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1.
Brain Stimul ; 13(3): 804-814, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32289711

RESUMO

BACKGROUND: Neuromodulation by transcranial focused ultrasound (FUS) offers the potential to non-invasively treat specific brain regions, with treatment location verified by magnetic resonance acoustic radiation force imaging (MR-ARFI). OBJECTIVE: To investigate the safety of these methods prior to widespread clinical use, we report histologic findings in two large animal models following FUS neuromodulation and MR-ARFI. METHODS: Two rhesus macaques and thirteen Dorset sheep were studied. FUS neuromodulation was targeted to the primary visual cortex in rhesus macaques and to subcortical locations, verified by MR-ARFI, in eleven sheep. Both rhesus macaques and five sheep received a single FUS session, whereas six sheep received repeated sessions three to six days apart. The remaining two control sheep did not receive ultrasound but otherwise underwent the same anesthetic and MRI procedures as the eleven experimental sheep. Hematoxylin and eosin-stained sections of brain tissue (harvested zero to eleven days following FUS) were evaluated for tissue damage at FUS and control locations as well as tissue within the path of the FUS beam. TUNEL staining was used to evaluate for the presence of apoptosis in sheep receiving high dose FUS. RESULTS: No FUS-related pre-mortem histologic findings were observed in the rhesus macaques or in any of the examined sheep. Extravascular red blood cells (RBCs) were present within the meninges of all sheep, regardless of treatment group. Similarly, small aggregates of perivascular RBCs were rarely noted in non-target regions of neural parenchyma of FUS-treated (8/11) and untreated (2/2) sheep. However, no concurrent histologic abnormalities were observed, consistent with RBC extravasation occurring as post-mortem artifact following brain extraction. Sheep within the high dose FUS group were TUNEL-negative at the targeted site of FUS. CONCLUSIONS: The absence of FUS-related histologic findings suggests that the neuromodulation and MR-ARFI protocols evaluated do not cause tissue damage.

2.
Neuroimage ; 211: 116592, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32014553

RESUMO

Magnetic resonance elastography (MRE) is emerging as a new tool for studying viscoelastic changes in the brain resulting from functional processes. Here, we demonstrate a novel time series method to generate robust functional magnetic resonance elastography (fMRE) activation maps in response to a visual task with a flashing checkerboard stimulus. Using a single-shot spin-echo (SS-SE) pulse sequence, the underlying raw images inherently contain blood-oxygen-level dependent (BOLD) contrast, allowing simultaneous generation of functional magnetic resonance imaging (fMRI) activation maps from the magnitude and functional magnetic resonance elastography (fMRE) maps from the phase. This allows an accurate comparison of the spatially localized stiffness (fMRE) and BOLD (fMRI) changes within a single scan, eliminating confounds inherent in separately acquired scans. Results indicate that tissue stiffness within the visual cortex increases 6-11% with visual stimuli, whereas the BOLD signal change was 1-2%. Furthermore, the fMRE and fMRI activation maps have strong spatial overlap within the visual cortex, providing convincing evidence that fMRE is possible in the brain. However, the fMRE temporal SNR (tSNRfMRE) maps are heterogeneous across the brain. Using a dictionary matching approach to characterize the time series, the viscoelastic changes are consistent with a viscoelastic response function (VRF) time constant of 12.1 â€‹s ± 3.0 â€‹s for a first-order exponential decay, or a shape parameter of 8.1 â€‹s ± 1.4 â€‹s for a gamma-variate.

