Alessandro Nesti

Alumni of the Department Human Perception, Cognition & Action
Alumni of the Group Motion Perception & Simulation

Main Focus

Research Scientist

I am a Postdoc with background in biomedical engineering and neuroscience. I currently work in the and in the research groups, and I contributed to the project . My research interest is in in everyday life and in using this knowledge to investigate and optimize techniques to perceptually expand the limited physical workspace of dynamic vehicles simulators ().

In my research I employ the motion simulators to provide wide motion ranges and an immersive virtual environment, and I use psychophysical procedures and active behavioral tasks to measure human performances both objectively (e.g. errors, delays, control signals) and subjectively (e.g. verbal reports, forced-choice decision tasks).

Since January 2017, I work from the Campus Biotech in Geneva on a collaborative project with the Laboratory of Cognitive Neuroscience, led by Professor Blanke at EPFL. The goal is to investigate the contribution of visual and vestibular signals to bodily self-consciousness.

Selected publications
  • Human discrimination of head-centred visual–inertial yaw rotations Experimental Brain Research (2015)
  • Roll rate perceptual thresholds in active and passive curve driving simulation Simulation: Transactions of the Society for Modeling and Simulation International (2016)
  • Accumulation of Inertial Sensory Information in the Perception of Whole Body Yaw Rotation PLoS One (2017)

1. HUMAN DISCRIMINATION OF SELF-MOTION

To successfully perform daily activities such as maintaining posture or running, humans need to be sensitive to self-motion over a large range of motion intensities. How the intensity of the motion stimuli affects self-motion perception is an open, yet important, question. We conducted an experimental campaign to investigate how the human ability to discriminate self-motion depends on motion intensity for upward and downward translations in darkness and for horizontal head-centred rotations in presence of visual-only, inertial-only and visual-inertial motion stimuli. We found that differential thresholds, i.e. the smallest detectable change in stimulus intensity, increase with stimulus intensity following a trend well-described by a power function [1,2]. Moreover, combining visual and inertial stimuli does not lead to improved self-motion sensitivity over the investigated range of yaw rotations. We further observed that the time necessary for a visual-only stimulus to evoke a compelling self-motion illusion is independent from stimulus intensity and facilitated by recent exposure [2].


Figure: Differential thresholds for head centered yaw rotations.

2. VARIABLE ROLL-RATE PERCEPTION IN DRIVING SIMULATION

Figure: Inside of the cabin of the MPI CyberMotion Simulator. In a driving experiment, the driver steers a virtual car through a curve using a forcefeedback steering wheel.


In driving simulation, simulator tilt is used to reproduce linear acceleration. In order to feel realistic, this tilt is performed at a rate below the tilt-rate detection threshold, which is usually assumed constant. However, it is known that many factors affect the threshold, like visual information, simulator motion in additional directions, or active vehicle control. We investigated the effect of these factors on roll-rate detection threshold during simulated curve driving [3]. Results showed that roll-rate perception in vehicle simulation is affected by the presence of motion in additional directions. Moreover, an active control task seems to increase the detection threshold, i.e. impair motion sensitivity, but with large individual differences. We hypothesize that this is related to the level of immersion during the task.


3. WABS: PERCEPTION-BASED MOTION SIMULATION


Within the project WABS ("Wahrnehmungsbasierte Bewegungssimulation") we developed an alternative approach to motion cueing. Motion cueing is the process of converting a desired physical motion (e.g. from a vehicle model) into commands that are sent to the motion simulator. This conversion is done by a so-called Motion Cueing Algorithm (MCA).The WABS project is based on the idea that motion cueing can be improved by including novel insights in human self-motion perception, obtained from fundamental motion perception studies, in the MCAs. This "perception-based motion cueing" approach allows for exploiting the limitations and ambiguities of the human perceptual system.

More about

4. SETUP OF THE MOTION-LAB

To expand our simulator fleet, we acquired and installed a new motion simulator consisting of a hexapod motion system. I supported the acquisition process and developed the software interface, including the experimental framework that was used for several research projects (from September 2015 onwards).

