Age-related changes in neural mechanisms of prospective memory

The capability to remember and execute intentions in the future – termed prospective memory (PM) – may be of special significance for older adults to enable successful completion of important activities of daily living. Despite the importance of this cognitive function, mixed findings have been obtained regarding age-related decline in PM, and, currently, there is limited understanding of potential contributing mechanisms. In the current study, older (N=41) and younger adults (N=47) underwent task-functional MRI during performance of PM conditions that encouraged either spontaneous retrieval (Focal) or sustained attentional monitoring (Non-focal) to detect PM targets. Older adults exhibited a reduction in PM-related sustained activity within the anterior prefrontal cortex (aPFC) and associated dorsal frontoparietal cognitive control network, due to an increase in non-specific sustained activation in (no-PM) control blocks (i.e., an age-related compensatory shift). Transient PM-trial specific activity was observed in both age groups within a ventral parietal memory network that included the precuneus. However, within a left posterior inferior parietal node of this network, transient PM-related activity was selectively reduced in older adults during the non-focal condition. These age differences in sustained and transient brain activity statistically mediated age-related declines in PM performance, and were potentially linked via age-related changes in functional connectivity between the aPFC and precuneus. Together, they support an account consistent with the Dual Mechanisms of Control framework, in which age-related PM declines are due to neural mechanisms that support proactive cognitive control processes, such as sustained attentional monitoring, while leaving reactive control mechanisms relatively spared.

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title: Age and individual differences influence prospective memory.
abstract: The influence of age and individual ability differences on event-based prospective memory was examined using an adapted version of G. O. Einstein and M. A. McDaniel's (1990) task. Two samples of younger and older adults who differed in educational attainment, occupational status, and verbal ability were compared. Results yield comparable prospective performance for the younger groups and higher ability older adults; lower ability older adults performed more poorly by comparison. Hierarchical regression analyses indicated that working memory span and recognition accounted for small but significant proportions of variance in prospective performance. The contribution of ability level to prospective memory remained significant even after statistically controlling for self-reported health and social activity characteristics. Implications for current views on prospective memory aging are discussed.

title: Normal aging and prospective memory.
abstract: We develop a laboratory paradigm for studying prospective memory and examine whether or not this type of memory is especially difficult for the elderly. In two experiments, young and old subjects were given a prospective memory test (they were asked to perform an action when a target event occurred) and three tests of retrospective memory (short-term memory, free recall, and recognition). From the perspective that aging disrupts mainly self-initiated retrieval processes, large age-related decrements in prospective memory were anticipated. However, despite showing reliable age differences on retrospective memory tests, both experiments showed no age deficits in prospective memory. Moreover, regression analyses produced no reliable relation between the prospective and retrospective memory tasks. Also, the experiments showed that external aids and unfamiliar target events benefit prospective memory performance. These results suggest some basic differences between prospective and retrospective memory.

title: Aging and prospective memory: examining the influences of self-initiated retrieval processes.
abstract: Past research has frequently failed to find age differences in prospective memory. This article tested the possibility that age differences would be more likely to emerge on a prospective memory task that was high in self-initiated retrieval. In the 1st experiment, participants were asked to perform an action every 10 min (a time-based task presumed to be high in self-initiated retrieval); in the 2nd experiment, participants were asked to perform an action whenever a particular word was presented (an event-based task presumed to be relatively low in self-initiated retrieval). Age differences were found with the time-based task but not with the event-based task. This pattern of age differences was again found in a 3rd experiment in which a new experimental procedure was used and the nature of the prospective memory task was directly varied. Generally, the results suggest that self-initiated retrieval processes are an important component of age-related differences across both retrospective and prospective memory tasks.

title: Prospective memory and aging: evidence for preserved spontaneous retrieval with exact but not related cues.
abstract: We examined whether normal aging spares or compromises cue-driven spontaneous retrieval processes that support prospective remembering. In Experiment 1, young and older adults performed prospective-memory tasks that required either strategic monitoring processes for retrieval (nonfocal) or for which participants relied on spontaneous retrieval processes (focal). We found age differences for nonfocal, but not focal, prospective-memory performance. Experiments 2 and 3 used an intention-interference paradigm in which participants were asked to perform a prospective-memory task (e.g., press "Q" when the word money appears) in the context of an image-rating task and were then told to suspend their prospective-memory intention until after completing an intervening lexical-decision task. During the lexical-decision task, we presented the exact prospective-memory cue (e.g., money; Experiments 2 and 3) or a semantically related lure (e.g., wallet; Experiment 3), and we inferred spontaneous retrieval from slowed lexical-decision responses to these items relative to matched control items. Young and older adults showed significant slowing when the exact prospective-memory cue was presented. Only young adults, however, showed significant slowing to the semantically related lure items. Collectively, these results partially support the multiprocess theory prediction that aging spares spontaneous retrieval processes. Spontaneous retrieval processes may become less sensitive with aging, such that older adults are less likely to respond to cues that do not exactly match their encoded targets.

title: The Effects of Age, Ability, and Memory Monitoring on Prospective Memory Task Performance
abstract: In this study we examined the influences of age, ability, and monitoring on event-based prospective memory performance. Two samples of younger and older adults who differed in educational attainment and verbal ability were compared. Monitoring of the prospective task was measured through use of an on-line thought probe.  yielded comparable prospective memory performance for the age/ability groups. On-line monitoring responses revealed a higher frequency of task-irrelevant thoughts among younger adults compared to older adults. However, on-line monitoring data were not related to prospective memory performance. Recognition memory was the strongest predictor of successful prospective memory, followed by working memory. These findings and their implications for current conceptions of prospective memory aging are discussed.

title: Aging and forgetting in prospective and retrospective memory tasks.
abstract: Ss aged 52-83 years were asked to name 30 famous people 4 times over the course of an hour and to respond to 2 targets (a beard and a pipe) by marking the trial number on the response sheet. Initial performance in the prospective memory task was related only to a measure of incidental learning. Subsequent forgetting (i.e., success followed by failure) occurred more often for older Ss than for younger Ss, but there was no difference between the age groups in recovery (i.e., failure followed by success). Forgetting was predicted by age, even after a composite measure of general ability was included in the regression. Recovery was related to general ability alone. These results both replicate and extend those from a reanalysis of a previous study (Maylor, 1990a). They provide a striking contrast with the effect of age on retrospective memory, namely, age-related impairment on initial performance but no effect of age on subsequent forgetting.

title: Age-related impairment in an event-based prospective-memory task.
abstract: Slides of famous people were presented to participants with the instructions to name each face and circle the trial number if the person was wearing glasses (prospective-memory target event). Participants in their 50s and 60s (n = 56) were more successful than participants in their 70s and 80s (n = 59) at both the naming an prospective-memory tasks. An age-related increase in the probability of forgetting replicated an earlier prospective-memory study (E. A. Maylor, 1993); in the present case, there was also an age-related decrease in the probability of recovery. These effects of age remained significant after other measures of current ability were taken into account, including intelligence, speed, and naming performance. For participants who were in both the earlier study (E. A. Maylor, 1993) and this study (n = 65), the correlation between prospective-memory performance on the 2 occasions was significant but only for younger participants. Performance in the prospective-memory task was entirely unrelated to performance in the naming task.

