Imagining handwriting movements in a usual or unusual position: effect of posture congruency on visual and kinesthetic motor imagery.

Motor imagery has been used in training programs to improve the performance of motor skills. Handwriting movement may benefit from motor imagery training. To optimize the efficacy of this kind of training, it is important to identify the factors that facilitate the motor imagery process for handwriting movements. Several studies have shown that motor imagery is more easily achieved when there is maximum compatibility between the actual posture and the imagined movement. We, therefore, examined the effect of posture congruency on visual and kinesthetic motor imagery for handwriting movements. Adult participants had to write and imagine writing a sentence by focusing on the evocation of either the kinesthetic or visual consequences of the motion. Half the participants performed the motor imagery task in a congruent posture (sitting with a hand ready for writing), and half in an incongruent one (standing with arms crossed behind the back and fingers spread wide). The temporal similarity between actual and imagined movement times and the vividness of the motor imagery were evaluated. Results revealed that temporal similarity was stronger in the congruent posture condition than in the incongruent one. Furthermore, in the incongruent posture condition, participants reported greater difficulty forming a precise kinesthetic motor image of themselves writing than a visual image, whereas no difference was observed in the congruent posture condition. Taken together, our results show that postural information is taken into account during the mental simulation of handwriting movements. The implications of these findings for guiding the design of motor imagery training are discussed.

Motor imagery development and proprioceptive integration: Which sensory reweighting during childhood?

It is widely accepted that motor imagery development during childhood may be due to refinement of internal models of action. At the same time, gradual improvement of predictive motor control in children may reflect an increasing ability to integrate the proprioceptive afferences with other sources of sensory information (especially vision). The current study investigated the extent to which motor imagery refinement observed between 5 and 9 years of age was related to the increasing ability to integrate proprioceptive afferences with vision and audition signals. To attain this goal, we compared motor imagery performances of 96 children (32 5-year-olds, 32 7-year-olds, and 32 9-year-olds) who received either visual and auditory inputs (VA condition) or visual, auditory, and proprioceptive inputs (VAP condition) during the imagery task. Motor imagery capacity was evaluated by means of mental chronometry paradigm based on a walking task. Our results revealed that correlations between overt and covert movements gradually increased across age in either the VA or VAP condition. Most important, in 5- and 7-year-olds, covert walking times were significantly longer than overt walking times in the VAP condition, whereas covert walking times were not different from actual walking times in the VA condition. In 9-year-olds, covert walking times were not different from overt walking times in either the VAP or VA condition. We suggest that motor imagery refinement during childhood can be partially related to the ability to integrate proprioceptive inputs with other sources of sensory information. Furthermore, our results shed light on the sensory content of motor images in children.

Handwriting on a tablet screen: Role of visual and proprioceptive feedback in the control of movement by children and adults.

Tablets are increasingly being used in schools for a variety of handwriting tasks. Given that the control of handwriting relies on both visual and proprioceptive feedback, especially in younger writers, this raises the question of whether the texture of the tablet surface affects graphomotor execution. A series of recent studies found that when the smoothness of a tablet screen modifies proprioceptive feedback, the impact on graphomotor execution varies according to the level of the writer's handwriting skills. However, as the writing on the screen remained visible in these studies, participants may have compensated for the decrease in proprioceptive feedback by relying more heavily on visual information. The aim of the present study was therefore to unravel the respective contributions of different types of sensory feedback during handwriting development and, consequently, the compensatory role of visual information when children and adults have to write on a tablet. To this end, we asked second and fifth graders and adult participants to write letters and pseudowords on a plastic board placed on top of a tablet screen. Participants wrote on either the smooth or the granular side of the plastic board (manipulation of surface friction), and with normal vision or behind a shield that hid the hand and handwriting from direct view (manipulation of vision). Kinematic parameters and legibility were recorded to assess handwriting performances. Results revealed a significant interaction between proprioceptive and visual feedback on letter size, pen speed and legibility, regardless of participants' age. Furthermore, reducing the visual and proprioceptive feedback had a greater effect on the children's handwriting performances than on those of adults. Overall, the present study provides new insight into the contribution of the different types of sensory feedback and their interaction with handwriting development. In addition, our results on the impact of tablet surface on graphomotor execution will serve as useful pointers for improving the design of this tool for children, such as increasing the degree of friction of the screen surface.

Rôle des afférences proprioceptives dans le développement de l'imagerie motrice chez l'enfant.

To which extent is motor imagery (MI) development, commonly observed between the ages of 5 and 9, related to the increasing ability to integrate proprioceptive afferences for the control of action? This question was addressed in a study evaluating MI performance of 108 children aged 5, 7 and 9 years old. A mental chronometry paradigm based on a walking task was used. Integration of proprioceptive information was evaluated by comparing MI performance when children held an external load (5 % of the children weight) to when they did not. Results revealed that the external load affected MI performances of the 5 year olds. In 7 years old, MI performances remained unchanged whether they held an external load or not. At 9 years, holding an external load improved MI performances. Taken together, these results reveal that MI development could be linked to proprioceptive acuity refinement during childhood. These results are discussed according to the relation between MI, proprioceptive development and development of internal models of action during childhood. (PsycINFO Database Record

Motor imagery for walking: a comparison between cerebral palsy adolescents with hemiplegia and diplegia.

The goal of the study was to investigate whether motor imagery (MI) could be observed in cerebral palsy (CP) participants presenting a bilateral affected body side (diplegia) as it has been previously revealed in participants presenting a unilateral body affected sided (hemiplegia). MI capacity for walking was investigated in CP adolescents diagnosed with hemiplegia (n=10) or diplegia (n=10) and in adolescents with typical motor development (n=10). Participants were explicitly asked to imagine walking before and after actually walking toward a target located at 4 m and 8 m. Movement durations for executed and imagined trials were recorded. ANOVA and Pearson's correlation analyses revealed the existence of time invariance between executed and imagined movement durations for the control group and both groups of CP participants. However, results revealed that MI capacity in CP participants was observed for the short distance (4 m) but not for the long distance (8 m). Moreover, even for short distance, CP participants performed worse than typical adolescents. These results are discussed inline of recent researches suggesting that MI in CP participants may not depend on the side of the lesion.

Assessment of motor imagery in cerebral palsy via mental chronometry: the case of walking.

Recent studies show varying results on whether motor imagery capacity is compromised in individuals with cerebral palsy (CP). Motor imagery studies in children predominantly used the implicit hand laterality task. In this task participants judge the laterality of displayed hand stimuli. A more explicit way of studying motor imagery is mental chronometry. This paradigm is based on the comparison between the movement durations of actually performing a task and imagining the same task. The current study explored motor imagery capacity in CP by means of mental chronometry of a whole body task. Movement durations of 20 individuals with CP (mean age=13 years, SD=3.6) were recorded in two conditions: actual walking and imagined walking. Six unique trajectories were used that varied in difficulty via manipulation of walking distance and path width. We found no main effect of condition (actual walking versus imagining) on movement durations. Difficulty of the walking trajectory did affect movement durations. In general, this was expressed by an increase in movement durations with increasing difficulty of the task. No interaction between task difficulty and movement condition was found. Our results show that task difficulty has similar effects on movement durations for both actual walking and imagined walking. These results exemplify that the tested individuals were able to use motor imagery in an explicit task involving walking. Previous studies using the implicit hand laterality task showed varying results on motor imagery capacity in CP. We therefore conclude that motor imagery capacity is task dependent and that an explicit paradigm as the one used in this study may reveal the true motor imagery capacity. The implications of these findings for the use of motor imagery training are discussed.