Phase synchronized 6 Hz transcranial electric and magnetic stimulation boosts frontal theta activity and enhances working memory.

Network-level synchronization of theta oscillations in the cerebral cortex is linked to many vital cognitive functions across daily life, such as executive functions or regulation of arousal and consciousness. However, while neuroimaging has uncovered the ubiquitous functional relevance of theta rhythms in cognition, there remains a limited set of techniques for externally enhancing and stabilizing theta in the human brain non-invasively. Here, we developed and employed a new phase-synchronized low-intensity electric and magnetic stimulation technique to induce and stabilize narrowband 6-Hz theta oscillations in a group of healthy human adult participants, and then demonstrated how this technique also enhances cognitive processing by assaying working memory. Our findings demonstrate a technological advancement of brain stimulation methods, while also validating the causal link between theta activity and concurrent cognitive behavior, which may ultimately help to not only explain mechanisms, but offer perspectives for restoring deficient theta-band network activity observed in neuropsychiatric diseases.

Nonlinear Effects of Dopamine D1 Receptor Activation on Visuomotor Coordination Task Performance.

Dopamine plays an important role in the modulation of neuroplasticity, which serves as the physiological basis of cognition. The physiological effects of dopamine depend on receptor subtypes, and the D1 receptor is critically involved in learning and memory formation. Evidence from both animal and human studies shows a dose-dependent impact of D1 activity on performance. However, the direct association between physiology and behavior in humans remains unclear. In this study, four groups of healthy participants were recruited, and each group received placebo or medication inducing a low, medium, or high amount of D1 activation via the combination of levodopa and a D2 antagonist. After medication, fMRI was conducted during a visuomotor learning task. The behavioral results revealed an inverted U-shaped effect of D1 activation on task performance, where medium-dose D1 activation led to superior learning effects, as compared to placebo as well as low- and high-dose groups. A respective dose-dependent D1 modulation was also observed for cortical activity revealed by fMRI. Further analysis demonstrated a positive correlation between task performance and cortical activation at the left primary motor cortex. Our results indicate a nonlinear curve of D1 modulation on motor learning in humans and the respective physiological correlates in corresponding brain areas.

Current intensity- and polarity-specific online and aftereffects of transcranial direct current stimulation: An fMRI study.

Transcranial direct current stimulation (tDCS) induces polarity- and dose-dependent neuroplastic aftereffects on cortical excitability and cortical activity, as demonstrated by transcranial magnetic stimulation (TMS) and functional imaging (fMRI) studies. However, lacking systematic comparative studies between stimulation-induced changes in cortical excitability obtained from TMS, and cortical neurovascular activity obtained from fMRI, prevent the extrapolation of respective physiological and mechanistic bases. We investigated polarity- and intensity-dependent effects of tDCS on cerebral blood flow (CBF) using resting-state arterial spin labeling (ASL-MRI), and compared the respective changes to TMS-induced cortical excitability (amplitudes of motor evoked potentials, MEP) in separate sessions within the same subjects (n = 29). Fifteen minutes of sham, 0.5, 1.0, 1.5, and 2.0-mA anodal or cathodal tDCS was applied over the left primary motor cortex (M1) in a randomized repeated-measure design. Time-course changes were measured before, during and intermittently up to 120-min after stimulation. ROI analyses indicated linear intensity- and polarity-dependent tDCS after-effects: all anodal-M1 intensities increased CBF under the M1 electrode, with 2.0-mA increasing CBF the greatest (15.3%) compared to sham, while all cathodal-M1 intensities decreased left M1 CBF from baseline, with 2.0-mA decreasing the greatest (-9.3%) from sham after 120-min. The spatial distribution of perfusion changes correlated with the predicted electric field, as simulated with finite element modeling. Moreover, tDCS-induced excitability changes correlated more strongly with perfusion changes in the left sensorimotor region compared to the targeted hand-knob region. Our findings reveal lasting tDCS-induced alterations in cerebral perfusion, which are dose-dependent with tDCS parameters, but only partially account for excitability changes.

