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).
1. striatum (basal ganglia); cerebellum
2. amygdala; limbic system
3. hippocampus; parahippocampal region
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?
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?
What feelings are generated when the amygdala is stimulated?
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.
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?
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?