Limbic System Flashcards
What does the limbic system control?
mood
emotion
feelings
motivation
critical for memory
What are the two reasons why the limbic system is difficult to study?
anatomically all the different structures are interconnected, so lesions one willa ffect function of another
physiologically hard to measure output of “feelings”
Why is understanding the limbic system so clinically relevant?
50% of patients will be treated for mood disorders
What are the 8 structures of the limbic system?
amygdala
hipocampus
septal nuclei
nucleus accumbens
medial prefrontal/anterior cingulate
vetnral trgmental area
anterior and dorsomedial nuclei of thalamus
mammillary nuclei
Where does the hippocampus project to in limbis system pathways? Via what tract of fibers?
to the hypothalamic mamillary bodies and the septal nuclei
via the fornix thorugh a C-shaped route
Where do the mammilary bodies project to in the limbis ystem pathways? Via what tract of biers?
to the anterior thalamic nuclei via the mamalothalamic tract
Where does the amygdala project to in the limbic system pathways? Through what fibers?
to the septal nuclei via the stria terminalis (located lateral to the fornix)
Where does the mibrain project to via the hypothalamis?
the forebrain in the medial forebrain bundle
Through what tract does the hypothalamus project to the brain stem and spinal cord?
the dorsal longitudinal fasciculus
All areas of the limbic systems are involved in circuits that somehow invove the….
hypothalamus - because it exerts control over the ANS, which mediates output for emotion
What 4 neurotransmitters are particularly active in the limbic system?
norepinephrine from the locus ceruleous (pons0
serotonin from raphe nucleus of the midbrain, pons and medulla
dopamine in the mesolimbic system
acetylcholine from the nucleus basilis and septal nuclei
Again, where does NE come from? 5HT?
NE from the locus ceruleus of pons
5HT from the raphe nuclei of midbrain, pons and mdulla
What is dopamine particularly important for the mesolimbic pathway?
pleasure and reward for behavior
Where are the dopaminergic neurons of the mesolimbic system and where do they project to?
ventral tegmental area of the midbrain
project ot nucleus accumbens, medial prefrontal cortex, amygdala and septal nucleu via the medial forebrain bundle
What are the affects of cocaine and amphetamine on dopamine?
cocaine blocks reuptake of DA
amphetamine increases DA secretion (and blocks reuptake)
Lesions of what area and blocking of what receptors will result in a decrease in drug seeking behaivor?
lesion of the VTA or nucleus accumbens
blocking DA receptors
Why is treating drug addiction so hard in terms of the mesolimbic pathway?
The mesolimbic pathway is also involved in the pleasure of natural rewards like food and sex
What is the clinical importance of the nucleus basalis?
you lose is in AD - no ACh - memory deficits
What is the primary role of the amygdala?
fear conditioning
What is the affect of amygdala lesions?
- no fear conditioning
- prior fear conditioning goes immediatley extinct after lesion
What symptoms would you see in a prefrontal lobe syndrome?
- impariment in goal directed behavior
- lack of emotion in decision making (lack of risk aversion)
- Poor social judgement (antisocila behavior)
- Poor emotional control (increased impulsivity)
NO CHANGE IN INTELLIGENCE
What are the etiologies to prefrontal lobe syndrome, specific to the segments….
dorsolateral PFC involved in working memory, so damage causes the inability to “folow thorugh”/godl directed behavior
orbital frontal cortex has connections to the amygdala, so without it, you are more pront to fits of anger
ultiamatley, the prefrontal cortex is inhibitory to the amygdala, which is excitatory to the hypothalamus, so you have an uncontrolled amygdala telling the hypothalamus to alter autonomics
What is the role of the hippocampus?
memory
What were the symptoms of HM’s bilateral medial temporal lobectomy?
anterograde amnesia and temporally graded retrograde amnesia (loss of old memories that are more recent to the surgery)
specifically, loss of excplicit or declarative memory with conservation of implicit memory
why was implicit memory spared in HM?
it doesn’t require the hippocampus
What is the disease that results in dilateral damage to the amygdala from mineral deposits?
