Apathy and executive dysfunction in Alzheimer disease.

Apathy, defined as a reduction in voluntary goal-directed behaviors, is one of the most common behavioral symptoms encountered in Alzheimer disease (AD). However, the processes underlying the different components of apathy are still unclear. The aim of this study was to explore a particularly important aspect of executive function in daily life: multitasking [assessed with the Modified Six Elements Task (MSET)], and its relationship with apathy in AD. Sixty-seven participants (37 AD patients matched with 30 control participants) were screened using the MSET. Simultaneously, a close relative of each patient was given the Apathy Inventory, which assesses 3 distinct dimensions of apathy (lack of initiative, lack of interest, and emotional blunting). AD patients presented significantly more multitasking deficits than control participants. In addition, regression analyses revealed that the number of rule breaks on the MSET (inability to perform several tasks in a predefined time observing a number of rules) was the best predictor of apathy, and especially of lack of initiative. These results suggest that the relation between lack of initiative and multitasking has a specific character and that mechanisms underlying multitasking constitute a key component of goal-directed behaviors.