Figure: Artistic representation of the graphical user interface (GUI), the software and the motion simulator

5. ACCUMULATION OF SENSORY EVIDENCE IN SELF-MOTION PERCEPTION

While moving through the environment, our central nervous system accumulates sensory information over time to provide an estimate of our self-motion, allowing for completing crucial tasks such as maintaining balance. However, little is known on how the duration of the motion stimuli influences our performances in a self-motion discrimination task. We studied the human ability to discriminate intensities of sinusoidal (0.5 Hz) self-rotations around the vertical axis (yaw) for four different stimulus durations (1, 2, 3 and 5 s) in darkness. We found that discrimination performances increase with stimulus duration [4], suggesting that the central nervous system accumulates sensory information on self-motion over time. Observed trends in differential thresholds are consistent with predictions based on a drift diffusion model with leaky integration of sensory evidence.

Figure: Experimentally measured DTs (red circles) are well described by a DDM that includes a leaky integration term (blue line).

6. PSYCHOPHYSICAL FUNCTIONS FOR SELF-MOTION PERCEPTION [ongoing project]

The fundamental research question of how physical and perceived stimuli are related to each other fascinates neuroscientists since the seminal works of Weber and, later on, of Fechner and Stevens. In the research field of self-motion perception, important steps towards this goal have been recently achieved through a series of studies that quantified the human ability to discriminate self-movements for a wide range of motion intensities [1], [2]. However, this does not yet allow to univocally define the “psychophysical function” relating physical and perceived motion intensity, since changes in discrimination performances can be due to nonlinearities and/or to stimulus-dependent noisein the perceptual process. In this project we combine a “Magnitude Estimation” (ME) task and a “Magnitude Discrimination” (MD) task to gain insight into both the shape and the noise of the psychophysical function. In the ME task, 10 participants experience several 1s long linear translations of different intensities (0 – 2 m/s2) and assign them a numerical estimate that reflects the intensity of the evoked motion sensation. In the MD task, the smallest detectable change between two lateral translations of different intensity (Differential Threshold, DT) will be measured for 10 participants. Preliminary analyses show that both magnitude estimates and DTs increase with motion intensity, and that measured DTs are overall smaller than predictions based on magnitude estimates alone.


References

[1] A. Nesti, K. A. Beykirch, P. Pretto, and H. H. Bülthoff, “Human discrimination of head-centred visual–inertial yaw rotations,” Exp. Brain Res., vol. 233, no. 12, pp. 3553–3564, 2015.

[2] A. Nesti, K. A. Beykirch, P. Pretto, and H. H. Bülthoff, “Self-motion sensitivity to visual yaw rotations in humans,” Exp. Brain Res., vol. 233, no. 3, pp. 861–899, 2015.

[3] A. Nesti, S. Nooij, M. Losert, H. H. Bu lthoff, and P. Pretto, “Roll rate perceptual thresholds in active and passive curve driving simulation,” Simul. Trans. Soc. Model. Simul. Int., vol. 92, no. 5, pp. 417–426, 2016.

[4] A. Nesti, K. De Winkel, and H. H. Bülthoff, “Accumulation of Inertial Sensory Information in the Perception of Whole Body Yaw Rotation,” PLoS One, vol. 12, no. 1, 2017.

Curriculum Vitae

Education

  • 02/2011 - 04/2015: PhD in Neuroscience at the "Max Planck Institute for Biological Cybernetics" - Spemannstrase 41 - 72076 Tübingen, Germany
  • 10/2003 - 04/2010: Master’s degree in biomedical engineering at "Università degli Studi di Pavia" - Via Ferrata, 1 - 27100 Pavia - Italy
  • 07/2003: European Baccalaureat at the "European School of Varese" - Italy

Professional experience

  • 02/2011 - now: Doctoral and post-doctoral research activity on the human perception of self-motion at Max Planck Institute for Biological Cybernetics with Professor , Spemannstrasse 38 – 72076 Tübingen, Germany
  • 11/2011 - 11/2013: Technical support and research activity within a VIP project on perception-based motion simulation at Max Planck Institute for Biological Cybernetics with Professor , Spemannstrasse 38 – 72076 Tübingen, Germany
  • 10/2009 - 04/2010: Development of Hardware and Software for the diagnosis of the Ocular Tilt Reaction syndrome at Bioengeneering Laboratory with Professor - Via Ferrata 1 - 27100 Pavia
  • 09/2006 - 07/2007: Development of Hardware and Software for rehabilitation of vestibular disorders at Bioengeneering Laboratory with Professor - Via Ferrata 1 - 27100 Pavia
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