Showing papers on "Visual perception published in 2002"
TL;DR: In this paper, a biologically motivated computational model of bottom-up visual selective attention was used to examine the degree to which stimulus salience guides the allocation of attention in human eye movements while participants viewed a series of digitized images of complex natural and artificial scenes.
1,417 citations
TL;DR: Of regions in the extended system for face perception, the amygdala plays a central role in processing the social relevance of information gleaned from faces, particularly when that information may signal a potential threat.
1,224 citations
TL;DR: This study examined the timing and topography of cortical auditory-visual interactions using high-density event-related potentials (ERPs) during a simple reaction-time (RT) task, providing compelling evidence that auditory- visual neural interactions give rise to this RT effect.
871 citations
TL;DR: It is reported that subjects can rapidly detect animals or vehicles in briefly presented novel natural scenes while simultaneously performing another attentionally demanding task, and some visual tasks associated with “high-level” cortical areas may proceed in the near absence of attention.
Abstract: attention appear to be carried out in the early stages of the visual system. Contrary to this common belief, we report that subjects can rapidly detect animals or vehicles in briefly presented novel natural scenes while simultaneously performing another attentionally demanding task. By comparison, they are unable to discriminate large T's from L's, or bisected two-color disks from their mirror images under the same conditions. We conclude that some visual tasks associated with ''high-level'' cortical areas may proceed in the near absence of attention.
747 citations
TL;DR: Responses were faster when the pictured object's shape matched the shape implied by the sentence than when there was a mismatch, supporting the hypothesis that perceptual symbols are routinely activated in language comprehension.
Abstract: We examined the prediction that people activate perceptual symbols during language comprehension. Subjects read sentences describing an animal or object in a certain location. The shape of the object or animal changed as a function of its location (e.g., eagle in the sky, eagle in a nest). However, this change was only implied by the sentences. After reading a sentence, subjects were presented with a line drawing of the object in question. They judged whether the object had been mentioned in the sentence (Experiment 1) or simply named the object (Experiment 2). In both cases, responses were faster when the pictured object's shape matched the shape implied by the sentence than when there was a mismatch. These results support the hypothesis that perceptual symbols are routinely activated in language comprehension.
703 citations
TL;DR: It is reported that the occipital and fusiform face areas (OFA and FFA) also contain neural signals capable of differentiating biological from nonbiological motion.
666 citations
TL;DR: This paper found that neurons in the lateral prefrontal cortex were tuned for quantity irrespective of the exact physical appearance of the displays, which may explain why behavioral discrimination improves with increasing numerical distance and why discrimination of two quantities with equal numerical distance worsens as their numerical size increases.
Abstract: Deriving the quantity of items is an abstract form of categorization. To explore it, monkeys were trained to judge whether successive visual displays contained the same quantity of items. Many neurons in the lateral prefrontal cortex were tuned for quantity irrespective of the exact physical appearance of the displays. Their tuning curves formed overlapping filters, which may explain why behavioral discrimination improves with increasing numerical distance and why discrimination of two quantities with equal numerical distance worsens as their numerical size increases. A mechanism that extracts the quantity of visual field items could contribute to general numerical ability.
624 citations
TL;DR: This work presents the first cross-modal modification of visual perception which involves a phenomenological change in the quality-as opposed to a small, gradual, or quantitative change-of the percept of a non-ambiguous visual stimulus.
584 citations
TL;DR: It is shown that, as predicted by this model, the visual-proprioceptive integration varies with direction, and this results provide evidence for statistically optimal integration of information from multiple modalities.
559 citations
TL;DR: This work shows that feature selectivity in the macaque inferior temporal cortex is shaped by categorization of objects on the basis of their visual features, and finds enhanced neuronal representation of the diagnostic features relative to the non-diagnostic ones.
