Visual search in patients with subcortical vascular dementia: short fixations but long reaction times.

Visual search is a cognitive function of high ecological relevance. It involves rapid alternations between allocating and shifting attention. In patients with Alzheimer's disease, the duration of fixations during visual search increases already in the early stage of the illness. Subcortical vascular dementia (SVD), a newly defined subgroup of vascular dementia, has not yet been examined in this respect. SVD affects patients with a history of lacunar infarctions and/or transient ischemic attacks, focal neurological signs and evidence of subcortical white matter lesions as well as lacunes in the deep grey matter. Here, we report our findings from tracking eye movements during a visual search task with different array sizes in 9 patients with SVD and compare the number and duration of eye fixations they made with the values obtained in 9 healthy elderly control subjects. While patients with SVD were significantly slower in the tasks with longer center to target distances (mean reaction time), the number and duration of fixations they made did not differ from those in controls. Impairment of visual search in patients with SVD seems to be an effect of general cognitive slowing in more demanding arrays of visual search rather than a specific deficit in parameters of eye fixation.