Showing papers on "Visual perception published in 1987"
TL;DR: Psychophysical experiments on the interactions of color, form, depth, and movement in human perception are described, and it is attempted to correlate these aspects of visual perception with the different subdivisions of the visual system.
Abstract: Physiological and anatomical findings in the primate visual system, as well as clinical evidence in humans, suggest that different components of visual information processing are segregated into largely independent parallel pathways. Such a segregation leads to certain predictions about human vision. In this paper we describe psychophysical experiments on the interactions of color, form, depth, and movement in human perception, and we attempt to correlate these aspects of visual perception with the different subdivisions of the visual system.
1,569 citations
TL;DR: Three recent developments that have yielded insight into information processing and flow within extrastriate cortex are focused on.
Abstract: The neuronal processes that lead to visual perception have attracted intense interest since Kuffier's studies of receptive field organization in cat retinal ganglion cells over three decades ago (Kuffier 1953). A variety of ana tomical and physiological approaches have been employed to analyze the organization of thc visual pathway between the retina and striate cortex (VI ) and the transformations of visual information that occur at each stage (see Hubel & Wiesel 1977, Stone 1 983, Shapley & Lennie 1985). The growth in understanding of the retinostriate pathway has been accompanied by increasing interest in visual processing in the expanse of extrastriate cortex beyond V I . Studies of extrastriate cortex in many spec ies showed that it comprises a mosaic of visual areas that can be dis tinguished by several anatomical and physiological criteria (reviewed by Kaas 1 978, Zeki 1 978, Cowey 1979, Van Essen 1 979, 1985, Wagor et al 1980, Tusa et al 1 98 1) . The literature in this field is large, and we do not attempt to review all relevant studies. Rather, we concern ourselves with three recent devel opments that have yielded insight into information processing and flow within extrastriate cortex. The first of these is the convergence of ana tom-
1,227 citations
01 Dec 1987
TL;DR: In this article, the stability-plasticity dilemma and Adaptive Resonance Theory are discussed in the context of self-organizing learning and recognition systems, and the three R's: Recognition, Reinforcement, and Recall.
Abstract: : Partial Contents: Attention and Expectation in Self-Organizing Learning and Recognition Systems; The Stability-Plasticity Dilemma and Adaptive Resonance Theory; Competitive Learning Models; Self-Stabilized Learning by an ART Architecture in an Arbitrary Input Environment; Attentional Priming and Prediction: Matching by the 2/3 Rule; Automatic Control of Hypothesis Testing by Attentional-Orienting Interactions; Learning to Recognize an Analog World; Invariant Visual Pattern Recognition; The Three R's: Recognition, Reinforcement, and Recall; Self-Stabilization of Speech Perception and Production Codes: New Light on Motor Theory; and Psychophysiological and Neurophysiological Predictions of ART.
1,196 citations
TL;DR: A theory of some of these subsystems is formulated in light of an analysis of problems that must be solved by the visual system and the constraints on the solutions to these problems; computational, neurological, and behavioral constraints are considered.
Abstract: Visual recognition, navigation, tracking, and imagery are posited to share certain high-level processing subsystems. In the first part of this article, a theory of some of these subsystems is formulated. This theory is developed in light of an analysis of problems that must be solved by the visual system and the constraints on the solutions to these problems; computational, neurological, and behavioral constraints are considered. In the second part, inferences about perceptual subsystems are used to develop a theory of how mental images are generated. Support for this theory is adduced from studies of split-brain patients and a review of relevant neuropsychological findings. In the third part, a computational mechanism is developed to account for how visual function becomes lateralized in the brain; this mechanism is used to predict how the hypothesized processing subsystems become lateralized. In the fourth part, some critical tests of the theory of lateralization of perceptual processing subsystems are reported, and in the fifth part the theory is extended to account for the lateralization of image-transformation subsystems. In the sixth part, the theory is used to account for the almost ubiquitous variability (both between subjects and within subjects) evident in the neuropsychological literature on lateralization. Finally, in the concluding part of the article, the computational-neuropsychological approach is discussed and evaluated.