Modulating functional connectivity with non-invasive brain stimulation for the investigation and alleviation of age-associated declines in response inhibition: A narrative review.

Response inhibition, the ability to withhold a dominant and prepotent response following a change in circumstance or sensory stimuli, declines with advancing age. While non-invasive brain stimulation (NiBS) has shown promise in alleviating some cognitive and motor functions in healthy older individuals, NiBS research focusing on response inhibition has mostly been conducted on younger adults. These extant studies have primarily focused on modulating the activity of distinct neural regions known to be critical for response inhibition, including the right inferior frontal gyrus (rIFG) and the pre-supplementary motor area (pre-SMA). However, given that changes in structural and functional connectivity have been associated with healthy aging, this review proposes that NiBS protocols aimed at modulating the functional connectivity between the rIFG and pre-SMA may be the most efficacious approach to investigate-and perhaps even alleviate-age-related deficits in inhibitory control.

Efficacy of oral vitamin D on glycated haemoglobin (HbA1c) in type 2 diabetics having vitamin D deficiency - A randomized controlled trial.

OBJECTIVE: To study the efficacy of oral vitamin D in improving glycaemic control of patients with type 2 diabetes by reducing glycated haemoglobin levels. METHODS: This randomised control trial was carried out at Mayo Hospital, Lahore, from February 5 to August 5, 2016, and comprised type 2 diabetes patients aged 40-70 years visiting the outpatient clinics. They were randomly divided into two groups by using the lottery method. Group A received oral vitamin D along with metformin and group B received metformin only. Blood samples of both the groups were tested for glycated haemoglobin at three months to assess the change. SPSS 21 was used for data analysis. RESULTS: There were 140 patients divided into two groups of 70(50%) each. Mean age in Group A was 54.80±8.55 years and 58.40±7.98 years in Group B. No significant difference was seen in glycated haemoglobin levels at baseline (p>0.05). However, after 3 months post-treatment the levels significantly differed (p<0.05) in favour of Group A. CONCLUSIONS: Vitamin D supplementation had a significant effect in lowering glycated haemoglobin level in patients with type 2 diabetes.

Acute and chronic effects of noradrenergic enhancement on transcranial direct current stimulation-induced neuroplasticity in humans.

KEY POINTS: Chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) increased and prolonged the long-term potentiation-like plasticity induced by anodal transcranial direct current stimulation (tDCS) for over 24 h. Chronic administration of RBX converted cathodal tDCS-induced long-term depression-like plasticity into facilitation for 120 min. Chronic noradrenergic activity enhancement on plasticity of the human brain might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases. ABSTRACT: Noradrenaline affects cognition and motor learning processes via its impact on long-term potentiation (LTP) and depression (LTD). We aimed to explore the impact of single dose and chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) on plasticity induced by transcranial direct current stimulation (tDCS) in healthy humans via a double-blinded, placebo-controlled, randomized crossover study. Sixteen healthy volunteers received placebo or single dose RBX (8 mg) before anodal or cathodal tDCS of the primary motor cortex. Afterwards, the same subjects took RBX (8 mg day-1 ) consecutively for 21 days. During this period, two additional interventions were performed (RBX with anodal or cathodal tDCS), to explore the impact of chronic RBX treatment on plasticity. Plasticity was monitored by motor-evoked potential amplitudes elicited by transcranial magnetic stimulation. Chronic administration of RBX increased and prolonged the LTP-like plasticity induced by anodal tDCS for over 24 h. Chronic RBX significantly converted cathodal tDCS-induced LTD-like plasticity into facilitation, as compared to the single dose condition, for 120 min after stimulation. The results show a prominent impact of chronic noradrenergic enhancement on plasticity of the human brain that might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases.

Systematic evaluation of the impact of stimulation intensity on neuroplastic after-effects induced by transcranial direct current stimulation.

