Prospective Memory Impairment Research Articles

Impairments in prospective and retrospective memory following stroke

Prospective memory (PM) is the ability to carry out a planned intention at a future time. We studied PM deficits in a group of community-dwelling stroke survivors compared with normal controls. Twelve stroke patients and 12 matched controls performed a series of tests assessing executive function, prospective (PM) and retrospective memory (RM). Patients performed less well than controls on laboratory measures of PM and associative RM; they also showed deficits on standard tests of RM and executive control. The groups did not differ on more structured clinical measures of executive function, RM, PM or self-rated PM and RM. The results are discussed in terms of an impairment in the ability to ‘self-initiate’ effortful cognitive processes.

Incentive effects on event-based prospective memory performance in children and adolescents with traumatic brain injury.

Prospective memory (PM) is the formation of an intention and remembering to perform this intention at a future time or in response to specific cues. PM tasks are a ubiquitous part of daily life. Currently, there is a paucity of information regarding PM impairments in children with traumatic brain injury (TBI) and less empirical evidence regarding effective remediation strategies to mitigate these impairments. The present study employed two levels of a motivational enhancement (i.e., a monetary incentive) to determine whether event-based PM could be improved in children with severe TBI. In a crossover design, children with orthopedic injuries and mild or severe TBI were compared on two levels of incentive (dollars vs. pennies) given in response to accurate performance. All three groups performed significantly better under the high- versus low-motivation conditions. However, the severe TBI group's high-motivation condition performance remained significantly below the low-motivation condition performance of the orthopedic injury group. PM scores were positively and significantly related to age-at-test, but there were no age-at-injury or time-postinjury effects. Overall, these results suggest that event-based PM can be significantly improved in children with severe TBI.

Timing is everything: antiretroviral nonadherence is associated with impairment in time-based prospective memory.

Nonadherence to combination antiretroviral (ARV) therapies (cART) is highly prevalent and significantly increases the risk of adverse human immunodeficiency virus (HIV) disease outcomes. The current study evaluated the hypothesis that prospective memory-a dissociable aspect of episodic memory describing the ability to execute a future intention-plays an important role in successful cART adherence. Seventy-nine individuals with HIV infection who were prescribed at least one ARV medication underwent a comprehensive neuropsychological and neuromedical evaluation prior to completing a 1-month observation of their cART adherence as measured by electronic medication monitoring. Nonadherent individuals (n = 31) demonstrated significantly poorer prospective memory functioning as compared to adherent persons (n = 48), particularly on an index of time-based ProM (i.e., elevated loss of time errors). Deficits in time-based prospective memory were independently predictive of cART nonadherence, even after considering the possible influence of established predictors of adherence, such as general cognitive impairment (e.g., retrospective learning and memory) and psychiatric comorbidity (e.g., depression). These findings extend a nascent literature showing that impairment in time-based prospective memory significantly increases the risk of medication nonadherence and therefore may guide the development of novel strategies for intervention. (JINS, 2009, 15, 42-52.).

Involvement of Inferior Parietal Lobules in Prospective Memory Impairment during Acute MDMA (Ecstasy) Intoxication: An Event-Related fMRI Study

Prospective memory refers to the realization of delayed intentions. Several studies have shown that 3,4-methylenedioxy-methamphetamine (MDMA) users perform worse on measures of prospective memory as compared to nondrug users. Interpretation of these data may be limited because of polydrug use, psychosocial stressors, and increased psychopathology that have been reported in MDMA users. This study was designed to directly assess the pharmacological effect of MDMA on prospective memory and brain activity in a double-blind, placebo-controlled, cross-over study. Twelve recreational MDMA users received MDMA 75 mg and placebo and performed an objective prospective memory task during functional imaging. During prospective memory task performance subjects were engaged in a foreground task that consisted of a simple reaction time to visual stimuli (Go trials) and a prospective task of withholding a response during trials that were part of a dynamic memory set (No go trials). Behavioral data showed that a single dose of MDMA increased prospective memory failures in the No go trials, and that number of prospective memory failures was positively correlated to MDMA concentration in plasma. Functional imaging showed that MDMA decreased BOLD activation during Go trials in the thalamus (left), putamen (left), precuneus (left), and the inferior parietal lobules (bilateral), as compared to placebo. During No go trials, MDMA reduced BOLD deactivation in the inferior parietal lobules (bilateral), as compared to placebo. It is concluded that the loss of deactivation in inferior parietal lobules may account for increments in memory failures observed during MDMA intoxication.

