reinforcement & drug effects lesson 15. operant conditioning n acquisition & maintenance of...
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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 drug-taking behavior ~
Operant Conditioning
SD B SR:
Classical vs. Operant Conditioning
SR biologically important stimulus
B Response SR
SD
Discriminative stimulus Signals SR available Response required to obtain SR ~
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 ~
Similar to classical conditioning acquisition: B SR
extinction: B No SR
Other Phenomena
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 ~
Drugpump
Drug Self-administration
operant conditioning
Press bar drug infusion ~
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 B appetitive SR
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 ~
MFB
Ventral Tegmental Area
VTA
Mesolimbic Pathway
NA
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 N34 (Ach-R) Modulates mesolimbic pathway
18-MC (18-Methoxycoronaridine) Ibogaine derivative N34 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? ~
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