title: Effect of age on event-based and time-based prospective memory.
abstract: The magnitude of age differences on event- and time-based prospective memory tasks was investigated in 2 experiments. Participants performed a working memory task and were also required to perform either an event- or time-based prospective action. Control participants performed either the working memory task only or the prospective memory task only.  yielded age differences on both prospective tasks. The age effect was particularly marked on the time-based task. Performance of the event-based prospective task, however, had a higher cost to performance on the concurrent working memory task than the time-based task did, suggesting that event-based responding has a substantial attentional requirement. The older adults also made a significant number of time-monitoring errors when time monitoring was their sole task. This suggests that some time-based prospective memory deficits in older adults are due to a fundamental deficit in time monitoring rather than to prospective memory.

title: The source of adult age differences in event-based prospective memory: a multinomial modeling approach.
abstract: Event-based prospective memory involves remembering to perform an action in response to a particular future event. Normal younger and older adults performed event-based prospective memory tasks in 2 experiments. The authors applied a formal multinomial processing tree model of prospective memory (Smith & Bayen, 2004) to disentangle age differences in the prospective component (remembering that you have to do something) and the retrospective component (remembering when to perform the action) of prospective memory performance. The modeling results, as well as more traditional analyses, indicate age differences in the resource-demanding prospective component.

title: A meta-analytic review of prospective memory and aging.
abstract: A meta-analysis of prospective memory (PM) studies revealed that in laboratory settings younger participants outperform older participants on tests of both time- and event-based PM (rs=-.39 and -.34, respectively). Event-based PM tasks that impose higher levels of controlled strategic demand are associated with significantly larger age effects than event-based PM tasks that are supported by relatively more automatic processes (rs=-.40 vs. -.14, respectively). However, contrary to the prevailing view in the literature, retrospective memory as measured by free recall is associated with significantly greater age-related decline (r=-.52) than PM, and older participants perform substantially better than their younger counterparts in naturalistic PM studies (rs=.35 and.52 for event- and time-based PM, respectively).

title: Adult age differences, response management, and cue focality in event-based prospective memory: a meta-analysis on the role of task order specificity.
abstract: The present meta-analysis investigated whether event-based prospective memory (PM) age effects differ by task order specificity. In specified PM tasks, the order of the ongoing and the PM task response is predetermined, which imposes demands on cognitive control to navigate the possible response options. In contrast, unspecified PM tasks do not require responding in a particular order. Based on 57 studies and more than 5,500 younger and older adults, results showed larger PM age effects in specified compared with unspecified PM tasks. Additionally, the effect of task focality on age differences was replicated. Results suggest that both pre- and postretrieval processes independently affect PM age effects.

title: Transparent Meta-Analysis: Does Aging Spare Prospective Memory with Focal vs. Non-Focal Cues?
abstract: Prospective memory (ProM) is the ability to become aware of a previously-formed plan at the right time and place. For over twenty years, researchers have been debating whether prospective memory declines with aging or whether it is spared by aging and, most recently, whether aging spares prospective memory with focal vs. non-focal cues. Two recent meta-analyses examining these claims did not include all relevant studies and ignored prevalent ceiling effects, age confounds, and did not distinguish between prospective memory subdomains (e.g., ProM proper, vigilance, habitual ProM) (see Uttl, 2008, PLoS ONE). The present meta-analysis focuses on the following questions: Does prospective memory decline with aging? Does prospective memory with focal vs. non-focal cues decline with aging? Does the size of age-related declines with focal vs. non-focal cues vary across ProM subdomains? And are age-related declines in ProM smaller than age-related declines in retrospective memory?  A meta-analysis of event-cued ProM using data visualization and modeling, robust count methods, and conventional meta-analysis techniques revealed that first, the size of age-related declines in ProM with both focal and non-focal cues are large. Second, age-related declines in ProM with focal cues are larger in ProM proper and smaller in vigilance. Third, age-related declines in ProM proper with focal cues are as large as age-related declines in recall measures of retrospective memory.  The results are consistent with Craik's (1983) proposal that age-related declines on ProM tasks are generally large, support the distinction between ProM proper vs. vigilance, and directly contradict widespread claims that ProM, with or without focal cues, is spared by aging.

title: Strategic and automatic processes in prospective memory retrieval: a multiprocess framework
abstract: Prospective memory situations involve forming intentions and then realizing those intentions at some appropriate time in the future. An interesting feature of most prospective remembering is that recollection of the intended action occurs without an explicit request to attempt retrieval, and we present two views on how this type of remembering can be accomplished. One could strategically monitor the environment for the presence of the target event, or one could rely on anticipated environmental conditions more or less automatically reinstating the intended action. We present data supporting both views and argue that people use multiple approaches for solving the problem of retrieving an intention (prospective memory) after a delay. Moreover, we suggest that the extent to which prospective remembering is supported by relatively automatic processes (versus strategic resource-demanding monitoring) and the probability with which prospective memory is likely to be successful when relying on automatic processes varies as a function of the characteristics of the prospective memory task, target cue, ongoing task, and individual. We argue that the complexity of the empirical findings can best be understood by appealing to this multiprocess view of prospective memory.

title: Multiple processes in prospective memory retrieval: factors determining monitoring versus spontaneous retrieval.
abstract: Theoretically, prospective memory retrieval can be accomplished either by controlled monitoring of the environment for a target event or by a more reflexive process that spontaneously responds to the presence of a target event. These views were evaluated in Experiments 1-4 by examining whether performing a prospective memory task produced costs on the speed of performing the ongoing task. In Experiment 5, the authors directly tested for the existence of spontaneous retrieval. The results supported the multiprocess theory (M. A. McDaniel & G. O. Einstein, 2000) predictions that (a) spontaneous retrieval can occur and can support good prospective memory and (b) depending on task demands and individual differences, people rely to different degrees on monitoring versus spontaneous retrieval for prospective remembering.

title: Age-Related Effects in Prospective Memory are Modulated by Ongoing Task Complexity and Relation to Target Cue
abstract: 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.

title: Neural bases of prospective memory: A meta-analysis and the “Attention to Delayed Intention” (AtoDI) model
abstract: Remembering to realize delayed intentions is a multi-phase process, labelled as prospective memory (PM), and involves a plurality of neural networks. The present study utilized the activation likelihood estimation method of meta-analysis to provide a complete overview of the brain regions that are consistently activated in each PM phase. We formulated the 'Attention to Delayed Intention' (AtoDI) model to explain the neural dissociation found between intention maintenance and retrieval phases. The dorsal frontoparietal network is involved mainly in the maintenance phase and seems to mediate the strategic monitoring processes, such as the allocation of top-down attention both towards external stimuli, to monitor for the occurrence of the PM cues, and to internal memory contents, to maintain the intention active in memory. The ventral frontoparietal network is recruited in the retrieval phase and might subserve the bottom-up attention captured externally by the PM cues and, internally, by the intention stored in memory. Together with other brain regions (i.e., insula and posterior cingulate cortex), the ventral frontoparietal network would support the spontaneous retrieval processes. The functional contribution of the anterior prefrontal cortex is discussed extensively for each PM phase.

title: Dual pathways to prospective remembering
abstract: According to the multiprocess framework (McDaniel and Einstein, 2000), the cognitive system can support prospective memory (PM) retrieval through two general pathways. One pathway depends on top–down attentional control processes that maintain activation of the intention and/or monitor the environment for the triggering or target cues that indicate that the intention should be executed. A second pathway depends on (bottom–up) spontaneous retrieval processes, processes that are often triggered by a PM target cue; critically, spontaneous retrieval is assumed not to require monitoring or active maintenance of the intention. Given demand characteristics associated with experimental settings, however, participants are often inclined to monitor, thereby potentially masking discovery of bottom–up spontaneous retrieval processes. In this article, we discuss parameters of laboratory PM paradigms to discourage monitoring and review recent behavioral evidence from such paradigms that implicate spontaneous retrieval in PM. We then re-examine the neuro-imaging evidence from the lens of the multiprocess framework and suggest some critical modifications to existing neuro-cognitive interpretations of the neuro-imaging results. These modifications illuminate possible directions and refinements for further neuro-imaging investigations of PM.

