bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of homogeneous condensation in compressible flows: Ludwieg-tube experiments and simulations
Authors: LUO XISHENG , LAMANNA GRAZIA , HOLTEN A. P. C. , VAN DONGEN M. E. H.
Published: January 2007

Effects of homogeneous nucleation and subsequent droplet growth in compressible flows in humid nitrogen are investigated numerically and experimentally. A Ludwieg tube is employed to produce expansion flows. Corresponding to different configurations, three types of experiment are carried out in such a tube. First, the phase transition in a strong unsteady expansion wave is investigated to demonstrate the mutual interaction between the unsteady flow and the condensation process and also the formation of condensation-induced shock waves. The role of condensation-induced shocks in the gradual transition from a frozen initial structure to an equilibrium structure is explained. Second, the condensing flow in a slender supersonic nozzle G2 is considered. Particular attention is given to condensation-induced oscillations and to the transition from symmetrical mode-1 oscillations to asymmetrical mode-2 oscillations in a starting nozzle flow, as first observed by Adam & Schnerr. The transition is also found numerically, but the amplitude, frequency and transition time are not yet well predicted. Third, a sharp-edged obstacle is placed in the tube to generate a starting vortex. Condensation in the vortex is found. Owing to the release of latent heat of condensation, an increase in the pressure and temperature in the vortex core is observed. Condensation-induced shock waves are found, for a sufficiently high initial saturation ratio, which interact with the starting vortex, resulting in a very complex flow. As time proceeds, a subsonic or transonic free jet is formed downstream of the sharp-edged obstacle, which becomes oscillatory for a relatively high main-flow velocity and for a sufficiently high humidity.
Outcome factors of idiopathic dilated cardiomyopathy in children – a long-term follow-up review
Authors: Azevedo Vitor Manuel P. , Santos Marco Aurelio , Albanesi Filho Francisco M. , Castier M'árcia B. , Tura Bernardo R. , Amino Jose Geraldo C.
Published: January 2007

Background:Idiopathic dilated cardiomyopathy in children has a high rate of mortality. Cardiac transplantation is the treatment of choice in those who fail to respond to therapeutics. Several studies have been carried out to determine unfavourable prognoses, and to provide an early indication for cardiac transplantation. Nevertheless, no consensus has been reached on the matter.Objective:To propose predictors of death in children with idiopathic dilated cardiomyopathy.Methods:We reviewed data extending over 22 years from 142 consecutive children with idiopathic dilated cardiomyopathy, of whom 36 died. The criterions for inclusion were the presence of congestive heart failure or cardiomegaly in a routine chest X-ray, confirmed by enlargement and hypo kinesis of the left ventricle in the echocardiogram. We included asymptomatic children in functional class I. Based on Cox's analysis of clinical and laboratory data, we sought any predictors of death.Results:In univariate analysis, the predictors were functional class IV at presentation (p equal to 0.0001), dyspnoea (p equal to 0.0096), and reduced pedal pulses (p equal to 0.0413). In chest X-ray, they were maximal cardiothoracic ratio (p equal to 0.0001) and pulmonary congestion (p equal to 0.0072). In the electrocardiogram, right atrium overload (p equal to 0.0118), ventricular arrhythmias (p equal to 0.0148) and heart rate (p equal to 0.027). In the echocardiogram, mitral regurgitation of grade 3 to 4 (p equal to 0.002), the left atrial to aortic ratio (p equal to 0.0001), and left ventricle ejection fraction (p equal to 0.0266). In multivariate analysis, the independent predictors were maximum cardiothoracic ratio (p equal to 0.0001), left ventricle ejection fraction (p equal to 0.0013), mitral regurgitation of grade 3 or 4 (p equal to 0.0017), functional class IV at presentation (p equal to 0.0028), and ventricular arrhythmias (p equal to 0.0253).Conclusion:Children, who have these predictors of death should be considered for early heart transplantation when no improvement is observed in clinical treatment.
Resistance to Dietary Obesity in Rats Given Different High-Energy Diets
Authors: Pérez de Heredia  , Garaulet  , Puy Portillo  , Zamora
Published: January 2007

