Clinical tools for evaluating the severity of overactive bladder: A systematic review of psychometric properties

OBJECTIVES

To systematically evaluate the evidence describing the psychometric properties of clinical measures for assessing overactive bladder symptoms (urinary urgency with or without urge urinary incontinence, urinary frequency and nocturia). To evaluate the quality of this evidence-base using the COnsensus-based Standards for selecting health status Measurement INstruments (COSMIN) checklist and the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tools.

DATA SOURCES

Five electronic databases (CINAHL, EMBASE, MEDLINE, Scopus and Web of Science) were searched from dataset inception to August 2023.

REVIEW METHODS

Study screening, data extraction and quality appraisal were performed by two independent authors. Inclusion criteria were studies testing one or more psychometric properties of clinical tools for the assessment of overactive bladder symptoms among adults aged 18 years and older for both sexes. The methodological quality and quality of the evidence were evaluated using the COSMIN checklist and GRADE tools, respectively.

RESULTS

The search identified 40 studies totalling 10,634 participants evaluating the psychometric properties of 15 clinical tools. The COSMIN methodological quality was rated good for most measures, and the GRADE quality of evidence ranged from low (13%) to high (33%). The Overactive Bladder Symptom Score, Overactive Bladder Questionnaire and Neurogenic Bladder Symptom Score were of good methodological and high-GRADE evidence qualities.

CONCLUSION

Overactive Bladder Symptom Score, the Overactive Bladder Questionnaire and the Neurogenic Bladder Symptoms Score are promising psychometrically sound measures. The Overactive Bladder Symptom Score has been applied to the most culturally diverse populations supported by studies of good methodological and high-GRADE evidence quality.

Instantaneous effects of prefrontal transcranial magnetic stimulation on brain oxygenation: A systematic review

This systematic review investigates how prefrontal transcranial magnetic stimulation (TMS) immediately influences neuronal excitability based on oxygenation changes measured by functional magnetic resonance imaging (fMRI) or functional near-infrared spectroscopy (fNIRS). A thorough understanding of TMS-induced excitability changes may enable clinicians to adjust TMS parameters and optimize treatment plans proactively. Five databases were searched for human studies evaluating brain excitability using concurrent TMS/fMRI or TMS/fNIRS. Thirty-seven studies (13 concurrent TMS/fNIRS studies, 24 concurrent TMS/fMRI studies) were included in a qualitative synthesis. Despite methodological inconsistencies, a distinct pattern of activated nodes in the frontoparietal central executive network, the cingulo-opercular salience network, and the default-mode network emerged. The activated nodes included the prefrontal cortex (particularly dorsolateral prefrontal cortex), insula cortex, striatal regions (especially caudate, putamen), anterior cingulate cortex, and thalamus. High-frequency repetitive TMS most consistently induced expected facilitatory effects in these brain regions. However, varied stimulation parameters (e.g., intensity, coil orientation, target sites) and the inter- and intra-individual variability of brain state contribute to the observed heterogeneity of target excitability and co-activated regions. Given the considerable methodological and individual variability across the limited evidence, conclusions should be drawn with caution.

Sex differences in brain excitability revealed by concurrent iTBS/fNIRS

Sex differences have been claimed an imperative factor in the optimization of psychiatric treatments. Intermittent theta-burst stimulation (iTBS), a patterned form of repetitive transcranial magnetic stimulation, is a promising non-invasive treatment option. Here, we investigated whether the real-time neural response to iTBS differs between men and women, and which mechanisms may mediate these differences. To this end, we capitalized on a concurrent iTBS/functional near-infrared spectroscopy setup over the left dorsolateral prefrontal cortex, a common clinical target, to test our assumptions. In a series of experiments, we show (1) a biological sex difference in absolute hemoglobin concentrations in the left dorsolateral prefrontal cortex in healthy participants; (2) that this sex difference is amplified by iTBS but not by cognitive tasks; and (3) that the sex difference amplified by iTBS is modulated by stimulation intensity. These results inform future stimulation treatment optimizations towards precision psychiatry.

Gender Dysphoria and Sexual Euphoria: A Bayesian Perspective on the Influence of Gender-Affirming Hormone Therapy on Sexual Arousal

Self-reported sexual orientation of transgender individuals occasionally changes over transition. Using functional magnetic resonance imaging, we tested the hypothesis that neural and behavioral patterns of sexual arousal in transgender individuals would shift from the assigned to the experienced gender (e.g., trans women's responses becoming more dissimilar to those of cis men and more similar to those of cis women). To this aim, trans women (N = 12) and trans men (N = 20) as well as cisgender women (N = 24) and cisgender men (N = 14) rated visual stimuli showing male-female, female-female or male-male intercourse for sexual arousal before and after four months of gender-affirming hormone therapy. A Bayesian framework allowed us to incorporate previous behavioral findings. The hypothesized changes could indeed be observed in the behavioral responses with the strongest results for trans men and female-female scenes. Activation of the ventral striatum supported our hypothesis only for female-female scenes in trans women. The respective application or depletion of androgens in trans men and trans women might partly explain this observation. The prominent role of female-female stimuli might be based on the differential responses they elicit in cis women and men or, in theory, the controversial concept of autogynephilia. We show that correlates of sexual arousal in transgender individuals might change in the direction of the experienced gender. Future investigations should elucidate the mechanistic role of sex hormones and the cause of the differential neural and behavioral findings.The study was registered at ClinicalTrials.gov (NCT02715232), March 22, 2016.

Measures of quality of life of people with neurogenic overactive bladder: A systematic review of psychometric properties

OBJECTIVE

To identify psychometrically robust quality-of-life (QOL) outcome measures for evaluating QOL among people with neurogenic overactive bladder (OAB).

STUDY DESIGN

Electronic databases (CINAHL, EMBASE, MEDLINE, Scopus and Web of Science) were searched from inception to January 2023. Two independent reviewers participated in study screening, data extraction and quality appraisal. Studies were included if they validated at least one psychometric property of a QOL outcome measure among adults (age ≥ 18 years) with neurogenic OAB. The COnsensus-based Standards for selecting health status Measurement INstruments (COSMIN) checklist and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool were used to evaluate the methodological quality and quality of evidence, respectively, for each included study.

RESULTS

Database searches identified 47 studies that tested the psychometric properties of 15 QOL measures in a total of 19,994 participants with stroke, spinal cord injury, Parkinson's disease or multiple sclerosis. The Incontinence Quality of Life Questionnaire (I-QOL), King's Health Questionnaire, Overactive Bladder Questionnaire and Qualiveen were the best validated measures, with strong reliability, validity and responsiveness. I-QOL was the most robust, cross-culturally administered and psychometrically strong measure. The COSMIN checklist indicated sufficient methodological quality for 70% of measures, and the modified GRADE tool indicated quality of evidence ranging from moderate (67%) to high (33%).

CONCLUSIONS

This review identified the I-QOL as a culturally diverse measure with robust reliability, validity and responsiveness for assessing QOL among people with neurogenic OAB. These findings are supported by studies with good methodological quality (COSMIN) and high-quality evidence (GRADE).

The effectiveness and safety of low-intensity transcranial ultrasound stimulation: A systematic review of human and animal studies

Low-intensity transcranial ultrasound stimulation (LITUS) is a novel non-invasive neuromodulation technique. We conducted a systematic review to evaluate current evidence on the efficacy and safety of LITUS neuromodulation. Five databases were searched from inception to May 31, 2023. Randomized controlled human trials and controlled animal studies were included. The neuromodulation effects of LITUS on clinical or pre-clinical, neurophysiological, neuroimaging, histological and biochemical outcomes, and adverse events were summarized. In total, 11 human studies and 44 animal studies were identified. LITUS demonstrated therapeutic efficacy in neurological disorders, psychiatric disorders, pain, sleep disorders and hypertension. LITUS-related changes in neuronal structure and cortical activity were found. From histological and biochemical perspectives, prominent findings included suppressing the inflammatory response and facilitating neurogenesis. No adverse effects were reported in controlled animal studies included in our review, while reversible headache, nausea, and vomiting were reported in a few human subjects. Overall, LITUS alleviates various symptoms and modulates associated brain circuits without major side effects. Future research needs to establish a solid therapeutic framework for LITUS.

