Training-related brain plasticity in subjects at risk of developing Alzheimer's disease

Long-term cognitive training enhances fluid cognition and brain connectivity in individuals with MCI

Amnestic mild cognitive impairment (aMCI) is a risk factor for Alzheimer's disease (AD). Multi-domain cognitive training (CT) may slow cognitive decline and delay AD onset. However, most work involves short interventions, targeting single cognitive domains or lacking active controls. We conducted a single-blind randomized controlled trial to investigate the effect of a 6-month, multi-domain CT on Fluid Cognition, functional connectivity in memory and executive functioning networks (primary outcomes), and white matter microstructural properties (secondary outcome) in aMCI. Sixty participants were randomly assigned to either a multi-domain CT or crossword training (CW) group, and thirty-four participants completed the intervention. We found a significant group-by-time interaction in Fluid Cognition (p = 0.007, F (1,28) = 8.26, Cohen's d = 0.38, 95% confidence interval [CI]: 2.45-14.4), with 90% of CT patients showing post-intervention improvements (p < 0.01, Cohen's d = 0.7). The CT group also showed better post-intervention Fluid Cognition than healthy controls (HCs, N = 45, p = 0.045). Functional connectivity analyses showed a significant group-by-time interaction (Cohen's d ≥ 0.8) in the dorsolateral prefrontal cortex (DLPFC) and inferior parietal cortex (IPC) networks. Specifically, CT displayed post-intervention increases whereas CW displayed decreases in functional connectivity. Moreover, increased connectivity strength between the left DLPFC and medial PFC was associated with improved Fluid Cognition. At a microstructural level, we observed a decline in fiber density (FD) for both groups, but the CT group declined less steeply (1.3 vs. 2%). The slower decline in FD for the CT group in several tracts, including the cingulum-hippocampus tract, was associated with better working memory. Finally, we identified regions in cognitive control and memory networks for which baseline functional connectivity and microstructural properties were associated with changes in Fluid Cognition. Long-term, multi-domain CT improves cognitive functioning and functional connectivity and delays structural brain decline in aMCI (ClinicalTrials.gov number: NCT03883308).

Enhancing creative divergent thinking in older adults with a semantic retrieval strategy

Creative divergent thinking involves the generation of unique ideas by pulling from semantic memory stores and exercising cognitive flexibility to shape these memories into something new. Although cognitive abilities decline with age, semantic memory tends to remain intact. This study aims to utilize that memory to investigate the effectiveness of a brief cognitive training to improve creative divergent thinking. Older adults were trained using a semantic retrieval strategy to improve creativity in the Alternate Uses Task (AUT) and the Divergent Association Task (DAT). Participants were tested on the AUT and DAT across three time points: before the strategy was introduced (T0 and T1) and afterward (T2). Results showed that the strategy enhances idea novelty in the AUT; additionally, participants that initially scored lowest on the AUT showed the greatest increase in AUT performance. This finding suggests that older adults can use a semantic retrieval strategy to enhance creative divergent thinking.

Exergaming for dementia and mild cognitive impairment

BACKGROUND

Dementia and mild cognitive impairment are significant contributors to disability and dependency in older adults. Current treatments for managing these conditions are limited. Exergaming, a novel technology-driven intervention combining physical exercise with cognitive tasks, is a potential therapeutic approach.

OBJECTIVES

To assess the effects of exergaming interventions on physical and cognitive outcomes, and activities of daily living, in people with dementia and mild cognitive impairment.

SEARCH METHODS

On 22 December 2023, we searched the Cochrane Dementia and Cognitive Improvement Group's register, MEDLINE (Ovid SP), Embase (Ovid SP), PsycINFO (Ovid SP), CINAHL (EBSCOhost), Web of Science Core Collection (Clarivate), LILACS (BIREME), ClinicalTrials.gov, and the WHO (World Health Organization) meta-register the International Clinical Trials Registry Portal.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that recruited individuals diagnosed with dementia or mild cognitive impairment (MCI). Exergaming interventions involved participants being engaged in physical activity of at least moderate intensity, and used immersive and non-immersive virtual reality (VR) technology and real-time interaction. We planned to classify comparators as inactive control group (e.g. no treatment, waiting list), active control group (e.g. standard treatment, non-specific active control), or alternative treatment (e.g. physical activity, computerised cognitive training). Outcomes were to be measured using validated instruments.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion, extracted data, assessed the risk of bias using the Cochrane risk of bias tool RoB 2, and assessed the certainty of the evidence using GRADE. We consulted a third author if required. Where possible, we pooled outcome data using a fixed-effect or random-effects model. We expressed treatment effects as standardised mean differences (SMDs) for continuous outcomes and as risk ratios (RRs) for dichotomous outcomes, along with 95% confidence intervals (CIs). When data could not be pooled, we presented a narrative synthesis.

MAIN RESULTS

We included 11 studies published between 2014 and 2023. Six of these studies were pre-registered. Seven studies involved 308 participants with mild cognitive impairment, and five studies included 228 individuals with dementia. One of the studies presented data for both MCI and dementia separately. Most comparisons exhibited a high risk or some concerns of bias. We have only low or very low certainty about all the results presented below. Effects of exergaming interventions for people with dementia Compared to a control group Exergaming may improve global cognitive functioning at the end of treatment, but the evidence is very uncertain (SMD 1.47, 95% 1.04 to 1.90; 2 studies, 113 participants). The evidence is very uncertain about the effects of exergaming at the end of treatment on global physical functioning (SMD -0.20, 95% -0.57 to 0.17; 2 studies, 113 participants) or activities of daily living (ADL) (SMD -0.28, 95% -0.65 to 0.09; 2 studies, 113 participants). The evidence is very uncertain about adverse effects due to the small sample size and no events. Findings are based on two studies (113 participants), but data could not be pooled; both studies reported no adverse reactions linked to the intervention or control group. Compared to an alternative treatment group At the end of treatment, the evidence is very uncertain about the effects of exergaming on global physical functioning (SMD 0.14, 95% -0.30 to 0.58; 2 studies, 85 participants) or global cognitive functioning (SMD 0.11, 95% -0.33 to 0.55; 2 studies, 85 participants). For ADL, only one study was available (n = 67), which provided low-certainty evidence of little to no difference between exergaming and exercise. The evidence is very uncertain about adverse effects of exergaming compared with alternative treatment (RR 7.50, 95% CI 0.41 to 136.52; 2 studies, 2/85 participants). Effects of exergaming interventions for people with mild cognitive impairment (MCI) Compared to a control group Exergaming may improve global cognitive functioning at the end of treatment for people with MCI, but the evidence is very uncertain, (SMD 0.79, 95% 0.05 to 1.53; 2 studies, 34 participants). The evidence is very uncertain about the effects of exergaming at the end of treatment on global physical functioning (SMD 0.27, 95% -0.41 to 0.94; 2 studies, 34 participants) and ADL (SMD 0.51, 95% -0.01 to 1.03; 2 studies, 60 participants). The evidence is very uncertain about the effects of exergaming on adverse effects due to a small sample size and no events (0/14 participants). Findings are based on one study. Compared to an alternative treatment group The evidence is very uncertain about global physical functioning at the end of treatment. Only one study was included (n = 45). For global cognitive functioning, we included four studies (n = 235 participants), but due to considerable heterogeneity (I² = 96%), we could not pool results. The evidence is very uncertain about the effects of exergaming on global cognitive functioning. No study evaluated ADL outcomes. The evidence is very uncertain about adverse effects of exergaming due to the small sample size and no events (n = 123 participants). Findings are based on one study.

AUTHORS' CONCLUSIONS

Overall, the evidence is very uncertain about the effects of exergaming on global physical and cognitive functioning, and ADL. There may be an improvement in global cognitive functioning at the end of treatment for both people with dementia and people with MCI, but the evidence is very uncertain. The potential benefit is observed only when exergaming is compared with a control intervention (e.g. usual care, listening to music, health education), and not when compared with an alternative treatment with a specific effect, such as physical activity (e.g. standing and sitting exercises or cycling). The evidence is very uncertain about the effects of exergaming on adverse effects. All sessions took place in a controlled and supervised environment. Therefore, we do not know if exergaming can be safely used in a home environment, unsupervised.

Five-year effects of cognitive training in individuals with mild cognitive impairment

INTRODUCTION

In a 5-year follow-up study, we investigated the enduring effects of cognitive training on older adults with mild cognitive impairment (MCI).

METHODS

A randomized controlled single-blind trial involved 145 older adults with MCI, assigned to cognitive training (MEMO+), an active control psychosocial intervention, or a no-contact condition. Five-year effects were measured on immediate and delayed memory recall, the Montreal Cognitive Assessment screening test (MoCA), self-reported strategy use, and daily living difficulties.

RESULTS

At follow-up, participants who received cognitive training showed a smaller decline in delayed memory and maintained MoCA scores, contrasting with greater declines in the control groups. Cognitive training participants outperformed controls in both delayed memory and MoCA scores at the 5-year time point. No significant group differences were observed in self-reported strategy use or difficulties in daily living.

DISCUSSION

Cognitive training provides long-term benefits by mitigating memory decline and slowing clinical symptom progression in older adults with MCI.

Highlights

Cognitive training reduced the 5-year memory decline of persons with MCI.Cognitive training also reduced decline on the Montreal Cognitive Assessment (MoCA).No intervention effect was found on strategy use or activities of daily living.

