Occipital Proton Magnetic Resonance Spectroscopy ((1)H-MRS) Reveals Normal Metabolite Concentrations in Retinal Visual Field Defects

BACKGROUND: Progressive visual field defects, such as age-related macular degeneration and glaucoma, prevent normal stimulation of visual cortex. We investigated whether in the case of visual field defects, concentrations of metabolites such as N-acetylaspartate (NAA), a marker for degenerative processes, are reduced in the occipital brain region. METHODOLOGY/PRINCIPAL FINDINGS: Participants known with glaucoma, age-related macular degeneration (the two leading causes of visual impairment in the developed world), and controls were examined by proton MR spectroscopic ((1)H-MRS) imaging. Absolute NAA, Creatine and Choline concentrations were derived from a single-voxel in the occipital region of each brain hemisphere. No significant differences in metabolites concentrations were found between the three groups. CONCLUSIONS/SIGNIFICANCE: We conclude that progressive retinal visual field defects do not affect metabolite concentration in visual brain areas suggesting that there is no ongoing occipital degeneration. We discuss the possibility that metabolite change is too slow to be detectable

Discrete and Effortful Imagined Movements Do Not Specifically Activate the Autonomic Nervous System

International audienceBACKGROUND: The autonomic nervous system (ANS) is activated in parallel with the motor system during cyclical and effortful imagined actions. However, it is not clear whether the ANS is activated during motor imagery of discrete movements and whether this activation is specific to the movement being imagined. Here, we explored these topics by studying the baroreflex control of the cardiovascular system. METHODOLOGY/PRINCIPAL FINDINGS: Arterial pressure and heart rate were recorded in ten subjects who executed or imagined trunk or leg movements against gravity. Trunk and leg movements result in different physiological reactions (orthostatic hypotension phenomenon) when they are executed. Interestingly, ANS activation significantly, but similarly, increased during imagined trunk and leg movements. Furthermore, we did not observe any physiological modulation during a control mental-arithmetic task or during motor imagery of effortless movements (horizontal wrist displacements). CONCLUSIONS/SIGNIFICANCE: We concluded that ANS activation during motor imagery is general and not specific and physiologically prepares the organism for the upcoming effortful action

10 years of CEMARA database in the AnDDI-Rares network: a unique resource facilitating research and epidemiology in developmental disorders in France

Background : In France, the Ministry of Health has implemented a comprehensive program for rare diseases (RD) that includes an epidemiological program as well as the establishment of expert centers for the clinical care of patients with RD. Since 2007, most of these centers have entered the data for patients with developmental disorders into the CEMARA population-based registry, a national online data repository for all rare diseases. Through the CEMARA web portal, descriptive demographic data, clinical data, and the chronology of medical follow-up can be obtained for each center. We address the interest and ongoing challenges of this national data collection system 10 years after its implementation. Methods : Since 2007, clinicians and researchers have reported the “minimum dataset (MDS)” for each patient presenting to their expert center. We retrospectively analyzed administrative data, demographic data, care organization and diagnoses. Results : Over 10 years, 228,243 RD patients (including healthy carriers and family members for whom experts denied any suspicion of RD) have visited an expert center. Among them, 167,361 were patients affected by a RD (median age 11 years, 54% children, 46% adults, with a balanced sex ratio), and 60,882 were unaffected relatives (median age 37 years). The majority of patients (87%) were seen no more than once a year, and 52% of visits were for a diagnostic procedure. Among the 2,869 recorded rare disorders, 1,907 (66.5%) were recorded in less than 10 patients, 802 (28%) in 10 to 100 patients, 149 (5.2%) in 100 to 1,000 patients, and 11 (0.4%) in > 1,000 patients. Overall, 45.6% of individuals had no diagnosis and 6.7% had an uncertain diagnosis. Children were mainly referred by their pediatrician (46%; n = 55,755 among the 121,136 total children referrals) and adults by a medical specialist (34%; n = 14,053 among the 41,564 total adult referrals). Given the geographical coverage of the centers, the median distance from the patient’s home was 25.1 km (IQR = 6.3 km-64.2 km). Conclusions : CEMARA provides unprecedented support for epidemiological, clinical and therapeutic studies in the field of RD. Researchers can benefit from the national scope of CEMARA data, but also focus on specific diseases or patient subgroups. While this endeavor has been a major collective effort among French RD experts to gather large-scale data into a single database, it provides tremendous potential to improve patient care

Muscle fatigue affects mental simulation of action.