Efficacy of scalp stimulation for multidomain cognitive impairment in patients with post-stroke cognitive impairment and dementia: A network meta-analysis and meta-regression of moderators

BACKGROUND

Scalp stimulation has gained more traction for post-stroke cognitive impairment and dementia (PSCID); the interaction between stimulation targets and parameters influences the response to the stimulation. However, the most efficacious treatment for improving different domains of cognitive impairment remains unknown.

OBJECTIVE

We aimed to conduct a systematic review and network meta-analysis (NMA) to compare the efficacy of various scalp stimulation protocols used in PSCID treatment.

METHODS

Randomized controlled trials of scalp stimulation in patients with PSCID were searched in eight databases over the past 20 years. Standardized mean differences (SMDs) for global and subdomain cognitive scores were pooled in Bayesian NMA. Moderators were examined using meta-regression analysis.

RESULTS

A total of 90 trials, with 6199 patients, were included. Low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected dorsolateral prefrontal cortex (DLPFC) was highly suggested for alleviating global severity (SMD = 1.11, 95% CI (0.64, 1.57)). High-frequency rTMS over the left DLPFC was recommended for language use (1.85 (1.18, 2.52)), executive function (0.85 (0.36, 1.33)), orientation deficits (0.59 (0.07, 1.13)), and attention (0.85 (0.27, 1.43)). Anodal transcranial direct current stimulation over the affected DLPFC (2.03 (0.72, 3.34)) was recommended for treating memory impairment. Meta-regression analyses showed significant associations within attention, language and orientation.

CONCLUSION

Overall, different cognitive domains have different optimal scalp stimulation prescriptions, and activating the affected key brain regions and inhibiting the unaffected area is still the most effective treatment.

Changes to hypothalamic volume and associated subunits during gender-affirming hormone therapy

BACKGROUND

Among its pleiotropic properties, gender-affirming hormone therapy (GHT) affects regional brain volumes. The hypothalamus, which regulates neuroendocrine function and associated emotional and cognitive processes, is an intuitive target for probing GHT effects. We sought to assess changes to hypothalamus and hypothalamic subunit volumes after GHT, thereby honouring the region's anatomical and functional heterogeneity.

METHODS

Individuals with gender dysphoria and cisgender controls underwent 2 MRI measurements, with a median interval of 145 days (interquartile range [IQR] 128.25-169.75 d, mean 164.94 d) between the first and second MRI. Transgender women (TW) and transgender men (TM) underwent the first MRI before GHT and the second MRI after approximately 4.5 months of GHT, which comprised estrogen and anti-androgen therapy in TW or testosterone therapy in TM. Hypothalamic volumes were segmented using FreeSurfer, and effects of GHT were tested using repeated-measures analysis of covariance.

RESULTS

The final sample included 106 participants: 38 TM, 15 TW, 32 cisgender women (CW) and 21 cisgender men (CM). Our analyses revealed group × time interaction effects for total, left and right hypothalamus volume, and for several subunits (left and right inferior tubular, left superior tubular, right anterior inferior, right anterior superior, all p corr < 0.01). In TW, volumes decreased between the first and second MRI in these regions (all p corr ≤ 0.01), and the change from the first to second MRI in TW differed significantly from that in CM and CW in several subunits (p corr < 0.05).

LIMITATIONS

We did not address the influence of transition-related psychological and behavioural changes.

CONCLUSION

Our results suggest a subunit-specific effect of GHT on hypothalamus volumes in TW. This finding is in accordance with previous reports of positive and negative effects of androgens and estrogens, respectively, on cerebral volumes.

The influence of sex steroid treatment on insular connectivity in gender dysphoria

BACKGROUND

Sex-specific differences in brain connectivity were found in various neuroimaging studies, though little is known about sex steroid effects on insular functioning. Based on well-characterized sex differences in emotion regulation, interoception and higher-level cognition, gender-dysphoric individuals receiving gender-affirming hormone therapy represent an interesting cohort to investigate how sex hormones might influence insular connectivity and related brain functions.

METHODS

To analyze the potential effect of sex steroids on insular connectivity at rest, 11 transgender women, 14 transgender men, 20 cisgender women, and 11 cisgender men were recruited. All participants underwent two magnetic resonance imaging sessions involving resting-state acquisitions separated by a median time period of 4.5 months and also completed the Bermond-Vorst alexithymia questionnaire at the initial and final examination. Between scans, transgender subjects received gender-affirming hormone therapy.

RESULTS

A seed based functional connectivity analysis revealed a significant 2-way interaction effect of group-by-time between right insula, cingulum, left middle frontal gyrus and left angular gyrus. Post-hoc tests demonstrated an increase in connectivity for transgender women when compared to cisgender men. Furthermore, spectral dynamic causal modelling showed reduced effective connectivity from the posterior cingulum and left angular gyrus to the left middle frontal gyrus as well as from the right insula to the left middle frontal gyrus. Alexithymia changes were found after gender-affirming hormone therapy for transgender women in both fantasizing and identifying.

CONCLUSION

These findings suggest a considerable influence of estrogen administration and androgen suppression on brain networks implicated in interoception, own-body perception and higher-level cognition.

Leveraging the glymphatic and meningeal lymphatic systems as therapeutic strategies in Alzheimer's disease: an updated overview of nonpharmacological therapies

Understanding and treating Alzheimer's disease (AD) has been a remarkable challenge for both scientists and physicians. Although the amyloid-beta and tau protein hypothesis have largely explained the key pathological features of the disease, the mechanisms by which such proteins accumulate and lead to disease progression are still unknown. Such lack of understanding disrupts the development of disease-modifying interventions, leaving a therapeutic gap that remains unsolved. Nonetheless, the recent discoveries of the glymphatic pathway and the meningeal lymphatic system as key components driving central solute clearance revealed another mechanism underlying AD pathogenesis. In this regard, this narrative review integrates the glymphatic and meningeal lymphatic systems as essential components involved in AD pathogenesis. Moreover, it discusses the emerging evidence suggesting that nutritional supplementation, non-invasive brain stimulation, and traditional Chinese medicine can improve the pathophysiology of the disease by increasing glymphatic and/or meningeal lymphatic function. Given that physical exercise is a well-regarded preventive and pro-cognitive intervention for dementia, we summarize the evidence suggesting the glymphatic system as a mediating mechanism of the physical exercise therapeutic effects in AD. Targeting these central solute clearance systems holds the promise of more effective treatment strategies.

Effects of repetitive transcranial magnetic stimulation of the left dorsolateral prefrontal cortex on symptom domains in neuropsychiatric disorders: a systematic review and cross-diagnostic meta-analysis

BACKGROUND

The left dorsolateral prefrontal cortex is a prime target for repetitive transcranial magnetic stimulation (TMS) to treat neuropsychiatric disorders; thus, abundant efficacy data from controlled trials are available. A cross-diagnostic meta-analysis was conducted to identify the symptom domains susceptible to repetitive TMS to the left dorsolateral prefrontal cortex.

METHODS

This systematic review and meta-analysis investigated the effects of repetitive TMS to the left dorsolateral prefrontal cortex on neuropsychiatric symptoms presenting across diagnoses. We searched PubMed, MEDLINE, Embase, Web of Science, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform for randomised and sham controlled trials published from inception to Aug 17, 2022. Included studies assessed symptoms using clinical measures and reported sufficient data to calculate effect sizes pooled with a random effects model. Two independent reviewers conducted screening and used the Cochrane risk-of-bias tool for quality assessment. Summary data were extracted from published reports. The main outcome was the therapeutic effects of repetitive TMS of the left dorsolateral prefrontal cortex on distinct symptom domains. This study is registered with PROSPERO (CRD42021278458).

