caa a22 4500 44535318X CHVBK 20180317142851.0 cr unu---uuuuu 170323e20110401xx s 000 0 eng 10.1007/s00221-011-2590-6 doi (NATIONALLICENCE)springer-10.1007/s00221-011-2590-6 Prehension of half-full and half-empty glasses: time and history effects on multi-digit coordination [Elektronische Daten] [Yao Sun, Vladimir Zatsiorsky, Mark Latash] We explored how digit forces and indices of digit coordination depend on the history of getting to a particular set of task parameters during static prehension tasks. The participants held in the right hand an instrumented handle with a light-weight container attached on top of the handle. At the beginning of each trial, the container could be empty, filled to the half with water (0.4l), or filled to the top (0.8l). The water was pumped in/out of the container at a constant, slow rate over 10s. At the end of each trial, the participants always held a half-filled container that has just been filled (Empty-Half), emptied (Full-Half) or stayed half-filled throughout the trial (Half-Only). Indices of covariation (synergy indices) of elemental variables (forces and moments of force produced by individual digits) stabilizing such performance variables as total normal force, total tangential force, and total moment of force were computed at two levels of an assumed control hierarchy. At the upper level, the task is shared between the thumb and virtual finger (an imagined digit with the mechanical action equal to that of the four fingers), while at the lower level the action of the virtual finger is shared among the actual four fingers. Filling or emptying the container led to a drop in the safety margin (proportion of grip force over the slipping threshold) below the values observed in the Half-Only condition. Synergy indices at both levels of the hierarchy showed changes over the Full-Half and Empty-Half condition. These changes could be monotonic (typical of moment of force and normal force) or non-monotonic (typical of tangential force). For both normal and tangential forces, higher synergy indices at the higher level of the hierarchy corresponded to lower indices at the lower level. Significant differences in synergy indices across conditions were seen at the final steady state showing that digit coordination during steady holding an object is history dependent. The observations support an earlier hypothesis on a trade-off between synergies at the two levels of a hierarchy. They also suggest that, when a change in task parameters is expected, the neural strategy may involve producing less stable (easier to change) actions. The results suggest that synergy indices may be highly sensitive to changes in a task variable and that effects of such changes persist after the changes are over. Springer-Verlag, 2011 Prehension nationallicence Safety margin nationallicence Synergy nationallicence History effects nationallicence Sun Yao Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut Zatsiorsky Vladimir Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut Latash Mark Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut Experimental Brain Research Springer-Verlag 209/4(2011-04-01), 571-585 0014-4819 209:4<571 2011 209 221 https://doi.org/10.1007/s00221-011-2590-6 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00221-011-2590-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sun Yao Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut NATIONALLICENCE 700 1- Zatsiorsky Vladimir Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut NATIONALLICENCE 700 1- Latash Mark Department of Kinesiology, Rec.Hall-268N, The Pennsylvania State University, 16802, University Park, PA, USA aut NATIONALLICENCE 773 0- Experimental Brain Research Springer-Verlag 209/4(2011-04-01), 571-585 0014-4819 209:4<571 2011 209 221 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer