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Mental representation of arm motion dynamics in children and adolescents.

Crognier L, Skoura X, Vinter A, Papaxanthis C - PLoS ONE (2013)

Bottom Line: We found that actual movement times were greater for leftward than rightward arm movements in all groups.Furthermore, significant differences between actual and mental times were found at 9 and 11 years of age in the leftward direction.However, this overestimation gradually decreased with age.

View Article: PubMed Central - PubMed

Affiliation: Université de Bourgogne, Unité de Formation et de Recherche en Sciences et Techniques des Activités Physiques et Sportives, Dijon, France.

ABSTRACT
Motor imagery, i.e., a mental state during which an individual internally represents an action without any overt motor output, is a potential tool to investigate action representation during development. Here, we took advantage of the inertial anisotropy phenomenon to investigate whether children can generate accurate motor predictions for movements with varying dynamics. Children (9 and 11 years), adolescents (14 years) and young adults (21 years) carried-out actual and mental arm movements in two different directions in the horizontal plane: rightwards (low inertia) and leftwards (high inertia). We recorded and compared actual and mental movement times. We found that actual movement times were greater for leftward than rightward arm movements in all groups. For mental movements, differences between leftward versus rightward movements were observed in the adults and adolescents, but not among the children. Furthermore, significant differences between actual and mental times were found at 9 and 11 years of age in the leftward direction. The ratio R/L (rightward direction/leftward direction), which indicates temporal differences between low inertia and high inertia movements, was inferior to 1 at all ages, except for the mental movements at 9 years of age, indicating than actual and mental movements were shorter for the rightward than leftward direction. Interestingly, while the ratio R/L of actual movements was constant across ages, it gradually decreased with age for mental movements. The ratio A/M (actual movement/mental movement), which indicates temporal differences between actual and mental movements, was near to 1 in the adults' groups, denoting accurate mental timing. In children and adolescents, an underestimation of mental movement times appeared for the leftward movements only. However, this overestimation gradually decreased with age. Our results showed a refinement in the motor imagery ability during development. Action representation reached maturation at adolescence, during which mental actions were tightly related to their actual production.

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Related in: MedlinePlus

Average values (+SE) of actual and imagined movement times are illustrated for the four age-groups and the two directions (L, left and R, right).Diamonds indicate significant differences between actual and mental movements. Stars indicate significant differences between right and left directions for both actual and mental movements.
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pone-0073042-g002: Average values (+SE) of actual and imagined movement times are illustrated for the four age-groups and the two directions (L, left and R, right).Diamonds indicate significant differences between actual and mental movements. Stars indicate significant differences between right and left directions for both actual and mental movements.

Mentions: In the current study, we took advantage of the inertial anisotropy phenomenon to investigate whether children can generate accurate motor predictions for movements with varying dynamics. In a two-joint mechanical system such as the upper-arm and the forearm, motion dynamics change according to movement direction [4], [40], [41]. For instance, when we reach with our right arm rightwards the movement is accomplished principally by the motion of the forearm; consequently, the mass of the upper arm contributes little to the total inertia of the arm. On the contrary, when we perform the same movement leftwards, we move both the upper-arm and forearm, increasing consequently the total inertia of the arm (see Fig. 1 and 2 for detailed explanations). Previous studies have reported that direction-dependent changes in arm dynamics influence movement time [4], [40], [42]. Specifically, for the same hand amplitudes, arm movements with high inertia are slower than arm movements with low inertia. It is important to note that the brain maintains accurate internal representations of the inertial anisotropy of the arm. For example, by means of a grip-force/load-force coupling paradigm, it has have been demonstrated that the brain accurately anticipates the inertial anisotropy of the right arm and therefore the direction-dependent changes in movement time [43]. Similarly, it has been shown that young adults accurately integrate these direction-depended temporal asymmetries into the motor imagery process [4], [42]. Specifically, actual and mental movement times were equivalent whatever the direction of the movement and both actual and mental movement times were shorter for lower inertia than high inertia directions.


