A test of the opponent‐process theory of motivation using lesions that selectively block morphine reward
Bibliographic record
Abstract
The opponent-process theory of motivation postulates that motivational stimuli activate a rewarding process that is followed by an opposed aversive process in a homeostatic control mechanism. Thus, an acute injection of morphine in nondependent animals should evoke an acute rewarding response, followed by a later aversive response. Indeed, the tegmental pedunculopontine nucleus (TPP) mediates the rewarding effects of opiates in previously morphine-naive animals, but not other unconditioned effects of opiates, or learning ability. The aversive opponent process for acute morphine reward was revealed using a place-conditioning paradigm. The conditioned place aversion induced by 16-h spontaneous morphine withdrawal from an acute morphine injection in nondependent rats was abolished by TPP lesions performed prior to drug experience. However, TPP-lesioned rats did show conditioned aversions for an environment paired with the acute administration of the opioid antagonist naloxone, which blocks endogenous opioids. The results show that blocking the rewarding effects of morphine with TPP lesions also blocked the opponent aversive effects of acute morphine withdrawal in nondependent animals. Thus, this spontaneous withdrawal aversion (the opponent process) is induced by the acute rewarding effects of morphine and not by other unconditioned effects of morphine, the pharmacological effects of morphine or endogenous opioids being displaced from opiate receptors.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.002 |
| 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".