Activating Developmental Reserve Capacity Via Cognitive Training or Non-invasive Brain Stimulation: Potentials for Promoting Fronto-Parietal and Hippocampal-Striatal Network Functions in Old Age

Effective engagement in computerized cognitive training for older adults

Computerized cognitive training (CCT) is a frontline therapy to prevent or slow age-related cognitive decline. A prerequisite for CCT research to provide clinically relevant improvements in cognition is to understand effective engagement, i.e., the pattern of energy investment that ensures CCT effectiveness. Even though previous studies have assessed whether particular variables (e.g., gamification) predict engagement and/or CCT effectiveness, the field lacks a systematic approach to understanding effective engagement. Here, by comprehensively reviewing and evaluating engagement and adjacent literature, we propose a standardized measurement and operational framework to promote effective engagement with CCT targeting cognitive decline in older adults. We suggest that promoting effective engagement with CCT has two key steps: 1) comprehensively measuring engagement with CCT and 2) identifying which aspects of engagement are essential to achieve the pre-specified outcome of clinically relevant improvements in cognition. The proposed measurement and operational framework of effective engagement will allow future research to maximize older adults' engagement with CCT to slow/prevent age-related cognitive decline.

Defining the concept of reserve in the motor domain: a systematic review

A reserve in the motor domain may underlie the capacity exhibited by some patients to maintain motor functionality in the face of a certain level of disease. This form of "motor reserve" (MR) could include cortical, cerebellar, and muscular processes. However, a systematic definition has not been provided yet. Clarifying this concept in healthy individuals and patients would be crucial for implementing prevention strategies and rehabilitation protocols. Due to its wide application in the assessment of motor system functioning, non-invasive brain stimulation (NIBS) may support such definition. Here, studies focusing on reserve in the motor domain and studies using NIBS were revised. Current literature highlights the ability of the motor system to create a reserve and a possible role for NIBS. MR could include several mechanisms occurring in the brain, cerebellum, and muscles, and NIBS may support the understanding of such mechanisms.

Optical coherence tomography as a potential surrogate marker of dopaminergic modulation across the life span

The retina has been considered a "window to the brain" and shares similar innervation by the dopaminergic system with the cortex in terms of an unequal distribution of D1 and D2 receptors. Here, we provide a comprehensive overview that Optical Coherence Tomography (OCT), a non-invasive imaging technique, which provides an "in vivo" representation of the retina, shows promise to be used as a surrogate marker of dopaminergic neuromodulation in cognition. Overall, most evidence supports reduced retinal thickness in individuals with dopaminergic dysregulation (e.g., patients with Parkinson's Disease, non-demented older adults) and with poor cognitive functioning. By using the theoretical framework of metacontrol, we derive hypotheses that retinal thinning associated to decreased dopamine (DA) levels affecting D1 families, might lead to a decrease in the signal-to-noise ratio (SNR) affecting cognitive persistence (depending on D1-modulated DA activity) but not cognitive flexibility (depending on D2-modulated DA activity). We argue that the use of OCT parameters might not only be an insightful for cognitive neuroscience research, but also a potentially effective tool for individualized medicine with a focus on cognition. As our society progressively ages in the forthcoming years and decades, the preservation of cognitive abilities and promoting healthy aging will hold of crucial significance. OCT has the potential to function as a swift, non-invasive, and economical method for promptly recognizing individuals with a heightened vulnerability to cognitive deterioration throughout all stages of life.

The effect of cognitive training on children with attention deficit and hyperactivity disorder: A meta-analysis

OBJECTIVE

This document is a meta-analysis of randomized controlled trials that evaluated the effect of cognitive training interventions on attention deficit and hyperactivity disorder (ADHD) symptoms.

METHODS

A systematic literature search was conducted using databases such as PubMed, Web of Science, and Embase from the inception of each database to April 28, 2022. Data were analyzed using Stata 15 software. The risk of bias assessment was conducted using five domains from the Cochrane Collaborations tool.

RESULTS

A total of 10 studies with 446 children with ADHD were included. The results showed that cognitive training was effective in improving attention symptoms [SMD= -0.78 (95% CI: -1.46, -0.1)] and executive function [SMD = -0.3 (95% CI: -0.56, -0.05)] in children with ADHD compared to controls. No significant difference in the degree of improvement in hyperactivity/impulsivity with cognitive training compared to the control group [SMD = -0.65 (95% CI: -1.35, 0.05)]. In addition, subgroup analyses also found that cognitive training significantly improved attention in children with ADHD <10 years of age [SMD = -1.3 (95% CI: -2.58, -0.02)] and children with ADHD with length of training >30 days [SMD = -0.94 (95% CI: -1.81, -0.07)] compared to controls.

CONCLUSION

This meta-analysis found that the beneficial effects of cognitive training on attention (particularly for children with ADHD <10 years old and >30 days of training) and executive function in children with ADHD, but not on hyperactivity/impulsivity.