FINDINGS

Of 9056 studies identified (6704 from databases and 2352 from registers), 174 were included in the analysis including 7905 patients. 163 of 174 studies reported gender data; 3908 (52·35%) of 7465 patients were male individuals, and 3557 (47·65%) were female individuals. Mean age was 44·63 years (range 19·79-72·80). Ethnicity data were mostly not available. Effect size was large for craving (Hedges'g -0·803 [95% CI -1·099 to -0·507], p<0·0001; I²=82·40%), medium for depressive symptoms (-0·725 [-0·889 to -0·561], p<0·0001; I²=85·66%), small for anxiety, obsessions or compulsions, pain, global cognition, declarative memory, working memory, cognitive control, and motor coordination (Hedges'g -0·198 to -0·491), and non-significant for attention, suicidal ideation, language, walking ability, fatigue, and sleep.

INTERPRETATION

The cross-diagnostic meta-analysis shows the efficacy of repetitive TMS of the left dorsolateral prefrontal cortex on distinct symptom domains, providing a novel framework for assessing target or efficacy interactions of repetitive TMS, and informing personalised applications for conditions for which regular trials are uninformative.

FUNDING

The University Grants Committee of Hong Kong and the Mental Health Research Center, The Hong Kong Polytechnic University.

Effects of bilateral sequential theta-burst stimulation on functional connectivity in treatment-resistant depression: First results

BACKGROUND

Previous studies suggest that transcranial magnetic stimulation exerts antidepressant effects by altering functional connectivity (FC). However, knowledge about this mechanism is still limited. Here, we aimed to investigate the effect of bilateral sequential theta-burst stimulation (TBS) on FC in treatment-resistant depression (TRD) in a sham-controlled longitudinal study.

METHODS

TRD patients (n = 20) underwent a three-week treatment of intermittent TBS of the left and continuous TBS of the right dorsolateral prefrontal cortex (DLPFC). Upon this trial's premature termination, 15 patients had received active TBS and five patients sham stimulation. Resting-state functional magnetic resonance imaging was performed at baseline and after treatment. FC (left and right DLPFC) was estimated for each participant, followed by group statistics (t-tests). Furthermore, depression scores were analyzed (linear mixed models analysis) and tested for correlation with FC.

RESULTS

Both groups exhibited reductions of depression scores, however, there was no significant main effect of group, or group and time. Anticorrelations between DLPFC and the subgenual cingulate cortex (sgACC) were observed for baseline FC, corresponding to changes in depression severity. Treatment did not significantly change DLPFC-sgACC connectivity, but significantly reduced FC between the left stimulation target and bilateral anterior insula.

CONCLUSIONS

Our data is compatible with previous reports on the relevance of anticorrelation between DLPFC and sgACC for treatment success. Furthermore, FC changes between left DLPFC and bilateral anterior insula highlight the effect of TBS on the salience network.

LIMITATIONS

Due to the limited sample size, results should be interpreted with caution and are of exploratory nature.

Corrigendum: Modulations of static and dynamic functional connectivity among brain networks by electroacupuncture in post-stroke aphasia

[This corrects the article DOI: 10.3389/fneur.2022.956931.].

Effects of bilateral sequential theta-burst stimulation on 5-HT1A receptors in the dorsolateral prefrontal cortex in treatment-resistant depression: a proof-of-concept trial

Theta-burst stimulation (TBS) represents a brain stimulation technique effective for treatment-resistant depression (TRD) as underlined by meta-analyses. While the methodology undergoes constant refinement, bilateral stimulation of the dorsolateral prefrontal cortex (DLPFC) appears promising to restore left DLPFC hypoactivity and right hyperactivity found in depression. The post-synaptic inhibitory serotonin-1A (5-HT1A) receptor, also occurring in the DLPFC, might be involved in this mechanism of action. To test this hypothesis, we performed PET-imaging using the tracer [carbonyl-11C]WAY-100635 including arterial blood sampling before and after a three-week treatment with TBS in 11 TRD patients compared to sham stimulation (n = 8 and n = 3, respectively). Treatment groups were randomly assigned, and TBS protocol consisted of excitatory intermittent TBS to the left and inhibitory continuous TBS to the right DLPFC. A linear mixed model including group, hemisphere, time, and Hamilton Rating Scale for Depression (HAMD) score revealed a 3-way interaction effect of group, time, and HAMD on specific distribution volume (VS) of 5-HT1A receptor. While post-hoc comparisons showed no significant changes of 5-HT1A receptor VS in either group, higher 5-HT1A receptor VS after treatment correlated with greater difference in HAMD (r = -0.62). The results of this proof-of-concept trial hint towards potential effects of TBS on the distribution of the 5-HT1A receptor. Due to the small sample size, all results must, however, be regarded with caution.

Modulations of static and dynamic functional connectivity among brain networks by electroacupuncture in post-stroke aphasia

Introduction

Post-stroke aphasia (PSA) is a language disorder caused by left hemisphere stroke. Electroacupuncture (EA) is a minimally invasive therapeutic option for PSA treatment. Tongli (HT5) and Xuanzhong (GB39), two important language-associated acupoints, are frequently used in the rehabilitation of patients with PSA. Preliminary evidence indicated functional activation in distributed cortical areas upon HT5 and GB39 stimulation. However, research on the modulation of dynamic and static functional connectivity (FC) in the brain by EA in PSA is lacking.

Method

This study aimed to investigate the PSA-related effects of EA stimulation at HT5 and GB39 on neural processing. Thirty-five participants were recruited, including 19 patients with PSA and 16 healthy controls (HCs). The BOLD signal was analyzed by static independent component analysis, generalized psychophysiological interactions, and dynamic independent component analysis, considering variables such as age, sex, and years of education.

Results

The results revealed that PSA showed activated clusters in the left putamen, left postcentral gyrus (PostCG), and left angular gyrus in the salience network (SN) compared to the HC group. The interaction effect on temporal properties of networks showed higher variability of SN (F = 2.23, positive false discovery rate [pFDR] = 0.017). The interaction effect on static FC showed increased functional coupling between the right calcarine and right lingual gyrus (F = 3.16, pFDR = 0.043). For the dynamic FC, at the region level, the interaction effect showed lower variability and higher frequencies of circuit 3, with the strongest connections between the supramarginal gyrus and posterior cingulum (F = 5.42, pFDR = 0.03), middle cingulum and PostCG (F = 5.27, pFDR = 0.036), and triangle inferior frontal and lingual gyrus (F = 5.57, pFDR = 0.026). At the network level, the interaction effect showed higher variability in occipital network-language network (LN) and cerebellar network (CN) coupling, with stronger connections between the LN and CN (F = 4.29, pFDR = 0.042). Dynamic FC values between the triangle inferior frontal and lingual gyri were anticorrelated with transcribing, describing, and dictating scores in the Chinese Rehabilitation Research Center for Chinese Standard Aphasia Examination.

Discussion

These findings suggest that EA stimulation may improve language function, as it significantly modulated the nodes of regions/networks involved in the LN, SN, CN, occipital cortex, somatosensory regions, and cerebral limbic system.

Potential mechanisms underlying the accelerated cognitive decline in people with chronic low back pain: A scoping review

A growing body of evidence has shown that people with chronic low back pain (CLBP) demonstrate significantly greater declines in multiple cognitive domains than people who do not have CLBP. Given the high prevalence of CLBP in the ever-growing aging population that may be more vulnerable to cognitive decline, it is important to understand the mechanisms underlying the accelerated cognitive decline observed in this population, so that proper preventive or treatment approaches can be developed and implemented. The current scoping review summarizes what is known regarding the potential mechanisms underlying suboptimal cognitive performance and cognitive decline in people with CLBP and discusses future research directions. Five potential mechanisms were identified based on the findings from 34 included studies: (1) altered activity in the cortex and neural networks; (2) grey matter atrophy; (3) microglial activation and neuroinflammation; (4) comorbidities associated with CLBP; and (5) gut microbiota dysbiosis. Future studies should deepen the understanding of mechanisms underlying this association so that proper prevention and treatment strategies can be developed.

