18 results on '"Wexler, Mark"'
Search Results
2. Masking the saccadic smear.
- Author
-
Duyck M, Collins T, and Wexler M
- Subjects
- Humans, Perceptual Masking physiology, Retina physiology, Saccades physiology, Visual Perception physiology
- Abstract
Static visual stimuli are smeared across the retina during saccades, but in normal conditions this smear is not perceived. Instead, we perceive the visual scene as static and sharp. However, retinal smear is perceived if stimuli are shown only intrasaccadically, but not if the stimulus is additionally shown before a saccade begins, or after the saccade ends (Campbell & Wurtz, 1978). This inhibition has been compared to forward and backward metacontrast masking, but with spatial relations between stimulus and mask that are different from ordinary metacontrast during fixation. Previous studies of smear masking have used subjective measures of smear perception. Here we develop a new, objective technique for measuring smear masking, based on the spatial localization of a gap in the smear created by very quickly blanking the stimulus at various points during the saccade. We apply this technique to show that smear masking survives dichoptic presentation (suggesting that it is therefore cortical in origin), as well as separations of as much as 6° between smear and mask.
- Published
- 2016
- Full Text
- View/download PDF
3. Persistent states in vision break universality and time invariance.
- Author
-
Wexler M, Duyck M, and Mamassian P
- Subjects
- Female, Humans, Male, Models, Neurological, Visual Perception physiology
- Abstract
Studies of perception usually emphasize processes that are largely universal across observers and--except for short-term fluctuations--stationary over time. Here we test the universality and stationarity assumptions with two families of ambiguous visual stimuli. Each stimulus can be perceived in two different ways, parameterized by two opposite directions from a continuous circular variable. A large-sample study showed that almost all observers have preferred directions or biases, with directions lying within 90 degrees of the bias direction nearly always perceived and opposite directions almost never perceived. The biases differ dramatically from one observer to the next, and although nearly every bias direction occurs in the population, the population distributions of the biases are nonuniform, featuring asymmetric peaks in the cardinal directions. The biases for the two families of stimuli are independent and have distinct population distributions. Following external perturbations and spontaneous fluctuations, the biases decay over tens of seconds toward their initial values. Persistent changes in the biases are found on time scales of several minutes to 1 hour. On scales of days to months, the biases undergo a variety of dynamical processes such as drifts, jumps, and oscillations. The global statistics of a majority of these long-term time series are well modeled as random walk processes. The measurable fluctuations of these hitherto unknown degrees of freedom show that the assumptions of universality and stationarity in perception may be unwarranted and that models of perception must include both directly observable variables as well as covert, persistent states.
- Published
- 2015
- Full Text
- View/download PDF
4. Orthogonal steps relieve saccadic suppression.
- Author
-
Wexler M and Collins T
- Subjects
- Humans, Photic Stimulation methods, Retina physiology, Saccades physiology, Visual Perception physiology
- Abstract
Although the retinal position of objects changes with each saccadic eye movement, we perceive the visual world to be stable. How this visual stability or constancy arises is debated. Cancellation accounts propose that the retinal consequences of eye movements are compensated for by an equal-but-opposite eye movement signal. Assumption accounts propose that saccade-induced retinal displacements are ignored because we have a prior belief in a stable world. Saccadic suppression of displacement-the fact that small displacements of the visual targets during saccades go unnoticed-argues in favor of assumption accounts. Extinguishing the target before the displacement unmasks it, arguing in favor of cancellation accounts. We show that an irrelevant displacement of the target orthogonal to saccade direction unmasks displacements parallel to saccade direction, and therefore relieves saccadic suppression of displacement. This result suggests that visual stability arises from the interplay between cancellation and assumption mechanisms: When the post-saccadic target position falls within an elliptic region roughly equivalent to habitual saccadic variability, displacements are not seen and stability is assumed. When the displacements fall outside this region, as with our orthogonal steps, displacements are seen and positions are remapped.
