Michel Dojat

Michel Dojat
French Institute of Health and Medical Research | Inserm · Grenoble Institute of Neuroscience GIN

Eng, PhD, HDR

About

223
Publications
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Publications

Publications (223)
Article
Full-text available
With the advent of recent deep learning techniques, computerized methods for automatic lesion segmentation have reached performances comparable to those of medical practitioners. However, little attention has been paid to the detection of subtle physiological changes caused by evolutive pathologies, such as neurodegenerative diseases. In this work,...
Article
Full-text available
Objectives Determining the volume of brain lesions after trauma is challenging. Manual delineation is observer-dependent and time-consuming and cannot therefore be used in routine practice. The study aimed to evaluate the feasibility of an automated atlas-based quantification procedure (AQP) based on the detection of abnormal mean diffusivity (MD)...
Article
Full-text available
Background: Parkinson’s disease (PD) manifests with the appearance of non-motor symptoms before motor symptoms onset. Among these, dysfunctioning visual structures have recently been reported to occur at early disease stages. Objective: This study addresses effective connectivity in the visual network of PD patients. Methods: Using functional MRI a...
Preprint
Full-text available
In this paper, we reconsider to what extent, in the context of Neuroscience and Computer Science of the XXIst century, consciousness would remain or not a human specificity. Equivalent functional faculties can be produced by systems differing not only by the material of which they are constructed, but also by the architecture that combines their co...
Article
Full-text available
Retinal motion of the visual scene is not consciously perceived during ocular saccades in normal everyday conditions. It has been suggested that extra-retinal signals actively suppress intra-saccadic motion perception to preserve stable perception of the visual world. However, using stimuli optimized to preferentially activate the M-pathway, Castet...
Preprint
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Although neural networks have proven very successful in a number of medical image analysis applications, their use remains difficult when targeting subtle tasks such as the identification of barely visible brain lesions, especially given the lack of annotated datasets. Good candidate approaches are patch-based unsupervised pipelines which have both...
Chapter
Although neural networks have proven very successful in a number of medical image analysis applications, their use remains difficult when targeting subtle tasks such as the identification of barely visible brain lesions, especially given the lack of annotated datasets. Good candidate approaches are patch-based unsupervised pipelines which have both...
Preprint
Full-text available
ImUnity is an original deep-learning model designed for efficient and flexible MR image harmonization. A VAE-GAN network, coupled with a confusion module and an optional biological preservation module, uses multiple 2D-slices taken from different anatomical locations in each subject of the training database, as well as image contrast transformation...
Article
Full-text available
MRI plays a crucial role in multiple sclerosis diagnostic and patient follow-up. In particular, the delineation of T2-FLAIR hyperintense lesions is crucial although mostly performed manually - a tedious task. Many methods have thus been proposed to automate this task. However, sufficiently large datasets with a thorough expert manual segmentation a...
Book
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De nouvelles neurotechnologies se déploient désormais dans un paysage d’innovation où la diffusion du numérique a ouvert sur une véritable transformation civilisationnelle, avec des défis culturels, sociétaux et humains qui font osciller nos contemporains entre craintes et une certaine promesse ou espérance liée à leurs usages. Leur arrivée sur l...
Preprint
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Background: PD is associated with non-motor symptoms appearing before the motor symptoms onset. Recent studies report dysfunctions of visual structures at early stages of PD. Objective: This study addresses effective connectivity in the visual network of PD patients. Methods: Using brain functional MRI and Dynamic Causal Modeling analysis, we inves...
Preprint
Full-text available
[french] Chapter 8 of the book on Consciousness by CARMEN group (Grenoble, France) Is consciousness limited to humans or animals with a cortex ? Or can it exist in other animals and machines ?
Preprint
Full-text available
With the advent of recent deep learning techniques, computerized methods for automatic lesion segmentation have reached performances comparable to those of medical practitioners. However, little attention has been paid to the detection of subtle physiological changes caused by evolutive pathologies such as neurodegenerative diseases. In this work,...
Preprint
Full-text available
Objectives. The determination of the volume of brain lesions after trauma is challenging. Manual delineation is observer-dependent and time-consuming which inhibits the practice in clinical routine. We propose and evaluate an automated atlas-based quantification procedure (AQP) based on the detection of abnormal mean diffusivity (MD) values compute...
Preprint
Full-text available
Automatic segmentation of brain abnormalities is challenging, as they vary considerably from one pathology to another. Current methods are supervised and require numerous annotated images for each pathology, a strenuous task. To tackle anatomical variability, Unsupervised Anomaly Detection (UAD) methods are proposed, detecting anomalies as outliers...
