Brain Modulation Research Articles

Amygdala self-neuromodulation capacity as a window for process-related network recruitment.

Neurofeedback (NF) has emerged as a promising avenue for demonstrating process-related neuroplasticity, enabling self-regulation of brain function. NF targeting the amygdala has drawn attention to therapeutic potential in psychiatry, by potentially harnessing emotion-regulation processes. However, not all individuals respond equally to NF training, possibly owing to varying self-regulation abilities. This underscores the importance of understanding the mechanisms behind successful neuromodulation (i.e. capacity). This study aimed to investigate the establishment and neural correlates of neuromodulation capacity using data from repeated sessions of amygdala electrical fingerprint (Amyg-EFP)-NF and post-training functional magnetic resonance imaging (fMRI)-NF sessions. Results from 97 participants (healthy controls and post-traumatic stress disorder and fibromyalgia patients) revealed increased Amyg-EFP neuromodulation capacity over training, associated with post-training amygdala-fMRI modulation capacity and improvements in alexithymia. Individual differenaces in this capacity were associated with pre-training amygdala reactivity and initial neuromodulation success. Additionally, amygdala downregulation during fMRI-NF co-modulated with other regions such as the posterior insula and parahippocampal gyrus. This combined modulation better explained EFP-modulation capacity and improvement in alexithymia than the amygdala modulation alone, suggesting the relevance of this broader network to gained capacity. These findings support a network-based approach for NF and highlight the need to consider individual differences in brain function and modulation capacity to optimize NF interventions. This article is part of the theme issue 'Neurofeedback: new territories and neurocognitive mechanisms of endogenous neuromodulation'.

Brain Defense of Glycemia in Health and Diabetes.

The brain coordinates the homeostatic defense of multiple metabolic variables, including blood glucose levels, in the context of ever-changing external and internal environments. The biologically defended level of glycemia (BDLG) is the net result of brain modulation of insulin-dependent mechanisms in cooperation with the islet, and insulin-independent mechanisms through direct innervation and neuroendocrine control of glucose effector tissues. In this article, we highlight evidence from animal and human studies to develop a framework for the brain’s core homeostatic functions—sensory/afferent, integration/processing, and motor/efferent—that contribute to the normal BDLG in health and its elevation in diabetes.

Clinical efficacy of low-intensity pulsed ultrasound in Parkinson's disease with cognitive impairment.

Low-intensity pulsed ultrasound (LIPUS), is a new technique for invasive brain stimulation and modulation that has emerged recently, but the effects in Parkinson's disease with cognitive impairment (PD-CI) have been less observed. In this study, we collected 56 patients with PD-CI who were continuously treated with LIPUS for 8 weeks, and observed the clinical efficacy of LIPUS on PD-CI patients by comparing with the Sham stimulation continuous treatment. Fifty-six PD-CI patients were divided into the Sham group (given Sham stimulation on top of conventional medication, n = 28) and the LIPUS group (given LIPUS stimulation on top of conventional medication, n = 28), and both groups continued treatment for 8 weeks. Post-treatment efficacy and pre- and post-treatment cognitive function [Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA)], emotional state [Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI)], quality of life [Unified Parkinson's Disease Rating Scale (UPDRS), 39-item Parkinson's Disease Questionnaire (PDQ-39)], and serologic indices [5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA)] were compared. The total effective rate of the LIPUS group was higher versus that of the Sham group. In both groups, MMSE and MoCA scores increased; BDI and BAI scores decreased; UPDRS and PDQ-39 scores were reduced; the levels of 5-HT, NE, and DA were elevated. The above changes were more pronounced in the LIPUS group (all P < 0.05). The application of LIPUS on PD-CI could ameliorate patients' cognitive function, emotional state and quality of life, and regulate and optimize neurotransmitter expression levels.

Olfactory bulb stimulation mitigates Alzheimer's-like disease progression.