title: Age differences in brain systems supporting transient and sustained processes involved in prospective memory and working memory
abstract: In prospective memory (PM), an intention to act in response to an external event is formed, retained, and at a later stage, when the event occurs, the relevant action is performed. PM typically shows a decline in late adulthood, which might affect functions of daily living. The neural correlates of this decline are not well understood. Here, 15 young (6 female; age range=23-30years) and 16 older adults (5 female; age range=64-74years) were scanned with fMRI to examine age-related differences in brain activation associated with event-based PM using a task that facilitated the separation of transient and sustained components of PM. We show that older adults had reduced performance in conditions with high demands on prospective and working memory, while no age-difference was observed in low-demanding tasks. Across age groups, PM task performance activated separate sets of brain regions for transient and sustained responses. Age-differences in transient activation were found in fronto-striatal and MTL regions, with young adults showing more activation than older adults. Increased activation in young, compared to older adults, was also found for sustained PM activation in the IFG. These results provide new evidence that PM relies on dissociable transient and sustained cognitive processes, and that age-related deficits in PM can be explained by an inability to recruit PM-related brain networks in old age.

title: Age-related differences in the neural correlates of remembering time-based intentions
abstract: The present study used event-related potentials (ERPs) to explore the effect of age on the neural correlates of monitoring processes involved in time-based prospective memory. In both younger and older adults, the addition of a time-based prospective memory task to an ongoing task led to a sustained ERP activity broadly distributed over the scalp. Older adults, however, did not exhibit the slow wave activity observed in younger adults over prefrontal regions, which is considered to be associated with retrieval mode. This finding indicates that age-related decline in intention maintenance might be one source of the impaired prospective memory performance displayed by older adults. An 'anterior shift' in scalp distribution of the P3 was observed in older adults, and was related to lower levels of accuracy in prospective memory performance. This relationship suggests that possible factors responsible for age-related decline in prospective memory performance include the decreased efficiency of executive/frontal functions as well as the reduced amount of resources available for the prospective memory task.

title: Age-related differences in the temporal dynamics of prospective memory retrieval: A lifespan approach
abstract: The efficiency of prospective memory (PM) typically increases from childhood to young adulthood and then decreases in later adulthood. The current study used event-related brain potentials (ERPs) to examine the development of the neural correlates of processes associated with the detection of a PM cue, switching from the ongoing activity to the prospective task, retrieval of the intention from memory or task set configuration, and strategic monitoring of the environment. The study included 99 participants that were 7.5-83 years of age. Slow wave activity related to strategic monitoring was reliable across the lifespan suggesting that all ages were able to allocate attentional resources to facilitate PM. Additionally, components of the ERPs related to cue detection, switching, and task configuration were reliable across the lifespan, suggesting that similar processes contribute to PM at all ages. In children, PM errors may have resulted from a decoupling of processes supporting cue detection and switching from the ongoing activity to the prospective element of the task. In younger and older adults, PM errors appeared to result from the failure to detect PM cues in the environment. These findings lead to the conclusion that different processes may contribute to variation in PM across the lifespan.

title: Effects of aging and working memory demands on prospective memory.
abstract: The current study used event-related brain potentials (ERPs) to examine the effects of aging, increasing the working memory demands of the ongoing activity, and a prospective memory load on the neural correlates of prospective remembering and target recognition. The behavioral data revealed that the success of prospective memory was sensitive to working memory load in younger, but not older, adults and that a prospective memory load had a greater effect on the performance of older adults than that of younger adults. The ERP data revealed age-related differences in the neural correlates of the detection of prospective cues, post-retrieval processes that support prospective memory, and target recognition. Our results support the hypothesis that there are age-related differences in the ability to recruit preparatory attentional processes that underlie prospective memory, and demonstrate that younger and older adults may recruit somewhat different neural generators to support prospective memory and working memory.

title: Functional neuroimaging studies of prospective memory: What have we learnt so far?
abstract: The complexity of the behaviour described by the term "prospective memory" meant that it was not at all clear, when the earliest studies were conducted, that this would prove a fruitful area for neuroimaging study. However, a consistent relation rapidly emerged between activation in rostral prefrontal cortex (approximating Brodmann Area 10) and performance of prospective memory paradigms. This consistency has greatly increased the accumulation of findings, since each study has offered perspectives on the previous ones. Considerable help too has come from broad agreement between functional neuroimaging findings and those from other methods (e.g. human lesion studies, electrophysiology). The result has been a quite startling degree of advance given the relatively few studies that have been conducted. These findings are summarised, along with those from other brain regions, and new directions suggested. Key points are that there is a medial-lateral dissociation within rostral PFC. Some (but not all) regions of medial rostral PFC are typically more active during performance of the ongoing task only, and lateral aspects are relatively more active during conditions involving delayed intentions. Some of these rostral PFC activations seem remarkably insensitive to the form of stimulus material presented, the nature of the ongoing task, the specifics of the intention, how easy or hard the PM cue is to detect, or the intended action is to recall. However there are other regions within rostral PFC where haemodynamic changes vary with alterations in these, and other, aspects of prospective memory paradigms. It is concluded that rostral PFC most likely plays a super-ordinate role during many stages of creating, maintaining and enacting delayed intentions, which in some cases may be linked to recent evidence showing that this brain region is involved in the control of stimulus-oriented vs. stimulus-independent attending. Other key brain regions activated during prospective memory paradigms appear to be the parietal lobe, especially Brodmann Area (BA) 40 and precuneus (BA 7), and the anterior cingulate (BA 32). These regions are often co-activated with lateral rostral PFC across a wide range of tasks, not just those involving prospective memory.

title: Dissociable Neural Routes to Successful Prospective Memory
abstract: Identifying the processes by which people remember to execute an intention at an appropriate moment (prospective memory) remains a fundamental theoretical challenge. According to one account, top-down attentional control is required to maintain activation of the intention, initiate intention retrieval, or support monitoring. A diverging account suggests that bottom-up, spontaneous retrieval can be triggered by cues that have been associated with the intention and that sustained attentional processes are not required. We used a specialized experimental design and functional MRI methods to selectively marshal and identify each process. Results revealed a clear dissociation. One prospective-memory task recruited sustained activity in attentional-control areas, such as the anterior prefrontal cortex; the other engaged purely transient activity in parietal and ventral brain regions associated with attentional capture, target detection, and episodic retrieval. These patterns provide critical evidence that there are two neural routes to prospective memory, with each route emerging under different circumstances.

title: Effects of cue focality on the neural mechanisms of prospective memory: A meta-analysis of neuroimaging studies
abstract: Remembering to execute pre-defined intentions at the appropriate time in the future is typically referred to as Prospective Memory (PM). Studies of PM showed that distinct cognitive processes underlie the execution of delayed intentions depending on whether the cue associated with such intentions is focal to ongoing activity processing or not (i.e., cue focality). The present activation likelihood estimation (ALE) meta-analysis revealed several differences in brain activity as a function of focality of the PM cue. The retrieval of intention is supported mainly by left anterior prefrontal cortex (Brodmann Area, BA 10) in nonfocal tasks, and by cerebellum and ventral parietal regions in focal tasks. Furthermore, the precuneus showed increased activation during the maintenance phase of intentions compared to the retrieval phase in nonfocal tasks, whereas the inferior parietal lobule showed increased activation during the retrieval of intention compared to maintenance phase in the focal tasks. Finally, the retrieval of intention relies more on the activity in anterior cingulate cortex for nonfocal tasks, and on posterior cingulate cortex for focal tasks. Such focality-related pattern of activations suggests that prospective remembering is mediated mainly by top-down and stimulus-independent processes in nonfocal tasks, whereas by more automatic, bottom-up, processes in focal tasks.

