The impact of Dual-Tasking on mnestic performance in normal aging

Multitasking has become a necessity in our daily routines. Older people in developed countries are subject to ever-increasing cognitive demands, and the way they multitask has been raising significant interest. Recent research has focused on the clinical relevance of the motor-cognitive dual-task, partially neglecting the potential of concurrently using two cognitive tasks. Here, we devised a new, computer-based, cognitive-cognitive dual task to study the relationship between dual-task cost, age, and cognitive efficiency (MoCA and TMT) in a group of healthy participants (aged 50-77 years). Participants were tested with a primary visual memory task (free recall or forced choice) and a secondary phonemic fluency task, either concurrently (dual-tasking) or non-concurrently (single task). As expected, primary and secondary task performance was lower in free recall and further decreased with concurrent task demands and increasing age. Older participants did not suffer more than younger people from increased cognitive load in free recall, where the cost was higher. In the easiest, forced choice condition, younger participants made few of no errors. The cost in the phonemic tasks was stable across the age range. The mnestic cost positively correlated with two other measures of divided attention while no correlation was found with the MoCA score. This might be compatible with the presence of a core ability allowing to split attention for the parallel processing of information with different nature. In conclusion, cognitive-cognitive dual-tasks provide a sensitive measure of age-related changes in cognitive efficiency and could result in the development of more sensitive clinical tasks for the early detection of cognitive impairments.