Working Memory: Maintenance, Updating, and the Realization of Intentions

Transcranial direct current stimulation combined with cognitive training improves two executive functions: Cognitive flexibility and information updating after traumatic brain injury

Traumatic brain injury (TBI) often causes persistent deficits in cognitive flexibility and information updating. Cognitive flexibility refers to the brain's ability to adjust its thinking and behavior in response to changing circumstances, whereas information updating is the process of incorporating new facts into current knowledge. Both cognitive flexibility and information updating are critical components of executive function, and their impairment can have a major influence on a person's capacity to operate independently and adjust to life's problems following a TBI. Understanding and addressing these specific cognitive processes is therefore critical in designing successful therapies for TBI patients. Previous studies have examined the effects of non-invasive brain stimulation and cognitive training separately. This study investigated the effects of combining transcranial direct current stimulation (tDCS) with computer-based cognitive training, comparing this combined intervention against a control group with no treatment, to assess improvements in two executive functions in TBI patients: cognitive flexibility and information updating. Thirty TBI patients, 2-12 weeks post-injury with impaired executive dysfunction, were randomized to an experimental or control group. The experimental group received ten 30-minute sessions over 2 weeks of anodal (A-tDCS), 2.0 mA to the prefrontal cortex while performing cognitive training tasks from the RehaCom software. The control group received no intervention during this period. Cognitive flexibility and information updating were assessed before and after the intervention period using the n-back working memory task, Wisconsin Sorting Card Test, and quantitative electroencephalography (qEEG) during eyes-closed state. Statistically significant differences in theta, alpha, beta, and gamma band power were observed between groups (p < .05, 4 < f < 6). Secondary outcomes indicated significant improvements in cognitive flexibility within Wisconsin Card Sorting Test and information updating performance within n-back task (p < .05, 7 < f < 20). The combination of tDCS and cognitive training may improve cognitive flexibility and information updating in TBI patients by enhancing plasticity and connectivity in prefrontal regions involved in these complex cognitive processes.

From Cognitive Function to Treatment Efficacy in Obsessive-Compulsive Disorder: Insights from a Multidimensional Meta-Analytic Approach

Meta-analysis is a statistical tool used to combine and synthesise the results of multiple independent studies on a particular topic. To this end, researchers isolate important moderators and mediators to investigate their influence on outcomes. This paper introduces a novel approach to meta-analysis, known as multidimensional meta-analysis (mi-MA), to study memory performance in those with obsessive-compulsive disorder (OCD). Unlike traditional meta-analyses, mi-MA allows researchers to extract multiple data points (e.g., using different measures) from single studies and groups of participants, facilitating the exploration of relationships between various moderators while avoiding multicollinearity issues. Therefore, in the first instance, we outline the use of the mi-MA approach to quantify the impact of complex models of memory performance in individuals with OCD. This approach provides novel insights into the complex relationship between various factors affecting memory in people with OCD. By showcasing the effectiveness of mi-MA in analysing intricate data and modelling complex phenomena, the paper establishes it as a valuable tool for researchers exploring multifaceted phenomena, both within OCD research and beyond.

Territory-Related Functional Connectivity Changes Associated with Verbal Memory Decline in Patients with Unilateral Asymptomatic Internal Carotid Stenosis

BACKGROUND AND PURPOSE

Verbal memory decline is a common complaint of patients with severe asymptomatic stenosis of the internal carotid artery (aICS). Previous publications explored the associations between verbal memory decline and altered functional connectivity (FC) after aICS. Patients with severe aICS may show reduced perfusion in the ipsilateral territory and redistribution of cerebral blood flow to compensate for the deficient regions, including expansion of the posterior and contralateral ICA territories via the circle of Willis. However, aICS-related FC changes in anterior and posterior territories and the impact of the sides of stenosis were less explored. This study aims to investigate the altered FC in anterior and posterior circulation territories of patients with left or right unilateral aICS and its association with verbal memory decline.

MATERIALS AND METHODS

We enrolled 15 healthy controls (HCs), 22 patients with left aICS (aICSL), and 33 patients with right aICS (aICSR) to receive fMRI, Mini-Mental State Examination (MMSE), the Digit Span Test (DST), and the 12-item Chinese version of Verbal Learning Tests. We selected brain regions associated with verbal memory within anterior and posterior circulation territories. Territory-related FC alterations and verbal memory decline were identified by comparing the aICSL and aICSR groups with HC groups (P < .05, corrected for multiple comparisons), respectively. Furthermore, the association between altered FC and verbal memory decline was tested with the Pearson correlation analysis.

RESULTS

Compared with HCs, patients with aICSL or aICSR had significant impairment in delayed recall of verbal memory. Decline in delayed recall of verbal memory was significantly associated with altered FC between the right cerebellum and right middle temporal pole in the posterior circulation territory (r = 0.40, P = .03) in the aICSR group and was significantly associated with altered FC between the right superior medial frontal gyrus and left lingual gyrus in the anterior circulation territory (r = 0.56, P = .01) in the aICSL group.

CONCLUSIONS

Patients with aICSL and aICSR showed different patterns of FC alterations in both anterior and posterior circulation territories, which suggests that the side of aICS influences the compensatory mechanism for decline in delayed recall of verbal memory.

Effects of optogenetic silencing the anterior cingulate cortex in a delayed non-match to trajectory task

Working memory is a fundamental cognitive ability, allowing us to keep information in memory for the time needed to perform a given task. A complex neural circuit fulfills these functions, among which is the anterior cingulate cortex (CG). Functionally and anatomically connected to the medial prefrontal, retrosplenial, midcingulate and hippocampus, as well as motor cortices, CG has been implicated in retrieving appropriate information when needed to select and control appropriate behavior. The role of cingulate cortex in working memory-guided behaviors remains unclear due to the lack of studies reversibly interfering with its activity during specific epochs of working memory. We used eNpHR3.0 to silence cingulate neurons while animals perform a standard delayed non-match to trajectory task, and found that, while not causing an absolute impairment in working memory, silencing cingulate neurons during retrieval decreases the mean performance if compared to silencing during encoding. Such retrieval-associated changes are accompanied by longer delays observed when light is delivered to control animals, when compared to eNpHR3.0+ ones, consistent with an adaptive recruitment of additional cognitive resources.

