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Dissociable neural mechanisms of cognitive enhancement through transcranial stimulation and behavioral training.

BACKGROUND: Transcranial direct current stimulation (tDCS) and adaptive working memory (WM) training are promising cognitive enhancement approaches; however, their neural mechanisms and potential synergies remain poorly understood. OBJECTIVE: We directly compared how tDCS and WM training modulate neural oscillations during WM performance and examined whether combining both interventions produces additive effects. METHODS: We randomized 112 healthy adults into four groups: control (sham tDCS&#xa0;+&#xa0;non-adaptive 1-back), tDCS-only (active tDCS&#xa0;+&#xa0;non-adaptive 1-back), training-only (sham tDCS&#xa0;+&#xa0;adaptive n-back training), or combined (active tDCS&#xa0;+&#xa0;adaptive training). Participants underwent five daily intervention sessions. We recorded high-density EEG during transfer n-back tasks at baseline, post-intervention, and one-week follow-up. RESULTS: All active interventions improved WM performance relative to the control group, with the combined group showing the largest gains (n-back accuracy: +15.6% vs.&#xa0;+&#xa0;10.1% tDCS-only, +9.7% training-only, +0.7% control; all p&#xa0;<&#xa0;0.001). Critically, tDCS selectively increased gamma-band (30-50&#xa0;Hz) power in the frontal and parietal regions (cluster p&#xa0;=&#xa0;0.018, d&#xa0;>&#xa0;1.0), whereas WM training enhanced frontal theta-band (4-8&#xa0;Hz) power and theta-gamma phase-amplitude coupling (both cluster p&#xa0;<&#xa0;0.012, d&#xa0;>&#xa0;0.85). The combined group exhibited both neural signatures. Brain-behavior correlations revealed dissociable relationships: gamma increases predicted n-back accuracy improvements (r&#xa0;=&#xa0;0.61, p&#xa0;<&#xa0;0.001), whereas theta enhancements correlated with operation span gains (r&#xa0;=&#xa0;0.58, p&#xa0;=&#xa0;0.002). CONCLUSIONS: tDCS and WM training enhance cognition through distinct yet complementary neural mechanisms: tDCS via gamma-mediated cortical excitability and WM training via theta-mediated cognitive control. These findings provide neurophysiological evidence for multimodal enhancement strategies that target parallel pathways within WM networks.

Humans

Effectiveness of transcranial direct current stimulation with and without positive mood induction on worry and transdiagnostic cognitive-emotional processes: A randomized controlled trial.

The present study investigated the effectiveness of transcranial direct current stimulation (tDCS), with and without positive mood induction, on worry and key transdiagnostic cognitive-emotional processes, including attentional bias, working memory, problem solving, and emotion regulation, in individuals with high levels of worry. This single-blind randomized controlled trial included 45 individuals with high levels of worry. After a structured clinical interview, participants were randomly assigned, with gender balancing, to one of three groups: (1) tDCS alone, (2) tDCS combined with positive mood induction, or (3) a sham control group. Outcome measures were administered at three time points (pretest, posttest, and one-month follow-up) and assessed attentional bias (Dot Probe Task), working memory (1-back task), problem solving (Tower of London task), emotion regulation (Gross's Emotion Regulation Questionnaire), and worry severity (Penn State Worry Questionnaire; PSWQ). Repeated-measures ANOVA showed that both active groups (tDCS alone and tDCS + positive mood induction) significantly improved attentional bias, worry, working memory, problem solving, and emotion regulation compared to controls (p < 0.05). The combined intervention produced significantly greater gains than tDCS alone in working memory, problem solving, emotion regulation (p < 0.05), and reductions in attentional bias and worry (p < 0.001). All effects persisted at one-month follow-up (p < 0.05). tDCS reduces worry and attentional bias and enhances cognition and emotion regulation in individuals with high levels of worry. The combined intervention produced larger and more sustained improvements than tDCS alone across the assessed behavioral outcomes. These findings support further investigation of combining tDCS with structured positive mood induction while the mechanisms underlying the additional benefits remain to be established.