868 citations
Book•
01 Jan 1987
TL;DR: In this paper, the processing of information in face-to-face communication when a speaker makes both audible and visible information available to a perceiver is discussed. But the evaluation of the information source provides information about the strength of alternative interpretations, rather than just all-or-none categorical information, as claimed by "categorical perception" theory.
Abstract: This book is about the processing of information in face-to-face communication when a speaker makes both audible and visible information available to a perceiver. Both auditory and visual sources of information are evaluated and integrated to achieve speech perception. The evaluation of the information source provides information about the strength of alternative interpretations, rather than just all-or-none categorical information, as claimed by “categorical perception” theory. Information sources are evaluated independently; the integration process insures that the least ambiguous sources have the most influences on the judgment. Similar processes occur in a variety of other behaviors, ranging from personality judgments and categorization to sentence interpretation and decision making. The experimental results are consistent with a fuzzy logical model of perception, positing three operations in perceptual (primary) recognition: feature evaluation, feature integration, and pattern classification. Continuously valued features are first evaluated, then integrated and matched against prototype descriptions in memory; finally, an identification decision is made on the basis of the relative goodness-of-match of the stimulus information with the relevant prototype descriptions.
678 citations
TL;DR: The model appears to deal with the aperture problem as well as the human visual system since it extracts the correct velocity for patterns that have large differences in contrast at different spatial orientations, and it simulates psychophysical data on the coherence of sine-grating plaid patterns.
Abstract: A model is presented, consonant with current views regarding the neurophysiology and psychophysics of motion perception, that combines the outputs of a set of spatiotemporal motion-energy filters to extract optical flow. The output velocity is encoded as the peak in a distribution of velocity-tuned units that behave much like cells of the middle temporal area of the primate brain. The model appears to deal with the aperture problem as well as the human visual system since it extracts the correct velocity for patterns that have large differences in contrast at different spatial orientations, and it simulates psychophysical data on the coherence of sine-grating plaid patterns.
642 citations
608 citations
TL;DR: The results suggest that different pathways are modulated when attention is deployed to different regions of the visual fields, and suggest that the special role of the right hemisphere in spatial attention may be limited to analysis of information in the visual periphery.
517 citations
01 Jan 1987
491 citations
TL;DR: These studies employ the dual-task technique to determine whether covert visual orienting can take place while a person’s attention is engaged in a language processing task and find clear evidence of interference between the two tasks, which suggests some common operations.
Abstract: Recently our knowledge of the mechanisms of visual-spatial attention has improved because of studies employing single cell recording with alert monkeys and others using performance analysis of neurological patients. These studies suggest that a complex neural network that includes parts of the posterior parietal lobe and midbrain is involved in covert shifts of visual attention. Is this system an isolated visual attentional module or is it part of a more general attentional system? Our studies employ the dual-task technique to determine whether covert visual orienting can take place while a person’s attention is engaged in a language processing task. We find clear evidence of interference between the two tasks, which suggests some common operations. However, the results also indicate that whatever is common to the two tasks does not have the same anatomical location as that of visual-spatial attention.
488 citations
01 Sep 1987-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: A transform which maps an image into a set of images that vary in resolution and orientation, each pixel in the output may be regarded as the simulated response of a neuron in human visual cortex is described.
Abstract: With a goal of providing means for accelerating the image processing, machine vision, and testing of human vision models, an image transform was designed, which makes it possible to map an image into a set of images that vary in resolution and orientation. Each pixel in the output may be regarded as the simulated response of a neuron in human visual cortex. The transform is amenable to a number of shortcuts that greatly reduce the amount of computation.
TL;DR: In this article, the availability and saliency of object attributes under haptic exploration, with and without vision, were assessed by two tasks in which subjects sorted objects that varied factorially in size, shape, texture, and hardness.