An updating-based working memory load alters the dynamics of eye movements but not their spatial extent during free viewing of natural scenes

The relationship between spatial deployments of attention and working memory load is an important topic of study, with clear implications for real-world tasks such as driving. Previous research has generally shown that attentional breadth broadens under higher load, while exploratory eye-movement behaviour also appears to change with increasing load. However, relatively little research has compared the effects of working memory load on different kinds of spatial deployment, especially in conditions that require updating of the contents of working memory rather than simple retrieval. The present study undertook such a comparison by measuring participants' attentional breadth (via an undirected Navon task) and their exploratory eye-movement behaviour (a free-viewing recall task) under low and high updating working memory loads. While spatial aspects of task performance (attentional breadth, and peripheral extent of image exploration in the free-viewing task) were unaffected by the load manipulation, the exploratory dynamics of the free-viewing task (including fixation durations and scan-path lengths) changed under increasing load. These findings suggest that temporal dynamics, rather than the spatial extent of exploration, are the primary mechanism affected by working memory load during the spatial deployment of attention. Further, individual differences in exploratory behaviour were observed on the free-viewing task: all metrics were highly correlated across working memory load blocks. These findings suggest a need for further investigation of individual differences in eye-movement behaviour; potential factors associated with these individual differences, including working memory capacity and persistence versus flexibility orientations, are discussed.

Proteome-wide Analyses Identified Cortical Proteins Associated With Resilience for Varied Cognitive Abilities

BACKGROUND AND OBJECTIVES

Prior work suggests that cognitive resilience may contribute to the heterogeneity of cognitive decline. This study examined whether distinct cortical proteins provide resilience for different cognitive abilities.

METHODS

Participants were from the Religious Orders Study or the Rush Memory and Aging Project who had undergone annual assessments of 5 cognitive abilities and postmortem assessment of 9 Alzheimer disease and related dementia (ADRD) pathologies. Proteome-wide examination of the dorsolateral prefrontal cortex using tandem mass tag and liquid chromatography-mass spectrometry yielded 8,425 high-abundance proteins. We applied linear mixed-effect models to quantify residual cognitive change (cognitive resilience) of 5 cognitive abilities by regressing out cognitive decline related to age, sex, education, and indices of ADRD pathologies. Then we added terms for each of the individual proteins to identify cognitive resilience proteins associated with the different cognitive abilities.

RESULTS

We included 604 decedents (69% female; mean age at death = 89 years) with proteomic data. A total of 47 cortical proteins that provide cognitive resilience were identified: 22 were associated with specific cognitive abilities, and 25 were common to at least 2 cognitive abilities. NRN1 was the only protein that was associated with more than 2 cognitive abilities (semantic memory: estimate = 0.020, SE = 0.004, p = 2.2 × 10-6; episodic memory: estimate = 0.029, SE = 0.004, p = 5.8 × 10-1; and working memory: estimate = 0.021, SE = 0.004, p = 1.2 × 10-7). Exploratory gene ontology analysis suggested that among top molecular pathways, mitochondrial translation was a molecular mechanism providing resilience in episodic memory, while nuclear-transcribed messenger RNA catabolic processes provided resilience in working memory.

DISCUSSION

This study identified cortical proteins associated with various cognitive abilities. Differential associations across abilities may reflect distinct underlying biological pathways. These data provide potential high-value targets for further mechanistic and drug discovery studies to develop targeted treatments to prevent loss of cognition.

Stress, working memory, and academic performance: a neuroscience perspective

The relationship between stress and working memory (WM) is crucial in determining students' academic performance, but the interaction between these factors is not yet fully understood. WM is a key cognitive function that is important for learning academic skills, such as reading, comprehension, problem-solving, and math. Stress may negatively affect cognition, including WM, via various mechanisms; these include the deleterious effect of glucocorticoids and catecholamines on the structure and function of brain regions that are key for WM, such as the prefrontal cortex and hippocampus. This review explores the mechanisms underlying how stress impacts WM and how it can decrease academic performance. It highlights the importance of implementing effective stress-management strategies to protect WM function and improve academic performance.

Association between adolescents' socioeconomic status and working memory updating functioning: Role of parental educational involvement

Family socioeconomic status (SES) is positively associated with executive functioning. This study tested whether parental educational involvement mediates this association. Two hundred and sixty, 12-15-year-old adolescents completed working memory updating (WMU) and general intelligence tasks, and questionnaires on SES and parental educational involvement. SES and WMU ability were positively associated; there was no difference between the fathers and mothers for three types of educational involvement. The mothers' behavioural involvement positively mediated the SES-WM updating association, whereas a negative mediation was observed for the mothers' intellectual involvement. The fathers' educational involvement did not play a significant mediating role. These results might inform interventions targeting educational involvement for enhancing the cognitive development of children from low SES families.

Cognitive Contributors of Backward Walking in Persons with Multiple Sclerosis

Purpose

Individuals with multiple sclerosis (MS) are at an increased fall risk due to motor and cognitive dysfunction. Our past studies suggest that backward walking (BW) velocity predicts fall risk; however, specific cognitive domains associated with BW velocity remain understudied. The goal of this study was to determine the specific contributions of cognitive functioning to BW velocity in persons with MS. We hypothesized that better visuospatial memory, verbal immediate recall, and faster information processing speed would contribute to faster BW velocity, and deficits in these domains would partially account for disease severity-related impairment in BW velocity.

Methods

Participants completed demographic questionnaires, walking tests, and cognitive assessments. Applied structural equation modeling was used to test our hypothesized model of competing cognitive mediators. Within the model, disease severity was a predictor of BW via three intercorrelated cognitive mediators.

Results

Participants included 39 individuals with relapsing-remitting MS. Results indicated that 35.3% of the significant total effect of disease severity on BW was accounted for by specific cognitive deficits. Verbal immediate recall had the largest contribution, followed by visuospatial memory and information processing speed.

Conclusions

When examining the unique effects of cognitive domains on disease severity-related deficits in BW, a meaningful source of impairment related to visuospatial memory and verbal immediate recall was demonstrated. Considering the utility of BW velocity as a predictor of falls, these results highlight the importance of assessing cognition when evaluating fall risk in MS. Cognitive-based intervention studies investigating fall prevention may find BW as a more specific and sensitive predictor of fall risk than forward walking.