KEY POINTS: Applications of transcranial direct current stimulation to modulate human neuroplasticity have increased in research and clinical settings. However, the need for longer-lasting effects, combined with marked inter-individual variability, necessitates a deeper understanding of the relationship between stimulation parameters and physiological effects. We systematically investigated the full DC intensity range (0.5-2.0 mA) for both anodal and cathodal tDCS in a sham-controlled repeated measures design, monitoring changes in motor-cortical excitability via transcranial magnetic stimulation up to 2 h after stimulation. For both tDCS polarities, the excitability after-effects did not linearly correlate with increasing DC intensity; effects of lower intensities (0.5, 1.0 mA) showed equal, if not greater effects in motor-cortical excitability. Further, while intra-individual responses showed good reliability, inter-individual sensitivity to TMS accounted for a modest percentage of the variance in the early after-effects of 1.0 mA anodal tDCS, which may be of practical relevance for future optimizations. ABSTRACT: Contemporary non-invasive neuromodulatory techniques, such as transcranial direct current stimulation (tDCS), have shown promising potential in both restituting impairments in cortical physiology in clinical settings, as well as modulating cognitive abilities in the healthy population. However, neuroplastic after-effects of tDCS are highly dependent on stimulation parameters, relatively short lasting, and not expectedly uniform between individuals. The present study systematically investigates the full range of current intensity between 0.5 and 2.0 mA on left primary motor cortex (M1) plasticity, as well as the impact of individual-level covariates on explaining inter-individual variability. Thirty-eight healthy subjects were divided into groups of anodal and cathodal tDCS. Five DC intensities (sham, 0.5, 1.0, 1.5 and 2.0 mA) were investigated in separate sessions. Using transcranial magnetic stimulation (TMS), 25 motor-evoked potentials (MEPs) were recorded before, and 10 time points up to 2 h following 15 min of tDCS. Repeated-measures ANOVAs indicated a main effect of intensity for both anodal and cathodal tDCS. With anodal tDCS, all active intensities resulted in equivalent facilitatory effects relative to sham while for cathodal tDCS, only 1.0 mA resulted in sustained excitability diminution. An additional experiment conducted to assess intra-individual variability revealed generally good reliability of 1.0 mA anodal tDCS (ICC(2,1) = 0.74 over the first 30 min). A post hoc analysis to discern sources of inter-individual variability confirmed a previous finding in which individual TMS SI1mV (stimulus intensity for 1 mV MEP amplitude) sensitivity correlated negatively with 1.0 mA anodal tDCS effects on excitability. Our study thus provides further insights on the extent of non-linear intensity-dependent neuroplastic after-effects of anodal and cathodal tDCS.

Acute and Chronic Noradrenergic Effects on Cortical Excitability in Healthy Humans.

Background: Noradrenaline is a major neuromodulator in the central nervous system, and it is involved in the pathophysiology of diverse neuropsychiatric diseases. Previous transcranial magnetic stimulation studies suggested that acute application of selective noradrenaline reuptake inhibitors enhances cortical excitability in the human brain. However, other, such like clinical effects, usually require prolonged noradrenaline reuptake inhibitor treatment, which might go along with different physiological effects. Methods: The purpose of this study was to investigate the acute and chronic effects of the selective noradrenaline reuptake inhibitor reboxetine on cortical excitability in healthy humans in a double-blind, placebo-controlled, randomized crossover study. Sixteen subjects were assessed with different transcranial magnetic stimulation measurements: motor thresholds, input-output curve, short-latency intracortical inhibition and intracortical facilitation, I-wave facilitation, and short-interval afferent inhibition before and after placebo or reboxetine (8 mg) single-dose administration. Afterwards, the same subjects took reboxetine (8 mg/d) consecutively for 21 days. During this period (subjects underwent 2 experimental sessions with identical transcranial magnetic stimulation measures under placebo or reboxetine), transcranial magnetic stimulation measurements were assessed before and after drug intake. Results: Both single-dose and chronic administration of reboxetine increased cortical excitability; increased the slope of the input-output curve, intracortical facilitation, and I-wave facilitation; but decreased short-latency intracortical inhibition and short-interval afferent inhibition. Moreover, chronic reboxetine showed a larger enhancement of intracortical facilitation and I-wave facilitation compared with single-dose application. Conclusions: The results show physiological mechanisms of noradrenergic enhancement possibly underlying the functional effects of reboxetine regarding acute and chronic application.