Effects of a Virtual Reality Reaction Training Protocol on Physical and Cognitive Skills of Young Adults and Their Neural Correlates: A Randomized Controlled Trial Study

Increasing evidence shows that virtual reality (VR) training is highly effective in cognitive and motor rehabilitation. Another modern form of training is cognitive-motor dual-task training (CMDT), which has been demonstrated to rapidly improve physical and cognitive functions in real environments. This study aims to test whether a VR-based CMDT protocol can be used for motor and cognitive skill enhancement in young, healthy subjects. For this aim, 24 university students participated in a randomized control trial. The experimental group participated in a 5-week virtual reality reaction training (VRRT), performing 30 min sessions once a week. The control group did not receive any training but was tested twice with the same measures and temporal distance as the experimental group. Before and after the intervention, motor, cognitive, and electrophysiological measures were assessed. The results showed that following VRRT, the response time for both physical and cognitive tests was improved by about 14% and 12%, respectively, while the control group did not show significant changes. Moreover, electrophysiological data revealed a significant increase in anticipatory motor readiness in premotor brain areas in the experimental group only; however, cognitive top-down control tended to be increased in prefrontal areas after VRRT. This training protocol in a VR modality seems to be as effective as other CMDT methodologies carried out in a real modality. Still, it has the advantages of being more flexible and more user-friendly compared to standard training. The VRRT's efficacy on physical and cognitive functions indicates that virtual reality applications can be used by the young population, not only for entertainment purposes but also in the form of cognitive-motor training.

Effects of computerized cognitive training on biomarker responses in older adults with mild cognitive impairment: A scoping review

Background and Aims

Mild cognitive impairment (MCI) is a widespread condition in older individuals, posing significant risk of dementia. However, limited research has been conducted to explore effective interventions and clarify their impact at the neural level. Therefore, this study aimed to investigate the effects of computerized cognitive training (CCT) and explore the associated neural mechanisms in preventing dementia in older individuals with MCI, with a view to inform future intervention efforts.

Methods

We reviewed the effects of CCT on biomarker outcomes in older adults with MCI. The search was conducted for studies published between 2010 and May 10, 2023, using three search engines: PubMed, Scopus, and Cumulative Index to Nursing and Allied Health Literature. The inclusion criteria were as follows: studies that involved participants diagnosed with MCI, included CCT, included quantitative assessment of biomarker results, and conducted randomized controlled trials.

Results

Sixteen studies that used biomarkers, including magnetic resonance imaging, electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and blood or salivary biomarkers, were extracted. The results showed that CCT caused changes in structure and function within the main brain network, including the default mode network, and decreased both theta rhythm activity on EEG and prefrontal activity on fNIRS, with improvement in cognitive function. Furthermore, CCT combined with physical exercise showed more significant structural and functional changes in extensive brain regions compared with CCT alone. Virtual reality-based cognitive training improved not only executive function but also instrumental activities of daily living.

Conclusion

CCT causes functional and structural changes in extensive brain regions and improves cognitive function in older adults with MCI. Our findings highlight the potential of individualized intervention methods and biomarker assessment according to the specific causes of MCI. Future research should aim to optimize these personalized therapeutic strategies to maximize the benefits of CCT in older adults with MCI.

Altered whole-brain functional network in patients with frontal low-grade gliomas: a resting-state functional MRI study

PURPOSE

Gliomas are the most common primary brain tumor. Currently, topological alterations of whole-brain functional network caused by gliomas are not fully understood. The work here clarified the topological reorganization of the functional network in patients with unilateral frontal low-grade gliomas (LGGs).

METHODS

A total of 45 patients with left frontal LGGs, 19 with right frontal LGGs, and 25 healthy controls (HCs) were enrolled. All the resting-state functional MRI (rs-fMRI) images of the subjects were preprocessed to construct the functional network matrix, which was used for graph theoretical analysis. A two-sample t-test was conducted to clarify the differences in global and nodal network metrics between patients and HCs. A network-based statistic approach was used to identify the altered specific pairs of regions in which functional connectivity in patients with LGGs.

RESULTS

The local efficiency, clustering coefficient, characteristic path length, and normalized characteristic path length of patients with unilateral frontal LGGs were significantly lower than HCs, while there were no significant differences of global efficiency and small-worldness between patients and HCs. Compared with the HCs, betweenness centrality, degree centrality, and nodal efficiency of several brain nodes were changed significantly in patients. Around the tumor and its adjacent areas, the inter- and intra-hemispheric connections were significantly decreased in patients with left frontal LGGs.

CONCLUSION

The patients with unilateral frontal LGGs have altered global and nodal network metrics and decreased inter- and intra-hemispheric connectivity. These topological alterations may be involved in functional impairment and compensation of patients.

The Effectiveness of Cognitive-Focused Interventions for Adults With Diabetes: A Systematic Review

BACKGROUND

Adults with diabetes and impaired memory and executive functions are more likely to experience difficulties in diabetes self-management and achieving glycemic targets. The purpose of this systematic review was to evaluate the evidence of the effects of cognitive-focused interventions on cognitive ability, diabetes self-management, and management of glycemic levels for middle-aged adults and older adults with diabetes.

METHODS

A systematic review of randomized controlled/clinical trials published in English between 2012 and 2022 was conducted. A search was performed using 5 databases (PubMed, CINAHL, Embase, Web of Science, and Scopus) in addition to hand-searching. The search terms included diabetes, adults, cognitive-focused intervention, cognition, self-management, and hemoglobin A1C (HbA1C).

RESULTS

Eleven studies met the inclusion criteria. Cognitive ability and diabetes self-management were assessed using different measurements, and glycemic levels were measured with HbA1C. Nine studies applied cognitive training, one provided working memory training, and one used occupational therapy. Eight studies combined cognitive training with a co-intervention, including self-efficacy, lifestyle management, physical training, chronic disease self-management program, square-stepping exercise, psychoeducational intervention, and empowerment. Eight studies showed statistically significant improvements in at least one cognitive domain.

CONCLUSIONS

Cognitive-focused interventions have a positive effect on improving memory and executive function. However, the evidence of cognitive-focused interventions on diabetes self-management and glycemic levels has not been established. Future studies to improve cognition using effective strategies to improve cognitive function enhancing diabetes self-management behaviors and managing glycemic levels are warranted.

Efficacy analysis of three brain stimulation techniques for Alzheimer's disease: a meta-analysis of repeated transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation

INTRODUCTION

This systematic review and meta-analysis study investigates the efficacy of repeated transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS) using neuropsychological assessments as a potential treatment option for Alzheimer's disease (AD).

METHODS

PubMed, Embase, and the Cochrane Library were searched for studies on rTMS, tDCS, and DBS for the treatment of patients with AD between April 1970 and October 2022. The mini-Mental State Examination (MMSE) and AD Assessment Scale - Cognitive Subscale (ADAS-Cog) were adopted as the efficacy index.

RESULTS

The analysis yielded 17 eligible studies. rTMS greatly improved the cognition of patients with AD (immediate post-treatment WMD of MMSE score: 2.06, p < 0.00001; short-term follow-up WMD of MMSE score: 2.12, p = 0.006; WMD of ADAS-Cog score in single-arm studies: -4.97, p = 0.001). DBS did not reverse the progression of cognitive decline (WMD of ADAS-Cog score in single-arm studies: 7.40, p < 0.00001). Furthermore, tDCS demonstrated no significant efficacy in improving cognition in random clinical trials or single-arm studies.

CONCLUSION

rTMS is a promising non-medicinal alternative for cognitive improvement inpatients with AD.

Virtual reality applications based on instrumental activities of daily living (iADLs) for cognitive intervention in older adults: a systematic review

BACKGROUND

In recent years, the use of virtual reality (VR) as a complementary intervention in treating cognitive impairment has significantly increased. VR applications based on instrumental activities of daily living (iADL-VR) could offer a promising approach with greater ecological validity for intervention in groups with cognitive impairments. However, the effectiveness of this approach is still debated.

OBJECTIVE

This systematic review aims to synthesize the effects of iADL-VR interventions to rehabilitate, train, or stimulate cognitive functions in healthy adults and people with mild cognitive impairment (MCI) and different types of dementia.

METHODS

A systematic search was performed in the Scopus, PubMed, IEEE Xplore, Web of Science, and APA PsycNet databases until September 2022 and repeated in April 2023. The selected studies met the search terms, were peer-reviewed, included an iADL-VR intervention, and were written in English. Descriptive, qualitative studies, reviews, cognitive assessment, non-intervention studies, those unrelated to VR or iADL, those focused on motor aspects, and non-degenerative disorders were excluded. The PEDro scale was used to assess the methodological quality of the controlled studies. To present and synthesize the results, we organized the extracted data into three tables, including PEDro scores, participant characteristics, and study characteristics.

RESULTS

Nineteen studies that met the inclusion and exclusion criteria were included. The total sample reached 590 participants, mostly women (72.67%). Approximately 30% were diagnosed with Alzheimer's disease or dementia, and 20% had mild cognitive impairment. Variables such as authors and year of publication, study design, type of intervention and VR applied, duration of the intervention, main findings, and conclusions were extracted. Regarding demographic characteristics, the sample size, age, sex, years of education, neurological diagnosis, dropouts, and the city and country where the intervention took place were recorded. Almost all studies showed improvements in some or all the outcomes after the intervention, generally greater in the iADL-VR group than in the control group.

CONCLUSION

iADL-VR interventions could be beneficial in improving the performance of cognitive functions in older adults and people with MCI and different types of dementia. The ecological component of these tasks makes them very suitable for transferring what has been learned to the real world. However, such transfer needs to be confirmed by further studies with larger and more homogeneous samples and longer follow-up periods. This review had no primary funding source and was registered with PROSPERO under registration ID: 375166.

Diagnostic Efficacy and Clinical Relevance of Artificial Intelligence in Detecting Cognitive Decline

Cognitive impairment is an age-associated disorder of increasing prevalence as the aging population continues to grow. Classified based on the level of cognitive decline, memory, function, and capacity to conduct activities of daily living, cognitive impairment ranges from mild cognitive impairment to dementia. When considering the insidious nature of the etiologies responsible for varying degrees of cognitive impairment, early diagnosis may provide a clinical benefit through the facilitation of early treatment. Typical diagnosis relies heavily on evaluation in a primary care setting. However, there is evidence that other diagnostic tools may aid in an earlier diagnosis of the different underlying pathologies responsible for cognitive impairment. Artificial intelligence represents a new intersecting field with healthcare that may aid in the early detection of neurodegenerative disorders. When assessing the role of AI in detecting cognitive decline, it is important to consider both the diagnostic efficacy of AI algorithms and the clinical relevance and impact of early interventions as a result of early detection. Thus, this review highlights promising investigations and developments in the space of artificial intelligence and healthcare and their potential to impact patient outcomes.

