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1.
Neuroimage ; : 118745, 2021 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-34808364

RESUMO

Temporal modulations in the envelope of acoustic waveforms at rates around 4 Hz constitute a strong acoustic cue in speech and other natural sounds. It is often assumed that the ascending auditory pathway is increasingly sensitive to slow amplitude modulation (AM), but sensitivity to AM is typically considered separately for individual stages of the auditory system. Here, we used blood oxygen level dependent (BOLD) fMRI in twenty human subjects (10 male) to measure sensitivity of regional neural activity in the auditory system to 4 Hz temporal modulations. Participants were exposed to AM noise stimuli varying parametrically in modulation depth to characterize modulation-depth effects on BOLD responses. A Bayesian hierarchical modeling approach was used to model potentially nonlinear relations between AM depth and group-level BOLD responses in auditory regions of interest (ROIs). Sound stimulation activated the auditory brainstem and cortex structures in single subjects. BOLD responses to noise exposure in core and belt auditory cortices scaled positively with modulation depth. This finding was corroborated by whole-brain cluster-level inference. Sensitivity to AM depth variations was particularly pronounced in the Heschl's gyrus but also found in higher-order auditory cortical regions. None of the sound-responsive subcortical auditory structures showed a BOLD response profile that reflected the parametric variation in AM depth. The results are compatible with the notion that early auditory cortical regions play a key role in processing low-rate modulation content of sounds in the human auditory system.

2.
J Magn Reson ; 333: 107103, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34801822

RESUMO

PURPOSE: MRI can be utilized for quantitative characterization of tissue. To assess e.g. water fractions or diffusion coefficients for compartments in the brain, a decomposition of the signal is necessary. Imposing standard models carries the risk of estimating biased parameters if model assumptions are violated. This work introduces a data-driven multicomponent analysis, the monotonous slope non-negative matrix factorization (msNMF), tailored to extract data features expected in MR signals. METHODS: The msNMF was implemented by extending the standard NMF with monotonicity constraints on the signal profiles and their first derivatives. The method was validated using simulated data, and subsequently applied to both ex vivo DWI data and in vivo relaxometry data. Reproducibility of the method was tested using the latter. RESULTS: The msNMF recovered the multi-exponential signals in the simulated data and showed superiority to standard NMF (based on the explained variance, area under the ROC curve, and coefficient of variation). Diffusion components extracted from the DWI data reflected the cell density of the underlying tissue. The relaxometry analysis resulted in estimates of edema water fractions (EWF) highly correlated with published results, and demonstrated acceptable reproducibility. CONCLUSION: The msNMF can robustly separate MR signals into components with relation to the underlying tissue composition, and may potentially be useful for e.g. tumor tissue characterization.

3.
PLoS Comput Biol ; 17(9): e1009217, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34499635

RESUMO

Ergodicity describes an equivalence between the expectation value and the time average of observables. Applied to human behaviour, ergodic theories of decision-making reveal how individuals should tolerate risk in different environments. To optimize wealth over time, agents should adapt their utility function according to the dynamical setting they face. Linear utility is optimal for additive dynamics, whereas logarithmic utility is optimal for multiplicative dynamics. Whether humans approximate time optimal behavior across different dynamics is unknown. Here we compare the effects of additive versus multiplicative gamble dynamics on risky choice. We show that utility functions are modulated by gamble dynamics in ways not explained by prevailing decision theories. Instead, as predicted by time optimality, risk aversion increases under multiplicative dynamics, distributing close to the values that maximize the time average growth of in-game wealth. We suggest that our findings motivate a need for explicitly grounding theories of decision-making on ergodic considerations.

