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Dive into the research topics where Alessandro Nesti is active.

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Featured researches published by Alessandro Nesti.


PLOS ONE | 2014

The importance of stimulus noise analysis for self-motion studies

Alessandro Nesti; K Beykirch; Paul R. MacNeilage; Michael Barnett-Cowan; Hh Bülthoff

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.


Simulation | 2016

Roll rate perceptual thresholds in active and passive curve driving simulation

Alessandro Nesti; Suzanne A. E. Nooij; Martin Losert; Hh Bülthoff; P Pretto

In driving simulation, simulator tilt is used to reproduce sustained linear acceleration. In order to feel realistic, this tilt is performed at a rate below the human tilt rate detection threshold, which is usually assumed constant. However, it is known that many factors affect the threshold, such as visual information, simulator motion in additional directions, or the driver’s active effort required for controlling the vehicle. Here we investigated the effect of these factors on the roll rate detection threshold during simulated curve driving. Ten participants reported whether they detected roll motion in multiple trials during simulated curve driving, while roll rate was varied over trials. Roll rate detection thresholds were measured under four conditions. In the first three conditions, participants were moved passively through a curve with the following: (i) roll only in darkness; (ii) combined roll/sway in darkness; (iii) combined roll/sway and visual information. In the fourth (iv) condition participants actively drove through the curve. The results showed that roll rate thresholds in simulated curve driving increase, that is, sensitivity decreases, when the roll tilt is combined with sway motion. Moreover, an active control task seemed to further increase the detection threshold, that is, impair motion sensitivity, but with large individual differences. We hypothesize that this is related to the level of immersion during the task.


PLOS ONE | 2017

Accumulation of Inertial Sensory Information in the Perception of Whole Body Yaw Rotation.

Alessandro Nesti; Kn de Winkel; Hh Bülthoff

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. Here we study 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. In a typical trial, participants experienced two consecutive rotations of equal duration and different peak amplitude, and reported the one perceived as stronger. For each stimulus duration, we determined the smallest detectable change in stimulus intensity (differential threshold) for a reference velocity of 15 deg/s. Results indicate that differential thresholds decrease with stimulus duration and asymptotically converge to a constant, positive value. This suggests that the central nervous system accumulates sensory information on self-motion over time, resulting in improved discrimination performances. Observed trends in differential thresholds are consistent with predictions based on a drift diffusion model with leaky integration of sensory evidence.


Annals of the New York Academy of Sciences | 2011

A new device to assess static ocular torsion.

Stefano Ramat; Alessandro Nesti; Maurizio Versino; Silvia Colnaghi; Catia Magnaghi; Alessandro Bianchi; Giorgio Beltrami

In clinical settings, static ocular torsion is assessed by taking a fundus photograph and measuring the angle between a horizontal line and the line connecting the fovea to the head of the optic nerve (centro‐cecal axis rotation; CCAR). We developed and tested a system specifically aimed at CCAR measurements, based on low‐cost commercial hardware, and that implements an adaptive research algorithm that selects and presents bright dots on a monitor to outline the borders of the blind spot, locate its center, and measure CCAR. We examined 10 healthy subjects who underwent four CCAR measurements to evaluate the reliability of the system and compared our results with those of fundus photographic examination. Our data showed an excyclophoria, with mean ocular torsion of 6.4° in the right and 6.7° in the left eye. These values are in keeping with those in the literature. Moreover, the values of the intraclass correlation coefficients suggest excellent reliability of the technique.


Experimental Brain Research | 2016

Perception of rotation, path, and heading in circular trajectories

Suzanne A. E. Nooij; Alessandro Nesti; Hh Bülthoff; P Pretto

When in darkness, humans can perceive the direction and magnitude of rotations and of linear translations in the horizontal plane. The current paper addresses the integrated perception of combined translational and rotational motion, as it occurs when moving along a curved trajectory. We questioned whether the perceived motion through the environment follows the predictions of a self-motion perception model (e.g., Merfeld et al. in J Vestib Res 3:141–161, 1993; Newman in A multisensory observer model for human spatial orientation perception, 2009), which assume linear addition of rotational and translational components. For curved motion in darkness, such models predict a non-veridical motion percept, consisting of an underestimation of the perceived rotation, a distortion of the perceived travelled path, and a bias in the perceived heading (i.e., the perceived instantaneous direction of motion with respect to the body). These model predictions were evaluated in two experiments. In Experiment 1, seven participants were moved along a circular trajectory in darkness while facing the motion direction. They indicated perceived yaw rotation using an online tracking task, and perceived travelled path by drawings. In Experiment 2, the heading was systematically varied, and six participants indicated, in a 2-alternative forced-choice task, whether they perceived facing inward or outward of the circular path. Overall, we found no evidence for the heading bias predicted by the model. This suggests that the sum of the perceived rotational and translational components alone cannot adequately explain the overall perceived motion through the environment. Possibly, knowledge about motion dynamics and familiar stimuli combinations may play an important additional role in shaping the percept.


