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A selective impairment of motion perception following lesions of the middle temporal visual area (MT)
- JOURNAL OF NEUROSCIENCE
, 1988
"... Physiological experiments indicate that the middle temporal visual area (MT) of primates plays a prominent role in the cortical analysis of visual motion. We investigated the role of MT in visual perception by examining the effect of chemical lesions of MT on psychophysical thresholds. We trained rh ..."
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Cited by 202 (5 self)
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Physiological experiments indicate that the middle temporal visual area (MT) of primates plays a prominent role in the cortical analysis of visual motion. We investigated the role of MT in visual perception by examining the effect of chemical lesions of MT on psychophysical thresholds. We trained rhesus monkeys on psychophysical tasks that enabled us to assess their sensitivity to motion and to contrast. For motion psychophysics, we employed a dynamic random dot display that permitted us to vary the intensity of a motion signal in the midst of masking motion noise. We measured the threshold intensity for which the monkey could successfully complete a direction discrimination. In the contrast task, we measured the threshold contrast for which the monkeys could successfully discriminate the orientation of stationary gratings. Injections of ibotenic acid into MT caused striking elevations in motion thresholds, but had little or no effect on contrast thresholds. The results indicate that neural activity in MT contributes selectively to the perception of motion.
The Link Between Brain Learning, Attention, And Consciousness
, 1998
"... The processes whereby our brains continue to learn about a changing world in a stable fashion throughout life are proposed to lead to conscious experiences. These processes include the learning of top-down expectations, the matching of these expectations against bottom-up data, the focusing of atten ..."
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Cited by 134 (39 self)
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The processes whereby our brains continue to learn about a changing world in a stable fashion throughout life are proposed to lead to conscious experiences. These processes include the learning of top-down expectations, the matching of these expectations against bottom-up data, the focusing of attention upon the expected clusters of information, and the development of resonant states between bottom-up and top-down processes as they reach an attentive consensus between what is expected and what is there in the outside world. It is suggested that all conscious states in the brain are resonant states, and that these resonant states trigger learning of sensory and cognitive representations. The models which summarize these concepts are therefore called Adaptive Resonance Theory, or ART, models. Psychophysical and neurobiological data in support of ART are presented from early vision, visual object recognition, auditory streaming, variable-rate speech perception, somatosensory perception, a...
Segregation of form, color and stereopsis in primate area 18
- J. Neurosci
, 1987
"... for the enzyme cytochrome oxidase, shows a pattern of alternating dark and light stripes; in squirrel monkeys, the dark stripes are clearly of 2 alternating types, thick and thin. We have recorded from these 3 subdivisions in macaques and squirrel monkeys, and find that each has distinctive physiolo ..."
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Cited by 95 (1 self)
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for the enzyme cytochrome oxidase, shows a pattern of alternating dark and light stripes; in squirrel monkeys, the dark stripes are clearly of 2 alternating types, thick and thin. We have recorded from these 3 subdivisions in macaques and squirrel monkeys, and find that each has distinctive physiological properties: (1) Cells in one set of dark stripes, in squirrel monkeys the thin stripes, are not orientation-selective; a high proportion show color-opponency. (2) Cells in the other set of dark stripes (thick stripes) are orientationselective; most of them are also selective for binocular disparity, suggesting that they are concerned with stereoscopic depth. (3) Cells in the pale stripes are also orientation-selective and more than half of them are end-stopped. Each of the 3 subdivisions receives a different input from area 17: the thin stripes from the blobs, the pale stripes from
Independent component analysis applied to feature extraction from colour and stereo images
- Network Computation in Neural Systems
, 2000
"... Previous work has shown that independent component analysis (ICA) applied to feature extraction from natural image data yields features resembling Gabor functions and simple-cell receptive fields. This article considers the effects of including chromatic and stereo information. The inclusion of colo ..."
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Cited by 77 (5 self)
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Previous work has shown that independent component analysis (ICA) applied to feature extraction from natural image data yields features resembling Gabor functions and simple-cell receptive fields. This article considers the effects of including chromatic and stereo information. The inclusion of colour leads to features divided into separate red/green, blue/yellow, and bright/dark channels. Stereo image data, on the other hand, leads to binocular receptive fields which are tuned to various disparities. The similarities between these results and observed properties of simple cells in primary visual cortex are further evidence for the hypothesis that visual cortical neurons perform some type of redundancy reduction, which was one of the original motivations for ICA in the first place. In addition, ICA provides a principled method for feature extraction from colour and stereo images; such features could be used in image processing operations such as denoising and compression, as well as in pattern recognition.
Cortical dynamics of three-dimensional figure-ground perception of two-dimensional pictures
- PSYCHOLOGICAL REVIEW
, 1997
"... This article develops the FACADE theory of 3-dimensional (3-D) vision and figure-ground separation to explain data concerning how 2-dimensional pictures give rise to 3-D percepts of occluding and occluded objects. The model describes how geometrical and contrastive properties of a picture can either ..."
