Article

Similar effects have been reported for diverting attention from postural control
and increased anxiety on the characteristics of center-of-pressure (COP) time
series (decreased excursions and elevated mean power frequency). These effects
have also received similar interpretations in terms of increased postural
stiffness, suggesting that cognitive and affective manipulations have similar
influences on postural control. The present experiment tested this hypothesis by
comparing postural conditions involving manipulations of attention (diverting
attention from posture using cognitive and motor dual tasks) and anxiety
(standing at a height), and by complementing posturography with electromyographic
analyses to directly examine neuromuscular stiffness control. Affective and
cognitive manipulations had markedly different effects. Unlike the height
condition, diverting attention from balance induced smaller COP amplitudes and
higher sway frequencies. In addition, more regular COP trajectories (lower sample
entropy) were found in the height condition than the dual-task conditions,
suggesting elevated attentional investment in posture under the affective
manipulation. Finally, based on an analysis of the cross-correlation function
between anterior-posterior COP time series and enveloped calf muscle activity,
indications of tighter anticipatory neuromuscular control of posture were found
for the height condition only.
Our data suggest that affective and cognitive
perturbations have qualitatively different effects on postural control, and thus
are likely to be associated with different control processes, as evidenced by
differences in neuromuscular regulation and attentional investment in posture.
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Langue : ANGLAIS