3.
Neuroimage ; 188: 807-820, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30735828

RESUMO

Recent advances in parallel imaging and simultaneous multi-slice techniques have permitted whole-brain fMRI acquisitions at sub-second sampling intervals, without significantly sacrificing the spatial coverage and resolution. Apart from probing brain function at finer temporal scales, faster sampling rates may potentially lead to enhanced functional sensitivity, owing possibly to both cleaner neural representations (due to less aliased physiological noise) and additional statistical benefits (due to more degrees of freedom for a fixed scan duration). Accompanying these intriguing aspects of fast acquisitions, however, confusion has also arisen regarding (1) how to preprocess/analyze these fast fMRI data, and (2) what exactly is the extent of benefits with fast acquisitions, i.e., how fast is fast enough for a specific research aim? The first question is motivated by the altered spectral distribution and noise characteristics at short sampling intervals, while the second question seeks to reconcile the complicated trade-offs between the functional contrast-to-noise ratio and the effective degrees of freedom. Although there have been recent efforts to empirically approach different aspects of these two questions, in this work we discuss, from a theoretical perspective accompanied by some illustrative, proof-of-concept experimental in vivo human fMRI data, a few considerations that are rarely mentioned, yet are important for both preprocessing and optimizing statistical inferences for studies that employ acquisitions with sub-second sampling intervals. Several summary recommendations include concerns regarding advisability of relying on low-pass filtering to de-noise physiological contributions, employment of statistical models with sufficient complexity to account for the substantially increased serial correlation, and cautions regarding using rapid sampling to enhance functional sensitivity given that different analysis models may associate with distinct trade-offs between contrast-to-noise ratios and the effective degrees of freedom. As an example, we demonstrate that as TR shortens, the intrinsic differences in how noise is accommodated in general linear models and Pearson correlation analyses (assuming Gaussian distributed stochastic signals and noise) can result in quite different outcomes, either gaining or losing statistical power.


Assuntos
Encéfalo/diagnóstico por imagem , Neuroimagem Funcional/métodos , Interpretação de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Modelos Estatísticos , Conectoma/métodos , Conectoma/normas , Neuroimagem Funcional/normas , Humanos , Interpretação de Imagem Assistida por Computador/normas , Processamento de Imagem Assistida por Computador/normas , Imagem por Ressonância Magnética/normas , Projetos de Pesquisa , Fatores de Tempo
4.
Magn Reson Med ; 81(2): 825-838, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30284730

RESUMO

PURPOSE: Simultaneous brain and spinal cord functional MRI is emerging as a new tool to study the central nervous system but is challenging. Poor B0 homogeneity and small size of the spinal cord are principal obstacles to this nascent technology. Here we extend a dynamic shimming approach, first posed by Finsterbusch, by shimming per slice for both the brain and spinal cord. METHODS: We shim dynamically by a simple and fast optimization of linear field gradients and frequency offset separately for each slice in order to minimize off-resonance for both the brain and spinal cord. Simultaneous acquisition of brain and spinal cord fMRI is achieved with high spatial resolution in the spinal cord by means of an echo-planar RF pulse for reduced FOV. Brain slice acquisition is full FOV. RESULTS: T2*-weighted images of brain and spinal cord are acquired with high clarity and minimal observable image artifacts. Fist-clenching fMRI experiments reveal task-consistent activation in motor cortices, cerebellum, and C6-T1 spinal segments. CONCLUSIONS: High quality functional results are obtained for a sensory-motor task. Consistent activation in both the brain and spinal cord is observed at individual levels, not only at group level. Because reduced FOV excitation is applicable to any spinal cord section, future continuation of these methods holds great potential.


Assuntos
Tronco Encefálico/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Imagem por Ressonância Magnética , Medula Espinal/diagnóstico por imagem , Algoritmos , Artefatos , Imagem Ecoplanar , Voluntários Saudáveis , Humanos , Processamento de Imagem Assistida por Computador , Distribuição Normal
5.
Transl Psychiatry ; 8(1): 264, 2018 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504860

