Putative Sympathetic Oscillator in the Thoracic Spinal Cord of the Bullfrog
Bibliographic record
Abstract
BACKGROUND Cardiorespiratory control is essential for survival of all vertebrates, yet our understanding of the neuronal circuitry involved is rudimentary ‐‐ in part because there is little data beyond mammals to guide us. Neuronal oscillators are discrete neural circuits located within the central nervous system that are capable of generating rhythmic outputs without phasic input. These circuits are found throughout the animal kingdom and are often critical for regulating overt rhythmic behaviours such breathing. Previously, we found three oscillators in the frog brainstem that control ventilation: one for buccal ventilation, two for lung. Three respiratory oscillators have subsequently been found in mammals. Central neuronal oscillators within the sympathetic nervous system of frogs and mammals have also been suspected, but these oscillators have yet to be precisely located. FINDINGS Using extracellular recording and transection techniques in the frog superfused, isolated brainstem and spinal cord preparation, we discovered a robust, yet previously unreported buccal‐like rhythm in the third spinal nerve (SNIII). Unlike the ventilatory rhythms we normally study, the SNIII rhythm demonstrates poor bilateral synchrony. Our data also suggest that this rhythm is: (a) not coupled to ventilatory rhythms recorded in cranial nerves; (b) has distinct responses to pharmacological stimulation compared to ventilatory rhythms; (c) does not require the brainstem; and (d) persists in a chunk of spinal cord centered around SNIII. These data suggest an additional neuronal oscillator in the frog spinal cord located at the level of SNIII. However, removing the brainstem alters the frequency, increases variability and degrades left‐right synchrony of the rhythm, suggesting brainstem connections are important for normal function. SIGNIFICANCE The literature has long debated the existence of central neuronal oscillators that modulate sympathetic nervous system activity in vertebrates. We propose that the bursting activity recorded from the SNIII in frog is the output of such an oscillator, discovery of which could prove critical in shaping our current understanding of the function and evolution of the sympathetic nervous system. Support or Funding Information NSERC and HBI.
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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".