Event-based Prospective Memory Research Articles

Time-based but not event-based prospective memory remains impaired one year after the onset of schizophrenia: A prospective study

BackgroundProspective memory (PM) deficits have been consistently found in people with schizophrenia. Although there is evidence to suggest that PM deficits may be putative markers for schizophrenia, no longitudinal study has investigated the persistence of PM deficits. AimsWe examined whether PM deficits persist after the onset of schizophrenia, and compared the trajectories of time- and event-based PM performance 12months after illness onset. We also examined whether the association between PM and clinical symptoms changes over time 12months after illness onset. MethodWe recruited 58 individuals with first-episode schizophrenia for a 12-month follow-up study. Comparison participants were 37 healthy individuals who were matched in terms of demographics and intelligence with the patient group. PM functions and clinical symptoms were measured at baseline, the sixth month, and the twelfth month, using a computerized PM task and the Positive and Negative Syndrome Scale. ResultsPeople with schizophrenia showed a gradual improvement in both time- and event-based PM 12months after illness onset. However, compared to event-based PM, deficit in time-based PM persisted and was relatively stable. At baseline, PM functions were not associated with clinical symptoms. However, an association between time-based PM and PANSS positive and general symptoms emerged 12months after the onset of schizophrenia. ConclusionPeople with first-episode schizophrenia exhibit persistent time-based PM deficit. Our findings support that PM deficit, in particular, time-based deficit, may be a putative neuropsychological marker of schizophrenia.

NEUROPSYCHOLOGICAL DOMAINS: OTHERA-95The Time- and Event-Based Prospective Memory in HIV Disease: Age Differences as a Function of Cue and Delay Interval

NEUROPSYCHOLOGICAL DOMAINS: OTHERA-95The Time- and Event-Based Prospective Memory in HIV Disease: Age Differences as a Function of Cue and Delay Interval

Spontaneous prospective-memory processing: Unexpected fluency experiences trigger erroneous intention executions

Event-based prospective memory is the ability to remember to execute an intention when an environmental cue occurs. It has been argued that, due to their special meaning, these cues are discrepant from their environment and therefore are sometimes spontaneously noticed. In line with this assumption, the likelihood that an intention will be executed increases with increased cue-discrepancy. It is not yet clear, however, whether these improvements are due to facilitated spontaneous noticing rather than to an increase in the efficiency of controlled cue-processing. To further investigate the spontaneous nature of cue-discrepancy benefits, we presented participants with stimuli that were unrelated to the intention but discrepant from other stimuli. Therefore, we experimentally increased the processing fluency of some stimuli for participants currently holding an intention by using different priming procedures. We found that stimuli whose fluency was increased via spaced repeated stimulus presentation (Experiment 1) or via short pre-exposure (Experiment 2a to 3) elicited a tendency to fulfill the intention despite its actual inappropriateness. Findings were inconsistent as to whether cue-memory uncertainty fosters the reliance on cue discrepancy for intention retrieval (Experiments 2a and 3). Taken together, the present findings provide converging evidence for a spontaneous discrepancy-based prospective-memory process which works independent of controlled processes.

Prospective memory and frontal lobe function

The study sought to examine the role of frontal lobe functioning in focal prospective memory (PM) performance and its relation to PM deficit in older adults. PM and working memory (WM) differences were studied in younger aged (n = 21), older aged (n = 20), and frontal injury (n = 14) groups. An event-based focal PM task was employed and three measures of WM were administered. The younger aged group differed from the other two groups in showing significantly higher scores on PM and on one of the WM measures, but there were no differences at a statistically significant level between the older aged group and the frontal injury groups on any of the memory measures. There were, however, some differences in correlations with a WM measure between groups. It is concluded that there are similarities and differences in the deficits in PM between older adults and patients with frontal lobe injury on focal as well as nonfocal PM tasks.

Event-based prospective memory in patients with Parkinson's disease: the effect of emotional valence.

The present study investigated the effect of Parkinson’s disease (PD) on prospective memory (PM) tasks by varying the emotional content of the PM actions. Twenty-one older adults with PD and 25 healthy older adults took part in the present study. Participants performed three virtual days in the Virtual Week task. On each virtual day, participants performed actions with positive, negative or neutral content. Immediately following each virtual day, participants completed a recognition task to assess their retrospective memory for the various PM tasks. PD patients were less accurate than the control group at both PM accuracy and recognition task accuracy. The effect of emotional valence was also evident, indicating that all participants were more accurate on positive PM tasks than both negative and neutral. This study confirmed PM impairment in PD patients and extended previous research showing how positive emotional stimuli can influence PM performance.

