Saliency-guided eye movement during free-viewing in schizophrenic patients

Abstract

Patients with schizophrenia show various kinds of abnormality in eye movements. Recent studies showed that such abnormalities, including the shorter scanpath during free-viewing of natural images, is able to use as an efficient biomarker for schizophrenia. Here we extended our previous work (Miura et.al. 2014 Schizophr Res) and examined whether such difference in eye movements during free-viewing arises from the way in which their attention is drawn to specific features of the visual stimuli. The age-matched subjects (41 patients and 72 healthy controls) viewed 56 natural and/or complex images including faces, scenes and so on. During 8 seconds of viewing time for each image, eye movements were recorded using an eye tracker (EyeLink 1000). We calculated the saliency map of the images for low-level features (luminance, L-M, S-Lum and orientation) based on our previous work (Yoshida et.al. 2012 Curr. Biol.). Then we evaluated the time course of the saliency value at the position of the gaze. The luminance saliency was highest for the first fixation and went down during the 8-sec viewing time in the healthy controls. This is also true for patient group but the luminance saliency was consistently higher in the patients than in the healthy controls (repeated measures ANOVA, F_1,111=5.78, P=0.017). The saliency for other features showed different time course. By combining saliency values for different features (4 models * 8 time points), we constructed a classifier in which patients and controls are distinguished with 83% accuracy. These results suggest that the abnormality in eye movements during visual exploration can be explained, at least partly, by dysregulated saliency in the patients.

Meeting abstract presented at VSS 2015