Specific impairments of selective attention in mild Alzheimer's disease

The aim of the present study was to evaluate selective visual attention in subjects affected by Alzheimer's Disease (AD), by means of a computerized spatial exploration test that adopts a Touch Screen (TS) interface, which has already proved able to characterize alternative strategies in performing search tasks. We assessed a group of 16 patients affected by mild to moderate AD, comparing them with 16 control subjects matched for age and education. In the experimental tasks the performance of the AD patients was worse than that of the normal elderly, both quantitatively (slower speeds) and qualitatively (poorer planning and higher number of omissions and perseverations). In the visual attention tasks there appeared to be no close connection between AD patients' performance and increased Reaction Times (RT); this evidenced a specific role of non-elementary cognitive structures enclosed in a higher attentional domain, rather than a general decrease in the speed of basic cognitive processes. Our results are in line with specific AD literature: while psychomotor speed and lower attention levels (sensorimotor) are preferentially impaired in subcortical forms of dementia, the higher levels of selective and divided attention could be the first to deteriorate and appear more markedly disrupted in the Alzheimer type of dementia.