Deep brain stimulation (DBS) has demonstrated potential in mitigating Alzheimer's disease (AD). However, the invasive nature of DBS presents challenges for its application. The olfactory bulb (OB), showing early AD-related changes and extensive connections with memory regions, offers an attractive entry point for intervention, potentially restoring normal activity in deteriorating memory circuits. Our study examined the impact of electrically stimulating the OB on working memory as well as pathological and electrophysiological alterations in the OB, medial prefrontal cortex, hippocampus, and entorhinal cortex in amyloid beta (Aβ) AD model rats. Male Wistar rats underwent surgery for electrode implantation in brain regions, inducing Alzheimer's-like disease. Bilateral olfactory bulb (OB) electrical stimulation was performed for 1 hour daily to the OB of stimulation group animals for 18 consecutive days, followed by the evaluations of histological, behavioral, and local field potential signal processing. OB stimulation counteracted Aβ plaque accumulation and prevented AD-induced working memory impairments. Furthermore, it prompted an increase in power across diverse frequency bands and enhanced functional connectivity, particularly in the gamma band, within the investigated regions during a working memory task. This preclinical investigation highlights the potential of olfactory pathway-based brain stimulation to modulate the activity of deep-seated memory networks for AD treatment. Importantly, the accessibility of this pathway via the nasal cavity lays the groundwork for the development of minimally invasive approaches targeting the olfactory pathway for brain modulation.

Precise Localization of the Central Left Frontal Cortex in Different Canine Skull Types: A Comparative Study of Frameless Neuronavigation and External Measurement Techniques

Repetitive Transcranial Magnetic Stimulation (rTMS), a non-invasive brain modulation technique, has been explored as an additional treatment option for behaviorally disordered dogs. For optimal effectiveness of the rTMS treatment, accurate coil positioning to the stimulation target is pivotal. Frameless stereotactic neuronavigation for the localization of intracranial regions has been established as a reliable targeting method. However, given the varying skull shape and brain structures among dog breeds, divided into mesocephalic, brachycephalic, and dolichocephalic breeds, localizing the rTMS target area, the central left frontal cortex, can be challenging. Previous neuronavigation studies have only investigated its use in mesocephalic breeds of dogs. Because this neuronavigation is based on expensive high-tesla magnetic resonance imaging data, and anesthesia needed for immobilization, a cheaper and reliable localization alternative to broaden the rTMS use in the veterinary field is needed.The objective of this study was twofold. First, the study aimed to evaluate external localization of the central left frontal cortex within the three skull types (retrospective study 1). Then, this external localization method was compared to the conventional frameless neuronavigation technique to check the consistency, focusing on mesocephalic and dolichocephalic breeds (prospective study 2). Thirty-two brachycephalic, thirty-seven mesocephalic and thirty dolichocephalic dogs were included to evaluate the external localization of the central left frontal cortex by external measurement (retrospective study 1, data obtained from previously performed MRI scans). For the second objective, thirty-eight dogs (35 mesocephalic breeds and 3 dolichocephalic breeds) were recruited to compare the external measurement localization method and the localization by neuronavigation (prospective study 2, data extracted from study 1 and former rTMS studies). The first part of this study showed the central left frontal cortex was externally located approximately two-thirds of the total skull length (sagittal length) in meso- and dolichocephalic dogs, at the center of the skull length in brachycephalic dogs, and 0.65 to 0.70 cm to the left of the cerebral midline for all skull types (retrospective study 1). Using intraclass correlation coefficient (ICC) analysis, the second part of the study showed high consistency between these two methods, for the length of the skull (0.94), the relative position of the left frontal cortex (0.84), and the distance to the cerebral midline (0.69) in mesocephalic and dolichocephalic breeds (prospective study 2). Our findings suggest that the conventional frameless neuronavigation could be replaced by the external localization method in the mesocephalic and dolichocephalic dog breeds, and therefore ultimately reduce anesthesia time and financial burden when applying non-invasive brain modulation techniques like rTMS. More research needs to be conducted for brachycephalic dogs to validate this method in this specific population of dogs.

Mapping individual cortico-basal ganglia-thalamo-cortical circuits integrating structural and functional connectome: implications for upper limb motor impairment poststroke.

