The increased foreperiod duration to attain the neutral optimal preparation from sitting to standing.

The purpose of the present experiment was to investigate the effects of a neutral preparation during the foreperiod on motor and postural programming processes in a voluntary upper limb movement. The foreperiod duration (300, 500, 700 and 900 ms) and the postural condition (sitting vs standing) were manipulated using a neutral preparation (no advanced information during the preparatory signal). Thirteen subjects performed a raising arm movement with 1 kg load at the wrist. Premotor time, latency of the anticipatory postural adjustments and the vertical torque were calculated. A previous experiment showed that the optimal foreperiod duration (i.e. leading to the shortest premotor time) increased from sitting to standing in a selective preparation (Cuisinier et al. in Brain Res Bull 66(2):163-170, 2005). The present experiment replicated this finding in a neutral preparation. It was found that (1) this optimal foreperiod duration still increased from 500 ms in sitting to 700 ms in standing in a neutral preparation, (2) this increased optimal foreperiod duration resulted from a greater level of alertness necessary to control a more constrained posture in standing than in sitting, and (3) the existence of a temporal modulation in the central organization of the postural and focal commands was according to the foreperiod duration.