Non-Invasive Brain Stimulation Effects on Biomarkers of Tryptophan Metabolism: A Scoping Review and Meta-Analysis

Abnormal activation of the kynurenine and serotonin pathways of tryptophan metabolism is linked to a host of neuropsychiatric disorders. Concurrently, noninvasive brain stimulation (NIBS) techniques demonstrate high therapeutic efficacy across neuropsychiatric disorders, with indications for modulated neuroplasticity underlying such effects. We therefore conducted a scoping review with meta-analysis of eligible studies, conforming with the PRISMA statement, by searching the PubMed and Web of Science databases for clinical and preclinical studies that report the effects of NIBS on biomarkers of tryptophan metabolism. NIBS techniques reviewed were electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS). Of the 564 search results, 65 studies were included with publications dating back to 1971 until 2022. The Robust Bayesian Meta-Analysis on clinical studies and qualitative analysis identified general null effects by NIBS on biomarkers of tryptophan metabolism, but moderate evidence for TMS effects on elevating serum serotonin levels. We cannot interpret this as evidence for or against the effects of NIBS on these biomarkers, as there exists several confounding methodological differences in this literature. Future controlled studies are needed to elucidate the effects of NIBS on biomarkers of tryptophan metabolism, an under-investigated question with substantial implications to clinical research and practice.

Functional network characteristics based on EEG of patients in acute ischemic stroke: A pilot study

BACKGROUND

Ischemic stroke is a common type of stroke associated with reorganization of functional network of the brain.

OBJECTIVE

This pilot study aimed to investigate the characteristics of functional brain networks based on EEG in patients with acute ischemic stroke.

METHODS

Seven patients with ischemic stroke within 72 hours of onset and seven healthy controls were enrolled in the study. Dynamic EEG monitoring and clinical information were repeatedly collected within 72 hours (T1), on the 5th day (T2), and on the 7th day (T3) of stroke onset. A directed transfer function was employed to construct functional brain connection patterns. Graph theoretical analysis was performed to evaluate the characteristics of functional brain networks.

RESULTS

First, we found that the brain networks of ischemic stroke patients were quite different from the healthy controls. The clustering coefficient (0.001 <  Threshold <  0.2) in Delta, Theta, and Alpha bands for the patients were significantly lower (P <  0.01) and the shortest path length in all bands (0.001 <  Threshold <  0.2) for the patients were significantly longer (P <  0.01). Moreover, the peaks of the shortest path length for the patients seemed to be higher in all bands with larger thresholds. Secondly, the brain networks for the patients showed a characterized time-variation pattern. The clustering coefficient (0.001 <  Threshold <  0.2) of T1 was higher than that of T2 in alpha band (P <  0.01). The shortest path length (0.001 <  Threshold <  0.2) of T3 was shorter than that of T2 (P <  0.01) in all bands, and the peak of T3 was numerically higher than that of T2 in all bands with narrower thresholds.

CONCLUSION

Functional brain networks in patients with acute ischemic stroke showed impaired global functional integration and decreased efficiency of information transmission compared with healthy subjects. The shortening of the shortest path length during the recovery indicates neural plasticity and reorganization.

The Impact of Theta-Burst Stimulation on Cortical GABA and Glutamate in Treatment-Resistant Depression: A Surface-Based MRSI Analysis Approach

Background: Theta burst stimulation (TBS) belongs to one of the biological antidepressant treatment options. When applied bilaterally, excitatory intermittent TBS (iTBS) is commonly targeted to the left and inhibitory continuous TBS (cTBS) to the right dorsolateral prefrontal cortex. TBS was shown to influence neurotransmitter systems, while iTBS is thought to interfere with glutamatergic circuits and cTBS to mediate GABAergic neurotransmission.

Objectives: We aimed to expand insights into the therapeutic effects of TBS on the GABAergic and glutamatergic system utilizing 3D-multivoxel magnetic resonance spectroscopy imaging (MRSI) in combination with a novel surface-based MRSI analysis approach to investigate changes of cortical neurotransmitter levels in patients with treatment-resistant depression (TRD).

Methods: Twelve TRD patients (five females, mean age ± SD = 35 ± 11 years) completed paired MRSI measurements, using a GABA-edited 3D-multivoxel MEGA-LASER sequence, before and after 3 weeks of bilateral TBS treatment. Changes in cortical distributions of GABA+/tNAA (GABA+macromolecules relative to total N-acetylaspartate) and Glx/tNAA (Glx = mixed signal of glutamate and glutamine), were investigated in a surface-based region-of-interest (ROI) analysis approach.

Results: ANCOVAs revealed a significant increase in Glx/tNAA ratios in the left caudal middle frontal area (p_corr. = 0.046, F = 13.292), an area targeted by iTBS treatment. Whereas, contralateral treatment with cTBS evoked no alterations in glutamate or GABA concentrations.

Conclusion: This study demonstrates surface-based adaptions in the stimulation area to the glutamate metabolism after excitatory iTBS but not after cTBS, using a novel surface-based analysis of 3D-MRSI data. The reported impact of facilitatory iTBS on glutamatergic neurotransmission provides further insight into the neurobiological effects of TBS in TRD.

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals. Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus). Linear mixed models analysis revealed a significant measurement by gender identity effect (p_corr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (p_corr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men. Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. DATA AVAILABILITY STATEMENT: Due to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

Effects of Transcranial Pulse Stimulation (TPS) on Young Adults With Symptom of Depression: A Pilot Randomised Controlled Trial Protocol

Background

Since the emergence of the COVID-19 pandemic, there have been lots of published work examining the association between COVID-19 and mental health, particularly, anxiety and depression in the general populations and disease subpopulations globally. Depression is a debilitating disorder affecting individuals' level of bio-psychological-social functioning across different age groups. Since almost all studies were cross-sectional studies, there seems to be a lack of robust, large-scale, and technological-based interventional studies to restore the general public's optimal psychosocial wellbeing amidst the COVID-19 pandemic. Transcranial pulse stimulation (TPS) is a relatively new non-intrusive brain stimulation (NIBS) technology, and only a paucity of studies was conducted related to the TPS treatment on older adults with mild neurocognitive disorders. However, there is by far no study conducted on young adults with major depressive disorder nationwide. This gives us the impetus to execute the first nationwide study evaluating the efficacy of TPS on the treatment of depression among young adults in Hong Kong.

Methods

This study proposes a two-armed single-blinded randomised controlled trial including TPS as an intervention group and a waitlist control group. Both groups will be measured at baseline (T1), immediately after the intervention (T2), and at the 3- month follow-up (T3).

Recruitment

A total of 30 community-dwelling subjects who are aged 18 and above and diagnosed with major depressive disorder (MDD) will be recruited in this study. All subjects will be computer randomised into either the intervention group or the waitlist control group, balanced by gender and age on a 1:1 ratio.

Intervention

All subjects in each group will have to undertake functional MRI (fMRI) before and after six 30-min TPS sessions, which will be completed in 2 weeks' time.

Outcomes

Baseline measurements and post-TPS evaluation of the psychological outcomes (i.e., depression, cognition, anhedonia, and instrumental activities of daily living) will also be conducted on all participants. A 3-month follow-up period will be usedto assess the long-term sustainability of the TPS intervention. For statistical analysis, ANOVA with repeated measures will be used to analyse data. Missing data were managed by multiple mutations. The level of significance will be set to p < 0.05.

Significance of the Study

Results of this study will be used to inform health policy to determine whether TPS could be considered as a top treatment option for MDD.

Clinical Trial Registration

ClinicalTrials.gov, identifier: NCT05006365.