Humans

Cognitive-metabolic relationship in temporal lobe epilepsy: A systematic review.

OBJECTIVE: To summarize the current literature on neurometabolic dysfunction identified through brain imaging and its cognitive correlates in temporal lobe epilepsy (TLE). BACKGROUND: Cognitive decline contributes to chronic disability in TLE. The pathophysiology of cognitive decline in TLE is poorly understood, limiting therapeutic advances. Characterizing metabolic changes in patients with TLE and cognitive impairment may identify biomarkers and inform new treatment strategies. DESIGN/METHODS: We conducted a systematic review of five major databases, gathering studies published through December 2024, in accordance with PRISMA guidelines. We included all observational studies describing associations between metabolic imaging findings and cognitive measures in TLE. RESULTS: Of 1449 reports, 38 met the inclusion criteria, encompassing 1161 patients with TLE aged 5-66&#xa0;years. Twenty-two studies applied fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) to assess interictal brain glucose metabolism. Two studies utilized PET with other tracers to assess more specific metabolic aspects. Fourteen studies used proton magnetic resonance spectroscopy (1H-MRS) to quantify local concentrations of brain metabolites. Impairment of verbal memory was consistently associated with left temporal lobe metabolite changes. Non-memory cognitive impairments correlated with changes in glucose metabolism, N-acetylaspartate, and gamma-aminobutyrate in both temporal and extratemporal areas. CONCLUSION: 18F-FDG PET remains the most widely used imaging modality to assess cognitive-metabolic correlates in TLE, while other PET tracers and 1H-MRS are potentially underexplored. Verbal memory impairment correlates robustly with left temporal dysmetabolism. Cognitive impairment in TLE is multifaceted and correlates with measurable changes in metabolism in both temporal and extratemporal regions. While our synthesis was restricted by some methodological limitations, these neurometabolic signatures may hold promise as potential biomarkers for identifying risk of cognitive decline and highlight avenues for future research.

Humans

Effects of six weeks of guanidinoacetic acid supplementation with and without creatine monohydrate on cognitive function and markers of health in healthy adults.

