Running wild: Neurogenesis in the hippocampus across the lifespan in wild and laboratory‐bred Norway rats
Bibliographic record
Abstract
The dogmatic view that new neurons are not produced in the adult mammalian brain has been overturned in light of mounting evidence that neurogenesis continues to occur within two neurogenic niches, the subventricular zone and the hippocampus. In mammals, new neurons are incorporated into the hippocampus throughout life and are influenced by environmental and genetic factors. Most studies use captive-bred animals, and no previous studies have examined neurogenesis in free-living rats despite the common use of laboratory rats. In particular, exercise upregulates neurogenesis in the hippocampus and exercise levels would certainly differ between wild and captive populations. Therefore, it is unclear whether results from captive populations can be generalized to natural populations or reflect variations from an artificial and inappropriate "baseline" level. To address this, we compared levels of cell proliferation and the number of immature neurons (using the endogenous markers Ki67 and doublecortin, respectively) in captured wild juvenile and adult Norway rats to three captive strains (Sprague-Dawley, Long-Evans, and Brown Norway) of the same species. Here, we show that the level of cell proliferation and young immature neuron survival in the dentate gyrus of juvenile wild rats is significantly higher than in Sprague-Dawley rats, but not Long-Evans or Brown Norway rats. However, cell proliferation and the number of immature neurons in the hippocampus of adult wild rats are within the normal range of captive-bred rats at all adult ages examined. This finding is surprising given the dissimilar environments, including stressors and opportunities for exercise, encountered by each population.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| 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".