Connectome Wiring Shapes Neural Geometry in Fruit Fly Visual System
Researchers have shown that biologically accurate connectome wiring in the Drosophila visual system produces a distinctive, smooth circular representational geometry that randomly wired networks cannot replicate. The study used representational similarity analysis (RSA) and centered kernel alignment (CKA) on the FlyWire connectome-constrained Flyvis network ensemble, comparing it against stability-matched random baselines. The findings propose representational geometry as a practical fidelity metric for evaluating whether neural network models are biologically faithful, without requiring behavioral decoders or single-unit recordings.
A new preprint study on bioRxiv demonstrates that the specific wiring of the Drosophila melanogaster connectome shapes population-level neural geometry in ways that arbitrary wiring cannot reproduce. Using the Flyvis pretrained visual system ensemble — 50 networks constrained to the FlyWire connectome architecture — and comparing them against 50 stability-preserving randomly shuffled baselines, the authors found that connectome-constrained networks produced significantly higher RSA Spearman correlations (r = 0.686 for ON edge stimuli; r = 0.846 for ON+OFF edge stimuli) compared to random networks, with CKA corroborating these results. The connectome-constrained geometry also closely matched biological T4/T5 direction-tuning recordings from living flies (r = 0.930 vs. r = 0.603 for random networks, Δr = 0.327, p < 0.0001). The study further found that within each stimulus polarity, the ON pathway showed stronger geometric separation than the OFF pathway (Δr = 0.138), consistent with known asymmetries in T4/T5 direction selectivity. The authors argue this framework addresses a key gap highlighted by prior work — that behavioral fidelity alone cannot confirm biological fidelity in neural models — and suggest representational geometry as a scalable, decoder-free metric applicable as connectome-scale emulations advance toward mammalian cortex.
What's missing
The study is a preprint and has not yet undergone peer review. Key limitations include that the random baselines, while stability-constrained, may not exhaust all biologically plausible alternative wirings. It is also unclear whether representational geometry alone can distinguish connectome fidelity from other structural constraints (e.g., cell-type composition) that were not independently varied.
What different sources said
- bioRxivCenter
Connectome wiring shapes population-level neural geometry in the Drosophila visual system
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