The role of rostral prefrontal cortex in prospective memory: a voxel-based lesion study

Patients with lesions in rostral prefrontal cortex (PFC) often experience problems in everyday-life situations requiring multitasking. A key cognitive component that is critical in multitasking situations is prospective memory, defined as the ability to carry out an intended action after a delay period filled with unrelated activity. The few functional imaging studies investigating prospective memory have shown consistent activation in both medial and lateral rostral PFC but also in more posterior prefrontal regions and non-frontal regions. The aim of this study was to determine regions that are necessary for prospective memory performance, using the human lesion approach. We designed an experimental paradigm allowing us to assess time-based (remembering to do something at a particular time) and event-based (remembering to do something in a particular situation) prospective memory, using two types of material, words and pictures. Time estimation tasks and tasks controlling for basic attention, inhibition and multiple instructions processing were also administered. We examined brain-behaviour relationships with a voxelwise lesion method in 45 patients with focal brain lesions and 107 control subjects using this paradigm. The results showed that lesions in the right polar prefrontal region (in Brodmann area 10) were specifically associated with a deficit in time-based prospective memory tasks for both words and pictures. This deficit could not be explained by impairments in basic attention, detection, inhibition or multiple instruction processing, and there was also no deficit in event-based prospective memory conditions. In addition to their prospective memory difficulties, these polar prefrontal patients were significantly impaired in time estimation ability compared to other patients. The same region was found to be involved using both words and pictures, suggesting that right rostral PFC plays a material nonspecific role in prospective memory. This is the first lesion study showing that rostral PFC is crucial for time-based prospective memory. The findings suggest that time-based and event-based prospective memory might be supported at least in part by distinct brain regions. Two particularly plausible explanations for the deficit rest upon a possible role for polar prefrontal structures in supporting in time estimation, and/or in retrieving an intention to act. More broadly, the results are consistent with the view that the deficit of rostral patients in multitasking situations might at least in part be explained by a deficit in prospective memory.

Time-Based Prospective Memory in Schoolchildren

The present study examined age differences in time-based prospective memory (TBPM) in primary school age children and tested the role of self-initiated memory retrieval and strategic time monitoring (TM) as possible developmental mechanisms. Fifty-four children were recruited from local primary schools (27 younger children, mean age = 7.2 ± 0.55 years, and 27 older children, mean age = 9.61 ± 0.71 years). The task was a driving game scenario in which children had to drive a vehicle (ongoing task) and to remember to refuel before the vehicle runs out of gas (TBPM task, i.e., the fuel gauge served as child-appropriate time equivalent). Fuel gauge was either displayed permanently (low level of self-initiation) or could only be viewed on demand by hitting a button (high level of self-initiation). The results revealed age-dependent TBPM differences with better performance in older children. In contrast, level of self-initiated memory retrieval did not affect TBPM performance. However, strategies of TM influenced TBPM, as more frequent time checking was related to better performance. Patterns of time checking frequency differed according to children’s age and course of the game, suggesting difficulties in maintaining initial strategic TM in younger children. Taken together, the study revealed ongoing development of TBPM across primary school age. Observed age differences seemed to be associated with the ability to maintain strategic monitoring.

Remembrance of Things Future: Prospective Memory in Laboratory, Workplace, and Everyday Settings

Prospective memory involves remembering—and sometimes forgetting—to perform tasks that must be deferred. This chapter summarizes and provides a perspective on research and theory in this new and rapidly growing field. I explore the limits of existing experimental paradigms, which fail to capture some critical aspects of performance outside of laboratory settings, and review the relatively few studies in workplace and everyday settings. I suggest countermeasures to reduce vulnerability to forgetting to perform deferred tasks, identify roles for human factors practitioners, and propose a research agenda that would extend the current understanding of prospective memory performance.