Susceptibility to dietary obesity was studied in Wistar and Sprague-Dawley rats submitted to different high-energy diets. Experiment 1: female Sprague-Dawley rats were fed chow (n = 6) or a high-fat diet (n = 12) for 22 weeks. Experiment 2: Wistar rats were fed chow or a high-fat diet, and Sprague-Dawley rats were given chow, high-fat, sweet condensed milk, or cafeteria diets, for eight weeks (6 animals per group). Food intake and body weight were recorded weekly. Adipose tissue was collected from periovarian, mesenteric, and subcutaneous regions and adipocytes were isolated and measured. Both strains showed similar energy intake and body weight gain. Wistar rats reached greater final body fat contents than Sprague-Dawley rats, regardless of the type of diet. However, resistance to dietary obesity was found in 100% of cases in both experiments. None of the diets succeeded in increasing body fat accumulation when compared to control groups. All adipose tissue locations were equally unaffected, with periovarian fat cells being larger than those in mesenteric and subcutaneous regions in all the groups. In view of the strong resistance to obesity observed in rats, it should be important for researchers to transmit the difficulties of inducing dietary obesity in these animals, in order to prevent bias in science interpretation.
Effects of Dehulled Adlay on Plasma Glucose and Lipid Concentrations in Streptozotocin-induced Diabetic Rats fed a Diet Enriched in Cholesterol
Authors: Yeh  , Chiang  , Chiang
Published: January 2007

Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) is a cereal food for humans and has been also used as a superior medical herb substance and functional food for traditional treatment of diabetes in China. However, its scientific basis as a functional food is still unclear. The purpose of this study was to investigate the effect of dietary dehulled adlay on plasma lipid and glucose concentrations in diabetic rats. The diabetic male Sprague-Dawley (SD) rats, induced by injection of streptozotocin (60 mg/kg subcutaneously), were fed a cholesterol-rich diet (0.5% cholesterol) containing corn starch or dehulled adlay for four weeks. After completion of the experimental period, the abdominal adipose tissue and liver of rats were excised and weighed, and the plasma glucose, triglyceride, and lipoprotein cholesterol concentrations were assayed. The results showed that diabetic rats fed a dehulled adlay diet exhibited a greater adipose tissue weight (9.36 ± 3.43 vs. 5.39 ± 3.04 g, p < 0.05) and a reduced food intake (39.3 ± 5.9 vs. 61.0 ± 11.7 g/day, p < 0.05) when compared with animals fed a cornstarch diet. Significantly decreased plasma glucose (261.6 ± 96.6 vs. 422.1 ± 125.4 mg/dL, p < 0.05), total cholesterol (289.4 ± 140.6 vs. 627.3 ± 230.5 mg/dL, p < 0.05), and triglyceride (52.3 ± 14.4 vs. 96.5 ± 36.6 mg/dL, p < 0.05) levels were observed in rats fed the dehulled adlay diet. In addition, the ingestion of dehulled adlay appears to significantly decrease plasma low-density lipoprotein (LDL) plus very low-density lipoprotein (VLDL) cholesterol concentrations. Rats fed a dehulled adlay diet showed an increase in fecal weight and cholesterol contents of stools. Although a significantly decreased plasma thiobarbituric reactive substances (TBARS) value was observed in diabetic rats fed the dehulled adlay diet (6.2 ± 3.4 vs. 11.0 ± 3.8 nmol malondialdehyde (MDA)/mL, p < 0.05), no significant difference in the hepatic TBARS value was observed between the two dietary groups. Results from the present study suggest that dehulled adlay exhibited not only a hypolipidemic effect but also displayed a hypoglycemic ability in diabetic rats, indicating that dehulled adlay may play an important role in the regulation of plasma lipid and glucose metabolisms in diabetic rats induced by streptozotocin.
Folate Deprivation and Copper Exposure Potentiate Reactive Oxygen Species Generation and Chromosomal DNA Loss but not Mitochondrial DNA Deletions in Rat Hepatocytes
Authors: Lin  , Yu  , Chou  , Huang
Published: January 2007

Both increased copper and reduced folate levels are commonly found in patients with liver diseases. To better understand the mechanisms by which folate deprivation interacts with copper to contribute to hepatocellular toxicity, rat primary hepatocytes were isolated, cultured in folate-deprived (FD) RPMI medium, and assayed for cytotoxicity after copper sulfate (CuSO4) exposure. MTT measurement and trypan blue assay showed that elevated CuSO 4 levels aggravated cell death of folate-deprived but not folate-sufficient hepatocytes. CuSO 4 treatment increased the levels of intracellular reactive oxygen species (ROS) by 3 times in FD hepatocytes and tripled the proportion of FD hepatocytes with hypodiploid DNA contents. Measurement of membrane phosphatidylserine exposure indicated that the CuSO 4-mediated toxicity in FD hepatocytes was not mediated by the apoptotic pathway. Real-time polymerase chain reaction (PCR) analysis revealed that CuSO 4 treatment did not increase the occurrence of a 4834-bp mtDNA (mtDNA4834) deletion in FD hepatocytes. Preincubation of FD hepatocytes with various concentrations of folate prior to CuSO 4 treatment did not modulate the mtDNA 4834 deletion. Taken together, the data suggest that elevated copper levels potentiate cell death of folate-deprived hepatocytes, which is primarily associated with increased ROS generation and chromosomal DNA loss. The cytotoxicity exerted by folate depletion and elevated copper levels, however, is not due to apoptosis or accumulated mtDNA 4834 deletions in primary hepatocytes.
Rapid fluctuations in the deep North Atlantic heat budget during the last glacial period
Authors: Skinner L. C. , Elderfield H.
Published: January 2007

