Limbic System

Question 1

describe the limbic system in a nutshell

Answer 1

• emotionally significant stimuli activate sensory pathways that trigger HYPOTHALAMUS to modulate HR, BP, respiration (cahnges accompanying emotional response)
• info about emotionally significant stimuli also conveyed to CEREBRAL CORTEX, to integrate MOTOR RESPONSES to stimuli
• process of MEMORY and LEARNING is integrated into the system

Question 2

What major parts of the brain are associated with the limbic system?

Answer 2

• hippocampal formation (hippocampus, fornix, dentate gyrus)
• amygdala
• hypothalamus
• cingulate gyrus
• anterior, lateral dorsal, and dorsal medial nuclei of thalamus
• limbi association cortices

Question 3

function of amygdala

Answer 3

• formation and storage of info related to emotional events (long-term memory formation)
• help us recognize when we are in danger or fearful of something

Question 4

lesion to amygdala

Answer 4

• become docile
• affect memory formation, emotional sensitivity, learning and retention
• depression and anxiety

Question 5

input and output of limbic system

Answer 5

• input: entorhinal cortex projects to dentate gyrus via perforant pathway , synapsing on granule cells
• output: granule cells –> CA3 pyramidal neurons –> Sheaffer collaterals –> CA1

(note: CA1 cells give rise to fornix)

Question 6

Where is the limbic association cortex?

Answer 6

medial surface of frontal, parietal, temporal lobes (mesolimbic structures)

Question 7

Which gyri are part of the limbic association cortex?

Answer 7

• orbitofrontal gyrus
• paraterminal gyrus
• subcallosal gyrus
• cingulate gyrus
• parahippocampal gyrus
• temporal pole (entorhinal cortex)

Question 8

Which structures are involved in the circuit of Papez that regulates emotion?

Answer 8

• hypothalamus with mamillary body
• anterior thalamic nucleus
• cingulate gyrus
• hippocampus

Question 9

Describe and draw the Circuit of Papez. note the reciprocal step

Answer 9

1) cortex <–> CINGULATE GYRUS (RECIPROCAL)
2) cingulate gyrus –> hippocampal formation (via cingulum)
3) hippocampal formation –> hypothalamus with mamillary body (via fornix)
4) hypothalamus/mam. body –> anterior thalamic nuclei (via M-T tract)
5) anterior thalamic nuclei –> CINGULATE GYRUS
6) CINGULATE GYRUS –> cortex

REPEAT

KEY: reciprocal between cortex and cingulate gyrus

Question 10

Describe and draw the Circuit of Maclean (current theory). note the reciprocal step

Answer 10

1) PFC/Association Cortex –> cingulate gyrus/hippocampal formation
2) Association cortex <–> hippocampal formation –> amygdala (RECIPROCAL)
3) hippocampal formation/amygdala –> hypothalamus/mam. body (via fornix)
4) hypothalamus/mam. body –> PFC/association cortex

REPEAT (note: NO anterior thalamic nuclei; addition of amygdala)

KEY: reciprocal between hippocampus and association cortex/PFC

Question 11

if left hippocampus damaged?

Answer 11

auditory/vocal memory loss

Question 12

if both hippocampi removed?

Answer 12

anterograde amnesia

Question 13

TRUE or FALSE: hippocampus has a direct role in emotion

Answer 13

FALSE –> indirect role in emotion; direct role in explicit/declarative memory, memory consolidation and learning from emotional experiences

Question 14

Which part of the limbic system is most specifically involved with emotional experience?

Answer 14

amygdala

Question 15

What is the lateral amygdala linked to? what is its main function?

Answer 15

• linked to neocortex
• stimulate = fear –> anxiety

Question 16

What is the medial amygdala linked to? what is its main function?

Answer 16

• linked to striatum
• connects motor and brainstem

Question 17

What structure connects the 2 amygdalae?

Answer 17

anterior commissure

Question 18

lateral hypothalamus function vs ventromedial hypothalamus?

Answer 18

• lateral hypothalamus = pleasure center
• ventromedial hypothalamus = aversion (satiety) center

Question 19

which 2 nuclei make up the reward centre of the brain?

Answer 19

• septal nuclei
• nucleus accumbens

Question 20

bilateral lesion to frontal gyri

Answer 20

apathy; indecisiveness; difficulty concentrating

Question 21

bilateral lesion to orbital cortex

Answer 21

unstable emotional behaviour; loss of inhibition; inappropriate social behaviour

Question 22

bilateral lesion to temporal pole (entorhinal cortex)

Answer 22

fearlessness

Question 23

bilateral lesion to parahippocampal gyrus

Answer 23

anterograde amnesia

Question 24

basic game plan of the limbic system? main role of amygdala? main role of hippocampus?

Answer 24

cortex –> LAC –> amygdala/hippocampus –> cortex

• amygdala: link stimuli with emotion –> object recognition –> PROGRAM AND ORGANIZE RESPONSE TO POTENTIAL THREAT
• hippocampus: reflect more complex features of environment –> spatial relationships –> LEARN AND REMEMBER

Question 25

2 efferent pathways of the amygdala?

Answer 25

- ventral amygdalofugal path to: 1) thalamus, 2) hypothalamus, 3) rostral cingulate gyrus and orbitofrontal cortex and septal nuclei --> CONSCIOUS PERCEPTION OF EMOTION (pleasure and reward centre) - stria terminalus path to: 1) hypothalamus, 2) nucellus accumbens (euphoria) --> MOTOR PLANNING

Question 26

What is damaged in Korsakoff's Psychosis? What is the result?

Answer 26

- anterograde amnesia - damage to hippocampi, MD nucleus of thalamus, mamillary bodies

Question 27

4 major NTs delivered to limbic areas?

Answer 27

- dopamine - serotonin - norepinephrine - acetylcholine

Question 28

Describe midbrain dopaminergic projections.

Answer 28

- from: midbrain (VTA) and SNc - via: medial forebrain bundle - to: limbic areas

Question 29

what disease is mimicked when there is an increase in dopamine?

Answer 29

schizophrenia

Question 30

What is the hypothesis behind schizophrenia?

Answer 30

increased dopamine response in nucleus accumbens --> PFC dysfunction

Question 31

Describe ascending serotonergic projections.

Answer 31

- from: reticular formation (raphe nuclei) - via: medial forebrain bundle - to: limbic areas, striatum and cerebral cortex

Question 32

Describe noradrenergic projections.

Answer 32

- from: locus coeruleus - via: medial forebrain bundle - to: limbic system, entire cerebral cortex

Question 33

Describe basal forebrain cholinergic projections.

Answer 33

- from: basal forebrain cholinergic neurons (incl. Nucleus Accumbens, Septal Nuclei) - via: diverse pathways - to: limbic system, cerebral cortex

Question 34

degeneration of which neurons begins Alzheimer's Disease?

Answer 34

cholinergic neurons