Methods & Materials: A total of 23 elderly individuals (11 females and 12 males) voluntarily participated in the investigation: 13 patients with Alzheimer's disease (AD) and 10 healthy elderly individuals. The experimental setup consisted of (a) single -task and (b) dual-task trials at two levels of difficulty. In singletask condition, the participants were asked to recite the months of the year continuously with normal order (easy) and backward (difficult). They also performed a computerized visuospatial/motor tracking task. The participants then performed the tracking task in conjunction with each of the months reciting tasks as dual-task condition.

Results: The results showed a significant interaction (disease×level of difficulty) effect. So that, the performance impairment on combine performance in two simultaneous tasks was related to task difficulty, but the elderly control group did not differ in the easy and difficult conditions.

Conclusion: These findings not only increase our understanding of the attention deficits in AD patients, but also have implications for the mediating effect of cognitive load in using dual-task paradigm for studying attention mechanisms of cognitively suffered individuals.