Executive functions and prospective memory: clinical evidences on a multiprocess framework on planning actions

Recent studies demonstrated the role of executive functions in Prospective Memory (PM), even though it is still debated how these processes are overlapped. Our aim was to understand the role of executive functions in PM. Thus, we developed an experimental procedure in which we manipulated the level of executive load required by cognitive tasks. Experiment 1 required a simple arithmetic activity together with a PM 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 (a PASAT test) maintaining the same procedure of Experiment 1. We examined the effect of executive load manipulation in a patient (man, 52 y.o.) with a severe disexecutive syndrome following post-anoxic brain damage and 9 healthy participants. Patient’s performance significantly differed in PM accuracy only in PASAT-time condition. The difference between simple arithmetic and PASAT task in time- based condition was statistically significant as compared to the difference observed in the control sample. No differences were found in event-based conditions. These results suggested a partial independence between executive functions and PM in tasks involving an automatic retrieval of PM intention (event based). Nevertheless, these mechanisms seem to share resources in complex tasks requiring PM self-retrieval (time based). Our findings support a multiprocess framework, which assumes the role of controlled processes in PM under certain task conditions and emphasized the strong influence of planning, monitoring and attention abilities even in complex daily-life PM tasks.