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1.
Environ Sci Technol ; 58(6): 2728-2738, 2024 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-38232385

RESUMO

Understanding geochemical dissolution in porous materials is crucial, especially in applications such as geological CO2 storage. Accurate estimation of reaction rates enhances predictive modeling in geochemical-flow simulations. Fractured porous media, with distinct transport time scales in fractures and the matrix, raise questions about fracture-matrix interface dissolution rates compared to bulk dissolution rate and the scale-dependency of reaction rate averaging. Our investigation delves into these factors, studying the impact of flow rate and mineralogy on interface dissolution patterns. By injecting carbonated water into carbonate rock samples containing a central channel (mimicking fracture hydrodynamics), our study utilized µCT X-ray imaging at 3.3 µm spatial resolution to estimate the reaction rate and capture the change in pore morphology. Results revealed dissolution rates significantly lower (up to 4 orders of magnitude) than batch experiments. Flow rate notably influenced fracture profiles, causing uneven enlargement at low rates and uniform widening at higher ones. Ankerite presence led to a dissolution-altered layer on the fracture surface, showing high permeability and porosity without greatly affecting the dissolution rate, unlike clay-rich carbonates. This research sheds light on controlling factors influencing dissolution in subsurface environments, critical for accurate modeling in diverse applications.


Assuntos
Dióxido de Carbono , Carbonatos , Microtomografia por Raio-X
2.
Hum Brain Mapp ; 44(3): 1278-1282, 2023 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-36399510

RESUMO

Continuous real-time functional magnetic resonance imaging (fMRI) neurofeedback is gaining increasing scientific attention in clinical neuroscience and may benefit from the short repetition times of modern multiband echoplanar imaging sequences. However, minimizing feedback delay can result in technical challenges. Here, we report a technical problem we experienced during continuous fMRI neurofeedback with multiband echoplanar imaging and short repetition times. We identify the possible origins of this problem, describe our current interim solution and provide openly available workflows and code to other researchers in case they wish to use a similar approach.


Assuntos
Imagem Ecoplanar , Neurorretroalimentação , Humanos , Imagem Ecoplanar/métodos , Neurorretroalimentação/métodos , Imageamento por Ressonância Magnética/métodos , Atenção , Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem
3.
Hum Brain Mapp ; 39(7): 3018-3031, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29602255

RESUMO

Brain-computer interfaces provide conscious access to neural activity by means of brain-derived feedback ("neurofeedback"). An individual's abilities to monitor and control feedback are two necessary processes for effective neurofeedback therapy, yet their underlying functional neuroanatomy is still being debated. In this study, healthy subjects received visual feedback from their amygdala response to negative pictures. Activation and functional connectivity were analyzed to disentangle the role of brain regions in different processes. Feedback monitoring was mapped to the thalamus, ventromedial prefrontal cortex (vmPFC), ventral striatum (VS), and rostral PFC. The VS responded to feedback corresponding to instructions while rPFC activity differentiated between conditions and predicted amygdala regulation. Control involved the lateral PFC, anterior cingulate, and insula. Monitoring and control activity overlapped in the VS and thalamus. Extending current neural models of neurofeedback, this study introduces monitoring and control of feedback as anatomically dissociated processes, and suggests their important role in voluntary neuromodulation.


Assuntos
Tonsila do Cerebelo/fisiologia , Emoções/fisiologia , Neuroimagem Funcional/métodos , Neurorretroalimentação/métodos , Reconhecimento Visual de Modelos/fisiologia , Córtex Pré-Frontal/fisiologia , Autocontrole , Tálamo/fisiologia , Estriado Ventral/fisiologia , Adulto , Tonsila do Cerebelo/diagnóstico por imagem , Interfaces Cérebro-Computador , Feminino , Humanos , Imageamento por Ressonância Magnética , Córtex Pré-Frontal/diagnóstico por imagem , Tálamo/diagnóstico por imagem , Estriado Ventral/diagnóstico por imagem , Adulto Jovem
4.
Proc Natl Acad Sci U S A ; 112(16): 5207-12, 2015 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-25848050

