Raman-assisted crystallography reveals end-on peroxide intermediates in a nonheme iron enzyme.

International audienceIron-peroxide intermediates are central in the reaction cycle of many iron-containing biomolecules. We trapped iron(III)-(hydro)peroxo species in crystals of superoxide reductase (SOR), a nonheme mononuclear iron enzyme that scavenges superoxide radicals. X-ray diffraction data at 1.95 angstrom resolution and Raman spectra recorded in crystallo revealed iron-(hydro)peroxo intermediates with the (hydro)peroxo group bound end-on. The dynamic SOR active site promotes the formation of transient hydrogen bond networks, which presumably assist the cleavage of the iron-oxygen bond in order to release the reaction product, hydrogen peroxide

Praxis and Gesture Recognition

International audienceMost of the developed societies are experiencing an aging trend of theirpopulation. Aging is correlated with cognitive impairment such as dementia and its mostcommon type: Alzheimer's disease. So, there is an urgent need to develop technological toolsto help doctors to do early and precise diagnoses of cognitive decline.Inability to correctly perform purposeful skilled movements with hands and other forelimbsmost commonly is associated with Alzheimer’s disease [1]. These patients have difficulty tocorrectly imitate hand gestures and mime tool use, e.g. pretend to brush one’s hair. Thesepatients make spatial and temporal error

Recommendations for the Use of Serious Games in Neurodegenerative Disorders: 2016 Delphi Panel

The use of Serious Games (SG) in the health domain is expanding. In the field of neurodegenerative disorders (ND) such as Alzheimer’s disease, SG are currently employed both to support and improve the assessment of different functional and cognitive abilities, and to provide alternative solutions for patients’ treatment, stimulation, and rehabilitation. As the field is quite young, recommendations on the use of SG in people with ND are still rare. In 2014 we proposed some initial recommendations (Robert et al., 2014). The aim of the present work was to update them, thanks to opinions gathered by experts in the field during an expert Delphi panel. Results confirmed that SG are adapted to elderly people with mild cognitive impairment (MCI) and dementia, and can be employed for several purposes, including assessment, stimulation, and improving wellbeing, with some differences depending on the population (e.g., physical stimulation may be better suited for people with MCI). SG are more adapted for use with trained caregivers (both at home and in clinical settings), with a frequency ranging from 2 to 4 times a week. Importantly, the target of SG, their frequency of use and the context in which they are played depend on the SG typology (e.g., Exergame, cognitive game), and should be personalized with the help of a clinician

Recommendations for the Use of Serious Games in Neurodegenerative Disorders: 2016 Delphi Panel

International audienceThe use of Serious Games (SG) in the health domain is expanding. In the field of neurodegenerative disorders (ND) such as Alzheimer’s disease, SG are currently employed both to support and improve the assessment of different functional and cognitive abilities, and to provide alternative solutions for patients’ treatment, stimulation, and rehabilitation. As the field is quite young, recommendations on the use of SG in people with ND are still rare. In 2014 we proposed some initial recommendations (Robert et al., 2014). The aim of the present work was to update them, thanks to opinions gathered by experts in the field during an expert Delphi panel. Results confirmed that SG are adapted to elderly people with mild cognitive impairment (MCI) and dementia, and can be employed for several purposes, including assessment, stimulation, and improving wellbeing, with some differences depending on the population (e.g., physical stimulation may be better suited for people with MCI). SG are more adapted for use with trained caregivers (both at home and in clinical settings), with a frequency ranging from 2 to 4 times a week. Importantly, the target of SG, their frequency of use and the context in which they are played depend on the SG typology (e.g., Exergame, cognitive game), and should be personalized with the help of a clinician

