Reduced mind-wandering in Mild Cognitive Impairment: Testing the spontaneous retrieval deficit hypothesis

© American Psychological Association, 2018. This paper is not the copy of record and may not exactly replicate the authoritative document published in the APA journal. Please do not copy or cite without author's permission. The final article is available, upon publication, at: http://dx.doi.org/10.1037/neu0000457Objective: Research on early cognitive markers of Alzheimer's disease (AD) is primarily focused on declarative episodic memory tests that involve deliberate and effortful/strategic processes at retrieval. The present study tested the spontaneous retrieval deficit hypothesis, which predicts that people with amnestic mild cognitive impairment (aMCI), who are at increased risk of developing AD, are particularly impaired on tasks that rely on spontaneous retrieval processes. Method: Twenty-three participants with aMCI and 25 healthy controls (HC) completed an easy vigilance task and thought probes (reporting what was going through their mind), which were categorized as spontaneous thoughts about the past (i.e., involuntary memories), current situation, and future (i.e., spontaneous prospection). Results: Participants with aMCI reported significantly fewer spontaneous thoughts or mind-wandering than HC. This effect was driven by significantly fewer involuntary memories, although groups did not differ in the number of current and future thoughts. Conclusions: Findings provide strong support for the spontaneous retrieval deficit hypothesis. Implications for research on mind-wandering and the default network, early cognitive markers of the disease, and our theoretical understanding of the nature of cognitive deficits in AD are discussed.Peer reviewe

Age-related differences in mind-wandering in daily life

In recent years, several laboratory studies have indicated that healthy older adults exhibit a reduction in mind-wandering frequency compared with young adults. However, it is unclear if these findings extend to daily life settings. In the current study, using experience sampling over the course of a week in the daily life of 31 young and 20 older adults, we assessed age-related differences in: (a) mind-wandering frequency, (b) the relationship between affect and mind-wandering frequency, and (c) content of mind wandering. Older adults mind wandered less than young adults in daily life. Across age groups, negative affect was positively associated with mind-wandering occurrence. Finally, older adults reported that their thoughts were more pleasant, interesting, and clear compared with young adults, who had thoughts that were more dreamlike, novel, strange, and racing. Our results provide the first demonstration using thought sampling that older adults exhibit a reduction in mind-wandering frequency in daily life. Implications for current theories of age-related reductions in mind-wandering frequency are discussed

Development of abstract thinking during childhood and adolescence: the role of rostrolateral prefrontal cortex

Rostral prefrontal cortex (RPFC) has increased in size and changed in terms of its cellular organisation during primate evolution. In parallel emerged the ability to detach oneself from the immediate environment to process abstract thoughts and solve problems and to understand other individuals’ thoughts and intentions. Rostrolateral prefrontal cortex (RLPFC) is thought to play an important role in supporting the integration of abstract, often self-generated, thoughts. Thoughts can be temporally abstract and relate to long term goals, or past or future events, or relationally abstract and focus on the relationships between representations rather than simple stimulus features. Behavioural studies have provided evidence of a prolonged development of the cognitive functions associated with RLPFC, in particular logical and relational reasoning, but also episodic memory retrieval and prospective memory. Functional and structural neuroimaging studies provide further support for a prolonged development of RLPFC during adolescence, with some evidence of increased specialisation of RLPFC activation for relational integration and aspects of episodic memory retrieval. Topics for future research will be discussed, such as the role of medial RPFC in processing abstract thoughts in the social domain, the possibility of training abstract thinking in the domain of reasoning, and links to education

