Eye movements during natural actions in patients with schizophrenia

Abstract

Background: Visual scanning and planning of actions are reported to be abnormal in patients with schizophrenia. Most studies that monitored eye movements in these patients were performed under free-viewing conditions and used 2- dimensional images. However, images differ from the natural world in several ways, including task demands and the dimensionality of the display. Our study was designed to assess whether abnormalities in visual exploration in patients with schizophrenia generalize to active-viewing tasks in realistic conditions of viewing and to examine whether disturbances in action sequencing in these patients are reflected in their visual scanning patterns while executing natural tasks.

Methods: We monitored visual scan paths in patients with schizophrenia and healthy controls. Participants performed several tasks in which they were asked to look at a realistic scene on a table (free-viewing) and perform 2 active-viewing tasks: a familiar task (sandwich-making) and an unfamiliar task (model-building). The scenes contained both task-relevant and task-irrelevant objects.

Results: We included 15 patients and 15 controls in our analysis. Patients exhibited abnormalities in the free-viewing condition. Their patterns of exploration were similar to those of controls in the familiar task, but they showed scanning differences in the unfamiliar task. Patients were also slower than controls to accomplish both tasks.

Limitations: Patients with schizophrenia were taking antipsychotic medications, so the presence of medication effects cannot be excluded.

Conclusion: People with schizophrenia present a basic psychomotor slowing and seem to establish a less efficient planning strategy in the case of more complex and unfamiliar tasks.

Fig. 1

Examples of the 2 scene layouts used. (A) The “familiar sandwich” scene contained both task-relevant (bread, butter, jelly, knife, plate, glass, water bottle) and irrelevant objects (fork, tool, plug, tape measure, stapler, soda, spice jar). (B) The “unfamiliar construction set” scene contained both task-relevant (model pieces, screws, nuts) and irrelevant objects (2 other pieces from construction set that were not necessary, 2 different kinds of paperclips).

Fig. 2

Mean fixation durations for patients and controls in the sandwich-making task as a function of viewing condition (free v. active viewing). *p < 0.001.

Fig. 3

Gaze durations for patients and controls in the sandwich-making task as a function of viewing condition (free v. active viewing). *p < 0.001. IO = irrelevant objects, RO = relevant objects.

Fig. 4

Gaze durations for patients and controls as a function of the task (familiar/unfamiliar) and on the display model in the unfamiliar task. *p < 0.01, **p < 0.001. IO = irrelevant objects, RO = relevant objects.