RESUMO

Major depressive disorder (MDD) is characterized by the altered integration of reward histories and reduced responding of the striatum. We have posited that this reduced striatal activation in MDD is due to tonically decreased stimulation of striatal dopamine synapses which results in decremented propagation of information along the cortico-striatal-pallido-thalamic (CSPT) spiral. In the present investigation, we tested predictions of this formulation by conducting concurrent functional magnetic resonance imaging (fMRI) and 11C-raclopride positron emission tomography (PET) in depressed and control (CTL) participants. We scanned 16 depressed and 14 CTL participants with simultaneous fMRI and 11C-raclopride PET. We estimated raclopride binding potential (BPND), voxel-wise, and compared MDD and CTL samples with respect to BPND in the striatum. Using striatal regions that showed significant between-group BPND differences as seeds, we conducted whole-brain functional connectivity analysis using the fMRI data and identified brain regions in each group in which connectivity with striatal seed regions scaled linearly with BPND from these regions. We observed increased BPND in the ventral striatum, bilaterally, and in the right dorsal striatum in the depressed participants. Further, we found that as BPND increased in both the left ventral striatum and right dorsal striatum in MDD, connectivity with the cortical targets of these regions (default-mode network and salience network, respectively) decreased. Deficits in stimulation of striatal dopamine receptors in MDD could account in part for the failure of transfer of information up the CSPT circuit in the pathophysiology of this disorder.


Assuntos
Corpo Estriado/metabolismo , Corpo Estriado/fisiopatologia , Transtorno Depressivo Maior/metabolismo , Transtorno Depressivo Maior/fisiopatologia , Dopamina/metabolismo , Adulto , Mapeamento Encefálico , Corpo Estriado/diagnóstico por imagem , Transtorno Depressivo Maior/diagnóstico por imagem , Feminino , Humanos , Imagem por Ressonância Magnética , Masculino , Vias Neurais/diagnóstico por imagem , Vias Neurais/metabolismo , Vias Neurais/fisiopatologia , Tomografia por Emissão de Pósitrons , Racloprida
6.
IEEE Trans Haptics ; 2018 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-29993819

RESUMO

Multilayer electroactive polymer films actuate a small hand-held device that can display tool tip forces during MR-guided interventions. The display produces localized skin stretch at the thumb and index fingertips. Tests confirm that the device does not significantly affect MR imaging and produces detectable stimuli in response to forces measured by a biopsy needle instrumented with optical fibers. Tests with human subjects explored robotic and teleoperated paradigms to detect when the needle contacted a membrane embedded at variable depth in a tissue phantom that approximated the properties of porcine liver. In the first case, naive users detected membranes with a 98.9% success rate as the needle was driven at fixed speed. In the second case, users with experience in needle-based procedures controlled the needle insertion and detected membranes embedded in tissue phantoms with a 98% success rate. In the second experiment, some users detected membranes with very light contact forces, but there was greater subject-to-subject variation.

7.
IEEE Trans Med Imaging ; 37(9): 2060-2069, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29993864

RESUMO

Despite the great promise of integrated positron emission tomography (PET)/magnetic resonance (MR) imaging to add molecular information to anatomical and functional MR, its potential impact in medicine is diminished by a very high cost, limiting its dissemination. An RF-penetrable PET ring that can be inserted into any existing MR system has been developed to address this issue. Employing optical signal transmission along with battery power enables the PET ring insert to electrically float with respect to the MR system. Then, inter-modular gaps of the PET ring allow the RF transmit field from the standard built-in body coil to penetrate into the PET fields-of-view (FOV) with some attenuation that can be compensated for. MR performance, including RF noise, magnetic susceptibility, RF penetrability through and $B_{1}$ uniformity within the PET insert, and MR image quality, were analyzed with and without the PET ring present. The simulated and experimentally measured RF field attenuation factors with the PET ring present were -2.7 and -3.2 dB, respectively. The magnetic susceptibility effect (0.063 ppm) and noise emitted from the PET ring in the MR receive channel were insignificant. $B_{1}$ homogeneity of a spherical agar phantom within the PET ring FOV dropped by 8.4% and MR image SNR was reduced by 3.5 and 4.3 dB with the PET present for gradient-recalled echo and fast-spin echo, respectively. This paper demonstrates, for the first time, an RF-penetrable PET insert comprising a full ring of operating detectors that achieves simultaneous PET/MR using the standard built-in body coil as the RF transmitter.