Vascular Risk, Functional Connectivity, and Episodic Memory in Older Adults

Resting-state functional magnetic resonance imaging and functional connectivity (FC) analyses are used to explore functional brain networks underlying a diverse array of abilities. Functional networks are composed of regions throughout the brain whose activity is closely linked to form a coherent network. One functional network, the default mode network (DMN), is thought to subserve self-referential thought and autobiographical memory. DMN regions include the ventromedial prefrontal cortex, inferior parietal lobe, hippocampus, and the primary hub of this network, the posterior cingulate cortex (PCC). For reasons yet unknown, DMN FC declines in aging, which is associated with memory impairment. Vascular risk may be an important contributor to age-related DMN disruption through its effects on gray and white matter integrity. The present study examined relationships among vascular risk, DMN FC, and episodic memory in older adults using FC analyses and structural equation modeling. Several regions found to be functionally related to the PCC were those identified in prior research on the DMN, but also included areas not typically implicated in the DMN, such as the cerebellum and basal ganglia. Stronger FC between the PCC and parahippocampal gyrus predicted better memory performance, confirming the importance of medial temporal lobe structures for memory. FC between the PCC and several other areas, such as the cerebellum, basal ganglia, and limbic regions, also predicted memory performance, suggesting the importance of executive functioning and emotion for memory in aging. Correlations between FC and vascular risk were found in the basal ganglia, cerebellum, and inferior temporal gyrus, suggesting vascular risk may modify associations between the DMN and cortical and subcortical regions. Finally, a mediational model was tested in which DMN FC mediated the relationship between vascular risk and memory. This was compared to an alternative model with depressive symptoms as a mediator. Vascular risk was unrelated to memory and DMN FC in all models, while stronger DMN FC predicted poorer memory performance. Neither DMN FC nor depressive symptoms acted as mediators. The impact of vascular risk on the DMN in aging should be further explored using a comprehensive multimethod approach, along with other potential causes of age-related DMN disruption

Alpha suppression as a neural marker of task demands in voluntary vs involuntary retrieval in older and younger adults

Voluntary episodic memory relies on intentionally controlled retrieval, while involuntary episodic memory comes to mind automatically. Consistent with findings of reduced cognitive control with age, recent work suggests that voluntary memory declines with age while involuntary memory is relatively preserved. However, the neurophysiology underlying these age differences has yet to be established. The current study used EEG to test 31 young and 35 older adults during voluntary vs. involuntary retrieval (manipulated between-subjects). Participants first encoded sounds, half of which were paired with pictures, the other half unpaired. EEG was then recorded as they listened to the sounds, with participants in the involuntary group performing a sound localization task, and those in the voluntary group additionally attempting to recall the associated pictures. Participants later retrospectively reported which sounds brought the paired picture to mind during the sound task. Older adults said they remembered as many pictures as young adults, but their objective memory was lower on a final cued recall test. For the EEG analysis, older adults showed greater alpha event-related desynchronization (ERD; a neural marker of memory reactivation) for paired than unpaired sounds at occipital sites, possibly reflecting visual reactivation of the associated pictures. Young adults did not show memory-related alpha ERD effects. However, young adults did show greater alpha ERD during voluntary than involuntary retrieval at frontal and occipital sites, while older adults showed pronounced alpha ERD (indicative of effortful retrieval) regardless of condition. These data suggest that alpha ERD can be used as a neural marker of memory in older adults; however, a more naturalistic paradigm may be required to study true involuntary memory with age

From Cue to Recall : The Temporal Dynamics of Long-Term Memory Retrieval

A fundamental function of long-term memory is the ability to retrieve a specific memory when encountering a retrieval cue. The purpose of this dissertation was to further our understanding of such cued recall by investigating the temporal dynamics from the presentation of the retrieval cue until the target memory is recalled. Retrieval cues are often related with several memories. When such a retrieval cue is presented, the associated memories will compete for retrieval and this retrieval competition needs to be handled in order to retrieve the sought after target memory. Study 1 and Study 2 investigated the temporal dynamics of such competitive semantic cued recall. Interestingly, previous research has shown that the ability to retrieve the currently relevant target memory comes with a cost, namely retrieval-induced forgetting of the competing memories. These studies also investigated the role of competitor activation and target retrieval in this forgetting phenomenon. Study 1 investigated the electrophysiological correlates of reactivation of competing currently irrelevant memories and the role of such competitor activation in retrieval-induced forgetting. Competitor activation was related to an FN400 event-related potential (ERP) effect and this effect predicted increased levels of retrieval-induced forgetting, indicating that this forgetting effect is dependent on competitor activation. Study 2 examined processes involved in target retrieval in a similar competitive semantic cued recall task. The main finding in this study was that attempts to retrieve the target memory were related to a late posterior negativity ERP effect. Another important finding was that behavioural and ERP measures of target retrieval were unrelated to retrieval-induced forgetting. Retrieval cues can sometimes elicit involuntary retrieval of unwanted memories. Such memory intrusions are a core symptom of post-traumatic stress disorder. Study 3 investigated the temporal dynamics of such memory intrusions. One of the key findings was that memory intrusions were related to a negative slow wave ERP effect possibly reflecting the activation of the intruding memory in working memory. Taken together the findings in the dissertation indicate that cued recall involves several cognitive processes ranging from early automatic memory reactivation to conscious processes such as working memory activation and recollection. The findings have implications for cognitive theories of memory and have relevance for several clinical conditions including depression and post-traumatic stress disorder

