Why drugs keep reinforcing: prediction, tonic vs phasic, and speed
Explains why natural rewards stop producing dopamine once learned but drugs don't, how tonic and phasic dopamine differ, and why faster-acting drugs are more addictive.
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- The reward circuit: reinforcement and dopamine — Builds on the reward circuit and dopamine.
- Absorption and routes of administration — Route of administration sets how fast a drug acts — and so how addictive it is.
- Receptor types: autoreceptors, heteroreceptors and location — Tonic dopamine is regulated through autoreceptors.
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- From use to addiction: receptor loss, hypofrontality, craving and relapse — Repeated over-reinforcement leads to lasting changes in the brain.
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Once behavior has been learned, DA release diminishes upon presentation of natural rewards; it is still released in novel situations, based on predictability of reward. Hacking the system with electrical stimulation or drugs skips this, so behavior keeps getting strongly reinforced → compulsive use. Tonic activity – “background” activity; phasic (burst) activity – bursts and spikes of release. And the quicker the onset of effects, the more addictive the drug will be.
Términos del curso
Las palabras de tu profesor, tal cual aparecen en las diapositivas. Aprende el término y esta definición; la explicación de abajo solo ayuda a entenderla.
- Regulating learning
“Once behavior has been learned, DA release diminishes upon presentation of natural rewards”Diapositivas 06, p. 4
Dopamine shifts to reward cues (Schultz et al., 1997).
- Novelty
“Still released in novel situations; based on predictability of reward”Diapositivas 06, p. 4
Unexpected rewards produce dopamine.
- Tonic activity
““Background” activity due to baseline levels of neurotransmitter release”Diapositivas 06, p. 5
Regulated through regular autoreceptor binding over time.
- Phasic activity
“Bursts and spikes of neurotransmitter release in response to stimulus”Diapositivas 06, p. 5
Necessary for reinforcement and reward learning; reaches lower-affinity receptors.
- Onset and addiction
“General principle of drug addiction – quicker the onset of effects, the more addictive the drug will be”Diapositivas 06, p. 5
e.g., crack vs. cocaine vs. coca; IV heroin vs. oral oxycontin.
De tu curso: Course slides 06, pp. 12–15
Consejo: las teclas ← y → recorren la lección.