Assuntos
Imagem por Ressonância Magnética , Imagem Multimodal , Tomografia por Emissão de Pósitrons , Encéfalo/diagnóstico por imagem , Desenho de Equipamento , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética/instrumentação , Imagem por Ressonância Magnética/métodos , Imagem Multimodal/instrumentação , Imagem Multimodal/métodos , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/instrumentação , Tomografia por Emissão de Pósitrons/métodos
8.
J Nucl Med ; 59(1): 167-172, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28747522

RESUMO

The recent introduction of simultaneous whole-body PET/MR scanners has enabled new research taking advantage of the complementary information obtainable with PET and MRI. One such application is kinetic modeling, which requires high levels of PET quantitative stability. To accomplish the required PET stability levels, the PET subsystem must be sufficiently isolated from the effects of MR activity. Performance measurements have previously been published, demonstrating sufficient PET stability in the presence of MR pulsing for typical clinical use; however, PET stability during radiofrequency (RF)-intensive and gradient-intensive sequences has not previously been evaluated for a clinical whole-body scanner. In this work, PET stability of the GE SIGNA PET/MR was examined during simultaneous scanning of aggressive MR pulse sequences. Methods: PET performance tests were acquired with MR idle and during simultaneous MR pulsing. Recent system improvements mitigating RF interference and gain variation were used. A fast recovery fast spin echo MR sequence was selected for high RF power, and an echo planar imaging sequence was selected for its high heat-inducing gradients. Measurements were performed to determine PET stability under varying MR conditions using the following metrics: sensitivity, scatter fraction, contrast recovery, uniformity, count rate performance, and image quantitation. A final PET quantitative stability assessment for simultaneous PET scanning during functional MRI studies was performed with a spiral in-and-out gradient echo sequence. Results: Quantitation stability of a 68Ge flood phantom was demonstrated within 0.34%. Normalized sensitivity was stable during simultaneous scanning within 0.3%. Scatter fraction measured with a 68Ge line source in the scatter phantom was stable within the range of 40.4%-40.6%. Contrast recovery and uniformity were comparable for PET images acquired simultaneously with multiple MR conditions. Peak noise equivalent count rate was 224 kcps at an effective activity concentration of 18.6 kBq/mL, and the count rate curves and scatter fraction curve were consistent for the alternating MR pulsing states. A final test demonstrated quantitative stability during a spiral functional MRI sequence. Conclusion: PET stability metrics demonstrated that PET quantitation was not affected during simultaneous aggressive MRI. This stability enables demanding applications such as kinetic modeling.


Assuntos
Imagem por Ressonância Magnética/métodos , Imagem Multimodal/métodos , Tomografia por Emissão de Pósitrons/métodos , Imagem por Ressonância Magnética/instrumentação , Imagem Multimodal/instrumentação , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/instrumentação , Compostos Radiofarmacêuticos
9.
Hum Brain Mapp ; 38(5): 2454-2465, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28150892

RESUMO

Previous studies of resting state functional connectivity have demonstrated that the default-mode network (DMN) is negatively correlated with a set of brain regions commonly activated during goal-directed tasks. However, the location and extent of anti-correlations are inconsistent across different studies, which has been posited to result largely from differences in whether or not global signal regression (GSR) was applied as a pre-processing step. Notably, coordinates of seed regions-of-interest defined within the posterior cingulate cortex (PCC)/precuneus, an area often employed to study functional connectivity of the DMN, have been inconsistent across studies. Taken together with recent observations that the DMN contains functionally heterogeneous subdivisions, it is presently unclear whether these seeds map to different DMN subnetworks, whose patterns of anti-correlation may differ. If so, then seed location may be a non-negligible factor that, in addition to differences in preprocessing steps, contributes to the inconsistencies reported among published studies regarding DMN correlations/anti-correlations. In this study, they examined anti-correlations of different subnetworks within the DMN during rest using both seed-based and point process analyses, and discovered that: (1) the ventral branch of the DMN (vDMN) yielded significantly weaker anti-correlations than that associated with the dorsal branch of the DMN (dDMN); (2) vDMN anti-correlations introduced by GSR were distinct from dDMN anti-correlations; (3) PCC/precuneus seeds employed by earlier studies mapped to different DMN subnetworks, which may explain some of the inconsistency (in addition to preprocessing steps) in the reported DMN anti-correlations. Hum Brain Mapp 38:2454-2465, 2017. © 2017 Wiley Periodicals, Inc.


