Working Memory In Individuals Research Articles

Cognitive reserve, cortisol, and Alzheimer's disease biomarkers: A memory clinic study.

Cognitive reserve might mitigate the risk of Alzheimer's dementia among memory clinic patients. No study has examined the potential modifying role of stress on this relation. We examined cross-sectional associations of the cognitive reserve index (CRI; education, occupational complexity, physical and leisure activities, and social health) with cognitive performance and AD-related biomarkers among 113 memory clinic patients. The longitudinal association between CRI and cognition over a 3-year follow-up was assessed. We examined whether associations were influenced by perceived stress and five measures of diurnal salivary cortisol. Higher CRI scores were associated with better cognition. Adjusting for cortisol measures reduced the beneficial association of CRI on cognition. A higher CRI score was associated with better working memory in individuals with higher (favorable) cortisol AM/PM ratio, but not among individuals with low cortisol AM/PM ratio. No association was found between CRI and AD-related biomarkers. Physiological stress reduces the neurocognitive benefits of cognitive reserve among memory clinic patients. Physiological stress may reduce the neurocognitive benefits accrued from cognitively stimulating and enriching life experiences (cognitive reserve [CR]) in memory clinic patients. Cortisol awakening response modified the relation between CR and P-tau181, a marker of Alzheimer's disease (AD). Effective stress management techniques for AD and related dementia prevention are warranted.

Physical activity improves the visual-spatial working memory of individuals with mild cognitive impairment or Alzheimer's disease: a systematic review and network meta-analysis.

Our network meta-analysis aimed to ascertain the effect of physical activity on the visual-spatial working memory of individuals with mild cognitive impairment and Alzheimer's disease as well as to propose tailored exercise interventions for each group. Employing a frequentist approach, we performed a network meta-analysis to compare the effectiveness of different exercise interventions in improving the visual-spatial working memory of individuals with mild cognitive impairment and Alzheimer's disease. Subsequently, we explored the moderating variables influencing the effectiveness of the exercise interventions through a subgroup analysis. We included 34 articles involving 3,074 participants in the meta-analysis, comprised of 1,537 participants from studies on mild cognitive impairment and 1,537 participants from studies on Alzheimer's disease. The articles included exhibited an average quality score of 6.6 (score studies) and 6.75 (reaction time [RT] studies), all passing the inconsistency test (p > 0.05). In the mild cognitive impairment literature, mind-body exercise emerged as the most effective exercise intervention (SMD = 0.61, 95% CI: 0.07-1.14). In Alzheimer's disease research, aerobic exercise was identified as the optimal exercise intervention (SMD = 0.39, 95% CI: 0.06-0.71). The results of the subgroup analysis suggest that the most effective approach to enhancing the visual-spatial working memory of individuals with mild cognitive impairment entails exercising at a frequency of three or more times per week for over 60 min each time and at a moderate intensity for more than 3 months. Suitable exercise options include mind-body exercise, multicomponent exercise, resistance exercise, and aerobic exercise. For individuals with Alzheimer's disease, we recommend moderately intense exercise twice per week for over 90 min per session and for a duration of 3 months or longer, with exercise options encompassing aerobic exercise and resistance exercise.

Chronic alcohol-induced long-lasting working memory deficits are associated with altered histone H3K9 dimethylation in the prefrontal cortex.

