Revisiting spatial vision: toward a unifying model

We report contrast detection, contrast increment, contrast masking, orientation discrimination, and spatial frequency discrimination thresholds for spatially localized stimuli at 4° of eccentricity. Our stimulus geometry emphasizes interactions among overlapping visual filters and differs from that used in previous threshold measurements, which also admits interactions among distant filters. We quantitatively account for all measurements by simulating a small population of overlapping visual filters interacting through divisive inhibition. We depart from previous models of this kind in the parameters of divisive inhibition and in using a statistically efficient decision stage based on Fisher information. The success of this unified account suggests that, contrary to Bowne [Vision Res. 30, 449 (1990)], spatial vision thresholds reflect a single level of processing, perhaps as early as primary visual cortex

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

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

Natural scenes upset the visual applecart

The effortless ease of everyday vision seems to contradict numerous findings on the limited capacity of visual attention. However, natural scenes appear to escape the stringent limitations of attention that apply to seemingly far simpler stimuli. This astonishing result will oblige us to rethink the nature of visual attention and its limited capacity

Visual Attention: Light Enters the Jungle

AbstractRecent 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

Reduzierung der Magnetbelastung permanentmagneterregter Synchronmaschinen im dreiphasigen Stoßkurzschluss

Die vorliegende Arbeit behandelt das Thema Reduzierung der Magnetbelastung permanentmagneterregter Synchronmaschinen im dreiphasigen Stoßkurzschluss. Es wird eine neue Methode in der Theorie und durch praktische Versuche untersucht, wie bei permanentmagneterregten Synchronmaschinen (PMSM) mit Oberflächenmagneten das magnetische Feld, das im Stoßkurzschluss die Magnete belastet, reduziert werden kann

Positive regulators of osteoclastogenesis and bone resorption in rheumatoid arthritis

Bone destruction is a frequent and clinically serious event in patients with rheumatoid arthritis (RA). Local joint destruction can cause joint instability and often necessitates reconstructive or replacement surgery. Moreover, inflammation-induced systemic bone loss is associated with an increased fracture risk. Bone resorption is a well-controlled process that is dependent on the differentiation of monocytes to bone-resorbing osteoclasts. Infiltrating as well as resident synovial cells, such as T cells, monocytes and synovial fibroblasts, have been identified as sources of osteoclast differentiation signals in RA patients. Pro-inflammatory cytokines are amongst the most important mechanisms driving this process. In particular, macrophage colony-stimulating factor, RANKL, TNF, IL-1 and IL-17 may play dominant roles in the pathogenesis of arthritis-associated bone loss. These cytokines activate different intracellular pathways to initiate osteoclast differentiation. Thus, over the past years several promising targets for the treatment of arthritic bone destruction have been defined