Assuntos
Mapeamento Encefálico , Giro do Cíngulo/fisiologia , Modelos Neurológicos , Rede Nervosa/fisiologia , Lobo Parietal/fisiologia , Descanso , Adulto , Feminino , Giro do Cíngulo/diagnóstico por imagem , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Masculino , Movimento (Física) , Oxigênio/sangue , Lobo Parietal/diagnóstico por imagem , Análise de Regressão , Adulto Jovem
10.
Brain Connect ; 7(1): 13-24, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27875902

RESUMO

Recently, emerging studies have demonstrated the existence of brain resting-state spontaneous activity at frequencies higher than the conventional 0.1 Hz. A few groups utilizing accelerated acquisitions have reported persisting signals beyond 1 Hz, which seems too high to be accommodated by the sluggish hemodynamic process underpinning blood oxygen level-dependent contrasts (the upper limit of the canonical model is ∼0.3 Hz). It is thus questionable whether the observed high-frequency (HF) functional connectivity originates from alternative mechanisms (e.g., inflow effects, proton density changes in or near activated neural tissue) or rather is artificially introduced by improper preprocessing operations. In this study, we examined the influence of a common preprocessing step-whole-band linear nuisance regression (WB-LNR)-on resting-state functional connectivity (RSFC) and demonstrated through both simulation and analysis of real dataset that WB-LNR can introduce spurious network structures into the HF bands of functional magnetic resonance imaging (fMRI) signals. Findings of present study call into question whether published observations on HF-RSFC are partly attributable to improper data preprocessing instead of actual neural activities.


Assuntos
Artefatos , Mapeamento Encefálico , Encéfalo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Adulto , Mapeamento Encefálico/métodos , Simulação por Computador , Conjuntos de Dados como Assunto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Redes Neurais de Computação , Vias Neurais/diagnóstico por imagem , Oxigênio/sangue , Razão Sinal-Ruído , Análise Espectral , Adulto Jovem
11.
Neuroimage Clin ; 12: 65-77, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27408791

RESUMO

The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network is an ongoing multi-center collaborative research group established to conduct integrated studies in participants with urologic chronic pelvic pain syndrome (UCPPS). The goal of these investigations is to provide new insights into the etiology, natural history, clinical, demographic and behavioral characteristics, search for new and evaluate candidate biomarkers, systematically test for contributions of infectious agents to symptoms, and conduct animal studies to understand underlying mechanisms for UCPPS. Study participants were enrolled in a one-year observational study and evaluated through a multisite, collaborative neuroimaging study to evaluate the association between UCPPS and brain structure and function. 3D T1-weighted structural images, resting-state fMRI, and high angular resolution diffusion MRI were acquired in five participating MAPP Network sites using 8 separate MRI hardware and software configurations. We describe the neuroimaging methods and procedures used to scan participants, the challenges encountered in obtaining data from multiple sites with different equipment/software, and our efforts to minimize site-to-site variation.


Assuntos
Pesquisa Biomédica/organização & administração , Encéfalo/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética , Imagem por Ressonância Magnética , Vias Neurais/diagnóstico por imagem , Dor Pélvica/diagnóstico por imagem , Adulto , Dor Crônica , Estudos de Coortes , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Oxigênio/sangue , Descanso , Adulto Jovem
12.
Psychiatry Res Neuroimaging ; 249: 91-6, 2016 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-26862057

