Evolution leads to a diversity of motion-detection neuronal circuits

TL;DR

This study uses digital evolution to explore how diverse neural circuits for motion detection can arise, revealing that evolution produces many different architectures with varying complexity and redundancy, influenced by robustness and adaptation.

Contribution

It demonstrates that evolution generates a vast diversity of motion detection circuits and links circuit complexity to robustness and adaptive processes.

Findings

Evolution produces diverse neural architectures for the same function.

Evolved circuits show variation in redundancy and complexity.

Selection for robustness influences circuit complexity.

Abstract

A central goal of evolutionary biology is to explain the origins and distribution of diversity across life. Beyond species or genetic diversity, we also observe diversity in the circuits (genetic or otherwise) underlying complex functional traits. However, while the theory behind the origins and maintenance of genetic and species diversity has been studied for decades, theory concerning the origin of diverse functional circuits is still in its infancy. It is not known how many different circuit structures can implement any given function, which evolutionary factors lead to different circuits, and whether the evolution of a particular circuit was due to adaptive or non-adaptive processes. Here, we use digital experimental evolution to study the diversity of neural circuits that encode motion detection in digital (artificial) brains. We find that evolution leads to an enormous diversity of potential neural architectures encoding motion detection circuits, even for circuits encoding the exact same function. Evolved circuits vary in both redundancy and complexity (as previously found in genetic circuits) suggesting that similar evolutionary principles underlie circuit formation using any substrate. We also show that a simple (designed) motion detection circuit that is optimally-adapted gains in complexity when evolved further, and that selection for mutational robustness led this gain in complexity.