Blend membranes comprising polyetherimide and polyvinyl acetate with improved methane enrichment performance.

A clean and sustainable energy source, biogas is widely accessible worldwide. The caloric value of biogas is related to its methane content, and therefore removal of other gases is essential for reaping the benefits of this cleaner resource. In contrast to other classical techniques, membrane technology is relatively new yet extremely promising for methane enrichment. The methane enrichment performance of polymeric membranes is constrained, hence newer material combinations have been investigated to enhance membrane performance. In this study, blend membranes comprised of polyetherimide (PEI) and polyvinyl acetate (PVAc) in varying proportions were prepared by adopting the wet-phase inversion technique. The generated pure, and blend membranes were characterized for the morphological, thermal, and structural study. The interactions of PEI and PVAc in blend samples were verified by FTIR analysis. On the other hand, SEM investigation indicated that the membranes have an anisotropic porous structure with a dense skin layer at the top. Subsequently, a single glass transition temperature (Tg), as validated by DSC analysis, indicates that the blended polymers are miscible. Furthermore, membranes' performance for gas separation was assessed regarding selectivity and permeance at feed pressures ranging from 2 to 6 bar. The permeation results showed that the CO2 permeance has increased by 40.47% with the addition of 4 wt % PVAc at 2 bar pressure. Furthermore, ideal selectivity improves as the blend ratio increases; nonetheless, the highest value for CO2/CH4 ideal selectivity was attained with a 2 wt % PVAc addition and at 2 bar pressure, which is approximately 26% greater than the pure PEI membrane. At 4 bar pressure, optimum CO2/N2 selectivity value of 22.50 was achieved. The findings indicate that PVAc is an excellent option for expanding the separation performance of blended polymeric membranes for biogas enrichment.

Effect of TiO2 on Thermal, Mechanical, and Gas Separation Performances of Polyetherimide-Polyvinyl Acetate Blend Membranes.

Blend membranes consisting of two polymer pairs improve gas separation, but compromise mechanical and thermal properties. To address this, incorporating titanium dioxide (TiO2) nanoparticles has been suggested, to enhance interactions between polymer phases. Therefore, the objective of this study was to investigate the impact of TiO2 as a filler on the thermal, surface mechanical, as well as gas separation properties of blend membranes. Blend polymeric membranes consisting of polyetherimide (PEI) and polyvinyl acetate (PVAc) with blend ratios of (99:1) and (98:2) were developed via a wet-phase inversion technique. In the latter, TiO2 was incorporated in ratios of 1 and 2 wt.% while maintaining a blend ratio of (98:2). TGA and DSC analyses were used to examine thermal properties, and nano-indentation tests were carried out to ascertain surface mechanical characteristics. On the other hand, a gas permeation set-up was used to determine gas separation performance. TGA tests showed that blend membranes containing TiO2 had better thermal characteristics. Indentation tests showed that TiO2-containing membranes exhibited greater surface hardness compared to other membranes. The results of gas permeation experiments showed that TiO2-containing membranes had better separation characteristics. PEI-PVAc blend membranes with 2 wt.% TiO2 as filler displayed superior separation performance for both gas pairs (CO2/CH4 and CO2/N2). The compatibility between the rubbery and glassy phases of blend membranes was improved as a result of the inclusion of TiO2, which further benefited their thermal, surface mechanical, and gas separation performances.

Optimization of carboxylated graphene oxide (C-GO) content in polymer matrix: Synthesis, characterization, and application study.

