Abstract
Objective: Right-hemisphere stroke may cause an ipsilesional attention bias and left hemispatial neglect. Computerized time-limited tasks are more sensitive than conventional paper–pencil tests in detecting these spatial attention deficits. However, their frequency in the acute stage of stroke, the neuroanatomical basis and functional relevance for patients’ everyday life are unclear. Method: A realistic visual search task is introduced, in which eye movements are recorded while the patient searches for paperclips among different everyday objects on a computer display. The “desk task” performance of 34 acute right-hemisphere stroke patients was compared to established paper–pencil tests for neglect and the Posner reaction time task, and finally correlated to structural brain lesions. Results: Most of the patients, even those without clinical neglect signs and with normal paper–pencil test performance, exhibited a clear ipsilesional attention bias in the desk task. This bias was highly correlated to the left-right asymmetry in the Posner task and to neglect-related functional impairment scores. Lesion-symptom mapping revealed task-specific differences: deficits in the desk task were associated with lesions of the superior temporal gyrus, contralesional unawareness in the Posner task with ventral frontal cortex lesions and paper–pencil cancellation bias with damage to the inferior parietal lobe. Neglect behavior was further associated with distinct frontoparietal white matter tract disconnections (inferior longitudinal fasciculus, superior longitudinal fasciculus, arcuate). Conclusions: Results from the novel desk task indicate a functional relevance of spatial attention deficits in right-hemisphere stroke patients, even if they are “subclinical.” This should be considered especially in patients without obvious clinical neglect signs.
Highlights
Using a novel computerized task that simulated a real-life visual search situation, we have shown that acute right-hemisphere stroke patients both with and without clinical signs of spatial neglect exhibit a functionally relevant ipsilesional spatial attention bias that leads to misses of contralesional targets and a rightward shift of exploratory eye movements
In acute right-hemisphere stroke patients who showed normal performance in the paper-and-pencil test battery for spatial neglect (“no neglect” group), the lateralized deficit was evident in the novel visual search task as in the Posner reaction time (RT) task
Different studies previously showed that the ipsilesional deviation of exploratory eye movements is a typical sign of spatial neglect (Behrmann, Ebert, & Black, 2004; Hornak, 1992; Karnath, Niemeier, & Dichgans, 1998; Ptak, Golay, Müri, & Schnider, 2009) and that this oculomotor bias even seems to be especially sensitive for the detection of mild neglect in the chronic stage (Pflugshaupt et al, 2004)
Summary
ParticipantsThe study has been approved by the local Ethics Committee of the University of Lübeck (AZ 12– 064). For the assessment of primary afferent visual field defects, each of the four quadrants were stimulated by peripheral finger wiggling two times in a random order and the patients were asked to verbally respond by indicating the side of the stimulus. If a stimulus was missed both times on unilateral stimulation, a visual field defect was documented. Those patients with quadrantanopia or hemianopia were excluded from the study and did not undergo further testing. In case of intact visual fields, a bilateral stimulation with peripheral finger wiggling in the upper or lower quadrants was performed (again two runs each) and visual extinction was documented if the contralesional stimulus was missed at least once on bilateral stimulation. As opposed to primary visual fields defects, was no exclusion criterion
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