Kinematic properties of on-line error corrections in the monkey

Abstract

Despite the abundant experimental evidence for the irregular, multipeaked velocity profiles that often characterize rapid human limb movements, there is currently little agreement on how to interpret these phenomena. While in some studies these irregularities have been interpreted as reflecting a continuous control process, in others the irregularities are considered to be evidence for the existence of discrete movement primitives that are initiated by an intermittent controller. Here we introduce a novel "soft symmetry" method for analyzing irregular movements and decomposing them into their discrete movement primitives. We applied this method to analyze rapid pronation/supination wrist movements in monkeys during a one-dimensional tracking task. We showed that the properties of the extracted overlapping submovements (OSMs) were very similar to those of single, regular movements, despite the fact that the decomposition algorithm did not restrict the extracted submovements to a particular shape. In addition we showed that the movement primitives corrected preceding primitives and that the correction initiation time was highly variable, and thus could not be explained by the relatively fixed sensorimotor delay. These results argue against the interpretation of movement irregularities as reflecting a continuous control process and reinforce the hypothesis that movement irregularities result from an intermittent control mechanism. Demonstrating these phenomena in non-human primates will allow neurophysiological investigation of the neural mechanisms involved in these corrections.

Parabolic movement primitives and cortical states: merging optimality with geometric invariance

“…The existence of motor primitives was demonstrated at the level of forces generated by muscles operating on the limbs (Bizzi et al 1991;Giszter et al 1993;Nichols 1994;Kargo and Giszter 2000;Mussa-Ivaldi and Bizzi 2000;Mussa-Ivaldi and Solla 2004), at the level of muscle synergies (Tresch et al 1999;d'Avella et al 2003;Hart and Giszter 2004;Ivanenko et al 2004Ivanenko et al , 2005d'Avella and Bizzi 2005;d'Avella et al 2006), at the level of motion kinematics (Morasso and Mussa-Ivaldi 1982;Flash and Henis 1991;Burdet and Milner 1998;Krebs et al 1999;Sanger 2000;Rohrer and Hogan 2003;Fishbach et al 2005;Rohrer and Hogan 2006), and at the level of units of computation in the sensorimotor system (van Zuylen et al 1988;Thoroughman and Shadmehr 2000).…”

Individual Premotor Drive Pulses, Not Time-Varying Synergies, Are the Units of Adjustment for Limb Trajectories Constructed in Spinal Cord

“…Kinematic strokes of specific features have been proposed as high-level or kinematic planning primitives (Viviani and Terzuolo, 1982;Hogan, 1984;Flash and Hogan, 1985;Sanger, 2000;Schaal et al, 2003;Sosnik et al, 2004;Flash and Hochner, 2005). Unit strokes or unimodal kinematic primitives, identified at the trajectory level, are used to examine adjustments and tracking (Burdet and Milner, 1998;Novak et al, 2002;Roitman et al, 2004;Fishbach et al, 2005Fishbach et al, , 2007, motor learning (Sosnik et al, 2004;Pasalar et al, 2005), and recovery of function (Doeringer and Hogan 1998;Krebs et al, 1999;Rohrer et al, 2004).…”

Quantitative evaluation of upper-limb motor control in robot-aided rehabilitation

“…Several studies point out that human motion can be decomposed in elementary units, named submovements [43], probably originated by a ''neural controller'' in the brain [1,10,12,30,36,37,39,40,55]. Like primitives in natural and computer languages can be combined to generate a grammar of more complex constructs, the central nervous system can combine these elementary units to generate a manifold of more complex motor behaviors.…”