Task interference effects in prospective memory

Prospective memory (PM), or remembering to remember, is biq it s i p pl ’s liv s a d PM misses might represent around half of daily memory failures according to recent research. In this thesis, several intention-related factors were investigated in order to clarify and elaborate our understanding of the effects of working memory (WM) and cognitive aging on prospective remembering, increase theoretical clarity regarding the dynamics of the monitoring processes in PM tasks, and investigate the interplay between two qualitatively different PM retrieval processes (i.e., spontaneous retrieval and monitoring). The overall approach was to examine how holding a particular intention affected ongoing task performance in a series of specifically devised laboratory studies of PM. The main findings of this thesis can be summarized as follows: First, encountering intention-related information boosted nonfocal PM performance for low, but not high, WM young adults, and did so without any additional cost to ongoing task performance (Experiment 1). Second, presenting intention-related information as distractor items improved PM performance for older, but not young adults (Experiments 2 and 3). The benefit was most likely due to distractor lures enhancing the salience of the target events and triggering spontaneous retrieval of the intention, or alternatively (or additionally), triggering (functional) monitoring in close proximity to the target events (Experiment 2). Third, practicing the ongoing activity prior to encoding the PM task enhanced nonfocal target detection for high WM young adults, but not for low WM young adults and older adults; practice probably allowed individuals to encode a more elaborate and detailed representation of the PM task (Experiment 4). Fourth, explicit information about target-defining features led to trial-by-trial modulations in task interference as a function of stimulus relevance for the nonfocal PM task. The effect was observed when relevant and irrelevant stimuli varied at random with no cuing (Experiments 5 and 6) and when presentation was blocked (Experiment 5), and was most likely associated with the action of top-down attentional control. Fifth, implicit information about the PM task demands also aff ct d pa ticipa ts’ ff t a d s cc ss i the PM task. Moreover, experience with the PM targets triggered local changes in attention allocation when actual demands were higher than expected (Experiment 7). And sixth, target repetition within a set boosted PM performance by stimulating retrieval through spontaneous retrieval processes, and optimized performance relative to when retrieval relied mostly on monitoring processes alone (Experiment 8). In summary, the present work uncovered several factors that have the potential to boost prospective remembering, as well as influence the extent to which monitoring processes are engaged and/or the type of processing required to support PM retrieval