Central Adiponectin Signaling – A Metabolic Regulator in Support of Brain Plasticity

Brain plasticity and metabolism are tightly connected by a constant influx of peripheral glucose to the central nervous system in order to meet the high metabolic demands imposed by neuronal activity. Metabolic disturbances highly affect neuronal plasticity, which underlies the prevalent comorbidity between metabolic disorders, cognitive impairment, and mood dysfunction. Effective pro-cognitive and neuropsychiatric interventions, therefore, should consider the metabolic aspect of brain plasticity to achieve high effectiveness. The adipocyte-secreted hormone, adiponectin, is a metabolic regulator that crosses the blood-brain barrier and modulates neuronal activity in several brain regions, where it exerts neurotrophic and neuroprotective properties. Moreover, adiponectin has been shown to improve neuronal metabolism in different animal models, including obesity, diabetes, and Alzheimer’s disease. Here, we aim at linking the adiponectin’s neurotrophic and neuroprotective properties with its main role as a metabolic regulator and to summarize the possible mechanisms of action on improving brain plasticity via its role in regulating the intracellular energetic activity. Such properties suggest adiponectin signaling as a potential target to counteract the central metabolic disturbances and impaired neuronal plasticity underlying many neuropsychiatric disorders.

Effects of nonsurgical, minimally or noninvasive therapies for urinary incontinence due to neurogenic bladder: a systematic review and meta-analysis

Objective:

To determine the effects of nonsurgical, minimally or noninvasive therapies on urge urinary incontinence (UUI) symptoms and quality of life (QoL) in individuals with neurogenic bladder (NGB).

Data Sources:

Cochrane library, EMBASE, MEDLINE, PEDro, Scopus, and Web of Science databases were searched from inception to September 2021.

Review Methods:

Randomized controlled trials that compared therapies such as intravaginal electrical stimulation (IVES), transcutaneous electrical nerve stimulation (TENS), neuromuscular electrical stimulation (NMES), transcutaneous tibial nerve stimulation (TTNS), pelvic floor muscle training (PFMT), and behavioural therapy (BT) to control were included. Study screening, data extraction, and study quality assessments were performed by two independent authors.

Results:

Fourteen trials with 804 participants were included in the study after screening of 4281 potentially relevant articles. Meta-analyses revealed a significant effect of electrical stimulation on UUI due to multiple sclerosis (standardized mean difference (SMD): −0.614; 95% confidence interval (CI): −1.023, −0.206; p = 0.003) and stroke (SMD: −2.639; 95% CI: −3.804, −1.474; p = 0.000). The pooled analyses of TTNS (weighted mean difference (WMD): −12.406; 95% CI: −16.015, −8.797; p = 0.000) and BT (WMD: −9.117; 95% CI: −14.746, −3.487; p = 0.002) revealed significant effects of these interventions on QoL in people with Parkinson’s disease. However, meta-analyses revealed nonsignificant effects for PFMT (WMD: −0.751; 95% CI: −2.426, 0.924; p = 0.380) and BT (WMD: −0.597; 95% CI: −1.278, 0.083; p = 0.085) on UUI due to Parkinson’s disease.

Conclusions:

Our meta-analyses found electrical stimulation to be beneficial for improving the symptoms of UUI among people with multiple sclerosis and those with stroke. Our review also revealed that TTNS and BT might improve QoL for people with NGB due to Parkinson’s disease, although the effects of PFMT and BT on UUI warrant further investigation.

Protocol for a prospective open-label clinical trial to investigate the utility of concurrent TBS/fNIRS for antidepressant treatment optimisation

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) with theta burst stimulation (i.e. TBS) of the dorsolateral prefrontal cortex (DLPFC) is an innovative treatment for major depressive disorder (MDD). However, fewer than 50% of patients show sufficient response to this treatment; markers for response prediction are urgently needed. Research shows considerable individual variability in the brain responses to rTMS. However, whether differences in individual DLPFC modulation by rTMS can be used as a predictive marker for treatment response remains to be investigated. Here, we present a research programme that will exploit the combination of functional near-infrared spectroscopy (fNIRS) with brain stimulation. Concurrent TBS/fNIRS will allow us to systematically investigate TBS-induced modulation of blood oxygenation as a proxy for induced brain activity changes. The findings from this study will (1) elucidate the immediate effects of excitatory and inhibitory TBS on prefrontal activity in TBS treatment-naïve patients with MDD and (2) validate the potential utility of TBS-induced brain modulation at baseline for the prediction of antidepressant response to 4 weeks of daily TBS treatment.

METHODS AND ANALYSIS

Open-label, parallel-group experiment consisting of two parts. In part 1, 70 patients and 37 healthy controls will be subjected to concurrent TBS/fNIRS. Intermittent TBS (iTBS) and continuous TBS (cTBS) will be applied on the left and right DLPFC, respectively. fNIRS data will be acquired before, during and several minutes after stimulation. In part 2, patients who participated in part 1 will receive a 4 week iTBS treatment of the left DLPFC, performed daily for 5 days per week. Psychometric evaluation will be performed periodically and at 1 month treatment follow-up. Statistical analysis will include a conventional, as well as a machine learning approach.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Institutional Review Board. Findings will be disseminated through scientific journals, conferences and university courses.

TRIAL REGISTRATION NUMBER

NCT04526002.

Effects of non-invasive brain stimulation in multiple sclerosis: systematic review and meta-analysis

Objective:

The objective of this meta-analysis was to summarize evidence on the therapeutic effects of non-invasive brain stimulation (NIBS) on core symptoms of multiple sclerosis (MS). Specifically, findings from studies deploying transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) protocols were summarized in this review.

Methods:

We systematically searched articles published in four databases, until 31 May 2021, which compared the effects of active tDCS or rTMS with sham intervention in MS patients. We used a random-effects model for this meta-analysis. Meta-regression and subgroup meta-analysis were used to examine the effects of stimulation dose and different stimulation protocols, respectively.

Results:

Twenty-five randomized controlled trials (RCTs) were included in this review, consisting of 19 tDCS and 6 rTMS studies. tDCS led to a significant and immediate reduction of fatigue with a large effect size (Hedges’s g = −0.870, 95% confidence intervals (CI) = [−1.225 to −0.458], number needed to treat (NNT) = 2). Particularly, a subgroup analysis showed that applying tDCS over the left DLPFC and bilateral S1 led to fatigue reductions compared to sham stimulation. Furthermore, tDCS had favorable effects on fatigue in MS patients with low physical disability but not those with high physical disability, and additionally improved cognitive function. Finally, whereas rTMS was observed to reduce muscle spasticity, these NIBS protocols showed no further effect on MS-associated pain and mood symptoms.

Conclusion:

tDCS in MS alleviates fatigue and improves cognitive function whereas rTMS reduces muscle spasticity. More high-quality studies are needed to substantiate the therapeutic effects of different NIBS protocols in MS.

Dose-response relationship between iTBS and prefrontal activation during executive functioning: A fNIRS study

INTRODUCTION

Intermittent theta-burst stimulation (iTBS) is a non-invasive brain stimulation paradigm that has demonstrated promising therapeutic benefits for a variety of neuropsychiatric disorders. It has recently garnered widespread favor among researchers and clinicians, owing to its comparable potentiation effects as conventional high-frequency repetitive transcranial magnetic stimulation (rTMS), but administered in a much shorter time frame. However, there is still a lack of agreement over the optimal stimulation intensity, particularly when targeting the prefrontal regions. The objective of this study was to systematically investigate the influence of different stimulation intensities of iTBS, applied over the left dorsolateral prefrontal cortex (DLPFC), on brain activity and executive function in healthy adults.

METHODS

Twenty young healthy adults were enrolled in this randomized cross-over experiment. All participants received a single session iTBS over the left DLPFC at intensities of 50, 70, or 100% of their individual resting motor threshold (RMT), each on separate visits. Functional near-infrared spectroscopy (fNIRS) was used to measure changes of hemoglobin concentrations in prefrontal areas during the verbal fluency task (VFT) before and after stimulation.

