It is a well known fact that visual information is a powerful basis for the control of self-motio... more It is a well known fact that visual information is a powerful basis for the control of self-motion. Any movement of the observer in three dimensional space generates an optical inflow, consisting of the apparent movement of elements in the observer’s visual field. In most cases, this optical flow depends on the observer’s movements (of the body, head and eyes) and on the structure of the space involved. In this paper, the authors have shown how the combination of the rotational and transitional movements of the observer, made when driving a car, can generate complex optic flow. The usefulness of such optic flow in the control of self-motion could then depend on proprioceptive (extra-visual) information which would be necessary for the disassociation of the transitional and rotational components of the optic flow.
L’utilisation d’un simulateur de conduite pour la recherche en facteurs humains presente de nombr... more L’utilisation d’un simulateur de conduite pour la recherche en facteurs humains presente de nombreux avantages, tels que le controle experimental de plusieurs variables independantes, une reduction des couts, la securite et la facilite dans l’acquisition et la collecte de donnees. Cependant, la litterature decrit aussi des inconvenients associes a l’usage d’un simulateur comme : le mal du simulateur, la reproduction encore imprecise des sensations physiques, et surtout, la difficulte a etablir la validite ecologique des resultats obtenus. En depit des progres importants realises ces 40 dernieres annees pour retranscrire le plus fidelement possible l’experience sensorielle et motrice caracterisant l’activite de conduite, un manque de realisme semble toujours persister. Plus precisement, il s’agit d’un manque de validite psychologique qui peut s’apprehender comme la mesure selon laquelle les risques et les recompenses inherents a la simulation correspondent aux risques et aux recompenses inherents a la conduite reelle. Dans cet article, nous proposons d’aborder la validite comportementale sous l’angle de la validite psychologique au travers du concept de presence. Ce concept considere comme la capacite des individus a adopter des comportements similaires a ceux observes dans la vie quotidienne nous apparait interessant a utiliser pour interroger la validite comportementale a l’aide de mesures subjectives et objectives possiblement correlables. Cette approche est novatrice puisqu’elle nous permet de s’affranchir d’une methode d’evaluation de la validite usuellement pratiquee mais couteuse et complexe a mettre en place, a savoir celle de comparer des resultats provenant de la simulation avec ceux de la situation reelle. Cela permet ainsi de proposer une approche methodologique, sur la question de la validite des simulateurs, qui est moins contraignante et moins couteuse dans sa realisation.
A double-blind, placebo controlled, cross-over trial of sulfamethoxazole and trimethoprim was per... more A double-blind, placebo controlled, cross-over trial of sulfamethoxazole and trimethoprim was performed in a 62-year-old male patient who suffered from Machado-Joseph disease for 25 years. The patient, with cerebellar ataxia, akinetic-rigid syndrome and motor weakness but without any pyramidal features, had been chair-bound for 3 years before the trial. Bactrim therapy markedly improved performance on a physical examination which tested standing and gait, as compared to placebo session. Walker-assisted gait was possible again. For the first time, evaluation of spatio-temporal contrast sensitivity was performed and also revealed an improvement after Bactrim therapy as compared to placebo. These results suggest that Bactrim may be effective in degenerative neurological diseases and that Bactrim may have an overall effect on neurotransmission rather than solely possessing antispastic properties.
Summary— A large body of experimental evidence supports the hypothesis that dopamine is a functio... more Summary— A large body of experimental evidence supports the hypothesis that dopamine is a functional neuromodulator at many levels of the visual system. Intrinsic dopaminergic neurons were characterized in most mammalian retina, including man. These neurons give rise to a dendritic plexus covering the retina. Thus, dopamine seems to be involved in the organization of the ganglion cell and the bipolar cell receptive fields and modulates physiological activity of photoreceptors, both processes which underlie sensitivity and spatial selectivity of visual processing in the early stage of the visual system. Moreover, few data are now available concerning the functional significance of dopaminergic modulation of visual sensitivity in man. Parkinson's disease is a specific disorder of central dopaminergic systems. Abnormalities in the pattern‐evoked potentials and electroretinogram have been found in parkinsonian patients. Contrast sensitivity, a useful tool for measuring visual spatio‐temporal sensitivity in man, has also been shown to be modified due to this affection. Dynamic contrast sensitivity is primarily decreased in these patients, distinguishing them from the normal aging process. Because these modifications in shape of the contrast sensitivity function are reversed by L‐Dopa, and that neuroleptic administration could reproduce them in schizophrenian patients, it was suggested that dopamine might tune the contrast sensitivity function in man. We have recently shown that subcutaneous apomorphine induces changes in contrast sensitivity in healthy volunteers, which preferentially affect motion sensitivity. These dopaminergic sensitive modifications in the shape of the contrast sensitivity function might reflect a change in the range of sensitivity of the visual system, both in dynamic and spatial properties. This could be explained by a modification in the spatial and dynamic properties of the ganglion cell responses in the retina. Moreover, we suggest both from our results and from the review of the literature that human psychophysical data confirm the hypothesis that dopamine may be involved in light retinal adaptation, as light‐induced and dopamine‐induced modifications in the shape in the contrast sensitivity function are quite similar.
Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteer... more Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteers was performed with a fully automatic motion analyser. The recording included stride parameters for walking velocity, stride length, stride duration and swing time. Maximal amplitudes of rotation of the hip, knee and ankle were also recorded. The analysis was performed for the PD's patients before and after L-Dopa intake. All the patients walked with and without transversal stripes on the floor. The contrasting white lines were 45 cm apart. After medication, the stride length, the velocity and the swing phase duration were significantly increased. The movements around the hip, knee and ankle joints that were initially reduced, poorly increased after L-Dopa intake. When stripes were placed on the floor, no significant changes occurred for the overall group of patients. Seven parkinsonian patients did improve with visual guidance, increasing their stride length and their speed. Some rotations of hip and knee were also influenced by stripes. This sub-group of patients was characterized by older age, a slower walking velocity, a smaller stride length and a shorter swing time. We correlated the sensitivity to visual cues to the defect of the visual contrast sensitivity that has been established in PD by several recent works. Locomotion on the transverse lines might have produced a motion perception at a rate determined by the speed of the patient. For appropriate intervals between stripes, one can hypothesise that the resulting visual stimuli belonged to a range of spatio-temporal frequencies that are decreased in patients with PD.
In a series of experiments we studied the relationships between the characteristics of optokineti... more In a series of experiments we studied the relationships between the characteristics of optokinetic oculomotor responses triggered spontaneously by large-field visual motion and the perception of depth from motion parallax cues. Random-dot dynamic displays were projected at 60 Hz frame rate. Oculomotor behaviour was monitored with an infrared device. Subjects were asked to identify the spatial structure specified by optical motion and their responses were recorded with a mouse device. Results were as follows: (1) In all cases optokinetic responses are triggered when subjects are presented with visual displays specifying either a single surface, many surfaces or a cloud of dots receding in depth. (2) The velocity of slow phases of the optokinetic nystagmus changes from matching the average velocity of a display in early phases after the onset of a stimulation to slowing down to the slowest velocity in the display, for a small number of surfaces specified by motion parallax cues. (3) S...
The main objective of this study is to improve maintenance activities using mixed reality. Co-des... more The main objective of this study is to improve maintenance activities using mixed reality. Co-design work with Support Engineers was undertaken to develop a mixed reality solution that corresponded to the different needs of task sequencing feasibility. Multiple versions of the solution were tested using Microsoft HoloLens hardware to achieve continuous improvement. The study compared the two latest versions of the solution: the CAD version and the PHYS version. The CAD version was an immersive version inspired by CATIA CAD software, while the PHYS version implemented a realistic approach to parts handling (including gravity, continuous presence, and spatial organization of physical parts on a real table). Support Engineers carried out an experiment, performing a disassembly/assembly task using both versions of the solution. Results showed that the overall workload was significantly reduced, along with task completion time, using the PHYS solution. The PHYS version was also judged to be more usable than the CAD version. Adding 'pseudo-natural' manipulation of virtual objects to a maintenance task simulation better suits the needs of Support Engineers.
A great deal of research today is concerned with the study of the cognitive processes involved in... more A great deal of research today is concerned with the study of the cognitive processes involved in the realization of spatial displacements. In this article, we will analyze how the introduction of interfaces affects the conditions in which a displacement is produced and controlled. We will attempt to show that as the situation becomes less and less natural, the already important role played by visual information increases and the ways in which visual information is presented on the interfaces change as the modalities increase in number. Our discussion will not only be supported by fundamental and applied research on the mental representation of space and the visual control of displacement, but also by the few available studies on tele-operated situations.
