Psychology Fear & Anxiety

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PSY 339 Lecture
Fear Learning in Humans- Learning to be Afraid
Learning- a relatively permanent change in an organism’s behavior due to experience this occurs through ASSOCIATION – PAVLOV Classical Conditioning a previously neutral stimulus (CS)-red square- gets paired with the unconditioned stimulus (US) – lightening bolt- RESULT- CS elicits fear (CR) How do we measure fear in Pavlovian Conditioning? Freezing, Vocalization (ultrasonic for rodents), Increase in acoustic startle response, skin conductance- non- specific arousal Differential Conditioning- ITI- intertrial interval startles for in-between startle probes (when nothing is on the screen) Startle indexes magnitude of response of fear- ITI lowest, CS- low, CS+ highest Amygdala (fear conditioning/shock sensitization CS+ startle reflex) nucleus reticularis pontis caudalis (RPC) spinal & facial motoneurons (startle reflex), cochlear root neurons (abrupt noise-probe) Second-order conditioning- things which predict bad things to come (blue to red square, yellow to red light) CR magnitude is lower than first order conditioning (smaller reaction to blue square) What determines CS-US strength- not just association- but PREDICTABILITY of US, so unpaired US presentations will actually REDUCE CS-US strength, but unpaired is scarier- unpredictable US presentationsreduce conditioned fear, but increases anxiety (ITI goes up) CONTEXT conditioning Anxiety down for paired, up for unpaired

Grillon- blue light & shock in bank/casino/restaurant, no shock/predictable/unpredictable Where blue light always predicts shock CS+ is largest (present startle probes during CS+ for cued fear) CS+ and ITI don’t differ too much, anxiety is bigger in unpredictable roompresent startle probes during the ITI CS- is a safety signal

Learning fear through Instruction & Observation- acquires fear easily via learning through others w/ Phobias, no personal experience, but mostly through observational learning develops fear Problem with skin conductance- habituation, arousal ….CS+ high, CS- low, same w/ Pavlovian Neurobiology of fear Central nucleus of the amygdala that projects to diff. parts of the brain for CS+/CS-, cued fear (i.e. tone/shock) Double dissociation b/t fear potentiated startle (amgydala) vs. anxiety (BNST) Bed Nucleus Stria Terminalis (BNST) is not activated by conditioned stimuli, but by more diffuse cues in the environment (room you’re in, dark vs. light), via stress hormones- will have higher ITI startles/anxiety/context, no diff. in CS+ or CS- PairedCS+ high, CS-/ITI low

Unpaired CS+/CS-/ITI all high and same level
Unpaired but with CS- CS+/ITI high, CS- safety signal low
UNLEARNING FEAR
Extinction- when dangerous things become safe again, Acquisition (CS + UCS) ConditioningExtinction then stop pairing the US with the CS+ (CS alone)- will start to go down in startle Fear-potentiated startle takes longer to go down

* Recovery: startle response will go back up after period of rest, regardless of shock Spontaneous recovery (CS alone) Skin Conductance- good CS+ response in early in Extinction, but lower in later Extinction, high again in Spontaneous recovery (but would lower in repetition) *Fear Learning is completely context independentNOT context-dependent Unlearning is context dependent

* Reinstatement after Extinction (unpaired)- w/ NO delay
* increases fear in CS+
* During extinction, the context becomes safe- US presentations increase fear, and activate previously learned CS-US associations * If the UC are presented in context B NO reinstatement in context A * Aversiveness of a context activates CS-US association * CONTEXT-SPECIFIC- Unsignalled CSs in context B don’t reinstate fear in context A * Appears to depend on contextual learning Hippocampus Increased startle response in Spontaneous Recovery (delay) because of rest period, NOT because of contextreactivation of memory for unsignaled shock Renewal- Extinction is...
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