Prefrontal Cortex Activation during Memory Training by Virtual Drum Beating: A Randomized Controlled Trial

The use of virtual reality (VR) content in neurological disorders with cognitive impairment is increasing. We have developed a device that incorporates virtual drum beating content, designed for digit memorization training. This study aimed to investigate the effects of realistic cognitive training on brain activity using functional near-infrared spectroscopy (fNIRS). Thirty healthy individuals were recruited and randomly assigned into two groups: conventional cognitive exercise (CCE) and a realistic cognitive exergame (RCE). Subjects in the CCE group underwent memory training by memorizing numbers displayed on a computer screen and then writing them on paper. The main outcome measure was the oxyhemoglobin level in the dorsolateral prefrontal cortex (DLPFC). As a result, the average number of digits was 7.86 ± 0.63 for the CCE and 7.6 ± 0.82 for the RCE. The mean difference in ΔHbO was 1.417 ± 0.616 μm (p = 0.029) in channel 2, located in the right DLPFC. Channel 7 and channel 10, which measured activations in the hypothesized medial orbitofrontal cortex (OFC), also showed a significant mean difference of ΔHbO. DLPFC and OFC presented higher activation in the RCE group (p < 0.05), attributable to the simultaneous memory training and virtual drum beating, which provided various sensory inputs (visual, auditory, and vibration). Although DLPFC involvement in cognitive processes remains controversial, our findings suggest that realistic memory training using drumming content can lead to safer activation of the DLPFC compared to conventional cognitive training.

Sensory processing sensitivity, memory and cognitive training with neurofeedback

Sensory processing sensitivity (SPS) is a biological trait associated with enhanced awareness of and responsivity to the environment, as well as depth of cognitive processing. However, only a few studies have investigated how contextual factors impact cognition as a function of SPS. Thus, this study examined whether SPS is associated with differential changes in cognitive function resulting from participation in a 4-week app-based cognitive training program with neurofeedback (CT-NF). Participants (M age = 66 years) were randomized to either a treatment (CT-NF) or control group (Tetris). They completed a self-report measure of SPS (the Highly Sensitive Person Scale), and cognitive tests at pre- and post-intervention. Results revealed that individuals with higher levels of SPS in the treatment group showed superior improvements in memory (MEM) and visual memory (VSM), relative to other participants and other measures of cognition. These findings are consistent with theories of SPS and studies showing that enhanced visual perceptiveness and memory are associated with the trait. Moreover, they highlight the cognitive mechanisms that might be especially important for SPS. In conclusion, these findings suggest that those with high SPS may experience enhancements in MEM and VSM, resulting from a 4-week app-based CT-NF program.

Neurotoxicity and Outcomes from Developmental Lead Exposure: Persistent or Permanent?

BACKGROUND

Childhood lead poisoning remains an important public health issue in the United States, as well as elsewhere in the world. Although primary prevention is a major goal and it is critically important to keep children from getting poisoned, it is also important to explore ways to reduce the neurotoxic effects of lead in those children already poisoned. Whether lead-induced neurotoxicity and its related adverse outcomes are viewed as "permanent" or "persistent" may influence the way in which potential remediation efforts are considered for improving outcomes from childhood lead poisoning.

OBJECTIVES

The objective of this commentary was to discuss the ideas of permanence and persistence in relation to the direct neurotoxic effects of lead on the brain and the resulting adverse outcomes from these effects. Recent new insights regarding potential mitigation of lead-induced neurotoxic effects on brain and behavior are considered along with clinical information on neurorehabilitation to suggest potential strategies for improving cognitive/behavioral outcomes in lead-poisoned children.

DISCUSSION

The distinction between permanent and persistent in regard to lead-induced neurotoxicity and its resulting outcomes may have broad implications for public health policies in response to the problem of childhood lead exposure. The term permanent implies that the damage is irreversible with little chance of improvement. However, there is evidence that at least some of the adverse cognitive/behavioral outcomes from lead exposure are persistent rather than permanent and potentially amenable, under the appropriate circumstances, to some level of mitigation. This author recommends that clinical, interventional research efforts be devoted to exploring optimal neurorehabilitative and enrichment conditions to stimulate plasticity and enhance functioning to determine the extent to which promising results from preclinical studies of lead-induced brain damage and the mitigation of these effects can be successfully translated to humans. https://doi.org/10.1289/EHP12371.

Compensatory Mechanisms in Early Alzheimer's Disease and Clinical Setting: The Need for Novel Neuropsychological Strategies

Despite advances in the detection of biomarkers and in the design of drugs that can slow the progression of Alzheimer's disease (AD), the underlying primary mechanisms have not been elucidated. The diagnosis of AD has notably improved with the development of neuroimaging techniques and cerebrospinal fluid biomarkers which have provided new information not available in the past. Although the diagnosis has advanced, there is a consensus among experts that, when making the diagnosis in a specific patient, many years have probably passed since the onset of the underlying processes, and it is very likely that the biomarkers in use and their cutoffs do not reflect the true critical points for establishing the precise stage of the ongoing disease. In this context, frequent disparities between current biomarkers and cognitive and functional performance in clinical practice constitute a major drawback in translational neurology. To our knowledge, the In-Out-test is the only neuropsychological test developed with the idea that compensatory brain mechanisms exist in the early stages of AD, and whose positive effects on conventional tests performance can be reduced in assessing episodic memory in the context of a dual-task, through which the executive auxiliary networks are 'distracted', thus uncover the real memory deficit. Furthermore, as additional traits, age and formal education have no impact on the performance of the In-Out-test.

Deciphering the clinico-radiological heterogeneity of dysexecutive Alzheimer's disease

Dysexecutive Alzheimer's disease (dAD) manifests as a progressive dysexecutive syndrome without prominent behavioral features, and previous studies suggest clinico-radiological heterogeneity within this syndrome. We uncovered this heterogeneity using unsupervised machine learning in 52 dAD patients with multimodal imaging and cognitive data. A spectral decomposition of covariance between FDG-PET images yielded six latent factors ("eigenbrains") accounting for 48% of variance in patterns of hypometabolism. These eigenbrains differentially related to age at onset, clinical severity, and cognitive performance. A hierarchical clustering on the eigenvalues of these eigenbrains yielded four dAD subtypes, i.e. "left-dominant," "right-dominant," "bi-parietal-dominant," and "heteromodal-diffuse." Patterns of FDG-PET hypometabolism overlapped with those of tau-PET distribution and MRI neurodegeneration for each subtype, whereas patterns of amyloid deposition were similar across subtypes. Subtypes differed in age at onset and clinical severity where the heteromodal-diffuse exhibited a worse clinical picture, and the bi-parietal had a milder clinical presentation. We propose a conceptual framework of executive components based on the clinico-radiological associations observed in dAD. We demonstrate that patients with dAD, despite sharing core clinical features, are diagnosed with variability in their clinical and neuroimaging profiles. Our findings support the use of data-driven approaches to delineate brain-behavior relationships relevant to clinical practice and disease physiology.

Effectiveness of a Computerized Home-Based Cognitive Stimulation Program for Treating Cancer-Related Cognitive Impairment

Cancer patients assert that after chemotherapy their cognitive abilities have deteriorated. Cognitive stimulation is the clinical treatment of choice for reversing cognitive decline. The current study describes a computerized home-based cognitive stimulation program in patients who survived breast cancer. It aims to assess safety and effectiveness of cognitive stimulation in the oncology population. A series of 45-min training sessions was completed by the participants. A thorough assessment was performed both before and after the intervention. The mini-Mental Adjustment to Cancer Scale, the Cognitive Assessment for Chemo Fog Research, and the Functionality Assessment Instrument in Cancer Treatment-Cognitive Function served as the main assessment tools. The State-Trait Anxiety Inventory, Beck Depression Inventory, Brief Fatigue Inventory, and Measuring Quality of Life-The World Health Organization data were gathered as secondary outcomes. Home-based cognitive stimulation demonstrated beneficial effects in the oncology population, with no side effects being reported. Cognitive, physical, and emotional improvements were observed, along with decreased interference in daily life activities and a better overall quality of life.

Toward rational use of cognitive training in those with mild cognitive impairment

The term cognitive training includes a range of techniques that hold potential for treating cognitive impairment caused by neurologic injury and disease. Our central premise is that these techniques differ in their mechanisms of action and therefore engage distinct brain regions (or neural networks). We support this premise using data from a single-blind randomized-controlled trial in which patients with mild cognitive impairment were randomized to either mnemonic strategy training (MST) or spaced retrieval training (SRT) as they learned ecologically relevant object-location associations. Both training approaches were highly effective in the short term, but MST demonstrated a clear advantage after days to weeks. MST also increased activation in and functional connectivity between frontal, temporal, and parietal regions as well as the hippocampus. In contrast, patterns of reduced activation and functional connectivity were evident following SRT. These findings support the rational development of cognitive training techniques.

Contralesional macrostructural plasticity in patients with frontal low-grade glioma: a voxel-based morphometry study

PURPOSE

Neuroplasticity can partially compensate for the neurological deficits caused by brain tumors. However, the structural plasticity of the brain caused by brain tumors is not fully understood. This study aimed to assess the structural plasticity of the contralesional hemisphere in patients with frontal low-grade gliomas (LGGs).