Reliability of self-reported dispositional mindfulness scales and their association with working memory performance and functional connectivity

We systematically investigated the link between trait mindfulness scores and functional connectivity (FC) features or behavioral data, to emphasize the importance of the reliability of self-report mindfulness scores. Sixty healthy young male participants underwent two functional MRI runs with three mindfulness or mind-wandering task blocks with an N-back task (NBT) block. The data from 49 participants (age: 23.3 ± 2.8) for whom two sets of the self-reported Mindfulness Attention Awareness Scale (MAAS) and NBT performance were available were analyzed. We divided participants into two groups based on the consistency level of their MAAS scores (i.e., a "consistent" and an "inconsistent" group). Then, the association between the MAAS scores and FC features or NBT performance was investigated using linear regression analysis with p-value correction and bootstrapping. Meaningful associations (a) between MAAS and NBT accuracy (slope = 0.41, CI = [0.10, 0.73], corrected p < 0.05), (b) between MAAS and the FC edges in the frontoparietal network, and (c) between the FC edges and NBT performance were only observed in the consistent group (n = 26). Our findings demonstrate the importance of appropriate screening mechanisms for self-report-based dispositional mindfulness scores when trait mindfulness scores are combined with neuronal features and behavioral data.

Impact of working memory capacity on predominance of parietal over frontal P300 amplitude

Working memory-related neural activity varies with task load, and these neural variations can be constrained by working memory capacity (WMC). For instance, some studies suggest that parietal and frontal P300 amplitudes, reflecting working memory functioning, vary differentially with task load and WMC. The present study explored whether the predominance of parietal over frontal P300 amplitude is related to WMC, and whether this relationship varies according to task load. Thirty-one adults aged 20-40 years performed a Sternberg task with two set sizes (2 vs. 6 items), during which event-related potentials were recorded. This allowed us to explore the P300 and estimate the magnitude of its parietal over frontal predominance, calculated as a parietal over frontal predominance index (PFPI). Participants also performed the Digit Span and alpha span tests, which were used to compute an independent index of WMC. Results revealed the classic parietal over frontal P300 predominance. They also indicated that the PFPI decreased as task load increased, owing mainly to an increase in frontal P300 amplitude. Interestingly, WMC was positively correlated with the PFPI, suggesting that individuals with greater WMC exhibited greater parietal over frontal predominance. These correlations did not vary across set sizes. Parietal over frontal predominance was reduced in individuals with lower WMC, who relied more on frontal neural resources. This frontal upregulation may have reflected the recruitment of supplementary attentional executive operations to compensate for less efficient working memory maintenance operations.

Cognitive control in age-related hearing loss: A narrative review

Recent evidence suggests links between hearing loss and cognitive impairment in older adults with peripheral age-related hearing loss (ARHL). Earliest cognitive changes have been observed in cognitive control; however, a cohesive account of cognitive control alterations in older adults with peripheral ARHL is lacking. Cognitive control refers to cognitive processes that manage and regulate one's behavior to achieve desired goals. This review summarizes behavioral evidence on alterations in three cognitive control processes, including cognitive flexibility, inhibitory control, and working memory updating, in individuals with ARHL. Of the three processes, cognitive flexibility and working memory updating have been most extensively studied, with relatively fewer studies examining inhibitory control. Most consistent evidence is observed for long-term changes in cognitive flexibility, particularly in individuals with greater severity of ARHL. Equivocal evidence is seen for alterations in inhibitory control and working memory updating, with various factors contributing to inconsistencies across studies. Our review summarizes the emerging body of research on cognitive control in individuals with ARHL to guide future work in this area and considerations related to the management of cognitive issues in this population.

Delayed episodic memory recall after one week is associated with executive functions and divided attention in pediatric epilepsy patients

AIM

Recent studies suggest that although children with epilepsy may show normal learning and memory performance, accelerated long-term forgetting (ALF) may become evident over time. Our study examined associations between delayed episodic memory performance (recall 1-week after learning) and executive functions.

METHOD

A consecutive sample of children with a diagnosis of idiopathic epilepsy with focal or generalized seizures, without morphologic or metabolic abnormalities (n = 20, mean age: 11.70 years) was compared to an IQ-matched healthy control group (n = 20, mean age: 11.55 years). We also assessed parents' and children's rating of forgetting in everyday life and explored its association with delayed episodic memory recall.

RESULTS

Similar to results from recent studies of pediatric patients with temporal lobe epilepsy or genetic generalized epilepsy, our pediatric epilepsy patients showed a significantly elevated recall loss over time, although verbal learning, immediate and 30-minute recall was comparable to the matched control group. Additionally, delayed memory recall in patients was moderately associated with their subjective rating of forgetting, as well as with executive functions (verbal fluency and switching) and divided attention.

INTERPRETATION

We assume that executive functions play a crucial role in deep memory encoding, facilitating stronger and more enduring memory traces. Given that approximately 20% of epilepsy patients - compared to a healthy reference sample - had a significantly reduced delayed recall and due to the clinical relevance of long-term memory, age-appropriate standard norms for free memory recall after 1-week are desirable.

Association between working memory updating ability and cognitive reappraisal: An investigation into a modulatory role of the individual's sex

Cognitive reappraisal has been shown to be an effective emotion regulation strategy that contributes to mental health. Previous studies focused on sex differences in the frequency of use and ability to use this strategy, and the association of fequency of use and ability with executive functioning. However, there is a lack of behavioral studies examining whether the involvement of executive functions in cognitive reappraisal use and ability differs for men and women. Such a sex difference may inform the design of cognitive interventions directed at enhancing cognitive reappraisal use and ability. The present study used a sample of 125 Chinese university students and focused on one key component of executive functioning: working memory updating. Frequency of cognitive reappraisal use was assessed by self-report. Ability to use cognitive reappraisal and working memory updating capacity were each assessed with a laboratory task. The results revealed no sex difference in cognitive reappraisal use or ability. However, of primary interest, the ability to apply cognitive reappraisal was associated with working memory updating performance, but only for women. If confirmed in further studies, these findings suggest that cognitive interventions in general, and working memory updating trainings more specifically, are more likely to enhance the ability to use cognitive reappraisal as a means to regulate emotions in women than in men.

Cilia in the Striatum Mediate Timing-Dependent Functions

Almost all brain cells contain cilia, antennae-like microtubule-based organelles. Yet, the significance of cilia, once considered vestigial organelles, in the higher-order brain functions is unknown. Cilia act as a hub that senses and transduces environmental sensory stimuli to generate an appropriate cellular response. Similarly, the striatum, a brain structure enriched in cilia, functions as a hub that receives and integrates various types of environmental information to drive appropriate motor response. To understand cilia's role in the striatum functions, we used loxP/Cre technology to ablate cilia from the dorsal striatum of male mice and monitored the behavioral consequences. Our results revealed an essential role for striatal cilia in the acquisition and brief storage of information, including learning new motor skills, but not in long-term consolidation of information or maintaining habitual/learned motor skills. A fundamental aspect of all disrupted functions was the "time perception/judgment deficit." Furthermore, the observed behavioral deficits form a cluster pertaining to clinical manifestations overlapping across psychiatric disorders that involve the striatum functions and are known to exhibit timing deficits. Thus, striatal cilia may act as a calibrator of the timing functions of the basal ganglia-cortical circuit by maintaining proper timing perception. Our findings suggest that dysfunctional cilia may contribute to the pathophysiology of neuro-psychiatric disorders, as related to deficits in timing perception.

