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The processing of proprioceptive information in the context of a conflict between visual and somatosensory feedbacks deteriorates motor performance. Previous studies have shown that seeing one’s hand increases the weighting assigned to arm somatosensory inputs. In this light, we hypothesized that the sensory conflict, when tracing the contour of a shape with mirror-reversed vision, will be greater for participants who trace with a stylus seen in their hand (Hand group, n=17) than for participants who trace with the tip of rod without seen their hand (Tool group, n=15). Based on this hypothesis, we predicted that the tracing performance with mirror vision will be more deteriorated for the Hand group than for the Tool group, and we predicted a greater gating of somatosensory information for the Hand group to reduce the sensory conflict. The participants of both groups followed the outline of a shape in two visual conditions. Direct vision: the participants saw the hand or portion of a light 40 cm rod directly. Mirror Vision: the hand or the rod was seen through a mirror. We measured tracing performance using a digitizing tablet and the cortical activity with electroencephalography. Behavioral analyses revealed that the tracing performance of both groups was similarly impaired by mirror vision. However, contrasting the spectral content of the cortical oscillatory activity between the Mirror and Direct conditions, we observed that tracing with mirror vision resulted in significantly larger alpha (8-12 Hz) and beta (15-25 Hz) powers in the somatosensory cortex for participants of the Hand group. The somatosensory alpha and beta powers did not significantly differ between Mirror and Direct vision conditions for the Tool group. For both groups, tracing with mirror vision altered the activity of the visual cortex: decreased alpha power for the Hand group, decreased alpha and beta power for the Tool group. Overall, these results suggest that seeing the hand enhanced the sensory conflict when tracing with mirror vision and that the increase of alpha and beta powers in the somatosensory cortex served to reduce the weight assigned to somatosensory information. The increased activity of the visual cortex observed for both groups in the mirror vision condition suggests greater visual processing with increased task difficulty. Finally, the fact that the participants of the Tool group did not show better tracing performance than those of the Hand group suggests that tracing deterioration resulted from a sensorimotor conflict (as opposed to a visuo-proprioceptive conflict).

International audience; The purpose of handwriting is to produce a legible trace quickly and fluently. Its motor control and learning therefore rely on an efficient integration of visual and proprioceptive feedback, with a transition from a control based on the written trace in beginner to a control based mainly on writing movements in expert writer. The aim of this study was to test the effect of a partial deletion of the written trace and an increase of visual information on the kinematics after the performance in a learning task. Twenty-four adults learned to write six new pseudoletters with a stylus controlled by non-dominant hand on a touch screen digital tablet. Half of the pseudoletters were trained in the modified visual FB conditions and the other half without modification (control condition). Results revealed that, in the short-term, the pseudoletters trained with the modified visual feedback were written faster and more fluently than those trained in the control condition, without spatial accuracy reduction. This method seems to be efficient, at least in proficient adults and is currently tested in children with dysgraphia.

A previous study have shown that musical background during training improve handwriting speed and fluency in a child with difficulties (Veron-Delor et al., 2017). However, it is still necessary to explain this effect. One hypothesis is that handwriting movement synchronizes with the music rhythm. This should lead to a stabilization of the movement, as it has been reported in other motor activities (e.g. Dalla Bella et al., 2018). To address this issue, we propose here to record handwriting kinematics in children under different background conditions. Specifically, three main questions will be addressed. First, we will investigate if rhythm could explain the benefits of musical background reported in previous studies. To this aim, melodic and rhythmic+melodic background will be compared to a silent condition. Second, we will test the influence of tempo on handwriting to confirm the synchronization of handwriting to auditory stimuli. Third, different variables may modulate the benefits of rhythmic background. Specifically, we will investigate the role of handwriting automation by testing this effect in two age groups. In addition, spontaneous tempo and handwriting deficits will be assessed to correlate these variables to rhythmic background benefits.

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International audience; Dans cet article, nous présentons l’organisation des aires cérébrales impliquées dans l’écriture manuscrite chez l’adulte, et nous décrivons des données récentes sur cette organisation dans le cerveau d’enfants en cours d’apprentissage. Chez l’adulte, le réseau impliqué comprend un ensemble de régions pariéto-frontales gauches, le gyrus fusiforme gauche et le cervelet droit. Ces régions codent les aspects orthographiques et moteurs de l’écriture manuscrite. Chez l’enfant de huit à 11 ans, les régions bien décrites chez l’adulte sont également actives : le réseau del’écriture est déjà structuré. Cependant, des différences observées entre les deux groupes dans le niveau d’activation de certains éléments du réseau, dans le recrutement d’autres régions ou dans la latéralisation des activations témoignent d’un processus en cours d’automatisation.

