Jean-Louis Vercher

Jean-Louis Vercher
French National Centre for Scientific Research | CNRS · Institute of Movement Sciences

PhD

About

196
Publications
30,938
Reads
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3,991
Citations
Introduction
I got my PhD at the Aix-Marseille University (France). From 1984 to 1987 I was with the French Ministry of Defense. In 1985 and 1986, I was a visiting scientist (post-doc) at the department of Physiology of Oxford University (UK). In 1987 I joined the CNRS as assistant researcher, and got my Habilitation for Research Direction in 1999. Since 2000 I am Research Director. The main topic of my research relates to the study of sensori-motor systems control, coordination and plasticity.
Additional affiliations
January 1996 - December 2011
French National Centre for Scientific Research
Position
  • Centre national de la recherche scientifique
January 1990 - December 1997
Aix-Marseille Université

Publications

Publications (196)
Article
Full-text available
When taking off from a sloping surface, flies have to reorient themselves dorsoventrally and stabilize their body by actively controlling their flapping wings. We have observed that the righting is achieved solely by performing a rolling manoeuvre. How flies manage to do this has not yet been elucidated. It was observed here for the first time that...
Article
Full-text available
Viewing a scene on a screen display differs greatly from viewing it in the real world. The visual information is conveyed via a flat screen at a fixed distance, and this screen distance can influence how viewers perceive depth in stereograms in conventional stereoscopic displays. This study investigated whether screen distance influences perceived...
Article
Full-text available
We investigated the impact of automated driving phases of different durations (long vs. short) on takeover performance and driver state. Thirty participants drove on a dynamic simulator under autonomous mode for three successive periods of automated driving: a short (10 min), a long (1 hour) and another short (10 min) period, each ending with a tak...
Article
Full-text available
The human nervous system displays such plasticity that we can adapt our motor behavior to various changes in environmental or body properties. However, how sensorimotor adaptation generalizes to new situations and new effectors, and which factors influence the underlying mechanisms, remains unclear. Here we tested the general hypothesis that differ...
Conference Paper
Full-text available
With advanced technology on new automation functions, driverless cars are going to be very popular in a near future. As a consequence, drivers' role is about to change: drivers will not drive anymore but will be driven, allowing them to focus on other activities such as playing games or watching a video without worrying about road events. Our resea...
Article
Full-text available
Monitoring car drivers for drowsiness is crucial but challenging. The high inter-individual variability observed in measurements raises questions about the accuracy of the drowsiness detection process. In this study, we sought to enhance the performance of machine learning models (Artificial Neural Networks: ANNs) by training a model with a group o...
Poster
Full-text available
In the near future, autonomous cars will allow drivers to focus on more enjoyable activities such as reading or watching videos instead of driving. However, spending more time with gaze-off the road leads drivers to lose situational awareness and fall into an "out of loop" state, posing a risk on safety in the event of takeover (Endsley, 1995). Her...
Conference Paper
Full-text available
We investigated drivers' gaze behavior during takeover after short (10 min) and long (1 hour) durations spent on Level 3 automation. Eight participants drove on a dynamic simulator in autonomous mode on a highway loop. They were required to watch a movie on the instrument cluster behind the steering wheel before the request to intervene. Gaze data...
Article
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The stabilization of plummeting hoverflies was filmed and analysed in terms of their wingbeat initiation times as well as the crash and stabilization rates. The flies experienced near-weightlessness for a period of time that depended on their ability to counteract the free fall by triggering their wing-beats. In this paradigm, hoverflies’ flight st...
Article
Full-text available
Findings from virtual reality applications in general and driving or flight simulators in particular, are frequently generalized to the study of human behavior. Thus, it is crucial to ensure that the virtuality of the experimental setup has little or no effect on perception of space and motion. Most studies show that observers immersed in virtual e...
Article
Full-text available
To avoid crashing onto the floor, a free falling fly needs to trigger its wingbeats quickly and control the orientation of its thrust accurately and swiftly to stabilize its pitch and hence its speed. Behavioural data have suggested that the vertical optic flow produced by the fall and crossing the visual field plays a key role in this anti-crash r...
Data
Schematic representation of the simulations. In the simulations, the procedure was assumed to take place in an infinite corridor with textured walls. Numerically simulated hoverflies headed toward the corridor and their attitude varied only on the pitch degree-of-freedom. Since both yaw and roll are locked, they followed a straight line along the c...
Data
1—At the beginning of the film the head of the flies is dotted on each image from the two point of views. 2—Three points are automatically tracked on each image of the flies: Head, thanks to the dot determined on the first image. Body, which is the centroid of the pixels’ mass. And tail, at the opposite extremity of the head. This step is repeated...
Data