4.
Artigo em Inglês | MEDLINE | ID: mdl-34282469

RESUMO

Empathy is the ability to generate emotional responses (i.e., cognitive empathy) and to make cognitive inferences (i.e., affective empathy) to other people's emotions. Empirical evidence suggests that patients with bipolar disorder (BD) exhibit impairment in cognitive empathy, but findings on affective empathy are inconsistent. Few studies have examined the neural mechanisms of cognitive and affective empathy in patients with BD. In this study, we examined the empathy-related resting-state functional connectivity (rsFC) in BD patients. Thirty-seven patients with BD and 42 healthy controls completed the self-report Questionnaires of Cognitive and Affective Empathy (QCAE), the Yoni behavioural task, and resting-sate fMRI brain scans. Group comparison of empathic ability was conducted. The interactions between group and empathic ability on seed-based whole brain rsFC were examined. BD patients scored lower on the Online Simulation subscale of the QCAE and showed positive correlations between cognitive empathy and the rsFC of the dorsal Medial Prefrontal Cortex (dmPFC) with the lingual gyrus. The correlations between cognitive empathy and the rsFC of the temporal-parietal junction (TPJ) with the fusiform gyrus, the cerebellum and the parahippocampus were weaker in BD patients than that in healthy controls. These findings highlight the underlying neural mechanisms of empathy impairments in BD patients.

5.
Neuroimage ; 237: 118093, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-33940146

RESUMO

The experimental manipulation of neural activity by neurostimulation techniques overcomes the inherent limitations of correlative recordings, enabling the researcher to investigate causal brain-behavior relationships. But only when stimulation and recordings are combined, the direct impact of the stimulation on neural activity can be evaluated. In humans, this can be achieved non-invasively through the concurrent combination of transcranial magnetic stimulation (TMS) with functional magnetic resonance imaging (fMRI). Concurrent TMS-fMRI allows the assessment of the neurovascular responses evoked by TMS with excellent spatial resolution and full-brain coverage. This enables the functional mapping of both local and remote network effects of TMS in cortical as well as deep subcortical structures, offering unique opportunities for basic research and clinical applications. The purpose of this review is to introduce the reader to this powerful tool. We will introduce the technical challenges and state-of-the art solutions and provide a comprehensive overview of the existing literature and the available experimental approaches. We will highlight the unique insights that can be gained from concurrent TMS-fMRI, including the state-dependent assessment of neural responsiveness and inter-regional effective connectivity, the demonstration of functional target engagement, and the systematic evaluation of stimulation parameters. We will also discuss how concurrent TMS-fMRI during a behavioral task can help to link behavioral TMS effects to changes in neural network activity and to identify peripheral co-stimulation confounds. Finally, we will review the use of concurrent TMS-fMRI for developing TMS treatments of psychiatric and neurological disorders and suggest future improvements for further advancing the application of concurrent TMS-fMRI.


Assuntos
Mapeamento Encefálico/métodos , Imageamento por Ressonância Magnética/métodos , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/fisiologia , Acoplamento Neurovascular/fisiologia , Estimulação Magnética Transcraniana/métodos , Humanos
6.
PLoS One ; 16(4): e0243899, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33826633

RESUMO

Phasic dopamine release from mid-brain dopaminergic neurons is thought to signal errors of reward prediction (RPE). If reward maximisation is to maintain homeostasis, then the value of primary rewards should be coupled to the homeostatic errors they remediate. This leads to the prediction that RPE signals should be configured as a function of homeostatic state and thus diminish with the attenuation of homeostatic error. To test this hypothesis, we collected a large volume of functional MRI data from five human volunteers on four separate days. After fasting for 12 hours, subjects consumed preloads that differed in glucose concentration. Participants then underwent a Pavlovian cue-conditioning paradigm in which the colour of a fixation-cross was stochastically associated with the delivery of water or glucose via a gustometer. This design afforded computation of RPE separately for better- and worse-than expected outcomes during ascending and descending trajectories of serum glucose fluctuations. In the parabrachial nuclei, regional activity coding positive RPEs scaled positively with serum glucose for both ascending and descending glucose levels. The ventral tegmental area and substantia nigra became more sensitive to negative RPEs when glucose levels were ascending. Together, the results suggest that RPE signals in key brainstem structures are modulated by homeostatic trajectories of naturally occurring glycaemic flux, revealing a tight interplay between homeostatic state and the neural encoding of primary reward in the human brain.