Time keeping and working memory development in early adolescence: a 4-year follow-up

In this longitudinal study, we examined time keeping in relation to working memory (WM) development. School-aged children completed two tasks of WM updating and a time monitoring task in which they indicated the passing of time every 5 min while watching a film. Children completed these tasks first when they were 8 to 12 years old and then 4 years later when they were 12 to 16 years old. Time keeping in early adolescence showed a different pattern of outcome measures than 4 years earlier, with reduced clock checking and increased timing error. However, relative changes in WM development moderated these adverse effects. Adolescents with greater relative gains in WM development were better calibrated than participants with less developing WM functions. We discuss these findings in relation to individual and developmental differences in executive control functions and socioemotionally driven reward seeking.

A large-scale comparison of prospective and retrospective memory development from childhood to middle age

We present the first large-scale comparison of prospective memory (PM) and retrospective memory (RM) from 8 to 50 years of age ( N = 318,614). Participants in an Internet study were asked to remember to click on a smiley face (single-trial event-based PM test) and to indicate whether/where a picture had changed from study to test (single-trial RM test), in both cases after retention intervals filled with working-memory tests and questionnaires. Both PM and RM improved during childhood; however, whereas maximal PM was reached by teenagers, with approximately linear decline through the 20s–40s, RM continued to improve through the 20s and 30s. On both tests, females outperformed males and achieved maximal success at earlier ages. Strikingly, 10–11-year-old girls performed significantly better than females in their late 20s on the PM test. The presence of the smiley face at encoding and temporal uncertainty (expecting it “later” rather than at the “end” of the test) both benefited PM; these effects decreased and increased, respectively, from childhood to middle age. The findings demonstrate that in a cross-sectional study (a) developmental trajectories are qualitatively different between PM and RM, and (b) the relative influence of PM cues differs between younger and older ages.

The storehouse/correspondence partition in memory research: Promises and perils

The novel correspondence metaphor outlined by Koriat & Goldsmith offers important advantages for studying critical issues of memory-accuracy. It also fits well with the current emphasis on the reconstructive nature of memory and on the role of cognitive, metacognitive, and motivational factors in memory performance. These positive features notwithstanding, the storehouse/correspondence framework faces potential perils having to do with its implied linkage to the laboratory/real-life controversy and its proposal of studying correspondence issues in isolation from memory phenomena captured by the storehouse paradigm.

Memory, metamemory, and conditional statistics

Koriat & Goldsmith's distinction between encoding processes and metamnemonic decision processes is theoretically and practically important, as is their methodology for separating the two. However, their accuracy measure is a conditional statistic, subject to the unfathomable selection effects that have hindered analogous measures in the past. We also find their arguments concerning basic and applied research mostly beside the point.

The alternative to the storehouse metaphor

Koriat and Goldsmith clearly show the need for an alternative to the storehouse metaphor; however, the alternative metaphor they choose – the correspondence metaphor – is problematic. A more suitable one is the capacity metaphor.

Memory metaphors and the real-life/laboratory controversy: Correspondence versus storehouse conceptions of memory

The study of memory is witnessing a spirited clash between proponents of traditional laboratory research and those advocating a more naturalistic approach to the study of “real-life” or “everyday” memory. The debate has generally centered on the “what” (content), “where” (context), and “how” (methods) of memory research. In this target article, we argue that the controversy discloses a further, more fundamental breach between two underlying memory metaphors, each having distinct implications for memory theory and assessment: Whereas traditional memory research has been dominated by thestorehousemetaphor, leading to a focus on thenumberof items remaining in store and accessible to memory, the recent wave of everyday memory research has shifted toward acorrespondencemetaphor, focusing on theaccuracyof memory in representing past events. The correspondence metaphor calls for a research approach that differs from the traditional one in important respects: in emphasizing the intentional –representational function of memory, in addressing the wholistic and graded aspects of memory correspondence, in taking an output-bound assessment perspective, and in allowing more room for the operation of subject-controlled metamemory processes and motivational factors. This analysis can help tie together soine of the what, where, and how aspects of the “real-life/laboratory” controversy. More important, however, by explicating the unique metatheoretical foundation of the accuracy-oriented approach to memory we aim to promote a more effective exploitation of the correspondence metaphor inbothnaturalistic and laboratory research contexts.