Oscillatory beta/alpha band modulations: A potential biomarker of functional language and motor recovery in chronic stroke?

Stroke remains one of the leading causes of various disabilities, including debilitating motor and language impairments. Though various treatments exist, post-stroke impairments frequently become chronic, dramatically reducing daily life quality, and requiring specific rehabilitation. A critical goal of chronic stroke rehabilitation is to induce, usually through behavioral training, experience-dependent plasticity processes in order to promote functional recovery. However, the efficiency of such interventions is typically modest, and very little is known regarding the neural dynamics underpinning recovery processes and possible biomarkers of their efficiency. Some studies have emphasized specific alterations of excitatory–inhibitory balance within distributed neural networks as an important recovery correlate. Neural processes sensitive to these alterations, such as task-dependent oscillatory activity in beta as well as alpha bands, may be candidate biomarkers of chronic stroke functional recovery. In this review, we discuss the results of studies on motor and language recovery with a focus on oscillatory processes centered around the beta band and their modulations during functional recovery in chronic stroke. The discussion is based on a framework where task-dependent modulations of beta and alpha oscillatory activity, generated by the deep cortical excitatory–inhibitory microcircuits, serve as a neural mechanism of domain-general top-down control processes. We discuss the findings, their limitations, and possible directions for future research.

Effects of forward and backward span trainings on working memory: Evidence from a randomized controlled trial

Both forward and backward working memory span tasks have been used in cognitive training, but no study has been conducted to test whether the two types of trainings are equally effective. Based on data from a randomized controlled trial, this study (N = 60 healthy college students) tested the effects of backward span training, forward span training, and no intervention. Event-related potential (ERP) signals were recorded at the pre-, mid-, and post-tests while the subjects were performing a distractor version of the change detection task, which included three conditions (2 targets and 0 distractor [2T0D]; 4 targets and 0 distractor [4T0D]; and 2 targets and 2 distractors [2T2D]). Behavioral data were collected from two additional tasks: a multi-object version of the change detection task, and a suppress task. Compared to no intervention, both forward and backward span trainings led to significantly greater improvement in working memory maintenance, based on indices from both behavioral (Kmax) and ERP data (CDA_2T0D and CDA_4T0D). Backward span training also improved interference control based on the ERP data (CDA_filtering efficiency) to a greater extent than did forward span training and no intervention, but the three groups did not differ in terms of behavioral indices of interference control. These results have potential implications for optimizing the current cognitive training on working memory.

Virtual Reality-based Cognitive Intervention for Enhancing Executive Functions in Community-dwelling Older Adults

With the rapid growth of the older population globally, it is anticipated that age-related cognitive decline in the prodromal phase and more severe pathological decline will increase. Moreover, currently, no effective treatment options for the disease exist. Thus, early and timely prevention actions are promising and prior strategies to preserve cognitive functions by preventing symptomatology from increasing the age-related deterioration of the functions in healthy older adults. This study aims to develop the virtual reality-based cognitive intervention for enhancing executive functions (EFs) and examine the EFs after training with the virtual reality-based cognitive intervention in community-dwelling older adults. Following inclusion/exclusion criteria, 60 community-dwelling older adults aged 60-69 years were involved in the study and randomly divided into passive control and experimental groups. Eight 60 min virtual reality-based cognitive intervention sessions were held twice a week and lasted for 1 month. The EFs (i.e., inhibition, updating, and shifting) of the participants were assessed by using standardized computerized tasks, i.e., Go/NoGo, forward and backward digit span, and Berg's card sorting tasks. Additionally, a repeated-measure ANCOVA and effect sizes were applied to investigate the effects of the developed intervention. The virtual reality-based intervention significantly improved the EFs of older adults in the experimental group. Specifically, the magnitudes of enhancement were observed for inhibitory as indexed by the response time, F(1) = 6.95, p < .05, η_p² = .11, updating as represented by the memory span, F(1) = 12.09, p < .01, η_p² = .18, and the response time, F(1) = 4.46, p = .04, η_p² = .07, and shifting abilities as indexed by the percentage of correct responses, F(1) = 5.30, p = .03, η_p² = .09, respectively. The results indicated that the simultaneous combined cognitive-motor control as embedded in the virtual-based intervention is safe and effective in enhancing EFs in older adults without cognitive impairment. Nevertheless, further studies are required to investigate the benefits of these enhancements to motor functions and emotional aspects relating to daily living and the well-being of older populations in communities.

What Is Targeted When We Train Working Memory? Evidence From a Meta-Analysis of the Neural Correlates of Working Memory Training Using Activation Likelihood Estimation

Working memory (WM) is the system responsible for maintaining and manipulating information, in the face of ongoing distraction. In turn, WM span is perceived to be an individual-differences construct reflecting the limited capacity of this system. Recently, however, there has been some evidence to suggest that WM capacity can increase through training, raising the possibility that training can functionally alter the neural structures supporting WM. To address the hypothesis that the neural substrates underlying WM are targeted by training, we conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of WM training using Activation Likelihood Estimation (ALE). Our results demonstrate that WM training is associated exclusively with decreases in blood oxygenation level-dependent (BOLD) responses in clusters within the fronto-parietal system that underlie WM, including the bilateral inferior parietal lobule (BA 39/40), middle (BA 9) and superior (BA 6) frontal gyri, and medial frontal gyrus bordering on the cingulate gyrus (BA 8/32). We discuss the various psychological and physiological mechanisms that could be responsible for the observed reductions in the BOLD signal in relation to WM training, and consider their implications for the construct of WM span as a limited resource.

