bluuebunny/crossref_metadata_2025_split huggingface dataset:
The calcium ionophore A23187 induces endothelium‐dependent contractions in femoral arteries from rats with streptozotocin‐induced diabetes
Authors: Shi Y , Feletou M , Ku D D , Man R Y K , Vanhoutte P M 
Published: January 2007

Background and purpose:To study the importance of endothelium‐derived contracting factors (EDCFs) in arteries of rats with type I diabetes.Experimental approach:Rat femoral arteries were collected four or twelve weeks after induction of diabetes with streptozotocin. Rings, with or without endothelium, were suspended in organ chambers for isometric tension measurement. COX protein levels were determined by Western blotting.Key results:Four weeks after the injection of streptozotocin, the endothelium‐dependent relaxations (during contractions to phenylephrine) to A23817 were attenuated, but the endothelium‐dependent contractions (quiescent preparations) to the ionophore were augmented. Indomethacin and S18886 prevented the endothelium‐dependent contractions, while dazoxiben reduced them in rings from streptozotocin‐treated rats, suggesting that thromboxane A2, activating TP‐ receptors, is involved. Twelve weeks after the injection of streptozotocin, the changes in endothelium‐dependent relaxations and contractions to A23187 were even more noticeable. The protein expression of COX‐1 was increased in femoral arteries of the diabetic rats. Valeryl salicylate and SC560 inhibited the contractions, suggesting that the EDCFs are produced by COX‐1. At that time, a combination of S18886 with EP1‐blockers was required to abolish the contractions, suggesting that the EDCFs involved act at both TP‐ and EP‐receptors. Rings without endothelium from streptozotocin‐treated rats exhibited a reduced maximal contraction to potassium chloride and U46619, combined with hyper‐responsiveness to the latter, suggesting that more prolonged diabetes also alters the responsiveness of vascular smooth muscle.Conclusion and Implications:The production of EDCFs is progressively increased in the course of type I diabetes. Eventually, the disease also damages vascular smooth muscle.British Journal of Pharmacology (2007) 150, 624–632. doi:10.1038/sj.bjp.0706999
Cardiovascular protection with sildenafil following chronic inhibition of nitric oxide synthase
Authors: Kukreja R C 
Published: January 2007

During the past 18 years, sildenafil has evolved from a potential anti‐angina drug to an on‐demand treatment for erectile dysfunction and more recently to a new orally active treatment for pulmonary hypertension. Recent studies suggest that the drug has powerful cardioprotective effect against ischemia/reperfusion injury, doxorubicin‐induced cardiomyopathy and anti‐hypertensive effect induced by chronic inhibition of nitric oxide synthase in animals. Based on several recent basic and clinical studies, it is clear that sildenafil and other clinically approved type‐5 phosphodiesterase‐5 inhibitors including vardenafil and tadalafil will eventually be developed for several cardiovascular indications including essential hypertension, endothelial dysfunction, ischemia/reperfusion injury, myocardial infarction, ventricular remodeling and heart failure.British Journal of Pharmacology (2007) 150, 538–540. doi:10.1038/sj.bjp.0707132
Effect of the cannabinoid CB1receptor antagonist rimonabant on nociceptive responses and adjuvant‐induced arthritis in obese and lean rats
Authors: Croci T , Zarini E 
Published: January 2007

Background and purpose:Obesity is a risk factor for several inflammation‐based diseases including arthritis. We investigated the anti‐nociceptive and anti‐inflammatory effects of the cannabinoid CB1receptor antagonist rimonabant in lean and diet‐induced obese female rats with arthritis induced by complete Freund's adjuvant (CFA) injected in the right hind‐paw.Experimental approach:The effect of oral rimonabant was assessed in rat paws on thermal hyperalgesia, mechanical allodynia, oedema, global arthritis score, nitrite/nitrate levels and ankle widths.Key results:After 7 but not after 14 days, the inflammatory response to CFA was significantly higher in obese than lean rats; however, the nociceptive response (thermal hyperalgesia and mechanical allodynia) was similar. Oral rimonabant (3 or 10 mg kg−1, once a day for 1 week from day 7 after CFA) only reduced the global arthritic score and joint width in obese rats, with no effect on the paw oedema. It also markedly reduced thermal hyperalgesia and mechanical allodynia in both lean and obese rats, with a greater effect in the latter.Conclusion and implications:Rimonabant appears to be a potent inhibitor of sensorial hypersensitivity associated with CFA‐induced arthritis in obese rats, in which the inflammatory reaction is more severe than in lean rats. It may thus have therapeutic potential in obesity‐associated inflammatory diseases, particularly in the treatment of the pain associated with arthritis.British Journal of Pharmacology(2007)150, 559–566. doi:10.1038/sj.bjp.0707138
Single Units and Sensation: A Neuron Doctrine for Perceptual Psychology?
Authors: Barlow H B 
Published: January 2007