title: The variable nature of cognitive control: a dual mechanisms framework
abstract: A core component of cognitive control - the ability to regulate thoughts and actions in accordance with internally represented behavioral goals - might be its intrinsic variability. In this article, I describe the dual mechanisms of control (DMC) framework, which postulates that this variability might arise from qualitative distinctions in temporal dynamics between proactive and reactive modes of control. Proactive control reflects the sustained and anticipatory maintenance of goal-relevant information within lateral prefrontal cortex (PFC) to enable optimal cognitive performance, whereas reactive control reflects transient stimulus-driven goal reactivation that recruits lateral PFC (plus a wider brain network) based on interference demands or episodic associations. I summarize recent research that demonstrates how the DMC framework provides a coherent explanation of three sources of cognitive control variation - intra-individual, inter-individual and between-groups - in terms of proactive versus reactive control biases.

title: Age-related shifts in brain activity dynamics during task switching.
abstract: Cognitive aging studies have suggested that older adults show declines in both sustained and transient cognitive control processes. However, previous neuroimaging studies have primarily focused on age-related change in the magnitude, but not temporal dynamics, of brain activity. The present study compared brain activity dynamics in healthy old and young adults during task switching. A mixed blocked/event-related functional magnetic resonance imaging design enabled separation of transient and sustained neural activity associated with cognitive control. Relative to young adults, older adults exhibited not only decreased sustained activity in the anterior prefrontal cortex (aPFC) during task-switching blocks but also increased transient activity on task-switch trials. Another pattern of age-related shift in dynamics was present in the lateral PFC (lPFC) and posterior parietal cortex (PPC), with younger adults showing a cue-related response during task-switch trials in lPFC and PPC, whereas older adults exhibited switch-related activation during the cue period in PPC only. In all 3 regions, these qualitatively distinct patterns of brain activity predicted qualitatively distinct patterns of behavioral performance across the 2 age groups. Together, these results suggest that older adults may shift from a proactive to reactive cognitive control strategy as a means of retaining relatively preserved behavioral performance in the face of age-related neurocognitive changes.

title: Cognitive control, goal maintenance, and prefrontal function in healthy aging.
abstract: Cognitive control impairments in healthy older adults may partly reflect disturbances in the ability to actively maintain goal-relevant information, a function that depends on the engagement of lateral prefrontal cortex (PFC). In 2 functional magnetic resonance imaging studies, healthy young and older adults performed versions of a task in which contextual cues provide goal-relevant information used to bias processing of subsequent ambiguous probes. In Study 1, a blocked design and manipulation of the cue-probe delay interval revealed a generalized pattern of enhanced task-related brain activity in older adults but combined with a specific delay-related reduction of activity in lateral PFC regions. In Study 2, a combined blocked/event-related design revealed enhanced sustained (i.e., across-trial) activity but a reduction in transient trial-related activation in lateral PFC among older adults. Further analyses of within-trial activity dynamics indicated that, within these and other lateral PFC regions, older adults showed reduced activation during the cue and delay period but increased activation at the time of the probe, particularly on high-interference trials. These results are consistent with the hypothesis that age-related impairments in goal maintenance abilities cause a compensatory shift in older adults from a proactive (seen in young adults) to a reactive cognitive control strategy.

title: Structural correlates of prospective memory
abstract: 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.

title: The neuropsychology of prospective memory in normal aging: A componential approach
abstract: To guide understanding of the neuropsychology of prospective memory and aging, we highlight several components of prospective memory, including planning an intended action, retrieving the action at the appropriate moment, and executing the action. We posit that frontal systems are particularly important for prospective memory tasks that require planning, that require strategic monitoring to detect the appropriate moment for executing the prospective memory intention, or for which execution of the retrieved intention must be delayed briefly. Drawing from a variety of approaches, including neuroimaging (with young adults) and studies examining individual differences relating to frontal functioning, we assemble preliminary evidence that supports this hypothesis. Further, because aging especially disrupts frontal functioning, the above noted prospective memory tasks would thus be expected to display the greatest age-related decline. The available literature confirms this expectation. A second key hypothesis is that some prospective memory tasks--those requiring minimal planning and supporting spontaneous retrieval--do not rely extensively on frontal processes but instead rely on medial-temporal structures for reflexive retrieval. These prospective memory tasks tend to show minimal or no age-related decline. The literature, though sparse with regard to the neuropsychological underpinnings of this kind of prospective memory task, is consistent with the present hypothesis.

title: Focal and nonfocal prospective memory performance in very mild dementia: a signature decline.
abstract: In a recent study, performance on a certain kind of prospective memory task (PM), labeled focal PM, was sensitive to the very early stages of Alzheimer's disease (AD; Duchek, Balota, & Cortese, 2006). This study sought to replicate and extend these findings by investigating both focal and nonfocal PM, as well as possible influences of alleles of the apolipoprotein E (ApoE) gene.



Thirty-five healthy older adults and 33 adults in the very earliest stages of AD, as determined by the clinical dementia rating scale, completed both focal and nonfocal PM tasks. Performance on these tasks has been linked to qualitatively different cognitive processes (Scullin, McDaniel, Shelton, & Lee, 2010), thereby providing leverage to illuminate the specific processes that underlie PM failures in very early AD. Approximately half of the adults in each group were ApoE e4 carriers and half were noncarriers. We also obtained participants' scores on a battery of standard psychometric tests.



There was a significant interaction between the type of PM task and dementia status, p < .05, ηp² = .12, demonstrating that the AD-related decline was more robust for focal than for nonfocal PM. Further, focal PM performance significantly discriminated between the very earliest stages of AD and normal aging, explaining variance unique to that explained by typical psychometric indices. ApoE status, however, was not associated with PM performance.



The pronounced deficit observed in the focal PM task suggests that spontaneous retrieval processes may be compromised in very early AD.

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

title: Prospective memory in Parkinson disease across laboratory and self-reported everyday performance.
abstract: Prospective memory is a complex cognitive construct ubiquitous in everyday life that is thought to sometimes rely on executive skills commonly affected by Parkinson's disease (PD). The present study investigated the effect of PD on prospective memory tasks with varying demand on executive control processes, namely on the amount of strategic attentional monitoring required for intention retrieval. Individuals with PD but without dementia and healthy adults performed laboratory event-based prospective memory tasks that varied in whether strategic attentional monitoring (nonfocal condition) or spontaneous processes (focal condition) were primarily involved in intention retrieval. Participants also completed a questionnaire rating their frequency of prospective memory failures in everyday life for both self-cued and environment-cued tasks. PD participants performed worse than non-PD participants in the nonfocal, but not focal, condition of the laboratory task. They also reported more everyday failures than non-PD participants for self-cued, but not environment-cued, prospective memory tasks. Thus, nondemented individuals with PD are preferentially impaired on prospective memory tasks for which higher levels of executive control are needed to support intention retrieval. This pattern is consistent across laboratory and reported real-world performance.