BACKGROUND: Guanidinoacetic acid (GAA) supplementation has been reported to increase brain creatine content more effectively than creatine monohydrate (CrM). However, the effects on cognitive function are unclear. PURPOSE: The purpose of this proof-of-concept exploratory clinical trial was to determine whether GAA supplementation with and without CrM affects cognitive function and/or markers of health. METHODS: In a double-blind, randomized, and counterbalanced manner, 58 healthy and active adults (33 females, 35.5&#x2009;&#xb1;&#x2009;14 years, 76.2&#x2009;&#xb1;&#x2009;14 kg) ingested a PLA (PLA, 2 &#xd7; 6 g/d maltodextrin), GAA (2 &#xd7; 1 g/d)&#x2009;+&#x2009;PLA (2 &#xd7; 5 g/d), or GAA (2 &#xd7; 1 g/d)&#x2009;+&#x2009;CrM (2 &#xd7; 5 g/d) for six weeks. The participants donated fasting blood samples and completed a battery of tests and questionnaires assessing various aspects of function, mood, stress, sleep quality, and markers of health at baseline and after six weeks of supplementation. Data were analyzed using General Linear Model (GLM) multivariate and univariate with repeated measures, and mean changes from baseline with 95% confidence intervals, and Chi-squared analysis, and considered significant when the probability of error was 0.05 or less, and approaching significance (p&#x2009;>&#x2009;0.05-p&#x2009;<&#x2009;0.10). RESULTS: GAA supplementation tended to improve overall reaction time (-241.8&#x2009;ms [-533, 50], p&#x2009;=&#x2009;0.10) while significant interaction effects were observed in overall reaction time (p&#x2009;=&#x2009;0.031-330 ms [-629, -31]) and YES reaction time (-290&#x2009;ms [-484, -96], p&#x2009;=&#x2009;0.004) while recalled correct reaction time (-178&#x2009;ms [-374, 21], p&#x2009;=&#x2009;0.078) and recalled correct YES (7.4 % [-1, 15.8], p&#x2009;=&#x2009;0.084) approached significance compared to PLA. Limited to no effects were observed on the Delayed Picture Recognition Task Test, Digit Vigilance Task Test, Corsi Block Task Test, or Stroop Color-Word Task Test. The amount of time engaged in moderate physical activity was significantly greater (p&#x2009;<&#x2009;0.05) in the GAA group compared to PLA. Participants in the GAA group reported a lower frequency of controlling irritations (p&#x2009;=&#x2009;0.036), and feeling like difficulties are mounting (p&#x2009;=&#x2009;0.053) on the Perceived Stress Scale. Some positive and potentially undesirable effects were observed in sleep quality assessments. The quality of life assessment revealed that participants in the GAA group reported less frequent feelings of being worn out (p&#x2009;=&#x2009;0.068) and that their health was excellent (p&#x2009;=&#x2009;0.092) while those in the GAA&#x2009;+&#x2009;CrM group reported more frequent limitations when bending, kneeling, or stooping (p&#x2009;=&#x2009;0.053), more often feeling full of life (p&#x2009;=&#x2009;0.081), and less frequency in feeling downhearted and depressed (p&#x2009;=&#x2009;0.066). No clinically meaningful changes were observed in blood markers or self-reported side effects among the groups. CONCLUSION: Dietary supplementation with GAA (2 g/d) and the combination of CrM (10 g/d&#x2009;+&#x2009;GAA 2 g/d) for six weeks improved delayed verbal episodic recognition memory and retrieval speed and some measures of perceived stress, sleep quality, and quality of life. However, most cognitive tests were not affected, particularly when comparing the GAA to the PLA group; there were some inconsistencies in the findings, and several differences only approached significance. Additional research is needed before conclusions can be drawn. Clinical trial registration: ISRCTN68542582.

Humans

Updated adjunctive minocycline for schizophrenia: A systematic review and meta-analysis of clinical and cognitive outcomes.

BACKGROUND: Minocycline has been proposed as an adjunctive treatment for schizophrenia due to its anti-inflammatory and neuroprotective properties. However, evidence regarding its efficacy across clinical and cognitive outcomes remains inconsistent. METHODS: A systematic review and meta-analysis of double-blind RCTs was conducted following PRISMA guidelines. PubMed, Web of Science, Embase, Ovid MEDLINE, and the Cochrane Library were searched from January 2000 to August 2025. Eligible studies included patients with schizophrenia receiving adjunctive minocycline plus stable antipsychotics. Primary outcomes were PANSS total and subscale scores and overall cognitive performance. Secondary outcomes included SANS, CDS, CGI, GAF, and seven cognitive domains. Standardized mean differences (SMDs) with 95% CIs were calculated. RESULTS: Ten RCTs involving 895 participants were included. Adjunctive minocycline was associated with improvements in negative symptoms (PANSS negative: SMD = -0.55, 95% CI: -0.96 to -0.13; SANS: SMD = -0.75, 95% CI: -1.00 to -0.49) and overall psychopathology (PANSS total: SMD = -0.49, 95% CI: -0.80 to -0.18). Cognitive benefits were limited to a modest improvement in working memory (SMD = 0.24, 95% CI: 0.08 to 0.39), with no significant effects in other cognitive domains. Subgroup analyses suggested that illness stage, antipsychotic regimen, treatment duration, sample size, and geographic region may contribute to variability in treatment effects. Adverse event rates were comparable between groups. CONCLUSIONS: Adjunctive minocycline may improve negative symptoms and provide modest working memory benefits in schizophrenia. However, the evidence is limited by substantial heterogeneity, potential small-study effects, and inconsistent findings. Although short- to medium-term tolerability appeared comparable to placebo, larger, longer-term RCTs are needed to confirm its efficacy and safety.

