Prospective Memory Retrieval Research Articles

Complex Real Life-Related Prospective Memory in Soldiers with and Without Post-Traumatic Stress Disorder

Objective: Posttraumatic stress disorder (PTSD) is known to influence memory functions in a complex fashion. However, little is known about the impact of PTSD on future directed mnemonic functions like prospective memory (PM). Methods: The present study aimed at examining performance of 13 soldiers with PTSD, 12 without PTSD and 21 non-military controls without PTSD across different phases of a real life-related PM paradigm. In addition, neuropsychological tests of memory and the influence of salivary cortisol levels on memory performance wereassessed.Results: Soldiers with PTSD performed significantly worse during the planning and retrieval phase of time- and event-dependent PM compared to the non-military controls, but not to soldiers without PTSD. Moreover, PTSD symptom severity correlated negatively with PM retrieval. In soldiers without PTSD time- and eventdependent PM was significantly declined during retrieval phase compared to the non-military controls. Significantly decreased salivary cortisol levels were detected only for soldiers with PTSD. Standard neuropsychological assessment showed significantly impaired working- and retrospective long-term memory in bothsoldiers with and without PTSD.Conclusion: Our results indicate for the first time that exposure to combat-related stress may have selective deteriorating effects on real-life-related PM and other memory functions in the absence of a PTSD diagnosis. We conclude that stress-related alterations of memory functions in soldiers may not only be related toPTSD-related changes in cortisol metabolism. Rather, additional neuropeptides and/or neurohormones may be involved in the emergence of memory dysfunctions resulting from combat-related stress.

Prospective memory mediated by interoceptive accuracy: a psychophysiological approach.

Previous studies on prospective memory (PM), defined as memory for future intentions, suggest that psychological stress enhances successful PM retrieval. However, the mechanisms underlying this notion remain poorly understood. We hypothesized that PM retrieval is achieved through interaction with autonomic nervous activity, which is mediated by the individual accuracy of interoceptive awareness, as measured by the heartbeat detection task. In this study, the relationship between cardiac reactivity and retrieval of delayed intentions was evaluated using the event-based PM task. Participants were required to detect PM target letters while engaged in an ongoing 2-back working memory task. The results demonstrated that individuals with higher PM task performance had a greater increase in heart rate on PM target presentation. Also, higher interoceptive perceivers showed better PM task performance. This pattern was not observed for working memory task performance. These findings suggest that cardiac afferent signals enhance PM retrieval, which is mediated by individual levels of interoceptive accuracy.This article is part of the themed issue ‘Interoception beyond homeostasis: affect, cognition and mental health’.

Impaired cue identification and intention retrieval underlie prospective memory deficits in patients with first-episode schizophrenia.

Schizophrenia is associated with impairment in prospective memory, the ability to remember to carry out an intended action in the future. It has been established that cue identification (detection of the cue event signaling that an intended action should be performed) and intention retrieval (retrieval of an intention from long-term memory following the recognition of a prospective cue) are two important processes underlying prospective memory. The purpose of this study was to examine prospective memory deficit and underlying cognitive processes in patients with first-episode schizophrenia. This study examined cue identification and intention retrieval components of event-based prospective memory using a dual-task paradigm in 30 patients with first-episode schizophrenia and 30 healthy controls. All participants were also administered a set of tests assessing working memory and retrospective memory. Both cue identification and intention retrieval were impaired in patients with first-episode schizophrenia compared with healthy controls ( ps < 0.05), with a large effect size for cue identification (Cohen's d = 0.98) and a medium effect size for intention retrieval (Cohen's d = 0.62). After controlling for working memory and retrospective memory, the difference in cue identification between patients and healthy controls remained significant. However, the difference in intention retrieval between the two groups was no longer significant. In addition, there was a significant inverse relationship between cue identification and negative symptoms ( r = -0.446, p = 0.013) in the patient group. These findings suggest that both cue identification and intention retrieval in event-based prospective memory are impaired in patients with first-episode schizophrenia. Cue identification and intention retrieval could be potentially used as biomarkers for early detection and treatment prognosis of schizophrenia. In addition, addressing cue identification deficit through cognitive enhancement training may potentially improve negative symptoms as well.

