Visual exploration of dynamic real-world scenes in patients with hemispatial neglect

Visual exploration of everyday scenes requires shifts of attention performed by the use of saccadic eye movements. We do know that patients with hemispatial neglect show profound deficits in the exploration of static scenes and in visual search paradigms using abstract stimuli. However, little is known about their scanning behaviour in dynamic scenes, in particular when the moving real-world stimuli are presented in a visual search context. Given that visual attention is largely driven by the salience of visual targets and that motion is one of the strongest (most salient) cues, we wondered whether neglect patients' exploratory eye movements differ between naturalistic dynamic scenes and static images.

Using a remote eye tracking system at the bedside, we examined 19 patients with spatial hemineglect following acute right hemisphere stroke, 14 right-brain damaged patients without neglect and 21 healthy control subjects. Real-world scenes were presented as static photographs, dynamic scenes and in a visual search context.

We analyzed global saccade parameters such as saccadic amplitude and fixation duration, the spatial distribution of fixations as well as physical scene properties (local motion, colour and contrast). Preliminary results indicate that the pathological attentional rightward shift in neglect patients can be overcome by objects in the left hemi-field that are of higher interest and saliency (motion, contrast) than the right-sided objects. The cue „motion“ reduced the neglect behaviour even in the complex visual search task, in which left-sided targets were more likely to be found when they were moving. In the future, the use of modified real-world movies may be an interesting complement to current therapy schemes using static and abstract stimuli for the rehabilitation of neglect and associated visuo-spatial disorders.