The Limbic System Flashcards
limbic cortex
cingulate gyrus and parahippocampal gyrus
hippocampal formation
dentate gyrus- 3 layers- acellular, graunlar, and inner polymorphic
hippocampus- 3 layers- molecular, pyramidal, and inner polymorphic
contains 4 different cell regions- CA1, 2, 3, and 4
subiculum- composed of presubiculum, parasubiculum, and subiculum
transition zone between 6 layered entorhinal cortex and 3 layered hippocampus
amygdala anatomy
located beneath the uncus
contains 13 nuclei, of note:
basolateral basomedial lateral amygdalar centromedial, lateral, and central extended amygdala septal nuclei
cingulum
cingulate to amygdala tract/parahippocampal gyrus
fornix
output from hippocampus (entorihnal and subiculum) to hypothalamus
3 divisions: precommissural, postcommissural, and nonfornical
mammillothalamic tract
mammillary bodies to anterior and dorsal thalamus
anterior thalamic projections
input from fornix and mammillothalamic tracts
output to orbitofrontal cortex and cingulate
unicate fasciculus
originate in anterior temporal lobe, uncus, amygdala
enters orbitofrontal cortex
stria terminalis
output from amygdala terminateing in septum/hypothalamus
stria habelularis
septal nuclei to habenula
ventra amygdalofugal pathway
output from amygdala to hypothalamus
basolateral amygdalar circuit
set of connections that encodes and relays information pertinent to social signals and social acts
ex empathy or inference
spatial orientation
hippocampus-diencephalon tracts (fornix and mammillothalamic tracts) and the parahippocampal-retrosplenial cortex (cingulum) contains information with spatial info and memory
integration of emotional and visceral states
temporo-amygdala-orbitofrontal cortex via unicate fasciculus- activated during introspective thought
deactivated during goal directed tasks
damage results in mood disorders
insula
connections to insula are important for interepreting visceral autonomic responses and imposing them on salience
interoception- sense of the physiological condition of the body
kluver bucy syndrome
loss of normal fear and anger responses, hypersexuality, hyperphalagia, visual agnosia
difference between fear and anxiety
central nucleus of amygdala- acquisition and expression of fear to events
bed nucleus of stria terminalis- sustained, diffuse anxiety
connected via extended amygdala
fear conditioning
lateral amygdala is most important structure for conditioned fear
after training, the conditioned stimulus is sufficient to produce activity out of lateral amygadala activating fear pathways, indicating that a change in the firing pattern of the LA is associated with a learned fear response
importance of environment to fear response
lateral amygdala can adapt in response to training to conditioned stimulus, but the environment in which the training occured is also sufficient to elicit a fear response
extinction and reconsolidation
reconsolidation- allows information associated w/ the memory to be updated and reinforced. occurs everytime a memory is retrieved
extinguishing- not a degradation, substition of a new memory where an aversive pairing no longer exists
key processes of extinction
NMDA receptors in basolateral amygdala are required for acquisition of fear extinction
fear extinction associated with change in synaptic strength of projections from hippocampus to mPFC
PTSD
characterized by the inappropriate retrieval of fear memories leading to maladaptive arousal and stress
drugs interfering w/ reconsolidation or augementing extinction have some success w/ PTSD
optogenetics and dentate gyrus
encode contextual memory engrams- project to basolateral amygdala
stimulation via optogenetics created a false contextual fear memory
valence (fear or reward) could also be manipulated
theories of cognitive decision making
balance between emotional and congnitive processes
striatum, amygdala, mPFC, OFC, insular cortex
vs
dlPFC, aPFC, posterior parietal cortex
stress in goal directed behaviors
stress dependent changes in dlPFC correlate w/ decrease in goal directed behavior and increase in habitual behavior
signaling via norepi and glucocorticoids contribute to habitual behavior
stress impairs PFC functioning in decision making and increases risky decision making
insula is involved in social decision making
ok
integration of mood into decision making
insula and ventral striatum involved, w/ interpretation that involvement of VS signified reduced reward associated w/ decision making
hypothesis- activity in regions that regulate emotion and its reward (amygdala, ventral striatum) shift neural processing circuits that underlie subjective value assessments (OFC)
vmPFC
damage shows lover impact of social factors in decision making
implicit bias structures
amygdala, insula, cingulate, OFC
fast, automatic, no processing
explici bias structures
PFC, frontopolar cortex
slow, conscious, cognitively taxing
reapprasial
conscious override of unconscious assessments
stereotyping
priming of stereotyping done by vmPFC
output to dlPFC
dlPFC then has task of overriding or suppressing those stereotypes
extended amygdala
part of anxiety circuit
CRF
elevated CRF is hallmark of anxiety
differential expression in extended amygdala may explain sex specific differences to stress
CRF increases 5-HT receptor internalization, increasing anxiety like behavior (more so in women than men)
5-HT receptors are also internalized by CRF
drugs promoting 5HT are major target for therapy
BnST and stress
central amygdala projects to basal nucleus of stria terminalis w/ CRF- connection for anxiogenic action
