Induced Simultanagnosia in Saccadic Persistence of Vision Display
Rolf Nelson, Augustus Kram Mendelsohn* ‘20, Michael F. Vallerie* ‘21, and Elizabeth Shelto* ‘23
*Department of Psychology and Neuroscience, Wheaton College, Norton, MA
Our fall semester was spent creating and experimenting with a saccadic persistence of vision display. A saccade is a rapid movement of the eyes between two points. People usually experience a brief moment of blindness when this occurs that is never recognized. Our research delved into this issue to determine how the saccade truly works. The vision display we created was composed of a thin strip of 32 LED lights that blink incredibly quick. Staring directly at the vision display, the viewer would see only a lit strip of lights. However, when a saccade is performed across an LED strip, an image will become apparent. The method used to create images using a LED strip is called painting the retina. The LED lights have to be flashing at such a high rate that the image is actually painted on the retina as the eyes move side to side.
The initial goal of this project was to explore whether participants would see multiple fragmented figures or one solid image during the time it takes to make a saccade. The perception of only one image would be considered a kind of induced simultanagnosia. Simultanagnosia is a neurological condition in which an individual is only able to see one image at a time, even if they are presented with multiple. We investigated this phenomenon by asking participants to make a saccade over the light strip, then draw what they saw. Each participant repeated this for a number of different stimuli, with insurance that the shape, size, and order of each stimuli varied. After analyzing the images drawn by those partaking in our study, we found that participants generally saw one solid image, not several. This means that even though they were presented with multiple images as the LED strip painted their retinas they only perceived and reproduced one final image.
The lab originally set out to create a small device that could paint retinas during a saccade and to study the ability of subjects to perceive images presented to them in this fashion. We succeeded in both producing a mobile LED strip that could paint retinas and achieved an experiment testing our initial hypothesis about inducing simultagnosia. Our method of retinal painting with a persistence of vision display allowed us to induce simultanagnosia within the participants almost all the time. We presented participants with stimuli that were created by flashing an LED strip quickly enough to paint their retina but they only perceived one image instead of the multiple images they actually saw. Research involving saccades and persistence of vision displays is just starting to surface. Hopefully this will lead to new insights into how humans perceive their surroundings and create their own personal reality.