Assuntos
Glicemia/metabolismo , Dopamina/metabolismo , Núcleos Parabraquiais , Recompensa , Substância Negra , Área Tegmentar Ventral , Adulto , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Núcleos Parabraquiais/diagnóstico por imagem , Núcleos Parabraquiais/metabolismo , Substância Negra/diagnóstico por imagem , Substância Negra/metabolismo , Área Tegmentar Ventral/diagnóstico por imagem , Área Tegmentar Ventral/metabolismo
7.
Cogn Neuropsychiatry ; 26(3): 166-182, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33706673

RESUMO

INTRODUCTION: Effort-reward imbalance (ERI) is a typical psychosocial stress. Schizotypal traits are attenuated features of schizophrenia in the general population. According to the diathesis-stress model, schizotypal traits and psychosocial stress contribute to the onset of schizophrenia. However, few studies examined the effects of these factors on brain alterations. This study aimed to examine relationships between ERI, schizotypal traits and brain structures and functions. METHODS: We recruited 37 (13 male, 24 female) participants with high levels of schizotypal traits and 36 (12 male, 24 female) participants with low levels of schizotypal traits by the Schizotypal Personality Questionnaire (SPQ). The Chinese school version of the effort-reward imbalance questionnaire (C-ERI-S) was used to measure ERI. We conducted the voxel-based morphometry (VBM) and whole brain resting-state functional connectivity (rsFC) analysis using reward or stress-related regions as seeds. RESULTS: Participants with high levels of schizotypal traits were more likely to perceive ERI. The severity of ERI was correlated with grey matter volume (GMV) reduction of the left pallidum and altered rsFC among the prefrontal, striatum and cerebellum in participants with high levels of schizotypal traits. CONCLUSION: ERI is associated with GMV reduction and altered rsFC in individuals with high levels of schizotypal traits.


Assuntos
Recompensa , Transtorno da Personalidade Esquizotípica , Encéfalo/diagnóstico por imagem , Córtex Cerebral , Feminino , Humanos , Masculino , Personalidade , Inquéritos e Questionários
8.
Front Neurol ; 11: 800, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33013616

RESUMO

Introduction: Diffuse traumatic axonal injury (TAI) is one of the key mechanisms leading to impaired consciousness after severe traumatic brain injury (TBI). In addition, preferential regional expression of TAI in the brain may also influence clinical outcome. Aim: We addressed the question whether the regional expression of microstructural changes as revealed by whole-brain diffusion tensor imaging (DTI) in the subacute stage after severe TBI may predict the duration of post-traumatic amnesia (PTA). Method: Fourteen patients underwent whole-brain DTI in the subacute stage after severe TBI. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for five bilateral brain regions: fronto-temporal, parieto-occipital, and midsagittal hemispheric white matter, as well as brainstem and basal ganglia. Region-specific calculation of mean FA and MD only considered voxels that showed no tissue damage, using an exclusive mask with all voxels that belonged to local brain lesions or microbleeds. Mean FA or MD of the five brain regions were entered in separate partial least squares (PLS) regression analyses to identify patterns of regional microstructural changes that account for inter-individual variations in PTA. Results: For FA, PLS analysis revealed two spatial patterns that significantly correlated with individual PTA. The lower the mean FA values in all five brain regions, the longer that PTA lasted. A pattern characterized by lower FA values in the deeper brain regions relative to the FA values in the hemispheric regions also correlated with longer PTA. Similar trends were found for MD, but opposite in sign. The spatial FA changes as revealed by PLS components predicted the duration of PTA. Individual PTA duration, as predicted by a leave-one-out cross-validation analysis, correlated with true PTA values (Spearman r = 0.68, p permutation = 0.008). Conclusion: Two coarse spatial patterns of microstructural damage, indexed as reduction in FA, were relevant to recovery of consciousness after TBI. One pattern expressed was consistent with diffuse microstructural damage across the entire brain. A second pattern was indicative of a preferential damage of deep midline brain structures.

