Matched filtering and the ecology of vision in insects

Abstract

In the words of Wehner (J Comp Physiol A 161:511–531, 1987) who first coined the term “matched filter” in the context of sensory systems, matched filters “severely limit the amount of information the brain can pick up from the outside world, but they free the brain from the need to perform more intricate computations to extract the information finally needed for fulfilling a particular task”. In other words, by matching the properties of neurons, circuits and sensory structures to the characteristics of the most crucial sensory stimuli that need to be detected, these stimuli can be rapidly and reliably extracted for further processing, thus drastically improving the efficiency of sensing. And by “severely limiting information picked up by the brain”, the energetic costs that would have been associated with coding superfluous information are effectively eliminated. Thus, “freeing the brain” not only frees it from the need to perform intricate computations, it also frees it from significant (and unnecessary) energetic costs. Not surprisingly, with their small eyes and brains and severely limited energy budgets, visual matched filtering is particularly well developed in small animals like insects. It is most obvious at the visual periphery, in the morphology and physiology of the compound eyes, but remarkable matched filters also occur at higher levels of visual processing. Using a number of case studies, I will show how visual matched filters have evolved for all aspects of insect life, including the detection and pursuit of mates and prey and for locomotion and navigation in the natural habitat.