Carboxylated graphene oxide (C-GO) embedded in polysulfone (PSF) membrane composites were prepared with different wt. % (i.e., 0.2% M - 1, 0.3% M - 2, 0.4% M - 3, and 0.5% M - 4) using non-solvent induced phase separation (NIPS) method and ultrafiltration assembly was applied for the removal of dye effluents. The optimization of C-GO content into polymer matrix was found influencing factor in determining the composite membranes efficiency and application in various research fields. The membranes were characterized in terms of surface morphology (SEM), crystallinity (XRD), and functional groups identification (FTIR). The water permeability of the developed membranes was analyzed, and it is observed that increasing the content of C-GO in PSF membranes imposed a positive impact on permeation performance. M - 3 was found to be a potential candidate among all the membranes with a maximum water flux of about 183 LMH which is considerably higher as compared to the pristine PSF membrane's water flux (i.e., 27 LMH). Moreover, contact angle measurements of membranes were also checked to assess the hydrophilicity of PSF membranes. The results of contact angle also support the water permeability and efficient correlation was observed as contact angle decreases with increasing the content of C-GO. The minimum contact angle with excellent hydrophilicity was shown by the M - 3 membrane and it was found of about ±58.19° and this value is close to the M - 4 membrane having maximum C-GO content. The photocatalytic performance of the M - 3 membrane was checked under UV-254 nm using methylene blue dye and 97% dye removal was achieved within 220 min of reaction time under neutral pH conditions. The M - 3 membrane having C-GO content of 0.4% was found to be the best membrane with high pure water flux (183 LMH) and efficient dye rejection (82%) capability.

Tuneable molecular selective boron nitride nanosheet ultrafiltration lamellar membrane for dye exclusion to remediate the environment.

Smart tuning of the membrane's porous nanostructures offers an effective strategy for creating state-of-the-art, high-performance separation membranes. In aqueous solution, polyethylene glycol (PEG) grafted boron nitride PEGX-g-(f-BN) nanosheets exhibit high permeance and excellent molecular sieving. The molecular selectivity of the PEGX-g-(f-BN) lamellar membrane is controlled by the nanopores, which can be tuned by modulating the interplanar spacing between the nanosheets. Herein, the interplanar spacing of h-BN nanosheets is enhanced in the range of 0.334-0.348 nm through grafting different molecular weight PEG. Moreover, the grafted PEG instigates a synergistic effect on the nanosheets in two ways. Firstly, through PEG intercalation, the interlayer spacing of the (002) plane could be adjusted without significant deterioration to the hexagonal crystallographic structure. Secondly, intercalated PEG in BN nanosheets reflects in terms of improved h-BN wettability through transformation to hydrophilic surface characteristics (small contact angle of 36-39°). The fabricated PEGX-g-(f-BN) lamellar membrane acquires stable and interconnected nanopores and nanochannels with an average pore diameter of 1.36-2.19 nm. Permeance-exclusion trade-off manipulation through methodical approaches of PEGX-g-(f-BN) decoration thickness and interplanar spacing is exploited to build a better understanding of water transport behavior. PEGX-g-(f-BN) lamellar membranes show unprecedented permeance of ∼1253 L m-2 h-1 bar-1 with a steady methyl blue (MB) exclusion of 98.9% even in different pH conditions.

Current status and future perspectives of proton exchange membranes for hydrogen fuel cells.

The world is on the lookout for sustainable and environmentally benign energy generating systems. Fuel cells (FCs) are regarded as environmentally friendly technology since they address a variety of environmental issues, such as hazardous levels of local pollutants, while also delivering economic advantages owing to their high efficiency. A fuel cell is a device that changes chemical energy contained in fuels (such as hydrogen and methanol) into electrical energy. A wide variety of FCs are commercially available; however, proton exchange membranes for hydrogen fuel cells (PEMFCs) have received overwhelming attention owing to their potential to significantly reduce our energy consumption, pollution emissions, and reliance on fossil fuels. The proton exchange membrane (PEM) is a critical element; it is made of semipermeable polymer and serves as a barrier between the cathode and anode during fuel cell construction. Additionally, membranes function as an insulator between the cathode and anode, facilitating proton exchange and inhibiting electron exchange between the electrodes. Due to the excellent features such as durability and proton conductivity, Nafion membranes are commercially viable and have been in use for a long time. However, Nafion membranes are costly, and their proton exchange capacities degrade over time at higher temperatures and low relative humidity. Other types of membranes have been considered in addition to Nafion membranes. This article discusses the problems connected with several types of PEMs, as well as the strategies adopted to improve their characteristics and performance.

