Chapter 4 – Classical Conditioning: Mechanisms

1. 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

2. 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

3. Latent Inhibition (CS preexposure effect) LI Group Forward controlRandom control Phase 1 CS Nothing Nothing Phase 2 CS  US CSUS unpaired CS and US Test CS alone CS alone CS alone LI Group Forward controlRandom control Phase 1 bell nothing nothing Phase 2 bell food bell food unpaired bell and food Test bell alone bell alone bell alone

4. 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 LI groupCTA groupBackward control • phase 1 sacch nothing nothing • phase 2 sacch  LiCl sacch  LiCl LiCl  sacch • test sacch alone sacch alone sacch alone

5. 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

6. 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

7. 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?

8. US preexposure effect US preexposureForward controlRandom control Phase 1 US Nothing Nothing Phase 2 CS  US CSUS unpaired CS and US Test CS alone CS alone CS alone US preexposureForward controlRandom control Phase 1 Food nothing nothing Phase 2 bell food bell food unpaired bell and food Test bell alone bell alone bell alone

9. 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

10. 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 noisytasty • group 1 (LiCl) drink don’t drink • group 2 (Shock) don’t drink drink

11. 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

12. 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 higher-order conditioning can occur.

13. Higher-Order Conditioning (Second-Order) Exp. GroupControl Group phase 1 CS1 (light)US (shock) CS1 (light) /US (Shock) random phase 2 CS2 (tone)CS1 (light) CS2 (tone) --> CS1 (light  test CS2 (tone) alone CS2 (tone) alone • Can you think of an example of higher order conditioning that we handle every day?

14. 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.

15. Pigeons • GP 1 GP 2 • Key light (8 s)  Grain Key light (8 s)  Water • What procedure is this? • CS, US, UR, CR? CS, US, UR, CR? • CR is pecking the key in both cases • 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

16. 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?

17. Conditioned Cold Tolerance (Riccio et al.) • CS, US, UR, CR? • What if you tested them in a new room?

18. 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

19. 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?

20. 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

21. 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?

22. 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

23. Rats trained with context  Morphine • Test with context alone? • Showed increased withdrawal • Wet dog shakes • Paw tremors • Ear wipes • Head shakes • Body twitches • What if withdrawal occurs in new context? • Decreased withdrawal