Human Movement Science 32 (2013) 997–998
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Human Movement Science
15th International Graphonomics Society Conference (IGS 2011) This editorial summarizes six contributions from the 2011 International Graphonomics Conference held in Cancun, Mexico. These contributions are a representative sample of the research areas relevant to the ﬁeld of graphonomics, including skill development, computational theories, and disorders of graphonomics, which were showcased at the Biennial Meeting. The Accardo, Genna and Borean’s study investigated a large number of handwriting kinematic parameters from 218 right-handed Italian school children from 2nd to 8th grade. As such, it provides useful normative data that are potentially useful for assessing handwriting development and planned interventions in children. The Kostrubiec, Danna and Zanone’s contribution is an attempt to demonstrate that handwriting movements result from the generation of coordination patterns that obey oscillatory dynamics, as defended by the Coordination Dynamics (Kelso, 1995). Anchored in the theoretical background, the authors looked at testing the relationships between attention (which would reﬂect the cost needed to assemble or disassemble a motor pattern) and the production of stable or preferred graphic patterns. They thus invited participants to produce ellipses with various relative phases at different frequencies, while responding as fast as possible to an auditory signal. As expected, their data showed that as stability decreased, attentional cost increased, a covariation that would be an intrinsic property of all systems involving oscillatory coupled components, though this correlation failed to be observed at the lowest movement frequency. The paper concluded with some reﬂections on the possible explanations of poor letter legibility (adjustment of the amplitude of the oscillatory movements). These suggestions could however be disputed by some, as some forms of letter illegibility (e.g., disruptions in the trajectory so that it appears as a concatenation of small segments) seem to give more support to classical views of letter movement programming. The Plamondon, Djioua and Mathieu’s study concerns the examination of delays between bursts of EMG of antagonist muscles recruited during rapid hand movements using experiments and simulations of the Delta-lognormal model of neuromuscular function. According to this theory, the production of rapid human movements involves the activation of two neuromuscular systems (agonist and antagonist) that dictate the parameters of movement production (e.g., direction of movement). Each of these systems consists of sequential and parallel components such that each component interacts serially with its nearest neighbor and in a hierarchically parallel manner with more distal components. The different hierarchical couplings that exist in a given synergy can be estimated assuming a proportionality relationship between the cumulative time delays of the different stages of the equivalent sequential representation of such synergy. The authors showed high-correlation between the timing of the burst of activity generated by each muscle, supporting the cumulative delays in the hypothesized impulse response, thereby providing validation for their kinematic model.
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Editorial / Human Movement Science 32 (2013) 997–998
The contribution by O’Reilly and Plamondon, also related to the Delta-lognormal model of rapid human movements, focuses on the agonist-antagonist interaction in speed/accuracy tradeoff. Speciﬁcally, this study uses mathematical modeling to understand how agonist and antagonist forces covary as endpoint precision requirements change. The Delta-lognormal model is therefore applied to movement trajectories associated with a variety of indexes of difﬁculty and the authors report on their observation of tighter coupling of impulse parameters for more difﬁcult movements. On the other hand, accuracy demands reduced the magnitude of correlations involving timing. New hypotheses are presented based on the above results. The Rosenblum, Engel-Yeger and Fogel’s study investigated the relationships between age, executive functions control and handwriting performances in four groups of healthy adults, aged 31–45 yrs, 46– 60 yrs, 61–75 yrs and above 76 years of age. The executive functions control was assessed by means of the Behavioral Assessment of the Dysexecutive Syndrome tool, which revealed to be a reliable and valid tool, since the authors reported a gradual decline in executive functions as age increased with this instrument, in conformity with the current literature. Age appeared as a strong and signiﬁcant predictor of this decline. Handwriting performances were also assessed objectively, with temporal and spatial measures of handwriting movements recorded with a computerized system. Again, in line with previous studies, the authors found an increase in the in-air time in writing and in letter size as age progressed, reﬂecting increasing difﬁculties in planning spatio-temporal parameters of ﬁne distal movements with aging. Like for the decline in executive functions, age acted as an important and signiﬁcant predictor of handwriting movement modiﬁcations. However, the key ﬁnding was that executive functions control did not result in a signiﬁcant predictor of handwriting performance once the age effect was controlled. This indeed appears contradictory with the proposal that changes in handwriting movements with aging are due to increasing difﬁculties in planning activities. The authors suggest that other measures of executive functioning may be required, which is a valuable suggestion but quite contradictory with the conclusion that the instrument used in the present study is a valid tool. The last contribution concerns the Pan and Van Gemmert’s study which considers the transfer of training for various parameters of a hand aiming task. The authors deploy three models of bilateral transfer (access, cross-activation, and dynamic dominance) to test transfer of training. Subjects were required to make point-to-point drawing movements while adapting to a visual distortion resulting in visual feedback with a 45° rotation and a movement gain of 2 for pen movements. The authors examined performance of the non-dominant hand after practice of the dominant hand in half of the subjects, while performance of the dominant hand was examined after practice with the non-dominant hand of the other half of the subjects. Results showed different patterns of transfer at the kinematic level that depended on the learning condition. The authors also concluded that only the dynamic dominance model could account for the transfer of training effects as the ﬁrst two models (access and cross-activation) are ruled-out as they only predict transfer in one direction. Acknowledgements We would like to thank the guest reviewers, who reviewed the manuscripts submitted for the special issue. Guest Editors Jose L. Contreras-Vidal Annie Vinter Douglas Rogers