- Published
- 2014
- Full Text
- View/download PDF
5. The reference frame of the tilt aftereffect.
- Author
-
Knapen T, Rolfs M, Wexler M, and Cavanagh P
- Subjects
- Adaptation, Physiological physiology, Adult, Humans, Photic Stimulation methods, Psychophysics, Young Adult, Figural Aftereffect physiology, Head Movements physiology, Orientation physiology, Saccades physiology, Visual Perception physiology
- Abstract
Perceptual aftereffects provide a sensitive tool to investigate the influence of eye and head position on visual processing. There have been recent indications that the TAE is remapped around the time of a saccade to remain aligned to the adapting location in the world. Here, we investigate the spatial frame of reference of the TAE by independently manipulating retinal position, gaze orientation, and head orientation between adaptation and test. The results show that the critical factor in the TAE is the correspondence between the adaptation and test locations in a retinotopic frame of reference, whereas world- and head-centric frames of reference do not play a significant role. Our results confirm that adaptation to orientation takes place at retinotopic levels of visual processing. We suggest that the remapping process that plays a role in visual stability does not transfer feature gain information around the time of eye (or head) movements.
- Published
- 2010
- Full Text
- View/download PDF
6. Anticipating the Three-Dimensional Consequences of Eye Movements
- Author
-
Wexler, Mark and Held, Richard M.
- Published
- 2005
7. Default perception of high-speed motion
- Author
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Wexler, Mark, Glennerster, Andrew, Cavanagh, Patrick, Ito, Hiroyuki, and Seno, Takeharu
- Published
- 2013
8. Observer Movement and Size Constancy
- Author
-
Combe, Emmanuelle and Wexler, Mark
- Published
- 2010
9. Voluntary Head Movement and Allocentric Perception of Space
- Author
-
Wexler, Mark
- Published
- 2003
10. Bifurcation in brain dynamics reveals a signature of conscious processing independent of report
- Author
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Sergent, Claire, Corazzol, Martina, Labouret, Ghislaine, Stockart, François, Wexler, Mark, King, Jean-Rémi, Meyniel, Florent, Pressnitzer, Daniel, Centre National de la Recherche Scientifique (CNRS), Université de Paris (UP), Centre Neurosciences intégratives et Cognition (INCC - UMR 8002), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire des systèmes perceptifs (LSP), Département d'Etudes Cognitives - ENS Paris (DEC), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Adult ,Male ,Behavior ,Adolescent ,Consciousness ,Science ,[SCCO.NEUR]Cognitive science/Neuroscience ,Cognitive Neuroscience ,Brain ,Electroencephalography ,Article ,[SCCO]Cognitive science ,Young Adult ,Acoustic Stimulation ,[SCCO.PSYC]Cognitive science/Psychology ,Human behaviour ,Auditory Perception ,Visual Perception ,Humans ,Auditory system ,Psychology ,Female ,Neuroscience - Abstract
An outstanding challenge for consciousness research is to characterize the neural signature of conscious access independently of any decisional processes. Here we present a model-based approach that uses inter-trial variability to identify the brain dynamics associated with stimulus processing. We demonstrate that, even in the absence of any task or behavior, the electroencephalographic response to auditory stimuli shows bifurcation dynamics around 250–300 milliseconds post-stimulus. Namely, the same stimulus gives rise to late sustained activity on some trials, and not on others. This late neural activity is predictive of task-related reports, and also of reports of conscious contents that are randomly sampled during task-free listening. Source localization further suggests that task-free conscious access recruits the same neural networks as those associated with explicit report, except for frontal executive components. Studying brain dynamics through variability could thus play a key role for identifying the core signatures of conscious access, independent of report., Current knowledge on the neural basis of consciousness mostly relies on situations where people report their perception. Here, the authors provide evidence for the idea that bifurcation in brain dynamics reflects conscious perception independent of report.
