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Neurophysiological Measures of Task-Set Switching: Effects of Working Memory and Aging

¹ Department of Psychology, Concordia University, Montreal, Québec, Canada.
² Centre for Research in Human Development, Concordia University, Montreal, Québec, Canada.
³ Lady Davis Institute for Medical Research/Jewish General Hospital, Montreal, Québec, Canada.

Address correspondence to Natalie A. Phillips, PhD, Department of Psychology, Concordia University, Centre for Research in Human Development, 7141 Sherbrooke Street West, Montréal, Québec, Canada, H4B 1R6. E-mail: Natalie.Phillips{at}concordia.ca

We investigated age-related differences in task-switching performance by using behavioral measures and event-related brain potentials. We tested younger and older adults, and we separated older adults into groups with high and low working memory (WM); that is, we separated them into old–high-WM and old–low-WM groups. On average, all participants responded more slowly in mixed-task than in single-task blocks (i.e., reaction time or RT mixing cost). Younger adults and old–high-WM participants had equivalent RT mixing costs and showed larger posterior negative slow-wave activity when preparing for mixed trials than for single-task trials, suggesting that mixed-task trials required trial-to-trial preparation. Old–high-WM participants also showed frontally distributed activity on mixed-task trials, suggesting their use of executive control to offset age-related differences in mixed-task preparation. In contrast, old-low-WM participants had large RT mixing costs and large posterior event-related brain potential negativities during single-task trials, suggesting that they prepare during single- and mixed-task blocks. High WM, therefore, may help older adults offset the age-related difficulties often observed when they are task switching.

Key Words: Task switching • Mixing cost • Working memory • Event-related brain potentials • Negative slow wave