The Corticolimbic Circuit: Order Flashcards
elements of fear learning
(all fear is learned)
1. fear conditioning
2. fear extinction
3. recall
fear conditioning
learned to associate a previously neutral stimulus with an aversive experience
- usually freeze in response
fear conditioning & rat example
the tone was the conditioned stimulus (because they learned to associate it with pain) and the electrified grid is the unconditioned stimulus (because they don’t have to learn that it is painful).
amygdala and fear conditioning
The conditioned stimulus and conditioned stimulus, inputs converge on the same neuron in the BLA, a “fear neuron,” to include fear in the CeA
This leads to the potentiation of activation of the neuron and integrates the information (long-term potentiation – LTP)
one-trial learning
able to associate something with fear after a scary encounter w it once (ex. getting bitten by a snake and being scared off by a stick that looks like a snake)
neural response to salient visual stimuli
PET scan of participants exposed to CS visual paired with a loud noise
- this led to activation in amygdala and structures for arousal, encoding, integrating and pulvinar
*consider study about pulvinar density and response to visual stimuli
what is the relationship between the amygdala and the conditioned response
more activation of the amygdala is associated with a greater strength of the conditioned response
observational fear learning
watching someone else experience fear learning
(ex. watch someone see blue square and get shocked while you’re in the same room w shock equipment)
- leads to bilateral activation of the amygdala and greater activation in dACC when you see a blue square
SURROGATE US
Indirect fear learning
fear “warning”
- you are just told to be scared of smth (ex. warning sign)
- greater activation of the dACC, HF, insula by seeing a blue square and told you ‘may’ receive a shock from it
- greater activation in the amygdala
how does relationships affect fear learning
study of observer watching demonstrater get shocked and they learn the conditioned stimulus a day later
*more impactful when observing friend/ family be shocked
fear extinction
removing the response of fear to the CS
- in different context with same CS but no shock (US)
- eventually learns not to express fear
the medial prefrontal cortex and fear extinction
fear extinction creates a new memory and decreases the conditioned behavior with the rise of the extinction memory
dmPFC:
- Drives extinction neurons and inhibits fear neurons by directly inhibiting input in BLA
- Excitatory projects inhibit output (by influencing the ICMs which inhibit the CeA)
does fear extinction erase fear?
no, it is selective inhibition, which shapes output
- it doesn’t erase fear, just adds an extinction response
learning trace
through pathways between the amygdala and dmPFC, it mediates extinction of the original trace
fear recall
(24 hours later)
- exhibit extinction and no extinction behavior in different environments
the hippocampus formation and fear recall
It is a switch between safety and danger with just one of the conditions changing (ex. would fear a snake in the woods but not in a museum even if you see something that looked similar)
fear-conditioning context
- stimulus and context associated with fear boosts the response
- the hippocampus formation amplifies the CS bc its in the context associated with the fear, which induces a fear response in the CeA
fear extinction context
- the hippocampal formation and dmPFC inhibit the conditioned stimulus’ fear response and also activate the ICM’s which inhibit the CeA
- so there is no fear response without the proper context
fear potentiation in the fear-conditioning context
exaggerated reactions because of greater arousal when the amygdala is activated in a fear response
amygdala activity and strength of conditioned response
magnitude of activity in response to the conditioned stimulus predicts the strength of the fear response
Hippocampal formation and vmPFC extinction retention magnitude
magnitude of activity in vmPFC and HF predict its ability to successfully inhibit fear following extinction
what is the impact of a disconnect between the vmPFC and HF?
PTSD (inappropriate demonstration of fear)
- ability to integrate information in the vmPFC is impact by the ability to appropriately inhibit by dmPFC
hippocampal and amygdala lesions
amygdala lesions– don’t generate a fear response, but remember facts about the experiment
hippocampal lesions– normal fear response but poor recall of details from the experiment
how many universal facial expressions are there?
6 (but 5 agreed upon, surprise is a bit of an outlier)
happy, sad, fear, anger, disgust, … surprise
disgust and amygdala response
(to protect us from contaminants)
- registers in the insula but not the amygdala
anger and fear as an amygdala response
- strong activation of the amygdala
- CS is paired with bad things happening
STUDY: Orienting to fear in sclera and pupil
(briefly shown a fearful face so you’re not conscious of it directly)but the response cognitively changes, most activation in the sclera
STUDY: direct/ averted gaze and fear response
(anger, direct; anger, averted; fear, direct; fear, averted)
- more amygdala activity when its anger, averted and fear, direct
- because info of the threat is more unknown (what are they looking at, why are they looking at me with anger?)
size of pupil and association with amygdala response
undilated pupil is associated with a greater amygdala interaction
amygdala habituation
- overtime extinction of fear and lower amygdala activation leads to less of a response
- lower activity in the amygdala when repeated presentations of CS without the US (aversive simulation)
trait anxiety
tendency to experience anxiety when presented with a threat
- increases amygdala activity and decreases habituation
subjective evaluation
vmPFC activated by the amygdala which then goes back and forth with the dmPFC, which eventually inhibits the amygdala to reduce the fear response
