INHIBITORY PROCESSES IN COVERT ORIENTING IN PATIENTS WITH ALZHEIMERS-DISEASE

Previous studies of covert orienting in Alzheimer's disease (AD) have investigated exogenous and endogenous processes separately. We aimed t o investigate how the 2 modes of orienting interact to control attenti on in healthy older participants and patients with AD. The covert orie nting of visual attention task (COVAT) with abrupt onset cues was used in all experiments. In Experiments 1 and 2, predictive information wa s added to cues to initiate an endogenous orienting response. Results showed that healthy older participants were able to use endogenous pro cesses to inhibit exogenous orienting. In contrast, patients with AD w ere unable tp inhibit exogenous orienting to cues even when targets ra rely appeared there. Experiment 3 investigated inhibition of return (I OR) in patients with AD. Both healthy older controls and patients with AD showed a normal IOR, suggesting that exogenous orienting processes are relatively unaffected by the normal aging process or in patients with AD. A model of covert orienting in which exogenous and endogenous orienting processes interact to control attentional behaviors is disc ussed.