title: Differential neural activity in the recognition of old versus new events: An Activation Likelihood Estimation Meta‐Analysis
abstract: This study presents a meta‐analysis comparing hit and correct rejection (CR) conditions across 48 fMRI studies. Old/new (hit > CR) effects associated most consistently with (1) components of the default‐mode network, including the left angular gyrus, bilateral precuneus, and bilateral posterior cingulate regions, which may support the mental re‐experiencing of an old event, or ecphory; (2) components of the cognitive‐control network, involving the left dorsolateral and dorsomedial prefrontal cortex and bilateral intraparietal sulcus regions, which may mediate memory and non‐memory control functions; and (3) the caudate nucleus, a key part of the brain's reward system that may support the satisfaction tied to target‐detection. Direct comparisons of old/new effects between item versus source retrieval and “remember” versus “know” retrieval yielded three main sets of findings. First, default‐mode network regions showed greater old/new effects in conditions associated with richer ecphoric processing. Second, cognitive‐control network regions showed greater old/new effects in conditions associated with a greater demand for strategic‐retrieval processing. Third, the caudate nucleus showed greater old/new effects in conditions tied to greater confidence in target‐detection. New/old (CR > hit) effects most strongly associated with the bilateral medial temporal lobe, possibly reflecting greater encoding‐related activity for new than for old items, and the right posterior middle temporal regions, possibly reflecting repetition‐related neural priming for old items. In conclusion, neural activity distinguishing old from new events comprises an ensemble of multiple memory‐specific activities, including encoding, retrieval, and priming, as well as multiple types of more general cognitive activities, including default‐mode, cognitive‐control, and reward processing.

title: Laboratory-based and autobiographical retrieval tasks differ substantially in their neural substrates
abstract: In designing experiments to investigate retrieval of event memory, researchers choose between utilizing laboratory-based methods (in which to-be-remembered materials are presented to participants) and autobiographical approaches (in which the to-be-remembered materials are events from the participant's pre-experimental life). In practice, most laboratory studies have utilized old/new recognition memory, and most autobiographical memory studies have used the Galton-Crovitz word cueing technique [Crovitz, H.F., & Schiffman, H. (1974). Frequency of episodic memories as a function of their age. Bulletin of the Psychonomic Society, 4, 517-518]. What are the implications of these methodological choices for understanding the component processes and underlying neural substrates of memory retrieval? An Activation Likelihood Estimation (ALE) meta-analysis procedure [Turkeltaub, P., Eden, G., Jones, K., & Zeffiro, TA. (2002). Meta-analysis of the functional neuroanatomy of single-word reading: Method and validation. NeuroImage, 16, 765-780] was used to construct two whole-brain statistical maps: one showing brain regions that are consistently implicated when the task utilized is old/new recognition memory and one showing regions that tend to emerge when autobiographical event memory is queried. A comparison of the two maps shows very few regions of overlap. This basic methodological choice has a profound impact on the conclusions reached regarding human memory retrieval and its neural substrates.

title: A Parcellation Scheme for Human Left Lateral Parietal Cortex
abstract: The parietal lobe has long been viewed as a collection of architectonic and functional subdivisions. Though much parietal research has focused on mechanisms of visuospatial attention and control-related processes, more recent functional neuroimaging studies of memory retrieval have reported greater activity in left lateral parietal cortex (LLPC) when items are correctly identified as previously studied ("old") versus unstudied ("new"). These studies have suggested functional divisions within LLPC that may provide distinct contributions toward recognition memory judgments. Here, we define regions within LLPC by developing a parcellation scheme that integrates data from resting-state functional connectivity MRI and functional MRI. This combined approach results in a 6-fold parcellation of LLPC based on the presence (or absence) of memory-retrieval-related activity, dissociations in the profile of task-evoked time courses, and membership in large-scale brain networks. This parcellation should serve as a roadmap for future investigations aimed at understanding LLPC function.

title: Event-related fMRI studies of episodic encoding and retrieval: Meta-analyses using activation likelihood estimation
abstract: The recent surge in event-related fMRI studies of episodic memory has generated a wealth of information about the neural correlates of encoding and retrieval processes. However, interpretation of individual studies is hampered by methodological differences, and by the fact that sample sizes are typically small. We submitted results from studies of episodic memory in healthy young adults, published between 1998 and 2007, to a voxel-wise quantitative meta-analysis using activation likelihood estimation [Laird, A. R., McMillan, K. M., Lancaster, J. L., Kochunov, P., Turkeltaub, P. E., & Pardo, J. V., et al. (2005). A comparison of label-based review and ALE meta-analysis in the stroop task. Human Brain Mapping, 25, 6-21]. We conducted separate meta-analyses for four contrasts of interest: episodic encoding success as measured in the subsequent-memory paradigm (subsequent Hit vs. Miss), episodic retrieval success (Hit vs. Correct Rejection), objective recollection (e.g., Source Hit vs. Item Hit), and subjective recollection (e.g., Remember vs. Know). Concordance maps revealed significant cross-study overlap for each contrast. In each case, the left hemisphere showed greater concordance than the right hemisphere. Both encoding and retrieval success were associated with activation in medial-temporal, prefrontal, and parietal regions. Left ventrolateral prefrontal cortex (PFC) and medial-temporal regions were more strongly involved in encoding, whereas left superior parietal and dorsolateral and anterior PFC regions were more strongly involved in retrieval. Objective recollection was associated with activation in multiple PFC regions, as well as multiple posterior parietal and medial-temporal areas, but not hippocampus. Subjective recollection, in contrast, showed left hippocampal involvement. In summary, these results identify broadly consistent activation patterns associated with episodic encoding and retrieval, and subjective and objective recollection, but also subtle differences among these processes.

title: Cognitive contributions of the ventral parietal cortex: an integrative theoretical account
abstract: Although ventral parietal cortex (VPC) activations can be found in a variety of cognitive domains, these activations have been typically attributed to cognitive operations specific to each domain. In this article, we propose a hypothesis that can account for VPC activations across all the cognitive domains reviewed. We first review VPC activations in the domains of perceptual and motor reorienting, episodic memory retrieval, language and number processing, theory of mind, and episodic memory encoding. Then, we consider the localization of VPC activations across domains and conclude that they are largely overlapping with some differences around the edges. Finally, we assess how well four different hypotheses of VPC function can explain findings in various domains and conclude that a bottom-up attention hypothesis provides the most complete and parsimonious account.

title: Parietal lobe contributions to episodic memory retrieval
abstract: Although the parietal lobe is not traditionally thought to support declarative memory, recent event-related fMRI studies of episodic retrieval have consistently revealed a range of memory-related influences on activation in lateral posterior parietal cortex (PPC) and precuneus extending into posterior cingulate and retrosplenial cortex. This article surveys the fMRI literature on PPC activation during remembering, a literature that complements earlier electroencephalography data. We consider these recent memory-related fMRI responses within the context of classical ideas about parietal function that emphasize space-based attention and motor intention. We conclude by proposing three hypotheses concerning how parietal cortex might contribute to memory.

title: A parietal memory network revealed by multiple MRI methods
abstract: The manner by which the human brain learns and recognizes stimuli is a matter of ongoing investigation. Through examination of meta-analyses of task-based functional MRI and resting state functional connectivity MRI, we identified a novel network strongly related to learning and memory. Activity within this network at encoding predicts subsequent item memory, and at retrieval differs for recognized and unrecognized items. The direction of activity flips as a function of recent history: from deactivation for novel stimuli to activation for stimuli that are familiar due to recent exposure. We term this network the 'parietal memory network' (PMN) to reflect its broad involvement in human memory processing. We provide a preliminary framework for understanding the key functional properties of the network.

