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Abstract:
It has been suggested that the rightward bias that
characterizes left spatial neglect is due to a disturbed
body-centric frame in which the subjective body midline is
displaced to the right. If this hypothesis is correct then features
of neglect may be simulated in normal subjects by displacing the
body midline. The first experiment tested this possibility by
measuring simple reaction times (RTs) to lateralized visual stimuli
in normal volunteers (n=12) with the body centered versus with the
body rotated 30° to the left or right with respect to the head.
The results indicate that a rightward rotation of body midline
leads to a rightward bias in RTs (right visual field detection
latencies faster than left visual field detection latencies). In
contrast, leftward rotation produces no reliable effect on RTs.
This basic pattern was replicated in a subsequent experiment which
also demonstrated that the rightward bias effect is additive with
target intensity. Thus, simple visuomotor performance is affected
by the perceived location of body midline. The underlying
mechanisms and their relation to clinical neglect are
discussed.
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