This study investigated alterations in functional connectivity (FC) within cortico-basal ganglia-thalamo-cortical (CBTC) circuits and identified critical connections influencing poststroke motor recovery, offering insights into optimizing brain modulation strategies to address the limitations of traditional single-target stimulation. We delineated individual-specific parallel loops of CBTC through probabilistic tracking and voxel connectivity profiles-based segmentation and calculated FC values in poststroke patients and healthy controls, comparing with conventional atlas-based FC calculation. Support vector machine (SVM) analysis distinguished poststroke patients from controls. Connectome-based predictive modeling (CPM) used FC values within CBTC circuits to predict upper limb motor function. Poststroke patients exhibited decreased ipsilesional connectivity within the individual-specific CBTC circuits. SVM analysis achieved 82.8% accuracy, 76.6% sensitivity, and 89.1% specificity using individual-specific parallel loops. Additionally, CPM featuring positive connections/all connections significantly predicted Fugl-Meyer assessment of upper extremity scores. There were no significant differences in the group comparisons of conventional atlas-based FC values, and the FC values resulted in SVM accuracy of 75.0%, sensitivity of 67.2%, and specificity of 82.8%, with no significant CPM capability. Individual-specific parallel loops show superior predictive power for assessing upper limb motor function in poststroke patients. Precise mapping of the disease-related circuits is essential for understanding poststroke brain reorganization.

Dynamic Reorganization Patterns of Brain Modules after Stroke Reflecting Motor Function.

Advancements in neuroimaging technologies have significantly deepened our understanding of the neural physiopathology associated with stroke. Nevertheless, the majority of studies ignored the characteristics of dynamic changes in brain networks. The relationship between dynamic changes in brain networks and the severity of motor dysfunction after stroke needs further investigation. From the perspective of multilayer network module reconstruction, we aimed to explore the dynamic reorganization of the brain and its relationship with motor function in subcortical stroke patients. We recruited 35 healthy individuals and 50 stroke patients with unilateral limb motor dysfunction (further divided into mild-moderate group and severe group). Using dynamic multilayer network modularity analysis, we investigated changes in the dynamic modular reconfiguration of brain networks. Additionally, we assessed longitudinal clinical scale changes in stroke patients. Correlation and regression analyses were employed to explore the relationship between characteristic dynamic indicators and impairment and recovery of motor function, respectively. We observed increased temporal flexibility in the Default Mode Network (DMN) and decreased recruitment of module reconfiguration in the Attention Network (AN), Sensorimotor Network (SMN), and DMN after stroke. We also observed reduced module loyalty following stroke. Additionally, correlation analysis showed that hyper-flexibility of the DMN was associated with better lower limb motor function performance in stroke patients with mild-to-moderate impairment. Regression analysis indicated that increased flexibility within the DMN and decreased recruitment coefficient within the AN may predict good lower limb function prognosis in patients with mild to moderate motor impairment. Our study revealed more frequent modular reconfiguration and hyperactive interaction of brain networks after stroke. Notably, dynamic modular remodeling was closely related to the impairment and recovery of motor function. Understanding the temporal module reconfiguration patterns in multilayer networks after stroke can provide valuable information for more targeted treatments.

Identification of gene co-expression modules from zebrafish brain data: Applications in psychiatry illustrated through alcohol-related traits

Cumulative evidence suggests that zebrafish is a useful model in psychiatric research. Weighted Gene Co-expression Network Analysis (WGCNA) enables the reduction of genome-wide expression data to modules of highly co-expressed genes, which are hypothesized to interact within molecular networks. In this study, we first applied WGCNA to zebrafish brain expression data across different experimental conditions. Then, we characterized the different co-expression modules by gene-set enrichment analysis and hub gene-phenotype association. Finally, we analyzed association of polygenic risk scores (PRSs) based on genes of some interesting co-expression modules with alcohol dependence in 524 patients and 729 controls from Galicia, using competitive tests. Our approach revealed 34 co-expression modules in the zebrafish brain, with some showing enrichment in human synaptic genes, brain tissues, or brain developmental stages. Moreover, certain co-expression modules were enriched in psychiatry-related GWAS and comprised hub genes associated with psychiatry-related traits in both human GWAS and zebrafish models. Expression patterns of some co-expression modules were associated with the tested experimental conditions, mainly with substance withdrawal and cold stress. Notably, a PRS based on genes from co-expression modules exclusively associated with substance withdrawal in zebrafish showed a stronger association with human alcohol dependence than PRSs based on randomly selected brain-expressed genes. In conclusion, our analysis led to the identification of co-expressed gene modules that may model human brain gene networks involved in psychiatry-related traits. Specifically, we detected a cluster of co-expressed genes whose expression was exclusively associated with substance withdrawal in zebrafish, which significantly contributed to alcohol dependence susceptibility in humans.

