9I制作厂免费

Dario G Liebermann, PhD

Department of Physical Therapy, Sackler Faculty of Medicine, University of Tel Aviv - Israel

Human movements may express different internal states; e.g., removing the arm from a noxious source on the table looks different than intentionally flexing the arm to lift an object even though similar muscles may be activated. The identification of the internal states that drive such fundamentally different movements is facilitated by the recognition of invariant kinematic features (i.e., observable features that remain constant in spite of changes in load, direction and speed of movement or other factors). In the present study, it is argued that kinematic invariants express also higher-level motor solutions. For this purpose, spinal and supraspinal processes were simultaneously elicited (reflexive and voluntary motor responses, respectively). The two processes were described in terms of the temporal evolution of the 3D hand paths (i.e., the tangential velocity profiles). A 'vector superposition scheme' (Henis & Flash 1995) was hypothesized where reflex and voluntary movements integrated in order to produce 聽a global coherent response. Preliminary data showed that two different motor actions may combine in more than one way. Under the same conditions, sometimes they 'cooperate' following the hypothesized supersposition scheme and sometimes they 'compete' whereas the reflex perturbs the voluntary response. Theoretical and practical implications of this preliminary research are opened for discussion.