Electrical stimulation of retinal neurons is known to elicit visual sensations. When applied to the retina in a spatial pattern, electrical stimulation may be capable of providing rudimentary patterned vision that may be of benefit to sufferers of degenerative retinal disorders. No such device has yet been devised to provide for chronic study of the psychophysical perceptions elicited from a prosthesis for retinal stimulation. In this study, steps towards achieving this goal have been successfully carried out. Foregoing research was reviewed such that appropriate stimulation parameters were incorporated in the design of a 100 stimulation channel, complimentary metal oxide semiconductor (CMOS) integrated circuit, small enough in size so as to be capable of being implanted within the ocular anatomy or surrounding orbit. The device, and its associated external hardware and software were designed, modeled, fabricated, and interfaced with stimulating electrodes in acute testing in a highorder mammal (Ovis aries) so as to assess the capabilities of the device to elicit cortical potentials as a direct result of stimulation of the neural retina. Testing was performed under conditions similar to those anticipated in chronic in-situ configurations wherein radio-frequency telemetry was used to deliver power and configuration parameters to the device thus avoiding the passage of wires through tissue in order to communicate to the implant circuit. The results of the testing indicate that the circuit is indeed capable of eliciting physiological responses in the animal and evidence is present that these responses could be elicited in patterned form. Further work undertaken includes the development of surgical methods for implantation, and application of the prosthesis circuit in functional electronic stimulation.

Electrical stimulation of retinal neurons is known to elicit visual sensations. When applied to the retina in a spatial pattern, electrical stimulation may be capable of providing rudimentary patterned vision that may be of benefit to sufferers of degenerative retinal disorders. No such device has yet been devised to provide for chronic study of the psychophysical perceptions elicited from a prosthesis for retinal stimulation. In this study, steps towards achieving this goal have been successfully carried out. Foregoing research was reviewed such that appropriate stimulation parameters were incorporated in the design of a 100 stimulation channel, complimentary metal oxide semiconductor (CMOS) integrated circuit, small enough in size so as to be capable of being implanted within the ocular anatomy or surrounding orbit. The device, and its associated external hardware and software were designed, modeled, fabricated, and interfaced with stimulating electrodes in acute testing in a highorder mammal (Ovis aries) so as to assess the capabilities of the device to elicit cortical potentials as a direct result of stimulation of the neural retina. Testing was performed under conditions similar to those anticipated in chronic in-situ configurations wherein radio-frequency telemetry was used to deliver power and configuration parameters to the device thus avoiding the passage of wires through tissue in order to communicate to the implant circuit. The results of the testing indicate that the circuit is indeed capable of eliciting physiological responses in the animal and evidence is present that these responses could be elicited in patterned form. Further work undertaken includes the development of surgical methods for implantation, and application of the prosthesis circuit in functional electronic stimulation.

William Eric Leifur Grimson. / Based on the author's thesis (Ph.D.--Massachusetts Institute of Technology) Includes indexes. / Bibliography: p. [247]-267.

In this study human color constancy was tested for two-dimensional (2D) and three-dimensional (3D) setups with real objects and lights. Four different illuminant changes, a natural selection task and a wide choice of target colors were used. We found that color constancy was better when the target color was learned as a 3D object in a cue-rich 3D scene than in a 2D setup. This improvement was independent of the target color and the illuminant change. We were not able to find any evidence that frequently experienced illuminant changes are better compensated for than unusual ones. Normalizing individual color constancy hit rates by the corresponding color memory hit rates yields a color constancy index, which is indicative of observers' true ability to compensate for illuminant changes.