Motor representations and the perception of peripersonal space

Dans le cadre de ce travail de thèse, nous nous sommes intéressés aux relations étroites qu'entretiennent processus moteurs et sensoriels pour déterminer les régions de l'espace où une action directe est possible. Dans ce but, nous nous sommes centrés sur la perception de l' "atteignabilité" d'un objet, c'est-à-dire sur les processus cérébraux qui vont permettre de décider si cet objet pourrait être atteignable ou pas par un mouvement du bras. Pour cela, nous faisons l'hypothèse que ces jugements requièrent la prise en compte de connaissances motrices et corporelles fonctionnelles en plus des informations visuelles extraites de l'environnement. Plus particulièrement, nous proposons qu'ils reposent sur une prédiction des conséquences des actes moteurs potentiels suggérés par cet objet et donc de leur faisabilité à un instant donné. Les études réalisées au cours de cette thèse ont ainsi permis d'écarter l'hypothèse de l'influence de l'effort associé à des actions sur la perception de l'espace atteignable. En revanche, le rôle critique de la prédiction des conséquences sensorimotrices des actions a été mis en évidence, grâce à la démonstration d'une relation forte entre d'une part les correspondances entre la distance visuelle et l'amplitude des mouvements, et d'autre part la distance à laquelle la limite d'atteignabilité est perçue. Les processus d'anticipation sensorimotrice ont également été mis en évidence lors de jugements de perception spatiale en présence de cibles dynamiques, rendant compte du caractère spatio-temporel des mécanismes impliqués. Enfin, une dernière étude a montré l'influence des représentations corporelles et de leur plasticité dans la perception de l'espace péripersonnel, mettant ainsi en lumière l'implication du corps en action dans les jugements perceptifsIn this thesis, we assessed the tight relations between motor and sensory processes used to determine the areas of space in which a direct action is possible. We thus focused on the eprception of the reachability of an object, i.e. on the cerebral processes which allow to decide if an object could be reached or not by moving the arm. To do so, we made the hypothesis that theses judgments require to take into account functional motor and body knowledge, in addition to the visual information extracted from the environment. More specifically, we proposed that these judgments rely on a prediction of the consequences of a potential motor act toward the object, thus on the feasibility of the action at a given moment. Our studies discarded the hypothesis of the role of the effort associated to actions on the perception of reachable space. However, the critical role of predicting the sensorimotor consequences of an action has been showed, by demonstrating the strong relation between on the one hand the correspondence between visual distance and movement amplitude, and on the other hand the distance at which the reachability limit is perceived. Sensorimotor anticipation processes have also been showed in spatial perception involving dynamical targets, showing the spatio-temporal aspect of the involved mechanisms. Finally, our last study showed the influence of body representations and of their plasticity on the perception of peripersonal space, highlighting the implication of the body in action in perceptual judgment

Représentations motrices et perception de l'espace péripersonnel

In this thesis, we assessed the tight relations between motor and sensory processes used to determine the areas of space in which a direct action is possible. We thus focused on the eprception of the reachability of an object, i.e. on the cerebral processes which allow to decide if an object could be reached or not by moving the arm. To do so, we made the hypothesis that theses judgments require to take into account functional motor and body knowledge, in addition to the visual information extracted from the environment. More specifically, we proposed that these judgments rely on a prediction of the consequences of a potential motor act toward the object, thus on the feasibility of the action at a given moment. Our studies discarded the hypothesis of the role of the effort associated to actions on the perception of reachable space. However, the critical role of predicting the sensorimotor consequences of an action has been showed, by demonstrating the strong relation between on the one hand the correspondence between visual distance and movement amplitude, and on the other hand the distance at which the reachability limit is perceived. Sensorimotor anticipation processes have also been showed in spatial perception involving dynamical targets, showing the spatio-temporal aspect of the involved mechanisms. Finally, our last study showed the influence of body representations and of their plasticity on the perception of peripersonal space, highlighting the implication of the body in action in perceptual judgmentsDans le cadre de ce travail de thèse, nous nous sommes intéressés aux relations étroites qu'entretiennent processus moteurs et sensoriels pour déterminer les régions de l'espace où une action directe est possible. Dans ce but, nous nous sommes centrés sur la perception de l' "atteignabilité" d'un objet, c'est-à-dire sur les processus cérébraux qui vont permettre de décider si cet objet pourrait être atteignable ou pas par un mouvement du bras. Pour cela, nous faisons l'hypothèse que ces jugements requièrent la prise en compte de connaissances motrices et corporelles fonctionnelles en plus des informations visuelles extraites de l'environnement. Plus particulièrement, nous proposons qu'ils reposent sur une prédiction des conséquences des actes moteurs potentiels suggérés par cet objet et donc de leur faisabilité à un instant donné. Les études réalisées au cours de cette thèse ont ainsi permis d'écarter l'hypothèse de l'influence de l'effort associé à des actions sur la perception de l'espace atteignable. En revanche, le rôle critique de la prédiction des conséquences sensorimotrices des actions a été mis en évidence, grâce à la démonstration d'une relation forte entre d'une part les correspondances entre la distance visuelle et l'amplitude des mouvements, et d'autre part la distance à laquelle la limite d'atteignabilité est perçue. Les processus d'anticipation sensorimotrice ont également été mis en évidence lors de jugements de perception spatiale en présence de cibles dynamiques, rendant compte du caractère spatio-temporel des mécanismes impliqués. Enfin, une dernière étude a montré l'influence des représentations corporelles et de leur plasticité dans la perception de l'espace péripersonnel, mettant ainsi en lumière l'implication du corps en action dans les jugements perceptif

