Free visual exploration of natural movies in schizophrenia.

Abstract

Eye tracking dysfunction (ETD) observed with standard pursuit stimuli represents a well-established biomarker for schizophrenia. How ETD may manifest during free visual exploration of real-life movies is unclear. Eye movements were recorded (EyeLink®1000) while 26 schizophrenia patients and 25 healthy age-matched controls freely explored nine uncut movies and nine pictures of real-life situations for 20s each. Subsequently, participants were shown still shots of these scenes to decide whether they had explored them as movies or pictures. Participants were additionally assessed on standard eye-tracking tasks. Patients made smaller saccades (movies (p = 0.003), pictures (p = 0.002)) and had a stronger central bias (movies and pictures (p < 0.001)) than controls. In movies, patients' exploration behavior was less driven by image-defined, bottom-up stimulus saliency than controls (p < 0.05). Proportions of pursuit tracking on movies differed between groups depending on the individual movie (group*movie p = 0.011, movie p < 0.001). Eye velocity on standard pursuit stimuli wasreduced in patients (p = 0.029) but did not correlate with pursuit behavior on movies. Additionally, patients obtained lower rates of correctly identified still shots as movies or pictures (p = 0.046). Our results suggest a restricted centrally focused visual exploration behavior in patients not only on pictures, but also on movies of real-life scenes. While ETD observed in the laboratory cannot be directly transferred to natural viewing conditions, these alterations support a model of impairments in motion information processing in patients resulting in a reduced ability to perceive moving objects and less saliency driven exploration behavior presumably contributing to alterations in the perception of the natural environment.