Professor of Neuroscience at University of Sussex, Leon Lagnado has made a series of important contributions to our understanding of neural signalling through the study of visual processing in the retina. He developed the first techniques for observing the activity of populations of synapses in the intact brain, using these to reveal how the plasticity of excitatory and inhibitory connections dynamically alters the input-output relation of the retinal circuit. His understanding of how synapses function as machines and then observing how they transmit information has made him a world leader in unravelling the synaptic basis of sensory processing. He has taken the field of “optophysiology” to a new level by pioneering the analysis of circuit function.