Papers by Patrick Cavanagh
The recovery of target locations in space across movements of eyes and head Le rétablissement des... more The recovery of target locations in space across movements of eyes and head Le rétablissement des positions d’un objet dans l’espace à travers des mouvements des yeux et de la tête
Springer eBooks, 1975
Holography refers to a broad class of storage and retreival processes based on the recording of i... more Holography refers to a broad class of storage and retreival processes based on the recording of interference patterns. As a model for a neural memory system, holography provides both associative and redundant storage along with a mathematically explicit description of the system's operation. was among the first to propose that memory was coded in terms of neural interference patterns and was let to this conclusion by his discovery of redundant storage in the brain. Twenty-seven years later, showed how such interference patterns might be stored so that the original information could be retrieved without distortion. In 1963, van Heerden noted the similarity between Bcurle's hypothesis and the more concise representation of the interference process offered by holographic theory. Subsequently, a number of authors have outlined, to varying degrees, the analogy between holographic and neural processes Westlake, , 196o, 1970)). Of these, only Westlake (196~, 1970)has given a detailed analysis of the neural mechanisms involved. His hypothesis, however, like Beurle's, places severe restrictions on the firing patterns of neurons that are at odds with the known properties of neural codes. This paper will demonstrate that holographic storage can be obtained when only the most general neural codes are assumed. A recognition system employing transmission holography is proposed and the limited capacity of this type of storage for multiple recordlags leads naturally to a modelling of short term memory. The system predicts a wide range of behavioral data in recognition tasks based on a single assumption concerning the properties of individual neurons. Before detailing the neural holographic processes, a brief description of optical holography will demonstrate some of the properties of this method of storage. Optical holography, developed by , allows the recording of both the phase and amplitude of a wavefront of light. Since photographic plates are sensitive to intensity but not to phase, the plate is exposed to two wavefronts simultaneously and the resulting interference pattern is recorded. If both wavefronts are monochromatic and coherent in phase, a stable interaction occurs so that the interference pattern codes both amplitude and phase in terms of intensity variations. The recorded interference pattern is the hologram; illuminating the hologram with one of the original wavefroats causes the
Endogenous attention biases transformational apparent motion based on high-level shape representations
Journal of Vision
There appear to be three independent systems for allocating attention: space-based, feature based... more There appear to be three independent systems for allocating attention: space-based, feature based, and object-based. Here, we review the literature of object-based attention to determine its underlying mechanisms. First, findings from unconscious priming and cuing suggest that the pre-attentive targets of object-based attention can be fully developed object representations. Next, the control of object-based attention appears to come from ventral visual areas specialized in object analysis that project downward to early visual areas. Whether feedback from object areas can accurately target the object’s specific locations and features is controversial, but recent work in autoencoding has made this plausible. Finally, we suggest that the three classic modes of attention may not be as independent as is commonly considered, and instead could rely on object-based attention for all three modes of selection. Specifically, studies show that attention can spread over the separated members of ...
Vision, 2021
We introduce a blind spot method to create image changes contingent on eye movements. One challen... more We introduce a blind spot method to create image changes contingent on eye movements. One challenge of eye movement research is triggering display changes contingent on gaze. The eye-tracking system must capture the image of the eye, discover and track the pupil and corneal reflections to estimate the gaze position, and then transfer this data to the computer that updates the display. All of these steps introduce delays that are often difficult to predict. To avoid these issues, we describe a simple blind spot method to generate gaze contingent display manipulations without any eye-tracking system and/or display controls.
Current biology : CB, Jan 6, 2017
Eye blinks cause disruptions to visual input and are accompanied by rotations of the eyeball [1].... more Eye blinks cause disruptions to visual input and are accompanied by rotations of the eyeball [1]. Like every motor action, these eye movements are subject to noise and introduce instabilities in gaze direction across blinks [2]. Accumulating errors across repeated blinks would be debilitating for visual performance. Here, we show that the oculomotor system constantly recalibrates gaze direction during blinks to counteract gaze instability. Observers were instructed to fixate a visual target while gaze direction was recorded and blinks were detected in real time. With every spontaneous blink-while eyelids were closed-the target was displaced laterally by 0.5° (or 1.0°). Most observers reported being unaware of displacements during blinks. After adapting for ∼35 blinks, gaze positions after blinks showed significant biases toward the new target position. Automatic eye movements accompanied each blink, and an aftereffect persisted for a few blinks after target displacements were elimin...
NeuroImage, Jun 22, 2017
When objects move or the eyes move, the visual system can predict the consequence and generate a ... more When objects move or the eyes move, the visual system can predict the consequence and generate a percept of the target at its new position. This predictive localization may depend on eye movement control in the frontal eye fields (FEF) and the intraparietal sulcus (IPS) and on motion analysis in the medial temporal area (MT). Across two experiments we examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, right MT, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion, both presented in the contralateral visual field. In trans-saccadic fusion trials, participants saccade toward a stimulus that is replaced with another stimulus during the saccade. Frequently, predictive position mechanisms lead to a fused percept of pre- and post-saccade stimuli (Paeye et al., 2017). We found that rTMS to IPS significantly decreased the fr...