The Efficacy of Cognitive Training on Neuropsychological Outcomes in Mild Cognitive Impairment: A Meta-Analysis

Mild cognitive impairment (MCI) or mild neurocognitive disorder is an intermediate stage of cognitive impairment between normal cognitive aging and dementia. Given the absence of effective pharmacological treatments for MCI, increasing numbers of studies are attempting to understand how cognitive training (CT) could benefit MCI. This meta-analysis aims to update and assess the efficacy of CT on specific neuropsychological test performance (global cognitive functioning, short-term verbal memory, long-term verbal memory, generativity, working memory, and visuospatial abilities) in individuals diagnosed with MCI, as compared to MCI control groups. After searching electronic databases for randomized controlled trials, 31 studies were found including 2496 participants. Results showed that CT significantly improved global cognitive functioning, short-term and long-term verbal memory, generativity, working memory, and visuospatial abilities. However, no significant effects were observed for shifting, abstraction ability/concept formation, processing speed, and language. The mode of CT had a moderating effect on abstraction ability/concept formation. The findings provide specific insights into the cognitive functions influenced by CT and guide the development of tailored interventions for MCI. While CT holds promise, further research is needed to address certain cognitive deficits and assess long-term effects on dementia progression.

Resilience to depression: Implication for psychological vaccination

From the vulnerability perspective, we often ask the question "why someone suffers from depression?" Despite outstanding achievements along this line, we still face high occurrence or recurrence and unsatisfied therapeutic efficacy of depression, suggesting that solely focusing on vulnerability perspective is insufficient to prevent and cure depression. Importantly, although experiencing same adversity, most people do not suffer from depression but manifest certain resilience, which could be used to prevent and cure depression, however, the systematic review is still lack. Here, we propose the concept "resilience to depression" to emphasize resilient diathesis against depression, by asking the question "why someone is exempted from depression?" Research evidence of resilience to depression has been reviewed systematically: positive cognitive style (clear purpose in life, hopefulness, et al.), positive emotion (emotional stability, et al.), adaptive behavior (extraversion, internal self-control, et al.), strong social interaction (gratitude and love, et al.), and neural foundation (dopamine circuit, et al.). Inspired by these evidence, "psychological vaccination" could be achieved by well-known real-world natural-stress vaccination (mild, controllable, and adaptive of stress, with help from parents or leaders) or newly developed "clinical vaccination" (positive activity intervention for current depression, preventive cognitive therapy for remitted depression, et al.), both of which aim to enhance the resilient psychological diathesis against depression, through events or training. Potential neural circuit vaccination was further discussed. This review calls for directing attention to resilient diathesis against depression, which offers a new thinking "psychological vaccination" in both prevention and therapy of depression.

Does the combination of exercise and cognitive training improve working memory in older adults? A systematic review and meta-analysis

Background

Cognitive functioning is dependent on working memory and a decline in working memory is the main cause of cognitive aging. Many studies have suggested that physical exercise or cognitive intervention can effectively improve working memory in the elderly. However, it is still unknown whether a combination of exercise and cognitive training (CECT) is more effective than either intervention alone. The present systematic review and meta-analysis were undertaken to evaluate the effect of CECT on working memory in the elderly.

Methods

The review was registered in the International Prospective Systematic Review (PROSPERO, CRD42021290138). Systematic searches were conducted on Web of Science, Elsevier Science, PubMed and Google Scholar. The data were extracted according to the PICOS framework. Comprehensive meta-analysis (CMA) software was used to perform the meta-analysis, moderator analysis and publication bias testing.

Results

The current meta-analysis included 21 randomized controlled trials (RCT). Results showed that CECT had a significantly greater impact on working memory in older adults compared to no intervention groups (SMD = 0.29, 95% CI [0.14-0.44], p < 0.01), with no significant difference between CECT and exercise (SMD = 0.16, 95% CI [-0.04-0.35], p = 0.12) or cognitive intervention alone (SMD = 0.08, 95% CI [-0.13-0.30], p = 0.44). Furthermore, the positive effect of CECT was moderated by intervention frequency and cognitive state.

Conclusions

The CECT can effectively improve working memory of older adults, but the effect of CECT compared to single intervention needs to be further explored.

The relationship between cognitive reserve and cognition in healthy adults: a systematic review

The concept of Cognitive Reserve (CR) refers to the individual differences allowing some people to cope better with brain pathology. The aim of the present review was to explore the relationship between CR and cognition in adulthood. This association has been addressed in several neuro(psycho)logical disorders and in healthy elderly people. However, few studies explored this issue in adulthood (age range 18–65), when individuals might take advantage the most from psychoeducational approaches aimed at increasing CR. For our systematic review, we selected studies assessing CR and adopting neuropsychological and experimental tasks for evaluation of cognitive functioning in healthy individuals. In the selected articles, we examined the relationship of singular proxies, composite indexes or standardized scales of CR with measures of general cognition, attention, inhibitory control, verbal fluency, constructional abilities, and verbal and spatial memory. The results suggested a positive relationship between singular CR proxies, composite indexes or standardized scales, and almost all the explored cognitive domains. No clear conclusion could be made on constructional abilities due to the scarcity of available studies. CR seems associated with better cognitive performance in adulthood, but definite methodological improvements and the use of standardized scales for CR are necessary to reduce inconsistencies among studies.