- Published
- 2019
11. Persistent states in vision break universality and time invariance
- Author
-
Wexler, Mark, Duyck, Marianne, and Mamassian, Pascal
- Subjects
Male ,Models, Neurological ,Visual Perception ,Humans ,Female ,Biological Sciences - Abstract
Studies of perception usually emphasize processes that are largely universal across observers and--except for short-term fluctuations--stationary over time. Here we test the universality and stationarity assumptions with two families of ambiguous visual stimuli. Each stimulus can be perceived in two different ways, parameterized by two opposite directions from a continuous circular variable. A large-sample study showed that almost all observers have preferred directions or biases, with directions lying within 90 degrees of the bias direction nearly always perceived and opposite directions almost never perceived. The biases differ dramatically from one observer to the next, and although nearly every bias direction occurs in the population, the population distributions of the biases are nonuniform, featuring asymmetric peaks in the cardinal directions. The biases for the two families of stimuli are independent and have distinct population distributions. Following external perturbations and spontaneous fluctuations, the biases decay over tens of seconds toward their initial values. Persistent changes in the biases are found on time scales of several minutes to 1 hour. On scales of days to months, the biases undergo a variety of dynamical processes such as drifts, jumps, and oscillations. The global statistics of a majority of these long-term time series are well modeled as random walk processes. The measurable fluctuations of these hitherto unknown degrees of freedom show that the assumptions of universality and stationarity in perception may be unwarranted and that models of perception must include both directly observable variables as well as covert, persistent states.
- Published
- 2015
12. Structure of visual biases revealed by individual differences.
- Author
-
Wexler, Mark, Mamassian, Pascal, and Schütz, Alexander C.
- Subjects
- *
VISUAL perception , *STIMULUS & response (Biology) , *MOTION perception (Vision) , *PSYCHOLOGY of movement , *RETINA - Abstract
Multiple studies have shown that certain visual stimuli are perceived in accordance with strong biases that are both robust within individuals and highly variable from one individual to the next. These biases undergo small changes over time that demonstrate that they constitute latent states of the visual system. The literature to date indicates that the individual biases for different stimulus classes are independent of each other. Here we asked whether some of these biases are nonetheless related to one another. We measured individual biases for five classes of stimuli in 1000 participants. The stimuli were two different versions of two-dimensional apparent motion, smooth motion in Glass patterns, and two different structure-from-motion stimuli. There were pronounced individual biases in all stimuli, and these biases varied in direction and strength across individuals. Some biases were not independent: the two biases for apparent motion direction were most strongly correlated, and they were both correlated, but less strongly, to the bias direction for smooth motion. While all other pairs of biases had unrelated directions, the strengths of all biases were correlated. The correlation of bias strengths may be due to either a common factor across the stimulus types, or an attentional effect. Only a tiny fraction of the between-participant variance can be explained by age and gender. These results show that latent states of the visual system that we measure as individual biases are organized in a structured way, and call out for further study of this under-explored aspect of visual perception. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
13. Depth Affects Where We Look
- Author
-
Wexler, Mark and Ouarti, Nizar
- Subjects
- *
EYE movements , *DEPTH perception , *VISUAL perception , *SACCADIC eye movements , *CHEMICAL senses - Abstract
Summary: Understanding how we spontaneously scan the visual world through eye movements is crucial for characterizing both the strategies and inputs of vision . Despite the importance of the third or depth dimension for perception and action, little is known about how the specifically three-dimensional aspects of scenes affect looking behavior. Here we show that three-dimensional surface orientation has a surprisingly large effect on spontaneous exploration, and we demonstrate that a simple rule predicts eye movements given surface orientation in three dimensions: saccades tend to follow surface depth gradients. The rule proves to be quite robust: it generalizes across depth cues, holds in the presence or absence of a task, and applies to more complex three-dimensional objects. These results not only lead to a more accurate understanding of visuo-motor strategies, but also suggest a possible new oculomotor technique for studying three-dimensional vision from a variety of depth cues in subjects—such as animals or human infants—that cannot explicitly report their perceptions. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
14. Visual perception of planar orientation: dominance of static depth cues over motion cues
- Author
-
Cornilleau-Pérès, Valérie, Wexler, Mark, Droulez, Jacques, Marin, Emmanuel, Miège, Christian, and Bourdoncle, Bernard
- Subjects
- *
VISUAL perception , *MENTAL orientation - Abstract
We measured the ability to report the tilt (direction of maximal slope) of a plane under monocular viewing conditions, from static depth cues (square grid patterns) and motion parallax (small rotations of the plane about a frontoparallel axis). These two cues were presented separately, or simultaneously. In the latter case they specified tilts that were either collinear (coherent case) or orthogonal (conflict case). The field of view was small (
8° ) or large (60° ). In small field, for motion parallax, the reported tilt depends strongly on the orientation of the plane relative to the rotation axis, being totally ambiguous when tilt is collinear with the rotation axis. In contrast, in large field, the reported tilt depends little on this variable, and is accurately specified by motion cues. In both cases static cues strongly dominated the tilt reports. Hence static grid patterns constitute robust tilt cues, which can dominate contradictory tilt indications from motion parallax, and should be considered as essential for the visual orientation during locomotion, or the immersion in virtual reality environments. [Copyright &y& Elsevier]- Published
