The effect of attentional dysfunction in Alzheimer's disease: theoretical and practical implications.

Attention may be one of the earliest cognitive abilities to change in Alzheimer's disease (AD), although its role has received belated recognition. This article discusses different aspects of attention and how these are differentially affected in AD. Of the various attention functions, divided and selective attention are particularly vulnerable. The etiology of attentional deficits in AD arises from damage to areas of frontal and parietal association cortex, disconnection between the anterior and posterior attentional networks, and decreased cholinergic function. Severity of illness is associated with attentional deterioration. Complexity or increased load of a task may further disrupt attentional function. Knowledge of attentional changes in AD is important to the understanding of disease-related changes in other cognitive domains such as memory, visuospatial functions, and language.