Modulation of network centrality and gray matter microstructure using multi-session brain stimulation and memory training

Neural mechanisms of behavioral improvement induced by repeated transcranial direct current stimulation (tDCS) combined with cognitive training are yet unclear. Previously, we reported behavioral effects of a 3-day visuospatial memory training with concurrent anodal tDCS over the right temporoparietal cortex in older adults. To investigate intervention-induced neural alterations we here used functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) datasets available from 35 participants of this previous study, acquired before and after the intervention. To delineate changes in whole-brain functional network architecture, we employed eigenvector centrality mapping. Gray matter alterations were analyzed using DTI-derived mean diffusivity (MD). Network centrality in the bilateral posterior temporooccipital cortex was reduced after anodal compared to sham stimulation. This focal effect is indicative of decreased functional connectivity of the brain region underneath the anodal electrode and its left-hemispheric homolog with other "relevant" (i.e., highly connected) brain regions, thereby providing evidence for reorganizational processes within the brain's network architecture. Examining local MD changes in these clusters, an interaction between stimulation condition and training success indicated a decrease of MD in the right (stimulated) temporooccipital cluster in individuals who showed superior behavioral training benefits. Using a data-driven whole-brain network approach, we provide evidence for targeted neuromodulatory effects of a combined tDCS-and-training intervention. We show for the first time that gray matter alterations of microstructure (assessed by DTI-derived MD) may be involved in tDCS-enhanced cognitive training. Increased knowledge on how combined interventions modulate neural networks in older adults, will help the development of specific therapeutic interventions against age-associated cognitive decline.

Feasibility of Cognitive Training in Combination With Transcranial Direct Current Stimulation in a Home-Based Context (TrainStim-Home): study protocol for a randomised controlled trial

INTRODUCTION

With the worldwide increase of life expectancy leading to a higher proportion of older adults experiencing age-associated deterioration of cognitive abilities, the development of effective and widely accessible prevention and therapeutic measures has become a priority and challenge for modern medicine. Combined interventions of cognitive training and transcranial direct current stimulation (tDCS) have shown promising results for counteracting age-associated cognitive decline. However, access to clinical centres for repeated sessions is challenging, particularly in rural areas and for older adults with reduced mobility, and lack of clinical personnel and hospital space prevents extended interventions in larger cohorts. A home-based and remotely supervised application of tDCS would make the treatment more accessible for participants and relieve clinical resources. So far, studies assessing feasibility of combined interventions with a focus on cognition in a home-based setting are rare. With this study, we aim to provide evidence for the feasibility and the effects of a multisession home-based cognitive training in combination with tDCS on cognitive functions of healthy older adults.

METHODS AND ANALYSIS

The TrainStim-Home trial is a monocentric, randomised, double-blind, placebo-controlled study. Thirty healthy participants, aged 60-80 years, will receive 2 weeks of combined cognitive training and anodal tDCS over left dorsolateral prefrontal cortex (target intervention), compared with cognitive training plus sham stimulation. The cognitive training will comprise a letter updating task, and the participants will be stimulated for 20 min with 1.5 mA. The intervention sessions will take place at the participants' home, and primary outcome will be the feasibility, operationalised by two-thirds successfully completed sessions per participant. Additionally, performance in the training task and an untrained task will be analysed.

ETHICS AND DISSEMINATION

Ethical approval was granted by the ethics committee of the University Medicine Greifswald. Results will be available through publications in peer-reviewed journals and presentations at national and international conferences.

TRIAL REGISTRATION NUMBER

NCT04817124.

Neuromodulation through brain stimulation-assisted cognitive training in patients with post-COVID-19 cognitive impairment (Neuromod-COV): study protocol for a PROBE phase IIb trial

INTRODUCTION

A substantial number of patients diagnosed with COVID-19 experience long-term persistent symptoms. First evidence suggests that long-term symptoms develop largely independently of disease severity and include, among others, cognitive impairment. For these symptoms, there are currently no validated therapeutic approaches available. Cognitive training interventions are a promising approach to counteract cognitive impairment. Combining training with concurrent transcranial direct current stimulation (tDCS) may further increase and sustain behavioural training effects. Here, we aim to examine the effects of cognitive training alone or in combination with tDCS on cognitive performance, quality of life and mental health in patients with post-COVID-19 subjective or objective cognitive impairments.

METHODS AND ANALYSIS

This study protocol describes a prospective randomised open endpoint-blinded trial. Patients with post-COVID-19 cognitive impairment will either participate in a 3-week cognitive training or in a defined muscle relaxation training (open-label interventions). Irrespective of their primary intervention, half of the cognitive training group will additionally receive anodal tDCS, all other patients will receive sham tDCS (double-blinded, secondary intervention). The primary outcome will be improvement of working memory performance, operationalised by an n-back task, at the postintervention assessment. Secondary outcomes will include performance on trained and untrained tasks and measures of health-related quality of life at postassessment and follow-up assessments (1 month after the end of the trainings).

ETHICS AND DISSEMINATION

Ethical approval was granted by the Ethics Committee of the University Medicine Greifswald (number: BB 066/21). Results will be available through publications in peer-reviewed journals and presentations at national and international conferences.

TRIAL REGISTRATION NUMBER

NCT04944147.

Toward noninvasive brain stimulation 2.0 in Alzheimer's disease

Noninvasive brain stimulation techniques (NiBS) have gathered substantial interest in the study of dementia, considered their possible role in help defining diagnostic biomarkers of altered neural activity for early disease detection and monitoring of its pathophysiological course, as well as for their therapeutic potential of boosting residual cognitive functions. Nevertheless, current approaches suffer from some limitations. In this study, we review and discuss experimental NiBS applications that might help improve the efficacy of future NiBS uses in Alzheimer's Disease (AD), including perturbation-based biomarkers for early diagnosis and disease tracking, solutions to enhance synchronization of oscillatory electroencephalographic activity across brain networks, enhancement of sleep-related memory consolidation, image-guided stimulation for connectome control, protocols targeting interneuron pathology and protein clearance, and finally hybrid-brain models for in-silico modeling of AD pathology and personalized target selection. The present work aims to stress the importance of multidisciplinary, translational, model-driven interventions for precision medicine approaches in AD.