RESUMO

Social interactions are fundamental for human behavior, but the quantification of their neural underpinnings remains challenging. Here, we used hyperscanning functional MRI (fMRI) to study information flow between brains of human dyads during real-time social interaction in a joint attention paradigm. In a hardware setup enabling immersive audiovisual interaction of subjects in linked fMRI scanners, we characterize cross-brain connectivity components that are unique to interacting individuals, identifying information flow between the sender's and receiver's temporoparietal junction. We replicate these findings in an independent sample and validate our methods by demonstrating that cross-brain connectivity relates to a key real-world measure of social behavior. Together, our findings support a central role of human-specific cortical areas in the brain dynamics of dyadic interactions and provide an approach for the noninvasive examination of the neural basis of healthy and disturbed human social behavior with minimal a priori assumptions.


Assuntos
Encéfalo/fisiologia , Relações Interpessoais , Imageamento por Ressonância Magnética , Feminino , Humanos , Masculino , Lobo Parietal/fisiologia , Análise de Componente Principal , Reprodutibilidade dos Testes , Lobo Temporal/fisiologia , Adulto Jovem
5.
Neuroimage ; 125: 182-188, 2016 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26481674

RESUMO

Down-regulation of the amygdala with real-time fMRI neurofeedback (rtfMRI NF) potentially allows targeting brain circuits of emotion processing and may involve prefrontal-limbic networks underlying effective emotion regulation. Little research has been dedicated to the effect of rtfMRI NF on the functional connectivity of the amygdala and connectivity patterns in amygdala down-regulation with neurofeedback have not been addressed yet. Using psychophysiological interaction analysis of fMRI data, we present evidence that voluntary amygdala down-regulation by rtfMRI NF while viewing aversive pictures was associated with increased connectivity of the right amygdala with the ventromedial prefrontal cortex (vmPFC) in healthy subjects (N=16). In contrast, a control group (N=16) receiving sham feedback did not alter amygdala connectivity (Group×Condition t-contrast: p<.05 at cluster-level). Task-dependent increases in amygdala-vmPFC connectivity were predicted by picture arousal (ß=.59, p<.05). A dynamic causal modeling analysis with Bayesian model selection aimed at further characterizing the underlying causal structure and favored a bottom-up model assuming predominant information flow from the amygdala to the vmPFC (xp=.90). The results were complemented by the observation of task-dependent alterations in functional connectivity of the vmPFC with the visual cortex and the ventrolateral PFC in the experimental group (Condition t-contrast: p<.05 at cluster-level). Taken together, the results underscore the potential of amygdala fMRI neurofeedback to influence functional connectivity in key networks of emotion processing and regulation. This may be beneficial for patients suffering from severe emotion dysregulation by improving neural self-regulation.


Assuntos
Tonsila do Cerebelo/fisiologia , Emoções/fisiologia , Vias Neurais/fisiologia , Neurorretroalimentação/métodos , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Lobo Límbico/fisiologia , Imageamento por Ressonância Magnética , Córtex Pré-Frontal/fisiologia , Adulto Jovem
6.
Addict Biol ; 21(4): 982-92, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26096546

