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Abstract

The BUMP model of response planning: Intermittent predictive control accounts for 10 Hz physiological tremor

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Abstract

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  1. The BUMP model of response planning: Intermittent predictive control accounts for 10 Hz physiological tremor Robin T. Bye* and Peter D. NeilsonNeuroengineering Laboratory, School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney 2052, Australia.*Corresponding author: robin.bye@gmail.com

  2. The BUMP model of response planning forms the kernel of Adaptive Model Theory which defines, in computational terms, a basic unit of motor production or BUMP. Each BUMP consists of three processes: (1) analysing sensory information, (2) planning a desired optimal response, and (3) execution of that response. These processes operate in parallel across successive sequential BUMPs. The response planning process requires a discrete time interval in which to generate a minimum acceleration trajectory to connect the actual response with the predicted future state of the target and compensate for executional error. Here we show, by means of a simulation study of constant velocity (ram p) movements, that employing a 100 ms planning interval closely reproduces the measurement discontinuities and power spectra of electromyograms, joint-angles, and angular velocities of 10 Hz physiological tremor reported experimentally. We conclude that intermittent predictive control through sequential operation of BUMPs is a fundamental mechanism of 10 Hz physiological tremor in movement. Abstract

  3. Physiological tremor Normal 8-12 Hz tremor due to central-neurogenic and mechanical-reflex components Many types, e.g. rest, posture, motion Tremor during movement (focus of this study) is ~10 Hz and of central origin 10 Hz physiological tremor during constant velocity (ramp) movements is observable in joint angle, angular velocity and EMG signals [1] Cerebello-thalamo-cortical loop is considered neural basis for intermittent motor control of continuous movement [2]

  4. Adaptive Model Theory The BUMP model forms the kernel of Adaptive Model Theory, a neuroengineering account of movement control Fusion of adaptive control theory and neuroscience Addresses major human movement science issues - e.g., intermittency, redundancy, resources, nonlinear interactions [3] Three systems for information processing Biologically-feasible neural network solution

  5. Three processing systems Response planning (RP) Response execution (RE) system Sensory analysis (SA) system Operate independently and in parallel: The CNS can simultaneously - plan appropriate response to a stimulus(RP system) - execute response to an earlier stimulus (RE system) - detect and store a subsequent stimulus (SA system)

  6. Intermittency SA and RE systems operate continuously RP system operates intermittently - system is refractory while operating on “chunks” of information fixed planning time interval to plan an optimal response trajectory (minimum acceleration) must predict future state of target and response - planning time interval Tp = 100 ms Leads to repeating SA-RP-RE sequences: BUMPs Movement consists of concatenated submovements Each submovement has a fixed duration of 100 ms

  7. SA-RP-RE sequence SA RP BUMP RE

  8. Basic unit of motor production (BUMP)

  9. Simulation study Simulator of BUMP model implemented with Matlab/Simulink software Aim: Test simulator’s ability to reproduce results from human experiments Test case: Influential study of physiological tremor in slow finger movements [1] Simulations of ramp and hold movements with and without visual feedback with various levels of skill of a variety of movement speeds Compare real (human) and simulated data angular position, velocity, acceleration power spectra

  10. Ramp movements (real)

  11. Ramp movements (sim.)

  12. Power spectra (real & sim.) Real Simulated

  13. Varying speeds (real)

  14. Varying speeds (sim.)

  15. Effect of vision (real & sim.) Real Simulated

  16. Discussion Simulator closely reproduces the results of [1], i.e. ramp movements (position, velocity, acceleration waveforms) and their power spectra - with and without visual feedback - for high and low level of skill - for a variety of movement speeds Main finding: 10 Hz physiological tremor occurs for all test cases independent of vision, skill, and movement speed

  17. Discussion cont’d With vision secondary 2-3 Hz component occurs for less skilled subjects - “bumpy” movement trajectory Without vision power of 2-3 Hz component is halved or disappears smooth movement trajectory Results are independent of movement speed An adaptation paradigm was used to simulate different levels of skill

  18. Conclusion We suggest that 10 Hz physiological tremor is the direct result of an intermittently operating predictive neural controller generating BUMPs every 100 ms. References Vallbo ÅB & Wessberg J (1993). Organization of motor output in slow finger movements in man. Journal of Physiology, 469, 673-691. Gross J, Timmermann L, Kujala J, Dirks M, Schmitz F, Salmelin R & Schnitzler A (2002). The neural basis of intermittent motor control in humans. Proceedings of the National Academy of Sciences of the USA,99(4), 2299-2302. Neilson PD & Neilson MD (2005). An overview of adaptive model theory: Solving the problems of redundancy, resources, and nonlinear interactions in human movement control. Journal of Neural Engineering, 2(3):S279–S312.

  19. Use this as a master First level - Second level

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