MPI CyberMotion Simulator: Implementation of a Novel Motion Simulator to Investigate Multisensory Path Integration in Three Dimensions

Abstract

Path integration is a process in which self-motion is integrated over time to obtain an estimate of one's current position relative to a starting point . However, with multiple cues present, inertial cues -particularly kinaesthetic -seem to dominate [6][7] . In the absence of vision, humans tend to overestimate short distances (<5 m) and turning angles (<30°), but underestimate longer ones 5 . Movement through physical space therefore does not seem to be accurately represented by the brain.Extensive work has been done on evaluating path integration in the horizontal plane, but little is known about vertical movement (see 3 for virtual movement from vision alone). One reason for this is that traditional motion simulators have a small range of motion restricted mainly to the horizontal plane. Here we take advantage of a motion simulator [8][9] with a large range of motion to assess whether path integration is similar between horizontal and vertical planes. The relative contributions of inertial and visual cues for path navigation were also assessed.16 observers sat upright in a seat mounted to the flange of a modified KUKA anthropomorphic robot arm. Sensory information was manipulated by providing visual (optic flow, limited lifetime star field), vestibular-kinaesthetic (passive self motion with eyes closed), or visual and vestibularkinaesthetic motion cues. Movement trajectories in the horizontal, sagittal and frontal planes consisted of two segment lengths (1st: 0.4 m, 2nd: 1 m; ±0.24 m/s 2 peak acceleration). The angle of the two segments was either 45° or 90°. Observers pointed back to their origin by moving an arrow that was superimposed on an avatar presented on the screen.Observers were more likely to underestimate angle size for movement in the horizontal plane compared to the vertical planes. In the frontal plane observers were more likely to overestimate angle size while there was no such bias in the sagittal plane. Finally, observers responded slower when answering based on vestibular-kinaesthetic information alone. Human path integration based on vestibular-kinaesthetic information alone thus takes longer than when visual information is present. That pointing is consistent with underestimating and overestimating the angle one has moved through in the horizontal and vertical planes respectively, suggests that the neural representation of self-motion through space is nonsymmetrical which may relate to the fact that humans experience movement mostly within the horizontal plane.

Sound-evoked vestibular stimulation affects the anticipation of gravity effects during visual self-motion

“…Thus, heading direction is monitored more robustly by integrating vestibular and visual signals, even when in conflict (Fetsch et al 2009;Butler et al 2015). Previous studies found differences in the representation of downward versus horizontal self-motion (Barnett-Cowan et al 2012;Nesti et al 2014). Moreover, functional magnetic resonance imaging (fMRI) showed that vertical visual self-motion activates a cerebral network including the parieto-insular vestibular cortex (PIVC), inferior parietal cortex, intraparietal sulcus, and cerebellar vermis (Indovina et al 2013b), a network known to process both visual and vestibular signals in humans (Indovina et al 2005;Lopez and Blanke 2011).…”

The Importance of Stimulus Noise Analysis for Self-Motion Studies

“…The study was conducted using the Max Planck Institute CyberMotion Simulator, a 6degrees-of-freedom anthropomorphic robot-arm, able to provide a large variety of motion stimuli, with a maximal vertical displacement of about 1.4 m and a maximal vertical linear acceleration of about 5 m/s 2 (for technical details refer to Robocoaster, KUKA Roboter GmbH, Germany; [19], [20]). IMU traces were acquired for 10 reference stimuli (1 Hz sinusoidal acceleration profiles with peak amplitudes of 0.07, 0.3, 1.1, 1.6 and 2 m/s 2 , both upward and downward) with a 3D accelerometer (YEI 3-Space Sensor, 500 Hz) attached rigidly on the back of the simulator seat.…”

Navigating in a Three-Dimensional World

“…We suggest that our understanding of three-dimensional navigation in humans can be improved using advanced motion simulatorssuch as our Max Planck Institute CyberMotion Simulator, which is capable of moving human observers through complex motion paths in a volume of space. (An open access video is found in the original article: Barnett-Cowan et al 2012. ) Future experiments with fewer constraints, including trajectories using additional degrees of freedom, longer paths, multiple planes, and with the body differently orientated relative to gravity, will be able to more fully assess the quasi-planar representation of space proposed by Jeffery et al, as well as how vertical movement may be encoded differently.…”