9.
Sci Rep ; 10(1): 13189, 2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32764639

RESUMO

Research in primates and rodents ascribes the striatum a critical role in integrating elementary movements into unitary action sequences through reinforcement-based learning. Yet it remains to be shown whether the human striatum represents action sequence-specific information. Young right-handed volunteers underwent functional magnetic resonance imaging while they performed four discrete finger sequences with their right hand, consisting of five button presses. Specific finger sequences could be discriminated based on the distributed activity patterns in left and right striatum, but not by average differences in single-voxel activity. Multiple bilateral clusters in putamen and caudate nucleus belonging to motor, associative, parietal and limbic territories contributed to classification sensitivity. The results show that individual finger movement sequences are widely represented in human striatum, supporting functional integration rather than segregation. The findings are compatible with the idea that the basal ganglia simultaneously integrate motor, associative and limbic aspects in the control of complex overlearned behaviour.


Assuntos
Dedos/fisiologia , Movimento , Neostriado/fisiologia , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Neostriado/diagnóstico por imagem , Adulto Jovem
10.
Neuroimage Clin ; 28: 102362, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32798910

RESUMO

BACKGROUND: Parkinson's disease is associated with severe nigro-striatal dopamine depletion, leading to motor dysfunction and altered reward processing. We previously showed that drug-naïve patients with Parkinson's disease had a consistent attenuation of reward signalling in the mesolimbic and mesocortical system. Here, we address the neurobiological effects of dopaminergic therapy on reward sensitivity in the mesolimbic circuitry, and how this may contribute to neuropsychiatric symptoms. OBJECTIVES: We tested the hypothesis that (1) dopaminergic treatment would restore the attenuated, mesolimbic and mesocortical responses to reward; and (2) restoration of reward responsivity by dopaminergic treatment would predict motor performance and the emergence of impulse control symptoms. METHODS: In 11 drug-naïve Parkinson patients, we prospectively assessed treatment-induced changes in reward processing before, and eight weeks after initiation of monotherapy with dopamine agonists. They were compared to 10 non-medicated healthy controls who were also measured longitudinally. We used whole-brain functional magnetic resonance imaging at 3 Tesla to assess the reward responsivity of the brain to monetary gains and losses, while participants performed a simple consequential gambling task. RESULTS: In patients, dopaminergic treatment improved clinical motor symptoms without significantly changing task performance. Dopamine agonist therapy induced a stronger reward responsivity in the right hippocampus with higher doses being less effective. None of the patients developed impulse control disorders in the follow-up period of four years. CONCLUSIONS: Short-term treatment with first-ever dopaminergic medication partially restores deficient reward-related processing in the hippocampus in de novo Parkinson's disease.


Assuntos
Agonistas de Dopamina , Jogo de Azar , Doença de Parkinson , Agonistas de Dopamina/uso terapêutico , Feminino , Hipocampo/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/tratamento farmacológico , Doença de Parkinson/fisiopatologia , Recompensa
11.
Neuroimage Clin ; 27: 102330, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32688307

RESUMO

Dopaminergic treatment may impair the ability to suppress impulsive behaviours in patients with Parkinson's disease, triggering impulse control disorders. It is unclear how dopaminergic medication affects the neural networks that contribute to withholding inappropriate actions. To address this question, we mapped task-related brain activity with whole-brain functional magnetic resonance imaging at 3 Tesla in 26 patients with Parkinson's disease. Patients performed a sequential gambling task while being ON and OFF their regular dopaminergic treatment. During a gambling round, patients repeatedly decided between the option to continue with gambling and accumulate more monetary reward under increasing risk or the option to bank the current balance and start a new round. 13 patients had an impulse control disorder (ICD + group). These patients did not differ in risk-taking attitude during sequential gambling from 13 patients without impulse control disorder (ICD - group), but they displayed differences in gambling-related activity in cortico-subcortical brain areas supporting inhibitory control. First, the ICD + group showed reduced "continue-to-gamble" activity in right inferior frontal gyrus and subthalamic nucleus. Second, the individual risk-attitude scaled positively with "continue-to-gamble" activity in right subthalamic nucleus and striatum in the ICD - group only. Third, ICD + patients differed in their functional neural responses to dopaminergic treatment from ICD - patients: dopaminergic therapy reduced functional connectivity between inferior frontal gyrus and subthalamic nucleus during "continue-to-gamble" decisions and attenuated striatal responses towards accumulating reward and risk. Together, the medication-independent (trait) and medication-related (state) differences in neural activity may set a permissive stage for the emergence of impulse control disorders during dopamine replacement therapy in Parkinson's disease.