Costs and benefits of tool-use on the perception of reachable space

International audiencePrevious studies have shown that using a tool modifies in a short time-scale both near-body space perception and arm-length representation in the body schema. However, to date no research has specifically investigated the effect of tool-use on an action-related perceptual task. We report here a study assessing the effect of tool-use on the perception of reachable space for perceptual estimates made in reference to either the tool or the hand. Using the tool on distal objects resulted in an extension of perceived reachable space with the tool and reduced the variability of reachability estimates. Tool use also extended perceived reachable space with the hand, but with a concomitant increase of the variability of reachability estimates. These findings suggest that tool incorporation into the represented arm following tool-use improves the anticipation of action possibilities with the tool, while hand representation becomes less accurate

A Gesture Recognition Framework for Cognitive Assessment

International audience17(Suppl.):. Purpose: Most developed countries have been confronted with an acute growth in their elderly population. This situation is accompanied by increased prevalence of several health issues decreasing their quality of life. Alzheimer's disease is one of the most common cognitive disorders associated with aging. This has resulted in an urge to take advantage of technological tools to help doctors by providing early diagnosis which is vital for treatment of the elderly. These patients are not able to correctly emulate forelimb gestures and commit spatial/temporal errors, e.g. pretend to strike a nail with a hammer. 1 We developed a gesture recognition and evaluation tool to assist doctors in early detection of cognitive disorders (Figure 1). The framework performs precise gesture recognition based on state-of-the-art computer vision algorithms and evaluates subjects' performances to obtain a diagnostic report for clinicians. Method: The gesture recognition part of the framework uses four different methods. The first method employs local descriptors such as HOG/HOF 2 using shape and motion cues of a person performing a gesture. In the second method, skeleton information of the subjects is used to benefit from the body pose information. The third method uses depth information to detect exact hand patches with body part trajectories. We also trained a deep learning based recognition model 3 which empowered the framework to perform reliable recognitions. Results and Discussion: The framework is trained to recognize correct/incorrect performances. To have an objective decision on correctness of the gesture performances, clinicians annotated the data used for training the recognition algorithms. The utilized dataset was collected at the Institute Claude Pompidou (ICP) at Nice consisting of 14 dynamic and 15 static gestures selected by clinicians. The framework achieved 90% average accuracy on classifying gestures which is a reliable rate for diagnosis. Additionally, reaction and movement time of a subject are also detected. These two motor reflex criteria which measures responsive level of a subject are important factors in cognitive diagnosis. Motion descriptors are utilized to detect those quantities. All these types of information are illustrated in the user interface which provides clinicians with a detailed assessment of individual gesture and overall performance (Figure 1). Conclusion: We developed a user-friendly tool to help doctors in the diagnosis of cognitive disorders by providing a complete assessment of gestures performed by subjects. Future Work: We will conduct extensive evaluations on a larger population of patients with different levels of cognitive disorders. To improve gesture recognition task, more accurate deep models will be investigated

Thermo-responsive properties of metallo-supramolecular block copolymer micellar hydrogels

Metallo-supramolecular micellar hydrogels exhibiting thermo-mechanical responsiveness are prepared through the hierarchical assembly of a heterotelechelic associating copolymer. The copolymer consists of a linear thermo-sensitive water-soluble sequence terminated by a short hydrophobic sticker at one end, the other being functionalized by a chelating ligand. As the first level of assembly, the associating copolymer is dissolved in aqueous solution to yield micellar nanostructures, bearing coordinative motifs at the end of the coronal chains. The second level of assembly is achieved when transition metal ions are added to the micellar solutions, resulting in almost instantaneous gelation. The thermo-mechanical response of those materials is investigated in detail by rotational rheometry, showing abrupt changes within the temperature boundaries corresponding to the phase transition of the polymer block located in the micellar corona. This journal is © the Partner Organisations 2014