title: The importance of stimulus noise analysis for self-motion studies.
abstract: Motion simulators are widely employed in basic and applied research to study the neural mechanisms of perception and action during inertial stimulation. In these studies, uncontrolled simulator-introduced noise inevitably leads to a disparity between the reproduced motion and the trajectories meticulously designed by the experimenter, possibly resulting in undesired motion cues to the investigated system. Understanding actual simulator responses to different motion commands is therefore a crucial yet often underestimated step towards the interpretation of experimental results. In this work, we developed analysis methods based on signal processing techniques to quantify the noise in the actual motion, and its deterministic and stochastic components. Our methods allow comparisons between commanded and actual motion as well as between different actual motion profiles. A specific practical example from one of our studies is used to illustrate the methodologies and their relevance, but this does not detract from its general applicability. Analyses of the simulator's inertial recordings show direction-dependent noise and nonlinearity related to the command amplitude. The Signal-to-Noise Ratio is one order of magnitude higher for the larger motion amplitudes we tested, compared to the smaller motion amplitudes. Simulator-introduced noise is found to be primarily of deterministic nature, particularly for the stronger motion intensities. The effect of simulator noise on quantification of animal/human motion sensitivity is discussed. We conclude that accurate recording and characterization of executed simulator motion are a crucial prerequisite for the investigation of uncertainty in self-motion perception.
authors.affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Nesti
authors.affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Karl A
authors.initials: KA
authors.lastname: Beykirch
authors.affiliation: German Center for Vertigo and Balance Disorders, Ludwig Maximilians University Hospital of Munich, Munich, Germany.
authors.forename: Paul R
authors.initials: PR
authors.lastname: MacNeilage
authors.affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Barnett-Cowan
authors.affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Tübingen, Germany; Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea.
authors.forename: Heinrich H
authors.initials: HH
authors.lastname: Bülthoff
mesh_terms: D004777:Environment; D006801:Humans; D009038:Motion; D009039:Motion Perception; D010812:Physical Stimulation; D059629:Signal-To-Noise Ratio; D013223:Statistics as Topic; D013269:Stochastic Processes
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