Prospective memory in subjective cognitive decline: a preliminary study on the role of early cognitive marker in dementia.

Accumulating evidence shows that subjective cognitive decline (SCD) without impairment on conventional neuropsychological tests may indicate increased risk for Alzheimer disease. Previous studies of mild cognitive impairment have demonstrated the potential role of prospective memory (PM) in the early detection of cognitive decline. We thus aimed to investigate the performance of people with SCD on PM tasks relative to their healthy controls (HCs). Forty-one participants with SCD and demographically matched HCs received regular cognitive testing as well as 2 single-trial naturalistic time-based and event-based PM tasks. Statistical analyses showed that the individuals with SCD performed worse on the time-based PM task, especially on the prospective component, when compared with their HCs. Our findings suggest that PM, especially the time-based one on the prospective component, may be an early cognitive marker of dementia. This implies an underlying difficulty among subjects with SCD in self-initiation that exacerbates their memory difficulties. Further investigation on a large scale is needed.

Forming implementation intentions improves prospective memory in early psychosis

The study examined whether individuals with early psychosis are impaired in prospective memory (PM), that is, remembering to execute a planned intention in the future, and whether implementation intentions can improve their PM performance. Thirty participants with early psychosis and 33 healthy controls were randomly allocated to either an implementation intentions or control condition and completed a computerised event-based PM task. Participants were also administered two standardised tests of PM and an abbreviated IQ test. Results demonstrated that individuals with early psychosis showed PM deficits relative to healthy controls on the computerised PM task and on some standardised measures of PM. The PM performance of the early psychosis group benefited from forming implementation intentions. Implementation intentions was concluded to be an effective strategy for improving PM performance in individuals with early psychosis.

The development of prospective memory across adolescence: an event-related potential analysis.

Prospective memory (PM) is an important cognitive function vital for day-to-day functioning. Although there has been extensive research into the decline of PM in older adulthood, little is known about its developmental trajectory throughout adolescence, a time of important brain maturation. In the present study, the development of PM was examined in 85 participants across the following groups: 12 to 13-year-olds (n = 19), 14 to 15-year-olds (n = 21), 16 to 17-year-olds (n = 19), and 18 to 19-year-olds (n = 26). A 30-cue (30 min) event-based PM task (with font-color stimuli as PM cues and a lexical-decision task as the ongoing task) was used while recording Event-Related Potentials (ERPs). The well-established neural correlates of PM, the N300 and parietal positivity, were examined across the age groups. In addition, hierarchical multiple regressions were used to examine the unique contribution of executive functioning measures (viz., the Self-Ordered Pointing Task [SOPT], the Stroop task, and Trail Making Test [TMT]) on the ERP components of PM (after controlling for age). First, the established components of ERPs associated with prospective remembering (i.e., N300 and parietal positivity) were detected for each age group. Second, although there were no significant age- group differences on the amplitude of the N300, the amplitude of the parietal positivity was found to be different between the 12 to 13-year-olds and 18 to 19-year-olds (viz., the 12 to 13-year-olds had the highest amplitude). Third, for the contribution of executive functioning measures on the amplitude of the ERP components of PM, the regression on the N300 was not significant, however, the SOPT beta weights were significant predictors of the amplitude of the parietal positivity. This relationship was found to be specific for the central and right electrode region. These findings are discussed within the context of brain development and executive functioning along with particular task demands, which may contribute to age-related PM differences across adolescence. Moreover, the findings suggest that cognitive processes associated with parietal positivity may continue to develop across adolescence.

The influence of mood on the process and content of encoding future intentions.

Remembering to perform an intention in the future when some environmental cue is encountered is referred to as event-based prospective memory. The influence of mood on this future-oriented memory is unclear. By experimentally manipulating mood, the current set of experiments sought to examine the influence that differing mood states have on encoding future intentions. Participants were induced into a neutral, positive, or negative mood state at intention formation and returned to their baseline mood before beginning the prospective memory task. Relative to the neutral mood, positive mood facilitated and negative mood impaired intention encoding when neutrally toned cues were used, as evidenced by the proportion of cues subsequently detected. The use of negatively toned cues ameliorated the benefit of the positive mood but not the impairment of the negative mood. Further, reinstatement of the encoding mood during retrieval equated performance for all three mood conditions. Results suggest that encoded mood influences the future accessibility and completion of intended behaviours, perhaps through modulation of associative processing. The current study demonstrates that mood plays a determining role in encoding future intentions.