Abstract: The way that we perceive and interact with objects depends on our previous experience with them. For example, a bird expert is more likely to recognize a bird as a sparrow, a sandpiper or a cockatiel than a non-expert. Neurons in the inferior temporal cortex have been shown to be important in the representation of visual objects; however, it is unknown which object features are represented and how these representations are affected by categorization training. Here we show that feature selectivity in the macaque inferior temporal cortex is shaped by categorization of objects on the basis of their visual features. Specifically, we recorded from single neurons while monkeys performed a categorization task with two sets of parametric stimuli. Each stimulus set consisted of four varying features, but only two of the four were important for the categorization task (diagnostic features). We found enhanced neuronal representation of the diagnostic features relative to the non-diagnostic ones. These findings demonstrate that stimulus features important for categorization are instantiated in the activity of single units (neurons) in the primate inferior temporal cortex
559 citations
01 Jul 2002
TL;DR: This work describes a computational approach to stylizing and abstracting photographs that explicitly responds to the design goal of good information design and represents a new alternative for non-photorealistic rendering both in its visual style, in its approach to visual form, and in its techniques for interaction.
Abstract: Good information design depends on clarifying the meaningful structure in an image. We describe a computational approach to stylizing and abstracting photographs that explicitly responds to this design goal. Our system transforms images into a line-drawing style using bold edges and large regions of constant color. To do this, it represents images as a hierarchical structure of parts and boundaries computed using state-of-the-art computer vision. Our system identifies the meaningful elements of this structure using a model of human perception and a record of a user's eye movements in looking at the photo; the system renders a new image using transformations that preserve and highlight these visual elements. Our method thus represents a new alternative for non-photorealistic rendering both in its visual style, in its approach to visual form, and in its techniques for interaction.
TL;DR: In this paper, a model of scene perception and long-term memory was proposed, which showed that relatively detailed visual information is retained in memory from previously attended objects in natural scenes and that participants successfully detected type and token changes (Experiment 1) or token and rotation changes to a target object when the object had been previously attended but was no longer within the focus of attention when the change occurred.
Abstract: The nature of the information retained from previously fixated (and hence attended) objects in natural scenes was investigated. In a saccade-contingent change paradigm, participants successfully detected type and token changes (Experiment 1) or token and rotation changes (Experiment 2) to a target object when the object had been previously attended but was no longer within the focus of attention when the change occurred. In addition, participants demonstrated accurate type-, token-, and orientationdiscrimination performance on subsequent long-term memory tests (Experiments 1 and 2) and during online perceptual processing of a scene (Experiment 3). These data suggest that relatively detailed visual information is retained in memory from previously attended objects in natural scenes. A model of scene perception and long-term memory is proposed. Because of the size and complexity of the visual environments humans tend to inhabit, and because high-acuity vision is limited to a relatively small area of the visual field, detailed perceptual processing of a natural scene depends on the selection of local scene regions by movements of the eyes (for reviews, see Henderson & Hollingworth, 1998, 1999a). During scene viewing, the eyes are reoriented approximately three times each second by saccadic eye movements to bring the projection of a local scene region (typically a discrete object) onto the area of the retina producing the highest acuity vision (the fovea). The periods between saccades, when the eyes are relatively stationary and detailed visual information is encoded, are termed fixations and last an average of approximately 300 ms during scene viewing. During each brief saccadic eye movement, however, visual encoding is suppressed (Matin, 1974). Thus, the visual system is provided with what amounts to a series of snapshots (corresponding to fixations), which may vary dramatically in their visual content over a complex scene, punctuated by brief periods of blindness (corresponding to saccades).
Book•
10 Jan 2002TL;DR: A computational approach to the neuropsychology of visual attention using neural network models and models of invariant object recognition as a model for this purpose is suggested.
Abstract: PREFACE 1. Introduction 2. The primary visual cortex 3. Extrastriate visual areas 4. The parietal cortex 5. Inferior temporal cortical visual areas 6. Visual attentional mechanisms 7. Neural network models 8. Models of invariant object recognition 9. The cortical neurodynamics of visual attention - a model 10. Visual search: Attentional neurodynamics at work 11. A computational approach to the neuropsychology of visual attention 12. Outputs of visual processing 13. Principles and conclusions INTRODUCTION TO LINEAR ALGEBRA FOR NEURAL NETWORKS INFORMATION THEORY References Index
TL;DR: Results of two fMRI experiments show that dissociable subsystems in ventral visual cortex maintain distinct view-dependent and view-invariant object representations.
