L&M Lecture 5-6 Classical Conditioning PDF

9/10/2024 Classical Conditioning Classical conditioning ○ Learning to predict and react to what is about to happen Through repeated experience, a neutral event becomes a signal for an upcoming, meaningful event ○ Unconditioned stimulus: a biological...

9/10/2024 Classical Conditioning Classical conditioning ○ Learning to predict and react to what is about to happen Through repeated experience, a neutral event becomes a signal for an upcoming, meaningful event ○ Unconditioned stimulus: a biologically significant stimulus that naturally evokes a response without prior training ○ Unconditioned response: the naturally occurring response to an unconditioned stimulus ○ Conditioned stimulus: a stimulus or cue that, through training, evokes a conditioned response ○ Conditioned response: the trained response to a conditioned stimulus in anticipation of the unconditioned stimulus is predicts Classical conditioning in The Office ○ US: altoid ○ UR: reach ○ CS: chime ○ CR: reach Ivan Pavlov ○ Russian physiologist who was interested in digestive function ○ Established basic principle of acquisition and extinction of conditioned responses (Pavlovian/classical conditioning) Pavlov’s dogs ○ Neutral stimulus: in CC, a stimulus which initially does not produce a specific response Classical conditioning ○ Appetitive conditioning: conditioning in which the unconditioned stimulus is a desirable event Food, physical touch, pleasant odor, etc. ○ Aversive conditioning: conditioning in which the unconditioned stimulus is an undesirable event Shock, painful stimulus, air puff to eye, etc. Little Albert experiment Classical conditioning in Little Albert ○ US: noise ○ UR: fear (crying) ○ CS: rat ○ CR: fear (crying, avoidance) Eyeblink conditioning ○ Puff of air to the eye (US) innately produces eyeblink (UR) ○ CS is a tone or light, which comes to produce an eye blink after repeated training  ○ A form of aversive conditioning often studied in both humans and rabbits ○ Typically, conditioned response builds gradually over many trials (acquisition) ○ The UR and CR can differ UR is a fast, strong blink occurring at the onset of the air puff (US) Initially, the CS does not produce a response After extensive training, the CR emerges: a slow, anticipatory blink prior to the US Classical conditioning ○ Conditioned response Can be same as UR (salivation) Can be different: allows learner to prepare for what is about to happen approach/avoidance, defensive behaviors Can occur at different times than the US (blinking eye before airpuff) ○ Acquisition of CR Develops over repeated experience Faster when US and CS are stronger/more salient Generalizes to similar stimuli Depends on the timing of the CS and US Timing affects acquisition ○ Delay conditioning Onset of CS precedes US; no gap between CS and US; both end at same time Leads to fastest acquisition ○ Simultaneous conditioning Slower acquisition ○ Trace conditioning CS and US are separated by an interstimulus interval (ISI) Duration of ISI impacts speed of acquisition Slower learning than delay conditioning ○ Backwards conditioning CS occurs after US Usually does not lead to learning, order matters Extinction ○ The process of reducing a learned response to a stimulus by ceasing to pair that stimulus with a reward or punishment ○ Even after extinction, CR can persist in a number of ways  Spontaneous recovery after a delay or due to a change in context (renewal) Rapid reacquisition (previously extinguished CR can be relearned quicker) Disinhibition (strong/arousing stimulus leads to renewal of extinguished CR) Extinction vs counterconditioning ○ Unlearning a conditioned response is not a simple matter of forgetting the original association ○ Extinction involved forming a new, inhibitory response to a CS ○ Counterconditioning replaces the previous CR with a new, desirable response New response should be incompatible with previous undesired CR Ex: training patients to relax while imagining increasingly stressful stimulus (systematic desensitization) 9/12/2024 Classical Conditioning Conditioning in complex environments ○ Example: conditioned taste aversion as a result of getting sick after eating something Compound conditioning ○ Simultaneous conditioning of two cues, usually presented at the same time Conditioned response to the compound (both stimuli together) is stronger than response to individual stimuli ○ Overshadowing: an effect seen in compound conditioning when a more salient cue within a compound acquires more association strength, and is more strongly conditioned, than does the less salient cue Salad example: ranch dressing has stronger flavor than lettuce, so it is more likely to generate a CR (disgust) on its own Blocking ○ A two phase training paradigm in which prior training to one cue (CS1 to US) blocks later learning of the second cue when the two are paired together in the second phase of training (CS1 + CS2 to US) Blocking: surprise drives learning ○ The blocking effect shows that simple co-occurrence (CS followed by