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1.
Neuroimage ; : 116715, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-32147367

RESUMO

Through the Human Connectome Project (HCP) our understanding of the functional connectome of the healthy brain has been dramatically accelerated. Given the pressing public health need, we must increase our understanding of how connectome dysfunctions give rise to disordered mental states. Mental disorders arising from high levels of negative emotion or from the loss of positive emotional experience affect over 400 million people globally. Such states of disordered emotion cut across multiple diagnostic categories of mood and anxiety disorders and are compounded by accompanying disruptions in cognitive function. Not surprisingly, these forms of psychopathology are the leading cause of disability worldwide. The Research Domain Criteria (RDoC) initiative spearheaded by NIMH offers a framework for characterizing the relations among connectome dysfunctions, anchored in neural circuits and phenotypic profiles of behavior and self-reported symptoms. Here, we report on our Connectomes Related to Human Disease protocol for integrating an RDoC framework with HCP protocols to characterize connectome dysfunctions in disordered emotional states, and present quality control data from a representative sample of participants. We focus on three RDoC domains and constructs most relevant to depression and anxiety: 1) loss and acute threat within the Negative Valence System (NVS) domain; 2) reward valuation and responsiveness within the Positive Valence System (PVS) domain; and 3) working memory and cognitive control within the Cognitive System (CS) domain. For 29 healthy controls, we present preliminary imaging data: functional magnetic resonance imaging collected in the resting state and in tasks matching our constructs of interest ("Emotion", "Gambling" and "Continuous Performance" tasks), as well as diffusion-weighted imaging. All functional scans demonstrated good signal-to-noise ratio. Established neural networks were robustly identified in the resting state condition by independent component analysis. Processing of negative emotional faces significantly activated the bilateral dorsolateral prefrontal and occipital cortices, fusiform gyrus and amygdalae. Reward elicited a response in the bilateral dorsolateral prefrontal, parietal and occipital cortices, and in the striatum. Working memory was associated with activation in the dorsolateral prefrontal, parietal, motor, temporal and insular cortices, in the striatum and cerebellum. Diffusion tractography showed consistent profiles of fractional anisotropy along known white matter tracts. We also show that results are comparable to those in a matched sample from the HCP Healthy Young Adult data release. These preliminary data provide the foundation for acquisition of 250 subjects who are experiencing disordered emotional states. When complete, these data will be used to develop a neurobiological model that maps connectome dysfunctions to specific behaviors and symptoms.

2.
J Vis ; 19(12): 23, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31658357

RESUMO

Scientists and engineers have created computations and made measurements that characterize the first steps of seeing. ISETBio software integrates such computations and data into an open-source software package. The initial ISETBio implementations modeled image formation (physiological optics) for planar or distant scenes. The ISET3d software described here extends that implementation, simulating image formation for three-dimensional scenes. The software system relies on a quantitative computer graphics program that ray traces the scene radiance through the physiological optics to the retinal irradiance. We describe and validate the implementation for several model eyes. Then, we use the software to quantify the impact of several physiological optics parameters on three-dimensional image formation. ISET3d is integrated with ISETBio, making it straightforward to convert the retinal irradiance into cone excitations. These methods help the user compute the predictions of optics models for a wide range of spatially rich three-dimensional scenes. They can also be used to evaluate the impact of nearby visual occlusion, the information available to binocular vision, or the retinal images expected from near-field and augmented reality displays.

3.
Neuroimage ; 202: 116048, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31356879

RESUMO

There is much interest in translating neuroimaging findings into meaningful clinical diagnostics. The goal of scientific discoveries differs from clinical diagnostics. Scientific discoveries must replicate under a specific set of conditions; to translate to the clinic we must show that findings using purpose-built scientific instruments will be observable in clinical populations and instruments. Here we describe and evaluate data and computational methods designed to translate a scientific observation to a clinical setting. Using diffusion weighted imaging (DWI), Wahl et al. (2010) observed that across subjects the mean fractional anisotropy (FA) of homologous pairs of tracts is highly correlated. We hypothesize that this is a fundamental biological trait that should be present in most healthy participants, and deviations from this assessment may be a useful diagnostic metric. Using this metric as an illustration of our methods, we analyzed six pairs of homologous white matter tracts in nine different DWI datasets with 44 subjects each. Considering the original FA measurement as a baseline, we show that the new metric is between 2 and 4 times more precise when used in a clinical context. Our framework to translate research findings into clinical practice can be applied, in principle, to other neuroimaging results.

