Contact Info

Hisayuki Nagashima

Tokyo Institute of Technology

Yokohama

226-8503

Japan

Phone:     +81-3-5448-4380

hisakun@mbf.sphere.ne.jp

Date/Time Last Modified: 05/06/2002 at 05:18 am GMT

Presentation Type: Platform/Poster

Theme 1: Cognition and Behavior

Subtheme 1: Human Cognition and Behavior

Topic 1: Other higher functions

Theme 2: Sensory Systems

Subtheme 2: Vision

Topic 2: Extrastriate visual cortex: Sensorimotor integration

Abstract Title: SENSORIMOTOR COORDINATION REVEALED IN MICRO-SLIPS

Contributing Authors: H. Nagashima1; K. Mogi2*

Institutions:

1. Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, Yokohama, Japan

2. Sony Computer Science Laboratories, Tokyo, Japan

Key words: SENSORIMOTOR, HAND, CONTROL, VISION

Abstract: Voluntary human hand movements sometimes exhibit transient and microscopic deviations ("micro-slips") from their planned trajectories. For example, when trying to make a cup of coffee, hand movements of the subjects are observed to exhibit small deviations from the expected smooth trajectory more than twice a minute (Reed and Schoenherr 1992, Suzuki and Sasaki 2001). We investigated the nature of such small deviations of hand movements using data gloves (Immersion, San Jose, U.S.A.), simultaneously measuring eye movements by EMR-8 (NAC Image Technologies, Tokyo, Japan). When compared with the occurrence of word slips during text reading and voluntary speech, the occurrence of hand micro-slips shows similar temporal statistics. The trajectories of eye gaze and the hand joints plotted in the phase space exhibit characteristic spatio-temporal patterns before and during the micro-slips. We define some invariants in terms of dynamical systems properties for various cases of micro-slips, such as hesitation, change of trajectory, touching irrelevant objects, and change of hand posture. We discuss the implications of our findings for the nature of sensory-motor coordination and neural mechanisms of voluntary movements. We suggest the possibility that the occurrence of "micro-slips" is a byproduct of the "switchability" ( Bernstein 1996) of goal-directed motor output, exhibited in a broad range of motor processes such as speech and hand movements.