The Effects of Mind-Wandering, Cognitive Load, and Task Engagement on Working Memory Performance in Remote Online Experiments.

Recent changes in environments from in-person to remote present several issues for work, education, and research, particularly related to cognitive performance. Increased distraction in remote environments may lead to increases in mind-wandering and disengagement with tasks at hand, whether virtual meetings, online lectures, or psychological experiments. The present study investigated mind-wandering and multitasking effects during working memory tasks in remote and in-person environments. In two experiments, participants completed a working memory task with varied cognitive load during a secondary task. After each working memory trial, participants reported their mind-wandering during that trial. Some participants completed the procedures in-person, while others completed the procedures remotely. Overall, remote participants reported significantly more mind-wandering and poorer secondary task performance than in-person participants, but this pattern was not reflected in working memory accuracy. Both groups exhibited similar multitasking effects on performance. Additional analyses found that for remote participants, task engagement better predicted working memory performance than either cognitive load or mind-wandering rates but did not indicate a tradeoff in resources between tasks. Together, these results demonstrate the importance of considering multiple metrics when assessing performance and illustrate that making assumptions about the equivalence of remote and in-person work is a risky proposition.

Secondary task engagement drives the McCabe effect in long-term memory.

Processing that occurs while information is held in working memory is critical in long-term retention of that information. One counterintuitive finding is that the concurrent processing required during complex span tasks typically impairs immediate memory, while also leading to improved delayed memory. One proposed mechanism for this effect is retrieval practice that occurs each time memory items are displaced to allow for concurrent processing during complex span tasks. Other research has instead suggested that increased free time during complex span procedures underlies this effect. In the present study, we presented participants with memory items in simple, complex, and slow span tasks and compared their performance on immediate and delayed memory tests. We found that how much a participant engaged with the secondary task of the complex span task corresponded with how strongly they exhibited a complex span boost on delayed memory performance. We also probed what participants were thinking about during the task, and found that participants' focus varied depending both on task type and secondary task engagement. The results support repeated retrieval as a key mechanism in the relationship between working memory processing and long-term retention. Further, the present study highlights the importance of variation in individual cognitive processing in predicting long-term outcomes even when objective conditions remain unchanged.

ALFF response interaction with learning during feedback in individuals with multiple sclerosis.

Amplitude of low-frequency fluctuations (ALFF) is defined as changes of BOLD signal during resting state (RS) brain activity. Previous studies identified differences in RS activation between healthy and multiple sclerosis (MS) participants. However, no research has investigated the relationship between ALFF and learning in MS. We thus examine this here. Twenty-five MS and nineteen healthy participants performed a paired-associate word learning task where participants were presented with extrinsic or intrinsic performance feedback. Compared to healthy participants, MS participants showed higher local brain activation in the right thalamus. We also observed a positive correlation in the MS group between ALFF and extrinsic feedback within the left inferior frontal gyrus, and within the left superior temporal gyrus in association with intrinsic feedback. Healthy participants showed a positive correlation in the right fusiform gyrus between ALFF and extrinsic feedback. Findings suggest that while MS participants do not show a feedback learning impairment compared to the healthy participants, ALFF differences might suggest a general maladaptive pattern of task unrelated thalamic activation and adaptive activation in frontal and temporal regions. Results indicate that ALFF can be successfully used at capturing pathophysiological changes in local brain activation in MS in association with learning through feedback.

Altered functional connectivity during performance feedback processing in multiple sclerosis.