METHODS

A total of 25 patients with left frontal LGGs (LFLGGs), 19 patients with right frontal LGGs (RFLGGs), and 25 healthy controls (HCs) were enrolled in this study. High-resolution structural T1-weighted imaging and fluid attenuation inversion recovery were performed on all participants. Voxel-based morphometry (VBM) analysis was used to detect differences in the brain structural plasticity between patients with unilateral LGGs and HCs.

RESULTS

VBM analysis revealed that compared with HCs, the gray matter volume (GMV) of the contralesional putamen and amygdala was significantly smaller and larger in the patients with RFLGGs and LFLGGs, respectively, while the GMVs of the contralesional cuneus and superior temporal gyrus (STG) were significantly larger in the patients with LFLGGs. The surviving clusters of the right hemisphere included 1357 voxels in the amygdala, 1680 voxels in the cuneus, 384 voxels in the STG, and 410 voxels in the putamen. The surviving clusters of the left hemisphere were 522 voxels in the amygdala and 320 voxels in the putamen.

CONCLUSION

The unilateral frontal LGGs are accompanied by structural plasticity in the contralesional cortex and vary with tumor laterality. Contralesional structural reorganization may be one of the physiological basis for functional reorganization or compensation in the frontal LGGs.

Cognitive Training Effect and Imaging Evidence

Cognitive intervention is a specific form of non-pharmacological intervention used to combat cognitive dysfunction. In this chapter, behavioral and neuroimaging studies about cognitive interventions are introduced. Regarding intervention studies, the form of intervention and the effects of the interventions have been systematically sorted out. In addition, we compared the effects of different intervention approaches, which help people with different cognitive states to choose appropriate intervention programs. With the development of imaging technology, many studies have discussed the neural mechanism of cognitive intervention training and the effects of cognitive intervention from the perspective of neuroplasticity. Behavioral studies and neural mechanism studies are used to improve the understanding of cognitive interventions for the treatment of cognitive impairment.

A Decade Later on How to "Use It" So We Don't "Lose It": An Update on the Unanswered Questions about the Influence of Activity Participation on Cognitive Performance in Older Age

Activity engagement is a modifiable factor that has been widely-cited as being good for the aging brain and cognition and represents a valuable target for reducing dementia risk. However, specific issues about activity engagement (mental, social, and physical) and cognition in older adulthood remain, and Bielak [Gerontology 2010;56: 507-519] reviewed seven major methodological and theoretical questions about this relationship. We present an updated reflection on these key questions, focusing on research published in the last 10 years. For some questions, a significant amount of work has been done and conclusions have become clearer; for others, there have been few additions to the literature and our knowledge remains much the same as it was a decade ago. We review the issues identified in the 2010 paper including the directionality and temporal nature of the relationship; whether specific activity domains offer different benefits to cognition and what domain(s) of cognition are affected; variation in the relation by age, gender, or education; potential mechanisms involved; and how activity engagement is assessed. For each, we present the most up-to-date research, discuss remaining challenges and possible future directions. This formal unifying of the information in the field is intended as a guide to support continued progress by spurring on studies addressing specific questions while reminding researchers of critical issues. We conclude with recommendations that future studies investigating the link between activity engagement and cognitive performance in adulthood should consider.

Effects of preventive interventions on neuroimaging biomarkers in subjects at-risk to develop Alzheimer's disease: A systematic review

Alzheimer's Disease (AD) is a multifactorial and complex neurodegenerative disorder. Some modifiable risk factors have been associated with an increased risk of appearance of the disease and/or cognitive decline. Preventive clinical trials aiming at reducing one or combined risk factors have been implemented and their potential effects assessed on cognitive trajectories and on AD biomarkers. However, the effect of interventions on surrogate markers, in particular imaging biomarkers, remains poorly understood. We conducted a review of the literature and analyzed 43 interventional studies that included physical exercise, nutrition, cognitive training or multidomain interventions, and assessed various brain imaging biomarkers, to determine the effects of preventive interventions on imaging biomarkers for subjects at-risk to develop AD. Deciphering the global and regional brain effect of each and combined interventions will help to better understand the interplay relationship between multimodal interventions, cognition, surrogate brain markers, and to better design primary and secondary outcomes for future preventive clinical trials. Those studies were pondered using generally-admitted quality criteria to reveal that interventions may affect the brain of patients with cognitive impairment rather than those without cognitive impairment thus indicating that particular care should be taken when selecting individuals for interventions. Additionally, a majority of the studies concurred on the effect of the interventions and particularly onto the frontal brain areas.

Cognitive training modified age-related brain changes in older adults with subjective memory decline

OBJECTIVES

Neuroimaging findings suggest that older adults with subjective memory decline (SMD) demonstrate some neurodegenerative brain changes and have high risk of developing dementia, but relatively little is known about the effectiveness of interventions for SMD. This study aimed to examine the effects of cognitive training on resting-state brain activity in SMD.

METHOD

This study employed the amplitude of low frequency fluctuations (ALFF) and resting state functional connectivity (rs-FC) analyses. After baseline evaluations, participants were randomly allocated to the intervention and control group to receive a four-week cognitive training and lectures on health and aging, respectively. All participants were scanned before and after training with an interval of about three months.

RESULTS

(1) Participants in the intervention group showed significant improvements on the Associative Learning Test (ALT) and the Digit Span Forward task compared to the control group; (2) ALFF in the occipital lobe for the control group increased significantly, while that for the intervention group remained the same; ALFF changes were negatively correlated with ALT performance in the control group; (3) The mean value of rs-FC for the intervention group decreased, while that for the control group showed a trend of increase; rs-FC changes were also negatively correlated with ALT performance in the control group.

CONCLUSIONS

Resting-state brain activities in occipital region increased with aging. The cognitive training could counteract this brain function changes associated with aging or even reverse the changes. These findings provide new insights into the understanding of brain plasticity in posterior areas in SMD.

TRIAL REGISTRATION

ChiCTR-IOR-15006165 in the Chinese Clinical Trial Registry.

Five-Year Changes in Cognitive Function and Their Predictor in Adult Moyamoya Disease

OBJECTIVE

The long-term outcomes of cognitive function in moyamoya disease remain unknown. We aimed to assess 5-year changes in cognitive function in adult moyamoya disease patients and to evaluate the value of the magnetic resonance angiography (MRA) steno-occlusive score to predict cognitive changes.

METHODS

Participants comprised 20 consecutive patients whose cognitive functions had been evaluated using the Frontal Assessment Battery (FAB) and Neurobehavioral Cognitive Status Examination (Cognistat) at baseline and reassessed 5 years later.

RESULTS

The total FAB score and total Cognistat score were lower after 5 years in 9 patients each. The Wilcoxon signed-rank test showed that subscores for conceptualization and comprehension increased, while subscores for mental flexibility, programming, and inhibitory control significantly decreased after 5 years. The right MRA total score and right posterior cerebral artery score were negatively associated with 5-year changes in the total FAB score and total Cognistat score. The right posterior cerebral artery score was significantly associated with changes in subscores for mental flexibility, programming, sensitivity to interference, and construction.

CONCLUSIONS

Specific cognitive domains can decline over time in patients with adult moyamoya disease. MRA findings might be useful for predicting future declines in cognitive function.

Cognitive Improvement After Multi-Domain Lifestyle Interventions in an APOE ɛ4 Homozygous Carrier with Mild Cognitive Impairment: A Case Report and Literature Review

Alzheimer’s disease (AD) is a degenerative disease of the central nervous system with insidious onset and chronic progression. The pathogenesis of AD is complex, which is currently considered to be the result of the interaction between genetic and environmental factors. The APOE ɛ4 is the strongest genetic risk factor for sporadic AD and a risk factor for progression from mild cognitive impairment (MCI) to AD. So far, no effective drugs have been found for the progression of MCI. However, the effects of nonpharmacological interventions such as nutrition, cognitive, and physical exercises on early AD have received increasing attention. We followed up cognitive assessment scales, Aβ-PET and MRI examination of a patient with MCI for 4 years, who carried APOE ɛ4 homozygous with a clear family history. After 4 years of multi-domain lifestyle interventions including nutrition, socialization, and physical exercises, the patient’s cognitive function, especially memory function, improved significantly. Intracerebral amyloid deposition was decreased, and hippocampal atrophy improved. Based on this case, this study reviewed and discussed the interaction of APOE ɛ4 with the environment in AD research in recent years, as well as the impact and mechanisms of non-pharmaceutical multi-domain lifestyle interventions on MCI or early AD. Both the literature review and this case showed that multi-domain lifestyle interventions may reduce the risk of disease progression by reducing Aβ deposition in the brain and other different pathologic mechanisms, which offers promise in brain amyloid-positivity or APOE ɛ4 carriers.

Can a serious game-based cognitive training attenuate cognitive decline related to Alzheimer's disease? Protocol for a randomized controlled trial

BACKGROUND

Alzheimer's disease (AD) is a major public health issue. Cognitive interventions such as computerized cognitive trainings (CCT) are effective in attenuating cognitive decline in AD. However, in those at risk of dementia related to AD, results are heterogeneous. Efficacy and feasibility of CCT needs to be explored in depth. Moreover, underlying mechanisms of CCT effects on the three cognitive domains typically affected by AD (episodic memory, semantic memory and spatial abilities) remain poorly understood.

METHODS

In this bi-centric, randomized controlled trial (RCT) with parallel groups, participants (planned N = 162, aged 60-85 years) at risk for AD and with at least subjective cognitive decline will be randomized to one of three groups. We will compare serious game-based CCT against a passive wait list control condition and an active control condition (watching documentaries). Training will consist of daily at-home sessions for 10 weeks (50 sessions) and weekly on-site group meetings. Subsequently, the CCT group will continue at-home training for an additional twenty-weeks including monthly on-site booster sessions. Investigators conducting the cognitive assessments will be blinded. Group leaders will be aware of participants' group allocations. Primarily, we will evaluate change using a compound value derived from the comprehensive cognitive assessment for each of three cognitive domains. Secondary, longitudinal functional and structural magnetic resonance imaging (MRI) and evaluation of blood-based biomarkers will serve to investigate neuronal underpinnings of expected training benefits.

