Research Outline Our group is interested in discovering design principles that govern the structure and function of neurons and neural circuits. We record from well-defined neurons, mainly in flies’ visual systems, to measure the molecular and cellular factors that determine relevant measures of performance, such as representational capacity, dynamic range and accuracy. We combine this empirical approach with modelling to see how the basic elements of neural systems (ion channels, second messengers systems, membranes, synapses, neurons, circuits and codes) combine to determine performance. We are investigating four general problems. How are circuits designed to integrate information efficiently? How do sensory adaptation and synaptic plasticity contribute to efficiency? How do the sizes of neurons and networks relate to energy consumption and representational capacity? To what extent have energy costs shaped neurons, sense organs and brain regions during evolution? The Evolution of Neural Circuits We are interested both in the underlying causes and consequences of changes in both the physiology and anatomy of neural circuits. Almost nothing is known about the types of changes that have occurred during evolution in neural circuits. Even less is know about how changes in neural circuits affect the behaviours these circuits generate. To assess the diversity of neural circuits our studies concentrate on two circuits in which it is possible to relate the activity of neurons to specific behaviours - the photoreceptors of insects (and in particular flies) and the neural circuits that control the movements of the legs in grasshoppers, crickets and bush crickets. By assessing changes in both the anatomy and physiology of species and relating them to behavioural differences and the known evolutionary relationships between these species we can begin to understand the patterns of change. Sensor Fusion How do neural circuits combine parallel datastreams from different types of sensor to produce a compound signal that is suitable for motor control? This question is particularly pertinent in systems where extreme speed and accuracy are critical. One such model system is the reflexive flight control system of the fly, where necessary reaction times approach timescales comparable to the refractory period of a spiking neuron. The fly combines inputs from two visual systems, the ocelli and the compound eyes, to stabilise its head in flight. Working with Holger Krapp, we have discovered that an exceptionally well characterised set of visually driven neurons, the large tangential neurons of the fly lobula plate, are driven by both sensory systems. We are exploiting this opportunity to analyse sensor fusion in circuits that are specialised for sensorimotor coordinate transformation using behavioural, electrophysiological and computational methods.