Bibliographic record
Abstract
The anhedonia hypothesis of drug addiction posits that drugs of abuse target the same neural systems as natural rewards such as food and sex. The most likely candidate brain region is the mesolimbic dopamine system. In animals, dopamine is released in the ventral striatum, or nucleus accumbens, in response to food, sexual mates, and to almost all drugs of abuse. There are several predictions one can make from the anhedonia hypothesis: (1) dopamine release in response to reinforcers will correlate with the degree of pleasure experienced; (2) natural reinforcers and drugs of abuse will release dopamine in the same brain areas; (3) aversive stimuli will not release dopamine. These predictions can be tested with PET experiments in human subjects. The method we use consists in comparing the binding potential of the D2 ligand [11C]raclopride in baseline and activation conditions. Studies in humans: Oral amphetamine and alcohol caused dopamine release in the ventral striatum in humans. The effect was greater in individuals with the novelty-seeking personality, a risk factor for addiction. The effect did not correlate with pleasure. However, while alcohol and amphetamine caused dopamine release in the ventral striatum, two natural rewards (money and food) targeted the main body and dorsal portion of the striatum. Thus there may be a dissociation between natural and drug rewards with respect to dopamine transmission. Another possibility is that conditioned rewarding stimuli target different brain regions than novel ones. We provided evidence for this second explanation by measuring dopamine release in response to smoking cigarettes in habitual smokers. Cigarette smoking caused dopamine release in the dorsal striatum. Finally, human and animal data suggest that hyper-responsiveness of the dopamine system may be a risk factor for addiction. How does dopamine hyper-responsiveness develop? We investigated this issue using two paradigms. We showed that poor parental bonding early in life was associated with a greater dopamine response to mental stress in adulthood. We also demonstrated sensitization in human subjects: we showed that repeated doses of oral amphetamine caused an enhanced response to subsequent amphetamine. This effect persisted after one year (See Figure 1).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".