Abstract: We conducted two event-related functional magnetic resonance imaging (fMRI) experiments to investigate the neural substrates of visual object recognition in humans. We used a repetition-priming method with visual stimuli recurring at unpredictable intervals, either with the same appearance or with changes in size, viewpoint or exemplar. Lateral occipital and posterior inferior temporal cortex showed lower activity for repetitions of both real and non-sense objects; fusiform and left inferior frontal regions showed decreases for repetitions of only real objects. Repetition of different exemplars with the same name affected only the left inferior frontal cortex. Crucially, priming-induced decreases in activity of the right fusiform cortex depended on whether the three-dimensional objects were repeated with the same viewpoint, regardless of whether retinal image size changed; left fusiform decreases were independent of both viewpoint and size. These data show that dissociable subsystems in ventral visual cortex maintain distinct view-dependent and view-invariant object representations.
TL;DR: Functional MRI is used to measure activity in a higher object processing area, the lateral occipital complex, and in primary visual cortex in response to visual elements that were either grouped into objects or randomly arranged, suggesting that activity in early visual areas is reduced as a result of grouping processes performed in higher areas.
Abstract: Visual perception involves the grouping of individual elements into coherent patterns that reduce the descriptive complexity of a visual scene. The physiological basis of this perceptual simplification remains poorly understood. We used functional MRI to measure activity in a higher object processing area, the lateral occipital complex, and in primary visual cortex in response to visual elements that were either grouped into objects or randomly arranged. We observed significant activity increases in the lateral occipital complex and concurrent reductions of activity in primary visual cortex when elements formed coherent shapes, suggesting that activity in early visual areas is reduced as a result of grouping processes performed in higher areas. These findings are consistent with predictive coding models of vision that postulate that inferences of high-level areas are subtracted from incoming sensory information in lower areas through cortical feedback.
TL;DR: The main result of this study was that the perception of objects, irrespective of the task (judgement of the vertical orientation, motor imagery, and silent generation of the noun or of the corresponding action verb), versus perception of non-objects, was associated with rCBF increases in a common set of cortical regions.
TL;DR: It is reported that single-cue information is indeed lost when cues from within the same sensory modality (disparity and texture gradients in vision) are combined, but not when different modalities (vision and haptics) are Combined.
Abstract: Humans use multiple sources of sensory information to estimate environmental properties. For example, the eyes and hands both provide relevant information about an object's shape. The eyes estimate shape using binocular disparity, perspective projection, etc. The hands supply haptic shape information by means of tactile and proprioceptive cues. Combining information across cues can improve estimation of object properties but may come at a cost: loss of single-cue information. We report that single-cue information is indeed lost when cues from within the same sensory modality (disparity and texture gradients in vision) are combined, but not when different modalities (vision and haptics) are combined.
TL;DR: An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a rather clear spatial and temporal rule, governing multisensory integration at the neuronal level.
Abstract: Neurophysiological studies have shown in animals that a sudden sound enhanced perceptual processing of subsequent visual stimuli. In the present study, we explored the possibility that such enhancement also exists in humans and can be explained through crossmodal integration effects, whereby the interaction occurs at the level of bimodal neurons. Subjects were required to detect visual stimuli in a unimodal visual condition or in crossmodal audio-visual conditions. The spatial and the temporal proximity of multisensory stimuli were systematically varied. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a rather clear spatial and temporal rule, governing multisensory integration at the neuronal level.
TL;DR: It is suggested that LOtv, the cortical region LOtv for the lateral occipital tactile-visual region, is involved in recovering the geometrical shape of objects.
Abstract: We have recently demonstrated using fMRI that a region within the human lateral occipital complex (LOC) is activated by objects when either seen or touched. We term this cortical region LOtv for the lateral occipital tactile-visual region. We report here that LOtv voxels tend to be located in sub-regions of LOC that show preference for graspable visual objects over faces or houses. We further examine the nature of object representation in LOtv by studying its response to stimuli in three modalities: auditory, somatosensory and visual. If objects activate LOtv, irrespective of the modality used, the activation is likely to reflect a highly abstract representation. In contrast, activation specific to vision and touch may reflect common and exclusive attributes shared by these senses. We show here that while object activation is robust in both the visual and the somatosensory modalities, auditory signals do not evoke substantial responses in this region. The lack of auditory activation in LOtv cannot be explained by differences in task performance or by an ineffective auditory stimulation. Unlike vision and touch, auditory information contributes little to the recovery of the precise shape of objects. We therefore suggest that LOtv is involved in recovering the geometrical shape of objects.
