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Susan Ross, Mark Mon-Williams; The development of prehension in normal and special need populations. Journal of Vision 2004;4(8):407. doi: 10.1167/4.8.407.
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The development of prehension was studied in five groups of children (n=10 for each group) aged between 5 and 12 years. The experiment also involved 10 children with developmental coordination disorder. The control children were all screened on standardised cognitive and movement skill batteries to ensure that they had no neurological abnormalities. The tasks involved the children reaching to grasp objects with different sized grasping surfaces placed at different distances with their preferred and non-preferred hand. We also investigated bimanual coordination in a precision task that required reach-to-grasps to two different objects and locations at the same time. In our paradigm, the two objects were either at the same distance or one object was closer or further than the other. In the same way, the grasping surface could be the same or different so that one hand had to reach to an object with greater accuracy constraints than the other hand. Variables such as total movement time, peak speed and maximum grip aperture were examined as well as a quantification of the extent to which both arms behaved in synchrony. In an earlier bimanual study in adults we found that the two hands always start moving synchronously with the movement consisting of two phases: (i) an initial phase (IP) during which the hand moved forwards and the fingers pre-formed an appropriate aperture before stopping at the object; (ii) a completion phase (CP) during which the finger and thumb closed to contact the object. The general pattern of findings was similar in the control children but clear developmental differences emerged in both the quantitative and qualitative pattern of the movements. The children with DCD were found to exhibit abnormal patterns of prehension even when compared to children of the same ‘motor age’. The findings represent one of the most comprehensive studies of prehensile control in children with normal and abnormal developmental histories.
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