RESUMO

It has been shown that in alcoholic patients, alcohol-related cues produce increased activation of reward-related brain regions like the ventral striatum (VS), which has been proposed as neurobiological basis of craving. Modulating this activation might be a promising option in the treatment of alcohol addiction. One approach might be real-time functional magnetic resonance imaging neurofeedback (rtfMRI NF). This study was set up to implement and evaluate a rtfMRI approach in a group of non-addicted heavy social drinkers. Thirty-eight heavy drinking students were assigned to a real feedback group (rFB, n = 13), a yoke feedback group (yFB, n = 13) and a passive control group (noFB, n = 12). After conducting a reward task as functional localizer to identify ventral striatal regions, the participants viewed alcohol cues during three NF training blocks in a 3 T MRI scanner. The rFB group received feedback from their own and the yFB from another participants' VS. The noFB group received no feedback. The rFB and the yFB groups were instructed to downregulate the displayed activation. Activation of the VS and prefrontal control regions was compared between the groups. We found significant downregulation of striatal regions specifically in the rFB group. While the rFB and the yFB groups showed significant activation of prefrontal regions during feedback, this activation was only correlated to the reduction of striatal activation in the rFB group. We conclude that rtfMRI NF is a suitable method to reduce striatal activation to alcohol cues. It might be a promising supplement to the treatment of alcoholic patients.


Assuntos
Consumo de Bebidas Alcoólicas/fisiopatologia , Alcoolismo/fisiopatologia , Sinais (Psicologia) , Imageamento por Ressonância Magnética/métodos , Neurorretroalimentação/métodos , Estriado Ventral/fisiopatologia , Adulto , Mapeamento Encefálico/métodos , Fissura/fisiologia , Feminino , Humanos , Masculino , Recompensa , Estriado Ventral/diagnóstico por imagem , Adulto Jovem
7.
Eur Addict Res ; 22(2): 80-9, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26343988

RESUMO

We explored brain volume recovery in terms of cortical thickness (CTh; gyral, sulcal pattern) and surface area (SA), as well as subcortical volume recovery in the first 2 weeks of abstinence in 49 alcohol-dependent patients (ADPs). A widespread reduction of CTh in ADPs at day 1 of abstinence compared to healthy controls, with more pronounced differences in sulci relative to gyri was found. After 2 weeks of abstinence, partial recovery to varying degrees of CTh loss in ADPs was observed for several regions. The longitudinal CTh changes were greater in sulci than in gyri of affected regions. No longitudinal change in SAs and subcortical volumes was found. Alterations of CTh contribute to brain volume loss in alcoholism and recovery during early abstinence. Sulci seem to be more vulnerable to excessive alcohol consumption and to drive abstinence-induced volume recovery. During the initial 2 weeks of abstinence no subcortical volume regain was observed. Either the time span was too short or the lower subcortical volume could represent a predisposing trait marker.


Assuntos
Abstinência de Álcool , Alcoolismo/patologia , Encéfalo/patologia , Córtex Cerebral/patologia , Estudos de Casos e Controles , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neuroimagem , Tamanho do Órgão , Fatores de Tempo
8.
Neural Plast ; 2016: 8240894, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26819776

RESUMO

This study investigated the impact of "life kinetik" training on brain plasticity in terms of an increased functional connectivity during resting-state functional magnetic resonance imaging (rs-fMRI). The training is an integrated multimodal training that combines motor and cognitive aspects and challenges the brain by introducing new and unfamiliar coordinative tasks. Twenty-one subjects completed at least 11 one-hour-per-week "life kinetik" training sessions in 13 weeks as well as before and after rs-fMRI scans. Additionally, 11 control subjects with 2 rs-fMRI scans were included. The CONN toolbox was used to conduct several seed-to-voxel analyses. We searched for functional connectivity increases between brain regions expected to be involved in the exercises. Connections to brain regions representing parts of the default mode network, such as medial frontal cortex and posterior cingulate cortex, did not change. Significant connectivity alterations occurred between the visual cortex and parts of the superior parietal area (BA7). Premotor area and cingulate gyrus were also affected. We can conclude that the constant challenge of unfamiliar combinations of coordination tasks, combined with visual perception and working memory demands, seems to induce brain plasticity expressed in enhanced connectivity strength of brain regions due to coactivation.