Acoustic deep brain modulation: Enhancing neuronal activation and neurogenesis

BackgroundNon-invasive deep brain modulation (DBM) stands as a promising therapeutic avenue to treat brain diseases. Acoustic DBM represents an innovative and targeted approach to modulate the deep brain, employing techniques such as focused ultrasound and shock waves. Despite its potential, the optimal mechanistic parameters, the effect in the brain and behavioral outcomes of acoustic DBM remains poorly understood. ObjectiveTo establish a robust protocol for the shock wave DBM by optimizing its mechanistic profile of external stimulation, and to assess its efficacy in preclinical settings. MethodsWe used shockwaves due to their capacity to leverage a broader spectrum of peak intensity (10–127 W/mm2) in contrast to ultrasound (0.1–5.0 W/mm2), thereby enabling a more extensive range of neuromodulation effects. We established various types of shockwave pressure profiles of DBM and compared neural and behavioral responses. To ascertain the anticipated cause of the heightened neural activity response, numerical analysis was employed to examine the mechanical dynamics within the brain. ResultsAn optimized profile led to an enhancement in neuronal activity within the hypothalamus of mouse models. The optimized profile in the hippocampus elicited a marked increase in neurogenesis without neuronal damage. Behavioral analyses uncovered a noteworthy reduction in locomotion without significant effects on spatial memory function. ConclusionsThe present study provides an optimized shock wave stimulation protocol for non-invasive DBM. Our optimized stimulation profile selectively triggers neural functions in the deep brain. Our protocol paves the way for new non-invasive DBM devices to treat brain diseases.

Functional near-infrared spectroscopy-based neurofeedback training targeting the dorsolateral prefrontal cortex induces changes in cortico-striatal functional connectivity

Due to its central role in cognitive control, the dorso–lateral prefrontal cortex (dlPFC) has been the target of multiple brain modulation studies. In the context of the present pilot study, the dlPFC was the target of eight repeated neurofeedback (NF) sessions with functional near infrared spectroscopy (fNIRS) to assess the brain responses during NF and with functional and resting state magnetic resonance imaging (task-based fMRI and rsMRI) scanning. Fifteen healthy participants were recruited. Cognitive task fMRI and rsMRI were performed during the 1st and the 8th NF sessions. During NF, our data revealed an increased activity in the dlPFC as well as in brain regions involved in cognitive control and self-regulation learning (pFWE < 0.05). Changes in functional connectivity between the 1st and the 8th session revealed increased connectivity between the posterior cingulate cortex and the dlPFC, and between the posterior cingulate cortex and the dorsal striatum (pFWE < 0.05). Decreased left dlPFC-left insula connectivity was also observed. Behavioural results revealed a significant effect of hunger and motivation on the participant control feeling and a lower control feeling when participants did not identify an effective mental strategy, providing new insights on the effects of behavioural factors that may affect the NF learning.

Expectations and transcranial direct current stimulation-induced brain modulation: independent and additive effects on experimental pain.

Expectations and transcranial direct current stimulation-induced brain modulation: independent and additive effects on experimental pain.

(Invited) Seeing the Sound: An Ultrasound-Mediated Intravascular Light Source for Noninvasive Brain Modulation

Light is used in a wide range of methods in biology and medicine, such as fluorescence imaging, optogenetics, photoactivatable gene editing, photothermal and photodynamic therapies to treat cancers, and photochemotherapy to inactivate viruses in vivo. A critical challenge of applying light in vivo, such as deep-brain optogenetic neuromodulation and photochemotherapy in deep organs, arises from the poor penetration of photons in biological tissue due to scattering and absorption. Therefore, delivering light deep into the body requires invasive procedures, such as the insertion of optical fibers and endoscopes, as well as surgical removal of overlying tissues. The very invasiveness of these procedures also precludes easy repositioning and volume adjustment of the illuminated region in the same subject. To address these challenges, our lab has developed an ultrasound-mediated intravascular light source, leveraging the deep-tissue penetration of focused ultrasound. We capitalized on mechanoluminescent nanotransducers (MLNTs), which are colloidal nanoparticles of mechanoluminescent materials synthesized via a biomineral-inspired suppressed dissolution approach. These MLNTs can be delivered intravenously into blood circulation and emit light locally at the ultrasound focus. Owing to the deep penetration and fast temporal kinetics of ultrasound, we have demonstrated that this method can produce on-demand and dynamically programmable light emission patterns at elevated depths in different organs of live mice with millisecond precision. This ultrasound-mediated intravascular light source has allowed us to perform noninvasive “sono-optogenetic” neuromodulation in live mice, as well as brain-wide “scanning optogenetics” that activate different brain regions of the same mouse brain. Our development of the ultrasound-mediated intravascular light source has been published in PNAS (2019), Science (2020), Science Advances (2022), JACS (2022), JACS (2023), and Nature Protocols (2023).