The problem discussed is the relationship between the firing of single neurons in sensory pathways and subjectively experienced sensations. The conclusions are formulated as the following five dogmas: To understand nervous function one needs to look at interactions at a cellular level, rather than either a more macroscopic or microscopic level, because behaviour depends upon the organized pattern of these intercellular interactions. The sensory system is organized to achieve as complete a representation of the sensory stimulus as possible with the minimum number of active neurons. Trigger features of sensory neurons are matched to redundant patterns of stimulation by experience as well as by developmental processes. Perception corresponds to the activity of a small selection from the very numerous high-level neurons, each of which corresponds to a pattern of external events of the order of complexity of the events symbolized by a word. High impulse frequency in such neurons corresponds to high certainty that the trigger feature is present. The development of the concepts leading up to these speculative dogmas, their experimental basis, and some of their limitations are discussed.
Inability of Humans to Discriminate between Visual Textures That Agree in Second-Order Statistics—Revisited
Authors: Julesz B , Gilbert E N , Shepp L A , Frisch H L 
Published: January 2007

In an earlier study by Julesz (1962) pairs of random textures were generated side-by-side using a Markov process with different third-order joint-probability distributions but identical first- and second-order distributions. Such texture pairs could not be discriminated from each other by the human visual system without scrutiny. Unfortunately, Markov processes are inherently one-dimensional while the general processes underlying visual texture discrimination are two-dimensional. Here three new methods are introduced that generate two-dimensional non-Markovian textures with different third-order but identical first- and second-order statistics. All three methods generate texture pairs that cannot be discriminated from each other. The lack of texture discrimination is the more astonishing since the individual elements that form the texture pair are clearly perceived as being very different. However, a counterexample was found that yields discrimination although the texture pair has approximately identical second-order statistics. This case can be explained by assuming that early feature extractors do some preprocessing. These new demonstrations give support to a model of texture discrimination in which the stimulus is first analyzed by local feature extractors that can detect only simple features such as dots and edges of given sizes and orientations. Then the outputs of these simple extractors are evaluated by a global processor that can compute only second- or first-order statistics (that is can compare at most two such outputs).
The Effect of Early Anomalous Visual Inputs on Orientation Selectivity
Authors: Abadi R V 
Published: January 2007

It is now well established that the cortical neurones of cats and monkeys respond best to either lines or edges of a specific orientation. The respective tuning curves of these cells can be broadened by rearing the animals in abnormal visual environments during their critical period of development. Since neurones in the human visual system probably also possess this orientational selectivity, then it is not inconceivable that humans also could demonstrate similar orientational selectivity loss if they too have an anomalous visual input during their early years of life. To test this hypothesis, a simultaneous subthreshold masking technique is proposed as a means for assessing psychophysically the selectivity properties within the human striate cortex. Both visually normal and abnormal systems were considered. No selectivity loss is demonstrated for either the orientationally deprived (i.e. high astigmats) or monocular form deprived (high anisometrope) subjects. The effect of large eye movements (nystagmus) does, however, bring about a coarser selectivity. These results are discussed in relation to recent neurophysiological studies of the critical period in lower vertebrates.
Some Perceptual Effects Generated by Rotating Gratings
Authors: Wade N J 
Published: January 2007

Rotation of a grating at around 2π rad s−1 in continuous illumination results in the appearance of a band lying almost perpendicular to the lines. Two possible bases for the occurrence of this effect were examined. Firstly, the band might represent a moiré fringe due to the overlap of the present grating with one persisting in the visual system from a previous position. Secondly, those parts of the lines farthest from the bisecting diameter will have the greatest linear displacement during rotation; thus, the extremities of each line might fail to be resolved, while those parts nearer the centre are adequately resolved, resulting in the appearance of a band. Three experiments were conducted to test predictions from the two hypotheses. The first experiment involved manipulation of the spatial frequency of the square-wave gratings and the size of the discs bearing them. In the second the line spacing was varied while the line width was kept constant. In the third experiment the angular velocities required to produce bands of different widths were determined. The results did not support either hypothesis unequivocally, and the possibility that both are involved in the effect cannot be discounted. Observation of the rotating gratings under stroboscopic illumination produced either moiré fringes or complex doily-like patterns, depending upon the angular velocity and strobe frequency. These ‘overlap’ effects were used to determine the duration of visual persistence in a fourth experiment. At certain combinations of high angular velocities and strobe frequencies, apparent rotation effects are visible simultaneously in opposite directions.
Studies on Visual Perception of Locomotion
Authors: Johansson Gunnar 
Published: January 2007