Shared Decision-Making in Breast Reconstruction for Breast Cancer Patients: A Scoping Review

For most breast cancer (BC) patients who have undergone a mastectomy, the decision whether to proceed with breast reconstruction (BR) is complicated and requires deliberation. Shared decision-making (SDM) helps to address those needs and promote informed value-based decisions. However, little is known about the SDM status for BR in BC patients. This scoping review describes: 1) basic characteristics of studies on BR SDM in BC patients; 2) factors influencing BR SDM in BC patients; 3) experience and perception of BR SDM in BC patients; and 4) outcome measures reported. This review was performed in accordance with the Arksey and O'Malley methodology. A total of 5 English and 4 Chinese databases were searched, as well as different sources from grey literature. The data extraction form was developed by referring to the objectives and the Ottawa Decision Support Framework (ODSF). Data was analyzed using thematic analysis, framework analysis and descriptive statistics, with findings presented in the tables and diagrams. A total of 1481 records were retrieved and 42 of these included after screening. In 21 (21/42, 50%) of the studies, patient decision aids (PDAs) were utilized, and in 17 (17/42, 40.48%) of the studies, the factors influencing the implementation of SDM were explored. Of these 17 studies, the factors influencing the implementation of SDM were categorized into the following: the patient level (17/17, 100%), the healthcare level (2/17, 11.76%) and the organizational and system level (7/17, 41.18%). A total of 8 (19.05%) of the 42 studies focused on patients' experiences and perceptions of SDM, and all studies used qualitative research methods. Of these 8 studies, a total of 7 (7/8, 87.50%) focused on patients' experiences of SDM participation, and 4 (4/8, 50.00%) focused on patients' perceptions of SDM. A total of 24 studies (24/42, 57.14%) involved quantitative outcome measures, where 49 items were divided into three classifications according to the outcomes of ODSF: the quality of the decision (17/24, 70.83%), the quality of the decision-making process (20/24, 83.33%), and impact (13/24, 54.17%). Although researchers have paid less attention to other research points in the field of SDM, compared to the design and application of SDM interventional tools, the research team still presents some equally noteworthy points through scoping review. For instance, the various factors influencing BC patients' participation in SDM for BR (especially at the healthcare provider level and at the organizational system level), patients' experiences and perceptions. Systematic reviews (SRs) should be conducted to quantify the impact of these different factors on BR SDM. Implementation of scientific theories and methods can inform the exploration and integration of these factors.

Mindfulness Training Improves Cognition and Strengthens Intrinsic Connectivity Between the Hippocampus and Posteromedial Cortex in Healthy Older Adults

Maintaining optimal cognitive functioning throughout the lifespan is a public health priority. Evaluation of cognitive outcomes following interventions to promote and preserve brain structure and function in older adults, and associated neural mechanisms, are therefore of critical importance. In this randomized controlled trial, we examined the behavioral and neural outcomes following mindfulness training (n = 72), compared to a cognitive fitness program (n = 74) in healthy, cognitively normal, older adults (65-80 years old). To assess cognitive functioning, we used the Preclinical Alzheimer Cognitive Composite (PACC), which combines measures of episodic memory, executive function, and global cognition. We hypothesized that mindfulness training would enhance cognition, increase intrinsic functional connectivity measured with magnetic resonance imaging (MRI) between the hippocampus and posteromedial cortex, as well as promote increased gray matter volume within those regions. Following the 8-week intervention, the mindfulness training group showed improved performance on the PACC, while the control group did not. Furthermore, following mindfulness training, greater improvement on the PACC was associated with a larger increase in intrinsic connectivity within the default mode network, particularly between the right hippocampus and posteromedial cortex and between the left hippocampus and lateral parietal cortex. The cognitive fitness training group did not show such effects. These findings demonstrate that mindfulness training improves cognitive performance in cognitively intact older individuals and strengthens connectivity within the default mode network, which is particularly vulnerable to aging affects. Clinical Trial Registration: [https://clinicaltrials.gov/ct2/show/NCT02628548], identifier [NCT02628548].

The ageing of the social mind: replicating the preservation of socio-affective and the decline of socio-cognitive processes in old age

Anticipating population ageing to reach a historically unprecedented level in this century and considering the public goal of promoting well-being until old age, research in many fields has started to focus on processes and factors that contribute to healthy ageing. Since human interactions have a tremendous impact on our mental and physical well-being, scientists are increasingly investigating the basic processes that enable successful social interactions such as social affect (empathy, compassion) and social cognition (Theory of Mind). However, regarding the replication crisis in psychological science it is crucial to probe the reproducibility of findings revealed by each specific method. To this end, we aimed to replicate the effect of age on empathy, compassion and Theory of Mind observed in Reiter and colleagues' study (Reiter et al. 2017 Sci. Rep. 7, 11046 (doi:10.1038/s41598-017-10669-4)) by using the same ecologically valid paradigm in an independent sample with similar age ranges. We were able to replicate the previously observed results of a preservation or even enhancement in socio-affective processes, but a decline in socio-cognitive processes for older adults. Our findings add to the understanding of how social affect and cognition change across the adult lifespan and may suggest targets for intervention studies aiming to foster successful social interactions and well-being until advanced old age.

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.