Prospective memory impairment in former users of methamphetamine

Considerable research indicates that methamphetamine use is associated with neurocognitive impairment, but no empirical study to date has assessed whether these difficulties extend to memory for future intentions (prospective memory). The present study assessed prospective performance on a laboratory measure of prospective memory that closely represents the types of prospective memory tasks that actually occur in everyday life and provides an opportunity to investigate the different sorts of prospective memory failures that occur ("Virtual Week"). Twenty adults with confirmed history of methamphetamine use and dependence, currently engaged in rehabilitation and confirmed to be abstinent for an average period of 6 months, and 20 methamphetamine-naive participants were tested on Virtual Week. Various other aspects of cognitive function were also assessed, including retrospective memory and executive functioning. Methamphetamine users were significantly impaired on Virtual Week, and these deficits did not vary as a function of specific prospective memory task demands. Of all the cognitive measures, cognitive inhibition shared greatest variance with group effects on the prospective memory measure. Prospective memory performance is sensitive to prior methamphetamine use even well into abstinence. Methamphetamine users experience generalized difficulties with prospective memory, suggesting that these deficits are likely to have important implications for day-to-day functioning.

Prospective memory in schizophrenia: Further clarification of nature of impairment

Prospective memory (PM) refers to the ability to execute a delayed intention and is different from retrospective memory (RM) in its nature and underlying mechanism (e.g., intention formation, maintenance, detection of PM cue and intention execution). Although preliminary studies have found PM impairment in patients with schizophrenia, the nature and magnitude of this problem in this clinical group is not yet fully known. The current study aimed to further clarify the nature of this impairment in schizophrenia. Fifty-four patients with schizophrenia and fifty-four healthy volunteers matched on demographic variables, IQ and executive functions took part in the study. Time-, event-, and activity-based PM tasks and a set of neurocognitive tests were administered to the participants. Results showed that patients with schizophrenia performed significantly worse on all sub-types of PM tasks, even after controlling for neurocognitive functions such as working memory, verbal memory, visual memory, and executive function. These findings suggest PM deficit is a primary deficit rather than a secondary consequence of neurocognitive impairments in schizophrenia. Analysis found that PM deficits may be mainly due to the impairment of the cue detection and intention retrieval stage.

Prospective memory impairment in individuals with Parkinson's disease.

This study investigated prospective memory and its relationship to executive and memory functions in persons with Parkinson's disease (PD). Twenty-three individuals with PD and 25 healthy comparison participants participated in the study. In the prospective memory tasks, participants were asked to execute 3 actions after 20 min (time-based condition) or after a timer ring (event-based condition). A score was computed for the correct recall of the intention to perform the actions (prospective component) and for the correct execution of the actions (retrospective component). Participants with PD also received an extensive neuropsychological test battery. PD participants were less accurate than comparison participants in the prospective component of the time-based but not the event-based task. Individuals with PD were also impaired on the retrospective component of both tasks. In the PD group, a general trend toward significant correlations was found between performance level on the prospective memory component of the time-based task and scores on executive and working memory measures. These results document that prospective memory is impaired in PD possibly in relation to a dysregulation of cognitive functions associated with frontal systems.

HIV-associated prospective memory impairment increases risk of dependence in everyday functioning.

HIV infection is associated with impairments in prospective memory (ProM), an aspect of episodic memory that refers to the ability to execute a future intention, such as remembering to take a medication at a specific time. The current study sought to examine the relationship between HIV-associated ProM impairment and the successful management of instrumental activities of daily living (IADLs). In a cohort of 66 HIV-infected individuals, ProM accounted for a significant proportion of variance in self-reported IADL dependence, over and above that which was explained by retrospective memory and by current affective distress. Analysis of component cognitive processes revealed that the relationship between HIV-associated ProM deficits and IADL dependence was driven by impaired cue detection and by deficits in self-initiated intention retrieval. Results were not better explained by demographic factors, HIV disease severity, psychiatric comorbidity, or substance use. Collectively, these data support the potential incremental ecological validity of ProM as a predictor of dependence in IADLs among persons living with HIV infection.