International audienceSeveral studies suggest that when subjects mentally rehearse or execute a familiar action, they engage similar neural and cognitive operations. Here, we examined whether muscle fatigue could influence mental movements. Participants mentally and actually performed a sequence of vertical arm movements (rotation around the shoulder joint) before and after a fatiguing exercise involving the right arm. We found similar durations for actual and mental movements before fatigue, but significant temporal discrepancies after fatigue. Specifically, mental simulation was accelerated immediately after fatigue, while the opposite was observed for actual execution. Furthermore, actual movements showed faster adaptation (i.e., return to prefatigue values) than mental movements. The EMG analysis showed that postfatigue participants programmed larger, compared to prefatigue, neural drives. Therefore, immediately after fatigue, the forward model received dramatically greater efferent copies and predicted faster, compared to prefatigue, arm movements. During actual movements, the discrepancy between estimated (forward model output) and actual state (sensory feedback) of the arm guided motor adaptation; i.e., durations returned rapidly to prefatigue values. Since during mental movements there is no sensory information and state estimation derives from the forward model alone, mental durations remained faster after fatigue and their adaptation was longer than those of actual movements. This effect was specific to the fatigued arm because actual and mental movements of the left nonfatigued arm were unaffected. The current results underline the interdependence of motor and cognitive states and suggest that mental actions integrate the current state of the motor system

Interaction entre processus centraux et périphériques lors de l'exécution, la simulation et l'observation du mouvement

Imaginer réaliser un mouvement ou observer une personne exécutant une action nécessite la participation de représentations mentales. Bien que simuler ou observer une action n implique pas de mouvement apparent, la participation des aires cérébrales motrices est essentielle à ces mécanismes. Si la participation d une composante motrice aux mécanismes de simulation mentale et d observation motrice n est plus à démontrer, la contribution d une composante sensorielle dans ces processus théoriquement centraux reste à éclaircir. (1) Dans la première étude, la présence d illusions sensorielles induites par la vibration musculaire influençaient les mouvements exécuté, simulé et inféré; (2) l altération de la simulation motrice a également été rapportée après l arrêt de cette stimulation (étude 2). Les post-effets induits étaient plus importants et l adaptation plus longue lors du mouvement imaginé, de part l absence de réafférences; (3) Dans la troisième étude, une contraction volontaire prolongée influençait également la simulation du mouvement. Une prédiction erronée en présence de fatigue musculaire a été montrée; (4) La quatrième étude a révélé une diminution de la capacité de patients vestibulo-lésés, à simuler des mouvements; (5) pour finir, nous avons montré que le cerveau peut, en plus des conséquences sensorielles, anticiper de manière non spécifique les changements physiologiques d un mouvement en activant le système nerveux autonome. En résumé, nos résultats révèlent la contribution du système sensori-moteur durant la simulation mentale et l observation du mouvement. Nous discutons ces résultats par l intermédiaire des données issues des neurosciences computationnelles.Imagining a movement or observing someone executing an action requires the participation of mental representations. Although imagining or observing an action doesn t involve apparent motion, participation of cerebral motor areas is essential in these activities. While at the cortical level, it has been clearly shown that there is a participation of a motor component, we do not know if there is a participation of a sensory component. (1) In the fist study, the presence of kinaesthetic illusions (induced by muscle vibration) significantly influenced the executed, imagined and observed movements (2) Alterations in the mental simulations were also reported after the end of the muscle vibration stimulation (study 2). Induced post-effects were greater and the adaptation was longer during the imagined movement (3) In the third study, a prolonged voluntary contraction also influenced the mental simulation of a movement. An erroneous prediction was shown in the presence of muscular fatigue (4) The fourth study revealed a decrease of mental simulation capacity in patients with vestibular strokes. (5) Finally we showed that in addition to anticipating sensory consequences the brain can also anticipates, non specifically, physiological changes mediated by the autonomous nervous system. In short, our results reveal the contribution of the sensori-motor system during mental simulation and observation of movement. We discuss these results in light of studies that have been conducted in the field of computational neuroscience.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Discrete and Effortful Imagined Movements Do Not Specifically Activate the Autonomic Nervous System

Background: The autonomic nervous system (ANS) is activated in parallel with the motor system during cyclical and effortful imagined actions. However, it is not clear whether the ANS is activated during motor imagery of discrete movements and whether this activation is specific to the movement being imagined. Here, we explored these topics by studying the baroreflex control of the cardiovascular system. Methodology/Principal Findings: Arterial pressure and heart rate were recorded in ten subjects who executed or imagined trunk or leg movements against gravity. Trunk and leg movements result in different physiological reactions (orthostatic hypotension phenomenon) when they are executed. Interestingly, ANS activation significantly, but similarly, increased during imagined trunk and leg movements. Furthermore, we did not observe any physiological modulation during a control mental-arithmetic task or during motor imagery of effortless movements (horizontal wrist displacements). Conclusions/Significance: We concluded that ANS activation during motor imagery is general and not specific and physiologically prepares the organism for the upcoming effortful action