RESULTS

After stimulation, iTBS to the left DLPFC with 70% RMT maintained the concentration change of oxyhemoglobin (HbO) in the target area during the VFT. In contrast, 50% [t ₍₁₇₎ = 2.203, P = 0.042, d = 0.523] and 100% iTBS [t ₍₁₇₎ = 2.947, P = 0.009, d = 0.547] significantly decreased change of HbO concentration, indicating an inverse U-shape relationship between stimulation intensity and prefrontal hemodynamic response in healthy young adults. Notably, improved VFT performance was only observed after 70% RMT stimulation [t ₍₁₇₎ = 2.511, P = 0.022, d = 0.592]. Moreover, a significant positive correlation was observed between task performance and the difference in HbO concentration change in the targeted area after 70% RMT stimulation (r = 0.496, P = 0.036) but not after 50 or 100% RMT stimulation.

CONCLUSION

The linear relationship between stimulation intensity and behavioral outcomes reported in previous conventional rTMS studies may not be translated to iTBS. Instead, iTBS at 70% RMT may be more efficacious than 100% RMT.

Dynamic Causal Modeling of the Prefrontal/Amygdala Network During Processing of Emotional Faces

Introduction: The importance of the amygdala/medial orbitofrontal cortex (OFC) network during processing of emotional stimuli, emotional faces in particular, is well established. This premise is supported by converging evidence from animal models, human neuroanatomical results, and neuroimaging studies. However, there is missing evidence from human brain connectivity studies that the OFC and no other prefrontal brain areas such as the dorsolateral prefrontal cortex (DLPFC) or ventrolateral prefrontal cortex (VLPFC) are responsible for amygdala regulation in the functional context of emotional face stimuli. Methods: Dynamic causal modeling of ultrahigh-field functional magnetic resonance imaging data acquired at 7 Tesla in 38 healthy subjects and a well-established paradigm for emotional face processing were used to assess the central role of the OFC to provide empirical validation for the assumed network architecture. Results: Using Bayesian model selection, it is demonstrated that indeed the OFC, and not the VLPFC and the DLPFC, downregulates amygdala activation during the emotion discrimination task. In addition, Bayesian model averaging group results were rigorously tested using bootstrapping, further corroborating these findings and providing an estimator for robustness and optimal sample sizes. Discussion: While it is true that VLPFC and DLPFC are relevant for the processing of emotional faces and are connected to the OFC, the OFC appears to be a central hub for the prefrontal/amygdala interaction.

Give me a pain that I am used to: distinct habituation patterns to painful and non-painful stimulation

Pain habituation is associated with a decrease of activation in brain areas related to pain perception. However, little is known about the specificity of these decreases to pain, as habituation has also been described for other responses like spinal reflexes and other sensory responses. Thus, it might be hypothesized that previously reported reductions in activation are not specifically related to pain habituation. For this reason, we performed a 3 T fMRI study using either painful or non-painful electrical stimulation via an electrode attached to the back of the left hand. Contrasting painful vs. non-painful stimulation revealed significant activation clusters in regions well-known to be related to pain processing, such as bilateral anterior and posterior insula, primary/secondary sensory cortices (S1/S2) and anterior midcingulate cortex (aMCC). Importantly, our results show distinct habituation patterns for painful (in aMCC) and non-painful (contralateral claustrum) stimulation, while similar habituation for both types of stimulation was identified in bilateral inferior frontal gyrus (IFG) and contralateral S2. Our findings thus distinguish a general habituation in somatosensory processing (S2) and reduced attention (IFG) from specific pain and non-pain related habituation effects where pain-specific habituation effects within the aMCC highlight a change in affective pain perception.

High-dose testosterone treatment reduces monoamine oxidase A levels in the human brain: A preliminary report

The sex hormones testosterone and estradiol influence brain structure and function and are implicated in the pathogenesis, prevalence and disease course of major depression. Recent research employing gender-affirming hormone treatment (GHT) of gender dysphoric individuals and utilizing positron emission tomography (PET) indicates increased serotonin transporter binding upon high-dosages of testosterone treatment. Here, we investigated the effects of GHT on levels of monoamine oxidase A (MAO-A), another key target of antidepressant treatment. Participants underwent PET with the radioligand [¹¹C]harmine to assess cerebral MAO-A distribution volumes (V_T) before and four months after initiation of GHT. By the time this study was terminated for technical reasons, 18 transgender individuals undergoing GHT (11 transmen, TM and 7 transwomen, TW) and 17 cis-gender subjects had been assessed. Preliminary analysis of available data revealed statistically significant MAO-A V_T reductions in TM under testosterone treatment in six of twelve a priori defined regions of interest (middle frontal cortex (-10%), anterior cingulate cortex (-9%), medial cingulate cortex (-10.5%), insula (-8%), amygdala (-9%) and hippocampus (-8.5%, all p<0.05)). MAO-A V_T did not change in TW receiving estrogen treatment. Despite the limited sample size, pronounced MAO-A V_T reduction could be observed, pointing towards a potential effect of testosterone. Considering MAO-A's central role in regulation of serotonergic neurotransmission, changes to MAO-A V_T should be further investigated as a possible mechanism by which testosterone mediates risk for, symptomatology of, and treatment response in affective disorders.

Sex Matters: A Multivariate Pattern Analysis of Sex- and Gender-Related Neuroanatomical Differences in Cis- and Transgender Individuals Using Structural Magnetic Resonance Imaging

Univariate analyses of structural neuroimaging data have produced heterogeneous results regarding anatomical sex- and gender-related differences. The current study aimed at delineating and cross-validating brain volumetric surrogates of sex and gender by comparing the structural magnetic resonance imaging data of cis- and transgender subjects using multivariate pattern analysis. Gray matter (GM) tissue maps of 29 transgender men, 23 transgender women, 35 cisgender women, and 34 cisgender men were created using voxel-based morphometry and analyzed using support vector classification. Generalizability of the models was estimated using repeated nested cross-validation. For external validation, significant models were applied to hormone-treated transgender subjects (n = 32) and individuals diagnosed with depression (n = 27). Sex was identified with a balanced accuracy (BAC) of 82.6% (false discovery rate [pFDR] < 0.001) in cisgender, but only with 67.5% (pFDR = 0.04) in transgender participants indicating differences in the neuroanatomical patterns associated with sex in transgender despite the major effect of sex on GM volume irrespective of the self-identification as a woman or man. Gender identity and gender incongruence could not be reliably identified (all pFDR > 0.05). The neuroanatomical signature of sex in cisgender did not interact with depressive features (BAC = 74.7%) but was affected by hormone therapy when applied in transgender women (P < 0.001).

Gray Matter Abnormalities in Type 1 and Type 2 Diabetes: A Dual Disorder ALE Quantification

Aims/hypothesis: Diabetes mellitus (DM) is associated with comorbid brain disorders. Neuroimaging studies in DM revealed neuronal degeneration in several cortical and subcortical brain regions. Previous studies indicate more pronounced brain alterations in type 2 diabetes mellitus (T2DM) than in type 1 diabetes mellitus (T1DM). However, a comparison of both types of DM in a single analysis has not been done so far. The aim of this meta-analysis was to conduct an unbiased objective investigation of neuroanatomical differences in DM by combining voxel-based morphometry (VBM) studies of T1DM and T2DM using dual disorder anatomical likelihood estimation (ALE) quantification.

Methods: PubMed, Web of Science and Medline were systematically searched for publications until June 15, 2020. VBM studies comparing gray matter volume (GMV) differences between DM patients and controls at the whole-brain level were included. Study coordinates were entered into the ALE meta-analysis to investigate the extent to which T1DM, T2DM, or both conditions contribute to gray matter volume differences compared to controls.