Assuntos
Transtornos Disruptivos, de Controle do Impulso e da Conduta , Jogo de Azar , Doença de Parkinson , Núcleo Subtalâmico , Encéfalo/diagnóstico por imagem , Transtornos Disruptivos, de Controle do Impulso e da Conduta/induzido quimicamente , Humanos , Doença de Parkinson/tratamento farmacológico
12.
Neuroimage ; 219: 117044, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32534963

RESUMO

Transcranial brain stimulation (TBS) has been established as a method for modulating and mapping the function of the human brain, and as a potential treatment tool in several brain disorders. Typically, the stimulation is applied using a one-size-fits-all approach with predetermined locations for the electrodes, in electric stimulation (TES), or the coil, in magnetic stimulation (TMS), which disregards anatomical variability between individuals. However, the induced electric field distribution in the head largely depends on anatomical features implying the need for individually tailored stimulation protocols for focal dosing. This requires detailed models of the individual head anatomy, combined with electric field simulations, to find an optimal stimulation protocol for a given cortical target. Considering the anatomical and functional complexity of different brain disorders and pathologies, it is crucial to account for the anatomical variability in order to translate TBS from a research tool into a viable option for treatment. In this article we present a new method, called CHARM, for automated segmentation of fifteen different head tissues from magnetic resonance (MR) scans. The new method compares favorably to two freely available software tools on a five-tissue segmentation task, while obtaining reasonable segmentation accuracy over all fifteen tissues. The method automatically adapts to variability in the input scans and can thus be directly applied to clinical or research scans acquired with different scanners, sequences or settings. We show that an increase in automated segmentation accuracy results in a lower relative error in electric field simulations when compared to anatomical head models constructed from reference segmentations. However, also the improved segmentations and, by implication, the electric field simulations are affected by systematic artifacts in the input MR scans. As long as the artifacts are unaccounted for, this can lead to local simulation differences up to 30% of the peak field strength on reference simulations. Finally, we exemplarily demonstrate the effect of including all fifteen tissue classes in the field simulations against the standard approach of using only five tissue classes and show that for specific stimulation configurations the local differences can reach 10% of the peak field strength.


Assuntos
Encéfalo/diagnóstico por imagem , Cabeça/diagnóstico por imagem , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética/métodos , Encéfalo/fisiologia , Mapeamento Encefálico/métodos , Simulação por Computador , Eletroencefalografia , Cabeça/fisiologia , Humanos , Magnetoencefalografia , Estimulação Transcraniana por Corrente Contínua , Estimulação Magnética Transcraniana
13.
Chronic Stress (Thousand Oaks) ; 4: 2470547020917623, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32518887

RESUMO

Background: Symptoms of anhedonia are often central to posttraumatic stress disorder (PTSD), but it is unclear how anhedonia is affected by processes induced by reliving past traumatic memories. Methods: Sixty-nine male refugees (PTSD = 38) were interviewed and scanned with functional magnetic resonance imaging while viewing positive, neutral and Scrambled Pictures after being read personalized scripts evoking an emotionally neutral memory and a traumatic memory. We further measured postprovocation state symptoms, physiological measures and PTSD symptoms. We tested whether neural activity associated with positive picture viewing in participants with PTSD was differentially affected by symptom provocation compared to controls. Results: For the pictures > scrambled contrast (Positive contrast), PTSD participants had significantly less activity than controls in fusiform gyrus, right inferior temporal gyrus and left middle occipital gyrus. The Positive contrast activity in fusiform gyrus scaled negatively with anhedonia symptoms in PTSD participants after controlling for total PTSD severity. Relative to the emotionally Neutral Script, the Trauma Script decreased positive picture viewing activity in posterior cingulate cortex, precuneus and left calcarine gyrus, but there was no difference between PTSD participants and controls. Conclusions: We found reduced responsiveness of higher visual processing of emotionally positive pictures in PTSD. The significant correlation found between positive picture viewing activity and anhedonia suggests the reduced responsiveness to be due to the severity of anhedonia.