Intermittent theta burst stimulation over left BA10 enhances virtual reality-based prospective memory in healthy aged subjects

Prospective memory (PM) refers to a complex cognitive ability that underpins the delayed execution of previously formulated intentions. PM performance declines early in normal aging and this process is accentuated in Alzheimer's disease. The left frontopolar cortex (BA10) has been consistently assigned a major role in PM functioning, but whether it can be noninvasively modulated to enhance PM performance in aged people has not been addressed so far. Here, we investigated the effects of modulating left BA10 by means of theta burst stimulation (TBS), using either excitatory (intermittent TBS), inhibitory (continuous TBS) or control (vertex) TBS in healthy aged subjects. The behavioral effects were assessed using a reliable and ecological virtual reality PM task that included both event- and time-based retrievals. As compared with vertex stimulation, event-based PM performance significantly improved after excitatory stimulation, whereas inhibitory stimulation had no significant effect. Additionally, and across the different types of stimulation, performance for congruent links between the event-based PM cue and the action to be performed was significantly better as compared with incongruent links. In conclusion, intermittent TBS might provide a relevant interventional strategy to counteract the decline of cognitive functions and memory abilities in normal aging.

Is Event-Based Prospective Memory Resistant to Proactive Interference?

Proactive interference builds up rapidly in recall with the presentation of successive lists comprising items from a single category (e.g., animals). In two experiments, we used a similar build-up paradigm in prospective memory. Interestingly, in Experiment 1, there was no evidence of proactive interference in prospective memory, although build-up emerged in a similar recall task. In Experiment 2, by also showing proactive interference build-up in a recognition task analogous to our prospective memory task, we ruled out the possibility that it was the recognition processes inherent in the prospective memory task that might make the task easier and prevent proactive interference. We suggest that, under normal conditions, prospective memory is resistant to build-up of proactive interference and propose that this resistance is a function of the strengthening afforded by a cue-to-intention association that is a part of prospective memory tasks. We discuss the finding using the classical paired-associate learning framework.

The effects of encoding modality and object presence on event-based prospective memory in seven- to nine-year-old children

To date, little work has been done to investigate event-based prospective memory in seven- to nine-year-old children, particularly with balancing the difficulty of the ongoing tasks across each age group. In this study, we tested 192 children (64 children in each age group) to explore this issue and examine the effects of encoding modality and object presence at encoding on prospective memory in seven- to nine-year-old children. The results highlighted three key aspects. First, the prospective memory performance of eight- and nine-year-old children was significantly better than that of seven-year-old children. Second, the combined group of eight- and nine-year-old children showed prospective memory improvement in enactment condition compared with verbal condition. Third, only seven-year-old children benefited from the presence of objects during the encoding stage. Finally, strategic issues of prospective memory will be discussed.

Slow down and remember to remember! A delay theory of prospective memory costs.

Event-based prospective memory (PM) requires a deferred action to be performed when a target event is encountered in the future. Individuals are often slower to perform a concurrent ongoing task when they have PM task requirements relative to performing the ongoing task in isolation. Theories differ in their detailed interpretations of this PM cost, but all assume that the PM task shares limited-capacity resources with the ongoing task. In what was interpreted as support of this core assumption, diffusion model fits reported by Boywitt and Rummel (2012) and Horn, Bayen, and Smith (2011) indicated that PM demands reduced the rate of accumulation of evidence about ongoing task choices. We revaluate this support by fitting both the diffusion and linear ballistic accumulator (Brown & Heathcote, 2008) models to these same data sets and 2 new data sets better suited to model fitting. There was little effect of PM demands on evidence accumulation rates, but PM demands consistently increased the evidence required for ongoing task response selection (response thresholds). A further analysis of data reported by Lourenço, White, and Maylor (2013) found that participants differentially adjusted their response thresholds to slow responses associated with stimuli potentially containing PM targets. These findings are consistent with a delay theory account of costs, which contends that individuals slow ongoing task responses to allow more time for PM response selection to occur. Our results call for a fundamental reevaluation of current capacity-sharing theories of PM cost that until now have dominated the PM literature.

