Mechanisms underlying hemispatial neglect

TLDR

Patients with left‑sided hemispatial neglect bisect lines incorrectly due to hemianopia or sensory hemiinattention, and moving the line toward the normal half of body space is hypothesized to improve performance. The study investigates whether hemispatial neglect is caused by a hemispatial memory defect. Six right‑hemisphere infarct patients with left‑sided neglect identified a letter at either end of a line before bisecting it, with lines positioned at the right, center, or left of the body midline. Patients performed equally when required to look left or right, but performed better when the line was placed to the right side of the body, supporting hemispatial hypokinesia; despite seeing the left side, they could not form a stable trace and behaved as if they did not see it.

Abstract

Abstract If patients with left‐sided hemispatial neglect bisect lines incorrectly because hemianopia or sensory hemiinattention prevents them from seeing how far the line extends to the left, a strategy that ensures their seeing the left side of the line in their normal field should improve performance. If patients have hemispatial hypokinesia, moving the line toward the normal half of body space should improve performance. Six patients with left‐sided neglect from right hemisphere infarctions were required to identify a letter at either the right or the left end of a line before bisecting that line. The task was given with the lines placed at either the right, the center, or the left of the body midline. Performance in trials when subjects were required to look to the left before bisecting a line did not differ from when they were required to look right. Performance was significantly better when the line was placed to the right side of the body than to the left. These observations support the hypothesis that patients with hemispatial neglect have hemispatial hypokinesia. An alternative hypothesis is that these subjects had a hemispatial memory defect. Although they saw the left side of the line in their normal field, they were incapable of forming a stable trace and performed as if they did not see the left side of the line.