Assuntos
Encéfalo/fisiologia , Cognição/fisiologia , Conectoma , Exercício Físico/fisiologia , Rede Nervosa/fisiologia , Adulto , Mapeamento Encefálico , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Memória de Curto Prazo/fisiologia , Pessoa de Meia-Idade
9.
J Neurosci ; 33(36): 14526-33, 2013 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-24005303

RESUMO

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have been used to study the neural correlates of reward anticipation, but the interrelation of EEG and fMRI measures remains unknown. The goal of the present study was to investigate this relationship in response to a well established reward anticipation paradigm using simultaneous EEG-fMRI recording in healthy human subjects. Analysis of causal interactions between the thalamus (THAL), ventral-striatum (VS), and supplementary motor area (SMA), using both mediator analysis and dynamic causal modeling, revealed that (1) THAL fMRI blood oxygenation level-dependent (BOLD) activity is mediating intermodal correlations between the EEG contingent negative variation (CNV) signal and the fMRI BOLD signal in SMA and VS, (2) the underlying causal connectivity network consists of top-down regulation from SMA to VS and SMA to THAL along with an excitatory information flow through a THAL→VS→SMA route during reward anticipation, and (3) the EEG CNV signal is best predicted by a combination of THAL fMRI BOLD response and strength of top-down regulation from SMA to VS and SMA to THAL. Collectively, these findings represent a likely neurobiological mechanism mapping a primarily subcortical process, i.e., reward anticipation, onto a cortical signature.


Assuntos
Antecipação Psicológica , Córtex Cerebral/fisiologia , Rede Nervosa/fisiologia , Recompensa , Tálamo/fisiologia , Adulto , Eletroencefalografia , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino
10.
Neuroimage ; 103: 522-532, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25204866

RESUMO

A tremendous amount of effort has been dedicated to unravel the functional neuroanatomy of the processing and regulation of emotion, resulting in a well-described picture of limbic, para-limbic and prefrontal regions involved. Studies applying functional magnetic resonance imaging (fMRI) often use the block-wise presentation of stimuli with affective content, and conventionally model brain activation as a function of stimulus or task duration. However, there is increasing evidence that regional brain responses may not always translate to task duration and rather show stimulus onset-related transient time courses. We assume that brain regions showing transient responses cannot be detected in block designs using a conventional fMRI analysis approach. At the same time, the probability of detecting these regions with conventional analyses may be increased when shorter stimulus timing or a more intense stimulation during a block is used. In a within-subject fMRI study, we presented aversive pictures to 20 healthy subjects and investigated the effect of experimental design (i.e. event-related and block design) on the detection of brain activation in limbic and para-limbic regions of interest of emotion processing. In addition to conventional modeling of sustained activation during blocks of stimulus presentation, we included a second response function into the general linear model (GLM), suited to detect transient time courses at block onset. In the conventional analysis, several regions like the amygdala, thalamus and periaqueductal gray were activated irrespective of design. However, we found a positive BOLD response in the anterior insula (AI) in event-related but not in block-design analyses. GLM analyses suggest that this difference may result from a transient response pattern which cannot be captured by the conventional fMRI analysis approach. Our results indicate that regions with a transient response profile like the AI can be missed in block designs if analyses do not account for transient responses. This may bias conclusions from empirical reports and meta-analyses towards an underestimation of these regions and their role in emotion and emotion regulation. The cognitive processes underlying differential time courses are discussed.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Emoções/fisiologia , Processamento de Imagem Assistida por Computador/métodos , Adulto , Feminino , Humanos , Imageamento por Ressonância Magnética
11.
Neuroimage ; 94: 349-359, 2014 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-24473101

