Thesis defense Marlies van Kessel (Donders Series 172)

26 November 2014

Promotors: Prof.dr. L. Fassotti, Prof.dr. W. H. Brouwer

Nothing left? How to keep on the right track - Spatial and non-spatial attention processes in neglect after stroke

Visuospatial neglect is a clinical syndrome occurring in a considerable number of patients after cerebrovascular stroke, mostly in the right hemisphere. Patients with neglect typically fail to explore the half-space contralateral to the cerebral lesion. From a theoretical point of view, neglect is usually described as a spatial attention deficit, leading to asymmetric performance levels on the contralesional as compared to the ipsilesional side. Moreover, non-spatial attentional deficits have been found to modulate and aggravate spatially lateralized neglect phenomena. Thus, an increase of attentional load may lead to an aggravation of neglect symptoms. In this thesis, a computerized (virtual reality) driving simulator task was used to assess the relationship between spatial and non-spatial attention processes in stroke patients. Using a single detection time task, it was observed that the presence of general attention deficits contributed to the exacerbation of neglect symptoms and a worsening of test performance in RH patients with a lateralized bias. Using a dual task version of the driving simulator task in left and right hemisphere stroke patients, it was observed that increased attentional load may result in different degrees of lateralized and general attentional problems. In some patients with neglect symptoms, attentional asymmetries were clearly augmented under increased attentional load. Moreover, the dual task brought about asymmetries in some patients without neglect symptoms on simpler tasks. Thus, dual task performance may draw attention towards patients who, without obvious signs of neglect on paper-and-pencil tasks, may show visuospatial attention deficits in complex situations.

Finally, we investigated if it were possible to improve a well-known training method for visual scanning training by adding a training variant of the virtual reality dual task to a standardized training procedure. Although significant improvements after training were observed in both groups taken together on most tasks, no additional positive effects of dual task training were observed in the experimental group.