DISCUSSION

The present study will address several shortcomings of previous CCT studies. This entails a comparison of serious game-based CCT with both a passive and an active control condition while including social elements crucial for training success and adherence, the combination of at-home and on-site training, inclusion of booster sessions and assessment of physiological markers. Study outcomes will provide information on feasibility and efficacy of serious game-based CCT in older adults at risk for AD and will potentially generalize to treatment guidelines. Moreover, we set out to investigate physiological underpinnings of CCT induced neuronal changes to form the grounds for future individually tailored interventions and neuro-biologically informed trainings.

TRIAL REGISTRATION

This RCT was registered 1st of July 2020 at clinicaltrials.gov (Identifier NCT04452864).

Sex differences in patterns of associative memory-related activation in individuals at risk of Alzheimer's disease

The risk of developing Alzheimer's disease dementia is higher in females compared to males and is greater in individuals with subjective cognitive decline and mild cognitive impairment than in healthy controls. We used a multivariate behavioral partial least square correlation analysis to examine how relationships between memory-related activation and associative memory performance vary as a function of sex and clinical status. This was assessed in 182 participants from the Consortium for the Early Identification of Alzheimer's Disease-Quebec cohort, which were stratified according to sex (Male, Female) and clinical status (healthy controls, subjective cognitive decline, mild cognitive impairment). We found 6 significant latent variables mainly expressing: (1) overall sex differences; (2) between-sex differences according to clinical status; and (3) within-sex differences according to clinical status in relationships between whole-brain memory-related activation and memory performance. These patterns of activation mostly involved the default mode and fronto-parietal networks. Our results have implication in understanding the macro-scale functional processes possibly contributing to the higher risk of cognitive decline in females compared to males in the context of aging and early Alzheimer's disease.

Beneficial effects of whole-body vibration exercise for brain disorders in experimental studies with animal models: a systematic review

Brain disorders have been a health challenge and is increasing over the years. Early diagnosis and interventions are considered essential strategies to treat patients at risk of brain disease. Physical exercise has shown to be beneficial for patients with brain diseases. A type of exercise intervention known as whole-body vibration (WBV) exercise gained increasing interest. During WBV, mechanical vibrations, produced by a vibrating platform are transmitted, to the body. The purpose of the current review was to summarize the effects of WBV exercise on brain function and behavior in experimental studies with animal models. Searches were performed in EMBASE, PubMed, Scopus and Web of Science including publications from 1960 to July 2021, using the keywords "whole body vibration" AND (animal or mice or mouse or rat or rodent). From 1284 hits, 20 papers were selected. Rats were the main animal model used (75%) followed by mice (20%) and porcine model (5%), 16 studies used males species and 4 females. The risk of bias, accessed with the SYRCLE Risk of Bias tool, indicated that none of the studies fulfilled all methodological criteria, resulting in possible bias. Despite heterogeneity, the results suggest beneficial effects of WBV exercise on brain functioning, mainly related to motor performance, coordination, behavioral control, neuronal plasticity and synapse function. In conclusion, the findings observed in animal studies justifies continued clinical research regarding the effectiveness and potential of WBV for the treatment of various types of brain disorders such as trauma, developmental disorders, neurogenetic diseases and other neurological diseases.

Altered Structural and Functional Patterns Within Executive Control Network Distinguish Frontal Glioma-Related Epilepsy

Background

The tumor invasion of the frontal lobe induces changes in the executive control network (ECN). It remains unclear whether epileptic seizures in frontal glioma patients exacerbate the structural and functional alterations within the ECN, and whether these changes can be used to identify glioma-related seizures at an early stage. This study aimed to investigate the altered structural and functional patterns of ECN in frontal gliomas without epilepsy (non-FGep) and frontal gliomas with epilepsy (FGep) and to evaluate whether the patterns can accurately distinguish glioma-related epilepsy.

Methods

We measured gray matter (GM) volume, regional homogeneity (ReHo), and functional connectivity (FC) within the ECN to identify the structural and functional changes in 50 patients with frontal gliomas (29 non-FGep and 21 FGep) and 39 healthy controls (CN). We assessed the relationships between the structural and functional changes and cognitive function using partial correlation analysis. Finally, we applied a pattern classification approach to test whether structural and functional abnormalities within the ECN can distinguish non-FGep and FGep from CN subjects.

Results

Within the ECN, non-FGep and FGep showed increased local structure (GM) and function (ReHo), and decreased FC between brain regions compared to CN. Also, non-FGep and FGep showed differential patterns of structural and functional abnormalities within the ECN, and these abnormalities are more severe in FGep than in non-FGep. Lastly, FC between the right superior frontal gyrus and right dorsolateral prefrontal cortex was positively correlated with episodic memory scores in non-FGep and FGep. In particular, the support vector machine (SVM) classifier based on structural and functional abnormalities within ECN could accurately distinguish non-FGep and FGep from CN, and FGep from non-FGep on an individual basis with very high accuracy, area under the curve (AUC), sensitivity, and specificity.

Conclusion

Tumor invasion of the frontal lobe induces local structural and functional reorganization within the ECN, exacerbated by the accompanying epileptic seizures. The ECN abnormalities can accurately distinguish the presence or absence of epileptic seizures in frontal glioma patients. These findings suggest that differential ECN patterns can assist in the early identification and intervention of epileptic seizures in frontal glioma patients.

Cognitive Training with Neurofeedback Using fNIRS Improves Cognitive Function in Older Adults

This study examined the effects of a 4-week cognitive training program with neurofeedback (CT-NF) among 86 healthy adults (M = 66.34 years, range 54-84) randomized to either a treatment (app-based ABC games) or control (Tetris) group. Participants completed seven cognitive assessments, pre- and post-intervention, and measured their cortical brain activity using a XB-01 functional near-infrared spectroscopy (fNIRS) brain sensor, while engaging in CT-NF. The treatment (ABC) group showed significant (pre/post-intervention) improvements in memory (MEM), verbal memory (VBM), and composite cognitive function, while the control group did not. However, both groups showed significant improvements in processing speed (PS) and executive function (EF). In line with other studies, we found that strength of cortical brain activity (measured during CT-NF) was associated with both cognitive (pre and post) and game performance. In sum, our findings suggest that CT-NF and specifically ABC exercises, confer improved cognition in the domains of MEM, VBM, PS, and EF.

Brain network hierarchy reorganization in Alzheimer's disease: A resting‐state functional magnetic resonance imaging study

Hierarchy is a fundamental organizational principle of the human brain network. Whether and how the network hierarchy changes in Alzheimer's disease (AD) remains unclear. To explore brain network hierarchy alterations in AD and their clinical relevance. Forty‐nine healthy controls (HCs), 49 patients with mild cognitive impairment (MCI), and 49 patients with AD were included. The brain network hierarchy of each group was depicted by connectome gradient analyses. We assessed the network hierarchy changes by comparing the gradient values in each network across the AD, MCI, and HC groups. Whole‐brain voxel‐level gradient values were compared across the AD, MCI, and HC groups to identify abnormal brain regions. Finally, we examined the relationships between altered gradient values and clinical features. In the secondary gradient, the posterior default mode network (DMN) gradient values decreased significantly in patients with AD compared with HCs. Regionally, compared with HCs, both MCI and AD groups showed that most of the brain regions with increased gradient values were located in anterior DMN, while most of the brain regions with decreased gradient values were located in posterior DMN. The decrease of gradients in the left middle occipital gyrus was associated with better logical memory performance. The increase of gradients in the right middle frontal gyrus was associated with lower rates of dementia. The network hierarchy changed characteristically in patients with AD and was closely related to memory function and disease severity. These results provide a novel view for further understanding the underlying neuro‐mechanisms of AD.

Cortical Thickness Changes After Computerized Working Memory Training in Patients With Mild Cognitive Impairment

Background

Adaptive computerized working memory (WM) training has shown favorable effects on cerebral cortical thickness as compared to non-adaptive training in healthy individuals. However, knowledge of WM training-related morphological changes in mild cognitive impairment (MCI) is limited.

Objective

The primary objective of this double-blind randomized study was to investigate differences in longitudinal cortical thickness trajectories after adaptive and non-adaptive WM training in patients with MCI. We also investigated the genotype effects on cortical thickness trajectories after WM training combining these two training groups using longitudinal structural magnetic resonance imaging (MRI) analysis in Freesurfer.

Method

Magnetic resonance imaging acquisition at 1.5 T were performed at baseline, and after four- and 16-weeks post training. A total of 81 individuals with MCI accepted invitations to undergo 25 training sessions over 5 weeks. Longitudinal Linear Mixed effect models investigated the effect of adaptive vs. non-adaptive WM training. The LME model was fitted for each location (vertex). On all statistical analyzes, a threshold was applied to yield an expected false discovery rate (FDR) of 5%. A secondary LME model investigated the effects of LMX1A and APOE-ε4 on cortical thickness trajectories after WM training.

Results

A total of 62 participants/patients completed the 25 training sessions. Structural MRI showed no group difference between the two training regimes in our MCI patients, contrary to previous reports in cognitively healthy adults. No significant structural cortical changes were found after training, regardless of training type, across all participants. However, LMX1A-AA carriers displayed increased cortical thickness trajectories or lack of decrease in two regions post-training compared to those with LMX1A-GG/GA. No training or training type effects were found in relation to the APOE-ε4 gene variants.

Conclusion

The MCI patients in our study, did not have improved cortical thickness after WM training with either adaptive or non-adaptive training. These results were derived from a heterogeneous population of MCI participants. The lack of changes in the cortical thickness trajectory after WM training may also suggest the lack of atrophy during this follow-up period. Our promising results of increased cortical thickness trajectory, suggesting greater neuroplasticity, in those with LMX1A-AA genotype need to be validated in future trials.

