SEMINAR ANNOUNCEMENT

Wednesday, 25 January 2001, at 10:10 a.m.
in S112  Engineering South Building
Research Seminar

Adaptive Properties of Circuits for Visual Motion Detection in the Insect Brain

Prof. David O'Carroll
Adelaide University

Abstract:  Adaptation to changing stimuli is an obvious feature of the transduction stage (the receptor level) of a wide variety of animal sensory systems. Our recent research has revealed sophisticated adaptive behavior in neural circuits beneath the receptor layer of the insect visual system. We concentrate on neurons that process and analyze the pattern of optical flow generated by the movement of flying insects (hoverflies) through their habitat. These 'motion detectors' are part of an elaborate visual guidance mechanism that supports spectacular aerial pursuit behavior in some flies. On an evolutionary time-scale (millions of years) these motion detectors have developed complex spatiotemporal filters that match the tuning of the neurons to the speeds of motion experienced during normal behavior1. On a more dynamic time-scale (tens of milliseconds), these same motion detectors display enormous changes in sensitivity to image contrast, depending on recent stimulus history2.  This dynamic contrast adaptation may improve the robustness of velocity estimates derived from the output of the motion detector, which may, in turn, be critical for behaviors such as navigation over large distances,
collision avoidance and target interception.

Biography:  I completed my Ph.D., on the optics of spider eyes, in 1989 at Flinders University, having also worked at RSBS (A.N.U.) and the University of Sussex in the U.K. After that I worked for 4 years (until 1993) on object detecting neurons in dragonflies, as a postdoctoral fellow with Prof. Adrian Horridge and Dr M.V.Srinivasan at RSBS. I then worked as Research Fellow with Simon Laughlin, in the Zoology Department at the University of Cambridge until 1998, when I moved to my present position as Assistant Professor at the University of Washington, Seattle. My work over the last 5 years or so has focused on visual ecology in nocturnal and diurnal insects, in signal processing and motion detection by the insect visual system and on the analysis of polarized light by spiders.

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