title: The functional neuroanatomy of spontaneous retrieval and strategic monitoring of delayed intentions
abstract: An intention stored in prospective memory (PM) for later execution can be retrieved either strategically through preparatory attentional processes such as active monitoring for PM targets or spontaneously through automatic retrieval processes when encountering a relevant cue. Using functional MRI to identify distinct brain areas involved in spontaneous retrieval of intentions and to dissociate them from monitoring-related processes, we compared brain activity in PM blocks in which subjects had to maintain and execute an intention in response to rarely occurring PM cues with blocks in which the previous intention had been completed. Although the PM task incurred performance costs in the ongoing task and was associated with increased block-related activation in the rostro-lateral prefrontal cortex (RLPFC), performance costs and RLPFC activation were no longer observed after the intention had been completed, providing further evidence for an involvement of RLPFC in strategic monitoring during PM tasks. By contrast, event-related activation induced by PM cues was observed in the ventral parietal cortex (VPC), precuneus and posterior cingulate cortex even after the intention was completed. These activations are consistent with the notion of spontaneous intention retrieval possibly mediated through a bottom-up driven re-activation of intention representations still persisting in a heightened state of activation in episodic memory. In conclusion, the results highlight the functional relevance of VPC and precuneus in prospective memory retrieval, possibly reflecting spontaneous, cue-based processes as opposed to top-down controlled strategic monitoring.

title: Characterizing Evoked Hemodynamics with fMRI
abstract: We describe an implementation of the general linear model that facilitates the characterization of evoked hemodynamic responses to sensorimotor or cognitive processing, when the exact form of these responses is not known. The importance of this approach is that one can test for differential responses among tasks that may elude more conventional analyses. In particular, we suppose that an evoked response has early and late components and that a differential response may involve (i) both components to the same degree, as in a conventional "activation" or (ii) differential expression of the early and late components in two tasks, as might be seen in differential adaptation, or differences associated with the tasks (e.g., requiring and not requiring sustained attention). Using this approach we were able to demonstrate that the anterior cingulate differentiates, in terms of its response, between two motor tasks that did and did not require sustained attention. This differential response was observed even though there was no classical "activation" (i.e., there was no difference in the mean activity associated with the two conditions). It is suggested that these demonstration results point to the possibility of making greater use of the temporal resolution afforded by fast fMRI techniques.

title: Separating neural processes using mixed event-related and epoch-based fMRI paradigms
abstract: Mixed event-related and epoch-based paradigms (mixed designs) have recently been introduced as viable experimental designs for fMRI studies. To date, mixed designs have been used only to evaluate transient and state changes that are associated with single event and blocked conditions, respectively. However, no study exists that demonstrates that the regional activity associated with two distinct processes with known activation patterns can be adequately separated. Rapid event-related experimental designs use the principles of linear summation and can identify multiple distinct processes that are not overlapping in time through linear regression. Events and epochs that are also separated in time can be easily distinguished using the same general linear model (GLM) and a multiple regression analysis. However, it may not be so obvious that events that are superimposed in time onto epochs can also theoretically be separated using this technique. We used the principles of linear summation and the GLM to demonstrate that regional activity from a mixed design with visual epochs and auditory events superimposed in time can in fact be separated. In addition, the flexibility of mixed designs is explored using a paradigm that includes events throughout the on and off blocks of the epoch-based paradigm. Mixed designs provide neuroscientists with the power and flexibility to address more complex cognitive hypotheses that were otherwise difficult to study with either epoch-based or event-related designs alone.

title: Distinct neural circuits support transient and sustained processes in prospective memory and working memory.
abstract: Current theories are divided as to whether prospective memory (PM) involves primarily sustained processes such as strategic monitoring, or transient processes such as the retrieval of intentions from memory when a relevant cue is encountered. The current study examined the neural correlates of PM using a functional magnetic resonance imaging design that allows for the decomposition of brain activity into sustained and transient components. Performance of the PM task was primarily associated with sustained responses in a network including anterior prefrontal cortex (lateral Brodmann area 10), and these responses were dissociable from sustained responses associated with active maintenance in working memory. Additionally, the sustained responses in anterior prefrontal cortex correlated with faster response times for prospective responses. Prospective cues also elicited selective transient activity in a region of interest along the right middle temporal gyrus. The results support the conclusion that both sustained and transient processes contribute to efficient PM and provide novel constraints on the functional role of anterior PFC in higher-order cognition.

title: Mixed blocked/event-related designs separate transient and sustained activity in fMRI
abstract: Recent functional magnetic resonance imaging (fMRI) studies using mixed blocked/event-related designs have shown activity consistent with separable sustained task-related processes and transient trial-related processes. In the mixed design, control blocks are intermixed with task blocks, during which trials are presented at varying intervals. Two studies were conducted to assess the ability of this design to detect and dissociate sustained task-related from transient trial-related activity. Analyses on both simulated and empirical data were performed by using the general linear model with a shape assumed for sustained effects, but not transient effects. In the first study, simulated data were produced with sustained time courses, transient time courses, and the sum of both together. Analyses of these data showed appropriate parsing of sustained and transient activity in all three cases. For the empirical fMRI experiment, counterphase-flickering checkerboard stimuli were constructed to produce sustained, transient, and combined sustained and transient responses in visual cortex. As with the simulation, appropriate parsing of sustained and transient activity was seen in all three cases; i.e., sustained stimuli produced sustained time courses and transient stimuli produced transient time courses. Combined stimuli produced both transient and sustained time courses. Critically, transient stimuli alone did not produce spurious positive sustained responses; sustained stimuli alone produced negligible spurious transient time courses. The results of these two studies along with supplemental simulations provide strong evidence that mixed designs are an effective tool for separating transient, trial-related activity from sustained activity in fMRI experiments. Mixed designs can allow researchers a means to examine brain activity associated with sustained processes, potentially related to task-level control signals.

title: Functional Specialization within Rostral Prefrontal Cortex (Area 10): A Meta-analysis
abstract: One of the least well understood regions of the human brain is rostral prefrontal cortex, approximating Brodmann's area 10. Here, we investigate the possibility that there are functional subdivisions within this region by conducting a meta-analysis of 104 functional neuroimaging studies (using positron emission tomography/functional magnetic resonance imaging). Studies involving working memory and episodic memory retrieval were disproportionately associated with lateral activations, whereas studies involving mentalizing (i.e., attending to one's own emotions and mental states or those of other agents) were disproportionately associated with medial activations. Functional variation was also observed along a rostral-caudal axis, with studies involving mentalizing yielding relatively caudal activations and studies involving multiple-task coordination yielding relatively rostral activations. A classification algorithm was trained to predict the task, given the coordinates of each activation peak. Performance was well above chance levels (74% for the three most common tasks; 45% across all eight tasks investigated) and generalized to data not included in the training set. These results point to considerable functional segregation within rostral prefrontal cortex.