RESUMO

Neural models of major depressive disorder (MDD) posit that over-response of components of the brain's salience network (SN) to negative stimuli plays a crucial role in the pathophysiology of MDD. In the present proof-of-concept study, we tested this formulation directly by examining the affective consequences of training depressed persons to down-regulate response of SN nodes to negative material. Ten participants in the real neurofeedback group saw, and attempted to learn to down-regulate, activity from an empirically identified node of the SN. Ten other participants engaged in an equivalent procedure with the exception that they saw SN-node neurofeedback indices from participants in the real neurofeedback group. Before and after scanning, all participants completed tasks assessing emotional responses to negative scenes and to negative and positive self-descriptive adjectives. Compared to participants in the sham-neurofeedback group, from pre- to post-training, participants in the real-neurofeedback group showed a greater decrease in SN-node response to negative stimuli, a greater decrease in self-reported emotional response to negative scenes, and a greater decrease in self-reported emotional response to negative self-descriptive adjectives. Our findings provide support for a neural formulation in which the SN plays a primary role in contributing to negative cognitive biases in MDD.


Assuntos
Afeto/fisiologia , Mapeamento Encefálico , Encéfalo/fisiopatologia , Transtorno Depressivo Maior/terapia , Neurorretroalimentação/métodos , Adulto , Transtorno Depressivo Maior/fisiopatologia , Transtorno Depressivo Maior/psicologia , Feminino , Humanos , Imagem por Ressonância Magnética
13.
Behav Brain Res ; 302: 237-51, 2016 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-26772629

RESUMO

The present study aims to examine the relationship between the cortical midline structures (CMS), which have been regarded to be associated with selfhood, and moral decision making processes at the neural level. Traditional moral psychological studies have suggested the role of moral self as the moderator of moral cognition, so activity of moral self would present at the neural level. The present study examined the interaction between the CMS and other moral-related regions by conducting psycho-physiological interaction analysis of functional images acquired while 16 subjects were solving moral dilemmas. Furthermore, we performed Granger causality analysis to demonstrate the direction of influences between activities in the regions in moral decision-making. We first demonstrate there are significant positive interactions between two central CMS seed regions-i.e., the medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC)-and brain regions associated with moral functioning including the cerebellum, brainstem, midbrain, dorsolateral prefrontal cortex, orbitofrontal cortex and anterior insula (AI); on the other hand, the posterior insula (PI) showed significant negative interaction with the seed regions. Second, several significant Granger causality was found from CMS to insula regions particularly under the moral-personal condition. Furthermore, significant dominant influence from the AI to PI was reported. Moral psychological implications of these findings are discussed. The present study demonstrated the significant interaction and influence between the CMS and morality-related regions while subject were solving moral dilemmas. Given that, activity in the CMS is significantly involved in human moral functioning.


Assuntos
Mapeamento Encefálico , Córtex Cerebral/anatomia & histologia , Tomada de Decisões/fisiologia , Princípios Morais , Motivação/fisiologia , Adulto , Córtex Cerebral/fisiologia , Feminino , Humanos , Imageamento Tridimensional , Imagem por Ressonância Magnética , Masculino , Adulto Jovem
14.
Science ; 351(6268): aac9698, 2016 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-26722001

RESUMO

Motivation for reward drives adaptive behaviors, whereas impairment of reward perception and experience (anhedonia) can contribute to psychiatric diseases, including depression and schizophrenia. We sought to test the hypothesis that the medial prefrontal cortex (mPFC) controls interactions among specific subcortical regions that govern hedonic responses. By using optogenetic functional magnetic resonance imaging to locally manipulate but globally visualize neural activity in rats, we found that dopamine neuron stimulation drives striatal activity, whereas locally increased mPFC excitability reduces this striatal response and inhibits the behavioral drive for dopaminergic stimulation. This chronic mPFC overactivity also stably suppresses natural reward-motivated behaviors and induces specific new brainwide functional interactions, which predict the degree of anhedonia in individuals. These findings describe a mechanism by which mPFC modulates expression of reward-seeking behavior, by regulating the dynamical interactions between specific distant subcortical regions.


