Abstract
Bistable percepts are those in which the same physical stimulus causes two spontaneously alternating internal perceptual states. Individuals vary widely in their switch rate within and between different bistable tasks. An abrupt change in the image projected onto the retina, such as when an eye blink or saccade occurs, may contribute to perceptual switches (van Dam & van Ee, 2006). Recently, our lab has shown that patients with psychosis as well as their first-degree relatives demonstrated faster switch rates than healthy controls when viewing an ambiguous structure-from-motion stimuli (the rotating cylinder illusion). Work investigating saccades in patients with psychosis, using anti-saccade tasks, has also demonstrated a decrease in their ability to prevent involuntary saccades. These abnormalities in visual functioning may be consistent with theorized disruptions in excitatory / inhibitory balance in psychosis. We examined whether increases in switch rate when viewing the rotating cylinder may be related to increased saccade or blink rates in patients. Specifically, we examined eye tracking data recorded while participants viewed the rotating cylinder. Data were acquired from three groups: patients with psychosis (e.g., schizophrenia, bipolar disorder), their first-degree biological relatives, and healthy controls. We saw no significant differences in fixation quality across groups, as measured by average Euclidean distance or variation from fixation. We found that there was an increased probability of blinks across all groups ~1s prior to reported switches, compared to baseline blink rate, followed immediately by a ~500ms decrease in blink and saccade probability. However, we did not see a significant difference in the number of blinks between the three groups. These results suggest that blinks and eye movements contribute to perceptual switches in a similar way across groups, such that differences in switch rates observed between patients and controls may not result from differences in eye movement or blink related processes.