4.
J Vis ; 19(7): 11, 2019 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-31323097

RESUMO

The spectral properties of the ambient illumination provide useful information about time of day and weather. We study the perceptual representation of illumination by analyzing measurements of how well people discriminate between illuminations across scene configurations. More specifically, we compare human performance to a computational-observer analysis that evaluates the information available in the isomerizations of cone photopigment in a model human photoreceptor mosaic. The performance of such an observer is limited by the Poisson variability of the number of isomerizations in each cone. The overall level of Poisson-limited computational-observer sensitivity exceeded that of human observers. This was modeled by increasing the amount of noise in the number of isomerizations of each cone. The additional noise brought the overall level of performance of the computational observer into the same range as that of human observers, allowing us to compare the pattern of sensitivity across stimulus manipulations. Key patterns of human performance were not accounted for by the computational observer. In particular, neither the elevation of illumination-discrimination thresholds for illuminant changes in a blue color direction (when thresholds are expressed in CIELUV ΔE units), nor the effects of varying the ensemble of surfaces in the scenes being viewed, could be accounted for by variation in the information available in the cone isomerizations.


Assuntos
/fisiologia , Iluminação , Percepção Visual/fisiologia , Cor , Percepção de Cores/fisiologia , Sensibilidades de Contraste , Fixação Ocular , Humanos , Variações Dependentes do Observador , Estimulação Luminosa , Células Fotorreceptoras Retinianas Cones/fisiologia , Limiar Sensorial/fisiologia , Software
5.
Annu Rev Vis Sci ; 5: 1-13, 2019 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-31283448

RESUMO

We are sad to report that Professor Jacob (Jack) Nachmias passed away on March 2, 2019. Nachmias was born in Athens, Greece, on June 9, 1928. To escape the Nazis, he and his family came to the United States in 1939. He received his undergraduate degree from Cornell University and then an MA from Swarthmore College, where he worked with Hans Wallach and Wolfgang Kohler; his PhD in Psychology was from Harvard University. Nachmias spent the majority of his career as a Professor of Psychology at the University of Pennsylvania. He made fundamental contributions to our understanding of vision, most notably through the study of eye movements, the development of signal detection theory and forced-choice psychophysical methods, and the psychophysical characterization of spatial-frequency-selective visual channels. Nachmias' work was recognized by his election to the National Academy of Sciences and receipt of the Optical Society's Tillyer Award.

7.
J Vis ; 19(4): 8, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30943530

RESUMO

We present a computational-observer model of the human spatial contrast-sensitivity function based on the Image Systems Engineering Toolbox for Biology (ISETBio) simulation framework. We demonstrate that ISETBio-derived contrast-sensitivity functions agree well with ones derived using traditional ideal-observer approaches, when the mosaic, optics, and inference engine are matched. Further simulations extend earlier work by considering more realistic cone mosaics, more recent measurements of human physiological optics, and the effect of varying the inference engine used to link visual representations to psychophysical performance. Relative to earlier calculations, our simulations show that the spatial structure of realistic cone mosaics reduces the upper bounds on performance at low spatial frequencies, whereas realistic optics derived from modern wave-front measurements lead to increased upper bounds at high spatial frequencies. Finally, we demonstrate that the type of inference engine used has a substantial effect on the absolute level of predicted performance. Indeed, the performance gap between an ideal observer with exact knowledge of the relevant signals and human observers is greatly reduced when the inference engine has to learn aspects of the visual task. ISETBio-derived estimates of stimulus representations at various stages along the visual pathway provide a powerful tool for computing the limits of human performance.


Assuntos
Simulação por Computador , Sensibilidades de Contraste/fisiologia , Células Fotorreceptoras Retinianas Cones/citologia , Humanos , Psicofísica , Células Fotorreceptoras Retinianas Cones/fisiologia , Vias Visuais/fisiologia
8.
J Neural Eng ; 16(2): 025003, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30523985