Assuntos
Anedonia/fisiologia , Corpo Estriado/fisiologia , Neurônios Dopaminérgicos/fisiologia , Motivação , Córtex Pré-Frontal/fisiologia , Recompensa , Animais , Mapeamento Encefálico , Corpo Estriado/citologia , Corpo Estriado/efeitos dos fármacos , Transtorno Depressivo/fisiopatologia , Dopamina/farmacologia , Neurônios Dopaminérgicos/efeitos dos fármacos , Feminino , Imagem por Ressonância Magnética , Masculino , Mesencéfalo/citologia , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/fisiologia , Rede Nervosa/fisiologia , Oxigênio/sangue , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/efeitos dos fármacos , Ratos , Ratos Endogâmicos LEC , Ratos Sprague-Dawley , Esquizofrenia/fisiopatologia
15.
Magn Reson Med ; 75(2): 817-22, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25809723

RESUMO

PURPOSE: Imaging using reduced FOV excitation allows higher resolution or signal-to-noise ratio (SNR) per scan time but often requires long radiofrequency pulses. The goal of this study was to improve a recent reduced field of view (FOV) method that uses a second-order shim gradient to decrease pulse length and evaluate its use in functional MRI (fMRI) applications. THEORY AND METHODS: The method, which was initially limited to excite thin disc-shaped regions at the isocenter, was extended to excite thicker regions off the isocenter and produced accurate excitation profiles on a grid phantom. Visual stimulation fMRI scans were performed with full and reduced FOV. The resolution of the time series images and functional activation maps were assessed using the full-width half-maxima of the autocorrelation functions (FACFs) of the noise images and the activation map values, respectively. RESULTS: The resolution was higher in the reduced FOV time series images (4.1% ± 3.7% FACF reduction, P < 0.02) and functional activation maps (3.1% ± 3.4% FACF reduction, P < 0.01), but the SNR was lower (by 26.5% ± 16.9%). However, for a few subjects, the targeted region could not be localized to the reduced FOV due to the low Z2 gradient strength. CONCLUSION: The results of this study suggest that the proposed method is feasible, though it would benefit from a stronger gradient coil.


Assuntos
Encéfalo/anatomia & histologia , Aumento da Imagem/métodos , Imagem por Ressonância Magnética/métodos , Humanos , Imagens de Fantasmas , Ondas de Rádio , Razão Sinal-Ruído
16.
Neuroimage ; 124(Pt B): 1074-1079, 2016 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-26364863

RESUMO

The Function Biomedical Informatics Research Network (FBIRN) developed methods and tools for conducting multi-scanner functional magnetic resonance imaging (fMRI) studies. Method and tool development were based on two major goals: 1) to assess the major sources of variation in fMRI studies conducted across scanners, including instrumentation, acquisition protocols, challenge tasks, and analysis methods, and 2) to provide a distributed network infrastructure and an associated federated database to host and query large, multi-site, fMRI and clinical data sets. In the process of achieving these goals the FBIRN test bed generated several multi-scanner brain imaging data sets to be shared with the wider scientific community via the BIRN Data Repository (BDR). The FBIRN Phase 1 data set consists of a traveling subject study of 5 healthy subjects, each scanned on 10 different 1.5 to 4 T scanners. The FBIRN Phase 2 and Phase 3 data sets consist of subjects with schizophrenia or schizoaffective disorder along with healthy comparison subjects scanned at multiple sites. In this paper, we provide concise descriptions of FBIRN's multi-scanner brain imaging data sets and details about the BIRN Data Repository instance of the Human Imaging Database (HID) used to publicly share the data.