US) isn’t enough for conditioning to occur  The new stimulus (CS2) could predict the US just as well as the old stimulus (C1S), so why was the new association blocked? ○ Learning depends on surprise: a mismatch between what is predicted and what occurs If the US is different (stronger or weaker) from what we expect, there is a prediction error In blocking effect, there is no prediction error since CS1 already perfectly predicts the US Contextual conditioning ○ Stimuli that compose a context act together as a CS Context acts as background cue that also become associated with the US ○ Fear conditioning in mice Mouse first explores a new context (testing chamber) Conditioning (tone followed by aversive shock causes fear CR) After conditioning, CR can occur due to context alone ○ Context can include both the external environment (exteroceptive context) and internal bodily states (interoceptive context) Exteroceptive: room, location, smells, decorations Interoceptive: mood state, deprivation state, hormonal state, memory of recent events Contextual conditioning and drug use ○ Conditioned compensatory responses: an automatic biological response that is opposite to the effect of a drug Cues that are consistently associated with drug use cause expectation of drug’s effect on body (compensatory response) The body acts to maintain homeostasis: the tendency of the body to gravitate toward a state of equilibrium or balance Larger doses required to counteract compensatory response and achieve the same high, contributing to increase in tolerance Conditioned tolerance is context dependent: overdoses are more likely to occur in different environments where the same cues are not present ○ Siegel examined the effect of of contextual cues on conditioned compensatory responses Three groups of rats given large doses of heroin: Same tested group: previous (small) dose in the same room Different tested group: previous (small) dose in a different room (change in context) First time tested group: no previous dose  Context and extinction ○ Extinction: break the association between CS and US Repeatedly present CS in absence of US Over time, learn that the CS no longer predicts the US, leading to decrease in CR Involves formation of a new, inhibitory response to the CS ○ Exposure therapy: repeated exposure to fear or anxiety inducing stimuli Example: treating PTSD Contextual cues become associated with highly traumatic events Experiencing same contextual cues leads to defensive fear response Exposure therapy used to reduce conditioned fear response ○ Exposure therapy is widely used and often leads to short term reductions in negative responses; however, high rate of relapse (return of fear response) ○ Why? Once acquired, a learned association will tend to generalize across contexts (it’s easy to elicit CR in different situations) Those learned associations are more difficult to extinguish in context-general manner Be oversensitive to threat signals, since you want to be ready whenever a threat is present ○ Renewal If an association is formed in Context A but extinction occurs in Context B, CR is renewed when returning to Context A 9/17/2024 Classical Conditioning continued Context and extinction ○ Spontaneous recovery With passage of time, previously extinguished CR returns ○ Delay usually involves a change in context: as time passes, the present becomes less and less similar to the extinction context ○ Context is an important factor in the acquisition and extinction of CR ○ How can we improve the efficacy of extinction Extinction cues: stimuli that aid retrieval of inhibitory CS-US association that was formed during extinction Mental reinstatement: explicitly train patient to recall the treatment period when CS is encountered  Multiple contexts: reduce the context-specificity of extinction by conducting in many different situations and internal states ○ Bias toward context-general acquisition but context specific extinction Renewal when returning to original conditioning context Renewal in new environment that is different from extinction context Spontaneous recovery after delay Persistence of CR is especially strong for negative associations Quiz 2 Review ○ Habituation is a decrease in strength of a reflexive response after repeated exposure to a stimulus ○ False: Habituation only occurs with highly emotional or arousing stimuli ○ Sensitization is demonstrated in Aplysia when, after shocking the tail, lightly touching the siphon causes a stronger gill withdrawal reflex ○ In classical conditioning, the unconditioned response occurs without any training or conditioning ○ Extinction of a CR to a CS is most effective when extinction occurs in many different contexts where the CS appears ○ Major difference between classical conditioning and habituation in how behavior changes in response to a stimulus over time: CC creates an association, habituation weakens an association ○ Last question: explain how habituation, sensitization, and classical conditioning serve different roles in allowing an organism to adapt to their environment