Neuropsychological substrates and everyday functioning implications of prospective memory impairment in schizophrenia

Individuals with schizophrenia demonstrate impairment in prospective memory (ProM), which describes the multifaceted ability to execute a future intention. Despite its clear implications for everyday functioning, the neuropsychological substrates and functional correlates of ProM impairment in schizophrenia remain poorly understood. In this study, the Memory for Intentions Screening Test (MIST), a standardized measure of ProM, was administered to 72 outpatients with schizophrenia or schizoaffective disorder as part of a comprehensive neuropsychological and psychiatric research evaluation. Results showed that ProM was positively correlated with standard clinical tests of attention, working memory, processing speed, learning, and executive functioning, but not delayed recall. In the context of multiple neuropsychological predictors, learning ability was the only domain that independently contributed to ProM. Importantly, better ProM was predictive of higher functional capacity (as measured by the UCSD Performance-Based Skills Assessment-Brief Version), above and beyond the variability explained by demographic and disease factors. Analysis of component processes revealed that event-based ProM, as well as no response (i.e., omission) and task substitution errors were the strongest predictors of everyday functioning. Overall, these findings suggest that ProM impairment in schizophrenia is associated with multiple cognitive substrates, particularly episodic learning deficits, and plays an important role in everyday living skills. Studies regarding the potential effectiveness of ProM-based remediation strategies to improve functional outcomes in schizophrenia are indicated.

Prospective memory impairment in “ecstasy” (MDMA) users

Considerable research indicates that "ecstasy" users perceive their memory for future intentions (prospective memory) to be impaired. However, only one empirical study to date has directly tested how this capacity is affected by ecstasy use, and this study provided relatively limited information regarding the extent, scope, or implications of problems experienced. The present study assessed prospective performance on a laboratory measure of prospective memory that closely represents the types of prospective memory tasks that actually occur in everyday life and provides an opportunity to investigate the different sorts of prospective memory failures that occur ("Virtual Week"). Ecstasy user group (27 current users and 34 nonusers) was between participants, and prospective memory task (regular, irregular, time-check) was within participants. A measure sensitive to specific aspects of psychopathology was also administered. Ecstasy users were significantly impaired on Virtual Week, and these deficits were of a comparable magnitude irrespective of the specific prospective memory task demands. The pattern of results was unchanged after controlling for marijuana use, level of psychopathology, and sleep quality. Further, prospective memory was shown to be significantly impaired for both relatively infrequent and relatively frequent ecstasy users, although for the latter group the magnitude of this deficit was greater. Prospective memory performance is sensitive to regular and even moderate ecstasy use. Importantly, ecstasy users experience generalized difficulties with prospective memory, suggesting that these deficits are likely to have important implications for day-to-day functioning.

Sub-clinical checking compulsions are related to impaired prospective memory independently of depression, anxiety and distractibility

In this study, we explored whether relationships between checking compulsions and prospective memory are a result of the increased levels of distractibility, depression, state and trait anxiety associated with checking compulsions. Students ( N = 126) completed a prospective memory task and questionnaires which assess the frequency of experiencing prospective memory failures. Checking compulsions were associated with failing the prospective memory task and with self-reported prospective memory failures. Elevations in distractibility, depression, state and trait anxiety associated with checking compulsions had no influence on prospective memory task performance. They contributed to, but did not completely account for, the relationship between checking and self-reported prospective memory. The results support our theory that individuals with checking compulsions have an impaired prospective memory and that their increased experiences with prospective memory failures undermines their trust in the ability to perform tasks, ultimately resulting in intrusive doubts that specific tasks were not performed and the compulsion to check.

Impaired Strategic Monitoring as the Locus of a Focal Prospective Memory Deficit

In this study we examine the locus of a prospective memory deficit in an individual with multiple sclerosis. Extensive psychometric and neuropsychological testing revealed above average to superior general intelligence, retrospective and autobiographical memory, short-term/working memory and executive functions. In contrast, the individual demonstrated poor prospective memory on a variety of measures incorporating naturalistic, self-report, and laboratory methods. This deficit appeared to arise from a disruption of processes underlying strategic monitoring. These data clearly demonstrate that impaired prospective memory can exist in the presence of an otherwise intact neuropsychological profile.