Acute social stress before the planning phase improves memory performance in a complex real life-related prospective memory task

Successful execution of intentions, but also the failure to recall are common phenomena in everyday life. The planning, retention, and realization of intentions are often framed as the scientific concept of prospective memory. The current study aimed to examine the influence of acute stress on key dimensions of complex “real life” prospective memory. To this end, we applied a prospective memory task that involved the planning, retention, and performance of intentions during a fictional holiday week. Forty healthy males participated in the study. Half of the subjects were stressed with the Socially Evaluated Cold Pressor Test (SECPT) before the planning of intentions, and the other half of the participants underwent a control procedure at the same time. Salivary cortisol was used to measure the effectiveness of the SECPT stress induction. Stressed participants did not differ from controls in planning accuracy. However, when we compared stressed participants with controls during prospective memory retrieval, we found statistically significant differences in PM across the performance phase. Participants treated with the SECPT procedure before the planning phase showed improved prospective memory retrieval over time, while performance of controls declined. Particularly, there was a significant difference between the stress and control group for the last two days of the holiday week. Interestingly, control participants showed significantly better performance for early than later learned items, which could be an indicator of a primacy effect. This differential effect of stress on performance was also found in time- and event-dependent prospective memory.Our results demonstrate for the first time, that acute stress induced before the planning phase may improve prospective memory over the time course of the performance phase in time- and event-dependent prospective memory. Our data thus indicate that prospective memory can be enhanced by acute stress.

Cognitive and neural plasticity in older adults' prospective memory following training with the Virtual Week computer game.

Prospective memory (PM) – the ability to remember and successfully execute our intentions and planned activities – is critical for functional independence and declines with age, yet few studies have attempted to train PM in older adults. We developed a PM training program using the Virtual Week computer game. Trained participants played the game in 12, 1-h sessions over 1 month. Measures of neuropsychological functions, lab-based PM, event-related potentials (ERPs) during performance on a lab-based PM task, instrumental activities of daily living, and real-world PM were assessed before and after training. Performance was compared to both no-contact and active (music training) control groups. PM on the Virtual Week game dramatically improved following training relative to controls, suggesting PM plasticity is preserved in older adults. Relative to control participants, training did not produce reliable transfer to laboratory-based tasks, but was associated with a reduction of an ERP component (sustained negativity over occipito-parietal cortex) associated with processing PM cues, indicative of more automatic PM retrieval. Most importantly, training produced far transfer to real-world outcomes including improvements in performance on real-world PM and activities of daily living. Real-world gains were not observed in either control group. Our findings demonstrate that short-term training with the Virtual Week game produces cognitive and neural plasticity that may result in real-world benefits to supporting functional independence in older adulthood.

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 effect of semantic context on prospective memory performance

The current study provides evidence for spontaneous processing in prospective memory (PM) or memory for intentions. Discrepancy-plus-search is the spontaneous processing of PM cues via disruptions in processing fluency of ongoing task items. We tested whether this mechanism can be demonstrated in an ongoing rating task with a dominant semantic context. Ongoing task items were manipulated such that the PM cues were members of a semantic category (i.e., Body Parts) that was congruent or discrepant with the dominant semantic category in the ongoing task. Results showed that participants correctly responded to more PM cues when there was a category discrepancy between the PM cues and ongoing task items. Moreover, participants' identification of PM cues was accompanied by faster ongoing task reaction times when PM cues were discrepant with ongoing task items than when they were congruent. These results suggest that a discrepancy-plus-search process supports PM retrieval in certain contexts, and that some discrepancy-plus-search mechanisms may result from the violation of processing expectations within a semantic context.

Response dynamics in prospective memory.

Prospective memory (PM) is the ability to remember to execute a delayed behavior. Most theoretical and empirical work on PM has focused on the attentional resources that might facilitate successfully executing a delayed behavior. In the present study, we enhance the current understanding of attention allocation and also introduce novel evidence for the dynamics of PM retrieval. We recorded mouse-tracking trajectories during a prospective memory task to examine the continuous nature of attentional processes that support PM cue retrieval. We found that the velocity profiles of response trajectories differed as a function of PM cue focality while controlling for the canonical measure of response time, supporting the notions that monitoring is evident in the continuous nature of response trajectories and that such trajectories are sensitive to cue focality. Conditional velocity profiles of ongoing task trials indicated that monitoring occurred when the processing of PM cues differed from ongoing task instructions (Nonfocal PM condition): responses were made later in the profile, suggestive of a more controlled retrieval process. Analysis of PM cue retrieval profiles indicated correctly retrieved Focal PM cues were qualitatively and quantitatively different from all other PM cue retrieval trials. This provides evidence that retrieval dynamics of a delayed behavior differ as a function of cue focality and suggests that controlled processing may contribute to spontaneous retrieval of a PM task.

