The Contribution of the Parietal Lobes to Speaking and Writing

The left parietal lobe has been proposed as a major language area. However, parietal cortical function is more usually considered in terms of the control of actions, contributing both to attention and cross-modal integration of external and reafferent sensory cues. We used positron emission tomography to study normal subjects while they overtly generated narratives, both spoken and written. The purpose was to identify the parietal contribution to the modality-specific sensorimotor control of communication, separate from amodal linguistic and memory processes involved in generating a narrative. The majority of left and right parietal activity was associated with the execution of writing under visual and somatosensory control irrespective of whether the output was a narrative or repetitive reproduction of a single grapheme. In contrast, action-related parietal activity during speech production was confined to primary somatosensory cortex. The only parietal area with a pattern of activity compatible with an amodal central role in communication was the ventral part of the left angular gyrus (AG). The results of this study indicate that the cognitive processing of language within the parietal lobe is confined to the AG and that the major contribution of parietal cortex to communication is in the sensorimotor control of writing

Comparaison des habiletés liées à la dextérité manuelle et à l'intégration visuo-motrice entre les enfants nés prématurés et les enfants nés à terme âgés de 5 ans 9 mois

Introduction : Les enfants prématurés (EP) courent un risque jusqu’à 5 fois plus élevé d’avoir des difficultés en écriture que leurs pairs nés à terme (AT). Ainsi, il est pertinent d’étudier les composantes pré-requises à l’apprentissage de l’écriture. Objectifs : Comparer les habiletés d’intégration visuo-motrice et de dextérité manuelle de 3 groupes d’enfants âgés de 5.9 ans. Méthodologie : Le groupe 1 est formé de 23 EP (< 28 semaines), le groupe 2 est constitué de 31 EP (28-32 semaines) et le groupe 3 regroupe 35 enfants AT. Les habiletés d’intégration visuo-motrice (Beery-VMI) et de dextérité manuelle (M-ABC) sont évaluées en laboratoire. Résultats : Sur toutes les épreuves mesurées, les enfants du groupe 1 ont une performance inférieure à ceux des groupes 2 et 3. Conclusion: Il existe une hétérogénéité au sein du groupe EP. Les résultats mettent en évidence l’importance d’un suivi de cette population avant l’entrée scolaire

The effect of graphomotor exercises and music on normal children and children with attention deficit hyperactivity disorder

Although drug therapy is the more common treatment of ADHD (attention deficit hyperactivity disorder), and has been shown to reduce symptoms, the benefits of the theraputic drugs are temporary, and the therapy can have adverse side effects. For these reasons, many prefer not to use drug therapy for ADHD. Alternative treatments have been shown to have some efficacy, especially when used in conjunction with drug therapy. Dynamic Systems theory suggests that an intervention which combines graphomotor exercises with music may have a positive effect on a child\u27s behavior and attention. A 2 x 2 pretest-posttest design tested the hypothesis that both children diagnosed with ADHD as well as children without ADHD would significantly improve on measures of attention, behavior inhibition and handwriting when those children received the graphomotor and music intervention. The intervention was designed according to the instructions in the handbook Training the Brain to Pay Attention the Write Way authored by Farmer and published by Writebrain Press in Denver, Colorado in 1993

The effects of external focus of attention exercise rehabilitation on dual task walking in Parkinson\u27s disease

Parkinson’s disease impairs control of well-learned movements, and therefore, individuals with Parkinson’s disease are forced to walk with greater conscious control. This causes difficulties while walking and completing a secondary task simultaneously (dual tasking), in that distractions from conscious control of walking increase the risk of falls and injury. Although, attention-based exercise may be a potential avenue to decrease the demands associated with walking in Parkinson’s disease. For example, an external focus of attention (on manipulated objects) has been found to recruit the networks that are important for walking with little conscious control (automatic control networks). In contrast, an internal focus (on limb movements) has been found to recruit conscious control networks. Unexpectedly, an external focus of attention (compared to an internal) has been found to improve postural stability in Parkinson’s disease (compared to internal) despite that this attentional focus recruits damaged automatic control circuits. Therefore, promoting an external focus during goal-based exercise may improve upon automatic control functioning, and therefore, improve the ability to dual task and reduce the severity of symptoms. A parallel group, single blind, randomized controlled trial was conducted. Thirty-nine participants with Parkinson’s disease were randomized to one of two exercise groups: 1) External focus of attention (focus on movement of coloured labels attached to limbs, n=19) or 2) Internal focus of attention (focus on movement of limbs, n=20). Both exercise groups completed 33 one-hour goal-based exercise sessions over 11 weeks. Eleven participants were assigned to a non-exercise control group. Walking ability (single and dual tasking) and symptom severity (Unified Parkinson’s disease Rating Scale motor subsection [UPDRS-III] ON and OFF dopamine medications) were assessed before and after (pre/post) the completion of the program, and 8 weeks after exercise cessation (washout). As a result of the intervention, walking ability while completing a secondary task became significantly worse in the Internal focus of attention exercise group, while dual tasking ability did not change in the external group. Symptom severity significantly improved in only the External group from pre to post. From pre to washout, dual task walking ability and motor symptom severity improved in both exercise groups. However, the Internal group had increased errors on the dual task, whereas the External group did not, indicating that improvements were only demonstrated in the External group. Thus, External focus of attention exercise may provide benefits that establish a foundation for improvements to dual task walking ability in Parkinson’s disease, whereas adopting an Internal focus of attention during goal-based exercise appeared to increase reliance on conscious control of movement, hindering dual tasking ability. Additionally, after the exercise program, greater improvements to symptom severity were found after externally focused exercise compared to internally focused. Together, these findings indicate that focusing externally on the manipulation of coloured labels while exercising provides greater rehabilitation effectiveness in Parkinson’s disease compared to focusing internally on limb movements

The neural substrates of graphomotor sequence learning.