A common polymorphism in the dopamine transporter gene predicts working memory performance and in vivo dopamine integrity in aging

Dopamine (DA) integrity is suggested as a potential cause of individual differences in working memory (WM) performance among older adults. Still, the principal dopaminergic mechanisms giving rise to WM differences remain unspecified. Here, 61 single-nucleotide polymorphisms, located in or adjacent to various dopamine-related genes, were assessed for their links to WM performance in a sample of 1313 adults aged 61-80 years from the Berlin Aging Study II. Least Absolute Shrinkage and Selection Operator (LASSO) regression was conducted to estimate associations between polymorphisms and WM. Rs40184 in the DA transporter gene, SLC6A3, showed allelic group differences in WM, with T-carriers performing better than C homozygotes (p<0.01). This finding was replicated in an independent sample from the Cognition, Brain, and Aging study (COBRA; baseline: n = 181, ages: 64-68 years; 5-year follow up: n = 129). In COBRA, in vivo DA integrity was measured with ¹¹C-raclopride and positron emission tomography. Notably, WM as well as in vivo DA integrity was higher for rs40184 T-carriers at baseline (p<0.05 for WM and caudate and hippocampal D2-receptor availability) and at the 5-year follow-up (p<0.05 for WM and hippocampal D2 availability). Our findings indicate that individual differences in DA transporter function contribute to differences in WM performance in old age, presumably by regulating DA availability.

Which 'Working' Components of Working Memory aren't Working in Youth with ADHD?

Despite replicated evidence for working memory deficits in youth with ADHD, no study has comprehensively assessed all three primary 'working' subcomponents of the working memory system in these children. Children ages 8-13 with (n = 45) and without (n = 41) ADHD (40% female; M_age = 10.5; 65% Caucasian/Non-Hispanic) completed a counterbalanced battery of nine tasks (three per construct) assessing working memory reordering (maintaining and rearranging information in mind), updating (active monitoring of incoming information and replacing outdated with relevant information), and dual-processing (maintaining information in mind while performing a secondary task). Detailed analytic plans were preregistered. Bayesian t-tests indicated that, at the group level, children with ADHD exhibited significant impairments in working memory reordering (BF₁₀ = 4.64 × 10⁵; d = 1.34) and updating (BF₁₀ = 9.49; d = 0.64), but not dual-processing (BF₀₁ = 1.33; d = 0.37). Overall, 67%-71% of youth with ADHD exhibited impairment in at least one central executive working memory domain. Reordering showed the most ADHD-related impairment, with 75% classified as below average or impaired, and none demonstrating strengths. The majority of children with ADHD (52%-57%) demonstrated average or better abilities in the remaining two domains, with a notable minority demonstrating strengths in updating (8%) and dual-processing (20%). Notably, impairments in domain-general central executive working memory, rather than individual subcomponents, predicted ADHD severity, suggesting that common rather than specific working memory mechanisms may be central to understanding ADHD symptoms. These impairment estimates extend prior work by providing initial evidence that children with ADHD not only exhibit heterogeneous profiles across cognitive domains but also exhibit significant heterogeneity within subcomponents of key cognitive processes.

Prefrontal Lesions Disrupt Posterior Alpha-Gamma Coordination of Visual Working Memory Representations

How does the human brain prioritize different visual representations in working memory (WM)? Here, we define the oscillatory mechanisms supporting selection of "where" and "when" features from visual WM storage and investigate the role of pFC in feature selection. Fourteen individuals with lateral pFC damage and 20 healthy controls performed a visuospatial WM task while EEG was recorded. On each trial, two shapes were presented sequentially in a top/bottom spatial orientation. A retro-cue presented mid-delay prompted which of the two shapes had been in either the top/bottom spatial position or first/second temporal position. We found that cross-frequency coupling between parieto-occipital alpha (α; 8-12 Hz) oscillations and topographically distributed gamma (γ; 30-50 Hz) activity tracked selection of the distinct cued feature in controls. This signature of feature selection was disrupted in patients with pFC lesions, despite intact α-γ coupling independent of feature selection. These findings reveal a pFC-dependent parieto-occipital α-γ mechanism for the rapid selection of visual WM representations.

Cognitive Aftereffects of Acute tDCS Coupled with Cognitive Training: An fMRI Study in Healthy Seniors

Enhancing cognitive functions through noninvasive brain stimulation is of enormous public interest, particularly for the aging population in whom processes such as working memory are known to decline. In a randomized double-blind crossover study, we investigated the acute behavioral and neural aftereffects of bifrontal and frontoparietal transcranial direct current stimulation (tDCS) combined with visual working memory (VWM) training on 25 highly educated older adults. Resting-state functional connectivity (rs-FC) analysis was performed prior to and after each stimulation session with a focus on the frontoparietal control network (FPCN). The bifrontal montage with anode over the left dorsolateral prefrontal cortex enhanced VWM accuracy as compared to the sham stimulation. With the rs-FC within the FPCN, we observed significant stimulation × time interaction using bifrontal tDCS. We found no cognitive aftereffects of the frontoparietal tDCS compared to sham stimulation. Our study shows that a single bifrontal tDCS combined with cognitive training may enhance VWM performance and rs-FC within the relevant brain network even in highly educated older adults.

Real-world objects are not stored in holistic representations in visual working memory

When storing multiple objects in visual working memory, observers sometimes misattribute perceived features to incorrect locations or objects. These misattributions are called binding errors (or swaps) and have been previously demonstrated mostly in simple objects whose features are easy to encode independently and arbitrarily chosen, like colors and orientations. Here, we tested whether similar swaps can occur with real-world objects, where the connection between features is meaningful rather than arbitrary. In Experiments 1 and 2, observers were simultaneously shown four items from two object categories. Within a category, the two exemplars could be presented in either the same or different states (e.g., open/closed; full/empty). After a delay, both exemplars from one of the categories were probed, and participants had to recognize which exemplar went with which state. We found good memory for state information and exemplar information on their own, but a significant memory decrement for exemplar-state combinations, suggesting that binding was difficult for observers and swap errors occurred even for meaningful real-world objects. In Experiment 3, we used the same task, but in one-half of the trials, the locations of the exemplars were swapped at test. We found that there are more errors in general when the locations of exemplars were swapped. We concluded that the internal features of real-world objects are not perfectly bound in working memory, and location updates impair object and feature representations. Overall, we provide evidence that even real-world objects are not stored in an entirely unitized format in working memory.