Probes flashed within a moving frame are dramatically displaced (Özkan et al, 2021; Wong &Mack, 1... more Probes flashed within a moving frame are dramatically displaced (Özkan et al, 2021; Wong &Mack, 1981). The effect is much larger than that seen on static or moving probes (induced motion, Duncker, 1929; Wallach et al, 1978). These flashed probes are often perceived with the separation they have in frame coordinates — a 100% effect. Here we explore this frame effect on flashed tests with several versions of the standard stimulus. We find that the frame effect holds for smoothly or abruptly displacing frames, even when the frame changed shape or orientation between the endpoints of its travel. The path could be non-linear, even circular. The effect was driven by perceived not physical motion. When there were competing overlapping frames, the effect was determined by which frame was attended. There were a number of constraints that limited the effect. A static anchor near the flashes suppressed the effect but an extended static texture did not. If the probes were continuous rather than...
Introduction: why do we look at pictures? Artists have been looking at the world for thousands of... more Introduction: why do we look at pictures? Artists have been looking at the world for thousands of years, and thus paintings and drawings can be considered to form a -year-old corpus of experimental psychology of perception. Through observation and trial-and-error they have exploited the principles of how our brains interpret the input from the retina, giving priority to only certain regularities of the visual pattern. Thus, a study of pictorial cues can tell us about the way that the brain recognizes objects, understands spatial depth, and uses illumination information in natural environments. Conversely, a better understanding of visual perception may help to explain the effectiveness of certain techniques used by artists. Therefore this essay will focus on some basic techniques in pictorial depiction that allow blobs of paint or charcoal marks to evoke objects, depth, movement, transparency, illumination, and refl ection. The development of these pictorial techniques by artists can be considered as fundamental discoveries about the neuroscience of perception.
Le système visuel a évolué de manière à prendre en compte les conséquences de nos mouvements sur ... more Le système visuel a évolué de manière à prendre en compte les conséquences de nos mouvements sur notre perception. L’évolution nous a particulièrement doté de la capacité à percevoir notre environnement visuel comme stable et continu malgré les importants déplacements de ses projections sur nos rétines à chaque fois que nous déplaçons nos yeux, notre tête ou notre corps. Des études chez l’animal ont récemment montré que dans certaines aires corticales et sous-corticales, impliquées dans le contrôle attentionnel et dans l’élaboration des mouvements oculaires, des neurones sont capables d’anticiper les conséquences des futurs mouvements volontaires des yeux sur leurs entrées visuelles. Ces neurones prédisent ce à quoi ressemblera notre environnement visuel en re-cartographiant la position des objets d’importance à l’endroit qu’ils occuperont après l’exécution d’une saccade. Dans une série d’études, nous avons tout d’abord démontré que cette re- cartographie pouvait être évaluée de man...
Computer vision, besides being a key area in Computer Science, is present in various industrial a... more Computer vision, besides being a key area in Computer Science, is present in various industrial applications, such as traffic sign recognition (including car license plates), face and gesture recognition , content-based image retrieval, remote sensing, cartography, radar sensing, and robot mapping. However, most computer vision systems disregard the cognitive aspects of human perception , thus limiting their applicability in natural environments, whereby small changes in the light conditions cause negative effects on the system's accuracy. This seminar brought together contributions from Computer Vision, Cognitive Psychology, Philosophy and History of Art in order to discuss the information content in cast shadows which, although currently recognised by psychologists as providing important cues about depth perception, is considered as noise in the computer vision literature. Seminar May 3-8, 2015-http://www.dagstuhl.de/15192
Visual cognition, high-level vision, mid-level vision and top-down processing all refer to decisi... more Visual cognition, high-level vision, mid-level vision and top-down processing all refer to decision-based scene analyses that combine prior knowledge with retinal input to generate representations. The label "visual cognition" is little used at present, but research and experiments on mid-and high-level, inference-based vision have flourished, becoming in the 21st century a significant, if often understated part, of current vision research. How does visual cognition work? What are its moving parts? This paper reviews the origins and architecture of visual cognition and briefly describes some work in the areas of routines, attention, surfaces, objects, and events (motion, causality, and agency). Most vision scientists avoid being too explicit when presenting concepts about visual cognition, having learned that explicit models invite easy criticism. What we see in the literature is ample evidence for visual cognition, but few or only cautious attempts to detail how it might work. This is the great unfinished business of vision research: at some point we will be done with characterizing how the visual system measures the world and we will have to return to the question of how vision constructs models of objects, surfaces, scenes, and events.
