Fast on-line adaptation may cause critical noise amplification in human control behaviour
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1
University of Bremen, Institute of Theoretical Neurophysics, Germany
When humans perform closed-loop control tasks like in upright standing or while balancing a stick, their behaviour exhibits non-Gaussian fluctuations with long-tailed distributions [1, 2]. The origin of these fluctuations is not known, but their statistics suggests a fine-tuning of the underlying system to a critical point [3]. We investigated whether self-tuning may be caused by the annihilation of local predictive information due to success of control [4]. We found that this mechanism can lead to critical noise amplification, a fundamental principle which produces complex dynamics even in very low-dimensional state estimation tasks. It generally emerges when an unstable dynamical system becomes stabilised by an adaptive controller that has a finite memory [5]. It is also compatible with control based on optimal recursive Bayesian estimation of a varying hidden parameter.
Starting from this theory, we developed a realistic model of adaptive closed-loop control by including constraints on memory and delays. To test this model, we performed psychophysical experiments where humans balanced an unstable target on a computer screen. It turned out, that the model reproduces the long tails of the distributions together with other characteristics of the human control dynamics. Fine-tuning the model to match the experimental dynamics identifies parameters characterising a subjects control system which can be independently tested. Our results suggest, that the nervous system involved in closed-loop motor control nearly optimally estimates system parameters on-line from very short epochs of past observations. Ongoing experimental investigation of the models predictions promises detailed insights into control strategies employed by the human brain.
Conference:
Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009.
Presentation Type:
Poster Presentation
Topic:
Decision, control and reward
Citation:
Patzelt
F and
Pawelzik
KR
(2009). Fast on-line adaptation may cause critical noise amplification in human control behaviour.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference on Computational Neuroscience.
doi: 10.3389/conf.neuro.10.2009.14.034
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Received:
26 Aug 2009;
Published Online:
26 Aug 2009.
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Correspondence:
Felix Patzelt, University of Bremen, Institute of Theoretical Neurophysics, Bremen, Germany, felix@neuro.uni-bremen.de