Our understanding of past ocean‐climate interactions has been hampered by a paucity of proxy reconstructions of physical ocean circulation parameters. Here we present the first detailed record of deepwater temperature variability that resolves Dansgaard‐Oeschger climate fluctuations during the last glaciation. Results indicate a positive coupling between abrupt temperature changes over Greenland and in the deep North Atlantic that was mediated by perturbations to the Atlantic overturning circulation. The occurrence of sharp warming events at the center of the “Heinrich” stadials 4 and 5 further indicates that the response of the ocean interior was less static across these major climate events than has been previously apparent.
Pharmacological characterization of mouse GPRC6A, an L‐α‐amino‐acid receptor modulated by divalent cations
Authors: Christiansen B , Hansen K B , Wellendorph P , Bräuner‐Osborne H
Published: January 2007

Background and purpose:

GPRC6A is a novel member of family C of G protein‐coupled receptors with so far unknown function. We have recently described both human and mouse GPRC6A as receptors for L‐α‐amino acids. To date, functional characterization of wild‐type GPRC6A has been impaired by the lack of activity in quantitative functional assays. The aim of this study was thus to develop such an assay and extend the pharmacological characterization of GPRC6A.

Experimental approach:

We have engineered a novel cell‐based inositol phosphate turnover assay for wild‐type mouse GPRC6A based on transient co‐expression with the promiscuous GαqG66D protein, known to increase receptor signalling sensitivity. This assay allowed for measurements of L‐α‐amino acid potencies. Furthermore, in combination with an assay measuring inward currents at Ca2+‐activated chloride channels in Xenopus oocytes, the divalent cation‐sensing ability of the receptor was examined.

Key results:

Using our novel assay, we demonstrate that the basic L‐α‐amino acids ornithine, lysine, and arginine are the most potent agonists at wild‐type mouse GPRC6A. Using two different assay systems, we show that divalent cations do not activate the Gq signalling pathway of mouse GPRC6A per se but positively modulate the amino‐acid response.

Conclusions and Implications:

This is the first reported assay for a wild‐type GPRC6A successfully applied for quantitative pharmacological characterization of amino acid and divalent cation responses at mouse GPRC6A. The assay enables further search for GPRC6A ligands such as allosteric modulators, which may provide essential information about the physiological function of GPRC6A.

British Journal of Pharmacology (2007) 150, 798–807. doi:10.1038/sj.bjp.0707121
Young’s modulus reduction of defective nanotubes
Authors: Pugno Nicola M.
Published: January 2007

In this letter the author calculate, by applying fracture mechanics, Young’s modulus reduction for a nanotube, imposed by the presence of nanodefects, with specified size, shape, and number. The results are compared with atomistic and continuum simulations. Vacancy fraction, eccentricity, orientation, and interaction of defects are found to be the key parameters influencing the stiffness degradation.
Novel sensor design for torque magnetometry
Authors: Kohout Stefan , Roos Josef , Keller Hugo
Published: January 2007

Torque magnetometry is a powerful method to determine a sample’s magnetic properties. In a torque magnetometer, the sample under interest is mounted on a suitable sensor, the core part of the instrument. Piezoresistive atomic force microscope tips are proven to be very useful torque sensors and have already been optimized for the specific needs of torque magnetometry. However, this type of sensor did not offer the possibility of measuring torque along two perpendicular directions simultaneously without sacrificing sensitivity. In this article we demonstrate a fundamentally new sensor design based on the piezoresistive readout technique, which offers a large variability of measurement modes. With a symmetric arrangement of the sensor legs, concurrent two-axis measurements are easily possible with two separate readout circuits. Furthermore, the variability can be exploited by fabricating a thermometer on the sample platform to directly measure the sample temperature. Test measurements are in good agreement with elasticity calculations.
Contrast Sensitivity and Increment Threshold
Authors: Bodis-Wollner I
Published: January 2007

The threshold of rectangular and annular increments was established on square-wave gratings of 1 foot lambert mean luminance. In the range of 5–18 cycles/degree the threshold fell as the spatial frequency of the background increased. The threshold change was similar for rectangles and annuli, but the exponent of the curve differed according to the relative orientation of the test stimulus. The threshold curve of rectangles was related to the human contrast sensitivity curve, and it was found that threshold is directly proportional to the contrast of the grating and effective contrast is a function of the spatial frequency of the pattern. In the range below 5 cycles/degree of the grating pattern the threshold dropped. This is attributed to the low-frequency decline in contrast sensitivity, but this decrease occurred at a higher spatial frequency than expected.