Effective learning from performance feedback is vital for adaptive behavior regulation necessary for successful cognitive performance. Yet, how this learning operates in clinical groups that experience cognitive dysfunction is not well understood. Multiple sclerosis (MS) is an autoimmune, degenerative disease of the central nervous system characterized by physical and cognitive dysfunction. A highly prevalent impairment in MS is cognitive fatigue (CF). CF is associated with altered functioning within cortico-striatal regions that also facilitate feedback-based learning in neurotypical (NT) individuals. Despite this cortico-striatal overlap, research about feedback-based learning in MS, its associated neural underpinnings, and its sensitivity to CF, are all lacking. The present study investigated feedback-based learning ability in MS, as well as associated cortico-striatal function and connectivity. MS and NT participants completed a functional magnetic resonance imaging (fMRI) paired-word association task during which they received trial-by-trial monetary, non-monetary, and uninformative performance feedback. Despite reporting greater CF throughout the task, MS participants displayed comparable task performance to NTs, suggesting preserved feedback-based learning ability in the MS group. Both groups recruited the ventral striatum (VS), caudate nucleus, and ventromedial prefrontal cortex in response to the receipt of performance feedback, suggesting that people with MS also recruit cortico-striatal regions during feedback-based learning. However, compared to NT participants, MS participants also displayed stronger functional connectivity between the VS and task-relevant regions, including the left angular gyrus and right superior temporal gyrus, in response to feedback receipt. Results indicate that CF may not interfere with feedback-based learning in MS. Nonetheless, people with MS may recruit alternative connections with the striatum to assist with this form of learning. These findings have implications for cognitive rehabilitation treatments that incorporate performance feedback to remediate cognitive dysfunction in clinical populations.

Pattern of thalamic nuclei atrophy in early relapse-onset multiple sclerosis.

BACKGROUND: Thalamic atrophy is prominent in multiple sclerosis; however, it is unclear which thalamic nuclei are most vulnerable, especially early in disease. INTRODUCTION: To investigate which thalamic nuclei differ between patients in early stages of relapsing-remitting multiple sclerosis (RRMS) versus healthy controls and examine the relationship between thalamic nuclei volume and T2 lesion volume. METHODS: We derived 15 thalamic subfields from high-resolution 3T magnetic resonance images in 182 patients with early RRMS (diagnosed ≤5.0 years, median 2.0 years). Independent t-tests assessed differences between patients and 35 controls across thalamic subfield volumes. Pearson correlations assessed the relationships between thalamic volumes and T2 lesion volumes. RESULTS: Patients had lower anterior and posterior nuclei volume than controls, whereas medial and ventral nuclei volumes were preserved. Higher T2 lesion volumes were disproportionately related to lower posterior subfield volumes. CONCLUSIONS: We found specific thalamic subfields were more vulnerable to early disease-related changes. We discuss potential mechanisms of differential thalamic subfield atrophy in early MS, including cortical demyelination, CSF toxicity, leptomeningeal inflammation, and iron deposition.

Motor speed does not impact the drift rate: a computational HDDM approach to differentiate cognitive and motor speed.

The drift diffusion model (DDM) is a widely applied computational model of decision making that allows differentiation between latent cognitive and residual processes. One main assumption of the DDM that has undergone little empirical testing is the level of independence between cognitive and motor responses. If true, widespread incorporation of DDM estimation into applied and clinical settings could ease assessment of whether response disruption occurs due to cognitive or motor slowing. Across two experiments, we manipulated response force (motor speed) and set size to evaluate whether drift rates are independent of motor slowing or if motor slowing impacts the drift rate parameter. The hierarchical Bayesian drift diffusion model was used to quantify parameter estimates of drift rate, boundary separation, and non-decision time. Model comparison revealed changes in set size impacted the drift rate while changes in response force did not impact the drift rate, validating independence between drift rates and motor speed. Convergent validity between parameter estimates and traditional assessments of processing speed and motor function were weak or absent. Widespread application, including neurocognitive assessment where confounded changes in cognitive and motor slowing are pervasive, may provide a more process-pure measurement of information processing speed, leading to advanced disease-symptom management.

Ex-Gaussian analysis of simple response time as a measure of information processing speed and the relationship with brain morphometry in multiple sclerosis.

BACKGROUND: The polyfactorial nature of the widely used symbol digit modalities test (SDMT) introduces significant measurement challenges in characterizing information processing speed (IPS) deficits in multiple sclerosis (MS). Measures with high psychometric IPS-specificity and less contamination from other cognitive domains are necessary to fully understand IPS changes. OBJECTIVE: Investigate how three mathematical modeling ex-Gaussian parameter estimates (mu, sigma, tau) derived from a simple response time (RT) task (1) differentiate MS from healthy control participants and (2) correspond to structural brain changes, to evaluate a novel IPS measurement approach. METHODS: Persons with and without MS completed a two-minute behavioral simple RT task, structural MRI and the MS functional composite. RT distributions were deconvolved into ex-Gaussian parameter estimates using mathematical modeling. Group differences and brain-behavior relationships were statistically evaluated. RESULTS: Persons with MS experienced a general pattern of slowing as evidenced by a shift in the Gaussian (mu) component of the distribution. This correlated with whole brain volume and white matter specifically. Additionally, persons with MS had larger values of tau (elongated positively skewed tail) that may reflect attentional lapses. CONCLUSION: The ex-Gaussian approach is sensitive to disease-related IPS changes and provides nuanced information about IPS slowing in MS.

