Chapter 4: Classical Conditioning: Mechanisms

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Chapter 4 – Classical Conditioning: Mechanisms
• Important characteristics of the CS and US
– 1) Novelty of CS and US
• Latent Inhibition
– association account
– memory account
– Release from LI
• US preexposure
– 2) Intensity/saliency of CS and US
– 3) CS/US relevance (belongingness)
• Garcia and Koeling
– Bright Noisy Tasty water
– Belongingness
– 4) Stimulus Substitution
• Higher order conditioning
• Further evidence for stimulus substitution
– Jenkins and Moore (1973)
• Homeostasis
– Riccio
– Siegel
• CS and US Novelty
– We learn about novel stimuli more quickly
than familiar.
• First noticed by Pavlov.
– If the dog had had heard the bell a lot before it
was harder for it to learn the bell now
predicted food
•
Latent Inhibition (CS preexposure effect)
Phase 1
Phase 2
Test
LI Group
CS
CS  US
CS alone
Forward control
Nothing
CSUS
CS alone
Random control
Nothing
unpaired CS and US
CS alone
Phase 1
Phase 2
Test
LI Group
bell
bell food
bell alone
Forward control
nothing
bell food
bell alone
Random control
nothing
unpaired bell and food
bell alone
• Why are familiar stimuli less easily conditioned?
• 1) The associative interference theory
– Prior learning about the CS or US interferes with the animals
ability to learn new things about the CS or US.
• Learned irrelevance or safety?
– The animals learn the CS is irrelevant or safe in phase 1
– The Bell doesn’t lead to anything good or bad
» Habituation
– Let’s apply to taste aversion
•
•
•
phase 1
phase 2
test
LI group
sacch
sacch  LiCl
sacch alone
CTA group
nothing
sacch  LiCl
sacch alone
Backward control
nothing
LiCl  sacch
sacch alone
• learned irrelevance or safety
– the LI group
• saccharin is “safe” in phase 1
• This “safe” learning makes it harder to learn that
saccharin is now “unsafe”
– Input problem
– CTA group
• Didn’t learned saccharin is safe.
• neophobia
– which is confirmed
•
2) A memory interference theory of Latent Inhibition
– Perhaps LI occurs because animals have learned two things equally
well
• The CS is safe
• The CS makes me Ill
•
What happens at test?
– LI group
• memories compete
• “safe” and “bad”
– intermediate level of CR.
– CTA
• one memory
• “bad”
– stronger CR
– Backward group
• one memory
• “safe”
– least CR
•
This is an output problem
• Release from LI (Kraemer & Spear,
1992)
– Instead of testing right away wait for
21 days
• LI is the same as CTA group.
–conditioned responding increased
• why?
–Biological importance of memories?
»CS Safe?
»CS Dangerous?
•
US preexposure effect
Phase 1
Phase 2
Test
US preexposure
US
CS  US
CS alone
Forward control
Nothing
CSUS
CS alone
Random control
Nothing
unpaired CS and US
CS alone
Phase 1
Phase 2
Test
US preexposure
Food
bell food
bell alone
Forward control
nothing
bell food
bell alone
Random control
nothing
unpaired bell and food
bell alone
• CS and US Intensity and Salience
– We have covered this before
• louder or brighter CSs
• more flavorful or painful USs
– Can be manipulated indirectly
• Salt deprived rats
– taste aversions to a salty substance
– Learn quickly
• CS-US Relevance, or Belongingness
– Bright – Noisy – Tasty Water
• Garcia and Koeling (1966)
• Group 1 – bright noisy tasty  LiCl
• Group 2 – bright noisy tasty  shock
test both groups with a choice between
bright noisy
tasty
• group 1 (LiCl)
drink
don’t drink
• group 2 (Shock) don’t drink
drink
• this illustrates species-specific differences in
preparedness to learn
– taste  illness
– sounds /sights pain.
• Pigeons?
– use sight more than taste for foraging
• color and shape of seeds
– learn a visual cue (colored bead) goes with illness readily.
• Humans?