Procedure used to quantify the errors in the pitch orientation estimates. (A) Five 13mm long dummy hoverflies were printed in 3-D with a given orientation of their body in regard to their holding rod (ranging from 0° to 60°). They were suspended from a horizontal bar with two different yaw orientations, namely 0° and 90° and placed in 6 different p...
Data
Estimation of the model’s parameters. (A) Likelihood map averaged from the 44 parameters estimations. The histogram on the x- and y-axis give the distribution of the parameters selected with MLE procedure during individual estimations. (B) Pitch data before wingbeat initiation and step response of the transfer function Tpassive(s) modeling the dyna...
Data
Measurement of the pitch orientation estimation errors. (A) Bar histogram of the whole angular error in the case of the 6 positions in the experimental box and the two imposed yaw orientation of the 5 dummies (S4A Fig) shown in blue bars. Probability density function estimated with a t-location scale distribution in the case of the whole data (red...
Data
Summary of the model parameters. (XLSX)
Research
Full-text available
A classical visuo-manual adaptation protocol carried out on a rotating platform was used to test the ability of subjects to adapt to centrifugal and Coriolis forces when visual feedback of the arm is manipulated. Three main results emerge: (a) an early modi®cation of the initial trajectory of the movements takes place even without visual feedback o...
Research
Full-text available
The present study tested whether vestibular input can be processed on-line to control goal-directed arm movements towards memorized visual targets when the whole body is passively rotated during movement execution. Subjects succeeded in compensating for current body rotation by regulating ongoing arm movements.This performance was compared to the a...
Research
Full-text available
Using galvanic vestibular stimulation (GVS), we tested whether a change in vestibular input at the onset of goal-directed arm movements induces deviations in arm trajectory. Eight head-fixed standing subjects were instructed to reach for memorized visual targets in complete darkness. In half of the trials, randomly-selected, a 3 mA bipolar binaural...
Article
Full-text available
Not just detecting but also predicting impairment of a car driver's operational state is a challenge. This study aims to determine whether the standard sources of information used to detect drowsiness can also be used to predict when a given drowsiness level will be reached. Moreover, we explore whether adding data such as driving time and particip...
Article
Full-text available
Understanding the impact of weightlessness on human behavior during the forthcoming long-term space missions is of critical importance, especially when considering the efficiency of goal-directed movements in these unusual environments. Several studies provided a large set of evidence that gravity is taken into account during the planning stage of...
Article
Full-text available
Insects’ aptitude to perform hovering, automatic landing and tracking tasks involves accurately controlling their head and body roll and pitch movements, but how this attitude control depends on an internal estimation of gravity orientation is still an open question. Gravity perception in flying insects has mainly been studied in terms of grounded...
Poster
Full-text available
Abstract Astronauts’ training is classically performed in a pool in order to reproduce a weightless environment by making use of Archimedes upthrust and buoyancy state. However, this training method has not been scientifically validated yet, and requires first to study the effects of underwater exposure on motor behaviour. The aim of this study is...
Article
Full-text available
Astronauts' training is conventionally performed in a pool to reproduce weightlessness by exploiting buoyancy which is supposed to reduce the impact of gravity on the body. However, this training method has not been scientifically validated yet, and requires first to study the effects of underwater exposure on motor behavior. We examined the influe...
Article
Full-text available
Background: Helicopter pilots are involved in a complex multitask activity, implying overuse of cognitive resources, which may result in piloting task impairment or in decision-making failure. Studies usually investigate this phenomenon in well-controlled, poorly ecological situations by focusing on the correlation between physiological values and...
Article
Full-text available
Hoverflies' ability to control their head orientation with respect to their body contributes importantly to their agility and their autonomous navigation abilities. Many tasks performed by this insect during flight, especially while hovering, involve a head stabilization reflex. This reflex mediated by multisensory channels prevents the visual proc...
Article
Full-text available
Humans can remarkably adapt their motor behavior to novel environmental conditions, yet it remains unclear which factors enable us to transfer what we have learned with one limb to the other. Here we tested the hypothesis that interlimb transfer of sensorimotor adaptation is determined by environmental conditions but also by individual characterist...
Conference Paper
Full-text available
Astronauts' training is conventionally performed in a pool in order to reproduce a weightless environment and facilitate motor performance during extra-vehicular activities. To that purpose, astronauts are usually immersed in a pressurized spacesuit, facing tasks involving accurate goal-directed actions. However, this method has not yet been scient...
Article
Full-text available
This study investigated the influence of pitch body tilt on judging the possibility of passing under high obstacles in presence of an illusory horizontal self-motion. Seated subjects tilted at various body orientations were asked to estimate the possibility of passing under a projected bar (i.e., a parking barrier), while imagining a forward whole-...
Conference Paper
Full-text available
