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Spatial and physical frames of reference in positioning a limb
S R Garrett1, C Pagano, G Austin
1Center for the Ecological Study of Perception and Action, University of Connecticut, Storrs 06268, USA. srg93001@uconnvm.uconn.edu
Abstract:
Splints attached to the right forearm were used to rotate the forearm's physical reference frame, as defined by the eigenvectors of its inertia tensor, relative to its spatial reference frame. In two experiments, when subjects were required to orient the forearm parallel to, or at 45 degrees to, the environmental horizontal, they produced limb orientations that were systematically deflected from the forearm's longitudinal spatial axis in the direction of the forearm's physical axes. The position sense seems to be based on inertial eigenvectors rather than on joint angles or gravitational torques.