The ipsilesional attention bias in right hemisphere stroke patients as revealed by a realistic visual search task: neuroanatomical correlates and functional relevance

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 fronto-parietal white matter tract disconnections (ILF, SLF, Arcuate). Conclusions: Results from the novel Desk task indicate a functional relevance of spatial attention deficits in right brain damaged patients, even if they are “subclinical”. This should be considered especially in patients without obvious clinical neglect signs.urology and Psychology, University of Lübeck.This work was supported by the Deutsche Forschungsgemeinschaft(Grants MA5332/1-1 and MA5332/3-1 to Björn Machner) and the Well-come Trust (Grants 091806 and 106926 to Paul M. Bays)