Limbic System Flashcards
describe the limbic system in a nutshell
- 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
What major parts of the brain are associated with the limbic system?
- hippocampal formation (hippocampus, fornix, dentate gyrus)
- amygdala
- hypothalamus
- cingulate gyrus
- anterior, lateral dorsal, and dorsal medial nuclei of thalamus
- limbi association cortices
function of amygdala
- 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
lesion to amygdala
- become docile
- affect memory formation, emotional sensitivity, learning and retention
- depression and anxiety
input and output of limbic system
- 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)
Where is the limbic association cortex?
medial surface of frontal, parietal, temporal lobes (mesolimbic structures)
Which gyri are part of the limbic association cortex?
- orbitofrontal gyrus
- paraterminal gyrus
- subcallosal gyrus
- cingulate gyrus
- parahippocampal gyrus
- temporal pole (entorhinal cortex)
Which structures are involved in the circuit of Papez that regulates emotion?
- hypothalamus with mamillary body
- anterior thalamic nucleus
- cingulate gyrus
- hippocampus
Describe and draw the Circuit of Papez. note the reciprocal step
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
Describe and draw the Circuit of Maclean (current theory). note the reciprocal step
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
if left hippocampus damaged?
auditory/vocal memory loss
if both hippocampi removed?
anterograde amnesia
TRUE or FALSE: hippocampus has a direct role in emotion
FALSE –> indirect role in emotion; direct role in explicit/declarative memory, memory consolidation and learning from emotional experiences
Which part of the limbic system is most specifically involved with emotional experience?
amygdala
What is the lateral amygdala linked to? what is its main function?
- linked to neocortex
- stimulate = fear –> anxiety
What is the medial amygdala linked to? what is its main function?
- linked to striatum
- connects motor and brainstem
What structure connects the 2 amygdalae?
anterior commissure
lateral hypothalamus function vs ventromedial hypothalamus?
- lateral hypothalamus = pleasure center
- ventromedial hypothalamus = aversion (satiety) center
which 2 nuclei make up the reward centre of the brain?
- septal nuclei
- nucleus accumbens
bilateral lesion to frontal gyri
apathy; indecisiveness; difficulty concentrating
bilateral lesion to orbital cortex
unstable emotional behaviour; loss of inhibition; inappropriate social behaviour
bilateral lesion to temporal pole (entorhinal cortex)
fearlessness
bilateral lesion to parahippocampal gyrus
anterograde amnesia
basic game plan of the limbic system? main role of amygdala? main role of hippocampus?
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
2 efferent pathways of the amygdala?
- 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
What is damaged in Korsakoff’s Psychosis? What is the result?
- anterograde amnesia
- damage to hippocampi, MD nucleus of thalamus, mamillary bodies
4 major NTs delivered to limbic areas?
- dopamine
- serotonin
- norepinephrine
- acetylcholine
Describe midbrain dopaminergic projections.
- from: midbrain (VTA) and SNc
- via: medial forebrain bundle
- to: limbic areas
what disease is mimicked when there is an increase in dopamine?
schizophrenia
What is the hypothesis behind schizophrenia?
increased dopamine response in nucleus accumbens –> PFC dysfunction
Describe ascending serotonergic projections.
- from: reticular formation (raphe nuclei)
- via: medial forebrain bundle
- to: limbic areas, striatum and cerebral cortex
Describe noradrenergic projections.
- from: locus coeruleus
- via: medial forebrain bundle
- to: limbic system, entire cerebral cortex
Describe basal forebrain cholinergic projections.
- from: basal forebrain cholinergic neurons (incl. Nucleus Accumbens, Septal Nuclei)
- via: diverse pathways
- to: limbic system, cerebral cortex
degeneration of which neurons begins Alzheimer’s Disease?
cholinergic neurons