RESUMO

OBJECTIVE: The nature of artificial vision with a retinal prosthesis, and the degree to which the brain can adapt to the unnatural input from such a device, are poorly understood. Therefore, the development of current and future devices may be aided by theory and simulations that help to infer and understand what prosthesis patients see. APPROACH: A biologically-informed, extensible computational framework is presented here to predict visual perception and the potential effect of learning with a subretinal prosthesis. The framework relies on optimal linear reconstruction of the stimulus from retinal responses to infer the visual information available to the patient. A simulation of the physiological optics of the eye and light responses of the major retinal neurons was used to calculate the optimal linear transformation for reconstructing natural images from retinal activity. The result was then used to reconstruct the visual stimulus during the artificial activation expected from a subretinal prosthesis in a degenerated retina, as a proxy for inferred visual perception. MAIN RESULTS: Several simple observations reveal the potential utility of such a simulation framework. The inferred perception obtained with prosthesis activation was substantially degraded compared to the inferred perception obtained with normal retinal responses, as expected given the limited resolution and lack of cell type specificity of the prosthesis. Consistent with clinical findings and the importance of cell type specificity, reconstruction using only ON cells, and not OFF cells, was substantially more accurate. Finally, when reconstruction was re-optimized for prosthesis stimulation, simulating the greatest potential for learning by the patient, the accuracy of inferred perception was much closer to that of healthy vision. SIGNIFICANCE: The reconstruction approach thus provides a more complete method for exploring the potential for treating blindness with retinal prostheses than has been available previously. It may also be useful for interpreting patient data in clinical trials, and for improving prosthesis design.

9.
Neuron ; 96(2): 298-311, 2017 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-29024656

RESUMO

We summarize the current state of knowledge of the brain's reading circuits, and then we describe opportunities to use quantitative and reproducible methods for diagnosing these circuits. Neural circuit diagnostics-by which we mean identifying the locations and responses in an individual that differ significantly from measurements in good readers-can help parents and educators select the best remediation strategy. A sustained effort to develop and share diagnostic methods can support the societal goal of improving literacy.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/fisiologia , Leitura , Humanos , Imagem por Ressonância Magnética/métodos , Células Ganglionares da Retina/fisiologia
10.
IEEE Trans Image Process ; 26(10): 5032-5042, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28613172

RESUMO

Many creative ideas are being proposed for image sensor designs, and these may be useful in applications ranging from consumer photography to computer vision. To understand and evaluate each new design, we must create a corresponding image processing pipeline that transforms the sensor data into a form, that is appropriate for the application. The need to design and optimize these pipelines is time-consuming and costly. We explain a method that combines machine learning and image systems simulation that automates the pipeline design. The approach is based on a new way of thinking of the image processing pipeline as a large collection of local linear filters. We illustrate how the method has been used to design pipelines for novel sensor architectures in consumer photography applications.

11.
Cereb Cortex ; 27(6): 3346-3359, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28369290

RESUMO

We compare several major white-matter tracts in human and macaque occipital lobe using diffusion magnetic resonance imaging. The comparison suggests similarities but also significant differences in the tracts. There are several apparently homologous tracts in the 2 species, including the vertical occipital fasciculus (VOF), optic radiation, forceps major, and inferior longitudinal fasciculus (ILF). There is one large human tract, the inferior fronto-occipital fasciculus, with no corresponding fasciculus in macaque. We could identify the macaque VOF (mVOF), which has been little studied. Its position is consistent with classical invasive anatomical studies by Wernicke. VOF homology is supported by similarity of the endpoints in V3A and ventral V4 across species. The mVOF fibers intertwine with the dorsal segment of the ILF, but the human VOF appears to be lateral to the ILF. These similarities and differences between the occipital lobe tracts will be useful in establishing which circuitry in the macaque can serve as an accurate model for human visual cortex.


Assuntos
Fibras Nervosas Mielinizadas/fisiologia , Vias Neurais/fisiologia , Lobo Occipital/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Animais , Mapeamento Encefálico , Corpo Caloso/diagnóstico por imagem , Bases de Dados Factuais/estatística & dados numéricos , Imagem de Tensor de Difusão , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Macaca mulatta , Masculino , Vias Neurais/diagnóstico por imagem , Lobo Occipital/anatomia & histologia , Especificidade da Espécie
12.
Sci Rep ; 7(1): 733, 2017 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-28389654