La fatigue musculaire altère la simulation mentale du mouvement

La simulation du mouvement est un acte purement central. Cependant, la participation du système périphérique reste éclaircir. Les durées des mouvements exécutés et imaginés du bras de huit sujets ont été enregistrées avant et après un exercice fatiguant de maintien de position. La durée des mouvements du bras droit exécutés après l’exercice fatigant, diminuait significativement (14,4 %; P < 0,001) alors qu’elle augmentait significativement pour les mouvements imaginés (12,6 %; P < 0,001). Cette différence serait expliquée par l’absence de réafférences relatives au mouvement lors de la simulation motrice. (résumé d'auteur)

Action Representation in Patients with Bilateral Vestibular Impairments

Import JabRef | WosArea Life Sciences and Biomedicine - Other TopicsInternational audienceDuring mental actions subjects feel themselves performing a movement without any corresponding motor output. Although broad information is available regarding the influence of central lesions on action representation, little is known about how peripheral damages affect mental events. In the current study, we investigated whether lack of vestibular information influences action representation. Twelve healthy adults and twelve patients with bilateral vestibular damage actually performed and mentally simulated walking and drawing. The locomotor paths implied one (first walking task) and four (second walking task) changes in the walking direction. In the drawing task, participants drew on a sheet of paper a path that was similar to that of the second walking task. We recorded and compared between the two groups the timing of actual and mental movements. We found significant temporal discrepancies between actual and mental walking movements in the group of patients. Conversely, drawing actual and drawing mental durations were similar. For the control group, an isochrony between mental and actual movements was observed for the three tasks. This result denotes an inconsistency between action representation and action execution following vestibular damage, which is specific to walking movements, and emphasizes the role of the vestibular system upon mental states of actions. This observation may have important clinical implications. During action planning vestibular patients may overestimate the capacity of their motor system (imaging faster, executing slower) with harmful consequences for their health

Action representation in patients with bilateral vestibular impairments.

During mental actions subjects feel themselves performing a movement without any corresponding motor output. Although broad information is available regarding the influence of central lesions on action representation, little is known about how peripheral damages affect mental events. In the current study, we investigated whether lack of vestibular information influences action representation. Twelve healthy adults and twelve patients with bilateral vestibular damage actually performed and mentally simulated walking and drawing. The locomotor paths implied one (first walking task) and four (second walking task) changes in the walking direction. In the drawing task, participants drew on a sheet of paper a path that was similar to that of the second walking task. We recorded and compared between the two groups the timing of actual and mental movements. We found significant temporal discrepancies between actual and mental walking movements in the group of patients. Conversely, drawing actual and drawing mental durations were similar. For the control group, an isochrony between mental and actual movements was observed for the three tasks. This result denotes an inconsistency between action representation and action execution following vestibular damage, which is specific to walking movements, and emphasizes the role of the vestibular system upon mental states of actions. This observation may have important clinical implications. During action planning vestibular patients may overestimate the capacity of their motor system (imaging faster, executing slower) with harmful consequences for their health

Integration of proprioceptive signals and attentional capacity during postural control are impaired but subject to improvement in dyslexic children

Import JabRef | WosArea Neurosciences and NeurologyInternational audienceChildren with developmental dyslexia suffer from delayed reading capabilities and may also exhibit attentional and sensori-motor deficits. The objective of this study was twofold. First, we aimed at investigating whether integration of proprioceptive signals in balance control was more impaired in dyslexic children when the attentional demand was varied. Secondly, we checked whether this effect was reduced significantly by using a specific treatment to improve eye control deficits and certain postural signs that are often linked to dyslexia (Quercia et al. in J Fr Ophtalmol 28:713-723, 2005, J Fr Ophtalmol 30:380-89, 2007). Thirty dyslexic and 51 treated dyslexic children (> 3 months of treatment) were compared with 42 non-dyslexic children in several conditions (mean age: 136.2 +/- A 23.6, 132.2 +/- A 18.7 and 140.2 +/- A 25 months, respectively). Co-vibration of ankle muscles was effected in order to alter proprioceptive information originating from the ankle. In two vibration conditions, ankle muscles were either not vibrated or vibrated at 85 Hz without illusion of any movement. These two vibration conditions were combined with two attentional conditions. In the first such condition, children maintained balance while merely fixing their gaze on a point in front of them. In the second condition, they had to look for smaller or larger stars in a panel showing forty of each kind. Balance was assessed by means of a force plate. Results indicated that the mean velocity (i.e. the total length) of the center of pressure (CoP) displacement in the 85-Hz vibration condition increased significantly more (compared with no vibration) in the dyslexic and the treated dyslexic groups than in the control group, irrespective of the attention task. Interestingly, in the condition without vibration, the attentional performance of treated children was similar to that of the control group, whereas the attentional performance of the untreated dyslexic children was significantly impaired. Altogether, these results suggest that integration of proprioceptive signals in balance control and attentional capacity are impaired in dyslexic children. However, attention capacity during the control of stance could be improved significantly