Cortex; a journal devoted to the study of the nervous system and behavior
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Homonymous visual field defects are a frequent consequence of brain damage occurring in some 20-40% of stroke patients. They are often accompanied by a peculiar spatial bias termed "Hemianopic Line Bisection Error" (HLBE). Although known for more than 100 years the explanations for the HLBE put forward remain controversial. ⋯ In the present article we summarize the main arguments of both theoretical positions and argue that although both accounts are valid, they are incomplete and several important issues remain unresolved. These include the potential contribution of eccentric fixation to the HLBE, the question of multimodal impairments, the role of (visuo)-motor processes, the relation between the HLBE and visual field recovery, and the exact clinical significance of the HLBE. Thus, far from concluding the research on the line-bisection error in hemianopia, the recent series of publications on this topic serve as a welcome reminder of how much more research is needed.
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The contralesional line bisection error in unilateral homonymous hemianopia is a frequent but neglected clinical phenomenon. Our knowledge about this bisection error is based on small samples of hemianopic patients. Moreover, horizontal line bisection has never been investigated in other unilateral visual field defects. ⋯ It is frequently associated with any unilateral homonymous visual field defect, i.e., hemianopia, upper/lower quadranopia, paracentral scotoma. Moreover, our results further support the recent finding that the contralesional bisection error is not a direct consequence of the visual field defect. Yet, they also suggest that, although the visual field defect does not seem to be the primary cause of the contralesional bisection error, it may nevertheless contribute to it.