Synaptic circuits of the <i>Drosophila</i> optic lobe: The input terminals to the medulla
Bibliographic record
Abstract
Understanding the visual pathways of the fly's compound eye has been blocked for decades at the second optic neuropil, the medulla, a two-part relay comprising 10 strata (M1-M10), and the largest neuropil in the fly's brain. Based on the modularity of its composition, and two previous reports, on Golgi-impregnated cell types (Fischbach and Dittrich, Cell Tissue Res.,1989; 258:441-475) and their synaptic circuits in the first neuropil, the lamina, we used serial-section electron microscopy to examine inputs to the distal strata M1-M6. We report the morphology of the reconstructed medulla terminals of five lamina cells, L1-L5, two photoreceptors, R7 and R8, and three neurons, medulla cell T1 and centrifugal cells C2 and C3. The morphology of these conforms closely to previous reports from Golgi impregnation. This fidelity provides assurance that our reconstructions are complete and accurate. Synapses of these terminals broadly localize to the terminal and provide contacts to unidentified targets, mostly medulla cells, as well as sites of connection between the terminals themselves. These reveal that R8 forms contacts upon R7 and thus between these two spectral inputs; that L3 provides input upon both pathways, adding an achromatic input; that the terminal of L5 reciprocally connects to that of L1, thus being synaptic in the medulla despite lacking synapses in the lamina; that the motion-sensing input cells L1 and L2 lack direct interconnection but both receive input from C2 and C3, resembling lamina connections of these cells; and that, as in the lamina, T1 provides no output chemical synapses.
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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".