Diurnal rhythms in neural activation in the mesolimbic reward system: critical role of the medial prefrontal cortex
Bibliographic record
Abstract
Previous evidence suggests a circadian modulation of drug-seeking behavior and responsiveness to drugs of abuse. To identify potential mechanisms for rhythmicity in reward, a marker of neural activation (cFos) was examined across the day in the mesolimbic reward system. Rats were perfused at six times during the day [zeitgeber times (ZTs): 2, 6, 10, 14, 18, and 22], and brains were analysed for cFos and tyrosine hydroxylase (TH)-immunoreactive (IR) cells. Rhythmic expression of cFos was observed in the nucleus accumbens (NAc) core and shell, in the medial prefrontal cortex (mPFC), and in TH-IR and non-TH-IR cells in the ventral tegmental area (VTA), with peak expression during the late night and nadirs during the late day. No significant rhythmicity was observed in the basolateral amgydala or the dentate gyrus. As the mPFC provides excitatory input to both the NAc and VTA, this region was hypothesised to be a key mediator of rhythmic neural activation in the mesolimbic system. Hence, the effects of excitotoxic mPFC lesions on diurnal rhythms in cFos immunoreactivity at previously observed peak (ZT18) and nadir (ZT10) times were examined in the NAc and VTA. mPFC lesions encompassing the prelimbic and infralimbic subregions attenuated peak cFos immunoreactivity in the NAc, eliminating the diurnal rhythm, but had no effect on VTA rhythms. These results suggest that rhythmic neural activation in the mesolimbic system may contribute to diurnal rhythms in reward-related behaviors, and indicate that the mPFC plays a critical role in mediating rhythmic neural activation in the NAc.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".