Abstract
ObjectiveTime-based prospective memory (PM), remembering to do something at a particular moment in the future, is considered to depend upon self-initiated strategic monitoring, involving a retrieval mode (sustained maintenance of the intention) plus target checking (intermittent time checks). The present experiment was designed to explore what brain regions and brain activity are associated with these components of strategic monitoring in time-based PM tasks.Method24 participants were asked to reset a clock every four minutes, while performing a foreground ongoing word categorisation task. EEG activity was recorded and data were decomposed into source-resolved activity using Independent Component Analysis. Common brain regions across participants, associated with retrieval mode and target checking, were found using Measure Projection Analysis.ResultsParticipants decreased their performance on the ongoing task when concurrently performed with the time-based PM task, reflecting an active retrieval mode that relied on withdrawal of limited resources from the ongoing task. Brain activity, with its source in or near the anterior cingulate cortex (ACC), showed changes associated with an active retrieval mode including greater negative ERP deflections, decreased theta synchronization, and increased alpha suppression for events locked to the ongoing task while maintaining a time-based intention. Activity in the ACC was also associated with time-checks and found consistently across participants; however, we did not find an association with time perception processing per se.ConclusionThe involvement of the ACC in both aspects of time-based PM monitoring may be related to different functions that have been attributed to it: strategic control of attention during the retrieval mode (distributing attentional resources between the ongoing task and the time-based task) and anticipatory/decision making processing associated with clock-checks.
Highlights
Many daily life activities involve execution of non-routine delayed intentions, such as attending a meeting, taking a child to the doctor or calling a friend on her birthday
Common brain regions across participants, associated with retrieval mode and target checking, were found using Measure Projection Analysis. Participants decreased their performance on the ongoing task when concurrently performed with the time-based Prospective Memory (PM) task, reflecting an active retrieval mode that relied on withdrawal of limited resources from the ongoing task
With its source in or near the anterior cingulate cortex (ACC), showed changes associated with an active retrieval mode including greater negative event-related potentials (ERPs) deflections, decreased theta synchronization, and increased alpha suppression for events locked to the ongoing task while maintaining a time-based intention
Summary
Many daily life activities involve execution of non-routine delayed intentions, such as attending a meeting, taking a child to the doctor or calling a friend on her birthday. These are referred to as Prospective Memory (PM) tasks. Research in prospective memory has focused on event-based prospective memory tasks (e.g. remembering to give a message to a colleague when you see her in the corridor), in which an environmental event signals the moment to retrieve the intention. Less attention has been paid to time-based prospective memory tasks, when the retrieval of the intention is signalled by the passage of time and the intention is initiated in the absence of an external event (e.g. remember to call someone in 10 minutes). Most theories of PM have not explicitly considered time-based PM tasks [8,9,10] and little is known about monitoring mechanisms in timebased PM tasks
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