Article
Full-text available
Clinical multicenter imaging studies are frequent and rely on a wide range of existing tools for sharing data and processing pipelines. This is not the case for preclinical (small animal) studies. Animal population imaging is still in infancy, especially because a complete standardization and control of initial conditions in animal models across la...
Article
Full-text available
Similarly to human population imaging, there are several well-founded motivations for animal population imaging, the most notable being the improvement of the validity of statistical results by pooling a sufficient number of animal data provided by different imaging centers. In this paper, we demonstrate the feasibility of such a multicenter animal...
Preprint
Full-text available
Similarly to human population imaging, there are several well-founded motivations for animal population imaging, the most notable being the improvement of the validity of statistical results by pooling a sufficient number of animal data provided by different imaging centers. In this paper, we demonstrate the feasibility of such a multicenter animal...
Article
Objectives: The dual hit hypothesis about the pathogenesis of Parkinson's disease suggests that the brainstem is a convergent area for the propagation of pathological α-synuclein from the periphery to the brain. While brainstem structures are likely to be affected early in the course of the disease, detailed information regarding specific brainste...
Preprint
Grapheme-colour synaesthesia is a subjective phenomenon related to perception and imagination, in which some people involuntarily but systematically associate specific, idiosyncratic colours to achromatic letters or digits. Its investigation is relevant to unravel the neural correlates of colour perception in isolation from low-level neural process...
Article
Full-text available
The identification of brain morphological alterations in newly diagnosed PD patients (i.e. 'de novo') could potentially serve as a biomarker and accelerate diagnosis. However, presently no consensus exists in the literature possibly due to several factors: small size cohorts, differences in segmentation techniques or bad control of false positive r...
Article
Full-text available
The infestation of a work of art may be destructive for the piece itself and also presents the threat of spreading throughout an entire collection. Several methods are available to museums in order to diagnose an infestation at an early stage and then treat it and prevent possible proliferation. Imaging offers a large range of non-destructive techn...
Article
Full-text available
We report the evaluation of an automated method for quan-tification of brain tissue damage, caused by a severe traumatic brain injury, using mean diffusivity computed from MR diffusion images. Our automatic results obtained on realistic phantoms and real patient images 10 days post-event provided by nine different centers were coherent with four ex...
Conference Paper
Full-text available
Stroke lesion segmentation
Conference Paper
Full-text available
Automatic segmentation of chronic stroke lesion from magnetic resonance images (MRI) is motivated by the increasing need for reproducible and repeatable endpoints in clinical trials. The task is non-trivial, due to a number of confounding factors, including heterogeneous lesion intensity, irregular shape, and large deformations that render the conv...
Article
Full-text available
We present a study of multiple sclerosis segmentation algorithms conducted at the international MICCAI 2016 challenge. This challenge was operated using a new open-science computing infrastructure. This allowed for the automatic and independent evaluation of a large range of algorithms in a fair and completely automatic manner. This computing infra...
Chapter
We report the evaluation of an automated method for quantification of brain tissue damage, caused by a severe traumatic brain injury, using mean diffusivity computed from MR diffusion images. Our automatic results obtained on realistic phantoms and real patient images 10 days post-event provided by nine different centers were coherent with four exp...
Chapter
Full-text available
Automatic segmentation of chronic stroke lesion from magnetic resonance images (MRI) is motivated by the increasing need for reproducible and repeatable endpoints in clinical trials. The task is non-trivial, due to a number of confounding factors, including heterogeneous lesion intensity, irregular shape, and large deformations that render the conv...
Preprint
Full-text available
We present a study of multiple sclerosis segmentation algorithms conducted at the international MICCAI 2016 challenge. This challenge was operated using a new open-science computing infrastructure. This allowed for the automatic and independent evaluation of a large range of algorithms in a fair and completely automatic manner. This computing infra...
Preprint
Full-text available
Surface color appearance depends on both local surface chromaticity and global context. How are these inter-dependencies supported by cortical networks? Combining functional imaging and psychophysics, we examined if color from long-range filling-in engages distinct pathways from responses caused by a field of uniform chromaticity. We find that colo...
Article
Full-text available
Several publications have reported structural changes in the brain of synesthetes compared to controls, either local differences or differences in connectivity. In the present study, we pursued this quest for structural brain differences that might support the subjective experience of synesthesia. In particular, for the first time in this field, we...
Data
