suffers damage to the septal nuclei?
increased rage
foraging behavior
alterations in sexual behavior
Which statement is false?
E. like the hippocampus, the amygdala and septal nuclei are considered part of the cerebral cortex
Is the amygdala inolved in eating behaviors? If so, how?
Yes, the amygdala receives input from the olfactory system and then transmits this information as an output signal to the feeding/eating centers in the hypothalamic nuclei
The fornix forms the anterior wall of which cranial structure?
interventricular foramen
What feelings are generated when the amygdala is stimulated?
fear
anxiety
(sometimes rage)
deja vu
What is the major input source of information to the hippocampus? What is its major output route?
input: enterorhinal cortex (EC): receives sensory info from association cortex
output: enterorhinal cortex (EC): delivers info to hypothalamus
What is the cause of an uncal herniation?
Normally the parahippocampal gyrus rests on thetentorium (not shown here), but when thereis an expanding lesion (such as hemorrhage) in the forebrain, the parahippocampal gyrus is “pushed” over the incisura, the free, stiff edge of the tentorial dura that partially encloses the midbrain. This is called an uncal herniation. The blood supply to the midbrain is compromised, resulting in coma or death.
True or False: The hippocampus is often suspected as the epileptogenic foci (i.e. origin of abnormal electrical activity) in the brain.
True
Which structure is NOT involved in consolidating a new declarative memory?
C. septal nuclei
Where are the "place" cells, which aid in navigation and place recognition, located in the hippocampus?
C. CA1 (aka Sommer's sector)
Would the dentate gyrus be more articulated and easier to identify in the rostral or caudal portion of the hippocampus?
rostral hippocampus
What cerebral arteries are associated with the hippocampus?
posterior cerebral artery
What is the 1 main input into the limbic system and what is its 2 major outputs?