The problem about visual discrimination between seeing objects in motion and perception of motion of the perceiver (locomotion) was taken up. A flow of vertical motion was presented to limited areas of the far periphery (45°–90°) of the retina simultaneously with optical information about a stationary room over the rest of the retina. The result was that most subjects perceived themselves as sitting in an elevator continuously moving upward or downward. Thus, peripheral motion stimulation over a few percent of the retinal area determines locomotion perception in apparent competition with information about a static state over the rest of the retina. The same type of stimulus presented to the central part of the retina always brought about perception of object motion and a static perceiver. Effects of size and localization of the area stimulated with the motion flow was studied. Theoretical consequences and problems for further experimental analyses are discussed.
Identification of Familiar and Unfamiliar Faces from Internal and External Features: Some Implications for Theories of Face Recognition
Authors: Ellis Hadyn D , Shepherd John W , Davies Graham M 
Published: January 2007

Three experiments are reported in which recognition of faces from whole faces or internal or external features was compared. In the first experiment, where the faces were of famous people, an advantage was found for identification from internal features. In the second experiment involving unfamiliar faces, however, no difference was found in recognition rates when subjects were given the internal or the external features. In a third experiment famous faces were presented and mixed with other famous faces for a recognition test. As in experiment 1, better recognition occurred from internal as compared with external features. It is argued that the internal representation for familiar faces may be qualitatively different from that for faces seen just once. In particular some advantage in feature saliency may accrue to the internal or ‘expressive’ features of familiar faces. The implications of these results are considered in relation to general theories of face perception and recognition.
Brunelleschi's Perspectives Reconsidered
Authors: Lynes John A 
Published: January 2007

Accounts by Brunelleschi's biographers of the discovery of linear perspective are briefly reexamined. It is suggested that Brunelleschi's familiarity, as a clockmaker, with sundials may have suggested to him a method of drawing perspectives without recourse to geometrical construction from plans and elevations. This would explain several puzzling features of the first perspective, including the choice of subject (the Baptistery of San Giovanni), the lateral inversion of the painting, the necessity for a hole “as tiny as a lentil bean”, and the use of mirrors. The second perspective is then shown to embody lessons learned from the shortcomings of the first. It is concluded that the descriptions written by Vasari and Manetti are essentially sound, but their usual interpretation is thrown into question. In particular they can no longer sustain the centuries-old claim, for which they formed the basis, that the geometrical construction of linear perspective from plans and elevations was discovered by Brunelleschi.
R L Gregory and Others: The Wrong Picture of the Picture Theory of Perception
Authors: Katz Stuart 
Published: January 2007

It is the position of R L Gregory and other cognitive theorists that perceptual knowledge conceived as an inner picture leads to an infinite regress, but that perceptual knowledge conceived as an abstract or coded representation does not. It is argued here that this view is mistaken. All inner representations, whether pictorial or abstract, lead to the regress because all representations, inner or outer, require interpretation, and hence an interpreter. The problem will not disappear, furthermore, by formalizing the representation because rule-following is not equivalent to interpretation. The regress can only be avoided if the whole organism is made the interpreter, and representations are given their appropriate place: in the external world, not inside heads.
Perceptual and Task Factors in Fluent Braille
Authors: Millar Susanna 
Published: January 2007

Hypotheses that fluent braille depends (i) on coding letters by global outline shape for all task and speed levels, or (ii) on lateral dot—gap density scanning in fast reading for meaning were tested with three groups of fluent braillists who differed in reading speeds. In experiment 1, 90°-rotated (near to far) texts under vertical and horizontal finger orientation were used. Hypothesis (i) was not supported. Finger orientation interacted significantly with Speed and Task. Vertical finger orientation, which disrupts lateral scanning, slowed reading for comprehension more than for letter search, and differentially more for faster readers. Horizontal finger orientation, which instead disrupts the familiar finger—body relation, did not have differential effects. The findings support hypothesis (ii). In experiment 2, normal texts and texts containing a degraded dot in some letters were used. These are felt in searching for individual letter patterns, but would disrupt lateral scanning of expected dot—gap density patterns in reading for meaning. The results supported the predictions from hypothesis (ii), that degraded texts slow reading for meaning significantly more than for letter search, and more in the case of faster readers than for the slowest group. Findings were not consistent with hypothesis (i), which predicts that text degradation affects tasks equally, and affects the slowest rather than the fastest readers. The results suggest that perceptual coding in reading differs with task demands and speed.
Projective Invariance and Picture Perception
Authors: Niall Keith K , Macnamara John 
Published: January 2007

