Visual Scanning Abnormalities as Biomarker for Schizophrenia

Abstract

Visual scan paths are a pattern of foveal fixations and voluntary saccades produced when an individual views an image. These scan paths have repeatedly been shown to be abnormal in patients with schizophrenia. Most clinical scan path studies have focused on the investigation of eye movements to images of social scenes, or most commonly, of faces. While healthy participants scan face images extensively, particularly the eyes and mouth, patients with schizophrenia demonstrate restricted scanning of these images. In other words, patients with schizophrenia exhibit fewer fixations, longer fixation duration, longer saccade duration and peak velocity, and smaller saccade amplitude compared with healthy controls. However, recent evidence has shown that this abnormality is not specific to faces but can be observed to other image types. In addition, it has been shown that the spatial distribution of fixation locations is different in patients with schizophrenia compared to healthy controls and that this abnormal scanning behaviour extends to patients with bipolar disorder. A small study on healthy twins has provided preliminary evidence that the distribution of fixations may be genetically determined and may serve as a biomarker for schizophrenia and bipolar disorder.