Robust spatial ventriloquism effect and trial-by-trial aftereffect under memory interference

Our brain adapts to discrepancies in the sensory inputs. One example is provided by the ventriloquism effect, experienced when the sight and sound of an object are displaced. Here the discrepant multisensory stimuli not only result in a biased localization of the sound, but also recalibrate the perception of subsequent unisensory acoustic information in the so-called ventriloquism aftereffect. This aftereffect has been linked to memory-related processes based on its parallels to general sequential effects in perceptual decision making experiments and insights obtained in neuroimaging studies. For example, we have recently implied memory-related medial parietal regions in the trial-by-trial ventriloquism aftereffect. Here, we tested the hypothesis that the trial-by-trial (or immediate) ventriloquism aftereffect is indeed susceptible to manipulations interfering with working memory. Across three experiments we systematically manipulated the temporal delays between stimuli and response for either the ventriloquism or the aftereffect trials, or added a sensory-motor masking trial in between. Our data reveal no significant impact of either of these manipulations on the aftereffect, suggesting that the recalibration reflected by the trial-by-trial ventriloquism aftereffect is surprisingly resilient to manipulations interfering with memory-related processes.

Toddlers, Tools, and Tech: The Cognitive Ontogenesis of Innovation

The development of tool innovation presents a paradox. How do humans have such diverse and complex technology, ranging from smartphones to aircraft, and yet young children find even simple tool innovation challenges, such as fashioning a hook to retrieve a basket from a tube, remarkably difficult? We propose that the solution to this paradox is the cognitive ontogenesis of tool innovation. Using a common measure of children's tool innovation, we describe how multiple cognitive mechanisms work in concert at each step of its process: recognizing the problem, generating appropriate solutions, and the social transmission of innovations. We discuss what the ontogeny of this skill tells us about cognitive and cultural evolution and provide recommendations for future research.

Age differences in predicting working memory performance from network-based functional connectivity

Deterioration in working memory capacity (WMC) has been associated with normal aging, but it remains unknown how age affects the relationship between WMC and connectivity within functional brain networks. We therefore examined the predictability of WMC from fMRI-based resting-state functional connectivity (RSFC) within eight meta-analytically defined functional brain networks and the connectome in young and old adults using relevance vector machine in a robust cross-validation scheme. Particular brain networks have been associated with mental functions linked to WMC to a varying degree and are associated with age-related differences in performance. Comparing prediction performance between the young and old sample revealed age-specific effects: In young adults, we found a general unpredictability of WMC from RSFC in networks subserving WM, cognitive action control, vigilant attention, theory-of-mind cognition, and semantic memory, whereas in older adults each network significantly predicted WMC. Moreover, both WM-related and WM-unrelated networks were differently predictive in older adults with low versus high WMC. These results indicate that the within-network functional coupling during task-free states is specifically related to individual task performance in advanced age, suggesting neural-level reorganization. In particular, our findings support the notion of a decreased segregation of functional brain networks, deterioration of network integrity within different networks and/or compensation by reorganization as factors driving associations between individual WMC and within-network RSFC in older adults. Thus, using multivariate pattern regression provided novel insights into age-related brain reorganization by linking cognitive capacity to brain network integrity.

Disentangling the Role of Working Memory in Parkinson's Disease

Working memory (WM) represents a core cognitive function with a major striatal contribution, and thus WM deficits, commonly observed in Parkinson’s disease (PD), could also relate to many other problems in PD patients. Our online study aimed to determine the subdomains of WM that are particularly affected in PD and to clarify the links between WM and everyday cognitive deficits, other executive functions, psychiatric and PD symptoms, as well as early cognitive impairment. Fifty-two mild-to-moderate PD patients and 54 healthy controls performed seven WM tasks tapping selective updating, continuous monitoring, or maintenance of currently active information. Self-ratings of everyday cognition, depression, and apathy symptoms, as well as screenings of global cognitive impairment, were also collected. The data were analyzed using structural equation modeling. Of the three WM domains, only selective updating was directly predictive of PD group membership. More widespread WM deficits were observed only in relation to global cognitive impairment in PD patients. Self-rated everyday cognition or psychiatric symptoms were not linked to WM performance but correlated with each other. Our findings suggest that WM has a rather limited role in the clinical manifestation of PD. Nevertheless, due to its elementary link to striatal function, the updating component of WM could be a candidate for a cognitive marker of PD also in patients who are otherwise cognitively well-preserved.

Effects of working memory training on emotion regulation: Transdiagnostic review

Working memory training is widely used transdiagnostically to improve cognition. However, more recently, studies using working memory training packages have targeted emotion-regulation outcomes to determine whether far transfer effects can be achieved. A narrative review is conducted of studies that have used standardized computerized working memory training packages across healthy volunteers, affect, anxiety, post-traumatic stress disorder (PTSD), and eating disordered populations with emotion-regulation outcomes. Working memory training has been used in children, adolescents, and adults to improve emotion regulation. Many studies have reported gains in mood as well as emotion-regulation strategies following working memory training, regardless of clinical indication and whether near transfer gains were achieved in cognitive domains. Significant emotion-regulation outcomes include: state and trait anxiety, rumination, brooding, positive appraisal, decreasing maladaptive emotion-regulation strategies, and decreasing intrusive thoughts. It is speculated that these far transfer outcomes from working memory training are possible due to the cognitive and neural overlap between cognitive and affective working memory, and emotion regulation. Working memory training could improve cognitive efficiency, which, in turn, increases the availability of cognitive resources during times when emotion regulation is taxed. Future studies need to consider the role of participant expectancy in predicting outcome measure performance, and including subjective and objective outcomes is paramount to study design. Furthermore, sample sizes require additional attention, given that the current review highlights that individual differences in non-clinical and clinical populations influence the outcomes from working memory training. Working memory training offers a possibility for improving emotion regulation transdiagnostically.

ERP evidence for the effect of working memory span training on working memory maintenance: A randomized controlled trial

There is a lot of debate in the literature with regards to whether the effects of working memory span training generalize to working memory tasks that are different from the trained task, however, there is little evidence to date supporting this idea. The present randomized controlled trial included 80 undergraduate students who were randomly assigned to either the experimental group (N = 40) or the control group (N = 40) in order to receive a working memory span intervention for 20 sessions over the course of 4 weeks. Brain electrophysiological signals during a dot pattern expectancy (DPX) task and a change detection task were recorded both before and after the intervention. The amplitudes of characteristic event-related potential (ERP) components reflecting working memory maintenance capability during the delay period of both tasks (i.e., the contingent negative variation or CNV, derived from the DPX task, and the contralateral delay activity or CDA, derived from the change detection task) were used as the primary outcome measures. Our data indicated that the intervention resulted in specific changes in both, the CNV and the CDA, suggesting that working memory span training generalized to working memory maintenance processes as observed in working memory tasks that were different from the trained task. We conclude that working memory span training might serve as a useful tool to improve working memory maintenance capability. Trial Registration: Chinese Clinical Trial Registry (chiCTR-INR-17011728).

