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Evans, B. D.

Publications and source records attributed to Evans, B. D..

2 recordsLinked to original sources

Biological convolutions improve DNN robustness to noise and generalisation

Deep Convolutional Neural Networks (DNNs) have achieved superhuman accuracy on standard image classification benchmarks. Their success has reignited significant interest in their use as models of the primate visual system, bolstered by claims of their architectural and representational similarities. However, closer scrutiny of these models suggests that they rely on various forms of shortcut learning to achieve their impressive performance, such as using texture rather than shape information. Such superficial solutions to image recognition have been shown to make DNNs brittle in the face of more challenging tests such as noise-perturbed or out-of-domain images, casting doubt on their similarity to their biological counterparts. In the present work, we demonstrate that adding fixed biological filter banks, in particular banks of Gabor filters, helps to constrain the networks to avoid reliance on shortcuts, making them develop more structured internal representations and more tolerant to noise. Importantly, they also gained around 20 35% improved accuracy when generalising to our novel out-of-domain test image sets over standard end-to-end trained architectures. We take these findings to suggest that these properties of the primate visual system should be incorporated into DNNs to make them more able to cope with real-world vision and better capture some of the more impressive aspects of human visual perception such as generalisation.

neuroscience

Vangl2 regulates the dynamics of Wnt cytonemes in vertebrates

The Wnt signalling network regulates cell proliferation and cell differentiation as well as migration and polarity in development of multicellular organisms. However, it is still unclear how distribution of Wnt ligands is precisely controlled to fulfil all of these different functions. Here, we show that the four-pass transmembrane protein Vangl2 occupies a central role in determining the distribution of Wnt by cytonemes in vertebrate tissue. In zebrafish epiblast cells, mouse intestinal telocytes and human gastric cancer cells, activation of Vangl2 leads to the generation of fewer but extremely long cytonemes, which start to branch and deliver Wnt protein to multiple cells. The Vangl2-activated cytonemes increase Wnt/{beta}-catenin signalling in the surrounding cells. Concordantly, inhibition of Vangl2 function leads to the formation of shorter cytonemes and reduced paracrine Wnt/{beta}-catenin signal activation. A mathematical model simulating the observed Vangl2 functions on cytonemes in zebrafish gastrulation predicts an anterior shift of the morphogenetic signalling gradient, altered tissue patterning, and a loss of the sharpness of tissue domains. We confirmed these predictions during anteroposterior patterning in the zebrafish neural plate. In summary, we show that Vangl2 - a core member of the PCP signalling component - is fundamental to paracrine Wnt/{beta}-catenin signalling by controlling cytoneme behaviour in vertebrate development and tissue homeostasis.

developmental biology