14.
Hum Brain Mapp ; 41(1): 172-184, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31571320

RESUMO

Machine learning has increasingly been applied to classification of schizophrenia in neuroimaging research. However, direct replication studies and studies seeking to investigate generalizability are scarce. To address these issues, we assessed within-site and between-site generalizability of a machine learning classification framework which achieved excellent performance in a previous study using two independent resting-state functional magnetic resonance imaging data sets collected from different sites and scanners. We established within-site generalizability of the classification framework in the main data set using cross-validation. Then, we trained a model in the main data set and investigated between-site generalization in the validated data set using external validation. Finally, recognizing the poor between-site generalization performance, we updated the unsupervised algorithm to investigate if transfer learning using additional unlabeled data were able to improve between-site classification performance. Cross-validation showed that the published classification procedure achieved an accuracy of 0.73 using majority voting across all selected components. External validation found a classification accuracy of 0.55 (not significant) and 0.70 (significant) using the direct and transfer learning procedures, respectively. The failure of direct generalization from one site to another demonstrates the limitation of within-site cross-validation and points toward the need to incorporate efforts to facilitate application of machine learning across multiple data sets. The improvement in performance with transfer learning highlights the importance of taking into account the properties of data when constructing predictive models across samples and sites. Our findings suggest that machine learning classification result based on a single study should be interpreted cautiously.


Assuntos
Conectoma/métodos , Imageamento por Ressonância Magnética/métodos , Esquizofrenia/diagnóstico por imagem , Esquizofrenia/fisiopatologia , Aprendizado de Máquina não Supervisionado , Adulto , Conectoma/normas , Feminino , Humanos , Imageamento por Ressonância Magnética/normas , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Aprendizado de Máquina não Supervisionado/normas
15.
J Neurotrauma ; 37(4): 581-592, 2020 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-31588844

RESUMO

Severe traumatic brain injury (TBI) produces shearing forces on long-range axons and brain vessels, causing axonal and vascular injury. To examine whether microbleeds and axonal injury colocalize after TBI, we performed whole-brain susceptibility-weighted imaging (SWI) and diffusion tensor imaging (DTI) in 14 patients during the subacute phase after severe TBI. SWI was used to determine the number and volumes of microbleeds in five brain regions: the frontotemporal lobe; parieto-occipital lobe; midsagittal region (cingular cortex, parasagittal white matter, and corpus callosum); deep nuclei (basal ganglia and thalamus); and brainstem. Averaged fractional anisotropy (FA) and mean diffusivity (MD) were measured to assess microstructural changes in the normal appearing white matter attributed to axonal injury in the same five regions. Regional expressions of microbleeds and microstructure were used in a partial least-squares model to predict the impairment of consciousness in the subacute stage after TBI as measured with the Coma Recovery Scale-Revised (CRS-R). Only in the midsagittal region, the expression of microbleeds was correlated with regional changes in microstructure as revealed by DTI. Microbleeds and microstructural DTI-based metrics of deep, but not superficial, brain regions were able to predict individual CRS-R. Our results suggest that microbleeds are not strictly related to axonal pathology in other than the midsagittal region. While each measure alone was predictive, the combination of both metrics scaled best with individual CRS-R. Structural alterations in deep brain structures are relevant in terms of determining the severity of impaired consciousness in the acute stage after TBI.


Assuntos
Lesões Encefálicas Traumáticas/diagnóstico por imagem , Hemorragia Cerebral/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Adolescente , Adulto , Idoso , Lesões Encefálicas Traumáticas/patologia , Hemorragia Cerebral/patologia , Imagem de Tensor de Difusão , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Substância Branca/patologia , Adulto Jovem
16.
Neuroimage ; 208: 116431, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31816421