– spiders and snakes – shock
– Houses and flowers – shock
• What determines the nature of the
Conditioned Response?
– The Stimulus Substitution model (Pavlov)
• The CS becomes a surrogate US
• This is why the CR and UR are typically the same
– Salivation/Salivation
• This is one explanation for how higherorder conditioning can occur.
• Higher-Order Conditioning (Second-Order)
phase 1
phase 2
test
•
Exp. Group
CS1 (light)US (shock)
CS2 (tone)CS1 (light)
CS2 (tone) alone
Control Group
CS1 (light) /US (Shock) random
CS2 (tone) --> CS1 (light
CS2 (tone) alone
Can you think of an example of higher order conditioning that we handle
every day?
• Further evidence for stimulus substitution
– Different US’s produce different UR’s
• Food salivation
• Shock  withdrawal and aversion
• Puff of air to the eye  eyeblink
– Jenkins and Moore (1973)
• even subtle differences in the US can affect
the nature of the conditioned response.
•
Pigeons
•
•
GP 1
Key light (8 s)  Grain
•
What procedure is this?
•
CS, US, UR, CR?
•
CR is pecking the key in both cases
GP 2
Key light (8 s)  Water
CS, US, UR, CR?
– How the pigeons pecked the key depended on the US
– Food
• Peck like eating
• Rapid with beak closing when striking the key
– Water
• Peck like drinking
• Slower with beak open and swallowing behavior
• Learning and Homeostasis: A Special Case of Stimulus
Substitution
– For our bodies to work well we often have to maintain
physiological parameters within some acceptable limit.
• e.g., Body temperature (98.6 degrees)
• Walter Cannon
– Introduced term Homeostasis
• physiological mechanisms that serve to maintain critical aspects of the
body within acceptable limits.
• What happens when we get cold?
– compensatory reaction
• Wouldn’t it be more efficient, if we could anticipate when we
are going to get cold?
– Compensate ahead of time?
• Conditioned Cold Tolerance (Riccio et al.)
• CS, US, UR, CR?
• What if you tested them in a new room?
• Drugs and Conditioned drug effects.
– It is well known that people also become tolerant
to the effects of a drug
– Could this tolerance also be context specific?
• Siegel
– injected rats with 5.0 mg/kg of morphine every
day in the same room (context)
• Increased body temperature
• Decreased heart rate
• decreased sensitivity to pain
– Paw lick latency
– over time all of these responses decreased
• tolerance
• Was this tolerance the result of Pavlovian
conditioning?
– How would you find out?
• test in a new environment
– paw lick latency went back up
– temperature increased
– heart rate decreased
• CS, US, UR, CR?
• tolerance appears to be at least in part conditioned
– body learns to compensate for the action of the drug in an
attempt to maintain homeostasis.
• Drinking in bar at 10 pm
• Drinking at school at 10 am
•
Heroin Addicts
– large tolerance in normal surroundings.
– take the same dose in a novel place
• Many OD patients reported taking drug in new place
• Siegel has shown that rats are more likely to die from
high dose of a drug they are tolerant to
– If in new environment
• If Seigel is correct typical classical
conditioning findings should apply to this
situation.
– Extinction
• Repeated exposure to the environmental cues (CS) in
the absence of morphine (US).
– This has been shown
• What should happen if an animal had
repeated exposure to the testing environment
before the drug was injected to the animal?
– Known as?
• Note - Conditioned Tolerance is usually
demonstrated (tested) while presenting the US.
• using Novel CS2 vs. Trained CS1
– No tolerance in novel context
• Its not your typical test with CS alone
• Conditioned withdrawal effects
– The result of a more traditional test of Pavlovian
Conditioning
• CS alone
• Note – withdrawal effects are often opposite
of drug effects
– Cocaine – Euphoria
• Withdrawal - Depression
• Rats trained with context  Morphine
– Test with context alone?
• Showed increased withdrawal
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–
–
–
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Wet dog shakes
Paw tremors
Ear wipes
Head shakes
Body twitches
– What if withdrawal occurs in new context?
• Decreased withdrawal

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