Evaluation of the spatial variability in the major resting-state networks across human brain functional atlases

The human brain is intrinsically organized into resting‐state networks (RSNs). Currently, several human brain functional atlases are used to define the spatial constituents of these RSNs. However, there are significant concerns about interatlas variability. In response, we undertook a quantitative comparison of the five major RSNs (default mode [DMN], salience, central executive, sensorimotor, and visual networks) across currently available brain functional atlases (n = 6) in which we demonstrated that (a) similarity between atlases was modest and positively linked to the size of the sample used to construct them; (b) across atlases, spatial overlap among major RSNs ranged between 17 and 76% (mean = 39%), which resulted in variability in their functional connectivity; (c) lower order RSNs were generally spatially conserved across atlases; (d) among higher order RSNs, the DMN was the most conserved across atlases; and (e) voxel‐wise flexibility (i.e., the likelihood of a voxel to change network assignment across atlases) was high for subcortical regions and low for the sensory, motor and medial prefrontal cortices, and the precuneus. In order to facilitate RSN reproducibility in future studies, we provide a new freely available Consensual Atlas of REsting‐state Networks, based on the most reliable atlases.

Remembering to Forget: A Dual Role for Sleep Oscillations in Memory Consolidation and Forgetting

It has been known since the time of patient H. M. and Karl Lashley's equipotentiality studies that the hippocampus and cortex serve mnestic functions. Current memory models maintain that these two brain structures accomplish unique, but interactive, memory functions. Specifically, most modeling suggests that memories are rapidly acquired during waking experience by the hippocampus, before being later consolidated into the cortex for long-term storage. Sleep has been shown to be critical for the transfer and consolidation of memories in the cortex. Like memory consolidation, a role for sleep in adaptive forgetting has both historical precedent, as Francis Crick suggested in 1983 that sleep was for "reverse-learning," and recent empirical support. In this article I review the evidence indicating that the same brain activity involved in sleep replay associated memory consolidation is responsible for sleep-dependent forgetting. In reviewing the literature, it became clear that both a cellular mechanism for systems consolidation and an agreed upon general, as well as cellular, mechanism for sleep-dependent forgetting is seldom discussed or is lacking. I advocate here for a candidate cellular systems consolidation mechanism wherein changes in calcium kinetics and the activation of consolidative signaling cascades arise from the triple phase locking of non-rapid eye movement sleep (NREMS) slow oscillation, sleep spindle and sharp-wave ripple rhythms. I go on to speculatively consider several sleep stage specific forgetting mechanisms and conclude by discussing a notional function of NREM-rapid eye movement sleep (REMS) cycling. The discussed model argues that the cyclical organization of sleep functions to first lay down and edit and then stabilize and integrate engrams. All things considered, it is increasingly clear that hallmark sleep stage rhythms, including several NREMS oscillations and the REMS hippocampal theta rhythm, serve the dual function of enabling simultaneous memory consolidation and adaptive forgetting. Specifically, the same sleep rhythms that consolidate new memories, in the cortex and hippocampus, simultaneously organize the adaptive forgetting of older memories in these brain regions.

Characterizing hippocampal dynamics with MEG: A systematic review and evidence-based guidelines

The hippocampus, a hub of activity for a variety of important cognitive processes, is a target of increasing interest for researchers and clinicians. Magnetoencephalography (MEG) is an attractive technique for imaging spectro-temporal aspects of function, for example, neural oscillations and network timing, especially in shallow cortical structures. However, the decrease in MEG signal-to-noise ratio as a function of source depth implies that the utility of MEG for investigations of deeper brain structures, including the hippocampus, is less clear. To determine whether MEG can be used to detect and localize activity from the hippocampus, we executed a systematic review of the existing literature and found successful detection of oscillatory neural activity originating in the hippocampus with MEG. Prerequisites are the use of established experimental paradigms, adequate coregistration, forward modeling, analysis methods, optimization of signal-to-noise ratios, and protocol trial designs that maximize contrast for hippocampal activity while minimizing those from other brain regions. While localizing activity to specific sub-structures within the hippocampus has not been achieved, we provide recommendations for improving the reliability of such endeavors.

Cognitive control in the prefrontal cortex: A central or distributed executive?

Cognitive control is the foundation for attaining goals by flexible adaptation of action to changing environmental demands. It has been hypothesized to be critically dependent upon the prefrontal cortex (PFC). In this mini-review, evidence for domain-general versus domain-specific cognitive control is examined, with a particular focus on attention and memory. The reviewed studies examined different levels of cognitive control in relation to performance and patterns of brain activity, and a few included direct comparisons of cognitive-control modulations across cognitive domains. Within domains, increased demands on cognitive control consistently translated into increased PFC activity, but limited overlap in recruited PFC regions was observed between domains. It is concluded that the PFC supports multiple cognitive-control systems that collectively may be conceived of as a distributed executive.

Purkinje Cell Representations of Behavior: Diary of a Busy Neuron

Fundamental for understanding cerebellar function is determining the representations in Purkinje cell activity, the sole output of the cerebellar cortex. Up to the present, the most accurate descriptions of the information encoded by Purkinje cells were obtained in the context of motor behavior and reveal a high degree of heterogeneity of kinematic and performance error signals encoded. The most productive framework for organizing Purkinje cell firing representations is provided by the forward internal model hypothesis. Direct tests of this hypothesis show that individual Purkinje cells encode two different forward models simultaneously, one for effector kinematics and one for task performance. Newer results demonstrate that the timing of simple spike encoding of motor parameters spans an extend interval of up to ±2 seconds. Furthermore, complex spike discharge is not limited to signaling errors, can be predictive, and dynamically controls the information in the simple spike firing to meet the demands of upcoming behavior. These rich, diverse, and changing representations highlight the integrative aspects of cerebellar function and offer the opportunity to generalize the cerebellar computational framework over both motor and non-motor domains.

Neurochemical changes in basal ganglia affect time perception in parkinsonians

BACKGROUND

Parkinson's disease is described as resulting from dopaminergic cells progressive degeneration, specifically in the substantia nigra pars compacta that influence the voluntary movements control, decision making and time perception.

AIM

This review had a goal to update the relation between time perception and Parkinson's Disease.