Brain modulation after exergaming training in advanced forms of Parkinson’s disease: a randomized controlled study

BackgroundPhysical activity combined with virtual reality and exergaming has emerged as a new technique to improve engagement and provide clinical benefit for gait and balance disorders in people with Parkinson’s disease (PD).ObjectiveTo investigate the effects of a training protocol using a home-based exergaming system on brain volume and resting-state functional connectivity (rs-FC) in persons with PD.MethodsA single blind randomized controlled trial was conducted in people with PD with gait and/or balance disorders. The experimental (active) group performed 18 training sessions at home by playing a custom-designed exergame with full body movements, standing in front of a RGB-D Kinect® motion sensor, while the control group played using the computer keyboard. Both groups received the same training program. Clinical scales, gait recordings, and brain MRI were performed before and after training. We assessed the effects of both training on both the grey matter volumes (GVM) and rs-FC, within and between groups.ResultsTwenty-three patients were enrolled and randomly assigned to either the active (n = 11) or control (n = 12) training groups. Comparing pre- to post-training, the active group showed significant improvements in gait and balance disorders, with decreased rs-FC between the sensorimotor, attentional and basal ganglia networks, but with an increase between the cerebellar and basal ganglia networks. In contrast, the control group showed no significant changes, and rs-FC significantly decreased in the mesolimbic and visuospatial cerebellar and basal ganglia networks. Post-training, the rs-FC was greater in the active relative to the control group between the basal ganglia, motor cortical and cerebellar areas, and bilaterally between the insula and the inferior temporal lobe. Conversely, rs FC was lower in the active relative to the control group between the pedunculopontine nucleus and cerebellar areas, between the temporal inferior lobes and the right thalamus, between the left putamen and dorsolateral prefrontal cortex, and within the default mode network.ConclusionsFull-body movement training using a customized exergame induced brain rs-FC changes within the sensorimotor, attentional and cerebellar networks in people with PD. Further research is needed to comprehensively understand the neurophysiological effects of such training approaches.Trial registration ClinicalTrials.gov NCT03560089.

The role of functional emotion circuits in distinct dimensions of psychopathology in youth

Several mental disorders emerge during childhood or adolescence and are often characterized by socioemotional difficulties, including alterations in emotion perception. Emotional facial expressions are processed in discrete functional brain modules whose connectivity patterns encode emotion categories, but the involvement of these neural circuits in psychopathology in youth is poorly understood. This study examined the associations between activation and functional connectivity patterns in emotion circuits and psychopathology during development. We used task-based fMRI data from the Philadelphia Neurodevelopmental Cohort (PNC, N = 1221, 8–23 years) and conducted generalized psycho-physiological interaction (gPPI) analyses. Measures of psychopathology were derived from an independent component analysis of questionnaire data. The results showed positive associations between identifying fearful, sad, and angry faces and depressive symptoms, and a negative relationship between sadness recognition and positive psychosis symptoms. We found a positive main effect of depressive symptoms on BOLD activation in regions overlapping with the default mode network, while individuals reporting higher levels of norm-violating behavior exhibited emotion-specific lower functional connectivity within regions of the salience network and between modules that overlapped with the salience and default mode network. Our findings illustrate the relevance of functional connectivity patterns underlying emotion processing for behavioral problems in children and adolescents.

Reduced spatial frequency differentiation and sex-related specificities in fearful face detection in autism: Insights from EEG and the predictive brain model.

