Limbic System VII

Question 1

Limbic lobe starts and ends where/where are the two edges? Show it on a saggital and a coronal section

Answer 1

cingulate gyrus, parahippocampal gyrus.

Question 2

what two sulci are the edges of the cingulate gyrus? show on both coronal and saggital sections

Answer 2

from deep inside, outwards:

• callosal sulcus (which separates cingulate gyris from corpus callosum)
• cingulate sulcus

Question 3

what sulcus separates the parahippocampal gyrus from the rest of the brain?

Answer 3

collateral sulcus

Question 4

divisions of cingulate gyrus from back to front? clue: the names relate to the corpus callosum division names

Answer 4

• retrospenial cortex
• posterior cingulate cortex
• anterior cingulate cortex
• subgenual cingulate cortec

Question 5

4 important parts of the parahippocampal gyrus?

try and show them

Answer 5

1. piriform cortex (primary olfactory cortex) - at front
2. entorhinal cortex - the gateway for information entering and leaving the hippocampal formation
3. uncus - the hook - has the amygdala. At the front
4. hippocampus - at the back.

Question 6

what’s the white matter associated with the limbic lobe? what type of WM is it?

Answer 6

• cingulum. Meaning belt
• Associative - associates areas together that are in the same hemispheres.

Question 7

what cortical areas are involved in the limbic system?

Answer 7

• Obvious ones:
• cingulate cortex, hippocampus, parahippocampal gyrus, amygdala (in the uncus gyrus), Entorhinal cortex
• Non-obvious ones:
  1) medial orbitofrontal cortex (remember, the “orbit” means the eye socket, so its the cortex on the top of this.)
  2) temporal pole: the front of the temporal cortex!
  3) anterior insula (remember we just have two insula - anterior and posterior)

Question 8

what is the periaqueductal grey? role?

Answer 8

The periaqueductal gray is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. you can see it nicely in the cross section.

modulation of pain, sympathetic responses as well as the learning and action of defensive and aversive behaviors.

Question 9

three poles from an inferior view?

Answer 9

frontal pole, occipital pole, temporal pole

Question 10

can you tell me which thalamic nuclei relay info from:

1)pain and temp,
2) proprioception
3)auditory info
4) visual info

Answer 10

• Pain and temperature:
  Spinothalamic tract: This pathway relays pain and temperature sensations from the body to the thalamus. The specific thalamic nucleus involved is the Ventral Posterior Lateral (VPL) nucleus.
• Proprioception:
  Ventral Posterior Medial (VPM) nucleus: This thalamic nucleus receives input from the trigeminal nerve and relays proprioceptive information from the face, including jaw position and movement.
• Auditory information:
  Medial Geniculate Body (MGB): The MGB is the thalamic nucleus that receives auditory input from the inferior colliculus in the midbrain. It then projects this information to the auditory cortex for further processing.
• Visual information
  Lateral Geniculate Nucleus (LGN):

Question 11

describe where anterior commissure and posterior commisure are and for what?

Answer 11

• anterior commisure: just above the optic chiasm. Function: relaying sensory information between the hemispheres, particularly for olfactory perception.
• posterior commissure: on the side of the pineal gland. Function: reflexive eye movements, particularly the pupillary light reflex. The fibers of the posterior commissure also contribute to visual integration and the coordination of eye movements between the hemispheres.

Question 12

The limbic system has four main functions and four main loops! What are they?

Answer 12

• emotions and drive: Amygdala circuit
• memory: hippocampal circuit
• homeostatic functions: hypothalamic circuit
• olfaction: rhinencephalon

Question 13

The limbic lobe is, in a way, between the neocortex and hypothalamus. THat means it’s function is basically what?

Answer 13

EMotional association - SURVIVAL!
associates external input and phenomena with emotion - positive or negative?

We learn about what’s good or bad and how to survive through this!

Question 14

Consequence of removal of medial temporal lobe?

Answer 14

KLUVER-BUCY syndorme
* no fear anymore
* emotional blunting
* visual agnosia
* inappropriate sexual behaviour

Question 15

what’s visual agnosia?

Answer 15

an impairment in recognizing visually presented objects

Question 16

Name 3 inputs to the amygdala & 3 outputs from amygdala?