Apparently orientation and size specificity in field adaptation is compatible with functions of cells established in the visual cortex of primates and humans.
Kinaesthetic Spatial Aftereffects from One and Two Wrists: A Problem for Neural Enhancement Theory
Authors: Empson Janet M , Frisby J P
Published: January 2007

An experiment is described which investigated a kinaesthetic spatial aftereffect related to the wrist joint. In one condition 24 Ss made a kinaesthetic judgement of ‘straightahead’ using rotation of only one wrist. In a second condition 24 different Ss made the same spatial judgement using both wrists at once. Kinaesthetic aftereffects were measured in both conditions and it was found that the mean aftereffect per wrist in the two-handed task was about three times the size of that found in the single-handed one, a difference significant at the p < 0 01 level. It is argued that this finding constitutes a difficulty for Over's (1971) ‘neural enhancement’ theory which seeks to explain kinaesthetic spatial aftereffects solely in terms of the neural events underlying the perception of individual joint positions.
Infants' Visual and Tactual Inspection of Objects
Authors: Harris P L
Published: January 2007

Following the development of visually-guided reaching, infants examine objects by touching and looking at them. Two experiments are presented which show that for infants of [Formula: see text] months these two modes of inspection are synchronized. Also, infants prefer to look at and to touch an object which they have not touched before, as compared with one which is tactually familiar. This preference appears to be attributable to the opportunity to correlate visual and tactual information concerning the object, rather than to touch it for the first time.
Visual Mechanisms in the Copepod Copilia
Authors: Moray N
Published: January 2007

In the planktonic copepod Copilia (Giesbrecht) the visual system consists of paired visual receptors, which appear to scan the visual field in the focal plane of the objective lens of the eye. A description of three species is given from which an evolutionary sequence may be deduced. Speculations are offered as to the advantages to be gained by such a mechanism.
The Site of Orientational Constancy
Authors: Mitchell D E , Blakemore C
Published: January 2007

The visual world remains perceptually quite stable during rotation of the head. There is some physiological evidence that in the cat this phenomenon of orientational constancy might result from changes in the orientation selectivity of neurones in the visual cortex during head tilt. In humans adaptation to a grating causes elevation of the threshold contrast for detecting gratings of similar orientation, and it can be argued that this aftereffect depends on neurones in the human visual cortex. If the head is tilted during such adaptation, but is vertical when the threshold is tested with a vertical grating, the maximum aftereffect occurs for an adapting grating that was vertical on retinal coordinates. We conclude that in humans the mechanism for orientational constancy occurs after the visual cortex.
‘Interest’ and ‘Pleasure’: Two Determinants of a Monkey's Visual Preferences
Authors: Humphrey N K
Published: January 2007

When given a choice between two visual stimuli (plain fields of light of different colour, photographs, cine films, etc.) monkeys show strong and consistent preferences. The strength and direction of the preferences is determined by two independent factors: the monkey's relative ‘interest’ in the stimuli (determined largely by their information content) and his relative ‘pleasure’ (determined by qualities such as colour and brightness). With an unchanging stimulus ‘interest’ rapidly fades but ‘pleasure’ (or ‘unpleasure’) remains stable. If the two factors are set against each other, as when a red-coloured cine film is paired with a plain white field (the pictorial content of the film being interesting, its colour unpleasant), interest over-rides pleasure in determining the observed preference. A quantitative model based on these principles predicts the behaviour in a variety of situations with great accuracy.
Pictorial Recognition in a Remote Ethiopian Population
Authors: Deregowski J B , Muldrow E S , Muldrow W F
Published: January 2007

A sample of Me'en (Mekan) drawn from a population having minimal contact with pictorial materials was found to be able to recognise correctly, albeit gradually and with a degree of effort, clearly depicted animals. They did make however some responses which in the west would be considered anomalous, and appeared to find the task stressful.
Laterality Effects in Diotic Listening
Authors: Morais J , Bertelson P
Published: January 2007