Dissociation of event-based prospective memory and time-based prospective memory in patients with prostate cancer receiving androgen-deprivation therapy: a neuropsychological study.

The primary purpose of this study was to evaluate the event-based prospective memory (EBPM) and time-based prospective memory (TBPM) in androgen-deprivation therapy (ADT)-induced cognitive impairment in patients with prostate cancer (PC). Participants included PC patients who had undergone ADT (ADT group, n = 43) or patients who did not undergo ADT (non-ADT group, n = 35), as well as age and education-matched healthy controls (HC group, n = 40). All participants were administered with a battery of neuropsychological tests including EBPM and TBPM tasks. Our results indicated that during the EBPM task, the ADT group obtained significantly lower scores than the non-ADT and HC group did, while no significant differences in the TBPM task scores were found among these three groups. Additionally, the ADT group demonstrated significantly lower scores in several cognitive tasks, including attention, memory, and information processing, when compared with the other two groups. This study demonstrated that PC patients receiving ADT may have selective reductions in EBPM performance but unimpaired TBPM performance and that these deficits may result from the changes of function and structure of the pre-frontal cortex induced by ADT.

Valenced cues and contexts have different effects on event-based prospective memory.

This study examined the separate influence and joint influences on event-based prospective memory task performance due to the valence of cues and the valence of contexts. We manipulated the valence of cues and contexts with pictures from the International Affective Picture System. The participants, undergraduate students, showed higher performance when neutral compared to valenced pictures were used for cueing prospective memory. In addition, neutral pictures were more effective as cues when they occurred in a valenced context than in the context of neutral pictures, but the effectiveness of valenced cues did not vary across contexts that differed in valence. The finding of an interaction between cue and context valence indicates that their respective influence on event-based prospective memory task performance cannot be understood in isolation from each other. Our findings are not consistent with by the prevailing view which holds that the scope of attention is broadened and narrowed, respectively, by positively and negatively valenced stimuli. Instead, our findings are more supportive of the recent proposal that the scope of attention is determined by the motivational intensity associated with valenced stimuli. Consistent with this proposal, we speculate that the motivational intensity associated with different retrieval cues determines the scope of attention, that contexts with different valence values determine participants’ task engagement, and that prospective memory task performance is determined jointly by attention scope and task engagement.

Modeling criterion shifts and target checking in prospective memory monitoring.

Event-based prospective memory (PM) involves remembering to perform intended actions after a delay. An important theoretical issue is whether and how people monitor the environment to execute an intended action when a target event occurs. Performing a PM task often increases the latencies in ongoing tasks. However, little is known about the reasons for this cost effect. This study uses diffusion model analysis to decompose monitoring processes in the PM paradigm. Across 4 experiments, performing a PM task increased latencies in an ongoing lexical decision task. A large portion of this effect was explained by consistent increases in boundary separation; additional increases in nondecision time emerged in a nonfocal PM task and explained variance in PM performance (Experiment 1), likely reflecting a target-checking strategy before and after the ongoing decision (Experiment 2). However, we found that possible target-checking strategies may depend on task characteristics. That is, instructional emphasis on the importance of ongoing decisions (Experiment 3) or the use of focal targets (Experiment 4) eliminated the contribution of nondecision time to the cost of PM, but left participants in a mode of increased cautiousness. The modeling thus sheds new light on the cost effect seen in many PM studies and suggests that people approach ongoing activities more cautiously when they need to remember an intended action.

Problems in remembering to carry out future actions in first-episode schizophrenia: Primary or secondary impairment?

Prospective memory (PM) is the ability to remember to carry out intended actions in the future. Empirical evidence suggests that PM deficits exist in individuals with chronic schizophrenia. However, it is unclear whether PM deficits in first-episode schizophrenia exist independently from other neuropsychological deficits. Moreover, prior research using patients with first-episode has been limited to small inpatient samples. We aimed to clarify the nature and extent of PM deficits in individuals with first-episode schizophrenia, using a large outpatient sample. Participants were 91 clinically stable outpatients with first-episode schizophrenia and 83 healthy controls. PM was assessed using both a subjective self-reported checklist and a laboratory-based task capturing time- and event-based PM. A battery assessing verbal and visuo-spatial working memory, as well as executive functions was also administered. ANOVA analyses showed that patients with first-episode schizophrenia performed significantly poorer than healthy controls in time- and event-based PM. Stepwise linear regression analyses suggested that cognitive flexibility predicted time- and event-based PM; and working memory predicted event-based PM. Subgroup analyses showed that “cognitive-preserved” patients with first-episode schizophrenia tended to perform poorer in time-based PM deficit than healthy controls who were matched in IQ and other neuropsychological functions. Overall, our results provide substantial evidence to support that time-based PM deficits in first-episode schizophrenia are apparent and not entirely attributable to other neuropsychological deficits. PM may constitute a neuropsychological marker for schizophrenia.