Epigenetic modifications have emerged as key contributors to the enduring behavioral, molecular and epigenetic neuroadaptations during withdrawal from chronic alcohol exposure. The present study investigated the long-term consequences of chronic alcohol exposure on spatial working memory (WM) and associated changes of transcriptionally repressive histone H3 lysine 9 dimethylation (H3K9me2) in the prefrontal cortex (PFC). Male C57BL/6 mice were allowed free access to either 12% (v/v) ethanol for 5 months followed by a 3-week abstinence period or water. Spatial WM was assessed through the spontaneous alternation T-maze test. Alcoholic and water mice received daily injections of GABAB agonist baclofen or saline during alcohol fading and early withdrawal. Global levels of histone modifications were determined by immunohistochemistry. Withdrawal mice displayed WM impairments along with reduced prefrontal H3K9me2 levels, compared to water-drinking mice. The withdrawal-induced decrease of H3K9me2 occurred concomitantly with increased level of permissive H3K9 acetylation (H3K9ac) in the PFC. Baclofen treatment rescued withdrawal-related WM deficits and fully restored prefrontal H3K9me2 and H3K9ac. Alcohol withdrawal induced brain region-specific changes of H3K9me2 and H3K9ac after testing, with significant decreases of both histone marks in the dorsal hippocampus and no changes in the amygdala and dorsal striatum. Furthermore, the magnitude of H3K9me2 in the PFC, but not the hippocampus, significantly and positively correlated with individual WM performances. No correlation was observed between H3K9ac and behavioral performance. Results also indicate that pre-testing intraperitoneal injection of UNC0642, a selective inhibitor of histone methyltransferase G9a responsible for H3K9me2, led to WM impairments in water-drinking and withdrawal-baclofen mice. Collectively, our results demonstrate that alcohol withdrawal induced brain-region specific alterations of H3K9me2 and H3K9ac, an effect that persisted for at least three weeks after cessation of chronic alcohol intake. The findings suggest a role for long-lasting decreased H3K9me2 specifically in the PFC in the persistent WM impairments related to alcohol withdrawal.

Effectiveness of Electroencephalography Neurofeedback for Improving Working Memory and Episodic Memory in the Elderly: A Meta-Analysis.

Background and Objective: Existing evidence indicates the potential benefits of electroencephalography neurofeedback (NFB) training for cognitive function. This study aims to comprehensively review all available evidence investigating the effectiveness of NFB on working memory (WM) and episodic memory (EM) in the elderly population. Material and Methods: A systematic search was conducted across five databases to identify clinical trials examining the impact of NFB on memory function in healthy elderly individuals or those with mild cognitive impairment (MCI). The co-primary outcomes focused on changes in WM and EM. Data synthesis was performed using a random-effects meta-analysis. Results: Fourteen clinical trials (n = 284) were included in the analysis. The findings revealed that NFB was associated with improved WM (k = 11, reported as Hedges' g = 0.665, 95% confidence [CI] = 0.473 to 0.858, p < 0.001) and EM (k = 12, 0.595, 0.333 to 0.856, p < 0.001) in the elderly, with moderate effect sizes. Subgroup analyses demonstrated that NFB had a positive impact on both WM and EM, not only in the healthy population (WM: k = 7, 0.495, 0.213 to 0.778, p = 0.001; EM: k = 6, 0.729, 0.483 to 0.976, p < 0.001) but also in those with MCI (WM: k = 6, 0.812, 0.549 to 1.074, p < 0.001; EM: k = 6, 0.503, 0.088 to 0.919, p = 0.018). Additionally, sufficient training time (totaling more than 300 min) was associated with a significant improvement in WM (k = 6, 0.743, 0.510 to 0.976, p < 0.001) and EM (k = 7, 0.516, 0.156 to 0.876, p = 0.005); however, such benefits were not observed in groups with inadequate training time. Conclusions: The results suggest that NFB is associated with enhancement of both WM and EM in both healthy and MCI elderly individuals, particularly when adequate training time (exceeding 300 min) is provided. These findings underscore the potential of NFB in dementia prevention or rehabilitation.

Wearable functional near-infrared spectroscopy for measuring dissociable activation dynamics of prefrontal cortex subregions during working memory.

