Prospective Memory Impairment in Mild Cognitive Impairment: An Analytical Review

Mild cognitive impairment (MCI) is a heterogeneous condition characterized by the presence in an otherwise healthy elderly individual of cognitive deficits involving specific domains in the absence of significant functional impairments. Reports indicate that prospective memory (PM), that is, the ability to remember to execute delayed intentions, is impaired in individuals with MCI. The present review discusses the current debate in the literature on PM functioning in MCI by focusing on the relationship between prospective retrieval and retrospective memory functioning. Analysis of the reported evidence revealed that both the prospective component and the retrospective component of PM can be impaired in MCI. Declarative memory dysfunction may account for the retrospective memory impairment, while either reduced executive abilities or a deficit of reflexive mechanisms could explain the prospective component impairment.     

Age, Focal Processing, and Monitoring in Event-Based Prospective Memory

While there is some consensus that prospective memory (PM) declines with age, the reasons for differences in performance across age groups are not fully understood. This experiment examines two factors that are likely to affect the magnitude of observed age group differences: type of PM task and whether participants monitor the task environment for the opportunity to complete the PM task. Younger and older adults were engaged in an ongoing test of short-term memory and were asked to perform one of two different event-based PM tasks. Younger adults performed better than older adults on both focal and nonfocal PM tasks. In addition, younger adults were able to perform both types of tasks equally well, but older adults were more successful on the focal task than on the nonfocal task. Age group differences in self-reported PM monitoring were also evident and were related to performance. These findings and their implications for current theoretical conceptions of PM aging are discussed.     

Planning and realization of complex intentions in traumatic brain injury and normal aging

The realization of delayed intentions (i.e., prospective memory) is a highly complex process composed of four phases: intention formation, retention, re-instantiation, and execution. The aim of this study was to investigate if executive functioning impairments are related to problems in the formation, re-instantiation, and execution of a delayed complex intention. In this context, it was another aim of the study to investigate the executive functioning hypothesis of cognitive aging in prospective memory performance. It was, therefore, explored if age-related prospective memory decline leads to similar decrements in the process of prospective remembering as executive functioning-related decline in young patients with traumatic brain injury. A group of patients with traumatic brain injury with retrospective memory within normal limits but impaired executive functions, a group of healthy older and a group of healthy younger adults completed a complex prospective memory task that allows for the separate assessment of the four phases of the prospective memory process. All groups showed a similarly high performance in the intention retention phase, whereas the patients with deficits in executive functioning and the older participants performed worse than the healthy young participants in the intention formation, re-instantiation and execution phases. The importance of executive functioning for prospective remembering in traumatic brain injury and normal aging is discussed.     

Prior task experience and comparable stimulus exposure nullify focal and nonfocal prospective memory retrieval differences

We explored the nature of focal versus nonfocal event-based prospective memory retrieval. In the context of a lexical decision task, people received an intention to respond to a single word (focal) in one condition and to a category label (nonfocal) for the other condition. Participants experienced both conditions, and their order was manipulated. The focal instruction condition was a single word presented multiple times. In Experiment 1, the stimuli in the nonfocal condition were different exemplars from a category, each presented once. In the nonfocal condition retrieval was poorer and reaction times were slower during the ongoing task as compared to the focal condition, replicating prior findings. In Experiment 2, the stimulus in the nonfocal condition was a single category exemplar repeated multiple times. When this single-exemplar nonfocal condition followed in time the single-item focal condition, focal versus nonfocal performance was virtually indistinguishable. These results demonstrate that people can modify their stimulus processing and expectations in event-based prospective memory tasks based on experience with the nature of prospective cues and with the ongoing task.     

Individual differences in event-based prospective memory: Evidence for multiple processes supporting cue detection

The multiprocess view proposes that different processes can be used to detect event-based prospective memory cues, depending in part on the specificity of the cue. According to this theory, attentional processes are not necessary to detect focal cues, whereas detection of nonfocal cues requires some form of controlled attention. This notion was tested using a design in which we compared performance on a focal and on a nonfocal prospective memory task by participants with high or low working memory capacity. An interaction was found, such that participants with high and low working memory performed equally well on the focal task, whereas the participants with high working memory performed significantly better on the nonfocal task than did their counterparts with low working memory. Thus, controlled attention was only necessary for detecting event-based prospective memory cues in the nonfocal task. These results have implications for theories of prospective memory, the processes necessary for cue detection, and the successful fulfillment of intentions.     

