6.1 Limbic System Flashcards
The limbic system links ___ and ___ aspects of behaviour
Cognitive and emotive
The limbic system is a collection of structures from which 3 encephalons?
- Telencephalon
- Diencephalon
- Mesencephalon
Is the limbic system a “separate”, well demarcated system?
- No
- It arises due to functional connectivity between various brain regions
Where is the limbic lobe? What gyri is it comprised of?
- Limus = rim
- Wraps around corpus callosum
- Comprised of cingulate, subcallosal and parahippocampal gyri
“Limbus” means rim. At a more conceptual level, what is the limbic lobe a rim between?
The phylogenetically older parts of the brain, and the young neocortex
Which part of the insula is thought to be part of the limbic system?
Anterior insular cortex
Which three structures comprise the hippocampal formation?
- Dentate gyrus
- Hippocampus
- Subiculum
Which CA region of the hippocampus is adjacent to the dentate gyrus vs subiculum? What is the meaning of CA?
Dentate: CA3
Subiculum: CA1
(“Cornu Ammonis” -> Ammon, Egyptian God, Alexander The Great)
These two cortices within the parahippocampal gyrus are where most sensory association areas funnel into
- Perirhinal cortex
- Parahippocampal cortex
The perirhinal and parrahippocampal cortices feed into this cortex, which then feeds into the hippocampus…
Entorhinal cortex
By which path does information travel from the entorhinal cortex to the hippocampus?
Perforant path
What happens to cortical sensory information once it reaches the hippocampus?
- It travels back out through the subiculum
- Travels back out to association areas
(Or, at least, this is one of the trajectories it can take)
How dooes subcortical information travel to and from the hypothalamus?
Via the fornix
Which two structures does the fornix connect the hypothalamus to?
- Mammillary bodies
- Septal nuclei
The basal forebrain and the septal nuclei are often considered part of the same structure, and sit ventral to the subcallosal gyrus. Which neurotransmitter do they produce?
Acetylcholine
In terms of brain structures, why can ACh be used to treat Alzheimer’s?
- Basal forebrain and septal nuclei are important for memory
- They produce ACh
- Giving ACh can give symptomatic relief
Which thamalic nuclei are thought to be involved in memory?
- Anterior nucleus
- Mediodorsal nucleus
- Midline thalamic nuclei
True or false: the mammillary bodies are not part of the hypothalamus
- False
- They are a part of the hypothalamus
Which hypothalamus-associated areas are involved in the medial diencephalic memory system?
- Mammillary bodies
- Septal nuclei
What kinds of memory is the hippocampus important for?
- Episodic (what did you do on your 19th Birthday?)
- Spatial (where did you park the Lancer?)
List the components of the Papez circuit in order
- Subiculum
- Fornix
- Mamillary bodies
- Mammillothalamic tract
- Anterior thalamic nuclei
- Internal capsule
- Cingulate gyrus
- Cingulum
- Parahippocampal gyrus (entorhinal cortex)
- Hippocampal formation
The amygdala is made of many nuclei, but is divided into three main groups of nuclei. What are these groups?
- Basolateral
- Corticomedial
- Central
The amygdala integrates information from cortical sensory areas, the thalamus, and the hippocampus. What kind of stimuli is it especially important for?
Aversive stimuli (loss aversion, fear-based selling)
Where is the amygdala located
Just anterior to the hippocampus in the medial temporal lobe
What does the amygdala provide an interface between?
Somatic expression of emotion (hypothalamus), and higher order emotion from the cortex.
(Stoicism/Zen Buddhism Interface)
Following temporal lobe removal, monkeys have good visual perception, but poor recognition. Why does this make sense, and what syndrome might accompany this?
- Makes sense because “what” stream is lost due to no more occipitotemporal
- Kluver Bucy syndrome will also occur (increased interest in sex, decrease in fear and aggression etc.)
You see a bear, and he looks pissed off. By which two routes does this information lead to fear, and which is faster?
Slow: thalamus, cortex, amygdala, consciousness
Fast: thalamus, straight to amygdala, consciousness
How does damage to the amygdala affect stress-induced illnesses and stress hormones?
- Lowers them
- Less fear response, less stress
Outline the four anatomical sections of the fornix
- Fimbria (runs alongside hippocampal formation)
- Crus (after splitting from HCP)
- Body (two Crus join)
- Columns (split back up)
What happens to the columns of the fornix at the level of the anterior commissure?
- Splits into anterior and posterior fibres
- Anterior run to septal region
- Posterior fibres run to mamillary bodies
Recall the inputs/outputs of the central nucleus of the amygdala
Input: Basolateral amygdala nucleus
Output: hypothalamus and brainstem nuclei
Recall the inputs/outputs of the basolateral nucleus of the amygdala
Input: hippocampus and sensory cortices
Output: central nucleus of the amygdala, ventral striatum, prefrontal cortex
Recall the inputs/outputs of the corticomedial nucleus of the amygdala
Input: olfactory bulb
Output: hypothalamus