The prefrontal cortex (PFC) has been extensively studied in relation to various cognitive abilities, including executive function, attention, and memory. Nevertheless, there is a gap in our scientific knowledge regarding the functionally dissociable neural dynamics across the PFC during a cognitive task and their individual differences in performance. Here, we explored this possibility using a delayed match-to-sample (DMTS) working memory (WM) task using NIRSIT, a high-density, wireless, wearable functional near-infrared spectroscopy (fNIRS) system. First, upon presentation of the sample stimulus, we observed an immediate signal increase in the ventral (orbitofrontal) region of the anterior PFC, followed by activity in the dorsolateral PFC. After the DMTS test stimulus appeared, the orbitofrontal cortex activated once again, while the rest of the PFC showed overall disengagement. Individuals with higher accuracy showed earlier and sustained activation of the PFC across the trial. Furthermore, higher network efficiency and functional connectivity in the PFC were correlated with individual WM performance. Our study sheds new light on the dynamics of PFC subregional activity during a cognitive task and its potential applicability in explaining individual differences in experimental, educational, or clinical populations. PRACTITIONER POINTS: Wearable functional near-infrared spectroscopy (fNIRS) captured dissociable temporal dynamics across prefrontal subregions during a delayed match-to-sample task. Anterior regions of the orbitofrontal cortex (OFC) activated first during the delay period, followed by the dorsolateral prefrontal cortex (PFC). PFC disengaged overall after the delay, but the OFC reactivated to the test stimulus. Earlier and sustained activation of PFC was associated with better accuracy. Functional connectivity and network efficiency also varied with task performance.

Enhancing cognitive flexibility and working memory in individuals with mild cognitive impairment: Exploring the impact of virtual reality on daily life activities

Mild Cognitive Impairment (MCI) serving as a transitional stage between normal aging and dementia. This study aimed to explore the impact of virtual reality (VR) on enhancing cognitive flexibility, working memory, and daily life activities. Forty participants diagnosed with MCI were randomly assigned to either an intervention group (N = 20) or a control group (N = 20). Evaluations were at baseline, post-training, and three months post-training using various cognitive assessment tools. Results showed that the VR-based cognitive rehabilitation significantly improved instrumental activities of daily living performance, visual and verbal working memory, and reduced anxiety and depression symptoms. While cognitive flexibility did not exhibit significant improvement, these findings highlight VR interventions as a potential avenue for improving cognitive and functional aspects, and alleviating psychological symptoms in individuals with MCI. Further research with larger sample sizes and extended follow-up periods is recommended to establish the long-term effectiveness of such interventions.

Effects of transcranial direct current stimulation and transcranial random noise stimulation on working memory and task-related EEG in major depressive disorder

ObjectiveTo compare effects of transcranial direct current stimulation (tDCS) and transcranial random noise stimulation with a direct-current offset (tRNS + DC-offset) on working memory (WM) performance and task-related electroencephalography (EEG) in individuals with Major Depressive Disorder (MDD). MethodsUsing a sham-controlled, parallel-groups design, 49 participants with MDD received either anodal tDCS (N = 16), high-frequency tRNS + DC-offset (N = 16), or sham stimulation (N = 17) to the left dorsolateral prefrontal cortex (DLPFC) for 20-minutes. The Sternberg WM task was completed with concurrent EEG recording before and at 5- and 25-minutes post-stimulation. Event-related synchronisation/desynchronisation (ERS/ERD) was calculated for theta, upper alpha, and gamma oscillations during WM encoding and maintenance. ResultstDCS significantly increased parieto-occipital upper alpha ERS/ERD during WM maintenance, observed on EEG recorded 5- and 25-minutes post-stimulation. tRNS + DC-offset did not significantly alter WM-related oscillatory activity when compared to sham stimulation. Neither tDCS nor tRNS + DC-offset improved WM performance to a significantly greater degree than sham stimulation. ConclusionsAlthough tDCS induced persistent effects on WM-related oscillatory activity, neither tDCS nor tRNS + DC-offset enhanced WM performance in MDD. SignificanceThis reflects the first sham-controlled comparison of tDCS and tRNS + DC-offset in MDD. These findings directly contrast with evidence of tRNS-induced enhancements in WM in healthy individuals.