RESUMO

Visual cortex contains a hierarchy of visual areas. The earliest cortical area (V1) contains neurons responding to colour, form and motion. Later areas specialize on processing of specific features. The second visual area (V2) in non-human primates contains a stripe-based anatomical organization, initially defined using cytochrome-oxidase staining of post-mortem tissue. Neurons in these stripes have been proposed to serve distinct functional specializations, e.g. processing of color, form and motion. These stripes represent an intermediate stage in visual hierarchy and serve a key role in the increasing functional specialization of visual areas. Using sub-millimeter high-field functional and anatomical MRI (7T), we provide in vivo evidence for stripe-based subdivisions in humans. Using functional MRI, we contrasted responses elicited by stimuli alternating at slow and fast temporal frequencies. We revealed stripe-based subdivisions in V2 ending at the V1/V2 border. The human stripes reach into V3. Using anatomical MRI optimized for myelin contrast within gray matter, we also observe a stripe pattern. Stripe subdivisions preferentially responding to fast temporal frequencies are more myelinated. As such, functional and anatomical measures provide independent and converging evidence for functional organization into striped-based subdivisions in human V2 and V3.


Assuntos
Mapeamento Encefálico , Imagem por Ressonância Magnética , Córtex Visual/anatomia & histologia , Córtex Visual/fisiologia , Adulto , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética/métodos , Masculino , Bainha de Mielina/metabolismo
13.
J Vis ; 17(2): 4, 2017 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-28196374

RESUMO

Visual neuroscience has traditionally focused much of its attention on understanding the response properties of single neurons or neuronal ensembles. The visual white matter and the long-range neuronal connections it supports are fundamental in establishing such neuronal response properties and visual function. This review article provides an introduction to measurements and methods to study the human visual white matter using diffusion MRI. These methods allow us to measure the microstructural and macrostructural properties of the white matter in living human individuals; they allow us to trace long-range connections between neurons in different parts of the visual system and to measure the biophysical properties of these connections. We also review a range of findings from recent studies on connections between different visual field maps, the effects of visual impairment on the white matter, and the properties underlying networks that process visual information supporting visual face recognition. Finally, we discuss a few promising directions for future studies. These include new methods for analysis of MRI data, open datasets that are becoming available to study brain connectivity and white matter properties, and open source software for the analysis of these data.


Assuntos
Imagem de Difusão por Ressonância Magnética/métodos , Fibras Nervosas/fisiologia , Neurônios/fisiologia , Vias Visuais/fisiologia , Substância Branca/diagnóstico por imagem , Mapeamento Encefálico/métodos , Humanos , Transtornos da Visão/fisiopatologia , Campos Visuais/fisiologia
15.
Hum Brain Mapp ; 37(10): 3623-35, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27273015

RESUMO

Quantitative magnetic resonance imaging (qMRI) aims to quantify tissue parameters by eliminating instrumental bias. We describe qMRI theory, simulations, and software designed to estimate proton density (PD), the apparent local concentration of water protons in the living human brain. First, we show that, in the absence of noise, multichannel coil data contain enough information to separate PD and coil sensitivity, a limiting instrumental bias. Second, we show that, in the presence of noise, regularization by a constraint on the relationship between T1 and PD produces accurate coil sensitivity and PD maps. The ability to measure PD quantitatively has applications in the analysis of in-vivo human brain tissue and enables multisite comparisons between individuals and across instruments. Hum Brain Mapp 37:3623-3635, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Prótons , Adulto , Algoritmos , Artefatos , Fenômenos Biofísicos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Simulação por Computador , Substância Cinzenta/diagnóstico por imagem , Substância Cinzenta/fisiologia , Humanos , Imagem por Ressonância Magnética/instrumentação , Imagens de Fantasmas , Software , Água , Substância Branca/diagnóstico por imagem , Substância Branca/fisiologia , Adulto Jovem
16.
Annu Rev Neurosci ; 39: 103-28, 2016 07 08.
Artigo em Inglês | MEDLINE | ID: mdl-27050319

RESUMO

Progress in magnetic resonance imaging (MRI) now makes it possible to identify the major white matter tracts in the living human brain. These tracts are important because they carry many of the signals communicated between different brain regions. MRI methods coupled with biophysical modeling can measure the tissue properties and structural features of the tracts that impact our ability to think, feel, and perceive. This review describes the fundamental ideas of the MRI methods used to identify the major white matter tracts in the living human brain.


