News and Events

Shape-from-shading is independent of visual attention and may be a 'texton'.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Spatial vision, Volume 7, Number 4, p.311–22 (1993)

URL:

http://www.ingentaconnect.com/content/vsp/spv/1993/00000007/00000004/art00006?token=00511964a17ce46557e442f20672176763f446a493e6d2a6c51687627504541676249266d656c9b85

Keywords:

Attention, Attention: physiology, Form Perception, Form Perception: physiology, Humans, Light, Ocular, Ocular: physiology, Psychophysics, Sensory Thresholds, Vision

Abstract:

Shading was used to generate the appearance of an obliquely illuminated surface with spherical indentations and protrusions. The "pop-out" of an apparent indentation among numerous apparent protrusions served as a psychophysical assay for shape-from-shading. Detectability of the pop-out varied with the direction of apparent illumination, a finding which is characteristic for shape-from-shading and which demonstrated the appropriateness of this assay. Observers were able to concurrently detect two shape-from-shading pop-outs in different parts of the display, demonstrating that shape-from-shading is a parallel process. In another experiment, visual attention was engaged by a letter discrimination task. Nevertheless, observers were able to detect a shape-from-shading pop-out concurrently in the unattended part of the display, suggesting that shape-from-shading is independent of visual attention. Thus, shape-from-shading shares some of the characteristics of Julesz' textural stimulus dimensions ('textons').

Targeting visual motion.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Nature neuroscience, Volume 3, Number 1, p.9–11 (2000)

URL:

http://www.nature.com/neuro/journal/v3/n1/full/nn0100\_9.html

Keywords:

Data Display, Humans, Motion Perception, Motion Perception: physiology, Observer Variation, Pattern Recognition, Photic Stimulation, Space Perception, Space Perception: physiology, Visual, Visual Cortex, Visual Cortex: physiology, Visual Perception, Visual Perception: physiology, Visual: physiology

Abstract:

A new stimulus display reveals that humans summate the motion energies of all components consistent with a single velocity, rather than optimizing sensitivity by ignoring noise.

The emperor has some clothes

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Nature neuroscience, Volume 3, Number 10, p.975 (2000)

URL:

http://www.nature.com/neuro/journal/v3/n10/full/nn1000\_975.html

Abstract:

The New Cognitive Neurosciences was a vast undertaking, the hefty fruit of about 180 contributors' labors. Just like its predecessor, the book surveys the field of cognitive neuroscience, which attempts to explain all aspects of mental life in terms of brain processes.

Vision and attention: the role of training.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Nature, Volume 393, Number 6684, p.424–5 (1998)

ISBN:

0028-0836 (Print)

URL:

http://www.nature.com/nature/journal/v393/n6684/abs/393424a0.html

Keywords:

Attention, Attention: physiology, Humans, Learning, Learning: physiology, Visual Perception, Visual Perception: physiology

Abstract:

What happens to visual experience in the absence of visual attention? Does lack of attention render us effectively blind1, or is there a significant residual experience2, 3, 4? Here I show that the surprising results of a recent study1 were due not to the novel way in which attention was controlled, but simply to the use of novice rather than expert observers. So the evidence remains strong that some aspects of visual experience are essentially independent of attention.

Vision: attending the invisible.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Current biology : CB, Cell Press, Volume 17, Number 6, p.R202–3 (2007)

ISBN:

0960-9822

URL:

http://linkinghub.elsevier.com/retrieve/pii/S0960982207008779

Keywords:

Attention, Awareness, Brain Mapping, Humans, Photic Stimulation, Visual Perception, Visual Perception: physiology

Abstract:

In everyday vision, attention and awareness are hand in glove and almost impossible to tell apart. Recent work has exploited more contrived situations that allow these psychologically defined processes to be dissociated, providing insights into their respective neurophysiological correlates.

Visual attention: light enters the jungle.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Current biology : CB, Volume 12, Number 17, p.R599–601 (2002)

URL:

http://www.cell.com/current-biology/abstract/S0960-9822(02)01103-X

Keywords:

Animals, Attention, Attention: physiology, Awareness, Awareness: physiology, Color Perception, Contrast Sensitivity, Contrast Sensitivity: physiology, Humans, Light, Magnetic Resonance Imaging, Reaction Time, Reaction Time: physiology, Sensory Thresholds, Visual Cortex, Visual Cortex: physiology

Abstract:

Recent studies focusing on basic visual attributes, such as luminance, colour and motion, are providing a starting point for investigating the relationship between perceptual and neural manifestations of attention.