Functionalized organic filler based integrated membranes for environmental remediation.

Mixed matrix membranes (MMMs) are synthesized for efficient CO2 separation released from various anthropogenic sources, which are due to global environmental concerns. The synergetic effect of porous nitrogen-rich, CO2-philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO2 competent. The development of various loadings of porphyrin poly(N-isopropyl Acryl Amide) (P-NIPAM)as functionalized organic fillers (5-20%) in polysulfone (PSU) through solution casting is carried out followed by the various characterizations including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), Fourier Transform Infrared Spectrometer(FT-IR) analysis and pure and mixed gas permeations ranging from 2 to 10 bar feed pressure. Due to both organic species interactions in the matrix, well-distributed fillers and homogenous surfaces, and cross-sectional structures were observed due to π-π interactions and Lewis's basic functionalities. The strong affinity of porous nitrogen-rich and CO2-philic fillers through gas permeation analysis showed high CO2/CH4 and CO2/N2 gas performance that surpassed Robeson's upper bound limit. Comparatively, MMMs showed improved CO2/CH4 permeabilities from 87.5 ± 0.5 Barrer to 88.2 ± 0.9 Barrer than pure polymer matrix. For CO2/N2, CO2 permeabilities improved to 75 ± 0.8 Barrer than pure polymer matrix. For both gas pairs (CO2/CH4, CO2/N2), respective pureselectivities (84%; 86%) and binary selectivities (85% and 85%)were improved. Various theoretical gas permeation models were used to predict CO2 permeabilities for MMMs from which the modified Maxwell-Wagner-Sillar model showed the least AARE% of 0.87. The results showed promising results for efficient CO2 separation due to exceptional functionalized P-PNIPAM affinitive properties. Finally, cost analysis reflected the inflated cost of membranes production for industrial setup using indigenous resources.

Environmental remediation through various composite membranes moieties: Performances and thermomechanical properties.

Pollution harms ecosystems and poses a serious threat to human health around the world through direct or indirect effects on air, water, and land. The importance of remediating effluents is paramount to reducing environmental concerns. CO2 emissions are removed efficiently and efficaciously with mixed matrix membranes (MMMs), which are viable replacements for less efficient and costly membranes. In the field of membrane technology, MMMs are advancing rapidly due to their good separation properties. The selection of filler to be incorporated in mixed matrix membranes is very considered very important. There has been considerable interest in MOFs, carbon nanotubes (CNTs), ionic liquids (ILs), carbon molecular sieves (CMSs), sulfonated fillers (SFs), and layered silicates (LSs) as inorganic fillers for improving the properties of mixed matrix membranes. These fillers promise superb results and long durability for mixed matrix membranes based on them. The purpose of this review is to review different fillers used in MMMs for improving separation properties, limitations, and thermomechanical properties for environmental control and remediation.

A checklist for assessing the methodological quality of concurrent tES-fMRI studies (ContES checklist): a consensus study and statement.

