Selective attention in a reaching task: effect of normal aging and Alzheimer's disease

This study examined the ability of young adults, older adults, and older adults suffering from Alzheimer's disease (AD) to perform a selective reaching task. Normal aging did not increase interference caused by distractors. In contrast, patients with AD showed massively increased effects of distractor interference. AD patients showed a high probability of making responses to distractor items. The proportion of these incorrect responses was related to the inability to use inhibitory processes, which increased with the severity of AD. Responses to distractors occurred despite the fact that patients could discriminate targets and distractors and knew that their responses to distractors were in error. These data suggest that AD patients are impaired in their ability to inhibit incorrect responses.