Too exhausted to remember: Ego depletion undermines subsequent event‐based prospective memory

Past research has consistently found that people are likely to do worse on high‐level cognitive tasks after exerting self‐control on previous actions. However, little has been unraveled about to what extent ego depletion affects subsequent prospective memory. Drawing upon the self‐control strength model and the relationship between self‐control resources and executive control, this study proposes that the initial actions of self‐control may undermine subsequent event‐based prospective memory (EBPM). Ego depletion was manipulated through watching a video requiring visual attention (Experiment 1) or completing an incongruent Stroop task (Experiment 2). Participants were then tested on EBPM embedded in an ongoing task. As predicted, the results showed that after ruling out possible intervening variables (e.g. mood, focal and nonfocal cues, and characteristics of ongoing task and ego depletion task), participants in the high‐depletion condition performed significantly worse on EBPM than those in the low‐depletion condition. The results suggested that the effect of ego depletion on EBPM was mainly due to an impaired prospective component rather than to a retrospective component.     

Enhanced recognition of words previously presented in a task with nonfocal prospective memory requirements

Remembering to perform deferred actions when events are encountered in the future is referred to as event-based prospective memory. Individuals can be slower to respond to ongoing tasks when they have prospective memory task requirements. These costs are interpreted as evidence for cognitive control processes allocated to the prospective memory task, but we know little about these processes. In the present article, the recognition of nontargets previously presented in an ongoing task with prospective memory task requirements provided evidence for the differential processing of individual ongoing task items. Participants performed a lexical decision task, where some participants were required to make an alternative prospective memory response either to a specific word (focal) or to exemplars of a category (nonfocal). Participants were slower to respond to the ongoing task in the nonfocal conditions than in the control condition (costs), regardless of whether or not prospective memory task importance was emphasized. Participants were also slower to respond to the ongoing task in the focal conditions than in the control condition, but only when prospective memory task importance was emphasized. This task was followed by a surprise recognition memory test in which nontarget words from the lexical decision task were intermixed with new words. Focal conditions, but not nonfocal conditions, showed better discrimination on the recognition task, as compared with the control condition. Participants in nonfocal conditions mapped the semantic features of the ongoing task letter strings onto the semantic features of their prospective memory category, and this elaboration in the processing of individual nontargets increased incidental learning and produced the recognition benefit.     

Association of television violence exposure with executive functioning and white matter volume in young adult males

Prior research has indicated that self-reported violent media exposure is associated with poorer performance on some neuropsychological tests in adolescents. This study aimed to examine the relationship of executive functioning to violent television viewing in healthy young adult males and examine how brain structure is associated with media exposure measures. Sixty-five healthy adult males (ages 18–29) with minimal video game experience estimated their television viewing habits over the past year and, during the subsequent week, recorded television viewing time and characteristics in a daily media diary. Participants then completed a battery of neuropsychological laboratory tests quantifying executive functions and underwent a magnetic resonance imaging (MRI) scan. Aggregate measures of executive functioning were not associated with measures of overall television viewing (any content type) during the past week or year. However, the amount of television viewing of violent content only, as indicated by both past-year and daily diary measures, was associated with poorer scores on an aggregate score of inhibition, interference control and attention, with no relationship to a composite working memory score. In addition, violent television exposure, as measured with daily media diaries, was associated with reduced frontoparietal white matter volume. Future longitudinal work is necessary to resolve whether individuals with poor executive function and slower white matter growth are more drawn to violent programming, or if extensive media violence exposure modifies cognitive control mechanisms mediated primarily via prefrontal cortex. Impaired inhibitory mechanisms may be related to reported increases in aggression with higher media violence exposure.     

Prospective memory and intraindividual variability in ongoing task response times in an adult lifespan sample: the role of cue focality

To contribute to the ongoing conceptual debate of what traditional mean-level ongoing task (OT) costs tell us about the attentional processes underlying prospective memory (PM), we investigated costs to intraindividual variability (IIV) in OT response times as a potentially sensitive indicator of attentional processes. Particularly, we tested whether IIV in OT responses may reflect controlled employment of attentional processes versus lapses of controlled attention, whether these processes differ across adulthood, and whether it is moderated by cue focality. We assessed 150 individuals (19–82 years) in a focal and a nonfocal PM condition. In addition, external measures of inhibition and working memory were assessed. In line with the predictions of the lapses-of-attention/inefficient-executive-control account, our data support the view that costs to IIV in OT trials of PM tasks reflect fluctuations in the efficiency of executive functioning, which was related to failures in prospective remembering, particularly in nonfocal PM tasks, potentially due to their increased executive demands. The additional value of considering costs to IIV over and beyond traditional mean-level OT costs in PM research is discussed.     