TL;DR: Using functional magnetic resonance imaging in humans, neural activity is measured 24 h after a single session of intensive monocular training on visual texture discrimination to provide a direct demonstration of learning-dependent reorganization at early processing stages in the visual cortex of adult humans.
Abstract: Visual texture discrimination has been shown to induce long-lasting behavioral improvement restricted to the trained eye and trained location in visual field [Karni, A. & Sagi, D. (1991) Proc. Natl. Acad. Sci. USA 88, 4966-4970]. We tested the hypothesis that such learning involves durable neural modifications at the earliest cortical stages of the visual system, where eye specificity, orientation, and location information are mapped with highest resolution. Using functional magnetic resonance imaging in humans, we measured neural activity 24 h after a single session of intensive monocular training on visual texture discrimination, performed in one visual quadrant. Within-subject comparisons between trained and untrained eye for targets presented within the same quadrant revealed higher activity in a corresponding retinotopic area of visual cortex. Functional connectivity analysis showed that these learning-dependent changes were not associated with an increased engagement of other brain areas remote from early visual cortex. We suggest that these new data are consistent with recent proposals that the cellular mechanisms underlying this type of perceptual learning may involve changes in local connections within primary visual cortex. Our findings provide a direct demonstration of learning-dependent reorganization at early processing stages in the visual cortex of adult humans.
TL;DR: This finding suggests that some individuals with autism may show impairments in low-level visual processing--specifically in the magnocellular visual pathway.
Abstract: Background: We assessed motion processing in a group of high functioning children with autism and a group of typically developing children, using a coherent motion detection task. Method: Twenty-five children with autism (mean age 11 years, 8 months) and 22 typically developing children matched for non-verbal mental ability and chronological age were required to detect the direction of moving dots in a random dot kinematogram. Results: The group of children with autism showed significantly higher motion coherence thresholds than the typically developing children (i.e., they showed an impaired ability to detect coherent motion). Conclusions: This finding suggests that some individuals with autism may show impairments in low-level visual processing - specifically in the magnocellular visual pathway. The findings are discussed in terms of implications for higher-level cognitive theories of autism, and the suggestion is made that more work needs to be carried out to further investigate low-level visual processing in autism.
TL;DR: For instance, this paper found that the percentage of time spent fixating a specific location during perception was highly correlated with the time spent on the same (empty) locations during imagery.
TL;DR: The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the age dependency of the reorganization is not fully known.
TL;DR: In this article, participants tapped their finger in synchrony with auditory and visual sequences containing an event onset shift (EOS), expected to elicit an involuntary phase correction response (PCR), and also tried to detect the EOS.
Abstract: Evidence that audition dominates vision in temporal processing has come from perceptual judgment tasks. This study shows that this auditory dominance extends to the largely subconscious processes involved in sensorimotor coordination. Participants tapped their finger in synchrony with auditory and visual sequences containing an event onset shift (EOS), expected to elicit an involuntary phase correction response (PCR), and also tried to detect the EOS. Sequences were presented in unimodal and bimodal conditions, including one in which auditory and visual EOSs of opposite sign coincided. Unimodal results showed greater variability of taps, smaller PCRs, and poorer EOS detection in vision than in audition. In bimodal conditions, variability of taps was similar to that for unimodal auditory sequences, and PCRs depended more on auditory than on visual information, even though attention was always focused on the visual sequences.
TL;DR: The results suggest differential effects of memory and attention during the generation and maintenance of mental images of faces during short- and long-term memory.
TL;DR: Investigation of how the nonclassical receptive field affects information transmission by V1 neurons during simulated natural vision in awake, behaving macaques demonstrates that the nCRF increases the sparseness of the stimulus representation in V1, suggesting that thenCRF tunes V 1 neurons to match the highly informative components of the natural world.
Abstract: We have investigated how the nonclassical receptive field (nCRF) affects information transmission by V1 neurons during simulated natural vision in awake, behaving macaques. Stimuli were centered over the classical receptive field (CRF) and stimulus size was varied from one to four times the diameter of the CRF. Stimulus movies reproduced the spatial and temporal stimulus dynamics of natural vision while maintaining constant CRF stimulation across all sizes. In individual neurons, stimulation of the nCRF significantly increases the information rate, the information per spike, and the efficiency of information transmission. Furthermore, the population averages of these quantities also increase significantly with nCRF stimulation. These data demonstrate that the nCRF increases the sparseness of the stimulus representation in V1, suggesting that the nCRF tunes V1 neurons to match the highly informative components of the natural world.