Low-intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation, applies weak electrical stimulation to modulate the activity of brain circuits. Integration of tES with concurrent functional MRI (fMRI) allows for the mapping of neural activity during neuromodulation, supporting causal studies of both brain function and tES effects. Methodological aspects of tES-fMRI studies underpin the results, and reporting them in appropriate detail is required for reproducibility and interpretability. Despite the growing number of published reports, there are no consensus-based checklists for disclosing methodological details of concurrent tES-fMRI studies. The objective of this work was to develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency and reproducibility (ContES checklist). A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists through the International Network of the tES-fMRI Consortium. The process began with a circulation of a preliminary checklist of essential items and additional recommendations, developed by the SC on the basis of a systematic review of 57 concurrent tES-fMRI studies. Contributors were then invited to suggest revisions or additions to the initial checklist. After the revision phase, contributors rated the importance of the 17 essential items and 42 additional recommendations in the final checklist. The state of methodological transparency within the 57 reviewed concurrent tES-fMRI studies was then assessed by using the checklist. Experts refined the checklist through the revision and rating phases, leading to a checklist with three categories of essential items and additional recommendations: (i) technological factors, (ii) safety and noise tests and (iii) methodological factors. The level of reporting of checklist items varied among the 57 concurrent tES-fMRI papers, ranging from 24% to 76%. On average, 53% of checklist items were reported in a given article. In conclusion, use of the ContES checklist is expected to enhance the methodological reporting quality of future concurrent tES-fMRI studies and increase methodological transparency and reproducibility.

The impact of individual electrical fields and anatomical factors on the neurophysiological outcomes of tDCS: A TMS-MEP and MRI study.

BACKGROUND: Transcranial direct current stimulation (tDCS), a neuromodulatory non-invasive brain stimulation technique, has shown promising results in basic and clinical studies. The known interindividual variability of the effects, however, limits the efficacy of the technique. Recently we reported neurophysiological effects of tDCS applied over the primary motor cortex at the group level, based on data from twenty-nine participants who received 15min of either sham, 0.5, 1.0, 1.5 or 2.0 mA anodal, or cathodal tDCS. The neurophysiological effects were evaluated via changes in: 1) transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEP), and 2) cerebral blood flow (CBF) measured by functional magnetic resonance imaging (MRI) via arterial spin labeling (ASL). At the group level, dose-dependent effects of the intervention were obtained, which however displayed interindividual variability. METHOD: In the present study, we investigated the cause of the observed inter-individual variability. To this end, for each participant, a MRI-based realistic head model was designed to 1) calculate anatomical factors and 2) simulate the tDCS- and TMS-induced electrical fields (EFs). We first investigated at the regional level which individual anatomical factors explained the simulated EFs (magnitude and normal component). Then, we explored which specific anatomical and/or EF factors predicted the neurophysiological outcomes of tDCS. RESULTS: The results highlight a significant negative correlation between regional electrode-to-cortex distance (rECD) as well as regional CSF (rCSF) thickness, and the individual EF characteristics. In addition, while both rCSF thickness and rECD anticorrelated with tDCS-induced physiological changes, EFs positively correlated with the effects. CONCLUSION: These results provide novel insights into the dependency of the neuromodulatory effects of tDCS on individual physical factors.

External induction and stabilization of brain oscillations in the human.

BACKGROUND: Neural oscillations in the cerebral cortex are associated with a range of cognitive processes and neuropsychiatric disorders. However, non-invasively modulating oscillatory activity remains technically challenging, due to limited strength, duration, or non-synchronization of stimulation waveforms with endogenous rhythms. OBJECTIVE: We hypothesized that applying controllable phase-synchronized repetitive transcranial magnetic stimulation pulses (rTMS) with alternating currents (tACS) may induce and stabilize neuro-oscillatory resting-state activity at targeted frequencies. METHODS: Using a novel circuit to precisely synchronize rTMS pulses with phase of tACS, we empirically tested whether combined, 10-Hz prefrontal bilateral stimulation could induce and stabilize 10-Hz oscillations in the bilateral prefrontal cortex (PFC). 25 healthy participants took part in a repeated-measures design. Whole-brain resting-state EEG in eyes-open (EO) and eyes-closed (EC) was recorded before (baseline), immediately (1-min), and 15- and 30-min after stimulation. Bilateral, phase-synchronized rTMS aligned to the positive tACS peak was compared with rTMS at tACS trough, with bilateral tACS or rTMS on its own, and to sham. RESULTS: 10-Hz resting-state PFC power increased significantly with peak-synchronized rTMS + tACS (EO: 44.64%, EC: 46.30%, p < 0.05) compared to each stimulation protocol on its own, and sham, with effects spanning between prefrontal and parietal regions and sustaining throughout 30-min. No effects were observed with the sham protocol. Moreover, rTMS timed to the negative tACS trough did not induce local or global changes in oscillations. CONCLUSION: Phase-synchronizing rTMS with tACS may be a viable approach for inducing and stabilizing neuro-oscillatory activity, particularly in scenarios where endogenous oscillatory tone is attenuated, such as disorders of consciousness or major depression.