Acute Exercise and Creativity: Embodied Cognition Approaches

This dissertation manuscript is the culmination of three years of research examining several unique, exercise-induced mechanisms underlying creativity. This collection of work addresses historical and current empirical concepts of creativity in a narrative review, providing recommendations for future research. Several reviews follow this introduction, highlighting the proposed effects of exercise on creativity, putative mechanisms for creativity, and the effects of exercise and embodied manipulations on creative behavior. Multiple experiments utilizing moderate-intensity exercise as a theoretical stimulus for higher-order cognitions were conducted to investigate associations between exercise and creativity, which lead to the final dissertation experiment. The dissertation experiment was the first to provide statistically significant evidence for acute, moderate-intensity treadmill exercise coupled with anagram problem-solving to prime subsequent RAT completion compared to a non-exercise, priming only condition. We emphasize that the additive effects of exercise plus priming may be a viable strategy for enhancing verbal convergent creativity. Future research is warranted to explore a variety of priming effects on the relationship between exercise, embodied interventions, and creativityThis dissertation manuscript is the culmination of three years of research examining several unique, exercise-induced mechanisms underlying creativity. This collection of work addresses historical and current empirical concepts of creativity in a narrative review, providing recommendations for future research. Several reviews follow this introduction, highlighting the proposed effects of exercise on creativity, putative mechanisms for creativity, and the effects of exercise and embodied manipulations on creative behavior. Multiple experiments utilizing moderate-intensity exercise as a theoretical stimulus for higher-order cognitions were conducted to investigate associations between exercise and creativity, which lead to the final dissertation experiment. The dissertation experiment was the first to provide statistically significant evidence for acute, moderate-intensity treadmill exercise coupled with anagram problem-solving to prime subsequent RAT completion compared to a non-exercise, priming only condition. We emphasize that the additive effects of exercise plus priming may be a viable strategy for enhancing verbal convergent creativity. Future research is warranted to explore a variety of priming effects on the relationship between exercise, embodied interventions, and creativit

The source of the associative deficit in aging: the role of attentional resources for processing relational information

Previous studies have proposed an associative deficit hypothesis, which attributes part of older adults' deficient episodic memory performance to their difficulty in creating cohesive episodes. According to the ADH, older adults show disproportionate deficits in relational memory (RM) relative to item memory (IM). The disproportionate RM deficit in older adults has been demonstrated with a variety of memory tasks, such as word-word, word-font, and face-name pairs. Despite rich evidence of an age-related RM deficit, the source of this deficit remains unspecified. One of the most widely investigated factors is the reduction in attentional resources in older adults. To investigate the effect of reduced attentional resources on RM performance, previous researchers have imposed a secondary task load on young adults during encoding of memory lists to divide attentional resources into two different tasks. However, none of the existing studies have found a disproportionate RM impairment in young adults under divided attention conditions. The current project investigated whether a reduction in attentional resources for relational processing underlies the memory impairments observed in aging. Using behavioral and functional neuroimaging techniques, I conducted three studies aimed at determining: 1) whether imposing a secondary task load for relational processing makes young adults' memory performance mimic the age-related RM deficit, and 2) whether the effect of reduced attentional resources for relational processing on RM is similar to the effect of aging at the neural level, using functional magnetic resonance imaging (fMRI). The results from the two behavioral studies indicate that a reduction in attentional resources for relational processing in young adults during encoding equates their performance in RM to that of older adults. Furthermore, the results from the fMRI study demonstrate that both aging and reductions in relational attention processing in young adults significantly reduced activity in the brain areas critical for RM formation, namely, the ventrolateral and dorsolateral PFC, superior and inferior parietal regions, and left hippocampus. This converging evidence from behavioral and neuroimaging studies thus documents the first evidence that the reduction in attentional resources for relational processing is the critical factor for the age-related RM deficit

How often are thoughts metacognitive? Findings from research on self-regulated learning, think-aloud protocols, and mind-wandering

Metacognitive monitoring refers to how people evaluate their cognitive performance. An extensive literature examines how accurately individuals engage in monitoring. The question of how often individuals engage in metacognitive monitoring has been largely neglected, although one might expect situational, group, and individual variability in monitoring frequency. We argue that this is a critical omission, given that the frequency of metacognitive monitoring might have important implications for monitoring accuracy and task performance. Within this review, we highlight findings from three literatures, that each provide insight into how often individuals engage in monitoring. To clarify the important links and potential overlaps between these separate bodies of research, we begin by summarizing the metacognitive monitoring literature, including age-related patterns in monitoring accuracy. We then connect these questions regarding spontaneous monitoring, including age-related patterns in spontaneous monitoring, to targeted reviews of the self-regulated learning, think-aloud protocol, and mind-wandering literatures. We discuss situational and dispositional factors believed to influence monitoring accuracy, and propose that the same factors could potentially influence the frequency of spontaneous monitoring. Additionally, we propose that age-related increases in spontaneous monitoring (as suggested by age-related increases in TRI) may contribute to older adults’ intact monitoring abilities. It is our hope that this review will encourage increased attention and research on the topic of spontaneous monitoring