Answer 16

Inputs from:

• sensory info relayed by thalamus - for all sensory info relayed by the Th, a copy is sent to the Amygdala for association
• Parallel info from prefrontal cortex: this helps the amygdala decide and “Know” what’s good/bad
• olfactory bulb & piriform cortex

Output to:

• hippocampus - to form memory and contextual association
• cingulum - higher cognitive functions - e.g., in danger, Amy activates the cingulum, which motivates you to escape
• hypothalamus –> hormonal response (pituitary gland), pain modulation (periaqueductal grey)
• brainstem nuclei – modulation of attention, motivation!

Question 17

3 amygdala pathways?

Answer 17

1. Stria Terminalis:
Bidirectional communication between the amygdala and other brain regions.
Involvement in emotional and autonomic regulation, reward processing, and higher-order cognitive functions.

2. Amygdalofugal pathway:
Carries information predominantly from the amygdala to other brain regions. (“fugal” comes from the Latin word “fugere,” meaning “to flee” or “to go away.”)
Modulation of emotional responses, regulation of autonomic functions, and influence on fear and stress-related behaviors.

3. Uncinate pathway:
Connects the anterior temporal lobe (including the amygdala) with the prefrontal cortex.
Integration of emotional and social information into decision-making processes.
Regulation of social behavior, empathy, and evaluation of emotional and social cues.

Question 18

what is the stria terminalis? What is the pathway?

Answer 18

• The stria terminalis is a prominent pathway in the brain that connects the amygdala with other regions, including the hypothalamus, septal nuclei, and prefrontal cortex. It consists of a bundle of white matter fibers that run along the lateral wall of the lateral ventricle.

PATHWAY:

• One branch of the stria terminalis extends amygdala –>hypothalamus , conveying emotional and autonomic signals to areas involved in regulating physiological responses.
• Another branch connects amy–> septal nuclei, which are involved in reward and social behaviors.
• Additionally, the stria terminalis sends fibers from amy –> prefrontal cortex, allowing for the modulation of higher-order cognitive processes related to emotion and decision-making.

Question 19

where are the septal nuclei and what are they for

Answer 19

nuclei right at bottom of septum pellucidum, in front of the anterior commissure

role: reward and reinforcement, social behaviours, it communicates with Amy, HIP, and many other things.

Question 20

what structure connects or allows communication between amygdala and septal nuclei, and for what aim?

Answer 20

STRIA TERMINALIS (white matter fibre bundles)

reward and reinforcement, social behaviours

Question 21

what happened to HM?

Answer 21

bilateral surgical removal of the medial temporal lobes - specifically, PARAHIPPOCAMPAL GYRUS including the hippocampus.

RESULT?

anterograde amnesia, which impaired his ability to form new long-term memories. His procedural memory was intact!

Question 22

3 parts of the hippocampal formation?

Answer 22

• hippocampus (/cornus ammonis (CA))
• dentate gyrus
• subiculum

Question 23

how can you identify the dentate gyrus of the hippocampal formation?

Answer 23

dense layer of granule cells forming a C shape

Question 24

how can you identify the dentate gyrus of the hippocampal formation?

Answer 24

dense layer of granule cells forming a C shape. PLays an important role in formation of new memories.

Question 25

gateway of HIP to the neocortex?

Answer 25

entorhinal cortex, through the subiculum of the hippocampus

Question 26

Two main circuits of hippocampus? Difference in roles?

Answer 26

• Trisynaptic circuit - for memory formation
• Papez circuit: role in emotional processing

Question 27

Outline the trisynaptic circuit

Answer 27

1. Dentate Gyrus: Incoming sensory information is first received in the dentate gyrus, which acts as a gateway to the hippocampus.
2. CA3 Region: The dentate gyrus projects its axons, called mossy fibers, to the CA3 region of the hippocampus.
3. CA1 Region: Neurons in the CA3 region send their axons, called Schaffer collaterals, to the CA1 region.
4. Subiculum: The CA1 region projects its axons to the subiculum, which serves as the final output of the hippocampus.

Question 28

Outline the Papez circuit

Answer 28

Hippocampal formation (subiculum) → fornix → mammillary bodies → mammillothalamic tract → anterior thalamic nucleus → cingulum → entorhinal cortex → hippocampal formation.

see slides

Question 29

what’s the rhinecepahlon and where to find it

Answer 29

= a part of the brain involved with smell (i.e. olfaction).

has two main structures:piriform cortex and amygdala

also has: entorhinal cortex and olfactory tubercle