Cerebral Blood Flow Alterations in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Arterial Spin Labeling Studies

Objective

Arterial spin labeling (ASL) studies have revealed inconsistent regional cerebral blood flow (CBF) alterations in patients with type 2 diabetes mellitus (T2DM). The aim of this systematic review and meta-analysis was to identify concordant regional CBF alterations in T2DM.

Methods

A systematic review was conducted to the published literatures comparing cerebral perfusion between patients with T2DM and healthy controls using ASL. The seed-based d mapping (SDM) was further used to perform quantitative meta-analysis on voxel-based literatures and to estimate the regional CBF alterations in patients with T2DM. Metaregression was performed to explore the associations between clinical characteristics and cerebral perfusion alterations.

Results

A total of 13 studies with 14 reports were included in the systematic review and 7 studies with 7 reports were included in the quantitative meta-analysis. The qualitative review found widespread CBF reduction in cerebral lobes in T2DM. The meta-analysis found increased regional CBF in right supplementary motor area and decreased regional CBF in bilateral middle occipital gyrus, left caudate nucleus, right superior parietal gyrus, and left calcarine fissure/surrounding cortex in T2DM.

Conclusion

The patterns of cerebral perfusion alterations, characterized by the decreased CBF in occipital and parietal lobes, might be the neuropathology of visual impairment and cognitive aging in T2DM.

Cognitive Training Modulates Brain Hypersynchrony in a Population at Risk for Alzheimer's Disease

BACKGROUND

Recent studies demonstrated that brain hypersynchrony is an early sign of dysfunction in Alzheimer's disease (AD) that can represent a proxy for clinical progression. Conversely, non-pharmacological interventions, such as cognitive training (COGTR), are associated with cognitive gains that may be underpinned by a neuroprotective effect on brain synchrony.

OBJECTIVE

To study the potential of COGTR to modulate brain synchrony and to eventually revert the hypersynchrony phenomenon that characterizes preclinical AD.

METHODS

The effect of COGTR was examined in a sample of healthy controls (HC, n = 41, 22 trained) and individuals with subjective cognitive decline (SCD, n = 49, 24 trained). Magnetoencephalographic (MEG) activity and neuropsychological scores were acquired before and after a ten-week COGTR intervention aimed at improving cognitive function and daily living performance. Functional connectivity (FC) was analyzed using the phase-locking value. A mixed-effects ANOVA model with factors time (pre-intervention/post-intervention), training (trained/non-trained), and diagnosis (HC/SCD) was used to investigate significant changes in FC.

RESULTS

We found an average increase in alpha-band FC over time, but the effect was different in each group (trained and non-trained). In the trained group (HC and SCD), we report a reduction in the increase in FC within temporo-parietal and temporo-occipital connections. In the trained SCD group, this reduction was stronger and showed a tentative correlation with improved performance in different cognitive tests.

CONCLUSION

COGTR interventions could mitigate aberrant increases in FC in preclinical AD, promoting brain synchrony normalization in groups at a higher risk of developing dementia.

Bilingualism and Aging: Implications for (Delaying) Neurocognitive Decline

As a result of advances in healthcare, the worldwide average life expectancy is steadily increasing. However, this positive trend has societal and individual costs, not least because greater life expectancy is linked to higher incidence of age-related diseases, such as dementia. Over the past few decades, research has isolated various protective "healthy lifestyle" factors argued to contribute positively to cognitive aging, e.g., healthy diet, physical exercise and occupational attainment. The present article critically reviews neuroscientific evidence for another such factor, i.e., speaking multiple languages. Moreover, with multiple societal stakeholders in mind, we contextualize and stress the importance of the research program that seeks to uncover and understand potential connections between bilingual language experience and cognitive aging trajectories, inclusive of the socio-economic impact it can have. If on the right track, this is an important line of research because bilingualism has the potential to cross-over socio-economic divides to a degree other healthy lifestyle factors currently do not and likely cannot.

Cognitive impairment and World Trade Centre-related exposures

On 11 September 2001 the World Trade Center (WTC) in New York was attacked by terrorists, causing the collapse of multiple buildings including the iconic 110-story 'Twin Towers'. Thousands of people died that day from the collapse of the buildings, fires, falling from the buildings, falling debris, or other related accidents. Survivors of the attacks, those who worked in search and rescue during and after the buildings collapsed, and those working in recovery and clean-up operations were exposed to severe psychological stressors. Concurrently, these 'WTC-affected' individuals breathed and ingested a mixture of organic and particulate neurotoxins and pro-inflammogens generated as a result of the attack and building collapse. Twenty years later, researchers have documented neurocognitive and motor dysfunctions that resemble the typical features of neurodegenerative disease in some WTC responders at midlife. Cortical atrophy, which usually manifests later in life, has also been observed in this population. Evidence indicates that neurocognitive symptoms and corresponding brain atrophy are associated with both physical exposures at the WTC and chronic post-traumatic stress disorder, including regularly re-experiencing traumatic memories of the events while awake or during sleep. Despite these findings, little is understood about the long-term effects of these physical and mental exposures on the brain health of WTC-affected individuals, and the potential for neurocognitive disorders. Here, we review the existing evidence concerning neurological outcomes in WTC-affected individuals, with the aim of contextualizing this research for policymakers, researchers and clinicians and educating WTC-affected individuals and their friends and families. We conclude by providing a rationale and recommendations for monitoring the neurological health of WTC-affected individuals.

Intrinsic Brain Activity Alterations in Patients With Mild Cognitive Impairment-to-Normal Reversion: A Resting-State Functional Magnetic Resonance Imaging Study From Voxel to Whole-Brain Level

Mild cognitive impairment (MCI) reversion refers to patients with MCI who revert from MCI to a normal cognitive state. Exploring the underlying neuromechanism of MCI reverters may contribute to providing new insights into the pathogenesis of Alzheimer's disease and developing therapeutic interventions. Information on patients with MCI and healthy controls (HCs) was collected from the Alzheimer's Disease Neuroimaging Initiative database. We redefined MCI reverters as patients with MCI whose logical memory scores changed from MCI to normal levels using the logical memory criteria. We explored intrinsic brain activity alterations in MCI reverters from voxel, regional, and whole-brain levels by comparing resting-state functional magnetic resonance imaging metrics of the amplitude of low-frequency of fluctuation (ALFF), the fractional amplitude of low-frequency fluctuation (fALFF), percent amplitude of fluctuation (PerAF), regional homogeneity (ReHo), and degree centrality (DC) between MCI reverters and HCs. Finally, partial correlation analyses were conducted between cognitive scale scores and resting-state functional magnetic resonance imaging metrics of brain regions, revealing significant group differences. Thirty-two patients with MCI from the Alzheimer's Disease Neuroimaging Initiative database were identified as reverters. Thirty-seven age-, sex-, and education-matched healthy individuals were also enrolled. At the voxel level, compared with the HCs, MCI reverters had increased ALFF, fALFF, and PerAF in the frontal gyrus (including the bilateral orbital inferior frontal gyrus and left middle frontal gyrus), increased PerAF in the left fusiform gyrus, and decreased ALFF and fALFF in the right inferior cerebellum. Regarding regional and whole-brain levels, MCI reverters showed increased ReHo in the left fusiform gyrus and right median cingulate and paracingulate gyri; increased DC in the left inferior temporal gyrus and left medial superior frontal; decreased DC in the right inferior cerebellum and bilateral insular gyrus relative to HCs. Furthermore, significant correlations were found between cognitive performance and neuroimaging changes. These findings suggest that MCI reverters show significant intrinsic brain activity changes compared with HCs, potentially related to the cognitive reversion of patients with MCI. These results enhance our understanding of the underlying neuromechanism of MCI reverters and may contribute to further exploration of Alzheimer's disease.

Effects of Combined Cognitive and Exercise Interventions on Poststroke Cognitive Function: A Systematic Review and Meta-Analysis

Objective

We investigated combined cognitive and exercise interventions in the literature and summarized their effectiveness in improving poststroke cognitive impairment (PSCI). Data Sources. Electronic databases and trial registries were searched from their inception until July 2020. Study Selection. Trials were collected with the following study inclusion criteria: (1) patients over 18 years of age who were diagnosed with PSCI; (2) combined cognitive-exercise interventions, regardless of the order of the two types of interventions or whether they were administered simultaneously; (3) any control group studied at the same time that was deemed acceptable, including no intervention/routine care, delayed intervention, sham intervention, and passive training; (4) the use of any validated cognitive neuropsychological test to evaluate cognitive function; and (5) clinically administered random trials with controls. Data Extraction. Five randomized controlled trials met the inclusion criteria. Two reviewers independently assessed the eligibility of the full texts and methodological quality of the included studies using the Cochrane risk of bias tool. Inconsistent results were resolved by additional discussion or decided by a third examiner, if necessary. Data Analysis. Meta-analysis demonstrated that the combined interventions had a significant effect on executive function and working memory [Stroop test (time), standardized mean difference (SMD) = 0.42, 95% confidence interval (CI): 0.80–0.04, p = 0.02; Trail Making Test, SMD = 0.49, 95% CI: 0.82–0.16, p = 0.004; Forward Digit Span Test, SMD = 0.91, 95% CI: 0.54–1.29, p ≤ 0.001]. While it was impossible to conduct a meta-analysis of global cognitive function and other cognitive domains, individual experiments demonstrated that the combined interventions played a significant role in global cognition, reasoning ability, logical thinking, and visual-spatial memory function.

Conclusions

Our analyses demonstrated that the combined interventions had a significant effect on the improvement of PSCI, particularly in terms of executive function. However, the moderate risk of bias in the included trials and the small number of relevant studies indicated a need for more uniform diagnostic and evaluation criteria, and larger trials would provide stronger evidence to better understand the effectiveness of the combined interventions. This trial is registered with trial registration number INPLASY202160090.