Four experiments test the assumption that, in the visual perception of pictures, observers have reliable and direct access to the equivalence of shapes in projective geometry. The assumption is that perception of projective equivalence is the basis of shape constancy (‘the projective thesis’). Observers matched or reproduced abstract planar shapes under conditions of rotation in the picture plane, and pictured rotation in depth. Departure from projective equivalence was assessed in each study by measuring the planar analogue of cross ratio. Projective equivalence was not found to be perceived uniformly where Euclidean equivalence was not judged uniformly, either in recognition tasks or in production tasks. When the projective thesis is put to a suitably general test, confidence in the thesis is undermined.
Anomalous Contours and Illusion of Angularity: Phenomenal and Theoretical Comparisons
Authors: Pinna Baingio 
Published: January 2007

Many experimental comparisons between real and anomalous contours have proven the functional equivalence of the two conditions; however, there are some contradictory findings. One of these is obtained by analyzing the anomalous contours in the light of a new illusion, called the ‘illusion of angularity’. A circle becomes a polygon when it covers the centre of a radial arrangement of black stripes, and a polygon changes its perceptual shape depending on its orientation with respect to the same radial arrangement. Phenomenally, it appears like a very pointed polygon, in which every side is concave or, alternatively, a shape that looks like a circle with angles added in the spaces between the radial stripes, or a polygonal shape in which every side is convex. The reciprocal anomalous counterparts of these conditions, obtained by removing the geometrical/polygonal contours, reveal different results. In the first case, one sees a perfect circle; in the second case, a polygon with blunted vertices, or a circular shape with angular protrusions; in the third case, a deformed circle. These results are inconsistent with some theoretical models proposed to explain the emergence of anomalous contours, namely, all the top-down models expressed in terms of cognitive constructions and perceptual hypotheses, or in terms of global figural organizations. Rather, these comparisons suggest a different interpretation for the two phenomena (the illusion of angularity and anomalous contours). This interpretation is based on dynamic interactions or on network computations that synthesize both real and anomalous contours.
The Perception of Movement and Depth in Moiré Patterns
Authors: Spillmann Lothar 
Published: January 2007

Moiré patterns can produce striking movement effects and in more complex stimuli can induce vivid stereoscopic depth. The physical rules underlying these phenomena are reviewed and their relationship to psychophysics is discussed. First, it is shown how moirés in ‘optical line interference’ patterns are created by superimposing periodic visual stimuli, eg gratings, and shifting them relative to each other. When two gratings are presented in this manner, small differences in spatial frequency, orientation, and speed are magnified. This magnification has prompted the use of moiré patterns both in industry and in art where their enhanced sensitivity to misalignment and spatial distortion has been widely exploited. Next, it is demonstrated how enhanced depth in ‘stereoscopic interference’ patterns is produced by presenting grating stimuli in two (or more) depth planes. The perceived depth effect in the resulting moiré pattern can be elicited similarly by binocular disparity and motion parallax. Finally, it is described how perceived movements occurring in different directions and at different depths are the basis for the perceptual ‘irritations’ that fascinate observers in complex moiré patterns. The use of moirés for the noninvasive examination of the human retina by aliasing is discussed.
The Relative Effectiveness of Serial and Parallel Viewing of Line Drawings Depicting Possible and Impossible Objects
Authors: Tambouratzis Tatiana , Wright Michael J 
Published: January 2007

In a series of experiments, subjects were asked to make judgments concerning the three-dimensional constructibility of line drawings depicting possible and impossible objects. A spectrum of objects was employed in which complexity as well as, for impossible objects, the cause and saliency of the contradiction in three-dimensional structure varied widely. The line drawings were presented under varying viewing conditions and exposure times. It was found that line drawings of possible objects were more often correctly identified than those of impossible ones. Parallel (simultaneous) viewing was more efficient than serial viewing (in which a line drawing moved behind a narrow stationary aperture). The orientation of the aperture did not cause differences in the subjects' performance. Line-drawing complexity and contradiction in three-dimensional structure were not found to be significant for accurate recognition. Finally, no consistent effect of exposure duration on performance could be determined in the range 60–1000 ms.