Horace Barlow was best known for his analysis of the way that visual information is encoded as significant nerve signals. He was the first to show (in amphibians) the fundamental organisation of optic nerve fibres, namely that each is connected to a clump of receptors that excite, surrounded by a ring that inhibits. With Richard Fitzhugh and Stephen Kuffler, he analysed how this organization changes in dark adaptation.

Horace’s work on human vision greatly strengthened the modern concept of threshold as signal detection in noisy channels, and he measured the quantum efficiency of seeing in various conditions. With William Levick, he showed that rabbits have optic nerves that signal not position but direction of movement, and by ingenious experiments analysed the neural mechanism by which specific movement is encoded.

Dr Horace Barlow FRS died on 5 July 2020.