Activity-Based Prospective Memory in Schizophrenia

The study reports activity-based prospective memory as well as its clinical and neuropsychological correlates in schizophrenia. A total of 42 persons diagnosed with schizophrenia and 42 healthy controls were administered prospective memory, set-shifting, and verbal working memory tasks. The schizophrenia group was additionally administered various psychopathology rating scales. Group differences, with poorer performances of the schizophrenia group, were observed on the measures of prospective memory, working memory, and set shifting. The performance on prospective memory tasks correlated with the performance levels on verbal working memory and set-shifting tasks but not with the clinical measures. This study demonstrated impaired activity-based prospective memory in schizophrenia. The impairment can be due to deficits in various neuropsychological domains.

Traumatic brain injury and prospective memory: Influence of task complexity

A quantitative review indicated that prospective memory impairment is a consistent feature of traumatic brain injury (TBI). However, evidence also suggests that manipulations that increase demands on controlled attentional processes moderate the magnitude of observed deficits. A total of 16 TBI participants were compared with 15 matched controls on a task in which the number of prospective target events was manipulated. This manipulation was of interest because two competing models make different predictions as to its effect on controlled attentional processes. In the context of Smith and Bayen's (2004) preparatory attentional processes and memory processes (PAM) model increasing the number of target events should increase requirements for controlled attentional processing. In contrast, McDaniel and Einstein's (2000) multiprocess framework assumes that distinct target events presented in focal awareness of the processing activities required for the ongoing task are likely to depend on automatic processes. This latter model therefore leads to the prediction that increasing the number of target events should not increase demands upon controlled attentional processes. Consistent with McDaniel and Einstein's (2000) multiprocess framework, TBI patients were significantly and comparably impaired on the one- and the four-target-event conditions relative to controls. Further, TBI deficits could not be attributed to increased difficulty with the retrospective component of the prospective memory task. The practical and theoretical implications of these results are discussed.

Prospective Memory and Pediatric Traumatic Brain Injury: Effects of Cognitive Demand

This study investigated the effects of pediatric traumatic brain injury (TBI) on prospective memory. Fourteen children and 14 adolescents with TBI were compared with 25 and 23 noninjured children and adolescents, respectively. Based on a prefrontal model, the cognitive demand on the ongoing component of a prospective-memory task was manipulated. Overall, those with TBI had poorer prospective-memory performance than their noninjured peers. Performance was worse in a high cognitive-demand condition than a low, and younger children performed worse than adolescents. Decreases in performance from the low- to high-demand conditions were not significantly different between the two children's groups but were between the two adolescents' groups. Furthermore, the age and injury effects were reflected in the performances on executive function tests: the Self-ordered Pointing Task (SOPT), and the Stroop Color Word Interference Test. The Tower of London (TOL), which did not produce age or injury effects, was nevertheless found to be an important predictor of performance on the high-demand task in those with TBI. Although previous research has demonstrated impaired prospective memory performance in children with TBI, this study attempted to explain why this might occur, specifically that the prefrontal regions might be implicated.

Deficits in cue detection and intention retrieval underlie prospective memory impairment in schizophrenia

Emerging evidence indicates that individuals with schizophrenia (SCZ) may exhibit deficits in prospective memory (ProM), a dissociable and ecologically important aspect of episodic memory entailing the formation, maintenance, and execution of future intentions. The present study aimed to elucidate the component processes of ProM impairment in 41 individuals with SCZ relative to 41 demographically similar healthy comparison (HC) participants. Results revealed that the SCZ group performed worse than HCs on overall ProM, with comparable deficits on time- and event-based ProM trials. In the SCZ cohort, better ProM performance was associated with younger age and less severe negative symptoms. Although a significantly greater number of Task Substitution and Loss of Time errors were evident in the SCZ group as compared to HCs, the most prevalent error type in SCZ was characterized by a complete failure to respond to the ProM cue. Importantly, the SCZ and HC groups did not differ on a post-test multiple-choice recognition trial, suggesting adequate formation and maintenance (i.e., retention) of the ProM cue-intention pairing when self-directed monitoring and retrieval demands were minimized. Findings indicate that SCZ is associated with impairment in the cue detection and self-initiated retrieval components of executing future intentions, which is consistent with a possible prefrontostriatal loop neuropathogenesis. Further studies are needed to explore the neurobiological mechanisms of SCZ-associated ProM impairment and the impact of such deficits on daily functioning (e.g., medication compliance).

