4. Differential Impairments in Incentive Learning Caused by First‐ and Second‐ Generation Antipsychotic Drugs
Bibliographic record
Abstract
Schizophrenia is a neuropsychiatric disorder characterized by increased function of dopamine in the brain. Dopamine release is a natural response to reward. It promotes incentive learning (IL), a process by which neutral stimuli acquire the ability to elicit approach and other responses. A recent model characterizes dopamine‐mediated IL as a progressive process with early and late stages accompanied by a shift in neural control from the nucleus accumbens (NAc) to the dorsolateral striatum (DLS). A parallel can be drawn to differences in regionally specific neural responses generated by first‐ and second‐generation antipsychotic drugs (APDs) used to treat schizophrenia. APDs are dopamine receptor antagonists, but first‐generation APDs affect the NAc and DLS while second‐generation APDs affect primarily the NAc. We compared the effects of APDs on IL. Rats (N = 48) were trained to press a lever for food pellets in an operant chamber. Intraperitoneal injections (1 hr before testing) of the first‐generation APD haloperidol (0,0.05,0.10,0.20 mg/kg) or of the second‐generation APD risperidone (0,0.20,0.40,0.80 mg/kg) induced dose‐dependent suppression of lever pressing on days 1‐4, with the highest dose groups failing to demonstrate any evidence of previous learning on day 5 when tested drug‐free. On days 16‐20, haloperidol induced a day‐to‐day suppression not seen with risperidone. The results suggest that the effects of first‐ and second‐generation APDs on learning processes putatively mediated by the NAc and DLS can be differentiated experimentally. The findings imply that APDs may differentially affect IL inpatients with schizophrenia.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".