- 2002
- Full Text
- View/download PDF
15. Self-motion and the perception of stationary objects.
- Author
-
Wexler, Mark, Panerai, Francesco, Lamouret, Ivan, and Droulez, Jacques
- Subjects
- *
MOTION perception (Vision) , *VISUAL perception , *DEPTH perception , *VISION - Abstract
Shows that the rigidity hypothesis, in which a passive observer in an environment of moving rigid objects can be used as a substitute for an active observer moving in an environment of stationary objects, is inadequate. Dependence on extraretinal information about self-movement for active observers' perception of three-dimensional structure; Difference in the way the visual system treats stationary and rigid objects; Role of action in depth perception; Argument for the revision of the rigidity hypothesis.
- Published
- 2001
- Full Text
- View/download PDF
16. Motion Masking by Stationary Objects: A Study of Simulated Saccades.
- Author
-
Duyck, Marianne, Wexler, Mark, Castet, Eric, and Collins, Thérèse
- Subjects
- *
VISUAL perception , *PSYCHOLOGY of movement , *SACCADIC eye movements , *MOTION perception (Vision) , *OPTICAL information processing - Abstract
Saccades are crucial to visual information intake by re-orienting the fovea to regions of interest in the visual scene. However, they cause drastic disruptions of the retinal input by shifting the retinal image at very high speeds. The resulting motion and smear are barely noticed, a phenomenon known as saccadic omission. Here, we studied the perception of motion during simulated saccades while observers fixated, moving naturalistic visual scenes across the retina with saccadic speed profiles using a very high temporal frequency display. We found that the mere presence of static pre- and post-saccadic images significantly reduces the perceived amplitude of motion but does not eliminate it entirely. This masking of motion perception could make the intra-saccadic stimulus much less salient and thus easier to ignore. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
17. More to 3-D vision than meets the eye
- Author
-
Wexler, Mark
- Subjects
- *
VISUAL perception , *RECOGNITION (Psychology) , *VISUAL discrimination - Abstract
Does self-motion affect object recognition? Researchers have long studied how 3-D objects are recognized from different points of view, but have disregarded the observers’ own movement by keeping them motionless. A recent study by Simons et al. shows that self-motion cannot be ignored, as it changes the way that objects are recognized. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
18. Voluntary head movement and allocentric perception of space
- Author
-
Mark Wexler, Laboratoire de Physiologie de la Perception et de l'Action (LPPA), Collège de France (CdF (institution))-Centre National de la Recherche Scientifique (CNRS), and Wexler, Mark
- Subjects
Vision Disparity ,Visual perception ,media_common.quotation_subject ,Frame of reference ,050105 experimental psychology ,03 medical and health sciences ,0302 clinical medicine ,Orientation ,Perception ,Psychophysics ,Humans ,0501 psychology and cognitive sciences ,Motion perception ,Persistence of vision ,Kinesthesis ,General Psychology ,media_common ,depth perception ,Communication ,business.industry ,05 social sciences ,Voluntary motion ,Observer (special relativity) ,Awareness ,motion perception ,Form Perception ,Head Movements ,Space Perception ,Egocentric bias ,[SCCO.PSYC] Cognitive science/Psychology ,[SCCO.PSYC]Cognitive science/Psychology ,Psychology ,Depth perception ,business ,030217 neurology & neurosurgery ,Cognitive psychology - Abstract
Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.
- Published
- 2002
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