Mental representation of arm motion dynamics in children and adolescents.

Crognier L, Skoura X, Vinter A, Papaxanthis C - PLoS ONE (2013)

Average values (+SE) of actual and imagined movement times are illustrated for the four age-groups and the two directions (L, left and R, right).Diamonds indicate significant differences between actual and mental movements. Stars indicate significant differences between right and left directions for both actual and mental movements.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3757012&req=5

pone-0073042-g002: Average values (+SE) of actual and imagined movement times are illustrated for the four age-groups and the two directions (L, left and R, right).Diamonds indicate significant differences between actual and mental movements. Stars indicate significant differences between right and left directions for both actual and mental movements.
Mentions: In the current study, we took advantage of the inertial anisotropy phenomenon to investigate whether children can generate accurate motor predictions for movements with varying dynamics. In a two-joint mechanical system such as the upper-arm and the forearm, motion dynamics change according to movement direction [4], [40], [41]. For instance, when we reach with our right arm rightwards the movement is accomplished principally by the motion of the forearm; consequently, the mass of the upper arm contributes little to the total inertia of the arm. On the contrary, when we perform the same movement leftwards, we move both the upper-arm and forearm, increasing consequently the total inertia of the arm (see Fig. 1 and 2 for detailed explanations). Previous studies have reported that direction-dependent changes in arm dynamics influence movement time [4], [40], [42]. Specifically, for the same hand amplitudes, arm movements with high inertia are slower than arm movements with low inertia. It is important to note that the brain maintains accurate internal representations of the inertial anisotropy of the arm. For example, by means of a grip-force/load-force coupling paradigm, it has have been demonstrated that the brain accurately anticipates the inertial anisotropy of the right arm and therefore the direction-dependent changes in movement time [43]. Similarly, it has been shown that young adults accurately integrate these direction-depended temporal asymmetries into the motor imagery process [4], [42]. Specifically, actual and mental movement times were equivalent whatever the direction of the movement and both actual and mental movement times were shorter for lower inertia than high inertia directions.

Bottom Line: We found that actual movement times were greater for leftward than rightward arm movements in all groups.Furthermore, significant differences between actual and mental times were found at 9 and 11 years of age in the leftward direction.However, this overestimation gradually decreased with age.

View Article: PubMed Central - PubMed

Affiliation: Université de Bourgogne, Unité de Formation et de Recherche en Sciences et Techniques des Activités Physiques et Sportives, Dijon, France.

ABSTRACT
Motor imagery, i.e., a mental state during which an individual internally represents an action without any overt motor output, is a potential tool to investigate action representation during development. Here, we took advantage of the inertial anisotropy phenomenon to investigate whether children can generate accurate motor predictions for movements with varying dynamics. Children (9 and 11 years), adolescents (14 years) and young adults (21 years) carried-out actual and mental arm movements in two different directions in the horizontal plane: rightwards (low inertia) and leftwards (high inertia). We recorded and compared actual and mental movement times. We found that actual movement times were greater for leftward than rightward arm movements in all groups. For mental movements, differences between leftward versus rightward movements were observed in the adults and adolescents, but not among the children. Furthermore, significant differences between actual and mental times were found at 9 and 11 years of age in the leftward direction. The ratio R/L (rightward direction/leftward direction), which indicates temporal differences between low inertia and high inertia movements, was inferior to 1 at all ages, except for the mental movements at 9 years of age, indicating than actual and mental movements were shorter for the rightward than leftward direction. Interestingly, while the ratio R/L of actual movements was constant across ages, it gradually decreased with age for mental movements. The ratio A/M (actual movement/mental movement), which indicates temporal differences between actual and mental movements, was near to 1 in the adults' groups, denoting accurate mental timing. In children and adolescents, an underestimation of mental movement times appeared for the leftward movements only. However, this overestimation gradually decreased with age. Our results showed a refinement in the motor imagery ability during development. Action representation reached maturation at adolescence, during which mental actions were tightly related to their actual production.

Show MeSH
Related in: MedlinePlus