Surface based morphometry. Material and Methods. (PDF)
Data
Individual demographic characteristics for the synesthete population. Average response time (inverse of the mean inverse RT) in synesthetic Stroop tasks: CC: Congruent stimuli in Color task; IC: Incongruent Color; CP: Congruent Photism task; IP: Incongruent Photism. “Synesthesia Strength” (also called photism strength) = (IC-CC)–(CP-CC). (see for d...
Data
Individual demographic characteristics for the control population. * subject not used in sulci and surface-based morphometry analyzes. (PDF)
Data
Correlation between WM and photism strength in our population of synesthetes. Left: Cluster-forming threshold p<0.001, t>3.4. Right: T statistic magnitude is mapped to color transparency. Correlation scale is between -2 and 2 10−4. For the coordinates for A, B and C views see the legend of Fig 2. Neurological convention (Right = Right). (PDF)
Data
Mean demographic characteristics for the control and synesthete populations. (PDF)
Data
Surface based morphometry. Differences in 48 controls vs. 32 synesthetes for cortical thickness (mm), area (mm2) and volume (mm3) for left and right hemispheres (Cluster-forming threshold p<0.001). For each parameter, regions where differences were detected are indicated. No region survived the FWEc at the cluster level. (PDF)
Article
Full-text available
Conjoint measurement was used to investigate the joint influences of the luminance of the background and the inner contour on hue- and brightness filling-in for a stimulus configuration generating a water-color effect (WCE), i.e., a wiggly bi-chromatic contour enclosing a region with the lower luminance component on the exterior. Two stimuli with t...
Preprint
Several publications have reported structural changes in the brain of synesthetes compared to controls, either local differences or differences in connectivity. In the present study, we pursued this quest for structural brain differences that might support the subjective experience of synaesthesia. In particular, for the first time in this field, w...
Conference Paper
Functional Magnetic Resonance Imaging (fMRI) is a neuroimaging technique that allows the non-invasive study of brain function. It is based on the hemodynamic variations induced by changes in cerebral synaptic activity following sensory or cognitive stimulation. The measured signal depends on the variation of blood oxygenation level (BOLD signal) wh...
Article
Grapheme‐colour synaesthesia is a subjective phenomenon related to perception and imagination, in which some people involuntarily but systematically associate specific, idiosyncratic colours to achromatic letters or digits. Its investigation is relevant to unravel the neural correlates of colour perception in isolation from low‐level neural process...
Article
Luminance contrast is a fundamental visual cue. Using a dedicated neuroimaging framework, we sought to characterize typical Blood Oxygen Level Dependent (BOLD) responses in two subcortical regions, the superior colliculus (SC) and the lateral geniculate nucleus (LGN), and V1, the primary visual cortex area, and how they change over the lifespan. Fo...
Conference Paper
We report our methodological developments to investigate, in a multi-center study using mean diffusivity, the tissue damage caused by a severe traumatic brain injury (GSC \(<9\)) in the 10 days post-event. To assess the diffuse aspect of the injury, we fuse several atlases to parcel cortical, subcortical and WM structures into well identified regio...
Article
Full-text available
Visual analysis of real-life scenes starts with the parallel extraction of different visual elementary features at different spatial frequencies. The global shape of the scene is mainly contained in low spatial frequencies (LSF), and the edges and borders of objects are mainly contained in high spatial frequencies (HSF). The present fMRI study inve...
Article
Full-text available
FMRI retinotopic mapping is a non-invasive technique for the delineation of low-level visual areas in individual subjects. It generally relies upon the analysis of functional responses to periodic visual stimuli that encode eccentricity or polar angle in the visual field. This technique is used in vision research when the precise assignation of bra...
Article
Full-text available
Synesthesia refers to additional sensations experienced by some people for specific stimulations, such as the systematic arbitrary association of colors to letters for the most studied type. Here, we review all the studies (based mostly on functional and structural magnetic resonance imaging) that have searched for the neural correlates of this sub...
Conference Paper
Full-text available
But de l'étude. Les bases d’une méthodologie de cartographie non-invasive des aires visuelles en IRMf ont été posées par les travaux princeps de Sereno (Sereno et al. 1995). Depuis, cette approche permettant de délinéer les aires visuelles de V1 à hV4 a été couramment utilisée dans de nombreuses études. La durée des acquisitions permettant une cart...
Article
Full-text available
Cognitive impairment related to obstructive sleep apnea might be explained by subtle changes in brain anatomy. This has been mainly investigated using magnetic resonance brain scans coupled with a voxel-based morphometry analysis. However, this approach is prone to several methodological pitfalls that may explain the large discrepancy in the result...
Article
Full-text available
Advances in neuroscience are underpinned by large, multicenter studies and a mass of heterogeneous datasets. When investigating the relationships between brain anatomy and brain functions under normal and pathological conditions, measurements obtained from a broad range of brain imaging techniques are correlated with the information on each subject...