Prospective memories and working memory: shared resources or distinct mechanisms?

Prospective memory (PM) is a complex process involving multiple cognitive abilities. Several studies demonstrated the role of working memory (WM) in PM. However, to date, the extent to which PM and WM shared resources or, rather, they are distinct mechanisms is still debated. With the aim to investigate the role of WM in PM, we developed two experiments manipulating the WM load required by ongoing tasks to examine a patient with PM difficulties and dysexecutive syndrome following brain damage. Experiment 1 required a simple arithmetic activity together with a PM switching-task to be performed at a given time (time-based condition) or following cue presentation (event-based condition). In Experiment 2, we varied the complexity of the ongoing task (PASAT test). Patient MB's performance in PM tasks significantly differs from the controls only in the PASAT time-based condition. We demonstrated a partial independence between WM and PM in tasks involving automatic retrieval.