Task switching in mild cognitive impairment: switch and nonswitch costs.

The ability to switch rapidly and fluidly between tasks is an important component of many everyday activities. In this study, we used a predictable, externally cued task-switching paradigm to investigate executive control processes in individuals with mild cognitive impairment (MCI). Participants were 26 individuals with amnestic MCI and 26 healthy older adult (OA) controls. In the mixed-task trials, participants switched between classifying whether a digit was odd/even or a letter was a consonant/vowel on every fourth trial. In the single-task trials, participants completed only the digit task or letter task throughout the entire block. Task switching costs were decomposed into nonswitch costs, which reflect the dual nature of the task, and switch costs, which reflect set-shifting abilities. The results revealed that the MCI group was not affected more than the healthy OAs by the requirement of keeping two tasks sets active in working memory (nonswitch costs). In contrast, the cost of switching between the two tasks was significantly greater for the MCI group compared with the OA controls (switch costs). Future research is needed to better understand the nature and implications for daily living of the greater switch costs found for individuals with MCI. (JINS, 2009, 15, 103-111.).