The Spatio-Temporal Structure of Force Variability in Static Grasp Suggests a Continually Active Neural Controller

Fingertip forces during simple and static tripod grasp exhibit a surprisingly rich dynamics [1]. Here we explore the hypothesis that, even for this apparently simple manipulation task, these fluctuations are shaped by a neural controller rather than by signal-dependent motor noise. We fed band-limited noise processes scaled to mean force level into a 21-muscle model of 3-finger grasp, and compare model output with experimental force recordings. We find that the spatial and spectral characteristics of simulated force fluctuations differed greatly from those observed in actual static tripod grasp. In light of current literature [2], we propose that a continually active neural controller is at work even for this simplest example of multifinger manipulation.