Abstract: SUMMARY The availability and salience of object attributes under haptic exploration, with and without vision, were assessed by two tasks in which subjects sorted objects that varied factorially in size, shape, texture, and hardness. In the directed-discrimination task, subjeets were instructed to sort along a particular dimension. Although levels on all dimensions were easily discriminated, shape was relatively less so for haptic explorers without vision, as was hardness for those using vision and haptics. Size was least discriminable for both groups. In thefiee-sorting task, subjects were to sort objects by similarity. Three groups used haptic exploration only; these were differentiated by the experimenters' definition of object similarity: unbiased haptics (no particular definition of similarity), haptically biased hapties (similarity = objects feel similar), haptics plus visual imagery (similarity = objects' visual inmges are similar). A fourth group used vision as well as haptics, with instructions like those of the unbiased haptics group. Dimensional salience was measured by the extent to which levels on a dimension were differentiated in free sorting (more differentiation indicating higher salience). The unbiased haptics and haptically biased haptics groups were highly similar; both found the substance dimensions (hardness and texture) relatively salient. The haptics plus visual imagery group showed shape to be overwhelmingly salient, even more so when they were instructed to use two hands, but less so when they had just seen the objects. The haptics plus vision group showed salience to be more evenly distributed over the dimensions. Exploratory hand movements were videotaped and scored into four categories of exploratory procedure (I.,derman & Klatzky, 1987): lateral motion, pressure, contour following, and enclosure (related to texture, hardness, shape, and size, respectively). The distribution of exploratory procedures was found to be directly related to both the designated dimension in the directed-discrimination task, and the salient dimension in the free-sorting task. The results support our contention that the haptic and visual systems have distinct encoding pathways, with haptics oriented toward the encoding of substance rather than shape. This may reflect a direct influence of haptic exploratory procedures: The procedures that are executed under unbiased haptic encoding are those that are generally found to be rapid and accurate (high "ease of encoding"), and the execution of these procedures determines which object properties become salient.
TL;DR: Neurons in a subdivision of the pulvinar resemble those in parietal cortex: many respond to visual stimuli, some of these have a spatial selection mechanism, and some have signals about the occurrence of eye movements that suggest a role in visual spatial attention.
TL;DR: The shifter hypothesis is consistent with available anatomical and physiological evidence on the organization of the primate visual pathway, and it offers a sensible explanation for a variety of otherwise puzzling facts, such as the plethora of cells in the geniculorecipient layers of V1.
Abstract: We propose a general strategy for dynamic control of information flow between arrays of neurons at different levels of the visual pathway, starting in the lateral geniculate nucleus and the geniculorecipient layers of cortical area V1. This strategy can be used for resolving computational problems arising in the domains of stereopsis, directed visual attention, and the perception of moving images. In each of these situations, some means of dynamically controlling how retinal outputs map onto higher-level targets is desirable--in order to achieve binocular fusion, to allow shifts of the focus of attention, and to prevent blurring of moving images. The proposed solution involves what we term "shifter circuits," which allow for dynamic shifts in the relative alignment of input and output arrays without loss of local spatial relationships. The shifts are produced in increments along a succession of relay stages that are linked by diverging excitatory inputs. The direction of shift is controlled at each stage by inhibitory neurons that selectively suppress appropriate sets of ascending inputs. The shifter hypothesis is consistent with available anatomical and physiological evidence on the organization of the primate visual pathway, and it offers a sensible explanation for a variety of otherwise puzzling facts, such as the plethora of cells in the geniculorecipient layers of V1.
TL;DR: Investigation of the visually allocated "beam" studied by Posner and others showed that orienting attention in response to central cues showed similar effects for both conjunction and feature search, but when attention was oriented with peripheral visual cues, conjunction search showed larger effects of attention than did feature search.