Neural correlates of extrinsic and intrinsic outcome processing during learning in individuals with TBI: a pilot investigation.

Outcome processing, the ability to learn from feedback, is an important component of adaptive behavior and rehabilitation. Evidence from healthy adults implicates the striatum and dopamine in outcome processing. Animal research shows that damage to dopaminergic pathways in the brain can lead to a disruption of dopamine tone and transmission. Such evidence thus suggests that persons with TBI experience deficits in outcome processing. However, no research has directly investigated outcome processing and associated neural mechanisms in TBI. Here, we examine outcome processing in individuals with TBI during learning. Given that TBI negatively impacts striatal and dopaminergic systems, we hypothesize that individuals with TBI exhibit deficits in learning from outcomes. To test this hypothesis, individuals with moderate-to-severe TBI and healthy adults were presented with a declarative paired-associate word learning task. Outcomes indicating performance accuracy were presented immediately during task performance and in the form of either monetary or performance-based feedback. Two types of feedback provided the opportunity to test whether extrinsic and intrinsic motivational aspects of outcome presentation play a role during learning and outcome processing. Our results show that individuals with TBI exhibited impaired learning from feedback compared to healthy participants. Additionally, individuals with TBI exhibited increased activation in the striatum during outcome processing. The results of this study suggest that outcome processing and learning from immediate outcomes is impaired in individuals with TBI and might be related to inefficient use of neural resources during task performance as reflected by increased activation of the striatum.

Global hippocampal and selective thalamic nuclei atrophy differentiate chronic TBI from Non-TBI.

Traumatic brain injury (TBI) may increase susceptibility to neurodegenerative diseases later in life. One neurobiological parallel between chronic TBI and neurodegeneration may be accelerated aging and the nature of atrophy across subcortical gray matter structures. The main aim of the present investigation is to evaluate and rank the degree that subcortical gray matter atrophy differentiates chronic moderate-severe TBI from non-TBI participants by evaluating morphometric differences between groups. Forty individuals with moderate-severe chronic TBI (9.23 yrs from injury) and 33 healthy controls (HC) underwent high resolution 3D T1-weighted structural magnetic resonance imaging. Whole brain volume was classified into white matter, cortical and subcortical gray matter structures with hippocampi and thalami further segmented into subfields and nuclei, respectively. Extensive atrophy was observed across nearly all brain regions for chronic TBI participants. A series of multivariate logistic regression models identified subcortical gray matter structures of the hippocampus and thalamus as the most sensitive to differentiating chronic TBI from non-TBI participants (McFadden R2 = .36, p < .001). Further analyses revealed the pattern of hippocampal atrophy to be global, occurring across nearly all subfields. The pattern of thalamic atrophy appeared to be much more selective and non-uniform, with largest between-group differences evident for nuclei bordering the ventricles. Subcortical gray matter was negatively correlated with time since injury (r = -.31, p = .054), while white matter and cortical gray matter were not. Cognitive ability was lower in the chronic TBI group (Cohen's d = .97, p = .003) and correlated with subcortical structures including the pallidum (r2 = .23, p = .038), thalamus (r2 = .36, p = .007) and ventral diencephalon (r2 = .23, p = .036). These data may support an accelerated aging hypothesis in chronic moderate-severe TBI that coincides with a similar neuropathological profile found in neurodegenerative diseases.

The Symbol Digit Modalities Test (SDMT) is sensitive but non-specific in MS: Lexical access speed, memory, and information processing speed independently contribute to SDMT performance.