What do memories correspond to?

Neither the storehouse nor the correspondence metaphor is an appropriate conceptual framework for memory research. Instead a meaning-based account of human memory is required. The correspondence metaphor is an advance over previous suggestions but entails an oversimple view of “accuracy.” Freud's account of memory may provide a more fruitful approach to memory and meaning.

The correspondence metaphor of memory: Right, wrong, or useful?

Our response to the commentators covers four general issues: (1) How useful is our proposed conceptualization of the real-life/laboratory controversy in terms of the contrast between the correspondence and storehouse metaphors? (2) What is the relationship between these two metaphors? (3) What are the unique implications of the correspondence metaphor for memory assessment and theory? (4) What are the nature and role of memory metaphors in memory research? We stress that the correspondence metaphor can be usefully exploited independent of the real-life/laboratory controversy, but that a variety of other metaphors, including the storehouse, should also be utilized in order to more fully capture the myriad facets and functions of memory in everyday life.

Beyond the correspondence metaphor: When accuracy cannot be assessed

Koriat & Goldsmith propose that the correspondence metaphor captures the essence of everyday memory research. We suggest that correspondence is often not at issue because objective assessments of everyday events are frequently lacking. In these cases, other questions arise, such as how individuals evaluate the validity of memories and the significance they attach to those evaluations.

Contexts and functions of retrieval

Koriat & Goldsmith provide an excellent analysis of the flexibility of retrieval processes and how they are situationally dependent. I agree with their emphasis on functional considerations and argue that the traditional laboratory experiment motivates the subject to be accurate. However, I disagree with their strong claim that the quantity–accuracy distinction implies an essential discontinuity between traditional and naturalistic approaches to the study of memory.

Implications of output-bound measures for laboratory and field research in memory

Everyday memory tasks often require that researchers focus on output-bound measures of memory. As a result, nonmemorial processes (e.g., report option and grain size) may influence recall accuracy. These nonmemorial processes, usually eliminated by laboratory researchers, have the potential to explain some anomalous results and may even be useful to enhance everyday recollection.

The relation between reproductive and reconstructive processing of memory content

Quantitative losses of memory content imply replicative processing; correspondence losses imply reconstructive processing. Research should focus on the relationship between these processes by obtaining accuracy- and quantity-based indicators of memory within the same framework. This approach will also yield information about the effects of task and individual-difference variables on loss and distortion, as well as the time course of each process.

Direct remembering and the correspondence metaphor

The correspondence view is consistent with a theory of direct remembering that assumes continuity between perception and memory. Two implications of direct remembering for correspondence are suggested. It is assumed that forgetting is exponential, and that remembering at one time is independent of factors influencing remembering at another. Elaboration of the correspondence view in the same terms as perception offers a novel approach to the study of memory.

Correspondence to the past: The essence of the archaeology metaphor

The correspondence view of memory is not a metaphor. However, correspondence is the essential feature of the archaeology metaphor, which harks back to Freud and Neisser. A modern version of this metaphor and some of its implications are briefly described. The archaeology metaphor integrates the idea of stored traces in a nonmechanistic framework.

Remembering as doing

Koriat & Goldsmith are right in their claim that the “ecological” and “traditional” approaches to memory rely on different metaphors. But the underlying ecological metaphor is notcorrespondence(which in any case is not a metaphorical notion): it isaction. Remembering is a kind of doing; like most other forms of action it is purposive, personal, and particular.

Functional memory requires a quite different value metaphor

The function of memory is to allow past experience to subserve present goal-oriented thought and action. The defining characteristic of goal-oriented approach/avoidance is value. Value lies beyond the reproductive conception of memory that is basic to both metaphors discussed in Koriat & Goldsmith's target article. Functional memory requires a quite different metaphor, for which a grounded theory is available.