This paper uses Bayesian networks to investigate the impact of three different kind of inputs, namely, physiological, cognitive and affect features, on workload estimation, from a computational point of view. The ability of the proposed models to infer the workload variation of subjects involved in successive tasks demanding different levels of cog...
Conference Paper
Full-text available
This paper presents an approach based on Bayesian Networks to estimate the workload of operators. The models take as inputs the entropy of different number of physiological features, as well as a cognitive feature (reaction time to a secondary task). They output the workload variation of subjects involved in successive tasks demanding different lev...
Conference Paper
Full-text available
Shape and mechanical structure of instruments play a large part in the lack of ergonomics during laparoscopic surgery. Providing intra-abdominal mobility and rethinking handles design are two solutions to increase comfort and precision of gestures. Based on previous work that determined the optimal intra-abdominal kinematics, this study analyses th...
Conference Paper
Full-text available
While modern dynamic driving simulators equipped with six degrees-of-freedom (6-DOF) hexapods and X-Y platforms have improved realism, mechanical limitations prevent them from offering a fully realistic driving experience. Solutions are often sought in the ”washout” algorithm, with linear accelerations simulated by an empirically chosen combination...
Article
Full-text available
Execution of a saccadic eye movement towards the goal of a hand pointing movement improves the accuracy of this hand movement. Still controversial is the role of extra-retinal signals, i.e. efference copy of the saccadic command and/or ocular proprioception, in the definition of the hand pointing target. We report here that hand pointing movements...
Article
Full-text available
Tilt-coordination is a technique which uses the tilt-translation ambiguity of the vestibular system to simulate linear accelerations on dynamic driving simulators, in combination with real linear accelerations. However, the tilt/translation ratio is chosen empirically. We experimentally determine the most realistic tilt/translation ratio to simulat...
Article
Full-text available
We studied the effect of static pitch body tilts on the perception of self-motion direction induced by a visual stimulus. Subjects were seated in front of a screen on which was projected a 3D cluster of moving dots visually simulating a forward motion of the observer with upward or downward directional biases (relative to a true earth horizontal di...
Article
Full-text available
Thanks to their different senses, human observers acquire multiple information coming from their environment. Complex cross-modal interactions occur during this perceptual process. This article proposes a framework to analyze and model these interactions through a rigorous and systematic data-driven process. This requires considering the general re...
Conference Paper
Full-text available
The perception of self-motion direction was usually investigated through a task that required to be assessed relative to body-fixed elements or other features of the environment. However, less is known about self-motion perception through a task that required to be achieved relative to some earth-based directions, such as the gravity or the horizon...
Conference Paper
Full-text available
Ces dernières années, avec le déploiement du Rafale et de l’hélicoptère Tigre, l’industrie aéronautique française s’est vue attribuée un programme de conception avionique d’envergure. Pour renforcer la sécurité des pilotes, la réalisation de tels projets appuie en amont la nécessité de mieux comprendre comment le cerveau humain se représente l’espa...
Article
Full-text available
Sensorimotor adaptation restores and maintains the accuracy of goal-directed movements. It remains unclear whether these adaptive mechanisms modify actions by controlling peripheral premotor stages that send commands to the effectors and/or earlier processing stages involved in registration of target location. Here, we studied the effect of adaptat...
Article
Full-text available
Because our environment and our body can change from time to time, the efficiency of human motor behavior relies on the updating of the neural processes transforming intentions into actions. Adaptation to the context critically depends on sensory feedback such as vision, touch or hearing. Although proprioception is not commonly listed as one of the...
Article
Full-text available
The authors investigated the relation between hand kinematics and eye movements in 2 variants of a rhythmical Fitts's task in which eye movements were necessary or not necessary. P. M. Fitts's (1954) law held in both conditions with similar slope and marginal differences in hand-kinematic patterns and movement continuity. Movement continuity and ey...
Conference Paper
Full-text available
The way humans can perceive the direction of visually-induced self-motion from optic flow is still largely discussed. A purely visual process on the basis of the retinal image motion alone (retinal cues) has first been advanced. However, multiple sources of information (extra retinal proprioceptive and/or vestibular cues) can also be involved. This...
Article
Full-text available
We investigated the influence of gaze elevation on judging the possibility of passing under high obstacles during pitch body tilts, while stationary, in absence of allocentric cues. Specifically, we aimed at studying the influence of egocentric references upon geocentric judgements. Seated subjects, orientated at various body orientations, were ask...
Conference Paper
Full-text available
When exposed to acoustic and visual stimuli, human observers may perceive them as originating either from a common or from distinct sources. Audiovisual perception includes both integration and segregation effects whose importance in the final percept depends on the stimuli spatio-temporal synchrony. This phenomenon has been studied through percept...