Abstract: In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. It is suggested that the attentional systems that are oriented in response to central and peripheral cues may not be the same and that only the latter performs a role in feature integration. Possibilities for future research are discussed. Language: en
TL;DR: Tests showed that opponent organization is not produced by differences in local directional properties in different parts of the receptive field, and how accurately the population response predicted radial stimulus direction by the application of a linear vector summation model was determined.
Abstract: Parietal visual neurons (PVNs) were studied in waking monkeys as they executed a simple fixation-detection task. Test visual stimuli of varied direction, speed, and extent were presented during the fixation period; these stimuli did not control behavior. Most PVNs subtend large, bilateral receptive fields and are exquisitely sensitive to stimulus motion and direction but insensitive to stimulus speed. The directional preferences of PVNs along meridians are opponently organized, with the preferred directions pointing either inward toward or outward away from the fixation point. Evidence presented in the preceding paper (Motter et al., 1987) indicates that opponent directionality along a single meridian is produced by a feed-forward inhibition of 20 degrees-30 degrees spatial extent. The observations fit a double-Gaussian model of superimposed but unequal excitatory and inhibitory receptive fields: When the former is larger, inward directionality results; when smaller, outward directionality results. We examine here the distribution of the meridional directional preferences in the visual field. Tests showed that opponent organization is not produced by differences in local directional properties in different parts of the receptive field. The distribution of response intensities from one meridian to another is adequately described by a sine wave function. These data indicate a best radial direction for each neuron with a broad distribution of response intensities over successive meridians. Thus, any single PVN, with rare exceptions, cannot signal radial stimulus direction precisely. We then determined how accurately the population response predicted radial stimulus direction by the application of a linear vector summation model. The resulting population vector varied from stimulus direction by an average of 9 degrees. Whether or not the perception of the direction of motion depends upon a population vector remains uncertain. PVNs are especially sensitive to object movement in the visual surround, particularly in the periphery of the visual field. This, combined with their large receptive fields and their wide but flat sensitivity to stimulus speed, makes them especially sensitive to optic flow. This is discussed in relation to the role of the parietal visual system in the visual guidance of projected movements of the arm and hand, in the guidance of locomotion, and in evoking the illusion of vection.
TL;DR: Visual and auditory signals, originally encoded in retinal and head-centered coordinates, respectively, have undergone a transformation that allows them to share a common efferent pathway for the generation of saccadic eye movements.
Abstract: Orienting movements of the eyes and head are made to both auditory and visual stimuli even though in the primary sensory pathways the locations of auditory and visual stimuli are encoded in differe...
20 Jul 1987
TL;DR: In this article, the authors reviewed evidence that elementary operations of cognition as defined by cognitive studies are the level at which the brain localizes its computations, and the component facilitations and inhibitions in visual orienting are related to neural systems through the study of focal neurological lesions.
Abstract: : A principle problem of neuropsychology is to relate the neural structures damaged in traumatic brain injury with their functions in the cognitive tasks of daily life. This lecture reviews evidence that elementary operations of cognition as defined by cognitive studies are the level at which the brain localizes its computations. Orienting of visual attention is used as a model task. The component facilitations and inhibitions in visual orienting are related to neural systems through the study of focal neurological lesions. Visual orienting is a part of a more general selective attention system that also involves orienting to language. Our ability to be aware of and to act upon target events depends upon the connections of posterior orienting these pathways in studies of focal changes in cerebral blood flow during performance of language tasks. Although we do not have a general analysis of the mental operations performed by these anterior systems, there is some evidence relating the dorsolateral prefrontal and areas of the medial surface to aspects of focal selection. One way to study the generality of the attentional system developed in this lecture is to examine putative deficits of attention in disorders such as schizophrenia, depression and closed head injury where the organic basis for the deficit is largely unknown. Our preliminary studies of schizophrenia are used to support the utility of the joint functional and structural analysis proposed here.
