Selective visual attention in Alzheimer's and Parkinson's patients: memory- and data-driven control.

An automated visual search experiment was carried out on patients with incipient Alzheimer's disease, non-demented Parkinsonians and healthy controls to test for selective attention control within the framework of the Norman and Bobrow (1975) model. The performances of the Parkinsonians and healthy controls were consistent with the predictions of this model but those of the Alzheimer patients were not. These patients appeared to be no longer sensitive to the facilitation supplied by the stimulus context and to spend most of their residual resources on achieving accuracy. The reduction of their attentional resources possibly interferes with the control of the speed-accuracy trade-off.