Development of an extended model for the permeation of environmentally hazardous CO2 gas across asymmetric hollow fiber composite membranes.

This study presents an extended thermodynamic and phenomenological combined model to mitigate the environmental hazardous acid gas over composite membranes. The model has been applied to an acid gas such as carbon dioxide (CO2) for its permeation through polyetherimide incorporated montmorillonite (Mt) nanoparticles hollow fiber asymmetric composite membranes. The well-established non-equilibrium lattice fluid (NELF) model for penetrating low molecular weight penetrant in a glassy polyetherimide (PEI) was extended to incorporate the other important polymer/filler system features such as tortuosity in acid gas diffusion pathways resulted from layered filler aspect ratio and concentration. The model mentioned above predicts the behavior of acid gas in PEI-Mt composite membranes based on thermodynamic characteristics of CO2 and PEI and tortuosity due to Mt. The calculated results are compared to experimentally determined values of CO2 permeability through PEI-Mt composite asymmetric hollow fiber membranes at varying transmembrane pressures and Mt concentrations. A reasonable agreement was found between the model predicted behavior and experimentally determined data in terms of CO2 solubility, Mt concentration and aspect ratio were calculated based on average absolute relative error (%AARE). The proposed modified model efficiently predicts the CO2 permeance across MMMs up to 3 wt% Mt loadings and 6 bar pressure with ± 10%AARE.

Dissociating the causal role of left and right dorsal premotor cortices in planning and executing bimanual movements - A neuro-navigated rTMS study.

BACKGROUND: The dorsal premotor cortex (PMd) is a key region in bimanual coordination. However, causal evidence linking PMd functionality during motor planning and execution to movement quality is lacking. OBJECTIVE: We investigated how left (PMdL) and right PMd (PMdR) are causally involved in planning and executing bimanual movements, using short-train repetitive transcranial magnetic stimulation (rTMS). Additionally, we explored to what extent the observed rTMS-induced modulation of performance could be explained by rTMS-induced modulation of PMd-M1 interhemispheric interactions (IHI). METHODS: Twenty healthy adults (mean age ± SD = 22.85 ± 3.73 years) participated in two sessions, in which either PMdL or PMdR was targeted with rTMS (10 Hz) in a pseudo-randomized design. PMd functionality was transiently modulated during the planning or execution of a complex bimanual task, whereby the participant was asked to track a moving dot by controlling two dials. The effect of rTMS on several performance measures was investigated. Concurrently, rTMS-induced modulation of PMd-M1 IHI was measured using a dual-coil paradigm, and associated with the rTMS-induced performance modulation. RESULTS: rTMS over PMdL during planning increased bilateral hand movement speed (p = 0.03), thereby improving movement accuracy (p = 0.02). In contrast, rTMS over PMdR during both planning and execution induced deterioration of movement stability (p = 0.04). rTMS-induced modulation of PMd-M1 IHI during planning did not predict rTMS-induced performance modulation. CONCLUSION: The current findings support the growing evidence on PMdL dominance during motor planning, as PMdL was crucially involved in planning the speed of each hand, subserving bimanual coordination accuracy. Moreover, the current results suggest that PMdR fulfills a role in continuous adjustment processes of movement.