Urbach-Wiethe Disease
What are the symptoms of Urbach-Wiethe Disease?
- impaired reocgition of emotion - especially anger and fear
- inability to differentiate between similar emotions (like anger and fear)
- Memory loss especially for information with emotional content
What’s the triad of symptoms in PTSD?
- re-experiencing phenomena - flashbacks
- avoidance of situational triggers
- hyperarousal - increased anxiety of what;s to happen
What is the etiology of PTSD found through fMRI studies?
decreased medial prefrontal, so disinhibtion of the amygdala and subsequent increase in amygdala activity
WHat are the general symptoms of schizophrenia?
fregmentation of thought, action and mood
positive symptoms - delusions and hallusinations
negative symptoms - social withdrawal
What is the US incidence of schizophrenia?
1%
What are the two “hypotheses” in schizophrenia?
- that dopamine receptor activity is too high
- That glutamine NMDA activity is too low
What ttreatments do we do we utilized if we take the dopamine hypothesis as true?
Block dopamine receptors
haloperidol - DA2 receptor blocker
closapine - CA2 receptor blocker, 5HT receptor blocker, blocks glue receptor to increase glutamate concentration
What proof do we have that glutamine is related to psychotic symptoms?
phencyclidine (PCP) blocks the nDMA receptor and causes psychotic symptoms
How how do you treat schizophrenia thorugh the glutamate arm?
increase glutamate receptor activity
What are the 3 general symptoms of depression?
- anhydnia
- sleep wake disturbance
- social withdrawal
What is th eincidence of depression in women compared to men?
20% women, 13% men
What NTs are implicated ind epression?
monoamines: NE and 5HT
thought to be low
What are the three general kinds of anti-depressants?
MAO inhibition to block NE and 5HT degradation
Tricclics: block reuptake of NE and 5HT by blocking the transporter
SSRIS (fluoxetine): block reuptake of serotonin only
Why is there a long latency for depression treatments to take?
it may depend on affecting neural plasticity
What is the triad of symptoms in Korsakoff’s syndrome?
- disorder of immediate memory - no new memory
- disorientation in space and time
- Confabulation - complete fabrications of info
What is the cause of korsakoff’s syndrome?
chronic alcoholism and related nutritional deficits
specifically, B1 thiamine deficiency
What is Kluver-Bucy Syndrome?
When you have bilateral medial temporal lobe damage (originally described in monkeys after bilateral surgical removal of amygdala, hippocampus, and temporal cortex)
What two issues are likel to have bilateral medial temporal lobe damage?
stroke or encephalitis
What are the 4 symptoms of Kluver-Bucy?
- oral tendencies
- changes in emotions - neutral affect
- hypersexuality
- Visual agnosia (inability to discriminate visual stimuli)
WHat are the 4 symptoms of AD?
- memory loss
- mood change: depanx
- motor dysfunction
- complete loss of ocgnitive funciton
What is th eincidence of AD in 85+
50%
What is the etiology of AD?
- loss of cholinergic input to hippocampus form the nucleus basalis
- loss of neuron sin multiple brain areas
- presence of neurofibrillary tangles of taue proteins and beta-amyloid plaques
Why do we treat AD patients with Donepezil (aricept)?
it’s an anticholinesterase, so increases concentraiton of ACh
What is chronic traumatic encephlalopathy?
it’s a progressive neurodegenerative disease cause by repeated head trauma
What are the symptoms of CTE?
memory impairment - anterograde amnesia
executive dysfunction
depression
apathy
decreased impulse control
increased aggressiveness
What is the etiology of CTE?
generalized brain atrophy - esp prefrontal corte, temporal lobes, and parietal lboes
neurofibrillaty tau protein tangles present