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Cited by 67 (32 self)
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This article develops the FACADE theory of 3-dimensional (3-D) vision and figure-ground separation to explain data concerning how 2-dimensional pictures give rise to 3-D percepts of occluding and occluded objects. The model describes how geometrical and contrastive properties of a picture can either cooperate or compete when fonning the boundaries and surface representations that subserve conscious percepts. Spatially long-range cooperation and spatially short-range competition work together to separate the boundaries of occluding figures from their occluded neighbors. This boundary ownership process is sensitive to image T junctions at which occluded figures contact occluding figures. These boundaries control the filling-in of color within multiple depth-sensitive surface representations. Feedback between surface and boundary representations strengthens consistent boundaries while inhibiting inconsistent ones. Both the boundary and the surface representations of occluded objects may be amodally completed, while the surface representations of unoccluded objects become visible through modal completion. Functional roles for conscious modal and amodal representations in object recognition, spatial attention, and reaching behaviors are discussed. Model interactions are interpreted in tenns of visual, temporal, and parietal cortices.
Tho’ she kneel’d in that place where they grew.’ The uses and origins of primate colour vision
- J. Exp. Biol
, 1989
"... The disabilities experienced by colour-blind people show us the biological advantages of colour vision in detecting targets, in segregating the visual field and in identifying particular objects or states. Human dichromats have especial difficulty in detecting coloured fruit against dappled foliage ..."
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Cited by 64 (7 self)
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The disabilities experienced by colour-blind people show us the biological advantages of colour vision in detecting targets, in segregating the visual field and in identifying particular objects or states. Human dichromats have especial difficulty in detecting coloured fruit against dappled foliage that varies randomly in luminosity; it is suggested that yellow and orange tropical fruits have co-evolved with the trichromatic colour vision of Old World monkeys. It is argued that the colour vision of man and of the Old World monkeys depends on two subsystems that remain parallel and independent at early stages of the visual pathway. The primordial subsystem, which is shared with most mammals, depends on a comparison of the rates of quantum catch in the short- and middle-wave cones; this system exists almost exclusively for colour vision, although the chromatic signals carry with them a local sign that allows them to sustain several of the functions of spatiochromatic vision. The second subsystem arose from the phylogenetically recent duplication of a gene on the X-cnromosome, and depends on a comparison of the rates of quantum catch in the long- and middle-wave receptors. At the early stages of the visual pathway, this chromatic information is carried by a channel that is also sensitive to spatial contrast. The New World monkeys have taken a different route to trichromacy: in species that are basically dichromatic, heterozygous females gain trichromacy as a result of X-chromosome inactivation, which ensures that different photopigments are expressed in two subsets of retinal photoreceptor.
Pre-Attentive Segmentation in the Primary Visual Cortex
, 1998
"... Stimuli outside classical receptive fields have been shown to exert significant influence over the activities of neurons in primary visual cortex. We propose that contextual influences are used for pre-attentive visual segmentation, in a new framework called segmentation without classification. T ..."
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Cited by 62 (0 self)
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Stimuli outside classical receptive fields have been shown to exert significant influence over the activities of neurons in primary visual cortex. We propose that contextual influences are used for pre-attentive visual segmentation, in a new framework called segmentation without classification. This means that segmentation of an image into regions occurs without classification of features within a region or comparison of features between regions.
How Does the Cerebral Cortex Work? Development, Learning, Attention, and 3d Vision by the Laminar Circuits of Visual Cortex
- BEHAVIORAL AND COGNITIVE NEUROSCIENCE REVIEWS
, 2003
"... A key goal of behavioral and cognitive neuroscience is to link brain mechanisms to behavioral functions. The present article describes recent progress towards explaining how the visual cortex sees. Visual cortex, like many parts of perceptual and cognitive neocortex, is organized into six main layer ..."
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Cited by 58 (34 self)
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A key goal of behavioral and cognitive neuroscience is to link brain mechanisms to behavioral functions. The present article describes recent progress towards explaining how the visual cortex sees. Visual cortex, like many parts of perceptual and cognitive neocortex, is organized into six main layers of cells, as well as characteristic sub-lamina. Here it is proposed how these layered circuits help to realize processes of development, learning, perceptual grouping, attention, and 3D vision through a combination of bottom-up, horizontal, and top-down interactions. A key theme is that the mechanisms which enable development and learning to occur in a stable way imply properties of adult behavior. These results thus begin to unify three fields: infant cortical development, adult cortical neurophysiology and anatomy, and adult visual perception. The identified cortical mechanisms promise to generalize to explain how other perceptual and cognitive processes work.
A Neural Model Of High-Level Motion Processing: Line Motion And Formotion Dynamics
, 1996
"... The percepts known variously as the line motion illusion, motion induction, and transformational apparent motion have attracted a great deal of experimental interest, since they sensitively probe interactions between preattentive and attentive vision processes. The present article develops a neural ..."
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Cited by 43 (28 self)
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The percepts known variously as the line motion illusion, motion induction, and transformational apparent motion have attracted a great deal of experimental interest, since they sensitively probe interactions between preattentive and attentive vision processes. The present article develops a neural model that qualitatively explains essentially all the data reported thus far, and quantitatively simulates key illustrative percepts. The model suggests how these data arise from neural mechanisms of preattentive boundary and surface formation, long-range apparent motion, formmotion interactions, and spatial attention. The boundary and surface formation processes model aspects of the interblob V1 ! interstripe V2 ! V4 and blob V1 ! thin stripe V2 ! V4 cortical processing streams, respectively. The long-range apparent motion process models aspects of the V1 ! MT ! MST processing stream. An interstream V2 ! MT form-motion interaction is proposed to allow the motion processing stream to track ...