Effects of cognitive training with and without aerobic exercise on cognitively demanding everyday activities.

We investigated the potential benefits of a novel cognitive-training protocol and an aerobic exercise intervention, both individually and in concert, on older adults' performances in laboratory simulations of select real-world tasks. The cognitive training focused on a range of cognitive processes, including attentional coordination, prospective memory, and retrospective-memory retrieval, processes that are likely involved in many everyday tasks, and that decline with age. Primary outcome measures were 3 laboratory tasks that simulated everyday activities: Cooking Breakfast, Virtual Week, and Memory for Health Information. Two months of cognitive training improved older adults' performance on prospective-memory tasks embedded in Virtual Week. Cognitive training, either alone or in combination with 6 months of aerobic exercise, did not significantly improve Cooking Breakfast or Memory for Health Information. Although gains in aerobic power were comparable with previous reports, aerobic exercise did not produce improvements for the primary outcome measures. Discussion focuses on the possibility that cognitive-training programs that include explicit strategy instruction and varied practice contexts may confer gains to older adults for performance on cognitively challenging everyday tasks.

Endogenous-cue prospective memory involving incremental updating of working memory: an fMRI study.

Prospective memory paradigms are conventionally classified on the basis of event-, time-, or activity-based intention retrieval. In the vast majority of such paradigms, intention retrieval is provoked by some kind of external event. However, prospective memory retrieval cues that prompt intention retrieval in everyday life are commonly endogenous, i.e., linked to a specific imagined retrieval context. We describe herein a novel prospective memory paradigm wherein the endogenous cue is generated by incremental updating of working memory, and investigated the hemodynamic correlates of this task. Eighteen healthy adult volunteers underwent functional magnetic resonance imaging while they performed a prospective memory task where the delayed intention was triggered by an endogenous cue generated by incremental updating of working memory. Working memory and ongoing task control conditions were also administered. The 'endogenous-cue prospective memory condition' with incremental working memory updating was associated with maximum activations in the right rostral prefrontal cortex, and additional activations in the brain regions that constitute the bilateral fronto-parietal network, central and dorsal salience networks as well as cerebellum. In the working memory control condition, maximal activations were noted in the left dorsal anterior insula. Activation of the bilateral dorsalanterior insula, a component of the central salience network, was found to be unique to this 'endogenous-cue prospective memory task' in comparison to previously reported exogenous- and endogenous-cue prospective memory tasks without incremental working memory updating. Thus, the findings of the present study highlightthe important role played by the dorsal anterior insulain incremental working memory updating that is integral to our endogenous-cue prospective memory task.

Taï chimpanzees anticipate revisiting high-valued fruit trees from further distances.

The use of spatio-temporal memory has been argued to increase food-finding efficiency in rainforest primates. However, the exact content of this memory is poorly known to date. This study investigated what specific information from previous feeding visits chimpanzees (Pan troglodytes verus), in Taï National Park, Côte d'Ivoire, take into account when they revisit the same feeding trees. By following five adult females for many consecutive days, we tested from what distance the females directed their travels towards previously visited feeding trees and how previous feeding experiences and fruit tree properties influenced this distance. To exclude the influence of sensory cues, the females' approach distance was measured from their last significant change in travel direction until the moment they entered the tree's maximum detection field. We found that chimpanzees travelled longer distances to trees at which they had previously made food grunts and had rejected fewer fruits compared to other trees. In addition, the results suggest that the chimpanzees were able to anticipate the amount of fruit that they would find in the trees. Overall, our findings are consistent with the hypothesis that chimpanzees act upon a retrieved memory of their last feeding experiences long before they revisit feeding trees, which would indicate a daily use of long-term prospective memory. Further, the results are consistent with the possibility that positive emotional experiences help to trigger prospective memory retrieval in forest areas that are further away and have fewer cues associated with revisited feeding trees.

No effects of executive control depletion on prospective memory retrieval processes.