Adult age differences in event-based prospective memory: a meta-analysis on the role of focal versus nonfocal cues

Studies of age differences in event-based prospective memory indicate wide variation in the magnitude of age effects. One explanation derived from the multiprocess framework proposes that age differences depend on whether the cue to carry out a prospective intention is focal to ongoing task processing. A meta-analysis of 117 effect sizes from 4,709 participants provided evidence for this view, as age effects were greater when the prospective cue to the ongoing task was nonfocal compared with when it was focal. However, the results only support a weaker but not a stronger prediction of the multiprocess framework, as age impairments were reliably above zero for both types of retrieval cues.     

The transient nature of executive control processes in younger and older adults

In this paper I review data from recent studies supporting the hypothesis that executive control processes fluctuate in efficiency over time and that these fluctuations are more pervasive in older than younger adults. Patterns of response accuracy in tasks requiring selective attention and prospective memory reveal that lapses of intention are often preceded and followed by periods of goal-directed action. Analysis of response time distributions reveals that increased performance variability in older adults for task conditions requiring executive control results from an increase in the degree of positive skewing of the distribution. Together, these findings lead to the suggestion that disruptions of executive control processes supporting performance in demanding tasks are temporally limited in nature. Data from recent neurophysiological studies indicates a possible role of the prefrontal cortex in maintaining optimal levels of executive control.     

Differential brain shrinkage over 6 months shows limited association with cognitive practice

The brain shrinks with age, but the timing of this process and the extent of its malleability are unclear. We measured changes in regional brain volumes in younger (age 20–31) and older (age 65–80) adults twice over a 6 months period, and examined the association between changes in volume, history of hypertension, and cognitive training. Between two MRI scans, 49 participants underwent intensive practice in three cognitive domains for 100 consecutive days, whereas 23 control group members performed no laboratory cognitive tasks. Regional volumes of seven brain structures were measured manually and adjusted for intracranial volume. We observed significant mean shrinkage in the lateral prefrontal cortex, the hippocampus, the caudate nucleus, and the cerebellum, but no reliable mean change of the prefrontal white matter, orbital-frontal cortex, and the primary visual cortex. Individual differences in change were reliable in all regions. History of hypertension was associated with greater cerebellar shrinkage. The cerebellum was the only region in which significantly reduced shrinkage was apparent in the experimental group after completion of cognitive training. Thus, in healthy adults, differential brain shrinkage can be observed in a narrow time window, vascular risk may aggravate it, and intensive cognitive activity may have a limited effect on it.     

Sleep disruption explains age-related prospective memory deficits: implications for cognitive aging and intervention

The high prevalence of sleep disruption among older adults may have implications for cognitive aging, particularly for higher-order aspects of cognition. One domain where sleep disruption may contribute to age-related deficits is prospective memory—the ability to remember to perform deferred actions at the appropriate time in the future. Community-dwelling older adults (55–93 years, N = 133) undertook assessment of sleep using actigraphy and participated in a laboratory-based prospective memory task. After controlling for education, sleep disruption (longer awakenings) was associated with poorer prospective memory. Additionally, longer awakenings mediated the relationship between older age and poorer prospective memory. Other metrics of sleep disruption, including sleep efficiency and wake after sleep onset, were not related to prospective memory, suggesting that examining the features of individual wake episodes rather than total wake time may help clarify relationships between sleep and cognition. The mediating role of awakening length was partially a function of greater depression and poorer executive function (shifting) but not retrospective memory. This study is among the first to examine the association between objectively measured sleep and prospective memory in older adults. Furthermore, this study is novel in suggesting sleep disruption might contribute to age-related prospective memory deficits; perhaps, with implications for cognitive aging more broadly. Our results suggest that there may be opportunities to prevent prospective memory decline by treating sleep problems.     

A bilingual advantage for episodic memory in older adults

The ability to remember events—referred to as episodic memory—is typically subject to decline in older adulthood. Episodic memory decline has been attributed in part to less successful executive functioning, which may hinder an older adult's ability to implement controlled encoding and retrieval processes. Since bilingual older adults often show more successful executive functioning than monolinguals, they may be better able to maintain episodic memory. To examine this hypothesis, we compared bilingual and monolingual older adults on a picture scene recall task (assessing episodic memory) and a Simon task (assessing executive functioning). Bilinguals exhibited better episodic memory than their monolingual peers, recalling significantly more items overall. Within the bilingual group, earlier second language acquisition and more years speaking two languages were associated with better recall. Bilinguals also demonstrated higher executive functioning, and there was evidence that level of executive functioning was related to memory performance. Results indicate that extensive practice controlling two languages may benefit episodic memory in older adults.     

