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Louise-Ann Leyland, Hayward J. Godwin, Valerie Benson, Simon P. Liversedge; Eye Movements in Patients with Hemispatial Neglect: Why is Information Neglected?. Journal of Vision 2013;13(9):792. doi: https://doi.org/10.1167/13.9.792.
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It has not yet been established whether hemispatial neglect, the failure to respond to contralesional information after stroke, occurs due to an information sampling deficit or impaired processing of contralateral information during fixation. To address this, we recorded eye movements of acute (<3 months post-stroke) neglect patients (NPs), stroke controls without neglect (SCs), and older adult controls (OACs) whilst participants completed letter and clock cancellation tasks. Participants were required to search for two different target letters simultaneously amongst other distractor letters (dual-target search; 64 targets in total) and to find clocks displaying a predetermined time amongst other distractor clocks (single-target search; 40 targets in total). NPs were significantly poorer than the SCs and OACs at identifying contralateral targets on all tasks but had high accuracy for ipsilateral targets. Interestingly, NPs made contralateral saccades to the same extent as the control groups. In line with previous research (e.g. Walker, & Young, 1996), NPs spent a smaller proportion of the total trial time fixating the contralateral regions. Additionally, a disproportionate amount of time was spent scanning ipsilaterally, suggesting hyper-attention to this area. This sampling deficit was further exacerbated by higher cognitive load (i.e. dual-search). Importantly, during completion of the clock cancellation tasks, average contralateral gaze durations (time spent fixating a region before transgressing a region boundary), but not ipsilateral gaze durations, were significantly inflated compared to controls. This is indicative of problems associated with processing (encoding or representing) information in this region. The results not only provide support for biased visual sampling in neglect, but also demonstrate that during contralateral visual sampling, disruption in processing was evident. This has implications for the efficacy of interventions that shift involuntary eye movements into the neglected area (e.g. prismatic adaptation), as even when neglect patients visually sample information, they often still fail to perceive it.
Meeting abstract presented at VSS 2013
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