Céline Delerue

Patients with schizophrenia are biased toward low spatial frequency to decode facial expression at a glance.

Whereas patients with schizophrenia exhibit early visual processing impairments, their capacity at integrating visual information at various spatial scales, from low to high spatial frequencies, remains untested. This question is particularly acute given that, in ecological conditions of viewing, spatial frequency bands are naturally integrated to form a coherent percept. Here, 19 patients with schizophrenia and 16 healthy controls performed a rapid emotion recognition task with hybrid faces. Because these stimuli displayed in a single image two different facial expressions, in low (LSF) and high (HSF) spatial frequencies, the selected emotion probes which spatial scale is preferentially perceived. In a control experiment participants performed the same task with either low or high spatial frequency filtered faces. Results show that patients have a strong bias towards LSF with hybrid faces compared to healthy controls. However, both patients and healthy controls performed better with HSF filtered faces than with LSF filtered faces in the control experiment, demonstrating that the bias found with hybrid stimuli in patients was not due to an inability to process HSF. Whereas previous works found a LSF contrast deficit in schizophrenia, our results suggest a deficit in the normal time course of concurrently perceiving LSF and HSF. This early visual processing impairment is likely to contribute to the difficulties of patients with schizophrenia with facial processing and therefore social interaction.

The relationship between visual object exploration and action processing in schizophrenia

Introduction. Abnormalities in visual exploration and action processing are widely reported in schizophrenia. The aim of this study was to investigate whether object exploration (in order to recognise an action or the object) modulates visuomotor behaviour differently in schizophrenic patients and controls. Methods. Visual scan paths were monitored in 36 patients and 36 controls. Participants performed three tasks, in which they were asked to either (1) name the object (the object-naming task), (2) picture themselves interacting with the object and then name the action (the action-naming task), or (3) explore the object (the free-viewing task). Results. Patients explored objects less than controls did. Controls explored the part needed to identify an object in the object-naming task and the whole object in the action-naming and free-viewing tasks. In contrast, the patients maintained their gaze on the “identity” part of the object in all three tasks. Conclusion. Our results were consistent with the literature findings on impaired action processing in schizophrenia but also extend the known impairment to implicit action processing when the subject is visually exploring an object. We discuss our results in terms of motivation, the effect of dopamine on eye movement, attentional capture, and frontal lobe dysfunction.

Eye movements during natural actions in patients with schizophrenia

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.

Visual exploration of objects and scenes in patients with age-related macular degeneration☆

OBJECTIVE Studies on people with age-related macular degeneration (AMD) have shown that they are able to detect briefly displayed objects and scenes with high accuracy (above 80%). However, in everyday life we explore our environment to search and to recognize objects. We assessed visual exploration in people with AMD during the identification of objects and scenes. METHOD Twenty patients with AMD, fifteen age-matched and twelve young controls participated. We used colored photographs of isolated objects, natural scenes and objects in scenes, displayed centrally on a monitor. Participants were asked to name the objects and scenes. Ocular movements were recorded during the identification task. Scan paths, saccades, fixations, and accuracy were also recorded. RESULTS People with AMD exhibited lower accuracy (by about 30%). Eye movement parameters were impaired with a larger number of saccades, shorter fixation durations and a larger scan path than controls. CONCLUSIONS Our results are consistent with studies on artificial scotoma in normally sighted people showing that a central scotoma impairs oculomotricity. In contrast to detection tasks, people with central vision loss exhibit impaired performance in identification of objects and scenes (62 to 66%). Eye movement studies suggest that the lower accuracy in patients is likely due to the use of peripheral vision and instability of fixation.

Visual exploration and action processing in schizophrenia

Introduction. Visual scanning is widely reported to be abnormal in schizophrenia. The majority of eye movement studies in schizophrenic patients have used pictures of a face in isolation in free viewings. This study was designed to examine whether attentional control, through instructions, modulates the visuomotor behaviour in schizophrenia with pictures presenting a face accompanied by its body, and to investigate the ability of schizophrenic patients to recognise others’ actions. Method. Visual scan paths were monitored in 26 schizophrenic patients and 26 controls. Participants performed three tasks in which they were asked either to look at the picture in any way they liked, to determine the characters gender, or to recognise the action that the character was making with an object. Results. Patients explored less the pictures than controls in the free viewing. Their scan paths did not differ from that of controls in the active viewings, though patients tended to “avoid” looking at the characters face in the action recognition task. Conclusion. The results show that patients are able to normalise their pattern of exploration as a function of task demands. The results are discussed in relation to attentional control, cognitive flexibility, dopamine, and processing of context information.