A controlled clinical efficacy trial of multimodal cognitive rehabilitation on episodic memory functioning in older adults with traumatic brain injury

OBJECTIVES

This study aimed to evaluate the impact of a 12-week, 24-session multimodal group cognitive intervention, the Cognitive Enrichment Program (CEP), on episodic memory in older adults with traumatic brain injury (TBI) compared to an active control group that received usual care in the form of individual holistic rehabilitation.

METHODS

In total, 37 patients with a TBI who were 57 to 90 years old were assigned to experimental (n = 23) and control (n = 14) groups in a semi-randomized, controlled, before-after intervention trial with follow-up at 6 months, with blinded outcome measurement. The CEP's Memory module consisted of memory strategies to promote encoding. Efficacy was evaluated by using Face-name association, Word list recall, and Text memory measures, and generalization was assessed with the Self-Evaluation Memory Questionnaire (SEMQ), the Psychological General Well-Being Index, and a satisfaction questionnaire.

RESULTS

ANCOVA mixed model repeated-measures analysis revealed a strong group-by-time interaction, with the experimental group showing statistically significant improvement on the Face-name association test, with a large effect size. We also found a statistically significant group-by-time interaction on 3 dimensions of the SEMQ generalization measure: the experimental group showed increased memorization of the content of Conversations, reduced Slips of attention, and increased memory of Political and social events, with medium to large effect sizes. The group also showed clinically significant improvements in psychological well-being. Scores on the satisfaction questionnaire indicated a perceived positive impact on daily life habits requiring memory abilities.

CONCLUSIONS

The CEP is a promising cognitive rehabilitation program for older individuals with TBI, showing high satisfaction in participants, that could improve their episodic memory functioning as well as enhance their psychological well-being. ClinicalTrials.gov Identifier: NCT04590911.

Transcranial direct current stimulation as an adjunct to cognitive training for older adults with mild cognitive impairment: A randomized controlled trial

BACKGROUND

Cognitive training (CT) for individuals with mild cognitive impairment (MCI) may not be optimal for enhancing cognitive functioning. Coupling CT with transcranial direct current stimulation (tDCS) may maximize the strength of transmission across synaptic circuits in pathways that are stimulated by CT. The synergistic effects arising from this combination could be superior to those with administration of CT alone.

OBJECTIVES

To investigate whether the receiving tDCS combined with CT is superior to CT alone on domain-specific and task-specific cognitive outcomes in older adults with MCI.

METHODS

This double-blind, sham-controlled randomized trial included 67 older adults with MCI assigned to 3 groups: 1) tDCS combined with CT (tDCS+CT), 2) sham tDCS combined with CT (sham tDCS+CT) and 3) CT alone. Nine sessions of computerized CT were administered to the 3 groups for 3 weeks. In addition, tDCS and sham tDCS was delivered to the left dorsolateral prefrontal cortex to the tDCS+CT and sham tDCS+CT groups, respectively, simultaneously with CT. Standardized cognitive assessments were performed at baseline, post-intervention, and at 6-week follow-up. Participants' performance in the CT tasks was rated every session.

RESULTS

The 3 groups showed improvements in global cognition and everyday memory (P<0.017) after the intervention and at follow-up, with larger effect sizes in the tDCS+CT than other groups (d>0.94) but with no significant differences between groups. Regarding CT outcomes, the groups showed significant differences in favour of the tDCS+CT group in decreasing the completion and reaction times of working memory and attention activities (P<0.017).

CONCLUSIONS

tDCS combined with CT was not superior to sham tDCS with CT and CT alone in its effects on domain-specific cognitive outcomes, but it did provide comparatively larger effect sizes and improve the processing speed of task-specific outcomes. CLINICALTRIALS.GOV: NCT03441152.

Cognitive reserve and the effects of virtual reality-based cognitive training on elderly individuals with mild cognitive impairment and normal cognition

BACKGROUND

Cognitive reserve (CR) is a concept proposed to account for discrepancies between the extent of brain pathology and clinical manifestations of that pathology. This study aimed to explore the associations between CR and the effects of cognitive training using fully immersive virtual reality (VR).

METHODS

A total of 44 older adults (22 cognitively normal, 22 with mild cognitive impairment) underwent eight cognitive training sessions using VR for a period of 4 weeks. CR was assessed using the Cognitive Reserve Index questionnaire (CRIq). To evaluate baseline cognitive function and the effects of VR training, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery was administered to all participants before and after the training.

RESULTS

Greater improvement in the total CERAD score was seen for cognitively normal participants with higher versus lower scores on the Education subdomain of the CRIq. Among patients with mild cognitive impairment, none of the CRIq subdomain scores (Education, Working Activity, Leisure Time) were related to a change in CERAD total scores. The CRIq total score did not predict the improvement of global cognition in either group.

CONCLUSIONS

This study revealed different impacts of CR on cognitive training according to the participants' cognitive status. It also suggests that employing three proxies of CR rather than using a composite score would provide a more accurate understanding of one's CR.

Different Modulatory Effects of Cognitive Training and Aerobic Exercise on Resting State Functional Connectivity of Entorhinal Cortex in Community-Dwelling Older Adults

The entorhinal cortex (EC) plays an essential role in age-related cognitive decline. However, the effect of functional connectivity (FC) changes between EC and other cerebral cortices on cognitive function remains unclear. The aim of this study was to explore the modulation of two interventions (cognitive training and aerobic exercise) on EC-FC in community-dwelling older adults. In total, 94 healthy older adults aged between 65 and 75 years were assigned to either the cognitive training or aerobic exercise group to receive 24 sessions over 12 weeks, or to a control group. Resting-state functional magnetic resonance imaging was performed at both baseline and 12-month follow-up. Compared to the cognitive training group, the aerobic exercise group showed greater EC-FC in the bilateral middle temporal gyrus, right supramarginal gyrus, left angular gyrus, and right postcentral gyrus. Compared to the control group, the cognitive training group had a decreased EC-FC in the right hippocampus, right middle temporal gyrus, left angular gyrus, and right postcentral gyrus and an increased EC-FC in the bilateral pallidum, while the aerobic exercise group showed increased EC-FC between the right medial prefrontal cortex(mPFC), bilateral pallidum, and right precuneus. Baseline EC-FC in the mPFC was positively correlated with the visuospatial/constructional index score of the Repeatable Battery for the Assessment of Neuropsychological Status. In the cognitive training group, EC-FC value changes in the right hippocampus were negatively correlated with changes in the RBANS delayed memory index score, while in the aerobic exercise group, EC-FC value changes in the left angular gyrus were positively correlated with changes in the RBANS attention index score. These findings support the hypothesis that both cognitive training and aerobic exercise can modulate EC-FC in aging populations but through different neural pathways.

Effect of Cognitive Training in Fully Immersive Virtual Reality on Visuospatial Function and Frontal-Occipital Functional Connectivity in Predementia: Randomized Controlled Trial

Background

Cognitive training can potentially prevent cognitive decline. However, the results of recent studies using semi-immersive virtual reality (VR)-assisted cognitive training are inconsistent.

Objective

We aimed to examine the hypothesis that cognitive training using fully immersive VR, which may facilitate visuospatial processes, could improve visuospatial functioning, comprehensive neuropsychological functioning, psychiatric symptoms, and functional connectivity in the visual brain network in predementia.

Methods

Participants over 60 years old with subjective cognitive decline or mild cognitive impairment from a memory clinic were randomly allocated to the VR (n=23) or the control (n=18) group. The VR group participants received multidomain and neuropsychologist-assisted cognitive training in a fully immersive VR environment twice a week for 1 month. The control group participants did not undergo any additional intervention except for their usual therapy such as pharmacotherapy. Participants of both groups were evaluated for cognitive function using face-to-face comprehensive neuropsychological tests, including the Rey-Osterrieth Complex Figure Test (RCFT) copy task; for psychiatric symptoms such as depression, apathy, affect, and quality of life; as well as resting-state functional magnetic resonance imaging (rsfMRI) at baseline and after training. Repeated-measures analysis of variance was used to compare the effect of cognitive training between groups. Seed-to-voxel–based analyses were used to identify the cognitive improvement–related functional connectivity in the visual network of the brain.

Results

After VR cognitive training, significant improvement was found in the total score (F_1,39=14.69, P=.001) and basic components score of the RCFT copy task (F_1,39=9.27, P=.005) compared with those of the control group. The VR group also showed improvements, albeit not significant, in naming ability (F_1,39=3.55, P=.07), verbal memory delayed recall (F_1,39=3.03, P=.09), and phonemic fluency (F_1,39=3.08, P=.09). Improvements in psychiatric symptoms such as apathy (F_1,39=7.02, P=.01), affect (F_1,39=14.40, P=.001 for positive affect; F_1,39=4.23, P=.047 for negative affect), and quality of life (F_1,39=4.49, P=.04) were found in the VR group compared to the control group. Improvement in the RCFT copy task was associated with a frontal-occipital functional connectivity increase revealed by rsfMRI in the VR group compared to the control group.

Conclusions

Fully immersive VR cognitive training had positive effects on the visuospatial function, apathy, affect, quality of life, and increased frontal-occipital functional connectivity in older people in a predementia state. Future trials using VR cognitive training with larger sample sizes and more sophisticated designs over a longer duration may reveal greater improvements in cognition, psychiatric symptoms, and brain functional connectivity.

Trial Registration

Clinical Research Information Service KCT0005243; https://tinyurl.com/2a4kfasa

Deficit of Cross-Frequency Integration in Mild Cognitive Impairment and Alzheimer's Disease: A Multilayer Network Approach

BACKGROUND

Studies at specific frequencies have shown abnormalities in brain functional networks among mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients. Previous studies have failed to take into account the possibility that optimal cognitive integration requires interactions between different frequency bands.

PURPOSE

To study whether there is abnormal cross-frequency integration in patients' brains during disease progression.

STUDY TYPE

Retrospective.

