The social impact of having or losing a drivers license is not to be underestimated since driving is no longer seen as a privilege but as an expectation. Furthermore, as it is often critical for the independence of older persons, decisions whether an elderly is unfit to drive should not be taken rashly. In this project we will study visual field defects because they are important age-related visual impairments that may affect fitness to drive. We will particularly focus on hemianopia, which is the most frequent visual field disorder after postchiasmatic brain damage (Zihl, 1994) and since previous research has shown that primary visual functions do not predict fitness to drive (e.g. Ball and Rebok, 1994) , we will assess the influence of disorders of visual attention on driving. A distinction will be made between the occurrence of hemianopia after damage to the optical tracts and primary visual cortex and hemianopia that results from damage of also other parts of the brain. In the latter group, the visual field defect may be accompanied by more or less subtle cognitive and motor impairments. We are particularly interested in manifestations and disorders of visual-spatial attention. An important neuropsychological attentional disorder which will be focused upon is the Unilateral Neglect Syndrome (UNS). We are specifically interested in the effect of mild manifestations of this syndrome, particularly if the neglect involves the ambient space representation, a dynamic global representation of the environment which allows focal attention to tune in on detail. Among the attentional theories recently advanced explaining UNS, a cognitive interpretation is that hemi-neglect is a multi-component syndrome consisting of an early automatic orienting of attention to the half space ipsilateral to the lesion followed by a disability to disengage attention automatically from its previous focus (e.g. Gainotti et al., 1991). We are particularly interested in the first component (attentional bias) which is interpreted in terms of saliency. We are currently in the process of developing a framework (attentional model) to understand and integrate this concept. We will attempt to relate measures of this attentional bias to parameters involving fitness to drive. This theoretical part comprises the first aim of the project namely a better understanding of the effects of visual field defects caused by brain damage on visual attention and driving competence. The observed relationships between visual attention and driving competence will then be incorporated into a training program in an attempt to improve fitness to drive. (A)
Samenvatting