BACKGROUND: The Symbol Digit Modalities Test (SDMT) is the most sensitive metric of neurocognitive function in multiple sclerosis (MS), and is consistently interpreted as a measure of information processing speed (IPS). OBJECTIVE: To evaluate the cognitive psychometric profile captured by the SDMT to identify whether different cognitive processes independently underlie performance. METHODS: Three samples of MS patients (total n=661; 185 research patients at MS center; 370 clinical patients at MS center; 106 persons with MS from the community) completed objective assessments of neuropsychological function across cognitive domains. Exploratory factor analysis (EFA) was used to derive latent cognitive factor scores, and operationalize cognitive domain composite scores, to understand the unique, shared and redundant contribution of different cognitive domains to SDMT performance using hierarchical multiple regression and commonality analysis. RESULTS: Across three independent samples we provide converging strong evidence that the cognitive domains of Memory, IPS and Rapid Automatized Naming (lexical access speed) jointly and uniquely contribute to SDMT performance. CONCLUSION: The SDMT measures multiple cognitive processes, which likely explains the high degree of sensitivity to cognitive change in MS. Researchers and clinicians should interpret the SDMT as a multifarious measure of general cognition rather than a specific test of IPS.

Attentional flexibility and prioritization improves long-term memory.

Recent evidence suggests the focus of attention (FoA) is a flexible resource within working memory (WM) used to temporarily maintain some information in a highly accessible state. This flexibility comes at the expense of other representations, demonstrating a resource trade-off in WM maintenance. The present experiments evaluate how flexibility within the FoA impacts long-term memory (LTM) for semantically meaningful information. A WM probe-recognition task was used in which two items were presented in black and a single item was presented in red. To encourage the prioritization and uninterrupted preferential maintenance of specific items, a process we call online refreshing, the red item was associated with a greater point-reward value than were the black items. This WM task was followed by a surprise delayed LTM test. In Experiment 1, the FoA flexibly adjusted to maintain non-recent semantic information with evidence for a resource trade-off across list positions. Flexibility also directly improved LTM. In Experiment 2, reward value was equated across red and black items to evaluate whether an alternative explanation, distinctiveness of encoding, could account for the LTM findings. When reward value was equated, the cued item did not encourage flexible orienting of the FoA toward non-recent items and there was no benefit of the distinct red item on LTM performance. While supportive of past research, these data further demonstrate that semantic information can be flexibly prioritized at the expense of other list positions and that this is directly tied to improvements in LTM.

Prioritization within visual working memory reflects a flexible focus of attention.

When motivated, people can keep nonrecent items in a list active during the presentation of new items, facilitating fast and accurate recall of the earlier items. It has been proposed that this occurs by flexibly orienting attention to a single prioritized list item, thus increasing the amount of attention-based maintenance directed toward this item at the expense of other items. This is manipulated experimentally by associating a single distinct feature with a higher reward value, such as a single red item in a list of black items. These findings may be more parsimoniously explained under a distinctiveness of encoding framework rather than a flexible attention allocation framework. The retrieval advantage for the prioritized list position may be because the incongruent feature stands out in the list perceptually and causes it to become better encoded. Across three visual working memory experiments, we contrast a flexible attention theory against a distinctiveness of encoding theory by manipulating the reward value associated with the incongruent feature. Findings from all three experiments show strong support in favor of the flexible attention theory and no support for the distinctiveness of encoding theory. We also evaluate and find no evidence that strategy use, motivation, or tiredness/fatigue associated with reward value can adequately explain flexible prioritization of attention. Flexible attentional prioritization effects may be best understood under the context of an online attentional refreshing mechanism.

Using Signal Detection Theory to Better Understand Cognitive Fatigue.

When we are fatigued, we feel that our performance is worse than when we are fresh. Yet, for over 100 years, researchers have been unable to identify an objective, behavioral measure that covaries with the subjective experience of fatigue. Previous work suggests that the metrics of signal detection theory (SDT)-response bias (criterion) and perceptual certainty (d')-may change as a function of fatigue, but no work has yet been done to examine whether these metrics covary with fatigue. Here, we investigated cognitive fatigue using SDT. We induced fatigue through repetitive performance of the n-back working memory task, while functional magnetic resonance imaging (fMRI) data was acquired. We also assessed cognitive fatigue at intervals throughout. This enabled us to assess not only whether criterion and d' covary with cognitive fatigue but also whether similar patterns of brain activation underlie cognitive fatigue and SDT measures. Our results show that both criterion and d' were correlated with changes in cognitive fatigue: as fatigue increased, subjects became more conservative in their response bias and their perceptual certainty declined. Furthermore, activation in the striatum of the basal ganglia was also related to cognitive fatigue, criterion, and d'. These results suggest that SDT measures represent an objective measure of cognitive fatigue. Additionally, the overlap and difference in the fMRI results between cognitive fatigue and SDT measures indicate that these measures are related while also separate. In sum, we show the relevance of SDT measures in the understanding of fatigue, thus providing researchers with a new set of tools with which to better understand the nature and consequences of cognitive fatigue.

