Tomoko Aoki

Prefectural University of Kumamoto

Does the dynamic dominance hypothesis apply to control of the fingers?

Handedness is arguably the most prominent asymmetry in neural control of human movement, with a hand preference occurring in more than 90% of any human population. The cause of hand preference in terms of the underlying right-left differences in performance ability remains poorly understood, however. Sainburg and Kalakanis (2000) first proposed the “dynamic dominance hypothesis,” having observed that during fast aimed arm movements, the dominant arm appeared more specialized for dynamic functions, dealing more efficiently with dynamic inter-limb torque patterns to produce straight-line hand path trajectories, while the non-dominant arm appeared more specialized for static functions, achieving more accurate control of final position. The present study examined the extent to which the dynamic dominance hypothesis might apply as well to control of finger movements. We studied four simple tasks performed by healthy human subjects using their index fingers on a small touchscreen. Consistent with dynamic dominance hypothesis, we found in right-handers that center-out trajectories were straighter, and slips during circle tracking were smaller for the dominant right index finger than for the non-dominant left. The opposite pattern was not found in left-handers, however, nor did we observe higher accuracy in control of final position for the non-dominant hand in either right- or left-handers. Taken together with studies of isometric force distribution among the fingers (Zhang et al. 2006), our findings suggest that the factors underlying dynamic dominance in arm movements may not extend fully to finger movements.

Reference

1)     Sainburg RL and Kalakanis D.  Difference in control of limb dynamics during dominant and nondominant arm reaching. J Neurophysiol 83: 2661-2675, 2000.

2)     Zhang W, Sainburg RL, Zatsiorsky VM, and Latash ML.  Hand dominance and multi-finger synergies. Neuroscience Letters 409: 200-204, 2006.