POPULATION

Forty-six normal control (NC), 85 patients with MCI, and 31 patients with AD.

FIELD STRENGTH/SEQUENCE

3T.

ASSESSMENT

Multilayer network models were constructed for NC, MCI, and AD, and multilayer participation coefficient (MPC) was used to study the changes of the interlayer relationship in the course of disease development. In addition, MPC and an overlapping degree were combined to classify nodes in the network, and the role of key nodes in the interlayer interaction was mainly observed. Finally, the correlation between multilayer network measures and cognitive function was investigated.

STATISTICAL TESTS

Pearson chi-squared two-tailed test, one-way analysis of variance (ANOVA), nonparametric Spearman correlation coefficient r, and the false discovery rate.

RESULTS

The MPC of the network decreased significantly in MCI (P < 0.05) and AD (P < 0.05). The number of intralayer nodes increased significantly (MCI [P < 0.05], AD [P < 0.05]) and the number of interlayer nodes decreased significantly. Centrality loss between frequencies of a large number of hub nodes, among which the damaged hub nodes included the left hippocampus, left precuneus, right precuneus, left posterior cingulate gyrus, left precentral gyrus, right precentral gyrus, left medial superior frontal gyrus, and right postcentral gyrus. MPC was significantly associated with memory impairment in patients (AD [Spearman's r = 0.526, P < 0.05], MCI [Spearman's r = 0.229, P < 0.05]), and these related regions included damaged hub nodes in patients.

DATA CONCLUSION

In the multilayer networks of patients, there was an obvious deficit in cross-frequency integration and the hub nodes were preferentially damaged. Moreover, these vulnerable hubs are associated with patients' cognitive scores.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 3.

Functional brain changes associated with cognitive training in healthy older adults: A preliminary ALE meta-analysis

Accumulating evidence suggests that cognitive training (CT) programs may provide healthy older adults (OAs) with cognitive benefits that are accompanied by alterations in neural activity. The current review offers the first quantitative synthesis of the available literature on the neural effects of CT in healthy aging. It was hypothesized that OAs would evidence increased and decreased neural activations across various challenging CTs, and that these effects would be observed as significantly altered clusters within regions of the frontoparietal network (FPN). Online databases and reference lists were searched to identify peer-reviewed publications that reported assessment of neural changes associated with CT programs in healthy OAs. Among the 2097 candidate studies identified, 14 studies with a total of 238 participants met inclusionary criteria. GingerALE software was used to quantify neural effects in a whole-brain analysis. The activation likelihood estimation technique revealed significant increases in activation following CT in the left hemisphere middle frontal gyrus, precentral gyrus, and posterior parietal cortex, extending to the superior occipital gyrus. Two clusters of diminished neural activity following CT were identified within the right hemisphere middle frontal gyrus and supramarginal gyrus, extending to the superior temporal gyrus. These results provide preliminary evidence of common neural effects of different CT interventions within regions of the FPN. Findings may inform future investigations of neuroplasticity across the lifespan, including clinical applications of CT, such as assessing treatment outcomes.

IN VIVO ASSESSMENT OF AMYLOID AND GLUCOSE SIGNATURES IN SUBJECTIVE COGNITIVE DECLINE SUBJECTS

Subjective cognitive decline (SCD), characterized by self-perceived subtle cognitive impairment ahead of the appearance of explicit and measurable cognitive deficits, is regarded as the preclinical manifestation of the pathological change continuum of Alzheimer’s disease (AD). We were committed to exploring the amyloid and glucose metabolic signatures related to imminent brain metabolic changes in SCD subjects. This study included 39 subjects (mean age = 71.9 years; 14 males and 25 females) diagnosed with SCD disease and 39 gender-matched healthy controls (HCs) (mean age = 75.2; 16 males and 23 females) with brain [18F] fluorodeoxyglucose positron emission tomography (PET) images and [18F] florbetapir PET images. The standardized uptake value ratios (SUVRs) of PET images within the regions of interest (ROIs) were calculated. Inter-group SUVR differences were assessed by two-sample [Formula: see text]-testing and receiver operating characteristic curve (ROC) analyses. A generalized linear model (GLM) was employed to evaluate the correlations between amyloid and FDG uptake. Compared with HCs, SCD subjects showed significantly increased amyloid SUVR, as well as significantly increased glucose SUVR in the olfactory, amygdala, thalamus, heschl gyrus, superior and middle temporal gyrus and temporal pole (all [Formula: see text]). The amyloid SUVR of thalamus was found to have a better ROC result (area under the curve (AUC): 0.77, 95% confidence interval (CI): 0.66–0.86) in the HC group, as was the case with the glucose SUVR of the middle temporal gyrus (AUC: 0.83, 95% CI: 0.73–0.91). There were significant positive correlations between amyloid and glucose SUVRs ([Formula: see text]). The amyloid SUVR of the thalamus showed a significantly better main effect (odd ratio [Formula: see text] 2.91, 95% CI: 1.44–6.7, [Formula: see text]), and the glucose SUVR of the heschl gyrus indicated an enhanced main effect (odd ratio [Formula: see text] 5.08, 95% CI: 1.86–18.15, [Formula: see text]). SCD subjects demonstrated significant amyloid accumulation and glucose hypermetabolism in specific brain regions, and amyloid pathology overlapped with regions of glucose abnormality. These findings may advance the understanding of imminent pathological changes in the SCD stage and help to provide clinical guidelines for interventional management.

Latent patterns of task-related functional connectivity in relation to regions of hyperactivation in individuals at risk of Alzheimer's disease

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Hyperactivation relates to memory-related network dysfunction in SCD⁺ and MCI.

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Hippocampal hyperactivation and connectivity relate to worst memory performance.

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In contrast, neocortical hyperactivation and connectivity may reflect compensation.

The goal of this study was to assess how task-related hyperactivation relates to brain network dysfunction and memory performance in individuals at risk of Alzheimer’s disease (AD). Eighty participants from the CIMA-Q cohort were included, of which 28 had subjective cognitive decline plus (SCD⁺), as they had memory complaints and worries in addition to a smaller hippocampal volume and/or an APOE4 allele, 26 had amnestic mild cognitive impairment (MCI) and 26 were healthy controls without memory complaints. Functional magnetic resonance imaging (fMRI) activation was measured during an object-location memory task. Seed-partial least square analyses (seed-PLS) were conducted in controls and in the SCD⁺/MCI groups to yield sets of orthogonal latent variables (LVs) assessing the triple association between: i) seed activity in brain regions found to be hyperactive in individuals at risk of AD (left hippocampus, left superior parietal lobule, right inferior temporal lobe), ii) latent patterns of whole-brain task-related activation, and iii) associative memory performance. Three LVs in the SCD⁺ and MCI groups (67.88% of total covariance explained) and two LVs in the controls (77.85% of total covariance explained) were significant. While controls and SCD⁺/MCI groups shared a common pattern of memory-related connectivity, patterns of hyperactivation-networks interactions were unique to the clinical groups. Interestingly, higher hippocampal connectivity was associated with poorer memory performance whereas higher neocortical connectivity predicted better memory performance in SCD⁺ and MCI groups. Our data provides empirical evidence that early dysfunction in brain activation and connectivity is present in the very early stages of AD and offers new insights on the relationship between functional brain alterations and memory performance.

Past, Present, and Future of Non-invasive Brain Stimulation Approaches to Treat Cognitive Impairment in Neurodegenerative Diseases: Time for a Comprehensive Critical Review

Low birth rates and increasing life expectancy experienced by developed societies have placed an unprecedented pressure on governments and the health system to deal effectively with the human, social and financial burden associated to aging-related diseases. At present, ∼24 million people worldwide suffer from cognitive neurodegenerative diseases, a prevalence that doubles every five years. Pharmacological therapies and cognitive training/rehabilitation have generated temporary hope and, occasionally, proof of mild relief. Nonetheless, these approaches are yet to demonstrate a meaningful therapeutic impact and changes in prognosis. We here review evidence gathered for nearly a decade on non-invasive brain stimulation (NIBS), a less known therapeutic strategy aiming to limit cognitive decline associated with neurodegenerative conditions. Transcranial Magnetic Stimulation and Transcranial Direct Current Stimulation, two of the most popular NIBS technologies, use electrical fields generated non-invasively in the brain to long-lastingly enhance the excitability/activity of key brain regions contributing to relevant cognitive processes. The current comprehensive critical review presents proof-of-concept evidence and meaningful cognitive outcomes of NIBS in eight of the most prevalent neurodegenerative pathologies affecting cognition: Alzheimer's Disease, Parkinson's Disease, Dementia with Lewy Bodies, Primary Progressive Aphasias (PPA), behavioral variant of Frontotemporal Dementia, Corticobasal Syndrome, Progressive Supranuclear Palsy, and Posterior Cortical Atrophy. We analyzed a total of 70 internationally published studies: 33 focusing on Alzheimer's disease, 19 on PPA and 18 on the remaining neurodegenerative pathologies. The therapeutic benefit and clinical significance of NIBS remains inconclusive, in particular given the lack of a sufficient number of double-blind placebo-controlled randomized clinical trials using multiday stimulation regimes, the heterogeneity of the protocols, and adequate behavioral and neuroimaging response biomarkers, able to show lasting effects and an impact on prognosis. The field remains promising but, to make further progress, research efforts need to take in account the latest evidence of the anatomical and neurophysiological features underlying cognitive deficits in these patient populations. Moreover, as the development of in vivo biomarkers are ongoing, allowing for an early diagnosis of these neuro-cognitive conditions, one could consider a scenario in which NIBS treatment will be personalized and made part of a cognitive rehabilitation program, or useful as a potential adjunct to drug therapies since the earliest stages of suh diseases. Research should also integrate novel knowledge on the mechanisms and constraints guiding the impact of electrical and magnetic fields on cerebral tissues and brain activity, and incorporate the principles of information-based neurostimulation.