RESUMO

Inhibitory response control has been extensively investigated in both electrophysiological (ERP) and hemodynamic (fMRI) studies. However, very few multimodal results address the coupling of these inhibition markers. In fMRI, response inhibition has been most consistently linked to activation of the anterior insula and inferior frontal cortex (IFC), often also the anterior cingulate cortex (ACC). ERP work has established increased N2 and P3 amplitudes during NoGo compared to Go conditions in most studies. Previous simultaneous EEG-fMRI imaging reported association of the N2/P3 complex with activation of areas like the anterior midcingulate cortex (aMCC) and anterior insula. In this study we investigated inhibitory control in 23 healthy young adults (mean age=24.7, n=17 for EEG during fMRI) using a combined Flanker/NoGo task during simultaneous EEG and fMRI recording. Separate fMRI and ERP analysis yielded higher activation in the anterior insula, IFG and ACC as well as increased N2 and P3 amplitudes during NoGo trials in accordance with the literature. Combined analysis modelling sequential N2 and P3 effects through joint parametric modulation revealed correlation of higher N2 amplitude with deactivation in parts of the default mode network (DMN) and the cingulate motor area (CMA) as well as correlation of higher central P3 amplitude with activation of the left anterior insula, IFG and posterior cingulate. The EEG-fMRI results resolve the localizations of these sequential activations. They suggest a general role for allocation of attentional resources and motor inhibition for N2 and link memory recollection and internal reflection to P3 amplitude, in addition to previously described response inhibition as reflected by the anterior insula.


Assuntos
Córtex Cerebral/fisiologia , Eletroencefalografia/métodos , Retroalimentação Fisiológica/fisiologia , Inibição Psicológica , Imageamento por Ressonância Magnética/métodos , Movimento/fisiologia , Inibição Neural/fisiologia , Adulto , Atenção/fisiologia , Mapeamento Encefálico/métodos , Feminino , Humanos , Masculino , Imagem Multimodal/métodos , Adulto Jovem
12.
Sci Rep ; 14(1): 9375, 2024 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-38654100

RESUMO

We propose an integrated methodology for the design and fabrication of 3D micromodels that are suitable for the pore-scale study of transport processes in macroporous materials. The micromodels, that bear the pore-scale characteristics of sandstone, such as porosity, mean pore size, etc, are designed following a stochastic reconstruction algorithm that allows for fine-tuning the porosity and the correlation length of the spatial distribution of the solid material. We then construct a series of 3D micromodels at very fine resolution (i.e. 16 µ m) using a state-of-the-art 3D printing infrastructure, specifically a ProJet MJP3600 3D printer, that utilizes the Material Jetting technology. Within the technical constraints of the 3D printer resolution, the fabricated micromodels represent scaled-up replicas of natural sandstones, that are suitable for the study of the scaling between the permeability, the porosity and the mean pore size. The REV- and pore-scale characteristics of the resulting physical micromodels are recovered using a combination of X-ray micro-CT and microfluidic studies. The experimental results are then compared with single-phase flow simulations at pore-scale and geostatistic models in order to determine the effects of the design parameters on the intrinsic permeability and the spatial correlation of the velocity profile. Our numerical and experimental measurements reveal an excellent match between the properties of the designed and fabricated 3D domains, thus demonstrating the robustness of the proposed methodology for the construction of 3D micromodels with fine-tuned and well-controlled pore-scale characteristics. Furthermore, a pore-scale numerical study over a wider range of 3D digital domain realizations reveals a very good match of the measured permeabilities with the predictions of the Kozeny-Carman formulation based on a single control parameter, k 0 , that is found to have a practically constant value for porosities ϕ ≥ 0.2 . This, in turn, enables us to customize the sample size to meet REV constraints, including enlarging pore morphology while considering the Reynolds number. It is also found that at lower porosities there is a significant increase in the fraction of the non-percolating pores, thus leading to different k 0 , as the porosity approaches a numerically determined critical porosity value, ϕ c , where the domain is no longer percolating.

