Abstract
Unilateral brain damage can lead to a striking deficit in awareness of stimuli on one side of space called Spatial Neglect. Patient studies show that neglect of the left is markedly more persistent than of the right and that its severity increases under states of low alertness. There have been suggestions that this alertness-spatial awareness link may be detectable in the general population. Here, healthy human volunteers performed an auditory spatial localisation task whilst transitioning in and out of sleep. We show, using independent electroencephalographic measures, that normal drowsiness is linked with a remarkable unidirectional tendency to mislocate left-sided stimuli to the right. The effect may form a useful healthy model of neglect and help in understanding why leftward inattention is disproportionately persistent after brain injury. The results also cast light on marked changes in conscious experience before full sleep onset.
Highlights
Correspondence and requests for materials should be addressed to Losing the left side of the world: Rightward shift in human spatial attention with sleep onset
Low alertness in the healthy population may provide a window for investigation of spatial bias that can result from brain injury
There may be a number of reasons for this including right-hemisphere dominance in aspects of spatial cognition and attention and prolongation of neglect by co-occurring deficits in alertness, themselves associated with right hemisphere function[13,14]
Summary
Losing the left side of the world: Rightward shift in human spatial attention with sleep onset. There may be a number of reasons for this including right-hemisphere dominance in aspects of spatial cognition and attention (making it more able to compensate for left hemisphere damage than vice versa12) and prolongation of neglect by co-occurring deficits in alertness, themselves associated with right hemisphere function[13,14] The latter argument has been supported by temporary amelioration in rightward bias that follows exposure to stimulating noises, thoughts or medication[15,16,17]. Following reports that some neurologically normal children with poor sustained attention can show left neglect[18,19], a series of studies with adults and children have shown significant within-subject rightward shifts in attentional bias with sleep deprivation[20], reduced night-time alertness[21], and after long periods of repetitive task performance[22]. Spatial neglect can be observed across modwww.nature.com/scientificreports
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