Jill Talley Shelton

Focal/Nonfocal Cue Effects in Prospective Memory: Monitoring Difficulty or Different Retrieval Processes?

We investigated whether focal/nonfocal effects (e.g., Einstein et al., 2005) in prospective memory (PM) are explained by cue differences in monitoring difficulty. In Experiment 1, we show that syllable cues (used in Einstein et al., 2005) are more difficult to monitor for than are word cues; however, initial-letter cues (in words) are similar in monitoring difficulty to word cues (Experiments 2a and 2b). Accordingly, in Experiments 3 and 4, we designated either an initial letter or a particular word as a PM cue in the context of a lexical decision task, a task that presumably directs attention to focal processing of words but not initial letters. We found that the nonfocal condition was more likely than the focal condition to produce costs to the lexical decision task (task interference). Furthermore, when task interference was minimal or absent, focal PM performance remained relatively high, whereas nonfocal PM performance was near floor (Experiment 4). Collectively, these results suggest that qualitatively different retrieval processes can support prospective remembering for focal versus nonfocal cues.

The Dynamic Multiprocess Framework: Evidence from prospective memory with contextual variability

The ability to remember to execute delayed intentions is referred to as prospective memory. Previous theoretical and empirical work has focused on isolating whether a particular prospective memory task is supported either by effortful monitoring processes or by cue-driven spontaneous processes. In the present work, we advance the Dynamic Multiprocess Framework, which contends that both monitoring and spontaneous retrieval may be utilized dynamically to support prospective remembering. To capture the dynamic interplay between monitoring and spontaneous retrieval, we had participants perform many ongoing tasks and told them that their prospective memory cue may occur in any context. Following either a 20-min or a 12-h retention interval, the prospective memory cues were presented infrequently across three separate ongoing tasks. The monitoring patterns (measured as ongoing task cost relative to a between-subjects control condition) were consistent and robust across the three contexts. There was no evidence for monitoring prior to the initial prospective memory cue; however, individuals who successfully spontaneously retrieved the prospective memory intention, thereby realizing that prospective memory cues could be expected within that context, subsequently monitored. These data support the Dynamic Multiprocess Framework, which contends that individuals will engage monitoring when prospective memory cues are expected, disengage monitoring when cues are not expected, and that when monitoring is disengaged, a probabilistic spontaneous retrieval mechanism can support prospective remembering.

Structural Correlates of Prospective Memory

Prospective memory (PM) includes the encoding and maintenance of an intention, and the retrieval and execution of this intention at the proper moment in the future. The present study expands upon previous behavioral, electrophysiological, and functional work by examining the association between grey matter volume and PM. Estimates of grey matter volume in theoretically relevant regions of interest (prefrontal, parietal, and medial temporal) were obtained in conjunction with performance on two PM tasks in a sample of 39 cognitively normal and very mildly demented older adults. The first PM task, termed focal in the literature, is supported by spontaneous retrieval of the PM intention whereas the second, termed non-focal, relies on strategic monitoring processes for successful intention retrieval. A positive relationship was observed between medial temporal volume and accuracy on the focal PM task. An examination of medial temporal lobe subregions revealed that this relationship was strongest for the hippocampus, which is considered to support spontaneous memory retrieval. There were no significant structure-behavior associations for the non-focal PM task. These novel results confirm a relationship between behavior and underlying brain structure proposed by the multiprocess theory of PM, and extend findings on cognitive correlates of medial temporal lobe integrity.

Dual n-back training increases the capacity of the focus of attention

Working memory (WM) training has been reported to benefit abilities as diverse as fluid intelligence (Jaeggi et al., Proceedings of the National Academy of Sciences of the United States of America, 105:6829–6833, 2008) and reading comprehension (Chein & Morrison, Psychonomic Bulletin & Review, 17:193–199, 2010), but transfer is not always observed (for reviews, see Morrison & Chein, Psychonomics Bulletin & Review, 18:46–60, 2011; Shipstead et al., Psychological Bulletin, 138:628–654, 2012). In contrast, recent WM training studies have consistently reported improvement on the trained tasks. The basis for these training benefits has received little attention, however, and it is not known which WM components and/or processes are being improved. Therefore, the goal of the present study was to investigate five possible mechanisms underlying the effects of adaptive dual n-back training on working memory (i.e., improvements in executive attention, updating, and focus switching, as well as increases in the capacity of the focus of attention and short-term memory). In addition to a no-contact control group, the present study also included an active control group whose members received nonadaptive training on the same task. All three groups showed significant improvements on the n-back task from pretest to posttest, but adaptive training produced larger improvements than did nonadaptive training, which in turn produced larger improvements than simply retesting. Adaptive, but not nonadaptive, training also resulted in improvements on an untrained running span task that measured the capacity of the focus of attention. No other differential improvements were observed, suggesting that increases in the capacity of the focus of attention underlie the benefits of adaptive dual n-back training.