Development of rostral prefrontal cortex and cognitive and behavioural disorders

Information on the development and functions of rostral prefrontal cortex (PFC), or Brodmann area 10, has been gathered from different fields, from anatomical development to functional neuroimaging in adults, and put forward in relation to three particular cognitive and behavioural disorders. Rostral PFC is larger and has a lower cell density in humans than in other primates. It also has a large number of dendritic spines per cell and numerous connections to the supramodal cortex. These characteristics suggest that rostral PFC is likely to support processes of integration or coordination of inputs that are particularly developed in humans. The development of rostral PFC is prolonged, with decreases in grey matter and synaptic density continuing into adolescence. Functions attributed to rostral PFC, such as prospective memory, seem similarly to follow a prolonged development until adulthood. Neuroimaging studies have generally found a reduced recruitment of rostral PFC, for example in tasks requiring response inhibition, in adults compared with children or adolescents, which is consistent with maturation of grey matter. The examples of autism, attention-deficit-hyperactivity disorder, and schizophrenia show that rostral PFC could be affected in several disorders as a result of the susceptibility of its prolonged maturation to developmental abnormalities.

Transparent meta-analysis of prospective memory and aging

Prospective memory (ProM) refers to our ability to become aware of a previously formed plan at the right time and place. After two decades of research on prospective memory and aging, narrative reviews and summaries have arrived at widely different conclusions. One view is that prospective memory shows large age declines, larger than age declines on retrospective memory (RetM). Another view is that prospective memory is an exception to age declines and remains invariant across the adult lifespan. The present meta-analysis of over twenty years of research settles this controversy. It shows that prospective memory declines with aging and that the magnitude of age decline varies by prospective memory subdomain (vigilance, prospective memory proper, habitual prospective memory) as well as test setting (laboratory, natural). Moreover, this meta-analysis demonstrates that previous claims of no age declines in prospective memory are artifacts of methodological and conceptual issues afflicting prior research including widespread ceiling effects, low statistical power, age confounds, and failure to distinguish between various subdomains of prospective memory (e.g., vigilance and prospective memory proper).

Event-based Prospective Memory in Schizophrenia

Although memory deficits have been well documented in schizophrenia, so far, there is dearth of literature about prospective memory (PM), that is memory for future events, in this disorder. The present study investigated event-based PM in schizophrenia. Additionally, the relationship of event-based PM with clinical variables of schizophrenia was also assessed. Task incorporating event-based prospective memory was administered on 42 schizophrenia patients and 42 nonpsychiatric comparison subjects. Patients with schizophrenia were additionally rated on The Scale for the Assessment of Positive Symptoms, The Scale for the Assessment of Negative Symptoms and The Brief Psychiatric Rating Scale. Results showed schizophrenia patients to have poor event-based prospective memory. However, no significant correlation was observed between the clinical variables and PM.

Development of Prospective Memory: Tasks Based on the Prefrontal-Lobe Model

This study investigated the development of prospective memory using tasks based on the prefrontal-lobe model. Three groups each of 30 children, adolescents, and young adults were compared on prospective-memory performance using ongoing tasks with two levels of cognitive demand (low and high), and two levels of importance (unstressed and stressed) of remembering prospective cues. The Self-Ordered Pointing Task (SOPT), Stroop Color Word Interference Test, and Tower of London were also used to assess relationships between prospective memory and prefrontal-lobe functions. The children remembered fewer prospective cues than either the adolescents or adults, but the adolescents and adults remembered equally well. This trend increased significantly as the cognitive demand of the ongoing tasks increased. However, stressing or not stressing the importance of remembering made no difference to prospective-memory performance. Performance on the SOPT and Stroop Colour Word Interference predicted performance on the high- but not on the low-demand condition. These findings implicate the maturation of the brain's prefrontal region in the development of prospective memory.