Performing sequences of movements easily and automatically is an integral part of our everyday lives. This dissertation examines how a set of individual movements are assembled into a movement sequence, focusing on the neural regions involved, and the timing of their participation. A second, related question is whether the order of encoding of the individual movements can be detected with kinematic and neuroimaging methods. Understanding how sequences are learned is important for expanding our knowledge of how the brain performs neural computations within healthy persons, and of the alterations of these processes in persons with neurological disorders. To examine these questions, we combined behavioral, kinematic and neuroimaging methods to examine motor sequence learning in healthy adults. The behavioral task involved subjects learning to copy a novel sequence of line-pairs (a graphomotor trajectory sequence learning paradigm) while blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) data were simultaneously acquired. Sequence learning, measured by normalized jerk, was best characterized by a curve with a double exponential fit, implying that an early, fast learning process (time-bins 1-2) merged with a slower learning process (bins 3-5). The early portion of the sequence learning process was characterized by dorsal and ventral visual stream activation; dorsal lateral premotor cortical activity; and deactivation of the anterior putamen, head of the caudate nucleus and posterior vermis. The deactivation of portions of the basal ganglia and cerebellum during the early phase of sequence learning may indicate that these regions were being reset, due to the high number of errors being produced. The pattern of neural activity in the the second, slower phase of sequence learning suggests that emphasis in the sequence learning process had shifted from visuomotor mapping to improving the kinematic and dynamic motor plans for the new sequences (sequence encoding). Taken together, a model of graphomotor sequence learning emerges, including patterns of neural activation and functional connectivity that correspond to changes in subject performance. This model adds to our current understanding of the neural substrates of graphomotor sequence learning, and may be important in explaining the alterations to these networks in persons with neurodegenerative disorders

Dynamique de coordination dans la formation de la trace écrite chez l'adulte et l'enfant

L'écriture est un mouvement parmi les plus complexes et les plus rapides de notre répertoire moteur. Elle requiert l'activité coordonnée de nombreux muscles et articulations du membre supérieur pour produire une succession de formes conventionnelles, des lettres, de manière suffisamment précise pour être reconnues. Ce travail de thèse a pour objectif de comprendre 1) comment les individus arrivent à contrôler et à coordonner l'ensemble des éléments du système moteur (ici graphomoteur) pour accomplir une telle tâche et 2) comment s'acquiert cette habileté motrice. Les concepts et outils de l'approche dynamique de la coordination motrice permettent d'envisager la formation de la trace écrite comme un processus auto-organisé qui répond aux modèles d'oscillateurs couplés. A partir de la modélisation de l'écriture en termes de couplage non linéaire de deux oscillateurs orthogonaux abstraits, la phase relative entre ces deux oscillateurs permet d'observer, de comprendre et de prédire la formation, le maintien et la dégradation de la trace écrite. Dans notre première étude, centrée sur la coordination graphomotrice adulte dans la reproduction de formes géométriques simples, nous avons confirmé qu'une ellipse d'excentricité intermédiaire et un trait sont plus faciles à tracer que toutes les autres formes elliptiques. Nous avons de plus montré que la production préférentielle d'ellipses d'excentricité intermédiaire est biaisée en faveur de formes plus arrondies lorsque leur orientation devient contraignante. Dans notre deuxième étude, centrée sur la coordination graphomotrice chez l'enfant de 7 à 11 ans, nous avons révélé que les enfants sont plus précis et plus stables dans le tracé de cercles que dans le tracé d'ellipses, préférentiel chez l'adulte. Nos résultats confirment que, comme tout mouvement rythmique coordonné, la stabilité des modes de coordination (grapho)motrice détermine la manière d'écrire.Handwriting movement is through one of the fastest and the most complex known to human motor behaviors. This ability involves a sophisticated coordination of many muscles and joints recruited in order to produce a trace sufficiently consistent and precise to be recognized as letters. The aim of the present thesis is to understand 1) how we succeed in controlling and coordinating the motor (here graphomotor) system to realize this task and 2) how this motor behavior is acquired. Concepts and tools of the dynamical approach of the motor coordination permit to consider the written trajectory formation as a self-organized process resulting from the dynamics of non-linear coupled oscillators. From the modeling of handwriting movements in terms of the non-linear coupling of two abstract orthogonal oscillators, the relative phase between these oscillators make possible to observe, to understand and to predict the formation, the maintaining and the deterioration of the written trajectory. In a first study based on graphic coordination of adults in production of simple geometrical shapes, we confirmed that the ellipse with intermediate eccentricity and the line are easier to produce that all other shapes. Moreover, we demonstrated that the preferential production of intermediate ellipse is biased toward a more circular shape when orientation becomes a constraint. In a second study based on graphic coordination of 7 to 11 year-old children, we revealed that children are more precise and stable in circle drawing than in ellipse drawing, preferential in adults. Our results confirm that, as all cyclic coordinated movements, the stability of the motor coordination patterns determine the way of handwriting