Emily R. Waldum

Dual pathways to prospective remembering.

According to the multiprocess framework (McDaniel and Einstein, 2000), the cognitive system can support prospective memory (PM) retrieval through two general pathways. One pathway depends on top–down attentional control processes that maintain activation of the intention and/or monitor the environment for the triggering or target cues that indicate that the intention should be executed. A second pathway depends on (bottom–up) spontaneous retrieval processes, processes that are often triggered by a PM target cue; critically, spontaneous retrieval is assumed not to require monitoring or active maintenance of the intention. Given demand characteristics associated with experimental settings, however, participants are often inclined to monitor, thereby potentially masking discovery of bottom–up spontaneous retrieval processes. In this article, we discuss parameters of laboratory PM paradigms to discourage monitoring and review recent behavioral evidence from such paradigms that implicate spontaneous retrieval in PM. We then re-examine the neuro-imaging evidence from the lens of the multiprocess framework and suggest some critical modifications to existing neuro-cognitive interpretations of the neuro-imaging results. These modifications illuminate possible directions and refinements for further neuro-imaging investigations of PM.

The selective directed forgetting effect: Can people forget only part of a text?

Participants studied sentences describing two different characters and then were told to forget the sentences about only one of the characters. A second list contained sentences attributed to a third character. Subsequently, they received a recall test on the sentences about the original two characters. When the sentences could be thematically integrated, participants showed no directed forgetting relative to a control group that was never told to forget. However, with unrelated sentences, participants selectively forgot the target characters sentences without forgetting the other characters sentences. This selective directed forgetting effect is a novel empirical result. We interpret the results as consistent with Radvanskys (1999) ideas about inhibition with textual materials.

Where is the forgetting with list-method directed forgetting in recognition?

Despite the fact that list-method directed forgetting instruction leads to decreases in memory performance on tests of free recall, there are to date no published reports of comparable effects in recognition testing. In the present article, we evaluated whether conditions that promote the importance of context in recognition, either via stimulus selection (Experiments 1 and 2) or by test choice (Experiment 3), elicit directed forgetting impairment. In all three experiments, we obtained reliable recognition deficits, suggesting that the typical conditions of recognition, rather than recognition itself, underlie the discrepancy between the tests of recognition and free recall in list-method directed forgetting.

Neural mechanisms of time-based prospective memory: evidence for transient monitoring.

In daily life, we often need to remember to perform an action after, or at, a specific period of time (e.g., take pizza out of oven in 15 minutes). Surprisingly, little is known about the neural mechanisms that support this form of memory, termed time-based prospective memory (PM). Here we pioneer an fMRI paradigm that enables examination of both sustained and transient processes engaged during time-based PM. Participants were scanned while performing a demanding on-going task (n-back working memory), with and without an additional time-based PM demand. During the PM condition participants could access a hidden clock with a specific button-press response, while in the control condition, pseudo-clocks randomly appeared and were removed via the same response. Analyses tested for sustained activation associated with the PM condition, and also transient activation associated with clock-checks and the PM target response. Contrary to prior findings with event-based PM (i.e., remembering to perform a future action when a specific event occurs), no sustained PM-related activity was observed in anterior prefrontal cortex (aPFC) or elsewhere in the brain; instead, transient clock-related activity was observed in this region. Critically, the activation was anticipatory, increasing before clock-check responses. Anticipatory activity prior to the PM target response was weaker in aPFC, but strong in pre-Supplementary Motor Area (pre-SMA; relative to clock-check responses), suggesting a functional double dissociation related to volitional decision-making. Together, the results suggest that aPFC-activity dynamics during time-based PM reflect a distinct transient monitoring process, enabling integration of the PM intention with current temporal information to facilitate scheduling of upcoming PM-related actions.

A role for memory in prospective timing informs timing in prospective memory.

Time-based prospective memory (TBPM) tasks require the estimation of time in passing-known as prospective timing. Prospective timing is said to depend on an attentionally driven internal clock mechanism and is thought to be unaffected by memory for interval information (for reviews see, Block, Hancock, & Zakay, 2010; Block & Zakay, 1997). A prospective timing task that required a verbal estimate following the entire interval (Experiment 1) and a TBPM task that required production of a target response during the interval (Experiment 2) were used to test an alternative view that episodic memory does influence prospective timing. In both experiments, participants performed an ongoing lexical decision task of fixed duration while a varying number of songs were played in the background. Experiment 1 results revealed that verbal time estimates became longer the more songs participants remembered from the interval, suggesting that memory for interval information influences prospective time estimates. In Experiment 2, participants who were asked to perform the TBPM task without the aid of an external clock made their target responses earlier as the number of songs increased, indicating that prospective estimates of elapsed time increased as more songs were experienced. For participants who had access to a clock, changes in clock checking coincided with the occurrence of song boundaries, indicating that participants used both song information and clock information to estimate time. Finally, ongoing task performance and verbal reports in both experiments further substantiate a role for episodic memory in prospective timing.

Prospective Memory Training: Outlining a New Approach.

Prospective memory (PM) tasks are those that must be performed in the future (e.g., attend an appointment). While these everyday tasks can be especially relevant for older adults (i.e., medication adherence), and have been associated with age-related decline, PM has been virtually overlooked in the cognitive training domain. This article describes the first comprehensive PM training intervention. Older adults (age 55 to 75) who received training completed 8 weekly PM training sessions that consisted of variable PM training tasks, strategy-focused discussion, and homework assignments. Those assigned to a control group completed only the first and last training task. On both a real-world proxy PM transfer task and the training tasks detailed here, there was a positive impact of PM training, suggesting practical benefits of the current training package for older adults. Benefits may also extend to other special populations who experience PM impairments (e.g., traumatic brain injury [TBI], Parkinson’s).

Age-related changes in neural mechanisms of prospective memory

The capability to remember and execute intentions in the future – termed prospective memory (PM) – may be of special significance for older adults to enable successful completion of important activities of daily living. Despite the importance of this cognitive function, mixed findings have been obtained regarding age-related decline in PM, and, currently, there is limited understanding of potential contributing mechanisms. In the current study, older (N=41) and younger adults (N=47) underwent task-functional MRI during performance of PM conditions that encouraged either spontaneous retrieval (Focal) or sustained attentional monitoring (Non-focal) to detect PM targets. Older adults exhibited a reduction in PM-related sustained activity within the anterior prefrontal cortex (aPFC) and associated dorsal frontoparietal cognitive control network, due to an increase in non-specific sustained activation in (no-PM) control blocks (i.e., an age-related compensatory shift). Transient PM-trial specific activity was observed in both age groups within a ventral parietal memory network that included the precuneus. However, within a left posterior inferior parietal node of this network, transient PM-related activity was selectively reduced in older adults during the non-focal condition. These age differences in sustained and transient brain activity statistically mediated age-related declines in PM performance, and were potentially linked via age-related changes in functional connectivity between the aPFC and precuneus. Together, they support an account consistent with the Dual Mechanisms of Control framework, in which age-related PM declines are due to neural mechanisms that support proactive cognitive control processes, such as sustained attentional monitoring, while leaving reactive control mechanisms relatively spared.