Time monitoring and executive functioning in children and adults

This study examined time-based prospective memory performance in relation to individual and developmental differences in executive functioning. School-age children and young adults completed six experimental tasks that tapped three basic components of executive functioning: inhibition, updating, and mental shifting. Monitoring performance was examined in a time-based prospective memory task in which participants indicated the passing of time every 5min while watching a movie. Separate analyses of the executive functioning data yielded a two-factor solution for both age groups, with the updating and inhibition tasks constituting a common factor and the shifting tasks constituting a separate factor. Both children and adults showed accelerating monitoring functions with low rates of clock checking during the early phase of each 5-min interval. However, compared with adults, children needed more clock checks for obtaining the same level of response accuracy. Executive functioning had selective effects on time-based prospective memory performance. In both children and adults, monitoring performance was related to the inhibition and updating components, but not to the shifting component, of executive functioning. We conclude that difficulties in temporary maintenance and updating of working memory contents may create discontinuities in sense of time, leading to an increased reliance on external cues for time keeping.

Die Entwicklung des prospektiven Gedächtnisses über die Lebensspanne

Zusammenfassung. Das prospektive Gedächtnis bezeichnet das Zusammenspiel jener kognitiven Fähigkeiten, die daran beteiligt sind, intendierte Handlungen zu planen und sie später zur adäquaten Gelegenheit selbstständig zu realisieren. In dieser Übersichtsarbeit werden Befunde von Studien erörtert, welche die Entwicklung des prospektiven Erinnerns im Kindes- und Jugendalter und vom jüngeren zum höheren Erwachsenenalter untersuchten. Neben der Identifikation erster konsistenter Trends wird außerdem auf eine paradoxe und bisher noch ungeklärte Befundlage bezüglich des alterskorrelierten Ausführens intendierter Handlungen im Labor und im Alltagsleben hingewiesen. Über die Deskription hinausgehend werden in einem zweiten Teil potenzielle Erklärungsmechanismen der Entwicklung des prospektiven Gedächtnisses über die Lebensspanne identifiziert und kritisch diskutiert.

Task interference from prospective memories covaries with contextual associations of fulfilling them

One of the current issues in the field of prospective memory concerns whether having an intention produces a cost to other ongoing activities (called task interference). The evidence to date suggests that certain intentions held over the shorter term do interfere with other tasks. Because the cumulative effect of such costs would be prohibitively expensive in everyday life, the present study examined one means by which that interference may be reduced. Participants who formed a specific association to fulfilling an intention in a future context did not exhibit task interference over the intervening period until that context was encountered. This outcome was observed with both an event-based and a time-based prospective memory task. The results suggest that associating intention fulfillment with a specific context can eliminate task interference, and they emphasize the importance of studying intentions that are linked to future contexts versus those that are not.

Prospective memory failures as an unexplored threat to patient safety: results from a pilot study using patient simulators to investigate the missed execution of intentions

This study investigated failures of prospective memory (PM) as a relevant but neglected error type in medicine. A patient simulator was used to investigate PM failures. The influence of subjective importance (high, low) and type of intention (educational, internal, external) on the (missed) execution of intention was investigated in a 2 x 2 design. The effects on missed executions by importance (high < low) and type of intention (educational < external < internal) were hypothesized. Of 73 valid intentions in 40 prepared simulator scenarios 19 (26%) were missed overall. A total of 64% of unimportant and 80% of important intentions were executed 79% of educational 67% of external and 72% of internal intentions were executed. Neither difference was statistically significant using chi(2) tests. Interaction was significant for missed executions (p = 0.025; n = 19; df = 2; chi(2) = 7.41) and for executions (p = 0.002; n = 54; df = 2; chi(2) = 12.50). Despite low statistical support and some methodological limitations, it was possible to show that PM failures are relevant to patient safety and that patient simulators are a suitable but so far unused tool for their investigation.

Cast in Six Ponds and You'll Reel in Something: Looking Back on 25 Years of Research

The author describes his program of research over the past 25 years. This research falls into 6 areas that are interdependent and that inform each other. The overall program is guided by 3 bioecological principles that posit the need for proximal processes and motivation to actualize biological potential. The author presents examples of experiments that fall into each of the 6 areas and show that human potential is highly contextualized and that, consequently, the same person who fails at a task in one domain is often able to succeed at it in a different domain.

