Connectome Wiring Shapes Neural Geometry in Fruit Fly Visual System
Researchers used representational geometry to show that biologically accurate connectome wiring in the Drosophila visual system produces distinct population-level neural patterns that random wiring cannot replicate. The study applied representational similarity analysis (RSA) and centered kernel alignment (CKA) to a Drosophila connectome-constrained neural network ensemble, finding strong alignment with recorded biological direction-tuning data. The findings propose a practical fidelity metric for evaluating connectome-scale brain emulations that requires neither behavioral decoders nor single-unit recordings.
A new preprint posted to bioRxiv argues that representational geometry — the structure of pairwise distances between population neural responses to different stimuli — can serve as a biologically meaningful fidelity metric for connectome-constrained neural network models. The researchers applied RSA and CKA to the Flyvis ensemble, 50 networks whose architecture mirrors the FlyWire connectome of Drosophila melanogaster, comparing them against 50 stability-constrained random baseline networks with shuffled weights. Connectome-constrained networks produced a smooth circular direction geometry that random networks failed to replicate, with RSA Spearman correlations of r = 0.686 for ON edge stimuli and r = 0.846 for ON+OFF edge stimuli, both statistically significant. The connectome-constrained geometry also matched electrophysiological recordings of T4/T5 direction-selective neurons in living flies substantially better than random networks (r = 0.930 vs. r = 0.603, gap Δr = 0.327). The study also found that within each stimulus polarity, the ON pathway showed stronger geometric separation than the OFF pathway, consistent with known asymmetries in T4/T5 direction selectivity. The authors frame this as a step toward verifiable fidelity metrics for large-scale brain emulations as connectome mapping scales toward mammalian cortex.
What's missing
The study is a preprint and has not yet undergone peer review. The authors acknowledge that the framework has been demonstrated only in the Drosophila visual system; whether representational geometry generalizes as a fidelity metric to more complex organisms or other brain regions remains untested. It is also unclear how sensitive the metric is to the specific choice of stimulus set, and whether stability-constrained random baselines fully capture the space of plausible alternative wiring schemes.
What different sources said
- bioRxivCenter
Connectome wiring shapes population-level neural geometry in the Drosophila visual system
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