TL;DR: The results suggest that a specific action intention, such as grasping, can enhance visual processing of action-relevant features,such as orientation, and support the view that visual attention can be best understood as a selection-for-action mechanism.
Abstract: The influence of action intentions on visual selection processes was investigated in a visual search paradigm. A predefined target object with a certain orientation and color was presented among distractors, and subjects had to either look and point at the target or look at and grasp the target. Target selection processes prior to the first saccadic eye movement were modulated by the different action intentions. Specifically, fewer saccades to objects with the wrong orientation were made in the grasping condition than in the pointing condition, whereas the number of saccades to an object with the wrong color was the same in the two conditions. Saccadic latencies were similar under the different task conditions, so the results cannot be explained by a speed-accuracy trade-off. The results suggest that a specific action intention, such as grasping, can enhance visual processing of action-relevant features, such as orientation. Together the findings support the view that visual attention can be best understood as a selection-for-action mechanism.
TL;DR: The attentional modulation of sensory neurons reflects a subject's anticipation of the timing of behaviourally relevant events and is shown to reflect the allocation of attention over time.
Abstract: Paying attention to a stimulus selectively increases the ability to process it. For example, when subjects attend to a specific region of a visual scene, their sensitivity to changes at that location increases. A large number of studies describe the behavioural consequences and neurophysiological correlates of attending to spatial locations. There has, in contrast, been little study of the allocation of attention over time. Because subjects can anticipate predictable events with great temporal precision, it seems probable that they might dynamically shift their attention when performing a familiar perceptual task whose constraints changed over time. We trained monkeys to respond to a stimulus change where the probability of occurrence changed over time. Recording from area V4 of the visual cortex in these animals, we found that the modulation of neuronal responses changed according to the probability of the change occurring at that instant. Thus, we show that the attentional modulation of sensory neurons reflects a subject's anticipation of the timing of behaviourally relevant events.
TL;DR: The effects of eye gaze on basic aspects of the person-perception process, namely, person construal and the extraction of category-related knowledge from semantic memory, and the results supported these predictions.
Abstract: Previous research has highlighted the pivotal role played by gaze detection and interpretation in the development of social cognition. Extending work of this kind, the present research investigated the effects of eye gaze on basic aspects of the person-perception process, namely, person construal and the extraction of category-related knowledge from semantic memory. It was anticipated that gaze direction would moderate the efficiency of the mental operations through which these social-cognitive products are generated. Specifically, eye gaze was expected to influence both the speed with which targets could be categorized as men and women and the rate at which associated stereotypic material could be accessed from semantic memory. The results of two experiments supported these predictions: Targets with nondeviated (i.e., direct) eye gaze elicited facilitated categorical responses. The implications of these findings for recent treatments of person perception are considered.
TL;DR: Visual ERPs, but not tactile ERP, were affected by spatial attention when audition was relevant, indicating that touch can be decoupled from cross-modal attention when task-irrelevant, and implicating supramodal mechanisms in the control of spatial attention.
Abstract: Recent behavioral and event-related brain potential (ERP) studies have revealed cross-modal interactions in endogenous spatial attention between vision and audition, plus vision and touch. The present ERP study investigated whether these interactions reflect supramodal attentional control mechanisms, and whether similar cross-modal interactions also exist between audition and touch. Participants directed attention to the side indicated by a cue to detect infrequent auditory or tactile targets at the cued side. The relevant modality (audition or touch) was blocked. Attentional control processes were reflected in systematic ERP modulations elicited during cued shifts of attention. An anterior negativity contralateral to the cued side was followed by a contralateral positivity at posterior sites. These effects were similar whether the cue signaled which side was relevant for audition or for touch. They also resembled previously observed ERP modulations for shifts of visual attention, thus implicating supramodal mechanisms in the control of spatial attention. Following each cue, single auditory, tactile, or visual stimuli were presented at the cued or uncued side. Although stimuli in task-irrelevant modalities could be completely ignored, visual and auditory ERPs were nevertheless affected by spatial attention when touch was relevant, revealing cross-modal interactions. When audition was relevant, visual ERPs, but not tactile ERPs, were affected by spatial attention, indicating that touch can be decoupled from cross-modal attention when task-irrelevant.