9309539 Barlow The compound eye of the horseshoe crab, Limulus, has been a model system in visual research for decades. The visual sensitivity of the eyes of this animal undergo a million-fold change between daytime and nighttime, controlled partly by an internal "circadian clock" that enables the animal to see underwater in dim moonlight as well as in bright sunlight. This project involves a unique approach with novel techniques in behavior and in neurophysiology. The objectives are to investigate the visual behavior during day and night, the activity patterns in the optic nerve in behaving animals, and the neural coding that underlies "approach" behavior to certain kinds of targets. Behavioral techniques provide precise measurements of what the animal can see and how well it can see under different lighting levels. Physiological techniques allow recordings of optic nerve activity from behaving animals by both tether and by sonar telemetry. Studies are done on behavior and physiology in the controlled environment of the laboratory and in the animal's natural habitat of the ocean, and data will be incorporated into related studies on computational models of visual processing. Results will reveal concepts of how neural activity is related to behavior, and will have impact not only on studies of vision, but across many areas of neuroscience, with potential further implications for artificial vision for robotics development as well as for possible aids for low vision. ***