Dissociating direct and indirect effects: a theoretical framework of how latent toxoplasmosis affects cognitive profile across the lifespan

About one-third of the world's population has latent toxoplasmosis, which is typically most prevalent in old age due to its lifelong persistence. Most infected people do not reveal clinically relevant symptoms, but T. gondii might trigger cognitive changes in otherwise asymptomatic individuals. As intact cognitive processes are essential for various achievements and successful aging, this review focuses on the cognitive profile associated with latent toxoplasmosis across the lifespan. It could be explained by a shift in balance between direct effects (increased dopamine synthesis) and indirect effects (neurodegeneration and chronic inflammation, which can decrease dopamine levels). Based thereon, we provide a possibly comprehensive framework of how T. gondii can differently affect cognitive performance across the lifespan (i.e., from increased catecholaminergic signaling in young age to decreased signaling in old age). We outline how future studies may inform our knowledge on the role of individual differences in response to T. gondii and how longitudinal studies can help trace the temporal dynamics in the shift of the balance between direct and indirect effects.

BRAINSTORMING: A study protocol for a randomised double-blind clinical trial to assess the impact of concurrent brain stimulation (tDCS) and working memory training on cognitive performance in Acquired Brain Injury (ABI)

Background

Acquired Brain Injury (ABI) admissions have an incidence of 385 per 100,000 of the population in the UK, and as brain injury often involves the frontal networks, cognitive domains affected are likely to be executive control, working memory, and problem-solving deficits, resulting in difficulty with everyday activities. The above observations make working memory, and related constructs such as attention and executive functioning attractive targets for neurorehabilitation. We propose a combined home-based rehabilitation protocol involving the concurrent administration of a working memory training program (adaptive N-back task) with non-invasive transcranial direct current stimulation (tDCS) of the right dorsolateral prefrontal cortex to promote long-lasting modification of brain areas underlying working memory function.

Method

Patients with a working memory deficit will be recruited and assigned to two age-matched groups receiving working memory training for 2 weeks: an active group, receiving tDCS (2 mA for 20 min), and a control group, receiving sham stimulation. After the end of the first 2 weeks, both groups will continue the working memory training for three more weeks. Outcome measures will be recorded at timepoints throughout the intervention, including baseline, after the 2 weeks of stimulation, at the end of the working memory training regimen and 1 month after the completion of the training.

Discussion

The aim of the study is to assess if non-invasive tDCS stimulation has an impact on performance and benefits of a working memory training regimen. Specifically, we will examine the impact of brain stimulation on training gains, if changes in gains would last, and whether changes in training performance transfer to other cognitive domains. Furthermore, we will explore whether training improvements impact on everyday life activities and how the home-based training regimen is received by participants, with the view to develop an effective home healthcare tool that could enhance working memory and daily functioning.

Trial registration

This study was registered with clinicaltrials.gov: NCT04010149 on July 8, 2019.

Cognitive training and brain stimulation in prodromal Alzheimer's disease (AD-Stim)-study protocol for a double-blind randomized controlled phase IIb (monocenter) trial

BACKGROUND

Given the growing older population worldwide, and the associated increase in age-related diseases, such as Alzheimer's disease (AD), investigating non-invasive methods to ameliorate or even prevent cognitive decline in prodromal AD is highly relevant. Previous studies suggest transcranial direct current stimulation (tDCS) to be an effective method to boost cognitive performance, especially when applied in combination with cognitive training in healthy older adults. So far, no studies combining tDCS concurrent with an intense multi-session cognitive training in prodromal AD populations have been conducted.

METHODS

The AD-Stim trial is a monocentric, randomized, double-blind, placebo-controlled study, including a 3-week tDCS-assisted cognitive training with anodal tDCS over left DLPFC (target intervention), compared to cognitive training plus sham (control intervention). The cognitive training encompasses a letter updating task and a three-stage Markov decision-making task. Forty-six participants with subjective cognitive decline (SCD) or mild cognitive impairment (MCI) will be randomized block-wise to either target or control intervention group and participate in nine interventional visits with additional pre- and post-intervention assessments. Performance in the letter updating task after training and anodal tDCS compared to sham stimulation will be analyzed as primary outcome. Further, performance on the second training task and transfer tasks will be investigated. Two follow-up visits (at 1 and 7 months post-training) will be performed to assess possible maintenance effects. Structural and functional magnetic resonance imaging (MRI) will be applied before the intervention and at the 7-month follow-up to identify possible neural predictors for successful intervention.

SIGNIFICANCE

With this trial, we aim to provide evidence for tDCS-induced improvements of multi-session cognitive training in participants with SCD and MCI. An improved understanding of tDCS effects on cognitive training performance and neural predictors may help to develop novel approaches to counteract cognitive decline in participants with prodromal AD.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT04265378 . Registered on 07 February 2020. Retrospectively registered. Protocol version: Based on BB 004/18 version 1.2 (May 17, 2019).

SPONSOR

University Medicine Greifswald.

A literature review on the neurophysiological underpinnings and cognitive effects of transcutaneous vagus nerve stimulation: challenges and future directions

Brain stimulation approaches are important to gain causal mechanistic insights into the relevance of functional brain regions and/or neurophysiological systems for human cognitive functions. In recent years, transcutaneous vagus nerve stimulation (tVNS) has attracted considerable popularity. It is a noninvasive brain stimulation technique based on the stimulation of the vagus nerve. The stimulation of this nerve activates subcortical nuclei, such as the locus coeruleus and the nucleus of the solitary tract, and from there, the activation propagates to the cortex. Since tVNS is a novel stimulation technique, this literature review outlines a brief historical background of tVNS, before detailing underlying neurophysiological mechanisms of action, stimulation parameters, cognitive effects of tVNS on healthy humans, and, lastly, current challenges and future directions of tVNS research in cognitive functions. Although more research is needed, we conclude that tVNS, by increasing norepineprine (NE) and gamma-aminobutyric acid (GABA) levels, affects NE- and GABA-related cognitive performance. The review provides detailed background information how to use tVNS as a neuromodulatory tool in cognitive neuroscience and outlines important future leads of research on tVNS.