RESUMO

Comparing electric field simulations from individualized head models against in-vivo intra-cranial recordings is considered the gold standard for direct validation of computational field modeling for transcranial brain stimulation and brain mapping techniques such as electro- and magnetoencephalography. The measurements also help to improve simulation accuracy by pinning down the factors having the largest influence on the simulations. Here we compare field simulations from four different automated pipelines against intracranial voltage recordings in an existing dataset of 14 epilepsy patients. We show that modeling differences in the pipelines lead to notable differences in the simulated electric field distributions that are often large enough to change the conclusions regarding the dose distribution and strength in the brain. Specifically, differences in the automatic segmentations of the head anatomy from structural magnetic resonance images are a major factor contributing to the observed field differences. However, the differences in the simulated fields are not reflected in the comparison between the simulations and intra-cranial measurements. This apparent mismatch is partly explained by the noisiness of the intra-cranial measurements, which renders comparisons between the methods inconclusive. We further demonstrate that a standard regression analysis, which ignores uncertainties in the simulations, leads to a strong bias in the estimated linear relationship between simulated and measured fields. Ignoring this bias leads to the incorrect conclusion that the models systematically misestimate the field strength in the brain. We propose a new Bayesian regression analysis of the data that yields unbiased parameter estimates, along with their uncertainties, and gives further insights to the fit between simulations and measurements. Specifically, the unbiased results give only weak support for systematic misestimations of the fields by the models.


Assuntos
Encéfalo , Eletrocorticografia , Modelos Teóricos , Neuroimagem , Estimulação Transcraniana por Corrente Contínua , Adulto , Teorema de Bayes , Encéfalo/anatomia & histologia , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Eletrocorticografia/normas , Epilepsia/diagnóstico , Humanos , Imageamento por Ressonância Magnética , Neuroimagem/normas , Análise de Regressão , Estimulação Transcraniana por Corrente Contínua/normas , Estudos de Validação como Assunto
17.
Front Neurosci ; 13: 1246, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31824247

RESUMO

A core symptom of mood disorders is cognitive impairment in attention, memory and executive functions. Erythropoietin (EPO) is a candidate treatment for cognitive impairment in unipolar and bipolar disorders (UD and BD) and modulates cognition-related neural activity across a fronto-temporo-parietal network. This report investigates predicting the pharmacological treatment from functional magnetic resonance imaging (fMRI) data using a supervised machine learning approach. A total of 84 patients with UD or BD were included in a randomized double-blind parallel-group study in which they received eight weekly infusions of either EPO (40 000 IU) or saline. Task fMRI data were collected before EPO/saline infusions started (baseline) and 6 weeks after last infusion (follow-up). During the scanning sessions, participants were given an n-back working memory and a picture encoding task. Linear classification models with different regularization techniques were used to predict treatment status from both cross-sectional data (at follow-up) and longitudinal data (difference between baseline and follow-up). For the n-back and picture encoding tasks, data were available and analyzed for 52 (EPO; n = 28, Saline; n = 24) and 59 patients (EPO; n = 31, Saline; n = 28), respectively. We found limited evidence that the classifiers used could predict treatment status at a reliable level of performance (≤60% accuracy) when tested using repeated cross-validation. There was no difference in using cross-sectional versus longitudinal data. Whole-brain multivariate decoding applied to pharmaco-fMRI in small to moderate samples seems to be suboptimal for exploring data driven neuronal treatment mechanisms.

18.
J Neural Eng ; 16(6): 066032, 2019 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-31487695

RESUMO

OBJECTIVE: Transcranial magnetic stimulation (TMS) and transcranial electric stimulation (TES) modulate brain activity non-invasively by generating electric fields either by electromagnetic induction or by injecting currents via skin electrodes. Numerical simulations based on anatomically detailed head models of the TMS and TES electric fields can help us to understand and optimize the spatial stimulation pattern in the brain. However, most realistic simulations are still slow, and the role of anatomical fidelity on simulation accuracy has not been evaluated in detail so far. APPROACH: We present and validate a new implementation of the finite element method (FEM) for TMS and TES that is based on modern algorithms and libraries. We also evaluate the convergence of the simulations and estimate errors stemming from numerical and modelling aspects. MAIN RESULTS: Comparisons with analytical solutions for spherical phantoms validate our new FEM implementation, which is three to six times faster than previous implementations. The convergence results suggest that accurately capturing the tissue geometry in addition to choosing a sufficiently accurate numerical method is of fundamental importance for accurate simulations. SIGNIFICANCE: The new implementation allows for a substantial increase in computational efficiency of FEM TMS and TES simulations. This is especially relevant for applications such as the systematic assessment of model uncertainty and the optimization of multi-electrode TES montages. The results of our systematic error analysis allow the user to select the best tradeoff between model resolution and simulation speed for a specific application. The new FEM code is openly available as a part of our open-source software SimNIBS 3.0.


