The impact of dual-tasking on mnestic performance in normal ageing

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 computer-based, cognitive-cognitive dual task to study the relationship between dual-task cost, age, and cognitive efficiency (MoCA) in a group of sixty-one 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 significantly decreased with concurrent task demands and increasing age. Age and cognitive load however did not interact: The dual-tasking cost in visual Memory and in phonemic Fluency was stable across the age range we investigated. Participants with higher mnestic costs had lower performance also in other measures of divided attention (e.g. TMT) 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 non-pathological age-related changes in cognitive efficiency and could be used as baseline when developing more sensitive tests for the early detection of abnormal patterns possibly indexing cognitive impairments.