Impact of 3-Day Combined Anodal Transcranial Direct Current Stimulation-Visuospatial Training on Object-Location Memory in Healthy Older Adults and Patients with Mild Cognitive Impairment

BACKGROUND

Associative object-location memory (OLM) is known to decline even in normal aging, and this process is accelerated in patients with mild cognitive impairment (MCI). Given the lack of curative treatment for Alzheimer's disease, activating cognitive resources during its preclinical phase might prevent progression to dementia.

OBJECTIVE

To evaluate the effects of anodal transcranial direct current stimulation (atDCS) combined with an associative episodic memory training on OLM in MCI patients and in healthy elderly (HE).

METHODS

In a single-blind cross-over design, 16 MCI patients and 32 HE underwent a 3-day visuospatial OLM training paired with either 20 min or 30 s (sham) atDCS (1 mA, right temporoparietal cortex). Effects on immediate (training success) and long-term memory (1-month) were investigated by conducting Mixed Model analyses. In addition, the impact of combined intervention on within-session (online) and on between-session (offline) performance were explored.

RESULTS

OLM training+atDCS enhanced training success only in MCI patients, but not HE (difference n.s.). Relative performance gain was similar in MCI patients compared to HE under atDCS. No beneficial effect was found after 1-month. Exploratory analyses suggested a positive impact on online, but a negative effect on offline performance in MCI patients. In both groups, exploratory post-hoc analyses indicated an association between initially low-performers and greater benefit from atDCS.

CONCLUSION

Cognitive training in MCI may be enhanced by atDCS, but further delineation of the impact of current brain state, as well as temporal characteristics of multi-session atDCS-training application, may be needed to induce longer-lasting effects.

Differential Age Effects of Transcranial Direct Current Stimulation on Associative Memory

OBJECTIVES

Older adults experience associative memory deficits relative to younger adults (Old & Naveh-Benjamin, 2008). The aim of this study was to test the effect of transcranial direct current stimulation (tDCS) on face-name associative memory in older and younger adults.

METHOD

Experimenters applied active (1.5 mA) or sham (0.1 mA) stimulation with the anode placed over the left dorsolateral prefrontal cortex (dlPFC) during a face-name encoding task, and measured both cued recall and recognition performance. Participants completed memory tests immediately after stimulation and after a 24-h delay to examine both immediate and delayed stimulation effects on memory.

RESULTS

Results showed improved face-name associative memory performance for both recall and recognition measures, but only for younger adults, whereas there was no difference between active and sham stimulation for older adults. For younger adults, stimulation-induced memory improvements persisted after a 24-h delay, suggesting delayed effects of tDCS after a consolidation period.

DISCUSSION

Although effective in younger adults, these results suggest that older adults may be resistant to this intervention, at least under the stimulation parameters used in the current study. This finding is inconsistent with a commonly seen trend, where tDCS effects on cognition are larger in older than younger adults.

Effects of a Multi-Session Cognitive Training Combined With Brain Stimulation (TrainStim-Cog) on Age-Associated Cognitive Decline - Study Protocol for a Randomized Controlled Phase IIb (Monocenter) Trial

Background

With increasing aging populations worldwide, developing interventions against age-associated cognitive decline is particularly important. Evidence suggests that combination of brain stimulation with cognitive training intervention may enhance training effects in terms of performance gain or transfer to untrained domains. This protocol describes a Phase IIb clinical trial that investigates the intervention effects of training combined with brain stimulation in older adults.

Methods

The TrainStim-Cog study is a monocentric, randomized, single-blind, placebo-controlled intervention. The study will investigate cognitive training with concurrent anodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (target intervention) compared to cognitive training with sham stimulation (control intervention) over nine sessions in 3 weeks, consisting of a letter updating task, and a three-stage Markov decision-making task. Fifty-six older adults will be recruited from the general population. Baseline assessment will be performed including neuropsychological screening and performance on training tasks. Participants will be allocated to one of the two study arms using block-wise randomization stratified by age and baseline performance with a 1:1 allocation ratio. Primary outcome is performance in the letter updating task after training under anodal tDCS compared to sham stimulation. Secondary outcomes include performance changes in the decision-making task and transfer tasks, as well as brain structure and functional networks assessed by structural, and functional magnetic resonance imaging (MRI) that are acquired pre- and post-intervention.

Significance

The main aim of the TrainStim-Cog study is to provide evidence for behavioral and neuronal effects of tDCS-accompanied cognitive training and to elucidate the underlying mechanisms in older adults. Our findings will contribute toward developing efficient interventions for age-associated cognitive decline.

Trial registration

This trial was retrospectively registered at Clinicaltrials.gov Identifier: NCT03838211 at February 12, 2019, https://clinicaltrials.gov/ct2/show/NCT03838211.

Protocol version

Based on BB 004/18 version 1.2 (May 17, 2019).