Assuntos
Encéfalo/fisiologia , Análise de Elementos Finitos , Modelos Anatômicos , Estimulação Magnética Transcraniana/métodos , Humanos
19.
Hum Brain Mapp ; 40(17): 4965-4981, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31403748

RESUMO

Previous studies have suggested that the degree of social anhedonia reflects the vulnerability for developing schizophrenia. However, only few studies have investigated how functional network changes are related to social anhedonia. The aim of this fMRI study was to classify subjects according to their degree of social anhedonia using supervised machine learning. More specifically, we extracted both spatial and temporal network features during a social cognition task from 70 subjects, and used support vector machines for classification. Since impairment in social cognition is well established in schizophrenia-spectrum disorders, the subjects performed a comic strip task designed to specifically probe theory of mind (ToM) and empathy processing. Features representing both temporal (time series) and network dynamics were extracted using task activation maps, seed region analysis, independent component analysis (ICA), and a newly developed multi-subject archetypal analysis (MSAA), which here aimed to further bridge aspects of both seed region analysis and decomposition by incorporating a spotlight approach.We found significant classification of subjects with elevated levels of social anhedonia when using the times series extracted using MSAA, indicating that temporal dynamics carry important information for classification of social anhedonia. Interestingly, we found that the same time series yielded the highest classification performance in a task classification of the ToM condition. Finally, the spatial network corresponding to that time series included both prefrontal and temporal-parietal regions as well as insula activity, which previously have been related schizotypy and the development of schizophrenia.


Assuntos
Anedonia , Encéfalo/diagnóstico por imagem , Empatia/fisiologia , Esquizofrenia/diagnóstico por imagem , Percepção Social , Teoria da Mente/fisiologia , Adolescente , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Comportamento Social , Máquina de Vetores de Suporte , Adulto Jovem
20.
Neuroimage ; 190: 269-274, 2019 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-29601954

RESUMO

A patient with motor conversion disorder presented with a functional paresis of the left hand. After exclusion of structural brain damage, she was repeatedly examined with whole-brain functional magnetic resonance imaging, while she performed visually paced finger-tapping tasks. The dorsal premotor cortex showed a bilateral deactivation in the acute-subacute phase. Recovery from unilateral hand paresis was associated with a gradual increase in task-based activation of the dorsal premotor cortex bilaterally. The right medial prefrontal cortex displayed the opposite pattern, showing initial task-based activation that gradually diminished with recovery. The inverse dynamics of premotor and medial prefrontal activity over time were found during unimanual finger-tapping with the affected and non-affected hand as well as during bimanual finger-tapping. These observations suggest that reduced premotor and increased medial prefrontal activity reflect an effector-independent cortical dysfunction in conversion paresis which gradually disappears in parallel with clinical remission of paresis. The results link the medial prefrontal and dorsal premotor areas to the generation of intentional actions. We hypothesise that an excessive 'veto' signal generated in medial prefrontal cortex along with decreased premotor activity might constitute the functional substrate of conversion disorder. This notion warrants further examination in a larger group of affected patients.


Assuntos
Transtorno Conversivo/fisiopatologia , Dedos/fisiopatologia , Neuroimagem Funcional , Atividade Motora/fisiologia , Córtex Motor/fisiopatologia , Paresia/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Recuperação de Função Fisiológica/fisiologia , Adulto , Transtorno Conversivo/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética , Córtex Motor/diagnóstico por imagem , Paresia/diagnóstico por imagem , Córtex Pré-Frontal/diagnóstico por imagem
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