Strain-Specific Differences in Cerebellar Anatomy between Laboratory and Wild Rats
Bibliographic record
Abstract
INTRODUCTION: Domestication and subsequent breed selection has significantly changed the phenotype of most domesticated animal species. Not only has their external appearance changed, in many species, the brain and individual brain regions often differ in size in domesticated strains compared with their wild ancestors. Although the majority of studies on mammals focus on cortical regions, the cerebellum often differs in relative and absolute size between domestic and wild strains, but more specific data on cell sizes and numbers are often lacking. METHODS: We quantified cerebellar anatomy in two domesticated strains (Long-Evans and Sprague-Dawley) and one wild type of brown rat (Rattus norvegicus). Using unbiased stereology, we measured the total cerebellum and its layers' volumes, as well as the number and size of Purkinje cells. RESULTS: Long-Evans rats had a larger total cerebellum volume, in both absolute and relative terms, than Sprague-Dawley and wild rats, but no other significant differences were detected. Significant differences in the absolute and relative sizes of the molecular, granule cell, and white matter layers were also found, but the differences were inconsistent among strains such that the largest values alternated between the two laboratory strains. The absolute number of Purkinje cells did not differ among strains, but one population of Sprague-Dawley rats and the wild rats had more Purkinje cells relative to cerebellar volume. Last, Long-Evans rats had significantly smaller Purkinje cells than the other strains in both absolute and relative terms. CONCLUSION: Only one of the two domesticated strains differed from wild rats in cerebellar anatomy. Our results therefore demonstrate that changes in the brains of domesticated animals do not necessarily follow a universal rule; they can vary between different strains. This highlights the importance of including more than one strain in wild-domesticate comparisons in brain anatomy and avoiding the oversimplification of the effects of domestication on the brain.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".