Assuntos
Bases de Dados Factuais , Informática Médica , Adolescente , Adulto , Idoso , Pesquisa Biomédica , Feminino , Voluntários Saudáveis , Humanos , Disseminação de Informação , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neuroimagem , Transtornos Psicóticos/patologia , Valores de Referência , Pesquisa , Esquizofrenia/patologia , Adulto Jovem
17.
Neuropsychol Rev ; 25(3): 314, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26319138
18.
Neuropsychol Rev ; 25(3): 289-313, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26248581

RESUMO

Since its inception in 1992, Functional Magnetic Resonance Imaging (fMRI) has become an indispensible tool for studying cognition in both the healthy and dysfunctional brain. FMRI monitors changes in the oxygenation of brain tissue resulting from altered metabolism consequent to a task-based evoked neural response or from spontaneous fluctuations in neural activity in the absence of conscious mentation (the "resting state"). Task-based studies have revealed neural correlates of a large number of important cognitive processes, while fMRI studies performed in the resting state have demonstrated brain-wide networks that result from brain regions with synchronized, apparently spontaneous activity. In this article, we review the methods used to acquire and analyze fMRI signals.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Imagem por Ressonância Magnética/métodos , Artefatos , Humanos , Processamento de Imagem Assistida por Computador , Processamento de Sinais Assistido por Computador
19.
J Psychiatr Res ; 68: 91-8, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26228406

RESUMO

Subcortical gray matter regions have been implicated in mood disorders, including Major Depressive Disorder (MDD) and Bipolar Disorder (BD). It is unclear, however, whether or how these regions differ among mood disorders and whether such abnormalities are state- or trait-like. In this study, we examined differences in subcortical gray matter volumes among euthymic BD, MDD, remitted MDD (RMD), and healthy (CTL) individuals. Using automated gray matter segmentation of T1-weighted MRI images, we estimated volumes of 16 major subcortical gray matter structures in 40 BD, 57 MDD, 35 RMD, and 61 CTL individuals. We used multivariate analysis of variance to examine group differences in these structures, and support vector machines (SVMs) to assess individual-by-individual classification. Analyses yielded significant group differences for caudate (p = 0.029) and ventral diencephalon (VD) volumes (p = 0.003). For the caudate, both the BD (p = 0.004) and the MDD (p = 0.037) participants had smaller volumes than did the CTL participants. For the VD, the MDD participants had larger volumes than did the BD and CTL participants (ps < 0.005). SVM distinguished MDD from BD with 59.5% accuracy. These findings indicate that mood disorders are characterized by anomalies in subcortical gray matter volumes and that the caudate and VD contribute uniquely to differential affective pathology. Identifying abnormalities in subcortical gray matter may prove useful for the prevention, diagnosis, and treatment of mood disorders.


Assuntos
Transtorno Bipolar/patologia , Encéfalo/patologia , Transtorno Depressivo Maior/patologia , Adulto , Análise de Variância , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Escalas de Graduação Psiquiátrica
20.
Biomed Opt Express ; 6(3): 1074-89, 2015 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-25798327

RESUMO

Functional near-infrared spectroscopy (fNIRS) is an increasingly popular technology for studying brain function because it is non-invasive, non-irradiating and relatively inexpensive. Further, fNIRS potentially allows measurement of hemodynamic activity with high temporal resolution (milliseconds) and in naturalistic settings. However, in comparison with other imaging modalities, namely fMRI, fNIRS has a significant drawback: limited sensitivity to hemodynamic changes in deep-brain regions. To overcome this limitation, we developed a computational method to infer deep-brain activity using fNIRS measurements of cortical activity. Using simultaneous fNIRS and fMRI, we measured brain activity in 17 participants as they completed three cognitive tasks. A support vector regression (SVR) learning algorithm was used to predict activity in twelve deep-brain regions using information from surface fNIRS measurements. We compared these predictions against actual fMRI-measured activity using Pearson's correlation to quantify prediction performance. To provide a benchmark for comparison, we also used fMRI measurements of cortical activity to infer deep-brain activity. When using fMRI-measured activity from the entire cortex, we were able to predict deep-brain activity in the fusiform cortex with an average correlation coefficient of 0.80 and in all deep-brain regions with an average correlation coefficient of 0.67. The top 15% of predictions using fNIRS signal achieved an accuracy of 0.7. To our knowledge, this study is the first to investigate the feasibility of using cortical activity to infer deep-brain activity. This new method has the potential to extend fNIRS applications in cognitive and clinical neuroscience research.

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