METHODOLOGY

We used the PRISMA methodology for this investigation built guided for subjects dopaminergic dysfunction in the time judgment, pharmacological models with levodopa and new studies on the time perception in Parkinson's Disease. We researched on databases Scielo, Pubmed / Medline and ISI Web of Knowledge on August 2017 and repeated in September 2017 and February 2018 using terms and associations relevant for obtaining articles in English about the aspects neurobiology incorporated in time perception. No publication status or restriction of publication date was imposed, but we used as exclusion criteria: dissertations, book reviews, conferences or editorial work.

RESULTS/DISCUSSION

We have demonstrated that the time cognitive processes are underlying to performance in cognitive tasks and that many are the brain areas and functions involved and the modulators in the time perception performance.

CONCLUSIONS

The influence of dopaminergic on Parkinson's Disease is an important research tool in Neuroscience while allowing for the search for clarifications regarding behavioral phenotypes of Parkinson's disease patients and to study the areas of the brain that are involved in the dopaminergic circuit and their integration with the time perception mechanisms.

On the efficiency of instruction-based rule encoding

Instructions have long been considered a highly efficient route to knowledge acquisition especially compared to trial-and-error learning. We aimed at substantiating this claim by identifying boundary conditions for such an efficiency gain, including the influence of active learning intention, repeated instructions, and working memory load and span. Our experimental design allowed us to not only assess how well the instructed stimulus-response (S-R) rules were implemented later on, but also to directly measure prior instruction encoding processes. This revealed that instruction encoding was boosted by an active learning intention which in turn entailed better subsequent rule implementation. As should be expected, instruction-based learning took fewer trials than trial-and-error learning to reach a similar performance level. But more importantly, even when performance was measured relative to the identical number of preceding correct implementation trials, this efficiency gain persisted both in accuracy and in speed. This suggests that the naturally greater number of failed attempts in the initial phase of trial-and-error learning also negatively impacted learning in subsequent trials due to the persistence of erroneous memory traces established beforehand. A single instruction trial was sufficient to establish the advantage over trial-and-error learning but repeated instructions were better. Strategic factors and inter-individual differences in WM span - the latter exclusively affecting trial-and-error learning presumably due to the considerably more demanding working memory operations - could reduce or even abolish this advantage, but only in error rates. The same was not true for response time gains suggesting generally more efficient task automatization in instruction-based learning.

How context features modulate the involvement of the working memory system during discourse comprehension

Using functional magnetic resonance imaging (fMRI), we investigated the effects of context features on the involvement of the working memory (WM) system during discourse comprehension. During the fMRI scan, participants were asked to read two-sentence discourses in which the topic of the second sentence was either maintained, or was shifted from, the topic of the first. Changes in the level of coherence between the two sentences as well as context length were also investigated across discourse items. The WM system was identified with a verbal N-back task. Analysis of the reading comprehension task revealed that within the WM system, stronger activation in the left inferior frontal gyrus corresponded with increased bridging coherence demands between sentences, while greater activation in the left inferior and middle frontal gyri, bilateral superior frontal gyri, and bilateral inferior parietal lobules corresponded with increased context length. Topic variation showed no effect on activation of the WM system. These results provide new insights into understanding how different levels of context features modulate activation of the subcomponents of the WM system and indicate a role for the left inferior frontal gyrus as a core component of the WM system supporting discourse processing.

Neural activations associated with feedback and retrieval success

There is substantial behavioral evidence for a phenomenon commonly called "the testing effect", i.e. superior memory performance after repeated testing compared to re-study of to-be-learned materials. However, considerably less is known about the underlying neuro-cognitive processes that are involved in the initial testing phase, and thus underlies the actual testing effect. Here, we investigated functional brain activity related to test-enhanced learning with feedback. Subjects learned foreign vocabulary across three consecutive tests with correct-answer feedback. Functional brain-activity responses were analyzed in relation to retrieval and feedback events, respectively. Results revealed up-regulated activity in fronto-striatal regions during the first successful retrieval, followed by a marked reduction in activity as a function of improved learning. Whereas feedback improved behavioral performance across consecutive tests, feedback had a negligable role after the first successful retrieval for functional brain-activity modulations. It is suggested that the beneficial effects of test-enhanced learning is regulated by feedback-induced updating of memory representations, mediated via the striatum, that might underlie the stabilization of memory commonly seen in behavioral studies of the testing effect.

Long-Term Predictive and Feedback Encoding of Motor Signals in the Simple Spike Discharge of Purkinje Cells

Most hypotheses of cerebellar function emphasize a role in real-time control of movements. However, the cerebellum’s use of current information to adjust future movements and its involvement in sequencing, working memory, and attention argues for predicting and maintaining information over extended time windows. The present study examines the time course of Purkinje cell discharge modulation in the monkey (Macaca mulatta) during manual, pseudo-random tracking. Analysis of the simple spike firing from 183 Purkinje cells during tracking reveals modulation up to 2 s before and after kinematics and position error. Modulation significance was assessed against trial shuffled firing, which decoupled simple spike activity from behavior and abolished long-range encoding while preserving data statistics. Position, velocity, and position errors have the most frequent and strongest long-range feedforward and feedback modulations, with less common, weaker long-term correlations for speed and radial error. Position, velocity, and position errors can be decoded from the population simple spike firing with considerable accuracy for even the longest predictive (-2000 to -1500 ms) and feedback (1500 to 2000 ms) epochs. Separate analysis of the simple spike firing in the initial hold period preceding tracking shows similar long-range feedforward encoding of the upcoming movement and in the final hold period feedback encoding of the just completed movement, respectively. Complex spike analysis reveals little long-term modulation with behavior. We conclude that Purkinje cell simple spike discharge includes short- and long-range representations of both upcoming and preceding behavior that could underlie cerebellar involvement in error correction, working memory, and sequencing.

Longitudinal Changes in Component Processes of Working Memory

Working memory (WM) entails maintenance and manipulation of information in the absence of sensory input. This study investigated the trajectories and neural basis of these component processes of WM functions in aging. Longitudinal human functional magnetic resonance imaging (fMRI) data are presented from 136 older individuals (55-80 years) who were scanned at baseline and again 4 years later. We obtained evidence that age-related changes in parietal and frontal components of the WM core network are dissociable in terms of their role in maintenance of perceptual representations and further manipulation of this information, respectively. Individual difference analyses in performance subgroups showed that only prefrontal changes in fMRI activation were accompanied by changes in performance, but parietal brain activity was related to study dropout. We discuss the results in terms of possible neurobiological causes underlying separable aging-related declines in inferior parietal cortex and lateral prefrontal cortex that differentially affect WM functions.