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Dissociation of near and far visuo-spatial left neglect in individuals who have had a stroke

1 May 1993


Presently, visuo-spatial left neglect is tested almost exclusively within reaching distance from the patient's body. Animal experiments and human case studies suggest that there may be separate areas in the brain for near and far visuo-spatial perception. One area of our brain may map the world that is within reaching distance, while a separate area maps the world beyond reaching distance. If so, there is a possibility that a stroke may damage only one of those areas, causing a dissociation of near and far visuo-spatial left neglect. Rehabilitation professionals may need to consider testing patients who have suffered a stroke at both reaching distance and throwing distance from the body in order to rule out a dissociated perceptual deficit prior to authorizing a patient's return to certain functional activities, such as driving an automobile. The aim of this investigation was to compare the signs of visuo-spatial left neglect at "reaching distance" and at "throwing distance" using a modified version of the line bisection task (a standard clinical test for left neglect). Eighteen individuals who had a stroke within ninety days prior to testing and seven age matched control subjects bisected five different size lines at distances of half a meter and two and a half meters. The bisections of the lines at the half meter distance were compared to the line bisections at the two and a half meter distance using a series of paired t-tests. Only three of the eighteen subjects with right cerebrovascular accidents demonstrated a possible dissociation across the two distances. However, these dissociations were not strong enough to support the theory of two separate spatial maps in humans.


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