Research has suggested that prospective memory retrieval is reliant on executive control processes, and the degree to which these processes are necessary for intention fulfillment is dependent on a host of variables related to the prospective memory task. Based on results suggesting that aspects of the prospective memory task vary in their need for executive control, the current study examined the possibility that executive control depletion from the Stroop task would negatively transfer to prospective memory performance. Depletion of executive control, measured objectively in a Stroop task, did not impair prospective memory performance in either low or high cue-target association conditions. However, participants' subjective assessments of their own cognitive fatigue correlated significantly with their prospective memory performance, regardless of the association between cues and target responses.

The functional neuroanatomy of spontaneous retrieval and strategic monitoring of delayed intentions

An intention stored in prospective memory (PM) for later execution can be retrieved either strategically through preparatory attentional processes such as active monitoring for PM targets or spontaneously through automatic retrieval processes when encountering a relevant cue. Using functional MRI to identify distinct brain areas involved in spontaneous retrieval of intentions and to dissociate them from monitoring-related processes, we compared brain activity in PM blocks in which subjects had to maintain and execute an intention in response to rarely occurring PM cues with blocks in which the previous intention had been completed. Although the PM task incurred performance costs in the ongoing task and was associated with increased block-related activation in the rostro-lateral prefrontal cortex (RLPFC), performance costs and RLPFC activation were no longer observed after the intention had been completed, providing further evidence for an involvement of RLPFC in strategic monitoring during PM tasks. By contrast, event-related activation induced by PM cues was observed in the ventral parietal cortex (VPC), precuneus and posterior cingulate cortex even after the intention was completed. These activations are consistent with the notion of spontaneous intention retrieval possibly mediated through a bottom-up driven re-activation of intention representations still persisting in a heightened state of activation in episodic memory. In conclusion, the results highlight the functional relevance of VPC and precuneus in prospective memory retrieval, possibly reflecting spontaneous, cue-based processes as opposed to top-down controlled strategic monitoring.

Psychophysiology of prospective memory

Prospective memory involves the self-initiated retrieval of an intention upon an appropriate retrieval cue. Cue identification can be considered as an orienting reaction and may thus trigger a psychophysiological response. Here we present two experiments in which skin conductance responses (SCRs) elicited by prospective memory cues were compared to SCRs elicited by aversive stimuli to test whether a single prospective memory cue triggers a similar SCR as an aversive stimulus. In Experiment 2 we also assessed whether cue specificity had a differential influence on prospective memory performance and on SCRs. We found that detecting a single prospective memory cue is as likely to elicit a SCR as an aversive stimulus. Missed prospective memory cues also elicited SCRs. On a behavioural level, specific intentions led to better prospective memory performance. However, on a psychophysiological level specificity had no influence. More generally, the results indicate reliable SCRs for prospective memory cues and point to psychophysiological measures as valuable approach, which offers a new way to study one-off prospective memory tasks. Moreover, the findings are consistent with a theory that posits multiple prospective memory retrieval stages.

Prospective memory retrieval and autonomic activities: Mental tension and interoceptive awareness

Prospective memory retrieval and autonomic activities: Mental tension and interoceptive awareness

Discrepancy-plus-search processes in prospective memory retrieval

In the present study, we investigated the processes underlying prospective memory (PM) retrieval, focusing specifically on two possible spontaneous processes: discrepancy-plus-search and familiarity. Discrepancy was elicited by orthogonally manipulating the processing difficulties of the PM targets and the nontargets. Participants performed a PM task while solving anagrams with two levels of difficulty (easy or difficult). Assuming that the ease of processing easy anagrams would heighten a sense of familiarity, the familiarity view predicted better PM performance with easy anagrams as the PM targets. In contrast, the discrepancy-plus-search view predicted higher PM performance for the PM targets that were anagrams whose difficulty level mismatched that of the surrounding nontargets, as compared to PM targets whose difficulty matched that of the surrounding nontargets. This prediction was based on the idea that mismatching rather than matching difficulty levels would create discrepancy, thereby signaling significance for the target. Participants were more likely to perform the PM task for PM targets that were discrepant, supporting the discrepancy-plus-search view.