Acute pain disrupts prospective memory cue detection processes

Prospective memory refers to the planning, retention, retrieval, and execution of intentions for future behaviours and it is integral to the enterprise of daily living. Although prospective memory relies upon retrospective memory and executive processes often disrupted by pain, limited research has explored the influence of acute or chronic pain on the ability to complete prospective memory tasks. In the present study we investigated the influence of acute pain on prospective memory tasks that varied in their demands on executive processes (i.e., non-focal versus focal prospective memory cues). Complex-span working memory tasks were also administered to examine whether individual differences in working memory capacity moderated any negative impact of pain on prospective memory. Acute pain significantly impaired prospective memory performance in conditions that encouraged non-focal strategic processing of prospective memory cues, but not in conditions that encouraged more spontaneous focal processing. Individual differences in working memory capacity did not moderate the effect of acute pain on non-focal prospective memory. These findings provide new insights into prospective memory dysfunction created by painful experiences.     

Unfulfilled goals interfere with tasks that require executive functions

Even after one stops actively pursuing a goal, many mental processes remain focused on the goal (e.g., the Zeigarnik effect), potentially occupying limited attentional and working memory resources. Five studies examined whether the processes associated with unfulfilled goals would interfere with tasks that require the executive function, which has a limited focal capacity and can pursue only one goal at a time. In Studies  and , activating a goal nonconsciously and then manipulating unfulfillment caused impairments on later tasks requiring fluid intelligence (solving anagrams; Study 1) and impulse control (dieting; Study 2). Study 3 showed that impairments were specific to executive functioning tasks: an unfulfilled goal impaired performance on logic problems but not on a test of general knowledge (only the former requires executive functions). Study 4 found that the effect was moderated by individual differences; participants who reported a tendency to shift readily amongst their various pursuits showed no task interference. Study 5 found that returning to fulfill a previously frustrated goal eliminated the interference effect. These findings provide converging evidence that unfulfilled goals can interfere with later tasks, insofar as they require executive functions.     

Age-related effects in prospective memory are modulated by ongoing task complexity and relation to target cue

Two experiments examined the puzzling variation in the age-related patterns for event-based prospective memory tasks. Both experiments involved a famous faces ongoing task with a feature of the famous face as the target for the prospective memory task. In Experiment 1, a substantial age deficit was found on the prospective memory task when the cue was nonfocal (wearing glasses) to the ongoing task, replicating previous research, but this deficit was significantly reduced with a focal cue (first name John). In Experiment 2, the prospective memory cue (wearing glasses) was held constant and the demands of the ongoing task of naming faces were varied. The substantial age differences found with a nonfocal cue were eliminated when the ongoing task was made less challenging. The findings help reconcile the divergent age-related findings reported in the literature.     

线索聚焦性影响前瞻记忆意向维持与提取：来自眼动追踪的证据

研究以眼动追踪的方法探讨线索聚焦性对前瞻记忆(prospective memory, PM）加工过程的影响。实验1中,28名被试完成了线索聚焦和非聚焦两类PM眼动追踪任务。结果发现,个体在聚焦和非聚焦两类PM任务意向维持、意向提取阶段上均表现出不同的眼动加工特征。实验2中,研究进一步对线索聚焦和非聚焦两个PM任务中PM线索词重复次数进行平衡,并重复了实验1的研究结果,说明实验1所观测到的效应不是PM线索词重复造成的混淆,线索聚焦性影响PM的意向维持、意向提取过程,研究结果支持多重加工理论。     

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.     

Colour language and colour cognition: Brown and Lenneberg revisited

We report two experiments that revisit the question raised by Brown and Lenneberg (1954) concerning the degree to which colours that are easier to name are also easier to communicate and to remember. Much subsequent research has suggested that such effects depend on context and task demands. In the present experiments communication accuracy and recognition memory were compared, varying the distractor array for items that are either best examples (focal) of the eight basic chromatic categories named in English, or peripheral (nonfocal) examples of them. Focal targets were communicated faster, more accurately, and with fewer words than nonfocal targets, irrespective of array. However, they were not recognized more accurately under all conditions. With a randomized array of distractors, more akin to real scenes outside the lab, there was no recognition advantage for those colours that are easiest to code and communicate. We conclude that focal colours are not inherently more memorable.