Naturalistic 3D Arm Movements can be Decomposed into Motion Primitives
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1
Ruhr-University Bochum, Institut für Neuroinformatik, Germany
How does the brain generate temporally and spatially coordinated, fluent arm movements? How are they affected by the presence of obstacles? And is it possible to identify elementary movements, called primitives, which can be combined to complex movements?
To approach these questions we investigated naturalistic 3D human arm movements during obstacle avoidance tasks. Experiments show that movement paths are largely planar and that the plane is chosen before movement onset. Additional investigations of different obstacle locations and heights reveal that the choice of movement plane reflects obstacle properties. Obstacles affect the movement path right from the beginning and do not act only locally in a small zone of influence. This implies that movement execution and control are always preceded by perception and initial planning.
As direct consequence of planarity, we decompose the trajectory into the transport and the lift/descend primitives. While the first describes a straight movement from the initial position to the target position, the latter represents up- and downward movements within the chosen plane. The two react independently to changing obstacle properties: shifting the obstacle between start and target does not change the lift primitive (being constantly bell-shaped), while the transport primitive is delayed depending on proximity of the obstacle. Further, the lift/descend primitive scales with obstacle height, while the transport primitive varies only sparsely. This autonomy of each primitive may imply their independent planning and execution by the CNS.
With this decomposition into movement primitives we can also explain observed phenomena like the formation and modulation of a double peak velocity structure during obstacle avoidance movements. Furthermore, it allows deeper insights into Flash and Hogan’s principle of local isochrony, even enabling a natural extension.
Altogether, our investigations show that naturalistic 3D obstacle avoidance movements are surprisingly regular. Their kinematic structure can be understood in terms of independent and invariant movement primitives: lift/descent and transport.
Keywords:
3D human arm movements,
motor control,
movement primitives,
obstacle avoidance
Conference:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011.
Presentation Type:
Poster
Topic:
motor control (please use "motor control" as keyword)
Citation:
Grimme
B,
Reimann
H and
Schöner
G
(2011). Naturalistic 3D Arm Movements can be Decomposed into Motion Primitives.
Front. Comput. Neurosci.
Conference Abstract:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011.
doi: 10.3389/conf.fncom.2011.53.00210
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Received:
18 Aug 2011;
Published Online:
04 Oct 2011.
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Correspondence:
Mrs. Britta Grimme, Ruhr-University Bochum, Institut für Neuroinformatik, Bochum, 44801, Germany, britta.grimme@ini.rub.de