13.
Eur Arch Psychiatry Clin Neurosci ; 263(7): 585-92, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23613000

RESUMO

Evidence suggests that the anterior cingulate cortex (ACC) plays a key role in the development of posttraumatic stress disorder (PTSD). Owing to the region's highly variable patterns, three different studies of PTSD have yielded inconsistent volume reductions. Accordingly, in order to measure the correct borders and volumes, the different patterns of the ACC must be considered separately. We examined 15 victims with chronic symptoms of PTSD, all traumatized at the same accident in 1988, comparing them to 15 matched control subjects. After categorizing the ACC according to single, single segmented, double or double segmented cingulate sulcus (CS), we measured the area with a semi-automated procedure using Brain2 software. Fifty-three percent of our PTSD subjects had single segmented CS compared to 23% in control subjects and 25% in the literature. Furthermore, the four patterns showed differences in mean volume over all subjects of up to 13%. We detected no differences in absolute ACC volumes when differentiating between the patterns or in correlation with brain volumes or clinical parameters. This is the first study to differentiate ACC structure into different patterns in PTSD. We found that one pattern was overrepresented which, in turn, could signal vulnerability to develop PTSD. Because of the remarkable volume differences between patterns, future studies should categorize this highly variable region into different patterns for volumetric measurements. However, future investigations in larger samples should confirm our findings and assess to which extend alterations of ACC patterns may influence the incidence of PTSD.


Assuntos
Giro do Cíngulo/patologia , Transtornos de Estresse Pós-Traumáticos/patologia , Adulto , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão , Transtornos de Estresse Pós-Traumáticos/etiologia
14.
Rev Sci Instrum ; 94(8)2023 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-38065175

RESUMO

An existing open and modular designed micro X-Ray Computed Tomography (µXRCT) system is extended by a test rig in order to combine mechanical and hydro-mechanical experiments with µXRCT characterization. The aim of the system is to cover the complete resolution range of the underlying µXRCT system in combination with a broad load capacity range. A characteristic feature of the developed setup is that it consists mainly of standard components. This makes the shown test rig potentially interesting for other researchers considering extending an existing µXRCT system with an apparatus for mechanical and hydro-mechanical in situ testing. For the load frame, an uniaxial 10 kN universal testing machine with a digital control system was employed, which was extended by two aligned rotational stages. The uniaxial load capacity is ±3.1 kN and can be combined with torque moments of up to ±15 N m both limited by the used rotational stages. The setup is designed in such a way that different x-ray transparent cells (flow cells, oedometer cells, triaxial cells, etc.) can be integrated to generate three-dimensional stress/strain states as required for porous media research. Three applications demonstrate the possible versatile use of the system. As part of these examples, we show how corresponding x-ray transparent cells are designed and implemented. Finally, we discuss the presented approach's technical advantages and disadvantages and suggest improvements.

15.
Brain Behav ; 12(1): e2442, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34878219

RESUMO

INTRODUCTION: Arterial spin labeling (ASL) is a functional neuroimaging technique that has been frequently used to investigate acute pain states. A major advantage of ASL as opposed to blood-oxygen-level-dependent functional neuroimaging is its applicability for low-frequency designs. As such, ASL represents an interesting option for studies in which repeating an experimental event would reduce its ecological validity. Whereas most ASL pain studies so far have used thermal stimuli, to our knowledge, no ASL study so far has investigated pain responses to sharp mechanical pain. METHODS: As a proof of concept, we investigated whether ASL has the sensitivity to detect brain activation within core areas of the nociceptive network in healthy controls following a single stimulation block based on 96 s of mechanical painful stimulation using a blunt blade. RESULTS: We found significant increases in perfusion across many regions of the nociceptive network such as primary and secondary somatosensory cortices, premotor cortex, posterior insula, inferior parietal cortex, parietal operculum, temporal gyrus, temporo-occipital lobe, putamen, and the cerebellum. Contrary to our hypothesis, we did not find any significant increase within ACC, thalamus, or PFC. Moreover, we were able to detect a significant positive correlation between pain intensity ratings and pain-induced perfusion increase in the posterior insula. CONCLUSION: We demonstrate that ASL is suited to investigate acute pain in a single event paradigm, although to detect activation within some regions of the nociceptive network, the sensitivity of our paradigm seemed to be limited. Regarding the posterior insula, our paradigm was sensitive enough to detect a correlation between pain intensity ratings and pain-induced perfusion increase. Previous experimental pain studies have proposed that intensity coding in this region may be restricted to thermal stimulation. Our result demonstrates that the posterior insula encodes intensity information for mechanical stimuli as well.


