limbic system (16) Flashcards
what are two good things that Papez figured out about the limbic system? what was his error?
- . Limbic system is involved in emotion
- Papez circuit describes the anatomy of the limbic circuit
- he was anatomically correct, but the components he identified only play a minor role in emotion
Explain the Kluver-Bucy experiment
Removed temporal lobes of an aggressive rhesus monkey
o Monkey became docile, over ate, ate inappropriate items, hyperoral, hypersexual
what were the conclusions of the Kluver Bucy experiement
Originally thought- that this was a confirmation of the Papez circuit, but later realized that emotions could be recapitulated by removing/damaging the amygdala is not a component of the papez circuit
list the 7 main limbic system components & downstream targets
- anterior & mid cingulate cortex
- amygdala
- hypothalamus
- periaqueductal gray (PAG)
- autonomic nervous system
- dorsal raphe nucleus (DRN)
- Locus coerules (LC)
what is the function of the ACC?
- recode the amygdala to gauge your emotional response
- involved in AFFECT
- stores long term emotional memories & operates thro the nervous system
- its ventral part: sadness
what is the function of the MCC?
- predict outcomes & resolve ambiguity
- motivational behaviors & response selection
- Its anterior part is active during fear & operates through its spinal projections to the skeletal motor system
- resolves conflict
what is the function of the amygdala?
invests sensory experience with emotion
main component in fear
what is urbach-wiethe disease?
calcification of the amygdala
what patient did the urbach-weieth disease happen to? what was the result?
- patient S.M. without the amygdala- inability to recognize & experience fear
- Lead to excessive risk taking, odd relations & financial decisions
- Tells you: amygdala is highly involved in fear!
what was the importance of the discovery found in the LeDoux lab?
hint: it had to do with the foot shock associated with a tone
- Condition fear response
- if you cut the auditory cortex off from the amygdala (which you would think would stop the response of being scared of the tone) you still got the fear response!
- This is because the amygdala gets a DIRECT input from the thalamus (without cortical processing) and thereby dominating the initial primary response to fear.
what is the function of the hypothalamus?
autonomic/hormonal control
our experience with fear
what is the function of the periaqueductal gray (PAG)?
coordinates behaviors: autonomic/skeletal
regulates ANS
where does the PAG project to?
nucleus of the solitary tract, dorsal motor nucleus of the vagus and intermediolateral nucleus
what is the function of the ANS in the limbic system?
skeletal motor output & memory enhancement
what is the function of the locus coeruleus (LC)
coordinates responses
enhances storage of emo memories
what is the function of the dorsal raphe nucleus (DRN)?
regulates mood
regulates secretion of serotonin & norepi
what are the two types of emotions?
primary & secondary
describe primary emotions. give an example. what structures are involved in primary emotion?
- “reflexive” (implicit). Linked with autonomic reflexes
- structures involved: amygdala, hypothalamus, PAG
- ex. fear
describe secondary emotions. what structures are involved in primary emotion?
- conscious emotions. Object & context dependent
- evaluating your emotional response
- structures involved: cortical limbic structures
where is the location of the PAG?
surrounds the aqueduct in the midbrain between 3rd and 4th ventricles
does PAG have the ability to do some memory of emotional responses?
heck no
when can “SHAM” rage occur?
when there has been a stroke/tumor in the hypothalamus/PAG
what is “SHAM” rage?
- Fully integrate rage without external control: primary emotion
- Ex. A fly on the nose & excess rage
- tells you the need for hierarchical system to coordinate behavior outputs according to the internal needs & external cortex of the organism
what are the effects of cortisol binding to glucocorticoid?
- Increase glucose levels & metabolism
- Increase AA metabolism
- Increase fat breakdown
- Increase memory
where does the MCC project to?
striatum, red nucleus, pontine nuclei (cerebellum) and cranial nerve motor nuclei for somatomotor driving of alpha motor neuron
is the PCC involved in emotion?
no
which area is especially and selectively vulnerable to emotional diseases such as depression?
the perigenual region (the genu around the corpus callosum)
which area is saddness & remembering sad events most prominently?
the ACC
in which cingulate cortex is happiness primarly found?
in the rostral part of the ACC
what is the response of electrically stimulating the MCC?
- it evokes complex skeletomotor response adapted to context
- Typically emotional relevant motor outputs (ie. Kissing)
- This is different from simple motor outputs that only involve stimulation of motor cortex
which of the cingulate gyri is considered the “facial region”
the anterior cingulate cortex
where does the facial region project to?
to the facial motor nucleus (muscles of facial expression) so you can make those ugly crying faces
what structures is considered the “key upstream & downstream coordinator of the limbic system”?
the locus coeruleus
who does the LC have reciprocal connections with to drive emotional memory formation?
the amygdala & limbic cortex
where is the LC located?
in the tegmentum of the metencephalon
what were “normal” people with short 5HT transporter allele found to have?
- you will have reduced functional interaction of ACC & amygdala, so they will be shrunken
- patients with this genetic modification (s5HTT) results in lower levels of transporter transcription and reduced 5HT uptake
- these patients have higher risk for developing depression and have shrunken ACC and amygdala
what is considered one of the most effective treatment options for depression?
SSRIs
where is the dorsal raphe nuclei located?
in the midbrain
explain why it takes about a month for the SSRIs to become effective?
- initially the 5HT levels are increased both at the level of the DRN and ACC
- these elevated levels cause DRN neurons to decrease their 5HT release in the ACC→therefore no net effect in the ACC
- but over time→ the autoreceptors are internalized & decreased therefore ultimately giving the rise to higher levels of 5HT in the ACC