The cost of remembering to remember in event-based prospective memory: investigating the capacity demands of delayed intention performance

Prospective memory tasks are often accomplished during the performance of other activities. Despite the dual-task nature of prospective memory, little attention has been paid to how successful prospective memory performance affects ongoing activities. In the first 2 experiments, participants performing an embedded prospective memory task had longer response times on nonprospective memory target trials of a lexical decision task than participants performing the lexical decision task alone. In the prospective memory groups, longer lexical decision response times were associated with better prospective memory performance (Experiments 1, 2, and 3), a pattern not demonstrated with an embedded retrospective memory task (Experiment 2). The results of Experiment 3 suggest that the retrieval of a delayed intention, or the prospective component, can require capacity.

Preliminary remarks on type of task and delay in children's prospective memory

This study investigated the extent to which the type of task influences children's prospective memory performance. 80 subjects, aged 7 to 11 yr. participated in an experiment in which the type of task (time-based vs event-based) and the retention interval (5 min. vs 10 min.) varied. The prospective memory task was embedded in a principal task lasting about 15 min. and required subjects perform an action at a given time or in response to a specific cue. Analysis indicated that the delay was associated with prospective memory performance only on a time-based task in which the intention has to be performed after 10 min. but not age. Analysis indicated also that time monitoring was associated with shorter latency between the target time and the execution of the intention on the time-based task. Implications were discussed.

Prospective and retrospective memory in normal aging and dementia: an experimental study

Two experiments investigated the effects of normal aging and dementia on laboratory-based prospective memory (PM) tasks. Participants viewed a film for a later recognition memory task. In Experiment 1, they were also required either to say "animal" when an animal appeared in the film (event-based PM task) or to stop a clock every 3 min (time-based PM task). In both tasks, young participants were more successful than older participants, who were, in turn, more successful than patients with Alzheimer's disease (AD). For successful remembering in the time-based task, older participants and AD patients checked the clock more often than did young participants. In Experiment 2, participants were asked to reset a clock either when an animal appeared in the film (unrelated cue-action) or when a clock appeared in the film (related cue-action). Responses were faster in the related condition than in the unrelated condition. Again, there were differences in PM performance between young and older participants, and between older participants and AD patients. The observed deficits were not due to the forgetting of the PM task instructions in either experiment. Retrospective memory (RM) tasks (digit span, sentence span, free recall, and recognition) were more impaired by AD than were the PM tasks. Factor analysis revealed separate factors corresponding to RM and PM.

When and where do we apply what we learn? A taxonomy for far transfer

Despite a century's worth of research, arguments surrounding the question of whether far transfer occurs have made little progress toward resolution. The authors argue the reason for this confusion is a failure to specify various dimensions along which transfer can occur, resulting in comparisons of "apples and oranges." They provide a framework that describes 9 relevant dimensions and show that the literature can productively be classified along these dimensions, with each study situated at the intersection of various dimensions. Estimation of a single effect size for far transfer is misguided in view of this complexity. The past 100 years of research shows that evidence for transfer under some conditions is substantial, but critical conditions for many key questions are untested.

Prospective memory: a new focus for research

Prospective memory is required for many aspects of everyday cognition, its breakdown may be as debilitating as impairments in retrospective memory, and yet, the former has received relatively little attention by memory researchers. This article outlines a strategy for changing the fortunes of prospective memory, for guiding new research to shore up the claim that prospective memory is a distinct aspect of cognition, and to obtain evidence for clear performance dissociations between prospective memory and other memory functions. We begin by identifying the unique requirements of prospective memory tasks and by dividing memory's prospective functions into subdomains that are analogous to divisions in retrospective memory (e.g., short- versus long-term memory). We focus on one prospective function, called prospective memory proper; we define this function in the spirit of James (1890) as requiring that we are aware of a plan, of which meanwhile we have not been thinking, with the additional consciousness that we made the plan earlier. We give an operational definition of prospective memory proper and specify how it differs from explicit and implicit retrospective memory and how it might be empirically assessed.