Humans

Extended Long-Term Effects of Cognitive and Aerobic Training on Cognitive Function in Patients With Stress-Related Exhaustion Disorder: A 4.5-Year Follow-Up of a Randomized Controlled Trial.

Stress-related conditions like clinical burnout and exhaustion disorder (ED) are associated with enduring cognitive problems. We have previously demonstrated that the addition of computerised cognitive training (CCT) and aerobic training (AT) to a multimodal rehabilitation programme (MMR) yielded greater improvements in cognitive function compared to MMR alone in patients with ED. These effects were maintained at the 1-year follow-up for CCT, but not for AT. Building on these findings, the present study examined the extended long-term effects of CCT and AT on cognitive function, psychological health, and work ability, 4.5&#xa0;years after the interventions. Participants were recruited from a stress-rehabilitation clinic and 56 of the initial 132 participants returned for the 4.5-year follow-up. Assessments were conducted before (T1), immediately after (T2), 1-year after (T3) and 4.5-years after (T4) the interventions. Mixed model analyses assessed changes in the intervention groups relative to the control group from T1 to T4, with follow-up comparisons examining within-group stability of outcomes between T3 to T4. The primary outcome was cognitive performance on a global cognitive score. Secondary outcomes included domain-specific cognitive functioning, self-reported cognitive function, psychological health (burnout, depression, anxiety, and fatigue), and work ability. The analysis revealed sustained long-term effects on the global cognitive score, a trained updating task and episodic memory in the CCT group, with stable performance between one- and 4.5-year follow-up. The addition of AT did not yield any extended long-term effects on cognitive performance. Both groups showed extended long-term improvements in self-reported memory problems, although findings were mixed. Extended long-term improvements were observed on burnout for both groups, with additional effects on anxiety and work ability in the AT group. Notably, these effects were not present at the 1-year follow-up and are more plausibly explained by selective attrition rather than a delayed intervention effect. In conclusion, the result indicates that cognitive interventions such as CCT can have lasting positive effects on cognitive function in patients with ED, whereas the long-term psychological effects should be interpreted with caution. TRIAL REGISTRATION: ClinicalTrials.gov: NCT0073772.

Adult

Does high fructose consumption trigger microglia activation and neuroinflammation? A systematic review.

This systematic review evaluated the effects of fructose intake on neuroinflammatory markers in rodent models. The search terms Fructose AND neuroinflammation OR Neurodegeneration OR chemokines OR interleukins OR microglia OR behaviour OR memory OR cognition were used in Google Scholar, Scopus and Web of Science. Thirteen animal studies investigating fructose-induced neuroinflammation that matched the eligibility criteria were included in the study. Across the studies, 16 inflammatory markers were identified and significantly altered following exposure to fructose. The findings consistently demonstrated elevated expression of pro-inflammatory cytokines, TNF-&#x3b1;, IL-6, and IL-1&#x3b2;, following fructose administration. Fructose consumption also dysregulated MCP-1, fractalkine, and CX3CR1 levels, thereby promoting inflammatory signalling and microglial activation. Furthermore, fructose exposure significantly increased IBA-1 and CD11b, indicating sustained neuroimmune activation. Alterations in important inflammatory pathways involving TLR4, NLRP3, NF-&#x3ba;B, MyD88, iNOS, and cyclooxygenases (COX-1 and COX-2) were also observed. In contrast, expression of the anti-inflammatory regulator peroxisome proliferator-activated receptor gamma (PPAR&#x3b3;) was reduced after fructose treatment. Overall, the findings suggest that chronic fructose consumption induces neuroinflammation through multiple inflammatory and immune-related mechanisms in the brain. These effects appear to be dose- and duration-dependent and may contribute significantly to neurodegeneration and cognitive impairment.