Age-related differences in the temporal dynamics of prospective memory retrieval: A lifespan approach

The efficiency of prospective memory (PM) typically increases from childhood to young adulthood and then decreases in later adulthood. The current study used event-related brain potentials (ERPs) to examine the development of the neural correlates of processes associated with the detection of a PM cue, switching from the ongoing activity to the prospective task, retrieval of the intention from memory or task set configuration, and strategic monitoring of the environment. The study included 99 participants that were 7.5–83 years of age. Slow wave activity related to strategic monitoring was reliable across the lifespan suggesting that all ages were able to allocate attentional resources to facilitate PM. Additionally, components of the ERPs related to cue detection, switching, and task configuration were reliable across the lifespan, suggesting that similar processes contribute to PM at all ages. In children, PM errors may have resulted from a decoupling of processes supporting cue detection and switching from the ongoing activity to the prospective element of the task. In younger and older adults, PM errors appeared to result from the failure to detect PM cues in the environment. These findings lead to the conclusion that different processes may contribute to variation in PM across the lifespan.

The role of rehearsals in self‐generated prospective memory tasks

In order to inquire into the nature of retrieval in prospective memory in a naturalistic context, we investigated the number and circumstances of rehearsals of different kinds of intentions to be pursued during a single time period. Thirty-six students were given four minutes to generate a list of tasks they were planning to perform over the course of 10 days. During this retention interval, they were provided with pocket-size diaries in which they recorded the details of each occasion they thought about the tasks previously listed. As to the nature of any triggers or cues that prompted rehearsal, the participants were asked to choose one of three alternatives: (1) association with an internal or an external cue that accidently appeared in the surroundings (accidental rehearsals), (2) deliberate thinking, e.g. while planning (self-initiated rehearsals), (3) recollection that spontaneously popped into one's mind for no apparent reason (no-trigger rehearsals). The results showed that thoughts about intended actions appeared more often after accidental cues than for no apparent reason. However, the relative contribution of self-initiated triggers to the rehearsal process was substantial: Most importantly, it was the self-initiated rehearsal that differentiated between executed and unexecuted actions. In addition, the most activated intention resulted in a higher frequency of no-trigger and self-initiated rehearsals than the remaining intentions. Finally, perceived intention importance was positively related to both the number of rehearsals and the likelihood of successful task completion. The results are discussed with regard to which factors may be crucial for the successful performance of participants' own self-generated intentions in a natural setting. The role of deliberate rehearsal in specifying the details of the intended action and its designated retrieval context is highlighted.

Ongoing task delays affect prospective memory more powerfully than filler task delays.

The effect of delay on prospective memory (PM) is mixed. Research has typically shown that PM either decreases or remains unchanged as the time increases between intention formation and encounter with a PM cue. However, the results of one study demonstrated that PM sometimes increases with increasing delays (Hicks, Marsh, & Russell, 2000). Hicks et al. hypothesised that increasing the delay may afford an opportunity for people to spontaneously rehearse the intention, or to be reminded of the intention. In the present work, we tested delays of 6 minutes, 21 minutes, and 36 minutes. Two factors were orthogonally manipulated between-subjects. One was the duration of the filler task that came between intention formation and the beginning of the ongoing task in which PM cues were embedded. The second was the duration of the ongoing task prior to the presentation of the first PM cue. Lengthening the ongoing task delay decreased PM. However, lengthening the filler task nominally increased PM. These results suggest that delays within the ongoing task replicate the effects traditionally found in retrospective memory work. In contrast, delays between intention formation and the beginning of the ongoing task may not have straightforward effects on PM retrieval.

Performance predictions improve prospective memory and influence retrieval experience.

In retrospective memory, performance predictions have been found to enhance performance on subsequent memory tests. In prospective memory, the influence of metacognitive judgments on performance has not been investigated systematically. In the present study, 140 undergraduate students performed a complex short-term memory task that included a prospective memory task. Half of them gave performance predictions after the prospective memory task instructions. In addition, the specificity of the prospective memory task was manipulated by instructing participants either to perform an action when a word that belongs to the category of musical instruments was presented or to respond when the word "trumpet" was presented. The results showed that performance predictions enhanced performance, but only for the categorical task. Additional analyses of retrieval experience showed that performance predictions lead to an increase in search experiences while cue specificity was accompanied by an increase in pop up experiences. The results indicate that performance predictions can improve prospective performance and thus may be a valuable strategy for assisting prospective memory.