Figure 3.
Fluctuations in direction of the fingertip force vector after finger contact. a, Force angle data [φforce(t)] from all subjects for all three initial conditions. The first 10 ms are grayed out and excluded for all analyses. Even for the remaining time segment, the force direction appears to fluctuate much more for the motion condition than for either the relaxed or preactivated conditions. The peak force angle deviation for the motion condition (blue) occurs around 8 ms. We are conservative in our analyses by excluding the first 10 ms because the force data were clearly reliable well before 8 ms (Fig. 1a, blue traces). b, The peak force angle deviation [max(φforce)] decreased from motion to relaxed to preactivated conditions. All differences were statistically significant. c, The variance in force direction [var(φforce)] also decreased from motion to relaxed to preactivated conditions and all differences were statistically significant.