Fig. 1.

Experimental setup and raw traces. A shows a subject standing on the force platform in the tandem posture. Electronic goggles worn by the subjects allowed control of vision inflow via a TTL signal. B shows the raw traces of ML CoP position (1 trial) in the mentally idle (black traces) and counting-backward (gray traces) conditions during addition (left) and withdrawal (right) of vision. C shows the ML CoP velocity traces of the same trials. D shows the level of ML CoP velocity of oscillation (average of 92 rectified ML CoP velocity traces). The horizontal segments with arrowheads over the level of ML CoP oscillation trace indicate the time windows in which the mean level of oscillation was calculated in the presence and in the absence of vision.