Oscillating wildly: Turning the evolution of respiratory rhythm generation on its head
Bibliographic record
Abstract
How the neuronal control of air breathing evolved is unknown. Brainstem circuits controlling breathing have only been investigated in a small handful of extant vertebrates. This makes an evolutionary analysis challenging. In the frog, we have found evidence for three areas involved in respiratory rhythm generation, each with distinct pharmacologies: the buccal area in rhombomere 7 as well as both lung burst priming and lung burst power stroke regions situated in rhombomeres 4‐5. We have long assumed that circuits generating air breathing in mammals and frogs are homologous, evolving from a common ancestry. However, there are some inconsistencies with this assumption. The primary inspiratory oscillator in mammals, the PreBötzinger Complex (PreBötC), is located in rhombomere 7‐‐the same rhombomere as the frog buccal area‐‐and the rhythms produced by buccal and PreBötC are stubbornly independent of CO2. In comparison, like pre‐inspiratory/expiratory activity in mammals, the lung bursts in the frog are highly CO2 sensitive, and both originate in rhombomere 4‐5. These data suggest that we may have to turn our previous hypothesis that the frog lung area and PreBötC are homologous on its head and consider the possibility that the mammalian PreBötC evolved from a fish oscillator used for water‐breathing. Until more studies on non‐mammalian vertebrates are performed any hypothesis on the evolution of air breathing is but a work in progress, and with so little data currently available, further oscillations are likely. This work was funded by NSERC.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 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".