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A model of saccade generation based on parallel processing and competitive inhibition

Findlay, John M. and Walker, Robin (1999) A model of saccade generation based on parallel processing and competitive inhibition.

Short Abstract:

A hypothesis about sensorimotor integration (the lambda model) is described and applied to movement control and kinesthesia. The nervous system organizes positional frames of reference for the sensorimotor apparatus and produces active movements by shifting frames in terms of spatial coordinates. Kinematic and electromyographic patterns are not programmed but emerge from the dynamic interaction of the system's components, including external forces, within the designated frame of reference. Motoneuronal threshold properties and proprioceptive inputs to motoneurons may be important components in the physiological mechanism which produces positional frames of reference. The hypothesis that intentional movements are produced by shifting the frame of reference is extended to multi-muscle and multi-degrees of freedom systems by providing a solution for the redundancy problem the allows the control of a joint alone or in combination with other joints to produce any desired limb configuration and movement trajectory. For each motor behavior, the nervous system uses a strategy which minimizes the number of changeable control variables and keep sthe parameters of these changes invariant. This is illustrated by examples of simulated kinematic and electromyographic signals from single- and multi-joint arm movements produced by patterns of control variables. Empirical support is provided and additional tests are suggested. The model is contrasted with others based on the ideas of programming of motoneuronal activity, muscle forces, stiffness or movement kinematics.

Long Abstract:

A hypothesis about sensorimotor integration (the lambda model) is described and applied to movement control and kinesthesia. The nervous system organizes positional frames of reference for the sensorimotor apparatus and produces active movements by shifting frames in terms of spatial coordinates. Kinematic and electromyographic patterns are not programmed but emerge from the dynamic interaction of the system's components, including external forces, within the designated frame of reference. Motoneuronal threshold properties and proprioceptive inputs to motoneurons may be important components in the physiological mechanism which produces positional frames of reference. The hypothesis that intentional movements are produced by shifting the frame of reference is extended to multi-muscle and multi-degrees of freedom systems by providing a solution for the redundancy problem the allows the control of a joint alone or in combination with other joints to produce any desired limb configuration and movement trajectory. For each motor behavior, the nervous system uses a strategy which minimizes the number of changeable control variables and keep sthe parameters of these changes invariant. This is illustrated by examples of simulated kinematic and electromyographic signals from single- and multi-joint arm movements produced by patterns of control variables. Empirical support is provided and additional tests are suggested. The model is contrasted with others based on the ideas of programming of motoneuronal activity, muscle forces, stiffness or movement kinematics.

Keywords:	motor control, frames of reference, motoneurons, control variables, proprioception, kinaesthesis, equilibrium points, multi-muscle systems, pointing, synergy, redundancy problem.
Subjects:	Neuroscience: Neuroanatomy Neuroscience: Neural Modelling Neuroscience: Motor Function Neuroscience: Neurophysiology
ID code:	bbs00000560
Deposited by:	John M Findlay on 02 May 2001