Do familiar memory items decay?

There is a long-standing debate over whether the passage of time causes forgetting from working memory, a process called trace decay. Researchers providing evidence against the existence of trace decay generally study memory by presenting familiar verbal memory items for 1 s or more per memory item, during the study period. In contrast, researchers providing evidence for trace decay tend to use unfamiliar nonverbal memory items presented for 1 s or less per memory item, during the study period. Taken together, these investigations suggest that familiar items may not decay while unfamiliar items do decay. The availability of verbal rehearsal and the time to consolidate a memory item into working memory during presentation may also play a role in whether or not trace decay will occur. Here we explore these alternatives in a series of experiments closely modeled after studies demonstrating time-based forgetting from working memory, but using familiar verbal memory items in place of the unfamiliar memory items used to observe decay in the past. Our findings suggest that time-based forgetting is persistent across all of these factors while simultaneously challenging prominent views of trace decay. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Poor Encoding and Weak Early Consolidation Underlie Memory Acquisition Deficits in Multiple Sclerosis: Retroactive Interference, Processing Speed, or Working Memory?

OBJECTIVE: Learning and memory impairments are common in multiple sclerosis (MS) and may be related to difficulty acquiring (encoding or consolidating) new information. We evaluate the role of retroactive interference and investigate whether minimizing interference immediately following encoding (early during consolidation) will improve MS participants' ability to remember new verbal information. Additionally, we investigate processing speed differences between memory-impaired and unimpaired participants and present an exploratory analysis of how the dual-components of working memory (capacity vs. processing) relate to memory impairment. METHOD: MS memory-unimpaired (N = 12) and MS memory-impaired participants (N = 12) were compared to healthy controls (N = 15). Interference onset following encoding (early, mid, late, no interference) was manipulated over the retention interval of a verbal learning and memory task. Response times (RT) were recorded during interference trials. RESULTS: MS memory-impaired participants encoded less information and lost proportionally more information over the retention interval (weak consolidation). Lengthening the onset of interference did not benefit memory performance in this sample. Memory performance was unrelated to RT but was related to performance on the Symbol Digit Modalities Test. Primary capacity of working memory did not differ across groups; however, secondary memory processing was reduced for MS memory-impaired participants. CONCLUSION: Minimizing interference following encoding did not improve memory in this sample. Both initial encoding and early consolidation were reduced for memory-impaired MS participants. Evidence for a relationship between processing speed and memory was mixed and depended on the processing speed assessment used. Memory impairment in MS may be partially due to inefficient processing within working memory.

Pilot investigation of the relationship between hippocampal volume and pattern separation deficits in multiple sclerosis.

Memory impairment and hippocampal atrophy are common in multiple sclerosis (MS). In the present pilot study, we investigate whether the mnemonic process of pattern separation is impaired and a predictor of hippocampal volume in relapsing remitting MS. MS participants and healthy controls completed the Mnemonic Similarities Task (MST) along with traditional neurocognitive assessments of memory. 3T structural magnetic resonance imaging was used to estimate whole hippocampal volumes (main aim) and hippocampal subfield volumes (exploratory aim). Results revealed that pattern separation performance was worse for MS participants compared to healthy controls (Cohen's d = 0.96). For MS participants, hippocampal volume was more strongly related to pattern separation performance (r = 0.83) than a traditional neurocognitive measure of visual memory (r = 0.65); hippocampal volume was not related to a traditional neurocognitive measure of verbal memory in this sample. No brain-behavior correlations were significant in the healthy control group. Results of the exploratory analysis revealed relationships between pattern separation performance and subiculum, molecular layer, and CA1 hippocampal subfield volumes for MS participants only. Pattern separation assessed using the MST may be a sensitive cognitive-biomarker of memory dysfunction and changes in hippocampal volume in relapsing-remitting MS.