Alternated emotional working memory in individuals with subclinical insomnia disorder: An electrophysiological study

The deleterious effects of sleep loss on sleep-dependent memory and emotional function have been documented in the current literature. Yet, the effects of insomnia-induced chronic sleep disturbance on emotional short-term memory have been scarcely investigated. Twenty-one participants with subclinical insomnia disorder (SID) and 20 healthy participants (healthy control, HC) performed a delayed recognition task of emotional faces, and event-related potentials (ERPs) involved in memory encoding, retention, and retrieval of faces across different emotional valences were assessed. Behavioral findings revealed that participants in the SID group had a larger response bias, being more likely to perceive negative faces as “old” faces presented in the retrieval phase than those in the HC group. ERP findings revealed that emotional faces in the SID vs. HC group induced significantly smaller P1 and late P3b and larger N170 amplitudes in the encoding phase and smaller negative slow wave (NSW) in the retention phase. In retrieval phase, the interaction between Sleep group and Valence were revealed for P1 and early P3b amplitudes, but no group differences were found after Bonferroni correction. These findings suggested that insomnia induced chronic sleep disturbance would influence performance on emotional working memory and induced processing phase specific regulation of neurophysiology in emotional working memory regardless of valence.

THE RELATIONSHIP OF TIME PERCEPTION WITH WORKING MEMORY IN PATIENTS WITH MULTIPLE SCLEROSIS

Objectives. Multiple Sclerosis (MS) is a chronic disease characterized by neuroinflammation of the central nervous system leading to progressive demyelination, loss of axons, and neurodegeneration. Meta-analyses have shown a cognitive impairment with a moderate effect size between healthy volunteers and MS patients, most apparently in working memory (WM), attention, and processing speed. It has recently been found that the perception of time has also been impaired in MS patients. This study aims to examine the relationship between WM and time perception in individuals with MS. Methods. Letter Number Sequencing Test (LNST), Time Interval Estimation Test, and Time Interval Production Test (TIPT) were administered to 50 MS patients. Individuals were allocated into low and high WM groups according to the median value of the LNST total score to compare time perception performance. Results. The mean age of the sample was 39.2. In the sample consisting of 14 male and 36 female participants, the mean number of educated years was 10.7 years, the age of disease onset was 31.9 years, and the duration of the disease was 7.2 years. A correlation was found between TIPT Ratio for 4 seconds and WM as well as disease severity. 29 people were in the low WM group and 21 people were in the high WM group. Age, age of disease onset, and the number of educated years were found to be higher in the high WM group. The TIPT Ratio for 4 seconds was lower in the high WM group. Conclusion. Consistent with the literature, a relationship was found between WM and time perception in individuals with MS in the 4 seconds, in which WM is considered to have a crucial role. The production of a 4- second interval was considered to be used as a marker reflecting both disease severity and WM capacity.

PAS‐MCI: Design and rationale for a randomized controlled trial to enhance prefrontal cortical plasticity and working memory in individuals with amnestic mild cognitive impairment

AbstractAmnestic Mild Cognitive Impairment (aMCI) is a prodromal stage to Alzheimer’s disease dementia (AD). Improving prefrontal cortical function in individuals with MCI could prevent progression from aMCI to AD. A key mechanism that has been linked to memory formation is cortical plasticity. Paired Associative Stimulation (PAS) is an intervention that uses transcranial magnetic stimulation (TMS) to enhance cortical plasticity. When delivered to the prefrontal cortex in individuals with AD, it has shown promise to improve prefrontal cortical plasticity and working memory.PAS‐MCI is a randomized controlled trial (RCT) that aims to assess: (1) dorsolateral prefrontal cortex (DLPFC) plasticity in individuals with aMCI compared to cognitively unimpaired control (CU) participants, (2) the efficacy of PAS delivered for 10 days bilaterally to the DLPFC of individuals with aMCI in enhancing their DLPFC plasticity, working memory, and executive function, and (3) whether changes in DLPFC plasticity mediate changes in working memory and executive function.100 aMCI and 50 CU control participants will be assessed clinically and cognitively, and undergo PAS combined with electroencephalography (PAS‐EEG) to characterize left DLPFC plasticity. The aMCI participants are randomized (1:1) to receive 10 daily sessions of either active or sham PAS delivered to the bilateral DLPFC. On Day 0, 7, and 28 following the PAS course, participants undergo repeat cognitive testing and PAS‐EEG to assess changes in working memory, executive function, and left DLPFC plasticity.As of February 1st, 2022, 14 aMCI and 9 CU participants consented, of which 5 aMCI and 4 CU participants completed the study. 7 aMCI participants were excluded because of: a contraindication for TMS (n = 1), having dementia (n = 1), and having non‐amnestic MCI (n = 5); 1 withdrew due to fatigue; and 1 is pending enrollment. 3 CU participants were excluded because of low cognitive scores; 1 withdrew due to not tolerating TMS; and 1 is pending enrollment.If successful, this RCT will establish the short‐term efficacy of PAS, a new TMS approach to enhance prefrontal cortical function in individuals with aMCI. A follow‐up longer‐term trial will be then needed to assess whether PAS could prevent cognitive decline and progression to AD.