Reward motivation and neurostimulation interact to improve working memory performance in healthy older adults: A simultaneous tDCS-fNIRS study

Several studies have evaluated the effect of anodal transcranial direct current stimulation (tDCS) over the prefrontal cortex (PFC) for the enhancement of working memory (WM) performance in healthy older adults. However, the mixed results obtained so far suggest the need for concurrent brain imaging, in order to more directly examine tDCS effects. The present study adopted a continuous multimodal approach utilizing functional near-infrared spectroscopy (fNIRS) to examine the interactive effects of tDCS combined with manipulations of reward motivation. Twenty-one older adults (mean age = 69.7 years; SD = 5.05) performed an experimental visuo-spatial WM task before, during and after the delivery of 1.5 mA anodal tDCS/sham over the left prefrontal cortex (PFC). During stimulation, participants received performance-contingent reward for every fast and correct response during the WM task. In both sessions, hemodynamic activity of the bilateral frontal, motor and parietal areas was recorded across the entire duration of the WM task. Cognitive functions and reward sensitivity were also assessed with standard measures. Results demonstrated a significant impact of tDCS on both WM performance and hemodynamic activity. Specifically, faster responses in the WM task were observed both during and after anodal tDCS, while no differences were found under sham control conditions. However, these effects emerged only when taking into account individual visuo-spatial WM capacity. Additionally, during and after the anodal tDCS, increased hemodynamic activity relative to sham was observed in the bilateral PFC, while no effects of tDCS were detected in the motor and parietal areas. These results provide the first evidence of tDCS-dependent functional changes in PFC activity in healthy older adults during the execution of a WM task. Moreover, they highlight the utility of combining reward motivation with prefrontal anodal tDCS, as a potential strategy to improve WM efficiency in low performing healthy older adults.

Noisy galvanic vestibular stimulation modulates spatial memory in young healthy adults

Hippocampal and striatal circuits play important roles in spatial navigation. These regions integrate environmental information and receive intrinsic afferent inputs from the vestibular system. Past research indicates that galvanic vestibular stimulation (GVS) is a non-invasive technique that modulates hippocampal and striatal activities. There are also evidences for enhanced motor and cognitive functions through GVS. This study extends previous research to investigate whether noisy GVS may improve hippocampal- and striatal-associated aspects of spatial navigation performance. Using a virtual navigation task, we examined effects of noisy GVS on spatial learning and memory. To probe the participants’ sensitivity to hippocampal- or striatal-associated spatial information, we either enlarged the virtual environment’s boundary or replaced an intra-environmental location cue, respectively. Noisy GVS or sham stimulation was applied online during the learning phase in a within-subject crossover design. The results showed that noisy GVS enhanced spatial learning and the sensitivity foremost to hippocampal-dependent spatial information both in males and females. Individual differences in spatial working memory capacity moderated the effects of GVS, with individuals with lower capacity benefitting more from the stimulation. Furthermore, sex-related differences in GVS effects on the two forms of spatial representations may reflect differences between males and females in preferred spatial strategies.

Comparing Effects of Reward Anticipation on Working Memory in Younger and Older Adults

Goal-directed behavior requires sufficient resource allocation of cognitive control processes, such as the ability to prioritize relevant over less relevant information in working memory. Findings from neural recordings in animals and human multimodal imaging studies suggest that reward incentive mechanisms could facilitate the encoding and updating of context representations, which can have beneficial effects on working memory performance in young adults. In order to investigate whether these performance enhancing effects of reward on working memory processes are still preserved in old age, the current study aimed to investigate whether aging alters the effects of reward anticipation on the encoding and updating mechanisms in working memory processing. Therefore, a reward modulated verbal n-back task with age-adjusted memory load manipulation was developed to investigate reward modulation of working memory in younger (age 20-27) and older (age 65-78) adults. Our results suggest that the mechanism of reward anticipation in enhancing the encoding and updating of stimulus representations in working memory is still preserved in old age. EZ-diffusion modeling showed age distinct patterns of reward modulation of model parameters that correspond to different processes of memory-dependent decision making. Whereas processes of memory evidence accumulation and sensorimotor speed benefited from reward modulation, responses did not become more cautious with incentive motivation for older adults as it was observed in younger adults. Furthermore, individual differences in reward-related enhancement of decision speed correlated with cognitive processing fluctuation and memory storage capacity in younger adults, but no such relations were observed in older adults. These findings indicate that although beneficial effects of reward modulation on working memory can still be observed in old age, not all performance aspects are facilitated. Whereas reward facilitation of content representations in working memory seems to be relatively preserved, aging seems to affect the updating of reward contexts. Future research is needed to elucidate potential mechanisms for motivational regulation of the plasticity of working memory in old age.

Functional connectivity in cognitive control networks mitigates the impact of white matter lesions in the elderly

BACKGROUND

Cerebrovascular pathology, quantified by white matter lesions (WML), is known to affect cognition in aging, and is associated with an increased risk of dementia. The present study aimed to investigate whether higher functional connectivity in cognitive control networks mitigates the detrimental effect of WML on cognition.

METHODS

Nondemented older participants (≥ 50 years; n = 230) underwent cognitive evaluation, fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI), and resting state functional magnetic resonance imaging (fMRI). Total WML volumes were quantified algorithmically. Functional connectivity was assessed in preselected higher-order resting state networks, namely the fronto-parietal, the salience, and the default mode network, using global and local measures. Latent moderated structural equations modeling examined direct and interactive relationships between WML volumes, functional connectivity, and cognition.