Face processing relies on predictive processes driven by low spatial frequencies (LSF) that convey coarse information prior to fine information conveyed by high spatial frequencies. However, autistic individuals might have atypical predictive processes, contributing to facial processing difficulties. This may be more normalized in autistic females, who often exhibit better socio-communicational abilities than males. We hypothesized that autistic females would display a more typical coarse-to-fine processing for socio-emotional stimuli compared to autistic males. To test this hypothesis, we asked adult participants (44 autistic, 51 non-autistic) to detect fearful faces among neutral faces, filtered in two orders: from coarse-to-fine (CtF) and from fine-to-coarse (FtC). Results show lower d' values and longer reaction times for fearful detection in autism compared to non-autistic (NA) individuals, regardless of the filtering order. Both groups presented shorter P100 latency after CtF compared to FtC, and larger amplitude for N170 after FtC compared to CtF. However, autistic participants presented a reduced difference in source activity between CtF and FtC in the fusiform. There was also a more spatially spread activation pattern in autistic females compared to NA females. Finally, females had faster P100 and N170 latencies, as well as larger occipital activation for FtC sequences than males, irrespective of the group. Overall, the results do not suggest impaired predictive processes from LSF in autism despite behavioral differences in fear detection. However, they do indicate reduced brain modulation by spatial frequency in autism. In addition, the findings highlight sex differences that warrant consideration in understanding autistic females.

No sex difference in maturation of brain morphology during the perinatal period.

Accumulating evidence have documented sex differences in brain anatomy from early childhood to late adulthood. However, whether sex difference of brain structure emerges in the neonatal brain and how sex modulates the development of cortical morphology during the perinatal stage remains unclear. Here, we utilized T2-weighted MRI from the Developing Human Connectome Project (dHCP) database, consisting of 41 male and 40 female neonates born between 35 and 43 postmenstrual weeks (PMW). Neonates of each sex were arranged in a continuous ascending order of age to capture the progressive changes in cortical thickness and curvature throughout the developmental continuum. The maturational covariance network (MCN) was defined as the coupled developmental fluctuations of morphology measures between cortical regions. We constructed MCNs based on the two features, respectively, to illustrate their developmental interdependencies, and then compared the network topology between sexes. Our results showed that cortical structural development exhibited a localized pattern in both males and females, with no significant sex differences in the developmental trajectory of cortical morphology, overall organization, nodal importance, and modular structure of the MCN. Furthermore, by merging male and female neonates into a unified cohort, we identified evident dependencies influences in structural development between different brain modules using the Granger causality analysis (GCA), emanating from high-order regions toward primary cortices. Our findings demonstrate that the maturational pattern of cortical morphology may not differ between sexes during the perinatal period, and provide evidence for the developmental causality among cortical structures in perinatal brains.

The Role of Non-Invasive Brain Modulation in Identifying Disease Biomarkers for Diagnostic and Therapeutic Purposes in Parkinsonism.

Over the past three decades, substantial advancements have occurred in non-invasive brain stimulation (NIBS). These developments encompass various non-invasive techniques aimed at modulating brain function. Among the most widely utilized methods today are transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES), which include direct- or alternating-current transcranial stimulation (tDCS/tACS). In addition to these established techniques, newer modalities have emerged, broadening the scope of non-invasive neuromodulation approaches available for research and clinical applications in movement disorders, particularly for Parkinson's disease (PD) and, to a lesser extent, atypical Parkinsonism (AP). All NIBS techniques offer the opportunity to explore a wide range of neurophysiological mechanisms and exert influence over distinct brain regions implicated in the pathophysiology of Parkinsonism. This paper's first aim is to provide a brief overview of the historical background and underlying physiological principles of primary NIBS techniques, focusing on their translational relevance. It aims to shed light on the potential identification of biomarkers for diagnostic and therapeutic purposes, by summarising available experimental data on individuals with Parkinsonism. To date, despite promising findings indicating the potential utility of NIBS techniques in Parkinsonism, their integration into clinical routine for diagnostic or therapeutic protocols remains a subject of ongoing investigation and scientific debate. In this context, this paper addresses current unsolved issues and methodological challenges concerning the use of NIBS, focusing on the importance of future research endeavours for maximizing the efficacy and relevance of NIBS strategies for individuals with Parkinsonism.

Investigations of microbiota composition and neuroactive pathways in association with symptoms of stress and depression in a cohort of healthy women.

