Classical Conditioning and Drug Effects

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Classical Conditioning and Drug Effects
Basic Classical Conditioning
The Unconditioned Stimulus
- a biologically relevant event
The Unconditioned Response
- a reflexive (unlearned) response to a
biologically relevant event
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Classical Conditioning and Drug Effects
Basic Classical Conditioning
- e.g., in Pavlovs original experiments, placing
meat powder on a dogs tongue (the US) produces
reflexive salivation (the UR)
- no learning required
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Classical Conditioning and Drug Effects
Basic Classical Conditioning
The Conditioned Stimulus
- initially elicits an orienting response, but is
biologically neutral
- the CS is generally paired with the US over
repeated presentations
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Classical Conditioning and Drug Effects
Basic Classical Conditioning
- e.g., in Pavlovs original experiments, a
metronome was activated (the CS) just before the
meat powder (the US) was placed on the dogs
tongue
- the metronome (CS) became a signal that
predicted the meat powder (US)
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Classical Conditioning and Drug Effects
Basic Classical Conditioning
The Conditioned Response
- once the CS becomes associated with the US, the
CS alone can produce a response (the CR)
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Classical Conditioning and Drug Effects
Basic Classical Conditioning
- e.g., in Pavlovs original experiments, after a
number of trials, the metronome alone (CS)
produced salivation (CR)
- although the CR is the same physical response
(salivation) as the UR, it is now the result of
associative learning
- CS produces anticipatory salivation in
expectation of the US
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Classical Conditioning and Drug Effects
Homeostasis
- a homeostatic system maintains itself with a
non-zero baseline state
- e.g., body temperature regulation
- baseline state is ? 37 C
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Classical Conditioning and Drug Effects
Homeostasis
- body temperature maintained at 37
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Classical Conditioning and Drug Effects
Homeostasis
- if temperature drops below baseline, the
regulating system works to increase it
- you start shivering to generate heat
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Classical Conditioning and Drug Effects
Homeostasis
- if temperature rises above baseline, the
regulating system works to decrease it
- you start sweating to dissipate heat
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Classical Conditioning and Drug Effects
Homeostasis
- any homeostatic system will try to correct
disturbances in either direction
- many examples of homeostatic systems in human
physiology
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
- administration of a drug such as morphine will
disturb multiple homeostatic systems in the body
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
- homeostatic mechanisms try to restore the
baseline state
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- each administration of a drug can be viewed as
a conditioning trial
- the effect of the drug (the US) reflexively
produces a compensatory anti-drug response (the
UR) as the body attempt to restore homeostasis
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- stimuli that regularly precede drug effects can
become CSs
- e.g., the preparation ritual, the surrounding
environment, early drug effects...
- these stimuli come to predict the onset of the
US (i.e., they reliably signal that the drug
effect is about to happen)
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- CSs that have become associated with the drug
effect US now produce anti-drug responses all
by themselves even before the actual drug effects
appear
- these compensatory CRs allow the body to be
better prepared to deal with the drug-induced
disturbance of homeostasis
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- learning to associate environmental CSs with
the drug effects ultimately reduces the ability
of the drug to disturb homeostasis
- the result is drug tolerance
- the same dose of a drug produces a
progressively smaller effect over a series of
administrations
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
before conditioning
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
after conditioning
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- the fact that drug tolerance is (at least in
part) a result of conditioning raises some
interesting questions...
1. What happens if the drug is now administered
in the absence of the CS?
- e.g., the drug is taken in unfamiliar
surroundings
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
no CS, so no CR
overdose
CS present
CS absent
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- if the CS is not present, there is no
compensatory anti-drug response
- this results in the failure of tolerance, or a
larger net effect of the drug
- may result in overdose even when the dose of
the drug is the same as is usually taken when the
CS is present
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- the fact that drug tolerance is (at least in
part) a result of conditioning raises some
interesting questions...
2. What happens if the CS is presented, but no
US follows?
- e.g., being in the usual drug-taking
environment, but not taking the drug
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Classical Conditioning and Drug Effects
Homeostasis and Drug Effects
withdrawal
US present
US absent
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- the CS produces the anti-drug CR
- there is, however, no US to push the system in
the opposite direction
- this produces a disturbance of homeostasis that
may result in withdrawal symptoms, which are
generally opposite to the drug effects
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- experimental studies have demonstrated that
such manipulations of the CS and US will produce
failure of tolerance or withdrawal in animal
models
- e.g., the work of Shepard Siegel and colleagues
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Classical Conditioning and Drug Effects
Drug Administration as Conditioning
- we can conclude on the basis of this evidence
that conditioning plays a major role in the
development of drug tolerance, the potential to
overdose, and the appearance of withdrawal
symptoms
- this may be relevant to the development of
effective treatment programs for drug dependence
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Classical Conditioning and Drug Effects
Questions?