Archive | 2015

Perception-Based Motion Cueing: A Cybernetics Approach to Motion Simulation

P Pretto; Joost Venrooij; Alessandro Nesti; Hh Bülthoff

The goal of vehicle motion simulation is the realistic reproduction of the perception a human observer would have inside the moving vehicle by providing realistic motion cues inside a motion simulator. Motion cueing algorithms play a central role in this process by converting the desired vehicle motion into simulator input commands with maximal perceptual fidelity, while remaining within the limited workspace of the motion simulator. By understanding how the one’s own body motion through the environment is transduced into neural information by the visual, vestibular and somatosensory systems and how this information is processed in order to create a whole percept of self-motion we can qualify the perceptual fidelity of the simulation. In this chapter, we address how a deep understanding of the functional principles underlying self-motion perception can be exploited to develop new motion cueing algorithms and, in turn, how motion simulation can increase our understanding of the brain’s perceptual processes. We propose a perception-based motion cueing algorithm that relies on knowledge about human self-motion perception and uses it to calculate the vehicle motion percept, i.e. how the motion of a vehicle is perceived by a human observer. The calculation is possible through the use of a self-motion perception model, which simulate the brain’s motion perception processes. The goal of the perception-based algorithm is then to reproduce the simulator motion that minimizes the difference between the vehicle’s desired percept and the actual simulator percept, i.e. the “perceptual error”. Finally, we describe the first experimental validation of the new motion cueing algorithm and shown that an improvement in the current standards of motion cueing is possible.


automotive user interfaces and interactive vehicular applications | 2018

The Effect of Road Bumps on Touch Interaction in Cars

Sven Mayer; Huy Viet Le; Alessandro Nesti; Niels Henze; Hh Bülthoff; Lewis L. Chuang

Touchscreens are a common fixture in current vehicles. With autonomous driving, we can expect touch interaction with such in-vehicle media systems to exponentially increase. In spite of vehicle suspension systems, road perturbations will continue to exert forces that can render in-vehicle touch interaction challenging. Using a motion simulator, we investigate how different vehicle speeds interact with road features (i.e., speed bumps) to influence touch interaction. We determine their effect on pointing accuracy and task completion time. We show that road bumps have a significant effect on touch input and can decrease accuracy by 19%. In light of this, we developed a Random Forest (RF) model that improves touch accuracy by 32.0% on our test set and by 22.5% on our validation set. As the lightweight model uses only features that can easily be determined through inertial measurement units, this model could be easily deployed in current automobiles.


Neuroscience Letters | 2017

Neural correlates of decision making on whole body yaw rotation: an fNIRS study

Kn de Winkel; Alessandro Nesti; Hasan Ayaz; Hh Bülthoff

Prominent accounts of decision making state that decisions are made on the basis of an accumulation of sensory evidence, orchestrated by networks of prefrontal and parietal neural populations. Here we assess whether these findings generalize to decisions on self-motion. Participants were presented with whole body yaw rotations of different durations in a 2-Interval-Forced-Choice paradigm, and tasked to discriminate motions on the basis of their amplitude. The cortical hemodynamic response was recorded using functional near-infrared spectroscopy (fNIRS) while participants were performing the task. The imaging data was used to predict the specific response on individual experimental trials, and to predict whether the comparison stimulus would be judged larger than the reference. Classifier performance on the former variable was negligible. However, considerable performance was achieved for the latter variable, specifically using parietal imaging data. The findings provide support for the notion that activity in the parietal cortex reflects modality independent decision variables that represent the strength of the neural evidence in favor of a decision. The results are encouraging for the use of fNIRS as a method to perform neuroimaging in moving individuals.


Seeing and Perceiving | 2012

Roll rate thresholds in driving simulation

Alessandro Nesti; Michael Barnett-Cowan; Hh Bülthoff; P Pretto

The restricted operational space of dynamic driving simulators requires the implementation of motion cueing algorithms that tilt the simulator cabin to reproduce sustained accelerations. In order to avoid conflicting inertial cues, the tilt rate is limited below drivers’ perceptual thresholds, which are typically derived from the results of classical vestibular research, where additional sensory cues to self-motion are removed. These limits might be too conservative for an ecological driving simulation, which provides a variety of complex visual and vestibular cues as well as demands of attention which vary with task difficulty. We measured roll rate detection threshold in active driving simulation, where visual and vestibular stimuli are provided as well as increased cognitive load from the driving task. Here thresholds during active driving are compared with tilt rate detection thresholds found in the literature (passive thresholds) to assess the effect of the driving task. In a second experiment, these thresholds (active versus passive) are related to driving preferences in a slalom driving course in order to determine which roll rate values are most appropriate for driving simulators so as to present the most realistic driving experience. The results show that detection threshold for roll in an active driving task is significantly higher than the limits currently used in motion cueing algorithms, suggesting that higher tilt limits can be successfully implemented to better optimize simulator operational space. Supra-threshold roll rates in the slalom task are also rated as more realistic. Overall, our findings indicate that increasing task complexity in driving simulation can decrease motion sensitivity allowing for further expansion of the virtual workspace environment.


Experimental Brain Research | 2014

Human sensitivity to vertical self-motion

Alessandro Nesti; Michael Barnett-Cowan; Paul R. MacNeilage; Hh Bülthoff

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