Microglia

Effects of adjunctive memantine on executive function and global cognition in bipolar disorder (BD): A randomized, double-blind, placebo-controlled clinical trial.

BACKGROUND: Cognitive impairment contributes substantially to disability in bipolar disorder (BD), but effective pharmacologic options remain limited. This trial evaluated whether adjunctive memantine improves global cognition and executive function in BD. METHODS: In this double-blind, placebo-controlled randomized trial, patients with bipolar I disorder (B1D) receiving lithium and olanzapine were assigned to memantine or placebo. Memantine was titrated to 20&#xa0;mg/day over 6&#xa0;weeks. Cognitive outcomes were assessed at baseline, week 6, and week 18. Global cognition was measured with the Neurocognitive Assessment Battery (NuCog), and executive function with the Frontal Assessment Battery (FAB). Data were analyzed using generalized estimating equations and Bonferroni-adjusted post-hoc tests. RESULTS: Sixty-three participants were randomized (memantine, n&#xa0;=&#xa0;31; placebo, n&#xa0;=&#xa0;32), and all completed follow-up. Groups were comparable at baseline for demographic and clinical variables and for most cognitive measures. Both groups improved over time (P&#xa0;<&#xa0;0.001), but improvement was greater with memantine for global cognition at week 6 (MD&#xa0;=&#xa0;9.32; 95% CI, 4.84-13.81; P&#xa0;<&#xa0;0.001) and week 18 (MD&#xa0;=&#xa0;12.69; 95% CI, 8.67-16.71; P&#xa0;<&#xa0;0.001). FAB total scores favored memantine at week 18 (MD&#xa0;=&#xa0;2.68; 95% CI, 1.76-3.61; P&#xa0;<&#xa0;0.001), but not at week 6. Domain analyses showed significant benefits for NuCog attention, visuoconstructional ability, memory, and executive function, and for several FAB subscales by week 18. CONCLUSIONS: Adjunctive memantine improved global cognition and, over longer follow-up, executive function in BD. These findings support NMDA receptor modulation as a potential strategy for cognitive dysfunction in BD.

Humans

Comparing trajectories of cognitive functioning in treatment-resistant and non-resistant depression: a multicentre linear mixed-effects analysis.

BACKGROUND: Impaired cognitive functioning is a severe symptom in major depressive disorder (MDD). Recent evidence suggests it may be a central characteristic in its treatment resistant form (TRD), potentially constituting a clinical marker for treatment resistance and a target amenable to intervention. To date, cognitive functioning in TRD remains poorly understood and longitudinal investigations are scarce. METHODS: This observational prospective cohort study, including 320 patients diagnosed with MDD from the multicentre PROMPT study, examined differences in cognitive functioning between 118 TRD and 202 non-TRD patients over a period of twelve weeks in a real-world setting, using linear mixed modelling. Patients that failed to respond to at least two prior antidepressants trials at baseline were classified as TRD. RESULTS: TRD patients showed significantly poorer baseline performances than non-TRD patients in attention/processing speed (&#x3b2;&#xa0;=&#xa0;-0.45; 95%CI[-0.70, -0.19]; FDR-p&#xa0;=&#xa0;0.003) and verbal memory (&#x3b2;&#xa0;=&#xa0;-0.45; 95%CI[-0.72, -0.18]; FDR-p&#xa0;=&#xa0;0.003). Significant time &#xd7; group interactions were observed in motor speed and verbal fluency tasks. Post-hoc-analyses revealed stagnation in TRD patients and significant improvement in non-TRD patients. Across all other tasks improvement was observed in both groups, and random effects showed large heterogeneity between patients, indicating notable individual differences in cognitive performances. CONCLUSIONS: The results suggest distinct recovery patters between non-TRD and TRD patients, and diminished functioning in TRD patients at the domain level. However, intact and diminished performances likely occur in both groups, warranting further investigation of cognitive heterogeneity. These short-term findings highlight the need for more comprehensive longitudinal research on cognition in TRD.

Humans