Complex Prospective Memory in Children with ADHD

The ability to remember intentions (prospective memory) is fundamental to the organization of goal-directed actions in everyday life. Successful prospective remembering involves forming, retaining, initiating, and executing an intention. Although previous research has demonstrated prospective memory impairments in children with attention deficit/hyperactivity disorder (ADHD), this has largely focused on the intention initiation and execution stages. In this study, we investigate the performance of 20 children with ADHD and 20 matched controls at each of the four stages of prospective memory, using a computer multitask paradigm. Results suggest that children with ADHD may demonstrate difficulties forming delayed intentions, as indicated by impulsive planning, and that this may have further implications for the retention and implementation of these delayed intentions. While children with ADHD showed comparable multitask switching, this appeared to be at the expense of intention execution as they made more performance errors than controls. Implications for day-to-day functioning are discussed.

Sub-clinical compulsive checkers’ prospective memory is impaired

We explored whether prospective memory task performance is impaired in sub-clinical compulsive checkers. Participants were 126 undergraduate students who were divided into three groups: high, medium, low checkers. Participants completed two objective tests of their episodic prospective memory, one event- and one time-cued, as well as two questionnaires that measured their subjective prospective memory. The results indicated that medium and high checkers performed worse than low checkers on the objective event-cued prospective memory task but that the three groups performed similarly on the objective time-cued prospective memory task. Moreover, high checkers reported experiencing every type of prospective memory failure more frequently than either the medium or the low checkers. We suggest that individuals with compulsive checking tendencies have an impaired prospective memory and that their increased experiences with prospective memory failures causes their intrusive concerns that tasks were not completed.

Patterns of prospective and retrospective memory impairment in preclinical Alzheimer's disease.

Forty-six preclinical Alzheimer's disease (AD) participants and 188 nondemented control persons from the Kungsholmen Project (L. Bäckman et al., 2004) were compared on prospective memory (ProM) and retrospective memory (RetM) tasks 3 years before dementia diagnosis. The preclinical AD participants showed deficits in both ProM and RetM. Most interestingly, logistic regression analyses revealed that ProM made an independent contribution to the prediction of AD over and above that of RetM. This finding suggests that ProM and RetM tap partly different cognitive operations. Furthermore, within the ProM task, both the retrospective and prospective components were similarly impaired in preclinical AD. Within RetM, the preclinical AD participants were impaired on indices of encoding, storage (forgetting), and retrieval of information. Hence, the findings indicate a rather global episodic memory impairment in preclinical AD that cuts across type of memory assessed (ProM and RetM) as well as across different components of both the ProM and RetM tasks.

Diazepam-induced prospective memory impairment and its relation to retrospective memory, attention, and arousal

The amnestic effects of benzodiazepines are well documented on a variety of memory tasks. However, prospective memory (PM), or remembering to execute an action at a future time, has not been studied previously. This study examined the effect of diazepam on word list recall, PM, sustained attention, and subjective ratings of arousal. Forty-eight healthy participants, aged 19-35, received an average of 0.19 mg/kg oral diazepam or placebo in a double-blind manner. Retrospective memory and PM were assessed by free recall of unrelated word lists and by instructing participants to request a hidden belonging at the end of the session, respectively. Sustained attention was measured by multiple trials of a digit cancellation task, and subjective arousal was assessed by self-ratings of drowsiness. Diazepam impaired performance on all measures, including PM. Reduced PM performance was associated with decreased subjective arousal in the diazepam group but was unrelated to sustained attention. This is the first report of the effects of benzodiazepines on prospective remembering, and further supports the view that the arousal/attentional system is composed of partially independent subsystems that have differential relationships to memory.