TL;DR: Four experiments are reported in which the detectability of threshold probe gratings of different spatial frequencies was measured while subjects analyzed either the local or the global information from a display.
Abstract: Probe methods were used to investigate whether the distribution of attention to the local or the global structure of a stimulus affects the detectability of different spatial frequencies. Four experiments are reported in which the detectability of threshold probe gratings of different spatial frequencies was measured while subjects analyzed either the local or the global information from a display. A relative shift in the detectability of low and high frequencies was observed. Low frequencies were facilitated during global processing and/or high frequencies were facilitated during local processing.
TL;DR: In this article, a series of three experiments was designed to determine if this effect of prior experience depends on preserving the visual details of a word between its prior presentation and test, and they found evidence of specific visual transfer only for words that were tested in lowercase.
Abstract: Prior presentation of a word can serve to enhance its later perceptual identification. A series of three experiments was designed to determine if this effect of prior experience depends on preserving the visual details of a word between its prior presentation and test. A first experiment revealed evidence of specific visual transfer only for words that were tested in lowercase. Words tested in lowercase that had been previously presented in lowercase were more readily identified than were those that had been previously presented in uppercase. Later experiments used more extreme manipulations of the visual details of a word in an attempt to maximize specific visual transfer. Results of the experiments are discussed in terms of the role of memory for visual details in word identification along with the possibility that perception can rely on memory for prior episodes.
TL;DR: The authors' data point to an approximate correspondence between orientation and spatial frequency discrimination "thresholds" determined behaviorally and those estimated from the most selective single cortical cells, which is considered in the discussion.
Abstract: Neurons in the visual cortex respond selectively to stimulus orientation and spatial frequency. Changes in response amplitudes of these neurons could be the neurophysiological basis of orientation ...
TL;DR: The results suggest that auditory deprivation and the acquisition of a visual language have marked and different effects on the development of cortical specializations in humans.
TL;DR: It appears that dyslexic persons learn to read outside the foveal field and, more generally, that there are different learned strategies for task-directed vision.
Abstract: We compared persons with dyslexia and normal readers with respect to how well they identified letters and short strings of letters briefly presented in the peripheral visual field at the same time that a single letter was presented at the fixation point of gaze. We found that the dyslexic subjects had a markedly wider area in which correct identification occurred in the peripheral field than did the normal readers. However, the dyslexie subjects had a "masking" between letters in the foveal field and letters in the near periphery. It appears that dyslexic persons learn to read outside the foveal field and, more generally, that there are different learned strategies for task-directed vision. Among such strategies are different mutual interactions between foveal and peripheral vision. (N Engl J Med 1987; 316: 1238–43.)
01 Jan 1987
TL;DR: Evidence is given that image analysis times on the order of a second or less can be obtained for typical industrial recognition tasks, without restriction on the orientation of the object in space.
Abstract: A method for the automatic construction of fast special purpose vision programs is described. The starting point for the automatic construction process is a description of a particular 3D object. The result is a fast special purpose program for recognizing and locating that object in images, without restriction on the orientation of the object in space. The method has been implemented and tested on a variety of images with good results. Some of the tests involved images in which the target objects appear in a jumbled pile. The current implementation is not fully optimized for speed. However, evidence is given that image analysis times on the order of a second or less can be obtained for typical industrial recognition tasks. (This time estimate excludes edge finding).
TL;DR: The increase of thresholds in peripheral vision was larger than predicted by the theory in the Landolt visual acuity and bisection hyperacuity tests, possibly because of retinal undersampling.