title: Psychophysiological and Modulatory Interactions in Neuroimaging
abstract: In this paper we introduce the idea of explaining responses, in one cortical area, in terms of an interaction between the influence of another area and some experimental (sensory or task-related) parameter. We refer to these effects as psychophysiological interactions and relate them to interactions based solely on experimental factors (i.e., psychological interactions), in factorial designs, and interactions among neurophysiological measurements (i.e., physiological interactions). We have framed psychophysiological interactions in terms of functional integration by noting that the degree to which the activity in one area can be predicted, on the basis of activity in another, corresponds to the contribution of the second to the first, where this contribution can be related to effective connectivity. A psychophysiological interaction means that the contribution of one area to another changes significantly with the experimental or psychological context. Alternatively these interactions can be thought of as a contribution-dependent change in regional responses to an experimental or psychological factor. In other words the contribution can be thought of as modulating the responses elicited by a particular stimulus or psychological process. The potential importance of this approach lies in (i) conferring a degree of functional specificity on this aspect of effective connectivity and (ii) providing a model of modulation, where the contribution from a distal area can be considered to modulate responses to the psychological or stimulus-specific factor defining the interaction. Although distinct in neurobiological terms, these are equivalent perspectives on the same underlying interaction. We illustrate these points using a functional magnetic resonance imaging study of attention to visual motion and a position emission tomography study of visual priming. We focus on interactions among extrastriate, inferotemporal, and posterior parietal regions during visual processing, under different attentional and perceptual conditions.

title: A generalized form of context-dependent psychophysiological interactions (gPPI): A comparison to standard approaches
abstract: Functional MRI (fMRI) allows one to study task-related regional responses and task-dependent connectivity analysis using psychophysiological interaction (PPI) methods. The latter affords the additional opportunity to understand how brain regions interact in a task-dependent manner. The current implementation of PPI in Statistical Parametric Mapping (SPM8) is configured primarily to assess connectivity differences between two task conditions, when in practice fMRI tasks frequently employ more than two conditions. Here we evaluate how a generalized form of context-dependent PPI (gPPI; ), which is configured to automatically accommodate more than two task conditions in the same PPI model by spanning the entire experimental space, compares to the standard implementation in SPM8. These comparisons are made using both simulations and an empirical dataset. In the simulated dataset, we compare the interaction beta estimates to their expected values and model fit using the Akaike information criterion (AIC). We found that interaction beta estimates in gPPI were robust to different simulated data models, were not different from the expected beta value, and had better model fits than when using standard PPI (sPPI) methods. In the empirical dataset, we compare the model fit of the gPPI approach to sPPI. We found that the gPPI approach improved model fit compared to sPPI. There were several regions that became non-significant with gPPI. These regions all showed significantly better model fits with gPPI. Also, there were several regions where task-dependent connectivity was only detected using gPPI methods, also with improved model fit. Regions that were detected with all methods had more similar model fits. These results suggest that gPPI may have greater sensitivity and specificity than standard implementation in SPM. This notion is tempered slightly as there is no gold standard; however, data simulations with a known outcome support our conclusions about gPPI. In sum, the generalized form of context-dependent PPI approach has increased flexibility of statistical modeling, and potentially improves model fit, specificity to true negative findings, and sensitivity to true positive findings.

title: Dissociable Intrinsic Connectivity Networks for Salience Processing and Executive Control
abstract: Variations in neural circuitry, inherited or acquired, may underlie important individual differences in thought, feeling, and action patterns. Here, we used task-free connectivity analyses to isolate and characterize two distinct networks typically coactivated during functional MRI tasks. We identified a “salience network,” anchored by dorsal anterior cingulate (dACC) and orbital frontoinsular cortices with robust connectivity to subcortical and limbic structures, and an “executive-control network” that links dorsolateral frontal and parietal neocortices. These intrinsic connectivity networks showed dissociable correlations with functions measured outside the scanner. Prescan anxiety ratings correlated with intrinsic functional connectivity of the dACC node of the salience network, but with no region in the executive-control network, whereas executive task performance correlated with lateral parietal nodes of the executive-control network, but with no region in the salience network. Our findings suggest that task-free analysis of intrinsic connectivity networks may help elucidate the neural architectures that support fundamental aspects of human behavior.

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

title: Adult age differences in interference from a prospective-memory task: a diffusion model analysis
abstract: People often slow down their ongoing activities when they must remember an intended action, known as the cost or interference effect of prospective memory (PM). Only a few studies have examined adult age differences in PM interference, and the specific reasons underlying such differences are not well understood. The authors used a model-based approach to reveal processes underlying PM interference and age differences in these processes. Older and younger adults first performed a block of an ongoing lexical decision task alone. An embedded event-based PM task was added in a second block. Simultaneously accounting for the changes in response time distributions and error rates induced by the PM task, Ratcliff’s ( 1978) diffusion model was used to decompose the nonlinear combination of speed and accuracy into psychologically meaningful components. Remembering an intention not only reduced processing efficiency in both age groups, but also prolonged peripheral nondecision times and induced response cautiousness. Overall, the findings suggest that there are multiple, but qualitatively similar factors underlying PM task interference in both age groups.

title: Proceeding With Care for Successful Prospective Memory: Do We Delay Ongoing Responding or Actively Monitor for Cues?
abstract: In prospective memory (PM) research, costs (slowed responding to the ongoing task when a PM task is present relative to when it is not) have typically been interpreted as implicating an attentionally demanding monitoring process. To inform this interpretation, Heathcote, Loft, and Remington (2015), using an accumulator model, found that PM-related costs were associated with changes in a decision threshold parameter. This pattern was interpreted as disfavoring a monitoring process and supporting a non-capacity-consuming delayed responding strategy. The present study combined both behavioral and modeling techniques, as well as embedded parameter validation, to better illuminate the underlying processes involved in PM. We encouraged participants to use either a delayed responding or a monitoring strategy and used these conditions as anchor points for comparing a standard PM condition (with no strategy instructions). The monitoring strategy benefited PM more than did a delayed responding strategy. Most importantly, behaviors and modeling parameters associated with the standard PM instructions more closely reflected footprints of monitoring. Further, we found no individual model parameter that directly implicates monitoring behavior.

title: Hemispheric asymmetry reduction in older adults: the HAROLD model.
abstract: A model of the effects of aging on brain activity during cognitive performance is introduced. The model is called HAROLD (hemispheric asymmetry reduction in older adults), and it states that, under similar circumstances, prefrontal activity during cognitive performances tends to be less lateralized in older adults than in younger adults. The model is supported by functional neuroimaging and other evidence in the domains of episodic memory, semantic memory, working memory, perception, and inhibitory control. Age-related hemispheric asymmetry reductions may have a compensatory function or they may reflect a dedifferentiation process. They may have a cognitive or neural origin, and they may reflect regional or network mechanisms. The HAROLD model is a cognitive neuroscience model that integrates ideas and findings from psychology and neuroscience of aging.

title: Neurocognitive Aging and the Compensation Hypothesis
abstract: The most unexpected and intriguing result from functional brain imaging studies of cognitive aging is evidence for age-related overactivation: greater activation in older adults than in younger adults, even when performance is age-equivalent. Here we examine the hypothesis that age-related overactivation is compensatory and discuss the compensation-related utilization of neural circuits hypothesis (CRUNCH). We review evidence that favors a compensatory account, discuss questions about strategy differences, and consider the functions that may be served by overactive brain areas. Future research directed at neurocognitively informed training interventions may augment the potential for plasticity that persists into the later years of the human lifespan.

title: Que PASA? The posterior-anterior shift in aging.
abstract: A consistent finding from functional neuroimaging studies of cognitive aging is an age-related reduction in occipital activity coupled with increased frontal activity. This posterior-anterior shift in aging (PASA) has been typically attributed to functional compensation. The present functional magnetic resonance imaging sought to 1) confirm that PASA reflects the effects of aging rather than differences in task difficulty; 2) test the compensation hypothesis; and 3) investigate whether PASA generalizes to deactivations. Young and older participants were scanned during episodic retrieval and visual perceptual tasks, and age-related changes in brain activity common to both tasks were identified. The study yielded 3 main findings. First, inconsistent with a difficulty account, the PASA pattern was found across task and confidence levels when matching performance among groups. Second, supporting the compensatory hypothesis, age-related increases in frontal activity were positively correlated with performance and negatively correlated with the age-related occipital decreases. Age-related increases and correlations with parietal activity were also found. Finally, supporting the generalizability of the PASA pattern to deactivations, aging reduced deactivations in posterior midline cortex but increased deactivations in medial frontal cortex. Taken together, these findings demonstrate the validity, function, and generalizability of PASA, as well as its importance for the cognitive neuroscience of aging.

