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. Author manuscript; available in PMC: 2018 Feb 1.
Published in final edited form as: Exp Brain Res. 2016 Oct 26;235(2):481–496. doi: 10.1007/s00221-016-4809-z

Figure 1.

Figure 1

A: A schematic illustration of the notions of actual coordinate (AC), actual orientation (AO), referent coordinate (RC), and referent orientation (RO) for the task of four-finger force-moment production. Note that total force (FTOT) is a linear function of (RC – AC), while total moment (MTOT) is a function of (RO – AO). B: A schematic illustration of the concept of RC-back-coupling. Direct process starts with a change in RC resulting in a change in force (F). A slower process leading to a change in RC (ΔRC) toward AC results in a force drop. The scheme on the right shows a potential field (dashed line) corresponding to a value of RC. Apparent stiffness and apparent rotational stiffness are shown as k and kR.