An evolutionary perspective on chordate brain organization and function: insights from amphioxus, and the problem of sentience
Bibliographic record
Abstract
The similarities between amphioxus and vertebrate brains, in their regional subdivision, cell types and circuitry, make the former a useful benchmark for understanding the evolutionary innovations that shaped the latter. Locomotory control systems were already well developed in basal chordates, with the ventral neuropile of the dien-mesencephalon serving to set levels of activity and initiate locomotory actions. A chief deficit in amphioxus is the absence of complex vertebrate-type sense organs. Hence, much of vertebrate story is one of progressive improvement both to these and to sensory experience more broadly. This has two aspects: (i) anatomical and neurocircuitry innovations in the organs of special sense and the brain centres that process and store their output, and (ii) the emergence of primary consciousness, i.e. sentience. With respect to the latter, a bottom up, evolutionary perspective has a different focus from a top down human-centric one. At issue: the obstacles to the emergence of sentience in the first instance, the sequence of addition of new contents to evolving consciousness, and the homology relationship between them. A further question, and a subject for future investigation, is how subjective experience is optimized for each sensory modality. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.
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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 | 0.001 |
| 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 | 0.006 |
| Scholarly communication | 0.001 | 0.003 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".