Reinforcement & Drug Effects
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Transcript Reinforcement & Drug Effects
Reinforcement
& Drug Effects
Lesson 15
Operant Conditioning
Acquisition & Maintenance of behavior
important for survival
Response Consequences
Response followed by satisfying
outcome
likely to be repeated
Acquisition & maintenance of drugtaking behavior ~
Operant Conditioning
SD
: B
SR
Classical vs. Operant Conditioning
SR
biologically important stimulus
B
R
Response S
SD
Discriminative stimulus
R available
Signals S
R ~
Response required to obtain S
Reinforcement
Strengthens behavior
increases responding
Positive reinforcement
B appetitive stimulus
Negative reinforcement
B terminates aversive stimulus
or prevents
Both are desirable outcomes ~
Punishment
Weakens behavior
decreases responding
Positive punishment
B aversive stimulus
Negative punishment
B terminates appetitive stimulus
or prevents
Both are undesirable outcomes ~
What are reinforcers?
Primary reinforcers
biologically important stimuli
Appetitive
food
water
sexual pleasure
drugs
Aversive
pain
Illness ~
Reinforcers (continued)
Secondary reinforcers
money
praise
drug paraphernalia
How do they become reinforcers?
Classical Conditioning
paired with primary reinforcers
starts
as a CS or SD
requires learning ~
Other Phenomena
Similar to classical conditioning
R
acquisition: B S
extinction: B No SR
spontaneous recovery
disinhibition
reacquisition
including magnitude & delay of RFT ~
Drug Self-administration (SA)
Animal model: drug taking behavior
Operant conditioning
Involves both...
Reward (positive RFT)
& escape/avoidance (negative RFT)
Self-administer same drugs as humans
Screening new drugs as potential
reinforcers ~
Drug Self-administration
operant conditioning
Press bar drug infusion ~
Drug
pump
Drugs as reinforcers
Addictive drugs
Postive reinforcers
Negative reinforcers
Aversive aftereffects
Obey laws of learning
same as any other learned response ~
Alcohol (ethanol)
Positive RFT
Pleasant feeling
Negative RFT
Reduces withdrawal effects
reduces stress
Aversive aftereffects
Hangover = withdrawal ~
Why does drinking persist?
Hangover as effective punishment?
Delay of RFT
Reward immediate
Punishment long delay
Magnitude of RFT
Smoking crack vs snorting cocaine
Greater euphoria & shorter delay
faster acquisition & slower extinction ~
Biological Bases of Drug
Reinforcement
Reinforcement Mechanisms
Positive reinforcement
R
B appetitive S
Mesolimbic Pathway
Negative Reinforcement
Widely distributed
Depends of specific drug effects ~
Reward Mechanisms
Olds & Milner
ESB
Mesolimbic Pathway
Ventral Tegmental Area (VTA)
Medial Forebrain Bundle (MFB)
Nucleus Accumbens (NA)
Role of Dopamine
Evaluating rewarding effects of drugs ~
The “Pleasure Center” of the Brain
Nucleus accumbens (NA)
DA activity mediates reward
DA activity in NA “pleasure”
Site of action for positive reinforcers
Natural reinforcers
Drugs ~
Mesolimbic Pathway
NA
MFB
Ventral
Tegmental Area
VTA
More evidence for dopamine role
Agonist: increases effects of NT
DA agonist euphoria
cocaine, amphetamine
Heroin opioids DA in NA
via Ventral Tegmental Area (VTA)
most addictive drugs
DA antagonists
Blocks learning
Also blocks responding for food ~
Alternate Reward Pathway
Medial Habenula
Habenulo-interpeduncular pathway
Na3b4 (Ach-R)
Modulates mesolimbic pathway
18-MC (18-Methoxycoronaridine)
Ibogaine derivative
Na3b4 antagonist
Stops self-administration ~
Negative Reinforcement
2 classes
B terminates aversive state
Therapeutic
e.g. morphine relieves pain
Alcohol relieves anxiety
self-medication
Escape/avoidance of drug withdrawal
Following tolerance/dependence ~
Negative Reinforcement
Different withdrawal syndromes
e.g. depressants vs stimulants
Depends on drugs effects
Tolerance as compensatory responses
Abstention: deficient synaptic activity
Withdrawal
More drug restores system balance
Aversive effects ~
Negative Reinforcement
Role of Nucleus Accumbens?
Rada, Mark & Hoebel (1998)
Medial Hypothalamus
stimulation aversive state
press bar terminate stimulation
Negative reinforcement
dopamine in NA
by 100%
Neg RFT blocked by DA antagonist? ~