Visuospatial asymmetry in dual-task performance after subacute stroke

Various authors have referred to an association between neglect and non-spatial components of attention. It has been suggested that an increase in attentional load could exacerbate neglect symptoms and reveal subtle, well-compensated neglect. In the present study, 21 RH and 22 LH subacute stroke patients and 20 controls performed a computerized single-detection task (CVRT) and a dual task (CVRT-D) combining the detection task with a driving simulation task. Omissions, reaction times (RTs) and RT asymmetries were analysed to investigate the influence of increasing attentional load on neglect symptoms. RT asymmetries were most pronounced in RH patients. Although a clear increase in RT asymmetries between CVRT and CVRT-D was observed, the amount of increase did not differ between both patient groups. Within both patient groups, correlations between RT asymmetries and ipsilesional RTs as a measure of general attention were significant in the single task but not in the dual task, indicating that increased attentional load may result in different degrees of lateralized and general attentional problems. Half of the patients with neglect on the BIT (Behavioural Inattention Test) showed increased RT asymmetries from CVRT to CVRT-D. Moreover, two LH and RH patients without neglect symptoms on the BIT and CVRT showed distinctively increased asymmetries in the CVRT-D, fostering the idea of an emergence of subtle neglect under increased attentional load. Dual-task performance may draw attention towards patients who, without obvious signs of neglect, may show visuospatial attention deficits in complex situations.