Working Memory Constrains Long-Term Memory in Children and Adults: Memory of Objects and Bindings

We explored how individual and age-related differences in working memory (WM) capacity affected subsequent long-term memory (LTM) retrieval. Unlike past studies, we tested WM and LTM not only for items, but also for item-color bindings. Our sample included 82 elementary school children and 42 young adults. The participants performed a WM task with images of unique everyday items presented sequentially at varying set sizes in different colors. Later, we tested LTM for items and item-color bindings from the WM task. The WM load during encoding constrained LTM, and participants with a higher WM capacity retrieved more items in the LTM test. Even when accounting for young children's poor item memory by considering only the items that they did remember, they exhibited an exacerbated difficulty with remembering item-color bindings in WM. Their LTM binding performance, however, as a proportion of remembered objects, was comparable to that of older children and adults. The WM binding performance was better during sub-span encoding loads, but with no clear transfer of this benefit to LTM. Overall, LTM item memory performance was constrained by individual and age-related WM limitations, but with mixed consequences for binding. We discuss the theoretical, practical, and developmental implications of this WM-to-LTM bottleneck.

Working memory control dynamics follow principles of spatial computing

Working memory (WM) allows us to remember and selectively control a limited set of items. Neural evidence suggests it is achieved by interactions between bursts of beta and gamma oscillations. However, it is not clear how oscillations, reflecting coherent activity of millions of neurons, can selectively control individual WM items. Here we propose the novel concept of spatial computing where beta and gamma interactions cause item-specific activity to flow spatially across the network during a task. This way, control-related information such as item order is stored in the spatial activity independent of the detailed recurrent connectivity supporting the item-specific activity itself. The spatial flow is in turn reflected in low-dimensional activity shared by many neurons. We verify these predictions by analyzing local field potentials and neuronal spiking. We hypothesize that spatial computing can facilitate generalization and zero-shot learning by utilizing spatial component as an additional information encoding dimension.

The effect of a virtual reality based intervention on processing speed and working memory in individuals with ADHD—A pilot-study

Introduction: This study aimed to evaluate the effectiveness of a virtual reality based intervention in processing speed and working memory in students with ADHD symptomatology.Methods: A randomized experimental study was conducted, with a sample consisting of 25 adult participants recruited from the Escola Superior de Saúde do Politécnico do Porto. The participants were allocated into two groups: a passive control group and an intervention group that completed 10 sessions using virtual reality-based games from the Enhance VR app. The intervention included 6 games: Whack-a-mole, Shuffled, Assembly, React, Memory Wall, and Maestro. The participants underwent pre- and post-intervention evaluations using the Southwestern Assessment of Processing Speed (SWAPS) and the Sequence of Letters and Numbers and Spatial Location of the Wechsler Adult Intelligence Scale - 3rd Edition - WAIS-III. Descriptive statistics were used to characterize the sample and a mixed ANOVA was used to test the effectiveness of the intervention.Results: There was an improvement in the results of processing speed in the group exposed to the intervention (p &amp;lt; 0.001) and the value of the interaction between intervention and time was also significant (p = 0.004). There were no statistically significant differences between the participants’ working memory in the different variables under study, except for the values of the Spatial location test in the experimental group that improved relative to the initial assessment (p = 0.034).Discussion: A virtual reality cognitive training intervention resulted in improvements in the processing speed measures, which were not found in the control group. Although we cannot make the same conclusions regarding working memory, these results suggest that the VR intervention resulted in progress in the experimental group, possibly influenced by the intervention, which should be verified in future studies with longer interventions.

