Assessment of left unilateral spatial neglect using illusory figures

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Unilateral spatial neglect is the failure to report, respond, or orient to novel or meaningful stimuli presented to the side opposite a brain lesion (Heilman, 1979). Traditionally unilateral spatial neglect is evaluated by using several visual exploration tests, such as the line cancellation task, or the line bisection task. The aim of the present study was to evaluate the new assessment technique using optical illusion. We performed three experiments employing the Wundt-Jastrow illusory figures to investigate the clinical application of this type of test and to evaluate the cognitive functions of the patients with left unilateral spatial neglect In the first experiment, the test was given to the patient with callosal lesion and clarified the attentional aspect of the cognitive function of the patient by using the Wundt-Jastrow Illusory figures. In the next experiment, we recorded the eye movement of this patient during the test His gaze quickly moved to the right side of the figure without substantial leftward search, To investigate precise eye fixation patterns, we performed the third experiment by using line bisection with structured presentation method. The results revealed that the patients were inferred line length mainly from the right endpoint of the stimulus. Through this series of experiments, it implies that the response to the illusory figure in patients with unilateral spatial neglect may reveal overattention to the right side of stimulus. Additional experiments confirmed that representational aspect of the deficit was also affected to these results.