.This is a photo of the current 1-D oculomotor system. The dark wooden board on which the individual components of the system are sitting is 17 inches wide. There are 3 main components of the system shown: the photoreceptor chip which triggers saccades to visual targets, the saccadic burst generator chip which drives the motors, and the auditory localization system which triggers saccades to auditory targets.
The photoreceptor chip which detects local changes in image intensity (upper left) is sitting on a rotatable platform, driven by two motors. The motors are driven by a controller chip (center) which mimics neural circuitry found in the brainstem of primates to center the photoreceptor chip on the location of the target. In addition, the system orients to auditory targets, using the two microphones (bottom left) to locate sound source azimuth. This system models a computational architecture found in the barn owl (far right) also provides target information to the motor control chip.
Here is a close-up color photo of the photoreceptor chip. In the background, the motor shafts of the antagonistic pair of motors can be seen. A fine thread wrapped around each shaft is used to drive the turntable. The photoreceptor chip is standing vertically and is covered by a lens. The silicon chip behind the lens is approximately 2mm square.
All of these circuits require the specification of many parameters which, until now, have been chosen by hand. The ability of animals to quickly adapt to changes in eyeball dynamics and system geometry from both growth and damage has been well documented, however, the mechanisms and rules for this change are still being debated. We are developing techniques for using biologically realistic error signals (e.g. vision-based accuracy measures and visual motion) in our system for studying this automatic parameter setting problem.
(Postscript: 1.4Meg)