ABSTRACTTo capture where things are and what they are doing, the visual system may extract the po... more ABSTRACTTo capture where things are and what they are doing, the visual system may extract the position and motion of each object relative to its surrounding frame of referencee.g., 1,2. Here we report a particularly powerful example where a paradoxical stabilization is produced by a moving frame. We first take a frame that moves left and right and we flash its right edge before, and its left edge after, the frame’s motion. For all frame displacements tested, the two edges are perceived as stabilized, with the left edge on the left and right edge on the right, separated by the frame’s width as if the frame were not moving. This illusory stabilization holds even when the frame travels farther than its width, reversing the actual spatial order of the two flashes. Despite this stabilization, the motion of the frame is still seen, albeit much reduced, and this hides the paradoxical standstill of relative positions. In a second experiment, two probes are flashed inside the frame at the s...
Perception, 2021
The descriptions of surfaces, objects, and events computed by visual processes are not solely for... more The descriptions of surfaces, objects, and events computed by visual processes are not solely for consumption in the visual system but are meant to be passed on to other brain centers. Clearly, the description of the visual scene cannot be sent in its entirety, like a picture or movie, to other centers, as that would require that each of them have their own visual system to decode the description. Some very compressed, annotated, or labeled version must be constructed that can be passed on in a format that other centers—memory, language, planning—can understand. If this is a “visual language,” what is its grammar? In a first pass, we see, among other things, differences in processing of visual “nouns,” visual “verbs,” and visual “prepositions.” Then we look at recursion and errors of visual grammar. Finally, the possibility of a visual language also raises the question of the acquisition of its grammar from the visual environment and the chance that this acquisition process was borr...
Journal of Vision, 2021
When an object casts a shadow on a background surface, both the offset of the shadow and the blur... more When an object casts a shadow on a background surface, both the offset of the shadow and the blur of its penumbra are potential cues to the distance between the object and the background. However, the shadow offset and blur are also affected by the direction and angular extent of the light source and these are often unknown. This means that the observer must make some assumptions about the illumination, the expected distribution of depth, or the relation between offset and depth in order to use shadows to make distance judgments. Here, we measure human judgments of perceived depth over a range of shadow offsets, blurs, and lighting directions to gain insight into this internal model. We find that distance judgments are relatively unaffected by blur or light direction, whereas the shadow offset has a strong and linear effect. The data are consistent with two models, a generic shadow-to-depth model and a Bayesian model.
Computer vision, besides being a key area in Computer Science, is present in various industrial a... more Computer vision, besides being a key area in Computer Science, is present in various industrial applications, such as traffic sign recognition (including car license plates), face and gesture recognition, content-based image retrieval, remote sensing, cartography, radar sensing, and robot mapping. However, most computer vision systems disregard the cognitive aspects of human perception, thus limiting their applicability in natural environments, whereby small changes in the light conditions cause negative effects on the system's accuracy. This seminar brought together contributions from Computer Vision, Cognitive Psychology, Philosophy and History of Art in order to discuss the information content in cast shadows which, although currently recognised by psychologists as providing important cues about depth perception, is considered as noise in the computer vision literature.
If a gabor pattern drifts in one direction while its internal texture drifts in the orthogonal di... more If a gabor pattern drifts in one direction while its internal texture drifts in the orthogonal direction, observers see a remarkable shift in its perceived direction when it is viewed in the periphery. The reported direction of the double-drift stimulus (also known as the infinite regress and curveball illusions) is some combination of the actual external motion of the gabor envelope and the internal motion of its texture (Tse & Hsieh, 2006). Here we find that if the observers track a fixation point that moves in tandem with the gabor, the illusion is undiminished. The pursuit of the moving fixation spot keeps the gabor roughly fixed at one location on the retina, cancelling its external motion, leaving only the internal motion. The gabor is seen to move in the world at roughly its actual speed as the motion of the eye is discounted at some point to recover velocities in world coordinates (e.g. Wallach, 1959). Our finding indicates that the combination of internal and external motio...
i-Perception
A random-dot background was expanded and contracted, and rotated, or expanded in one dimension wh... more A random-dot background was expanded and contracted, and rotated, or expanded in one dimension while contracting on the other, or skewed back and forth horizontally. Squares that were flashed at the reversal points of these affine pattern distortions, aligned to edges in the texture, showed massive changes in size and shape.
B1.01 Reversal of visual hemineglect: Differential influences of deactivating either contralatera... more B1.01 Reversal of visual hemineglect: Differential influences of deactivating either contralateral posterior parietal cortex or the superior colliculus.
Perception, 2016
An orbiting ray pattern produces an unexpected gray disk. Here we demonstrate this visual effect ... more An orbiting ray pattern produces an unexpected gray disk. Here we demonstrate this visual effect and its possible insights into visual temporal integration.
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Papers by Patrick Cavanagh