Efficacy of Transcranial Alternating Current Stimulation in the Enhancement of Working Memory Performance in Healthy Adults: A Systematic Meta-Analysis

BackgroundTranscranial alternating current stimulation (tACS)—a noninvasive brain stimulation technique that modulates cortical oscillations in the brain—has shown the capacity to enhance working memory (WM) abilities in healthy individuals. The efficacy of tACS in the improvement of WM performance in healthy individuals is not yet fully understood. Objective/HypothesisThis meta-analysis aimed to systematically evaluate the efficacy of tACS in the enhancement of WM in healthy individuals and to assess moderators of response to stimulation. We hypothesized that active tACS would significantly enhance WM compared with sham. We further hypothesized that it would do so in a task-dependent manner and that differing stimulation parameters would affect response to tACS. Materials and MethodsTen tACS studies met the inclusion criteria and provided 32 effects in the overall analysis. Random-effect models assessed mean change scores on WM tasks from baseline to poststimulation. The included studies involved varied in stimulation parameters, between-subject and within-subject study designs, and online vs offline tACS. ResultsWe observed a significant, heterogeneous, and moderate effect size for active tACS in the enhancement of WM performance over sham (Cohen’s d = 0.5). Cognitive load, task domain, session number, and stimulation region showed a significant relationship between active tACS and enhanced WM behavior over sham. ConclusionsOur findings indicate that active tACS enhances WM performance in healthy individuals compared with sham. Future randomized controlled trials are needed to further explore key parameters, including personalized stimulation vs standardized electroencephalography frequencies and maintenance of tACS effects, and whether tACS-induced effects translate to populations with WM impairments.

Neural mechanism of food-related working memory in individuals with overweight/obesity and related intervention

Neural mechanism of food-related working memory in individuals with overweight/obesity and related intervention

Working memory function in patients with major depression disorder: A narrative review.

Working memory (WM) deficits are recognized as serious cognitive impairment in patients with major depressive disorder (MDD). This review aims to clarify the effects of impaired WM function in patients with MDD and explore non-invasive and effective treatments that can be adopted in clinical practice. This review (1) synthesizes extant literature examining brain function and brain areas in terms of WM in individuals with depression, (2) utilizes the outcomes of the studies presented in this review to discuss the effects of impaired WM function on cognitive processing in individuals with depression, (3) integrates the treatments explored in current studies and (4) provides some suggestions for future research. We found that (1) central executive (CE) components affect the processing of WM, and this might be one of the factors influencing cognitive biases, as it is implicated in repetitive negative thinking and rumination; (2) the left dorsal anterior cingulate cortex (dACC), the left dorsolateral prefrontal cortex (DLPFC) and the regions of the default mode network (DMN) play a vital role in CE functioning; and (3) psychotherapy, cognitive training, exercise and physical therapy can be used as complementary treatments for MDD.

EFEITOS DO TREINO DE MEMÓRIA OPERACIONAL NA COGNIÇÃO DE IDOSOS SAUDÁVEIS: UM ESTUDO DE REVISÃO SISTEMÁTICA

ABSTRACT. The working memory (WM) training in older adults can benefit their cognition. However, there is a dearth of literature reviews on the subject. Objective: This study aimed to investigate and evaluate the effects of WM training on the cognition of healthy older adults, in individual and group interventions reported in the literature. Methods: This is a systematic review involving a qualitative analysis of publications on the SciELO, LILACS, and MEDLINE databases carried out between March and June 2021. Results: A total of 47 studies were identified and analyzed, comprising 40 in older adults only and 7 comparing older and younger adults, investigating individual or group WM training or other types of intervention focused on WM effects. Conclusions: Both individual and group intervention contributed to the maintenance and/or improvement of cognition in older adults exploiting brain plasticity to promote mental health and prevent cognitive problems that can negatively impact quality of life of this group.