RESULTS

Larger WML volumes were associated with worse cognition, having a greater impact on executive functions (β = -0.37, p < 0.01) than on memory (β = -0.22, p < 0.01). Higher global functional connectivity in the fronto-parietal network and higher local connectivity between the salience network and medial frontal cortex significantly mitigated the impact of WML on executive functions, (unstandardized coefficients: b = 2.39, p = 0.01; b = 3.92, p = 0.01) but not on memory (b = -5.01, p = 0.51, b = 2.01, p = 0.07, respectively). No such effects were detected for the default mode network.

CONCLUSION

Higher functional connectivity in fronto-parietal and salience networks may protect against detrimental effects of WML on executive functions, the cognitive domain that was predominantly affected by cerebrovascular pathology. These results highlight the crucial role of cognitive control networks as a neural substrate of cognitive reserve in older individuals.

No Effects of Non-invasive Brain Stimulation on Multiple Sessions of Object-Location-Memory Training in Healthy Older Adults

Object-location memory (OLM) is known to decline with normal aging, a process accelerated in pathological conditions like mild cognitive impairment (MCI). In order to maintain cognitive health and to delay the transition from healthy to pathological conditions, novel strategies are being explored. Tentative evidence suggests that combining cognitive training and anodal transcranial direct current stimulation (atDCS), both reported to induce small and often inconsistent behavioral improvements, could generate larger or more consistent improvements or both, compared to each intervention alone. Here, we explored the combined efficacy of these techniques on OLM. In a subject-blind sham-controlled cross-over design 32 healthy older adults underwent a 3-day visuospatial training paired with either anodal (20 min) or sham (30 s) atDCS (1 mA, temporoparietal). Subjects were asked to learn the correct object-location pairings on a street map, shown over five learning blocks on each training day. Acquisition performance was assessed by accuracy on a given learning block in terms of percentage of correct responses. Training success (performance on last training day) and delayed memory after 1-month were analyzed by mixed model analysis and were controlled for gender, age, education, sequence of stimulation and baseline performance. Exploratory analysis of atDCS effects on within-session (online) and between-session (offline) memory performance were conducted. Moreover, transfer effects on similar trained (visuospatial) and less similar (visuo-constructive, verbal) untrained memory tasks were explored, both immediately after training, and on follow-up. We found that atDCS paired with OLM-training did not enhance success in training or performance in 1-month delayed memory or transfer tasks. In sum, this study did not support the notion that the combined atDCS-training approach improves immediate or delayed OLM in older adults. However, specifics of the experimental design, and a non-optimal timing of atDCS between sessions might have masked beneficial effects and should be more systematically addressed in future studies.

Neuronal and behavioral effects of multi-day brain stimulation and memory training

Strategies for memory enhancement, especially for the older population, are of great scientific and public interest. Here, we aimed at investigating neuronal and behavioral effects of transcranial direct current stimulation (tDCS) paired with memory training. Young and older adults were trained on an object-location-memory task on 3 consecutive days with either anodal or sham tDCS. Recall performance was assessed immediately after training, 1 day and 1 month later, as well as performance on trained function and transfer task. Resting-state functional magnetic resonance imaging was conducted at baseline and at 1-day follow-up to analyze functional coupling in the default mode network. Anodal tDCS led to superior recall performance after training, an associated increase in default mode network strength and enhanced trained function and transfer after 1 month. Our findings suggest that tDCS-accompanied multi-day training improves performance on trained material, is associated with beneficial memory network alterations, and transfers to other memory tasks. Our study provides insight into tDCS-induced behavioral and neuronal alterations and will help to develop interventions against age-related cognitive decline.

Potential link between genetic polymorphisms of catechol-O-methyltransferase and dopamine receptors and treatment efficacy of risperidone on schizophrenia

OBJECTIVE

The current study aimed to explore the association of single nucleotide polymorphisms (SNPs) within catechol-O-methyltransferase (COMT) and dopamine receptors with schizophrenia and genetic association with risperidone treatment response.

METHODS

A total of 690 schizophrenic patients (case group) were selected and 430 healthy people were included as the controls. All patients received risperidone treatment continuously for 8 weeks. Next, peripheral venous blood samples were collected and were subjected to polymerase chain reaction-restriction fragment length polymorphism to amplify and genotype the SNPs within COMT and dopamine receptors. Then, correlation analysis was conducted between Positive and Negative Syndrome Scale improvement rates and SNPs within COMT and the dopamine receptor gene.

RESULTS

The allele of DRD1 rs11749676 (A) emerged as a key element in reducing schizophrenia risk with statistical significance (P<0.001). Remarkably, alleles of COMT rs165774 (G), DRD2 rs6277 (T), and DRD3 rs6280 (C) were associated with raised predisposition to schizophrenia (all P<0.001). Regarding DRD1 rs11746641, DRD1 rs11749676, DRD2 rs6277, and DRD3 rs6280, the case group exhibited a lesser frequency of heterozygotes in comparison with wild homozygotes genotype (all P<0.001). SNPs (COMT rs4680, DRD2 rs6275, DRD2 rs1801028, and DRD2 rs6277) were remarkably associated with improvement rates of PANSS total scores (P<0.05). SNPs (COMT rs165599 and DRD2 rs1801028) were significantly associated with risperidone efficacy on negative symptoms (P<0.05).

CONCLUSION

COMT SNPs and dopamine receptor SNPs were correlated with prevalence of schizophrenia and risperidone treatment efficacy of schizophrenia.