Despite mounting evidence of gut-brain involvement in psychiatric conditions, functional data remain limited, and analyses of other microbial niches, such as the vaginal microbiota, are lacking in relation to mental health. This aim of this study was to investigate if the connections between the gut microbiome and mental health observed in populations with a clinical diagnosis of mental illness extend to healthy women experiencing stress and depressive symptoms. Additionally, this study examined the functional pathways of the gut microbiota according to the levels of psychological symptoms. Furthermore, the study aimed to explore potential correlations between the vaginal microbiome and mental health parameters in young women without psychiatric diagnoses. In this cross-sectional study, 160 healthy Danish women (aged 18-40 years) filled out questionnaires with validated scales measuring symptoms of stress and depression and frequency of dietary intake. Fecal and vaginal microbiota samples were collected at the beginning of the menstrual cycle and vaginal samples were also collected at cycle day 8-12 and 18-22. Shotgun metagenomic profiling of the gut and vaginal microbiome was performed. The Kyoto Encyclopedia of Genes and Genomes (KEGG) was used for functional profiling and 56 Gut Brain Modules were analyzed in the fecal samples. The relative abundance in the gut of the genera Escherichia, Parabacteroides, and Shigella was higher in women with elevated depressive symptoms. Women with high perceived stress showed a tendency of increased abundance of Escherichia, Shigella, and Blautia. Amongst others, the potentially pathogenic genera, Escherichia and Shigella correlate with alterations in the neuroactive pathways such as the glutamatergic, GABAeric, dopaminergic, and Kynurenine pathways. Vaginosis symptoms were more prevalent in women reporting high levels of stress and depressive symptoms. The findings of this study support the concept of a microbiota-associated effect on the neuroactive pathways even in healthy young women. This suggest, that targeting the gut microbiome could be a promising approach for future psychiatric interventions.

Increased Functional Connectivity Between the Parietal and Occipital Modules Among Flight Cadets.

INTRODUCTION: Modular organization in brain regions often performs specific biological functions and is largely based on anatomically and/or functionally related brain areas. The current study aimed to explore changes in whole-brain modular organization affected by flight training.METHODS: The study included 25 male flight cadets and 24 male controls. The first assessment was performed in 2019, when the subjects were university freshmen. The second assessment was completed in 2022. High spatial resolution structural imaging (T1) and resting-state functional MRI data were collected. Then, 90 cerebral regions were organized into 6 brain modules. The intensity of intra- and intermodular communication was calculated.RESULTS: Mixed-effect regression model analysis identified significantly increased interconnections between the parietal and occipital modules in the cadet group, but significantly decreased interconnections in the control group. This change was largely attributed to flight training.DISCUSSION: Pilots need to control the aircraft (e.g., attitude, heading, etc.) using the stick and pedal in response to the current state of the aircraft displayed by the instrument panel; as such, flying requires a large amount of hand-eye coordination. Day-to-day flight training appeared to intensify the connection between the parietal and occipital modules among cadets.Chen X, Jiang H, Meng Y, Xu Z, Luo C. Increased functional connectivity between the parietal and occipital modules among flight cadets. Aerosp Med Hum Perform. 2024; 95(7):375-380.

Indirect neurogenesis in space and time.

During central nervous system (CNS) development, neural progenitor cells (NPCs) generate neurons and glia in two different ways. In direct neurogenesis, daughter cells differentiate directly into neurons or glia, whereas in indirect neurogenesis, neurons or glia are generated after one or more daughter cell divisions. Intriguingly, indirect neurogenesis is not stochastically deployed and plays instructive roles during CNS development: increased generation of cells from specific lineages; increased generation of early or late-born cell types within a lineage; and increased cell diversification. Increased indirect neurogenesis might contribute to the anterior CNS expansion evident throughout the Bilateria and help tomodify brain-region size without requiring increased NPC numbers or extended neurogenesis. Increased indirect neurogenesis could be an evolutionary driver of the gyrencephalic (that is, folded) cortex that emerged during mammalian evolution and might even have increased during hominid evolution. Thus, selection of indirect versus direct neurogenesis provides a powerful developmental and evolutionary instrument that drives not only the evolution of CNS complexity but also brain expansion and modulation of brain-region size, and thereby the evolution of increasingly advanced cognitive abilities. This Review describes indirect neurogenesis in several model species and humans, and highlights some of the molecular genetic mechanisms that control this important process.