title: Where is ELSA? The early to late shift in aging.
abstract: Studies of cognitive and neural aging have recently provided evidence of a shift from an early- to late-onset cognitive control strategy, linked with temporally extended activity in the prefrontal cortex (PFC). It has been uncertain, however, whether this age-related shift is unique to PFC and executive control tasks or whether the functional location might vary depending on the particular cognitive processes that are altered. The present study tested whether an early-to-late shift in aging (ELSA) might emerge in the medial temporal lobes (MTL) during a protracted context memory task comprising both anticipatory cue (retrieval preparation) and retrieval probe (retrieval completion) phases. First, we found reduced MTL activity in older adults during the early retrieval preparation phase coupled with increased MTL activity during the late retrieval completion phase. Second, we found that functional connectivity between MTL and PFC regions was higher during retrieval preparation in young adults but higher during retrieval completion in older adults, suggesting an important interactive relationship between the ELSA pattern in MTL and PFC. Taken together, these results critically suggest that aging results in temporally lagged activity even in regions not typically associated with cognitive control, such as the MTL.

title: Importance effects on performance in event‐based prospective memory tasks
abstract: In the present study we manipulated the importance of performing two event‐based prospective memory tasks. In Experiment 1, the event‐based task was assumed to rely on relatively automatic processes, whereas in Experiment 2 the event‐based task was assumed to rely on a more demanding monitoring process. In contrast to the first experiment, the second experiment showed that importance had a positive effect on prospective memory performance. In addition, the occurrence of an importance effect on prospective memory performance seemed to be mainly due to the features of the prospective memory task itself, and not to the characteristics of the ongoing tasks that only influenced the size of the importance effect. The results suggest that importance instructions may improve prospective memory if the prospective task requires the strategic allocation of attentional monitoring resources.

title: The parietal cortex and episodic memory: an attentional account
abstract: The contribution of the parietal cortex to episodic memory is a fascinating scientific puzzle. On the one hand, parietal lesions do not normally yield severe episodic-memory deficits; on the other hand, parietal activations are seen frequently in functional-neuroimaging studies of episodic memory. A review of these two categories of evidence suggests that the answer to the puzzle requires us to distinguish between the contributions of dorsal and ventral parietal regions and between the influence of top-down and bottom-up attention on memory.

title: Target preexposure eliminates the effect of distraction on event-based prospective memory
abstract: Prospective memory is critical to everyday functioning and can be vulnerable to distraction. We conducted an experiment to explore whether we could buffer prospective memory against distraction. For half the participants, we preexposed stimuli that were later designated as prospective memory targets. Then, all participants performed an ongoing task (in which the prospective memory task was embedded) under standard and high attentional demand (i.e., under full and divided attention). Target preexposure improved prospective memory and eliminated the significant divided attention effect. Thus, target preexposure seems to buffer prospective memory against the disruptive effect of dividing attention. Moreover, target preexposure seemed to help participants to respond with the correct intended action. This result implies that preexposure to the target stimuli facilitated the encoding of an association between the target stimuli and the intended action, perhaps promoting relatively more reflexive retrieval and thereby buffering prospective memory against distraction.

title: Discrepancy processes in prospective memory retrieval
abstract: Discrepancy processes may be helpful in noticing prospective memory targets (McDaniel, Guynn, Einstein, & Breneiser, 2004). We manipulated the discrepancy of prospective memory targets from the processing coherence established by the ongoing task by preexposing nontarget items in the ongoing task either five times (high discrepancy) or two times (low discrepancy). Prospective memory performance was significantly better in the high-discrepancy group than in the low-discrepancy group. These results support a discrepancy view of prospective remembering.

title: Discrepancy-plus-search processes in prospective memory retrieval
abstract: In the present study, we investigated the processes underlying prospective memory (PM) retrieval, focusing specifically on two possible spontaneous processes: discrepancy-plus-search and familiarity. Discrepancy was elicited by orthogonally manipulating the processing difficulties of the PM targets and the nontargets. Participants performed a PM task while solving anagrams with two levels of difficulty (easy or difficult). Assuming that the ease of processing easy anagrams would heighten a sense of familiarity, the familiarity view predicted better PM performance with easy anagrams as the PM targets. In contrast, the discrepancy-plus-search view predicted higher PM performance for the PM targets that were anagrams whose difficulty level mismatched that of the surrounding nontargets, as compared to PM targets whose difficulty matched that of the surrounding nontargets. This prediction was based on the idea that mismatching rather than matching difficulty levels would create discrepancy, thereby signaling significance for the target. Participants were more likely to perform the PM task for PM targets that were discrepant, supporting the discrepancy-plus-search view.

title: Cue-focused and reflexive-associative processes in prospective memory retrieval.
abstract: Several theories of event-based prospective memory were evaluated in 3 experiments. The results depended on the association between the target event and the intended action. For associated target-action pairs (a) preexposure of nontargets did not reduce prospective memory, (b) divided attention did not reduce prospective memory, (c) prospective memory was better than when the target event and intended action were not associated, and (d) prospective memory was characterized by retrieval of the precise intended action. These results converge on the view that retrieval is mediated by a reflexive-associative process. In contrast, for unassociated pairs (a) preexposure of nontargets reduced prospective memory, and (b) divided attention reduced prospective memory. These results implicate cue-focused retrieval processes and are most consistent with a discrepancy-plus-search model. The entire pattern implicates both cue-focused and reflexive-associative processes and more generally supports a multiprocess framework of prospective memory (M. A. McDaniel & G. O. Einstein, 2000).

title: The discrepancy-attribution hypothesis: I. The heuristic basis of feelings of familiarity.
abstract: B. W. A. Whittlesea and L. D. Williams (1998, 2000) proposed the discrepancy-attribution hypothesis to explain the source of feelings of familiarity. By that hypothesis, people chronically evaluate the coherence of their processing. When the quality of processing is perceived as being discrepant from that which could be expected, people engage in an attributional process; the feeling of familiarity occurs when perceived discrepancy is attributed to prior experience. In the present article, the authors provide convergent evidence for that hypothesis and show that it can also explain feelings of familiarity for nonlinguistic stimuli. They demonstrate that the perception of discrepancy is not automatic but instead depends critically on the attitude that people adopt toward their processing, given the task and context. The connection between the discrepancy-attribution hypothesis and the "revelation effect" is also explored (e.g., D. L. Westerman & R. L. Greene, 1996).

title: The gateway hypothesis of rostral prefrontal cortex (area 10) function
abstract: Rostral prefrontal cortex (PFC) is a large brain region, and is unusually large in humans. Therefore, it seems likely that it might support functions that are central to cognition. However, until recently, almost nothing was known about what these functions might be. The 'gateway hypothesis' places these abilities at the centre of human mental processing. It maintains that rostral PFC supports mechanisms that enable us to attend, to a novel degree, either to environmental stimuli, or by contrast, to self-generated or maintained representations (i.e. the 'thoughts in our head'). In this way, investigations into the functions of rostral PFC will reveal key new insights into how human and non-human mental abilities differ.