2015 Volume 14 Issue 1 Pages 1-6
We investigated the effects of increase of attentional dispersion on anticipatory postural control during unilateral arm abduction. Fifteen healthy young adults performed right arm abduction for a target imperative stimulus under the three types of attentional dispersion conditions. The imperative stimulus was presented at one of two, four or six positions, following a cue signal. By the number of the cue signal, subjects either focused their attention on the position or divided attention into two, four or six positions. The reaction time of the middle deltoid (MD) and onset time of erector spinae (ES) and gluteus medius (GM) were measured. MD reaction time was significantly longer with attentional dispersion than with attentional focusing in all position conditions (p < 0.05), and longer in four- or six-position conditions than in two-position condition with both attentional state (p < 0.001). Onset time of ES and GM showed no significant difference between attentional focusing and dispersion in two-position condition, however was significantly later with attentional dispersion than with attentional focusing in four- and six-position conditions (p < 0.05). Furthermore, onset time of GM with attentional dispersion was significantly later in four- or six-position conditions than in two-position condition (p < 0.05). These results suggested that the effects of attentional dispersion would become greater as increase of the number of positions where attention was directed and reach plateau until four positions. In relation to these changes, onset time of postural muscles became clearly later with attentional dispersion to four positions and over.