Corticosterone and dehydroepiandrosterone have opposing effects on adult neuroplasticity in the avian song control system
Bibliographic record
Abstract
Chronic elevations in glucocorticoids can decrease the production and survival of new cells in the adult brain. In rat hippocampus, supraphysiological doses of dehydroepiandrosterone (DHEA; a sex steroid precursor synthesized in the gonads, adrenals, and brain) have antiglucocorticoid properties. With male song sparrows (Melospiza melodia), we examined the effects of physiological doses of corticosterone, the primary circulating glucocorticoid in birds, and DHEA on adult neuroplasticity. We treated four groups of nonbreeding sparrows for 28 days with empty (control), corticosterone, DHEA, or corticosterone + DHEA implants. Subjects were injected with BrdU on days 3 and 4. In HVC, a critical song control nucleus, corticosterone and DHEA had independent, additive effects. Corticosterone decreased, whereas DHEA increased, HVC volume, NeuN(+) cell number, and BrdU(+) cell number. Coadministration of DHEA completely reversed the neurodegenerative effects of chronic corticosterone treatment. In an efferent target of HVC, the robust nucleus of the arcopallium (RA), DHEA increased RA volume, but this effect was blocked by coadministration of corticosterone. There were similar antagonistic interactions between corticosterone and DHEA on BrdU(+) cell number in the hippocampus and ventricular zone. This is the first report on the effects of corticosterone treatment on the adult song control circuit, and HVC was the most corticosterone-sensitive song nucleus examined. In HVC, DHEA is neuroprotective and counteracts several pronounced effects of corticosterone. Within brain regions that are particularly vulnerable to corticosterone, such as the songbird HVC and rat hippocampus, DHEA appears to be a potent native antiglucocorticoid.
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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) | 0.001 | 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".