Investigating Visual Illusory Perception In Schizophrenia Patients Using The Pinna Stimulus

Objectives:Schizophrenia patients is considered to have disorders of sensation and perception,and vision is an important part of sensation.This study was designed to investigate the difference of psychophysical properties of Pinna illusion and eye movements between healthy controls and patients with schizophrenia using the Pinna stimulusMethods:A case-control study was utilized in this research.98 patients with schizophrenia(SCZ)and 90 relatively well matched healthy-control(HC)were included in our study.Task performance of Pinna stimulus was gathered in SCZ and HC.We compared the bias and variance between two groups,and explore the relationship between psychophysics metrics and clinical symptoms Subjects’eye position was continuously monitored throughout the experiments using a table-mounted infrared eye tracker system.We compared the eye movement measures between two groups,and explore the relationship between eye movement measures and psychophysics metrics of Pinna illusionResults:1.psychophysics metrics of Pinna illusiona))Perceived illusory speed for each condition.Group had a significant effect on perceived illusory speed(p=0.006384);it is about 0.7±0.28 degrees per second lower in patients.Group had a significant effect on response variability(p=0.000015);approximately 1.01±0.24 higher in patientsb)Slower perceived speed and higher response variability in non-fixated trials for both patients and healthy controls(p’s<0.05).When only fixated trials are considered,there are no significant differences in perceived speed or response variability between patients and controlsc)There is a significant main effect of general symptoms and positive symptoms on perceived speed(p’s<0.05).And there is a significant main effect of excitatory symptoms on response variability(p<0.05)2.eye movements:a)In the single point fixation task,the trend of less fixation count,shorter fixation duration,more saccade count and longer mean distance to center were observed in SCZ(p’s<0.05);In stimulus present fixation task,the trend of less fixation count and more saccade count were observed in SCZ(p’s<0.05)b)No significant effect of eye movement metrics on psychophysics metricsConclusions:Patients with schizophrenia show lower perceived illusory speed and higher response variability,which indicate their resistance to Pinna illusion Weakened gain control(especially around suppression)and weakened integration may be the psychological mechanism of schizophrenia Pinna illusion defect.There is a trend of lower rate of fixations and higher rate of saccades in schizophrenia.