Visuospatial Attention, Eye Movements and Instrumental Activities of Daily Living (IADLs) in Alzheimer's Disease

The aim is to understand which components of attentional deployment and selection are impaired in AD during searching in realistic scenes on a computer screen (Experiment 1) and in a natural setting (Experiment 2).The investigators will also examine how deficits in visual exploration may be related to impairments in semantic, long-term memory (LTM) and working memory (WM) representations by manipulating the semantic consistency between the target and its visual surroundings, and the type of target cue (abstract vs. precise), respectively. Perceptual saliency of target and distractor objects will be also manipulated in Expt.1, In Expt.2, in order to determine how deficits in visual exploration may be involved in the IADL deficits shown by AD patients, participants at each trial will be required to search in a natural settings different types of targets and then to perform an IADL using five objects, among which one of the searched targets. Measures analysed: for the search tasks (Expt. 1 and 2): eye movements in different search phases, accuracy and response times; for IADLs tasks (Expt. 2): eye movements during action planning and execution, motor efficiency (number and types of action performed), time to terminate the activity. Compared to controls, the investigators expect that AD patients will have reduced ability using scene semantic LTM in order to locate the objects, greater attentional capture from highly salient features and greater search performance impairment when higher WM resources are required (abstract target cues). The investigators also expect that their performance at IADLs will be less efficient and, in particular, less organized than control, with reduced advantage of eye guidance.