6.1 Limbic System

Question 1

The limbic system links ___ and ___ aspects of behaviour

Answer 1

Cognitive and emotive

Question 2

The limbic system is a collection of structures from which 3 encephalons?

Answer 2

• Telencephalon
• Diencephalon
• Mesencephalon

Question 3

Is the limbic system a “separate”, well demarcated system?

Answer 3

• No
• It arises due to functional connectivity between various brain regions

Question 4

Where is the limbic lobe? What gyri is it comprised of?

Answer 4

• Limus = rim
• Wraps around corpus callosum
• Comprised of cingulate, subcallosal and parahippocampal gyri

Question 5

“Limbus” means rim. At a more conceptual level, what is the limbic lobe a rim between?

Answer 5

The phylogenetically older parts of the brain, and the young neocortex

Question 6

Which part of the insula is thought to be part of the limbic system?

Answer 6

Anterior insular cortex

Question 7

Which three structures comprise the hippocampal formation?

Answer 7

• Dentate gyrus
• Hippocampus
• Subiculum

Question 8

Which CA region of the hippocampus is adjacent to the dentate gyrus vs subiculum? What is the meaning of CA?

Answer 8

Dentate: CA3
Subiculum: CA1

(“Cornu Ammonis” -> Ammon, Egyptian God, Alexander The Great)

Question 9

These two cortices within the parahippocampal gyrus are where most sensory association areas funnel into

Answer 9

• Perirhinal cortex
• Parahippocampal cortex

Question 10

The perirhinal and parrahippocampal cortices feed into this cortex, which then feeds into the hippocampus…

Answer 10

Entorhinal cortex

Question 11

By which path does information travel from the entorhinal cortex to the hippocampus?

Answer 11

Perforant path

Question 12

What happens to cortical sensory information once it reaches the hippocampus?

Answer 12

• 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)

Question 13

How dooes subcortical information travel to and from the hypothalamus?

Answer 13

Via the fornix

Question 14

Which two structures does the fornix connect the hypothalamus to?

Answer 14

• Mammillary bodies
• Septal nuclei

Question 15

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?

Answer 15

Acetylcholine

Question 16

In terms of brain structures, why can ACh be used to treat Alzheimer’s?

Answer 16

• Basal forebrain and septal nuclei are important for memory
• They produce ACh
• Giving ACh can give symptomatic relief

Question 17

Which thamalic nuclei are thought to be involved in memory?

Answer 17

• Anterior nucleus
• Mediodorsal nucleus
• Midline thalamic nuclei

Question 18

True or false: the mammillary bodies are not part of the hypothalamus

Answer 18

• False
• They are a part of the hypothalamus

Question 19

Which hypothalamus-associated areas are involved in the medial diencephalic memory system?

Answer 19

• Mammillary bodies
• Septal nuclei

Question 20

What kinds of memory is the hippocampus important for?

Answer 20

• Episodic (what did you do on your 19th Birthday?)
• Spatial (where did you park the Lancer?)

Question 21

List the components of the Papez circuit in order

Answer 21

• Subiculum
• Fornix
• Mamillary bodies
• Mammillothalamic tract
• Anterior thalamic nuclei
• Internal capsule
• Cingulate gyrus
• Cingulum
• Parahippocampal gyrus (entorhinal cortex)
• Hippocampal formation

Question 22

The amygdala is made of many nuclei, but is divided into three main groups of nuclei. What are these groups?

Answer 22

• Basolateral
• Corticomedial
• Central

Question 23

The amygdala integrates information from cortical sensory areas, the thalamus, and the hippocampus. What kind of stimuli is it especially important for?

Answer 23

Aversive stimuli (loss aversion, fear-based selling)

Question 24

Where is the amygdala located

Answer 24

Just anterior to the hippocampus in the medial temporal lobe

Question 25

What does the amygdala provide an interface between?

Answer 25

Somatic expression of emotion (hypothalamus), and higher order emotion from the cortex.

Question 26

Following temporal lobe removal, monkeys have good visual perception, but poor recognition. Why does this make sense, and what syndrome might accompany this?

Answer 26

• 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.)

Question 27

You see a bear, and he looks pissed off. By which two routes does this information lead to fear, and which is faster?

Answer 27

Slow: thalamus, cortex, amygdala, consciousness
Fast: thalamus, straight to amygdala, consciousness

Question 28

How does damage to the amygdala affect stress-induced illnesses and stress hormones?

Answer 28

• Lowers them
• Less fear response, less stress

Question 29

Outline the four anatomical sections of the fornix

Answer 29

• Fimbria (runs alongside hippocampal formation)
• Crus (after splitting from HCP)
• Body (two Crus join)
• Columns (split back up)

Question 30

What happens to the columns of the fornix at the level of the anterior commissure?

Answer 30

• Splits into anterior and posterior fibres
• Anterior run to septal region
• Posterior fibres run to mamillary bodies

Question 31

Recall the inputs/outputs of the central nucleus of the amygdala

Answer 31

Input: Basolateral amygdala nucleus
Output: hypothalamus and brainstem nuclei

Question 32

Recall the inputs/outputs of the basolateral nucleus of the amygdala

Answer 32

Input: hippocampus and sensory cortices
Output: central nucleus of the amygdala, ventral striatum, prefrontal cortex

Question 33

Recall the inputs/outputs of the corticomedial nucleus of the amygdala

Answer 33

Input: olfactory bulb
Output: hypothalamus