Assuntos
Circulação Cerebrovascular , Dor , Encéfalo/fisiologia , Circulação Cerebrovascular/fisiologia , Humanos , Imageamento por Ressonância Magnética/métodos , Dor/diagnóstico por imagem , Lobo Parietal/fisiologia , Marcadores de Spin
16.
Sci Adv ; 7(52): eabj0960, 2021 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-34936457

RESUMO

Experimental and field studies reported a significant discrepancy between the cleanup and contamination time scales, while its cause is not yet addressed. Using high-resolution fast synchrotron x-ray computed tomography, we characterized the solute transport in a fully saturated sand packing for both contamination and cleanup processes at similar hydrodynamic conditions. The discrepancy in the time scales has been demonstrated by the nonuniqueness of hydrodynamic dispersion coefficient versus injection rate (Péclet number). Observations show that in the mixed advection-diffusion regime, the hydrodynamic dispersion coefficient of cleanup is significantly larger than that of the contamination process. This nonuniqueness has been attributed to the concentration-dependent diffusion coefficient during the cocurrent and countercurrent advection and diffusion, present in contamination and cleanup processes. The new findings enhance our fundamental understanding of transport processes and improve our capability to estimate the transport time scales of chemicals or pollution in geological and engineering systems.

17.
Hum Brain Mapp ; 31(1): 115-25, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19603410

RESUMO

Recent evidence suggests that deficits of working memory may be a promising neurocognitive endophenotype of bipolar affective disorder. However, little is known about the neurobiological correlates of these deficits. The aim of this study was to determine possible pathophysiological trait markers of bipolar disorder in neural circuits involved in working memory. Functional magnetic resonance imaging was performed in 18 euthymic bipolar patients and 18 matched healthy volunteers using two circuit-specific experimental tasks established by prior systematic neuroimaging studies of working memory. Both euthymic bipolar patients and healthy controls showed working memory-related brain activations that were highly consistent with findings from previous comparable neuroimaging studies in healthy subjects. While these patterns of brain activation were completely preserved in the bipolar patients, only the patients exhibited activation of the right amygdala during the articulatory rehearsal task. In the same task, functional activation in right frontal and intraparietal cortex and in the right cerebellum was significantly enhanced in the patients. These findings indicate that the right amygdala is pathologically activated in euthymic bipolar patients during performance of a circuit-specific working memory task (articulatory rehearsal). This pathophysiological abnormality appears to be a trait marker in bipolar disorders that can be observed even in the euthymic state and that seems to be largely independent of task performance and medication.


Assuntos
Tonsila do Cerebelo/fisiopatologia , Transtorno Bipolar/fisiopatologia , Transtornos da Memória/diagnóstico , Transtornos da Memória/fisiopatologia , Memória de Curto Prazo/fisiologia , Adulto , Biomarcadores , Transtorno Bipolar/complicações , Mapeamento Encefálico , Dominância Cerebral/fisiologia , Feminino , Lateralidade Funcional/fisiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Valor Preditivo dos Testes , Sensibilidade e Especificidade
18.
Rev Sci Instrum ; 91(11): 113102, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-33261434

RESUMO

In this paper, a modular and open micro X-ray Computed Tomography (µXRCT) system is presented, which was set up during the last years at the Institute of Applied Mechanics (CE) of the University of Stuttgart and earlier at the Institute of Computational Engineering of Ruhr-University Bochum. The system is characterized by its intrinsic flexibility resulting from the modular and open design on each level and the opportunity to implement advanced experimental in situ setups. On the one hand, the presented work is intended to support researchers interested in setting up an experimental XRCT system for the microstructural characterization of materials. On the other hand, it aims to support scientists confronted with the decision to set up a system on their own or to buy a commercial scanner. In addition to the presentation of the various hardware components and the applied modular software concept, the technical opportunities of the open and modular hard- and software design are demonstrated by implementing a simple and reliable method for the compensation of bad detector pixels to enhance the raw data quality of the projections. A detailed investigation of the performance of the presented system with regard to the achievable spatial resolution is presented. XRCT datasets of three different applications are finally shown and discussed, demonstrating the wide scope of options of the presented system.