Visual search among items of different salience: removal of visual attention mimics a lesion in extrastriate area V4.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

The Journal of neuroscience : the official journal of the Society for Neuroscience, Volume 14, Number 2, p.554–67 (1994)

URL:

http://www.jneurosci.org/content/14/2/554

Keywords:

Animals, Attention, Color Perception, Pattern Recognition, Primates, Time Factors, Visual, Visual Perception

Abstract:

In more than one respect, visual search for the most salient or the least salient item in a display are different kinds of visual tasks. The present work investigated whether this difference is primarily one of perceptual difficulty, or whether it is more fundamental and relates to visual attention. Display items of different salience were produced by varying either size, contrast, color saturation, or pattern. Perceptual masking was employed and, on average, mask onset was delayed longer in search for the least salient item than in search for the most salient item. As a result, the two types of visual search presented comparable perceptual difficulty, as judged by psychophysical measures of performance, effective stimulus contrast, and stability of decision criterion. To investigate the role of attention in the two types of search, observers attempted to carry out a letter discrimination and a search task concurrently. To discriminate the letters, observers had to direct visual attention at the center of the display and, thus, leave unattended the periphery, which contained target and distractors of the search task. In this situation, visual search for the least salient item was severely impaired while visual search for the most salient item was only moderately affected, demonstrating a fundamental difference with respect to visual attention. A qualitatively identical pattern of results was encountered by Schiller and Lee (1991), who used similar visual search tasks to assess the effect of a lesion in extrastriate area V4 of the macaque.

How a gap junction maintains its structure.

Publication Type:

Journal Article

Source:

Nature, Volume 310, Number 5975, p.316–8 (1984)

URL:

http://www.nature.com/nature/journal/v310/n5975/abs/310316a0.html

Keywords:

Animals, Biophysical Phenomena, Biophysics, Cell Membrane, Cell Membrane: ultrastructure, Electron, Freeze Fracturing, Intercellular Junctions, Intercellular Junctions: ultrastructure, Liver, Liver: ultrastructure, Macromolecular Substances, Membrane Proteins, Mice, Microscopy, Models, Molecular

Abstract:

<p>In gap junctions, identical membrane proteins are linked up in pairs (dyads) that bridge the extracellular space between two apposed cell membranes. Typically, several thousand of these dyads are aggregated in the plane of the membranes and form a junctional plaque with a distinct boundary. The question thus arises as to what maintains the dyads in an aggregated state. From a statistical mechanical analysis of the positions of dyads in a freeze-fracture electron micrograph, we report here that the aggregates are not maintained by an attractive force between pairs of dyads, but probably by the minimization of the repulsive force between apposed membranes. On the basis of this analysis we present a model for the structure of mature gap junctions as well as certain aspects of the formation and disassembly of gap junctions.</p>

Lateral interactions among membrane proteins. Valid estimates based on freeze-fracture electron microscopy.

Publication Type:

Journal Article

Source:

Biophysical journal, Volume 52, Number 3, p.427–39 (1987)

URL:

http://www.cell.com/biophysj/abstract/S0006-3495(87)83232-0

Keywords:

Algorithms, Electron, Freeze Fracturing, Membrane Proteins, Membrane Proteins: metabolism, Microscopy, Models, Protein Conformation, Theoretical

Abstract:

We consider the lateral distribution of intrinsic membrane proteins from the viewpoint of the statistical-mechanical theory of liquids. We connect the information in freeze-fracture electron micrographs–positions of proteins but not lipids or aqueous species–to a well developed theory of liquid mixtures. An algorithm, based on the Born-Green-Yvon integral equation, is presented for deducing forces between proteins from correlations among protein positions that are observed in micrographs. The algorithm is tested on simulated micrographs, obtained by Monte-Carlo methods, where forces between proteins are known analytically. We conclude that valid estimates of such forces, both attractions and repulsions, can be obtained from the positions of a few thousand proteins.

Withdrawing attention at little or no cost: detection and discrimination tasks.

Publication Type:

Journal Article

Source:

Perception & psychophysics, Volume 60, Number 1, p.1–23 (1998)

ISBN:

0031-5117 (Print)

URL:

http://www.springerlink.com/content/4818q04256186556/

Keywords:

Adult, Attention, Awareness, Color Perception, Discrimination Learning, Female, Humans, Male, Orientation, Pattern Recognition, Psychophysics, Visual

Abstract:

We used a concurrent-task paradigm to investigate the attentional cost of simple visual tasks. As in earlier studies, we found that detecting a unique orientation in an array of oriented elements ("pop-out") carries little or no attentional cost. Surprisingly, this is true at all levels of performance and holds even when pop-out is barely discriminable. We discuss this finding in the context of our previous report that the attentional cost of stimulus detection is strongly influenced by the presence and nature of other stimuli in the display (Braun, 1994b). For discrimination tasks, we obtained a similarly mixed outcome: Discrimination of letter shape carried a high attentional cost whereas discrimination of color and orientation did not. Taken together, these findings lead us to modify our earlier position on the attentional costs of detection and discrimination tasks (Sagi & Julesz, 1985). We now believe that observers enjoy a significant degree of "ambient" visual awareness outside the focus of attention, permitting them to both detect and discriminate certain visual information. We hypothesize that the information in question is selected by a competition for saliency at the level of early vision.

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