Implementation intentions forge a strong cue–response link and boost prospective memory performance

Prospective memory (PM) performance (i.e., remembering to perform intentions) is often in the service of higher goals and thus could be improved through better self-regulation. We examined the effectiveness of three self-regulatory strategies in a laboratory event-based PM task: implementation intention (i.e., planning in an if/when–then format), rehearsal (i.e., planning not in an if/when–then format) and upward counterfactual (“if only…” thoughts about a past performance). The cue and response mentioned in all three strategies were held constant, such that only format and timing (past vs. future orientation) of the strategy varied. Results indicated that the implementation intention strategy strengthened the cue–response link and improved PM performance over baseline, relative to a control condition. Neither rehearsal nor counterfactual strategies had significant benefits, relative to a control condition. These findings suggest that the if/when–then plan format of implementation intentions may be a critical feature of their effectiveness in retrieving and executing intentions.

The relationship between event-based prospective memory and ongoing task performance in chimpanzees (Pan troglodytes).

Prospective memory is remembering to do something at a future time. A growing body of research supports that prospective memory may exist in nonhuman animals, but the methods used to test nonhuman prospective memory differ from those used with humans. The current work tests prospective memory in chimpanzees using a method that closely approximates a typical human paradigm. In these experiments, the prospective memory cue was embedded within an ongoing task. Tokens representing food items could be used in one of two ways: in a matching task with pictures of items (the ongoing task) or to request a food item hidden in a different location at the beginning of the trial. Chimpanzees had to disengage from the ongoing task in order to use the appropriate token to obtain a higher preference food item. In Experiment 1, chimpanzees effectively matched tokens to pictures, when appropriate, and disengaged from the ongoing task when the token matched the hidden item. In Experiment 2, performance did not differ when the target item was either hidden or visible. This suggested no effect of cognitive load on either the prospective memory task or the ongoing task, but performance was near ceiling, which may have contributed to this outcome. In Experiment 3, we created a more challenging version of the task. More errors on the matching task occurred before the prospective memory had been carried out, and this difference seemed to be limited to the hidden condition. This finding parallels results from human studies and suggests that working memory load and prospective memory may have a similar relationship in nonhuman primates.

Prospective memory performance in non-psychotic first-degree relatives of patients with schizophrenia: a controlled study.

ObjectiveWe aimed at investigating prospective memory and its socio-demographic and neurocognitive correlates in non-psychotic, first-degree relatives (FDRs) of patients with schizophrenia compared to patients with first episode schizophrenia (FES), and healthy controls (HCs).MethodsForty-seven FES patients, 50 non-psychotic FDRs (23 offspring and 27 siblings) of patients with chronic schizophrenia (unrelated to the FES group) and 51 HCs were studied. The Chinese version of the Cambridge Prospective Memory Test (C-CAMPROMPT) was used to measure time-based prospective memory (TBPM) and event-based prospective memory (EBPM) performance. Other cognitive functions (involving respective memory and executive functions) were evaluated with standardized tests.ResultsAfter controlling for basic demographic characteristics including age, gender and educational level, there was a significant difference between FDRs, FES and HCs with respect to both TBPM (F(2,142) = 10.4, p<0.001) and EBPM (F(2,142) = 10.8, p<0.001). Multiple linear regression analyses revealed that lower scores of the Hopkins Verbal Learning Test-Revised (HVLT-R) and the STROOP Word-Color Test (SWCT) contributed to TBPM impairment, while lower educational level and higher scores of the Color Trails Test-2 (CTT-2) contributed to EBPM deficit in FDRs.ConclusionsFDRs share similar but attenuated prospective memory impairments with schizophrenia patients, suggesting that prospective memory deficits may represent an endophenotype of schizophrenia.