Can we improve the clinical assessment of working memory? An evaluation of the Wechsler Adult Intelligence Scale–Third Edition using a working memory criterion construct

Working memory is the cognitive ability to hold a discrete amount of information in mind in an accessible state for utilization in mental tasks. This cognitive ability is impaired in many clinical populations typically assessed by clinical neuropsychologists. Recently, there have been a number of theoretical shifts in the way that working memory is conceptualized and assessed in the experimental literature. This study sought to determine to what extent the Wechsler Adult Intelligence Scale–Third Edition (WAIS–III) Working Memory Index (WMI) measures the construct studied in the cognitive working memory literature, whether an improved WMI could be derived from the subtests that comprise the WAIS–III, and what percentage of variance in individual WAIS–III subtests is explained by working memory. It was hypothesized that subtests beyond those currently used to form the WAIS–III WMI would be able to account for a greater percentage of variance in a working memory criterion construct than the current WMI. Multiple regression analyses (n = 180) revealed that the best predictor model of subtests for assessing working memory was composed of the Digit Span, Letter–Number Sequencing, Matrix Reasoning, and Vocabulary. The Arithmetic subtest was not a significant contributor to the model. These results are discussed in the context of how they relate to Unsworth and Engles (2006, 2007) new conceptualization of working memory mechanisms.

A Characterization of Individual Differences in Prospective Memory Monitoring Using the Complex Ongoing Serial Task.

Prospective memory--remembering to retrieve and execute future goals--is essential to daily life. Prospective remembering is often achieved through effortful monitoring; however, potential individual differences in monitoring patterns have not been characterized. We propose 3 candidate models to characterize the individual differences present in prospective memory monitoring: attentional focus, secondary memory retrieval, and information thresholding. Two experiments using a novel paradigm, the Complex Ongoing Serial Task (COST), investigated the resource allocation patterns underlying individual differences in monitoring. Individuals exhibited differential resource allocation patterns, and the differences remained relatively stable across experimental sessions. Resource allocation patterns associated with information thresholding (high prospective memory, preserved ongoing task performance) and attentional focus (high prospective memory, inefficient ongoing task performance) were superior to secondary memory retrieval (low prospective memory, very inefficient ongoing task performance). Importantly, personality (openness, prevention focus) and cognitive (primary, working, and secondary memory) individual differences influenced monitoring patterns. This research represents the first explicit attempt to elucidate individual differences in prospective memory monitoring patterns.

The role of modality: Auditory and visual distractors in Stroop interference

As a commonly used measure of selective attention, it is important to understand the factors contributing to interference in the Stroop task. The current research examined distracting stimuli in the auditory and visual modalities to determine whether the use of auditory distractors would create additional interference, beyond what is typically observed in the print-based Stroop task. Research by Cowan and Barron supported the additive effects of auditory and visual distractors; however, there is only one empirical demonstration of this finding to date. Using different versions of the Stroop colour-naming task, behavioural analyses of reaction times (RT) were conducted, along with distributional RT analyses. The results indicated that a combination of visual and auditory distraction did not lead to a larger interference effect than visually based distraction alone. These findings suggest that methodological issues may have influenced the prior finding of additive effects of the two modalities, and are discussed in relation to the word production architecture account of Stroop effects.

Evidence for a detrimental relationship between hypertension history, prospective memory, and prefrontal cortex white matter in cognitively normal older adults

Hypertension affects many older adults and is associated with impaired neural and cognitive functioning. We investigated whether a history of hypertension was associated with impairments to prospective memory, which refers to the ability to remember to perform delayed intentions, such as remembering to take medication. Thirty-two cognitively normal older adult participants with or without a history of hypertension (self-reported) performed two laboratory prospective memory tasks, one that relied more strongly on executive control (nonfocal prospective memory) and one that relied more strongly on spontaneous memory retrieval processes (focal prospective memory). We observed hypertension-related impairments for nonfocal, but not focal, prospective memory. To complement our behavioral approach, we conducted a retrospective analysis of available structural magnetic resonance imaging data. Lower white matter volume estimates in the anterior prefrontal cortex were associated with lower nonfocal prospective memory and with a history of hypertension. A history of hypertension may be associated with worsened executive control and lower prefrontal white matter volume. The translational implication is that individuals who must remember to take antihypertensive medications and to monitor their blood pressure at home may be impaired in the executive control process that helps to support these prospective memory behaviors.

Improving Prospective Memory in Healthy Older Adults and Individuals with Very Mild Alzheimer's Disease

To test the utility of a memory‐encoding strategy for improving prospective memory (PM), the ability to remember to execute future goals (e.g., remembering to take medications), which plays an important role in independent living in healthy older adults and those with very mild Alzheimers disease (AD).

A fresh pair of eyes on prospective memory monitoring.

Remembering to complete one’s future intentions is termed prospective memory. We employed a new eyetracking paradigm to concretely observe the impact of environmental cues on strategic monitoring within a visual prospective memory task. Participants worked on a continuous living-count task comprising images, while simultaneously being asked to respond to a prospective memory target when it appeared. Importantly, the prospective memory target appeared in a different area of the participant’s visual field than did the continuous task, which is consistent with prospective memory in many real-world situations, and further allows for a clear index of strategic monitoring processes. Subtle cues in the form of semantically related images were embedded in the continuous task to prompt monitoring for the prospective memory target. Overt strategic monitoring was operationalized as the number of times participants fixated on the designated target area, and cue-driven monitoring was defined by the number of fixations on the prospective memory target region directly after fixating on a related cue. Overt strategic monitoring for the prospective memory target was directly observed for participants in the prospective memory condition, and cue-driven monitoring was also observed in these participants, since they were more likely to initiate monitoring immediately after fixating on a semantically related cue, relative to an unrelated cue. This psychophysiological approach afforded precise measurement of the strategic monitoring process and revealed how contextual cues in the environment interact with the cognitive mechanisms supporting prospective memory.