Assuntos
Fenômenos Mecânicos , Microtomografia por Raio-X/instrumentação , Desenho de Equipamento , Imagens de Fantasmas , Software
19.
Behav Brain Res ; 369: 111938, 2019 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-31071348

RESUMO

Receiving feedback from neural activity, dubbed neurofeedback, can reinforce brain self-regulation. In a real-time functional magnetic resonance imaging (fMRI) experiment, healthy participants received amygdala neurofeedback via a visual brain-computer interface. The brain response to signals of reward and failure was modeled. In contrast to previous analyses, we take into account feedback that immediately preceded these signals. That means we tested whether responses were modulated while participants observed sequent reward and failure signals. The orbitofrontal cortex (OFC) showed a negative Blood Oxygenation Level Dependent (BOLD) response to failure signals, when they were preceded by more failure signals. When failure signals were preceded by reward, in contrast, the response was less pronounced. The results suggest weighted processing of neurofeedback value in the OFC. Learning to self-regulate the brain with neurofeedback may involve similar neural networks as the learning of goal-directed action.


Assuntos
Neurorretroalimentação/métodos , Córtex Pré-Frontal/fisiologia , Adulto , Tonsila do Cerebelo/fisiologia , Encéfalo/fisiologia , Mapeamento Encefálico/métodos , Interfaces Cérebro-Computador , Feminino , Voluntários Saudáveis , Humanos , Aprendizagem/fisiologia , Imageamento por Ressonância Magnética/métodos , Reforço Psicológico , Recompensa , Adulto Jovem
20.
Neuroimage Clin ; 24: 102032, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31795041

RESUMO

Real-time functional magnetic resonance imaging (fMRI) neurofeedback training of amygdala hemodynamic activity directly targets a neurobiological mechanism, which contributes to emotion regulation problems in borderline personality disorder (BPD). However, it remains unknown which outcome measures can assess changes in emotion regulation and affective instability, associated with amygdala downregulation in a clinical trial. The current study directly addresses this question. Twenty-four female patients with a DSM-IV BPD diagnosis underwent four runs of amygdala neurofeedback. Before and after the training, as well as at a six-weeks follow-up assessment, participants completed measures of emotion dysregulation and affective instability at diverse levels of analysis (verbal report, clinical interview, ecological momentary assessment, emotion-modulated startle, heart rate variability, and fMRI). Participants were able to downregulate their amygdala blood oxygen-dependent (BOLD) response with neurofeedback. There was a decrease of BPD symptoms as assessed with the Zanarini rating scale for BPD (ZAN-BPD) and a decrease in emotion-modulated startle to negative pictures after training. Further explorative analyses suggest that patients indicated less affective instability, as seen by lower hour-to-hour variability in negative affect and inner tension in daily life. If replicated by an independent study, our results imply changes in emotion regulation and affective instability for several systems levels, including behavior and verbal report. Conclusions are limited due to the lack of a control group. A randomized controlled trial (RCT) will be needed to confirm effectiveness of the training.


Assuntos
Transtorno da Personalidade Borderline/diagnóstico por imagem , Transtorno da Personalidade Borderline/psicologia , Emoções , Neurorretroalimentação/métodos , Adulto , Tonsila do Cerebelo/diagnóstico por imagem , Regulação Emocional , Feminino , Humanos , Imageamento por Ressonância Magnética , Testes Neuropsicológicos , Estimulação Luminosa , Escalas de Graduação Psiquiátrica , Reflexo de Sobressalto , Autoavaliação (Psicologia)
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