The Effects of Processing Instruction and Output-Based Activities on Grammar Learning: The Mediating Role of Working Memory

Processing instruction (PI) is an input-based approach to grammar education based on input processing theory, and output is another element needed for second-language acquisition to be successful. This study sought to examine the impact of PI and output-based activities with the mediating role of working memory (WM) capacity on learning English future tense. To this end, 99 subjects with preintermediate command of English based on an Oxford Placement Test were recruited for the study, and they were divided into three groups: PI, output, and control, with 33 learners in each group. Using a reading-span test, it was revealed that 14 subjects in the PI group, 15 participants in the output group, and 13 learners in the comparison group had low WM, while the rest individuals had high WM capacity. Then, a two-way between-group analysis of variance and a Bonferroni adjustment post hoc test were performed. The results of the analyses showed that both PI and output groups outperformed the control group. Additionally, there was no difference in grammar gain between PI and output groups. Besides, learners with high WM outperformed low WM individuals. The pedagogical implication of this research is that PI and output-based activities can assist teachers in implementing effective strategies to raise L2 learners’ knowledge and consciousness.

The Neural Mechanism Underlying Visual Working Memory Training and Its Limited Transfer Effect.

Visual working memory (VWM) training has been shown to improve performance in trained tasks with limited transfer to untrained tasks. The neural mechanism underlying this limited transfer remains unknown. In the present study, this issue was addressed by combining model-fitting methods with EEG recordings. Participants were trained on a color delay estimation task for 12 consecutive 1-hr sessions, and the transfer effect was evaluated with an orientation change detection task. The EEG responses during both tasks were collected in a pretraining test, a posttraining test conducted 1 day after training, and a follow-up test conducted 3 months after training. According to our model-fitting results, training significantly improved the capacity but not the precision of color working memory (WM), and this capacity improvement did not transfer to the orientation change detection task, spatial 2-back task, symmetry span task, or Raven reasoning test. The EEG results revealed that training resulted in a specific and sustained increase in parietal theta power suppression in the color WM task, which reflected individual color WM capacity. In contrast, the increase in parietal-temporal alpha power, which reflected individual orientation WM capacity, did not change with training. Together, these findings suggest that the simultaneous change of stimulus type and task structure would modulate the cognitive and neural substrates of WM tasks and introduce additional constraints for the transfer of WM training.

Comparing resting-state connectivity of working memory networks in U.S. Service members with mild traumatic brain injury and posttraumatic stress disorder

Mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) are prevalent among military populations, and both have been associated with working memory (WM) impairments. Previous resting-state functional connectivity (rsFC) research conducted separately in PTSD and mTBI populations suggests that there may be similar and distinct abnormalities in WM-related networks. However, no studies have compared rsFC of WM brain regions in participants with mTBI versus PTSD. We used resting-state fMRI to investigate rsFC of WM networks in U.S. Service Members (n = 127; ages 18–59) with mTBI only (n = 46), PTSD only (n = 24), and an orthopedically injured (OI) control group (n = 57). We conducted voxelwise rsFC analyses with WM brain regions to test for differences in WM network connectivity in mTBI versus PTSD. Results revealed reduced rsFC between ventrolateral prefrontal cortex (vlPFC), lateral premotor cortex, and dorsolateral prefrontal cortex (dlPFC) WM regions and brain regions in the dorsal attention and somatomotor networks in both mTBI and PTSD groups versus controls. When compared to those with mTBI, individuals with PTSD had lower rsFC between both the lateral premotor WM seed region and middle occipital gyrus as well as between the dlPFC WM seed region and paracentral lobule. Interestingly, only vlPFC connectivity was significantly associated with WM performance across the samples. In conclusion, we found primarily overlapping patterns of reduced rsFC in WM brain regions in both mTBI and PTSD groups. Our finding of decreased vlPFC connectivity associated with WM is consistent with previous clinical and neuroimaging studies. Overall, these results provide support for shared neural substrates of WM in individuals with either mTBI or PTSD.