Abstract: In a generalized form, the cortical magnification theory of peripheral vision predicts that the thresholds of any visual stimuli are similar across the whole visual field if the cortical stimulus representations calculated by means of the cortical magnification factor are similar independently of eccentricity. Failures of the theory in spatial vision were analyzed, and the theory was tested with five visual acuity tasks and two hyperacuity tasks. Almost all increases in thresholds with eccentricity were explained by the theory in five of these tasks, which included the two-dot vernier hyperacuity test, the measurement of visual acuities with gratings, the Snellen E test, and two acuity tests that required either separation between dots or discrimination between two mirror-symmetric forms. The two-dot vernier thresholds could be explained as a special case of orientation discrimination, and orientation discrimination at different eccentricities was in agreement with the cortical magnification theory. The increase of thresholds in peripheral vision was larger than predicted by the theory in the Landolt visual acuity and bisection hyperacuity tests, possibly because of retinal undersampling.
TL;DR: Results showed that adults and good readers were able to direct attention effectively when given a cue that correctly predicted the location of the target letter, whereas poor readers were not.
Abstract: Twelve children, who were classified as good or poor readers, and 4 adults were given a task used to measure the ability to direct attention across visual space. Accuracy in detecting briefly presented target letters (S or N) was measured as a function of whether a cue did or did not correctly predict target location. Results showed that adults and good readers were able to direct attention effectively when given a cue that correctly predicted the location of the target letter, whereas poor readers were not. Poor readers also produced lower accuracy rates when the cue preceded the target by 100 msec or less, but demonstrated equal accuracy when the asynchrony between cue and target was 150 msec or more. Right-visual-field enhancement was found in adults and good readers, but not in poor readers. These results are discussed within the framework of current theories of reading disability.
TL;DR: The presence of cross-modal interference indicates that subjects could not prevent the processing of irrelevant, spoken color words and is used to support a description of processing in which multiple verbal items enter a prespeech buffer and a selection mechanism examines buffer items in parallel.
Abstract: This study examines effects of auditory color-word interference on a visual Stroop task with a spoken response. The presence of cross-modal interference indicates that subjects could not prevent the processing of irrelevant, spoken color words. Additional aspects of the results (e.g., lack of effects from noncolor items and additivity of auditory and visual interference) are used to support a description of processing in which multiple verbal items enter a prespeech buffer and a selection mechanism examines buffer items in parallel.
TL;DR: It is proposed that the primitive mechanism for the separation of stationary objects relies on their relative movement against a background, normally caused by the animal’s own movement.
Abstract: This paper is concerned with the evolution of visual mechanisms and the possibility of copying their principles at different levels of sophistication. It is an old question how the complex interaction between eye and brain evolved when each needs the other as a test-bed for successive improvements. I propose that the primitive mechanism for the separation of stationary objects relies on their relative movement against a background, normally caused by the animal's own movement. Apparently insects and many lower animals use little more than this for negotiating through a three-dimensional world, making adequate responses to individual objects which they 'see' without a cortical system or even without a large brain. In the development of higher animals such as birds or man, additional circuits store memories of the forms of objects that have been frequently inspected from all angles or handled. Simple visual systems, however, are tuned to a feature of the world by which objects separate themselves by movement relative to the eye. In making simple artificial visual systems which 'see', as distinct from merely projecting the image, it is more hopeful to copy the 'ambient' vision of lower animals than the cortical systems of birds or mammals.
TL;DR: Visual stabilisation of body sway in a patient with severe deficits of the vestibular system and the somatosensory system was studied and provides clinical evidence for rapid visuo-spinal control of posture.
Abstract: Visual stabilisation of body sway in a patient with severe deficits of the vestibular system (due to gentamicin treatment) and the somatosensory system (due to polyneuropathy) was studied. With eyes open the patient was able to stand and walk slowly. With eyes closed he lost balance within one second. In order to optimise visual stabilisation he intuitively searched for nearby visual targets. His postural sway was recorded using posturography. His balance performance deteriorated significantly beyond a distance of 1 m between the eyes and the surrounding objects and with visual acuity below 0.3 (experimentally achieved with semitransparent plastic foils). With flicker illumination of decreasing frequencies of the visual surround he needed at least a visual input rate of 17 Hz in order to maintain an upright body position. The data provide clinical evidence for rapid visuo-spinal control of posture.