International audience; Developmental coordination disorder (DCD) is a common and well-recognized neurodevelopmental disorder affecting approximately 5 in every 100 individuals worldwide. It has long been included in standard national and international classifications of disorders (especially the Diagnostic and Statistical Manual of Mental Disorders). Children and adults with DCD may come to medical or paramedical attention because of poor motor skills, poor motor coordination, and/or impaired procedural learning affecting activities of daily living. Studies show DCD persistence of 30-70% in adulthood for individuals who were diagnosed with DCD as children, with direct consequences in the academic realm and even beyond. In particular, individuals with DCD are at increased risk of impaired handwriting skills. Medium-term and long-term prognosis depends on the timing of the diagnosis, (possible) comorbid disorders (and their diagnosis), the variability of signs and symptoms (number and intensity), and the nature and frequency of the interventions individuals receive. We therefore chose to investigate the signs and symptoms, diagnosis, and rehabilitation of both DCD and developmental dysgraphia, which continues to receive far too little attention in its own right from researchers and clinicians.

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International audience; The aim of this study was to evaluate the compensatory effects of real-time auditory feedback on two proprioceptively deafferented subjects. The real-time auditory feedback was based on a movement sonification approach, consisting of translating some movement variables into synthetic sounds to make them audible. The two deafferented subjects and 16 age-matched control participants were asked to learn four new characters. The characters were learned under two different conditions, one without sonification and one with sonification, respecting a within-subject protocol. The results revealed that characters learned with sonification were reproduced more quickly and more fluently than characters learned without and that the effects of sonification were larger in deafferented than in control subjects. Secondly, whereas control subjects were able to learn the characters without sounds the deafferented subjects were able to learn them only when they were trained with sonification. Thirdly, although the improvement was still present in controls, the performance of deafferented subjects came back to the pre-test level 2 h after the training with sounds. Finally, the two deafferented subjects performed differently from each other, highlighting the importance of studying at least two subjects to better understand the loss of proprioception and its impact on motor control and learning. To conclude, movement sonification may compensate for a lack of proprioception, supporting the auditory-proprioception substitution hypothesis. However, sonification would act as a " sensory prosthesis " helping deafferented subjects to better feel their movements, without permanently modifying their motor performance once the prosthesis is removed. Potential clinical applications for motor rehabilitation are numerous: people with a limb prosthesis, with a stroke, or with some peripheral nerve injury may potentially be interested.

International audience; The quality of handwriting is evaluated from the visual inspection of its legibility and not from the movement that generates the trace. Although handwriting is achieved in silence, adding sounds to handwriting movement might help towards its perception, provided that these sounds are meaningful. This study evaluated the ability to judge handwriting quality from the auditory perception of the underlying sonified movement, without seeing the written trace. In a first experiment, samples of a word written by children with dysgraphia, proficient children writers, and proficient adult writers were collected with a graphic tablet. Then, the pen velocity, the fluency, and the axial pen pressure were sonified in order to create 45 audio files. In a second experiment, these files were presented to 48 adult listeners who had to mark the underlying unseen handwriting. In order to evaluate the relevance of the sonification strategy, two experimental conditions were compared. In a first ‘implicit’ condition, the listeners made their judgment without any knowledge of the mapping between the sounds and the handwriting variables. In a second ‘explicit’ condition, they knew what the sonified variables corresponded to and the evaluation criteria. Results showed that, under the implicit condition, two thirds of the listeners marked the three groups of writers differently. In the explicit condition, all listeners marked the dysgraphic handwriting lower than that of the two other groups. In a third experiment, the scores given from the auditory evaluation were compared to the scores given by 16 other adults from the visual evaluation of the trace. Results revealed that auditory evaluation was more relevant than the visual evaluation for evaluating a dysgraphic handwriting. Handwriting sonification might therefore be a relevant tool allowing a therapist to complete the visual assessment of the written trace byan auditory control of the handwriting movement quality.

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