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103_3_full - PSYC 103 Winter 2010 Lecture 3 Classical...

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Unformatted text preview: PSYC 103 Winter 2010 Lecture 3 Classical (Pavlovian) conditioning A conditional relationship emerges between the meaningful stimulus and the previously neutral stimulus.! US - unconditional stimulus - biologically significant
 stimulus (food)! UR - unconditional response (salivation)! CS - conditional stimulus - previously neutral
 stimulus (bell)! CR - conditional response (salivation)! Excitatory: CS signals the presence of a US Training CS Test US CS Inhibitory: CS signals the absence of a US UR CR Conditioning techniques Excitatory conditioning Eye-blink conditioning •  Normally used in rabbits •  A brief CS (e.g. tone) followed by a US (e.g. cheek shock) sufficient to produce a blink. •  After a number of pairings the CS will evoke a blink when presented alone Moore (1972): Conditioned rabbits to a 1200 Hz tone and tested tones of different frequencies: generalization and generalization decrement generalization extinction 3 Conditioning techniques Excitatory conditioning Autoshaping •  Commonly used in pigeons •  An acrylic panel is illuminated (CS), then food (US) is delivered into a hopper. •  After a number of pairings the pigeon will come to peck the panel acrylic panel hopper 4 Autoshaping movie Conditioning techniques Excitatory conditioning Conditioned suppression •  Normally used in rats •  After learning to press a lever for food, a CS (e.g. tone) is paired with a mild shock (US). •  After several CS-US pairings, the CS will come to suppress lever pressing Stimulus CS Responses -  Suppression ratio to measure learning: a/(a+b) Where: a= lever pressing during the CS b= lever pressing during the inter-trial interval 6 Conditioned suppression movie Conditioned suppression Tone without shock Tone + shock Acquisition and extinction of conditioned suppression by rats to a 60-second conditioned stimulus (CS) that was paired with foot shock (adapted from Hall & Pearce, 1979). Conditioning techniques Inhibitory conditioning CS signals the absence of US Conditioned inhibitor Light+tone no shock Tone shock Mean suppression ratios for rats given excitatory conditioning with a tone intermixed among trials with a light-tone compound followed by nothing (adapted from Zimmer-Hart & Rescorla, 1974). Conditioning techniques Inhibitory conditioning Revealed by: retardation and summation tests e.g. Pearce, Nicholas & Dickinson (1982) Group Experimental Inhibitory conditioning tone → Shock tone+light → no Shock bell → Shock Control Small CR to Tone+light compound Retardation test light → Shock Summation test bell vs. light+bell light → Shock Slower learning about light in Experimental Group than in Control Group Weaker responding to bell+light than to bell 10 Nature of associative learning A neural model of excitatory learning Aplysia Carew, Hawkins & Kandel (1983) -  Either the mantle or the siphon were stimulated. -  Stimulating one of these (the CS+) signalled a shock to the tail -  Stimulating the other (the CS-) signalled no shock -  The duration of siphon withdrawal (the CR) became longer during the CS+ than CS11 Nature of associative learning A neural model of excitatory learning Behavior Siphon mantle Siphon + shock Mean duration of siphon withdrawal by Aplysia to a stimulus that was either paired with shock (CS+) or presented by itself (CS-) on test trials that were conducted before and after conditioning (adapted from Macphail, 1993). Nature of associative learning A neural model of excitatory learning Neural pathways in aplysia, Kandel & Hawkins (1992) -  Two sensory neurons (CS+ and CS-), which are stimulated by an electrode, are connected to a motor neuron that withdraws the gill (CR) -  A third sensory neuron is excited by tail shock (US) -  All these neurons are connected to a modulatory interneuron - Hawkins et al. (1983): When one sensory neuron is followed soon after by a tail shock, its ability to excite the motor neuron is increased. 13 Nature of associative learning A neural model of excitatory learning Neural Activity Mean percentage of change in motor neuron activity in Aplysia to stimulation of one sensory neuron that was paired with tail shock (CS+) and to another sensory neuron that was never followed by shock (CS-), on test trials that were conducted before and after conditioning (adapted from Macphail, 1993). Nature of associative learning A memory model of associative learning -  Detection of the CS or the US in the sensory register excites a memory representation of these events - The US also activates a response to produce the UR - Learning can result in S-R associations ( e.g. Aplysia) or CS-US associations 15 What is learned? Two theories S-R learning: CS elicits CR directly S-S learning: CS activates representation of US S-S / S-R Differentiation Nature of associative learning A memory model of associative learning CS-US learning: Colwill & Motzkin (1994): Rat subjects Conditioning Devaluation Tone → Food Test Food → Illness Tone vs. Light Light → Sucrose Sucrose → nothing Weaker responding to Tone than Light -  Results are consistent with CS-US account of learning but are difficult to explain with an S-R account of learning -  Holland (1990) conducted a similar experiment and found, in the final test stage, that when allowed to drink water during the test stimuli, rats made ingestive responses (e.g paw licking) to the stimulus whose US had not been poisoned, and aversive responses (e.g. head shaking) to the other stimulus 18 US devaluation: Example Holloway and Domjan 1993 Sexual Pavlovian conditioning in the domesticated quail Light (CS) paired with access to female Copulation at the end of the trial --> Light elicits approach response What happens when drive is reduced? US Inflation Increase preference for salt with a Na+ deficiency CS: Bitter tasting water, US: salt Train, induce deficiency in both groups, test with bitter water (w/o Na) Animals in ‘Quinine--Salt’ group drink much more water! Types of stimulus-stimulus learning A. Serial conditioning -  A sequence of stimuli precedes the US, e.g.: Light → Tone → Food Holland & Ross (1981) showed that after such training, the response normally evoked by the light (e.g. rearing) was replaced by the response normally evoked by the tone (e.g. head jerking) - The presence of the light excites a memory of the tone and causes the rat to respond as if it were present B. Sensory preconditioning Rizley & Rescorla (1972): Stage 1 Light → Tone Stage 2 Test Tone → Shock Light Fear CR At test, the light excites a memory of the tone, which in turn excites a memory of shock 21 Types of stimulus-stimulus learning C. Second-order conditioning Stage 1 Stage 2 CS1→US CS2 →CS1 CS2 comes to evoke a CR -  CS2 enters into an association with CS1, which in turn excites a memory of the US as a consequence of stage 1 training. -  Rashotte, Griffin & Sisk (1977): Autoshaping procedure with pigeons. White and blue key-lights as CS1 and CS2. CS1 extinguished after stage 2. Results showed that CR to CS was weakened by this treatment. Supports the above analysis. -  Rizley & Rescorla (1972): Conditioned suppression procedure with rats. Tone and light as CS1 and CS2. They also extinguished CS1 after stage 2. Results showed that CR to CS was NOT weakened by this treatment. Contradicts the above analysis. -  Rescorla (1980): When CS1 and CS2 are similar = CS2-CS1 learning. When CS1 and CS2 are dissimilar = CS1-CR learning. 22 Nature of US representations Two characteristics/properties of US representations: (1)  Specific – Characteristics that make the US unique and recognizable (e.g. its duration, flavor) CS can become associated with the specific characteristics of the US (e.g. its flavor) (2) Affective – Characteristics that the US has in common with other stimuli and reflect its motivational properties blocking is unaffected by a change in the US from water to food between stages 1 to 2. Shows the CS must have become associated with the general affective properties of the US in stage 1 Associations between CS and both these properties can form during excitatory cond. 23 Nature of the conditioned response The US can influence the CR A. Consummatory CR - Evoked when a CS retrieves specific properties of the US -  Mimics the response of the US Example: key pecks of pigeons differ depending on whether the CS signals food or water B. Preparatory CR - Evoked when a CS retrieves affective properties of the US. -  Appetitive CR might be an increase in activity … or approach -  Aversive CR might a reduction in activity… or withdrawal C. Compensatory CR - A CR that opposes, or compensates for the UR -  Frequently examined in studies of drug tolerance 24 Conditioned response : Influence of the US on the CR C. Compensatory CRs Siegel (1977) •  Reduction of the analgesic effects of morphine in rats with training •  Injection/handling cues = CS, Morphine = US •  Reduction in the effectiveness of CS (i.e. tolerance) = Conditioning •  Saline (placebo) injections lead to extinction; without injections full tolerance remains. Tolerance develops Saline injections No injection 25 Reflexive nature of the conditioned response CR can be maladaptive… Hearst & Jenkins (1974) - Pigeons autoshaped in a long arena. Key light and hopper separated by 60 cm. Subjects often missed the US as a consequence of not getting to the hopper in time. -  CR was still maintained! Williams & Williams (1969) -  Omission schedule -  Pigeons given conventional autoshaping. US omitted if CR (pecking) was performed. Pecking still continued! 26 ...
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