It is a well known fact that visual information is a powerful basis for the control of self-motio... more It is a well known fact that visual information is a powerful basis for the control of self-motion. Any movement of the observer in three dimensional space generates an optical inflow, consisting of the apparent movement of elements in the observer’s visual field. In most cases, this optical flow depends on the observer’s movements (of the body, head and eyes) and on the structure of the space involved. In this paper, the authors have shown how the combination of the rotational and transitional movements of the observer, made when driving a car, can generate complex optic flow. The usefulness of such optic flow in the control of self-motion could then depend on proprioceptive (extra-visual) information which would be necessary for the disassociation of the transitional and rotational components of the optic flow.
L’utilisation d’un simulateur de conduite pour la recherche en facteurs humains presente de nombr... more L’utilisation d’un simulateur de conduite pour la recherche en facteurs humains presente de nombreux avantages, tels que le controle experimental de plusieurs variables independantes, une reduction des couts, la securite et la facilite dans l’acquisition et la collecte de donnees. Cependant, la litterature decrit aussi des inconvenients associes a l’usage d’un simulateur comme : le mal du simulateur, la reproduction encore imprecise des sensations physiques, et surtout, la difficulte a etablir la validite ecologique des resultats obtenus. En depit des progres importants realises ces 40 dernieres annees pour retranscrire le plus fidelement possible l’experience sensorielle et motrice caracterisant l’activite de conduite, un manque de realisme semble toujours persister. Plus precisement, il s’agit d’un manque de validite psychologique qui peut s’apprehender comme la mesure selon laquelle les risques et les recompenses inherents a la simulation correspondent aux risques et aux recompenses inherents a la conduite reelle. Dans cet article, nous proposons d’aborder la validite comportementale sous l’angle de la validite psychologique au travers du concept de presence. Ce concept considere comme la capacite des individus a adopter des comportements similaires a ceux observes dans la vie quotidienne nous apparait interessant a utiliser pour interroger la validite comportementale a l’aide de mesures subjectives et objectives possiblement correlables. Cette approche est novatrice puisqu’elle nous permet de s’affranchir d’une methode d’evaluation de la validite usuellement pratiquee mais couteuse et complexe a mettre en place, a savoir celle de comparer des resultats provenant de la simulation avec ceux de la situation reelle. Cela permet ainsi de proposer une approche methodologique, sur la question de la validite des simulateurs, qui est moins contraignante et moins couteuse dans sa realisation.
A double-blind, placebo controlled, cross-over trial of sulfamethoxazole and trimethoprim was per... more A double-blind, placebo controlled, cross-over trial of sulfamethoxazole and trimethoprim was performed in a 62-year-old male patient who suffered from Machado-Joseph disease for 25 years. The patient, with cerebellar ataxia, akinetic-rigid syndrome and motor weakness but without any pyramidal features, had been chair-bound for 3 years before the trial. Bactrim therapy markedly improved performance on a physical examination which tested standing and gait, as compared to placebo session. Walker-assisted gait was possible again. For the first time, evaluation of spatio-temporal contrast sensitivity was performed and also revealed an improvement after Bactrim therapy as compared to placebo. These results suggest that Bactrim may be effective in degenerative neurological diseases and that Bactrim may have an overall effect on neurotransmission rather than solely possessing antispastic properties.
Summary— A large body of experimental evidence supports the hypothesis that dopamine is a functio... more Summary— A large body of experimental evidence supports the hypothesis that dopamine is a functional neuromodulator at many levels of the visual system. Intrinsic dopaminergic neurons were characterized in most mammalian retina, including man. These neurons give rise to a dendritic plexus covering the retina. Thus, dopamine seems to be involved in the organization of the ganglion cell and the bipolar cell receptive fields and modulates physiological activity of photoreceptors, both processes which underlie sensitivity and spatial selectivity of visual processing in the early stage of the visual system. Moreover, few data are now available concerning the functional significance of dopaminergic modulation of visual sensitivity in man. Parkinson's disease is a specific disorder of central dopaminergic systems. Abnormalities in the pattern‐evoked potentials and electroretinogram have been found in parkinsonian patients. Contrast sensitivity, a useful tool for measuring visual spatio‐temporal sensitivity in man, has also been shown to be modified due to this affection. Dynamic contrast sensitivity is primarily decreased in these patients, distinguishing them from the normal aging process. Because these modifications in shape of the contrast sensitivity function are reversed by L‐Dopa, and that neuroleptic administration could reproduce them in schizophrenian patients, it was suggested that dopamine might tune the contrast sensitivity function in man. We have recently shown that subcutaneous apomorphine induces changes in contrast sensitivity in healthy volunteers, which preferentially affect motion sensitivity. These dopaminergic sensitive modifications in the shape of the contrast sensitivity function might reflect a change in the range of sensitivity of the visual system, both in dynamic and spatial properties. This could be explained by a modification in the spatial and dynamic properties of the ganglion cell responses in the retina. Moreover, we suggest both from our results and from the review of the literature that human psychophysical data confirm the hypothesis that dopamine may be involved in light retinal adaptation, as light‐induced and dopamine‐induced modifications in the shape in the contrast sensitivity function are quite similar.
Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteer... more Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteers was performed with a fully automatic motion analyser. The recording included stride parameters for walking velocity, stride length, stride duration and swing time. Maximal amplitudes of rotation of the hip, knee and ankle were also recorded. The analysis was performed for the PD's patients before and after L-Dopa intake. All the patients walked with and without transversal stripes on the floor. The contrasting white lines were 45 cm apart. After medication, the stride length, the velocity and the swing phase duration were significantly increased. The movements around the hip, knee and ankle joints that were initially reduced, poorly increased after L-Dopa intake. When stripes were placed on the floor, no significant changes occurred for the overall group of patients. Seven parkinsonian patients did improve with visual guidance, increasing their stride length and their speed. Some rotations of hip and knee were also influenced by stripes. This sub-group of patients was characterized by older age, a slower walking velocity, a smaller stride length and a shorter swing time. We correlated the sensitivity to visual cues to the defect of the visual contrast sensitivity that has been established in PD by several recent works. Locomotion on the transverse lines might have produced a motion perception at a rate determined by the speed of the patient. For appropriate intervals between stripes, one can hypothesise that the resulting visual stimuli belonged to a range of spatio-temporal frequencies that are decreased in patients with PD.
In a series of experiments we studied the relationships between the characteristics of optokineti... more In a series of experiments we studied the relationships between the characteristics of optokinetic oculomotor responses triggered spontaneously by large-field visual motion and the perception of depth from motion parallax cues. Random-dot dynamic displays were projected at 60 Hz frame rate. Oculomotor behaviour was monitored with an infrared device. Subjects were asked to identify the spatial structure specified by optical motion and their responses were recorded with a mouse device. Results were as follows: (1) In all cases optokinetic responses are triggered when subjects are presented with visual displays specifying either a single surface, many surfaces or a cloud of dots receding in depth. (2) The velocity of slow phases of the optokinetic nystagmus changes from matching the average velocity of a display in early phases after the onset of a stimulation to slowing down to the slowest velocity in the display, for a small number of surfaces specified by motion parallax cues. (3) S...
The main objective of this study is to improve maintenance activities using mixed reality. Co-des... more The main objective of this study is to improve maintenance activities using mixed reality. Co-design work with Support Engineers was undertaken to develop a mixed reality solution that corresponded to the different needs of task sequencing feasibility. Multiple versions of the solution were tested using Microsoft HoloLens hardware to achieve continuous improvement. The study compared the two latest versions of the solution: the CAD version and the PHYS version. The CAD version was an immersive version inspired by CATIA CAD software, while the PHYS version implemented a realistic approach to parts handling (including gravity, continuous presence, and spatial organization of physical parts on a real table). Support Engineers carried out an experiment, performing a disassembly/assembly task using both versions of the solution. Results showed that the overall workload was significantly reduced, along with task completion time, using the PHYS solution. The PHYS version was also judged to be more usable than the CAD version. Adding 'pseudo-natural' manipulation of virtual objects to a maintenance task simulation better suits the needs of Support Engineers.
A great deal of research today is concerned with the study of the cognitive processes involved in... more A great deal of research today is concerned with the study of the cognitive processes involved in the realization of spatial displacements. In this article, we will analyze how the introduction of interfaces affects the conditions in which a displacement is produced and controlled. We will attempt to show that as the situation becomes less and less natural, the already important role played by visual information increases and the ways in which visual information is presented on the interfaces change as the modalities increase in number. Our discussion will not only be supported by fundamental and applied research on the mental representation of space and the visual control of displacement, but also by the few available studies on tele-operated situations.
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Papers by Daniel Mestre