Assuntos
Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Rede Nervosa/fisiologia , Substância Branca/patologia , Substância Branca/fisiologia , Animais , Mapeamento Encefálico/métodos , Substância Cinzenta/patologia , Substância Cinzenta/fisiologia , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Rede Nervosa/patologia
17.
PLoS Comput Biol ; 12(2): e1004692, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26845558

RESUMO

Tractography uses diffusion MRI to estimate the trajectory and cortical projection zones of white matter fascicles in the living human brain. There are many different tractography algorithms and each requires the user to set several parameters, such as curvature threshold. Choosing a single algorithm with specific parameters poses two challenges. First, different algorithms and parameter values produce different results. Second, the optimal choice of algorithm and parameter value may differ between different white matter regions or different fascicles, subjects, and acquisition parameters. We propose using ensemble methods to reduce algorithm and parameter dependencies. To do so we separate the processes of fascicle generation and evaluation. Specifically, we analyze the value of creating optimized connectomes by systematically combining candidate streamlines from an ensemble of algorithms (deterministic and probabilistic) and systematically varying parameters (curvature and stopping criterion). The ensemble approach leads to optimized connectomes that provide better cross-validated prediction error of the diffusion MRI data than optimized connectomes generated using a single-algorithm or parameter set. Furthermore, the ensemble approach produces connectomes that contain both short- and long-range fascicles, whereas single-parameter connectomes are biased towards one or the other. In summary, a systematic ensemble tractography approach can produce connectomes that are superior to standard single parameter estimates both for predicting the diffusion measurements and estimating white matter fascicles.


Assuntos
Encéfalo/fisiologia , Conectoma/métodos , Imagem de Tensor de Difusão/métodos , Imagem por Ressonância Magnética/métodos , Adulto , Biologia Computacional , Humanos , Masculino , Rede Nervosa/fisiologia
18.
Cereb Cortex ; 26(2): 639-646, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25267856

RESUMO

A multiplicity of sensory and cognitive functions has been attributed to the large cortical region at the temporo-parietal junction (TPJ). Using functional MRI, we report that a small region lateralized within the right TPJ responds robustly to certain simple visual stimuli ("vTPJ"). The vTPJ was found in all right hemispheres (n = 7), posterior to the auditory cortex. To manipulate stimuli and attention, subjects were presented with a mixture of visual and auditory stimuli in a concurrent block design in 2 experiments: (1) A simple visual stimulus (a grating pattern modulating in mean luminance) elicited robust responses in the vTPJ, whether or not the subject attended to vision and(2) a drifting low-contrast dartboard pattern of constant mean luminance evoked robust responses in the vTPJ when it was task-relevant (visual task), and smaller responses when it was not (auditory task). The results suggest a focal, visually responsive region within the right TPJ that is powerfully driven by certain visual stimuli (luminance fluctuations), and that can be driven by other visual stimuli when the subject is attending. The precise localization of this visually responsive region is helpful in segmenting the TPJ and to better understand its role in visual awareness and related disorders such as extinction and neglect.


Assuntos
Mapeamento Encefálico , Lateralidade Funcional/fisiologia , Rede Nervosa/fisiologia , Lobo Parietal/fisiologia , Lobo Temporal/fisiologia , Percepção Visual/fisiologia , Estimulação Acústica , Ondas Encefálicas/fisiologia , Eletroencefalografia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Rede Nervosa/irrigação sanguínea , Testes Neuropsicológicos , Oxigênio/sangue , Lobo Parietal/irrigação sanguínea , Estimulação Luminosa , Detecção de Sinal Psicológico , Lobo Temporal/irrigação sanguínea , Vias Visuais/irrigação sanguínea , Vias Visuais/fisiologia
19.
Cereb Cortex ; 26(5): 2205-2214, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-25828567

RESUMO

Human visual cortex comprises many visual field maps organized into clusters. A standard organization separates visual maps into 2 distinct clusters within ventral and dorsal cortex. We combined fMRI, diffusion MRI, and fiber tractography to identify a major white matter pathway, the vertical occipital fasciculus (VOF), connecting maps within the dorsal and ventral visual cortex. We use a model-based method to assess the statistical evidence supporting several aspects of the VOF wiring pattern. There is strong evidence supporting the hypothesis that dorsal and ventral visual maps communicate through the VOF. The cortical projection zones of the VOF suggest that human ventral (hV4/VO-1) and dorsal (V3A/B) maps exchange substantial information. The VOF appears to be crucial for transmitting signals between regions that encode object properties including form, identity, and color and regions that map spatial information.


Assuntos
Córtex Visual/anatomia & histologia , Vias Visuais/anatomia & histologia , Substância Branca/anatomia & histologia , Adulto , Mapeamento Encefálico/métodos , Imagem de Difusão por Ressonância Magnética , Humanos , Masculino , Campos Visuais
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