Results: Twenty studies (comprising of 1,175 patients matched with 1,013 controls) were included, with seven studies on GMV alterations in T1DM and 13 studies on GMV alterations in T2DM. ALE analysis revealed seven clusters of significantly lower GMV in T1DM and T2DM patients relative to controls across studies. Both DM subtypes showed GMV reductions in the left caudate, right superior temporal lobe, and left cuneus. Conversely, GMV reductions associated exclusively with T2DM (>99% contribution) were found in the left cingulate, right posterior lobe, right caudate and left occipital lobe. Meta-regression revealed no significant influence of study size, disease duration, and HbA1c values.

Conclusions/interpretation: Our findings suggest a more pronounced gray matter atrophy in T2DM compared to T1DM. The increased risk of microvascular or macrovascular complications, as well as the disease-specific pathology of T2DM may contribute to observed GMV reductions.

Systematic Review Registration: [PROSPERO], identifier [CRD42020142525].

The Neuroanatomy of Transgender Identity: Mega-Analytic Findings From the ENIGMA Transgender Persons Working Group

BACKGROUND

In contrast to cisgender persons, transgender persons identify with a different gender than the one assigned at birth. Although research on the underlying neurobiology of transgender persons has been accumulating over the years, neuroimaging studies in this relatively rare population are often based on very small samples resulting in discrepant findings.

AIM

To examine the neurobiology of transgender persons in a large sample.

METHODS

Using a mega-analytic approach, structural MRI data of 803 non-hormonally treated transgender men (TM, n = 214, female assigned at birth with male gender identity), transgender women (TW, n = 172, male assigned at birth with female gender identity), cisgender men (CM, n = 221, male assigned at birth with male gender identity) and cisgender women (CW, n = 196, female assigned at birth with female gender identity) were analyzed.

OUTCOMES

Structural brain measures, including grey matter volume, cortical surface area, and cortical thickness.

RESULTS

Transgender persons differed significantly from cisgender persons with respect to (sub)cortical brain volumes and surface area, but not cortical thickness. Contrasting the 4 groups (TM, TW, CM, and CW), we observed a variety of patterns that not only depended on the direction of gender identity (towards male or towards female) but also on the brain measure as well as the brain region examined.

CLINICAL TRANSLATION

The outcomes of this large-scale study may provide a normative framework that may become useful in clinical studies.

STRENGTHS AND LIMITATIONS

While this is the largest study of MRI data in transgender persons to date, the analyses conducted were governed (and restricted) by the type of data collected across all participating sites.

CONCLUSION

Rather than being merely shifted towards either end of the male-female spectrum, transgender persons seem to present with their own unique brain phenotype. Mueller SC, Guillamon A, Zubiaurre-Elorza L, et al. The Neuroanatomy of Transgender Identity: Mega-Analytic Findings From the ENIGMA Transgender Persons Working Group. J Sex Med 2021;18:1122-1129.

Effects of virtual reality in post-stroke aphasia: a systematic review and meta-analysis

OBJECTIVE

To investigate whether virtual reality (VR) interventions have beneficial effects on the functional communication and language function of patients with post-stroke aphasia (PSA).

METHODS

We searched nine electronic literature databases and two clinical registry platforms to identify randomized controlled trials (RCTs) and quasi-RCTs performed up to September 2020. Screening, quality assessment, and data collection were performed by two authors independently, using standard protocols. Data aggregation and risk of bias evaluation were conducted using Review Manager Version 5.4. The quality of evidence was evaluated with GRADEpro.

RESULTS

A total of five studies involving 121 participants met the inclusion criteria and were appraised. Four studies were included in the quantitative synthesis. VR reduced the severity of language impairment with borderline significance [SMD (95%CI) = 0.70[0.01, 1.39], P=0.05]. The meta-analysis showed no statistical difference in functional communication [SMD (95%CI) =0.41[-0.29, 1.12], P=0.25], word finding [SMD (95%CI) =0.42[-0.24, 1.08], P=0.21], and repetition [SMD (95%CI) =0.16[-0.62, 0.94], P=0.68] between VR group and the control group.

CONCLUSION

This review demonstrated a borderline positive clinical effect of VR for the severity of language impairment when compared with conventional rehabilitation therapy. Conversely, VR had no effect on functional communication, word finding, and repetition. Further research is warranted to reach more definite conclusions.

The intervention, the patient and the illness - Personalizing non-invasive brain stimulation in psychiatry

Current hypotheses on the therapeutic action of non-invasive brain stimulation (NIBS) in psychiatric disorders build on the abundant data from neuroimaging studies. This makes NIBS a very promising tool for developing personalized interventions within a precision medicine framework. NIBS methods fundamentally vary in their neurophysiological properties. They comprise repetitive transcranial magnetic stimulation (rTMS) and its variants (e.g. theta burst stimulation - TBS) as well as different types of transcranial electrical stimulation (tES), with the largest body of evidence for transcranial direct current stimulation (tDCS). In the last two decades, significant conceptual progress has been made in terms of NIBS targets, i.e. from single brain regions to neural circuits and to functional connectivity as well as their states, recently leading to brain state modulating closed-loop approaches. Regarding structural and functional brain anatomy, NIBS meets an individually unique constellation, which varies across normal and pathophysiological states. Thus, individual constitutions and signatures of disorders may be indistinguishable at a given time point, but can theoretically be parsed along course- and treatment-related trajectories. We address precision interventions on three levels: 1) the NIBS intervention, 2) the constitutional factors of a single patient, and 3) the phenotypes and pathophysiology of illness. With examples from research on depressive disorders, we propose solutions and discuss future perspectives, e.g. individual MRI-based electrical field strength as a proxy for NIBS dosage, and also symptoms, their clusters, or biotypes instead of disorder focused NIBS. In conclusion, we propose interleaved research on these three levels along a general track of reverse and forward translation including both clinically directed research in preclinical model systems, and biomarker guided controlled clinical trials. Besides driving the development of safe and efficacious interventions, this framework could also deepen our understanding of psychiatric disorders at their neurophysiological underpinnings.

Neural Processes Underlying Mirror-Induced Visual Illusion: An Activation Likelihood Estimation Meta-Analysis

Introduction: Neuroimaging studies on neural processes associated with mirror-induced visual illusion (MVI) are growing in number. Previous systematic reviews on these studies used qualitative approaches.

Objective: The present study conducted activation likelihood estimation (ALE) meta-analysis to locate the brain areas for unfolding the neural processes associated with the MVI.

Method: We searched the CINAHL, MEDLINE, Scopus, and PubMed databases and identified eight studies (with 14 experiments) that met the inclusion criteria.

Results: Contrasting with a rest condition, strong convergence in the bilateral primary and premotor areas and the inferior parietal lobule suggested top-down motor planning and execution. In addition, convergence was identified in the ipsilateral precuneus, cerebellum, superior frontal gyrus, and superior parietal lobule, clusters corresponding to the static hidden hand indicating self-processing operations, somatosensory processing, and motor control. When contrasting with an active movement condition, additional substantial convergence was revealed in visual-related areas, such as the ipsilateral cuneus, fusiform gyrus, middle occipital gyrus (visual area V2) and lingual gyrus, which mediate basic visual processing.

Conclusions: To the best of our knowledge, the current meta-analysis is the first to reveal the visualization, mental rehearsal and motor-related processes underpinning the MVI and offers theoretical support on using MVI as a clinical intervention for post-stroke patients.