The relationship between masking and short-term consolidation during recall from visual working memory.

The presentation of a similar but irrelevant stimulus immediately following presentation of a memory item is called masking. Masking is known to reduce performance on working memory tests. This is the type of memory used to hold information in mind for brief periods of time for use in ongoing cognition. Two approaches to understanding masking effects have been proposed in different literatures. Working memory researchers often assume that the reduction in working memory performance after masking is because masking interferes with a transient sensory representation that is needed to complete consolidation into a working memory state. Researchers focused on the attentional blink, a finding that attention cannot be directed to new stimuli during working memory consolidation, have an alternative theory. Attentional blink researchers assume that masking slows the short-term consolidation process, thereby extending the length of the attentional blink. In two experiments, we contrast these two approaches to explaining masking effects and investigate the validity of both hypotheses. Some aspects of both approaches are validated, but neither theoretical perspective alone sufficiently explains the entire pattern of results.

General Mathematical Ability Predicts PASAT Performance in MS Patients: Implications for Clinical Interpretation and Cognitive Reserve.

OBJECTIVES: The Paced Auditory Serial Addition Test (PASAT) is used to assess cognitive status in multiple sclerosis (MS). Although the mathematical demands of the PASAT seem minor (single-digit arithmetic), cognitive psychology research links greater mathematical ability (e.g., algebra, calculus) to more rapid retrieval of single-digit math facts (e.g., 5+6=11). The present study evaluated the hypotheses that (a) mathematical ability is related to PASAT performance and (b) both the relationship between intelligence and PASAT performance as well as the relationship between education and PASAT performance are both mediated by mathematical ability. METHODS: Forty-five MS patients were assessed using the Wechsler Test of Adult Reading, PASAT and Calculation Subtest of the Woodcock-Johnson-III. Regression based path analysis and bootstrapping were used to compute 95% confidence intervals and test for mediation. RESULTS: Mathematical ability (a) was related to PASAT (ß=.61; p<.001) and (b) fully mediated the relationship between Intelligence and PASAT (ß=.76; 95% confidence interval (CI95)=.28, 1.45; direct effect of Intelligence, ß=.42; CI95=-.39, 1.23) as well as the relationship between Education and PASAT (ß=2.43, CI95=.81, 5.16, direct effect of Education, ß=.83, CI95=-1.95, 3.61). DISCUSSION: Mathematical ability represents a source of error in the clinical interpretation of cognitive decline using the PASAT. Domain-specific cognitive reserve is discussed.

An RCT to Treat Learning Impairment in Traumatic Brain Injury: The TBI-MEM Trial.

OBJECTIVE: To examine the efficacy of the modified Story Memory Technique (mSMT) to improve learning (ie, acquisition) and memory in participants with TBI. The mSMT is a behavioral intervention that teaches context and imagery to facilitate learning within 10 sessions over 5 weeks. METHODS: A total of 69 participants with moderate-severe Traumatic Brain Injury (TBI), 35 in the treatment group and 34 in the placebo control group, completed this double-blind, placebo-controlled randomized clinical trial. A baseline neuropsychological assessment was administered, including questionnaires assessing everyday memory. Repeat assessments were conducted immediately posttreatment and 6 months following treatment. Participants in the treatment group were randomly assigned to a booster session or a non-booster session group after completion of treatment with the mSMT to examine the efficacy of monthly booster sessions in facilitating the treatment effect over time. RESULTS: The treatment group demonstrated significant improvement on a prose memory task relative to the placebo group posttreatment (η(2) = 0.064 medium effect). Similar results were noted on objective measures of everyday memory, specifically prospective memory (Cohen's w = 0.43, medium effect), and family report of disinhibition in daily life (η(2) = 0.046, medium effect). CONCLUSION: The mSMT is effective for improving learning and memory in TBI. CLASSIFICATION OF EVIDENCE: Based on widely accepted classification systems for treatment study design, this study provides class I evidence that the mSMT behavioral intervention improves both objective memory and everyday memory in persons with TBI over 5 weeks. Thus, this study extends the evidence for efficacy of the treatment protocol to a sample of persons with TBI.