Non-invasive brain stimulation for posttraumatic stress disorder: a systematic review and meta-analysis

Approximately 7-9% of people develop posttraumatic stress disorder in their lifetime, but standard pharmacological treatment or psychotherapy shows a considerable individual variation in their effectiveness. Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) hold promise for the treatment of posttraumatic stress disorder. The objective of this meta-analysis was to summarize the existing evidence on the therapeutic effects of these brain stimulation treatments on posttraumatic core symptoms. We systematically retrieved articles published between 1st January 2000 and 1st January 2020 comparing the effects of active with sham stimulation or no intervention in posttraumatic patients from eight databases. Random-effects model was used for meta-analysis. Meta-regression and subgroup meta-analysis was performed to investigate the influence of stimulation dose and different stimulation protocols, respectively. 20 studies were included in this review, where of 11 randomized controlled trials were subjected to quantitative analysis. Active stimulation demonstrated significant reductions of core posttraumatic symptoms with a large effect size (Hedge's g = -0.975). Subgroup analysis showed that both excitatory and inhibitory rTMS of the right dorsolateral prefrontal cortex led to symptom reductions with a large (Hedges' g = -1.161, 95% CI, -1.823 to -0.499; p = 0.015) and medium effect size (Hedges' g = -0.680, 95% CI: -0.139 to -0.322; p ≤ 0.001) respectively. Results further indicated significant durability of symptom-reducing effects of treatments during a two to four weeks period post stimulation (Hedges' g = -0.909, 95% CI: -1.611 to -0.207; p = 0.011). rTMS of the right dorsolateral prefrontal cortex appears to have a positive effect in reducing core symptoms in patients with posttraumatic stress disorder.

Gender-affirming hormone treatment - A unique approach to study the effects of sex hormones on brain structure and function

Investigating the effects of the gender-affirming hormone treatment of transgender people using neuroimaging provides a unique opportunity to study the impact of high dosages of sex hormones on human brain structure and function. This line of research is of relevance from a basic neuroscientific as well as from a psychiatric viewpoint. Prevalence rates, etiopathology, and disease course of many psychiatric disorders exhibit sex differences which are linked to differences in sex hormone levels. Here, we review recent neuroimaging studies from others and our group that investigate the effects of gender-affirming hormone treatment in a longitudinal design utilizing structural and functional magnetic resonance imaging and positron emission tomography. Studies point to a general anabolic and anticatabolic effect of testosterone on grey and white matter structure, whereas estradiol and antiandrogen treatment seems to have partly opposite effects. Moreover, preliminary research indicates that gender-affirming hormone treatment influences serotonergic neurotransmission, a finding that is especially interesting for psychiatry. A clear picture of a hormonal influence on brain activity has yet to emerge. In conclusion, the available evidence reviewed here clearly indicates that sex hormone applications influence brain structure and function in the adult human brain.

Rumination network dysfunction in major depression: A brain connectome study

BACKGROUND

Rumination is a central feature of major depressive disorder (MDD). Knowledge of the neural structures that underpin rumination offers significant insight into depressive pathophysiology and may help to develop potential intervention strategies for MDD, a mental illness that has become the leading cause of disability worldwide.

METHODS

Using resting-state fMRI and graph theory, this study adopted a connectome approach to examine the functional topological organization of the neural network associated with rumination in MDD. Data from 96 participants were analyzed, including 51 patients with MDD and 45 healthy controls.

RESULTS

We found altered functional integration and segregation of neural networks associated with depressive rumination as indicated by reduced global and local efficiency in MDD patients compared with controls. Interestingly, these metrics correlated positively with depression severity, as measured by the Hamilton Depression Rating Scale. Moreover, mediation analysis indicated that the association between network metrics and depression severity was mediated by the ruminative tendency of patients. Disrupted nodal centralities were located in regions associated with emotional processing, visual mental imagery, and attentional control.

CONCLUSION

Our results highlight rumination as a two-edged sword that reflects a disease-specific neuropathology but also points to a functionality of depressive symptoms with evolutionary meaning.

Genetics of sex differences in neuroanatomy and function

Sex differences are observed at many distinct biologic levels, such as in the anatomy and functioning of the brain, behavior, and susceptibility to neuropsychiatric disorders. Previously, these differences were believed to entirely result from the secretion of gonadal hormones; however, recent research has demonstrated that differences are also the consequence of direct or nonhormonal effects of genes located on the sex chromosomes. This chapter reviews the four core genotype model that separates the effects of hormones and sex chromosomes and highlights a few genes that are believed to be partly responsible for sex dimorphism of the brain, in particular, the Sry gene. Genetics of the brain's neurochemistry is discussed and the susceptibility to certain neurologic and psychiatric disorders is reviewed. Lastly, we discuss the sex-specific genetic contribution in disorders of sexual development. The precise molecular mechanisms underlying these differences are currently not entirely known. An increased knowledge and understanding of the role of candidate genes will undeniably be of great aid in elucidating the molecular basis of sex-biased disorders and potentially allow for more sex-specific therapies.

Effects of repetitive transcranial magnetic stimulation (rTMS) on craving and substance consumption in patients with substance dependence: a systematic review and meta-analysis

BACKGROUND AND AIMS

Repetitive transcranial magnetic stimulation (rTMS) is increasingly used as an intervention for treating substance dependence. We aimed to assess evidence of the anti-craving and consumption-reducing effects of rTMS in patients with alcohol, nicotine and illicit drug dependence.

METHODS

A systematic review and meta-analysis of 26 randomized controlled trials (RCTs) published from January 2000 to October 2018 that investigated the effects of rTMS on craving and substance consumption in patients with nicotine, alcohol and illicit drug dependence (n = 748). Craving, measured using self-reported questionnaires or visual analog scale, and substance consumption, measured using self-report substance intake or number of addiction relapse cases, were considered as primary and secondary outcomes, respectively. Substance type, study design and rTMS parameters were used as the independent factors in the meta-regression.

RESULTS

Results showed that excitatory rTMS of the left dorsolateral pre-frontal cortex (DLPFC) significantly reduced craving [Hedges' g = -0.62; 95% confidence interval (CI) = -0.89 to -0.35; P < 0.0001], compared with sham stimulation. Moreover, meta-regression revealed a significant positive association between the total number of stimulation pulses and effect size among studies using excitatory left DLPFC stimulation (P = 0.01). Effects of other rTMS protocols on craving were not significant. However, when examining substance consumption, excitatory rTMS of the left DLPFC and excitatory deep TMS (dTMS) of the bilateral DLPFC and insula revealed significant consumption-reducing effects, compared with sham stimulation.

CONCLUSION

Excitatory repetitive transcranial magnetic stimulation of the dorsolateral pre-frontal cortex appears to have an acute effect on reducing craving and substance consumption in patients with substance dependence. The anti-craving effect may be associated with stimulation dose.

Probing the Impact of Gender-Affirming Hormone Treatment on Odor Perception

Evidence suggests that women outperform men in core aspects of odor perception, and sex hormones may play a significant role in moderating this effect. The gender-affirming treatment (GAT) of transgender persons constitutes a powerful natural experiment to study the psychological and behavioral effects of high dosages of cross-sex hormone applications. Therefore, our aim was to investigate the effects of GAT on odor perception in a sample of 131 participants including female and male controls, as well as transmen and transwomen over their first 4 months of gender transition. The Sniffin’ Sticks test battery was used to measure odor detection, discrimination, and identification at baseline, as well as 1 and 4 months after the start of GAT. Plasma levels of estradiol, testosterone, and sex hormone-binding globulin were analyzed for each assessment point. Results revealed no significant change of olfactory performance in the two transgender groups compared with female and male controls. There was no significant difference between groups at baseline or any other time point. Neither biological sex, nor gender identity had an influence on odor perception. Moreover, there was no significant correlation between sex hormones and odor perception and between GAT-induced changes in sex hormones and changes in odor perception. Our results indicate that the effects of sex hormones on olfactory performance are subtle, if present at all. However, our results do not preclude hormonal effects on odors not included in the Sniffin’ Sticks test battery, such as body odors or odors associated with sex.

Correction: Epistasis of HTR1A and BDNF risk genes alters cortical 5-HT1A receptor binding: PET results link genotype to molecular phenotype in depression

In the original Article, co-author Professor Andreas Hahn was not included in the author list. This has been corrected in the XML, PDF and HTML versions of this Article.