Three pairs of simultaneous consonant–vowel syllables were presented over two loudspeakers, and the subject attempted total recall. With the loudspeakers situated to the left and to the right of the subject, the message from the right is better recalled. With one loudspeaker in front of the subject and the other on one side, the message from the middle is better recalled. These results are discussed in terms of the interpretations which have been proposed for right ear superiority in dichotic listening to verbal material.
Effects of Movements upon the Appearance and Duration of a Prolonged Visual Afterimage: 2. Changes Arising from Movement of the Observer in Relation to the Previously Afterimaged Scene
Authors: Davies P
Published: January 2007

Gregory et al. (1959) reported that visual afterimages undergo changes in appearance when the observer moves. Davies in part 1 of this series reported qualitative and quantitative effects upon the appearance and duration of afterimages when a portion of the body incorporated in the afterimaged scene was moved. This paper reports an experiment in which 12 subjects afterimaged a long narrow corridor before (a) standing still and observing the afterimage; (b) turning right or left through 90 degrees and observing; and (c) walking along the afterimaged corridor. Each task was performed 5 times in a counterbalanced order by each subject. The timed observation period was from the flash to the termination of the long positive afterimage. Subjects reported qualitative changes in the appearance of the afterimage when observing it after turning right or left or during walking. The duration of the afterimage was also greater in those experimental conditions involving movement than in the condition involving immobile observation.
Assimilation Theory and the Reversed Müller—Lyer Illusion
Authors: Pressey A W , Bross M
Published: January 2007

The assimilation theory of geometric illusions was employed to explain the reversed ingoing form of the Müller–Lyer illusion. The mathematical formula which was used previously to predict changes in the Ponzo and Poggendorff illusions was employed in simulated experiments on the reversed Müller–Lyer illusion. It correctly predicted the form of the function, relating illusion to size of gap, that was found previously by Fellows (1967). In addition it correctly predicted the effects of increasing the length of the fins on the form of the function. Finally a reversed outgoing Müller–Lyer illusion was found when the outgoing fins were moved towards the center of the shaft.
Short-Term Memory for Stroboscopic Movement Perception
Authors: Julesz B , Chiarucci E
Published: January 2007

Two-dimensional arrays of black and white random dots were generated by a computer such that features (e.g. large clusters) which could be attended to were eliminated. The first N frames were uncorrelated, but these same N frames were repeated many times. When presented at 24, 16, 12, and 8 frames/s, these movie sequences appeared as dynamic noise and subjects were tested for the longest cycle time at which they could still perceive some periodicity of motion. Subjects' judgment of seeing periodic motion decayed exponentially with the cycle duration. The time constant of this exponential was 540 ms ± 250 ms, which supports the hypothesis that memory for movement is longer than iconic memory and is about equal to echoic memory. This hypothesis has 0·94 probability of being true. At the same cycle durations, memory for stroboscopic movement also depended on N, and deteriorated for N ≥ 7.
Perceptual Shape Constancy in Early Infancy
Authors: Day R H , McKenzie B E
Published: January 2007

Infants 6 to 16 weeks old exhibited shape constancy for plain solid objects. Habituation of visual fixation occurred with respect to repeated viewing of a cube in the same orientation and of a cube in different orientations, but not when viewing photographs of a cube in different orientations. Since the photographs reproduced the outline shape and the luminance patterns of the solid object, it is suggested that motion parallax mediates the shape constancy. Infants responded to the photographs as if the latter were patterns rather than as if they were representations of solid objects.
Visual Perception of Bending Motion
Authors: Jansson G , Johansson G
Published: January 2007

Principles of the perception of a special kind of partially rigid motion—bending motion—are explored. The proximal stimuli consisted of an outline quadrangle with various combinations of changes of length and direction of the four sides. The result demonstrated a perceptual preference for rotary motion over bending motion, and of bending motion over two-dimensional form change (stretching). The principle of minimum object change can predict this result, implying that rotation, bending, and stretching are perceptually preferred in this order.
Intelligence Factors in the Perception of Form through a Moving Slit
Authors: Rock I , Sigman E
Published: January 2007

When a narrow slit moves over a line figure (or the equivalent stimulus is simulated by a short line segment appropriately displacing within a moving slit), observers often perceive an extended figure although the stimulus information is ambiguous. In several experiments it is shown that the perception of a figure tends to occur, provided the stimulus information is compatible with the perceptual ‘solution’ of a figure revealed by a moving aperture: the visible segment of the figure must completely fill the aperture, the surround of the aperture must appear to be opaque and extend an adequate distance on both sides, the aperture must be perceived as an opening rather than as a figure, and, if the slope of the segment is visible, it must change appropriately from moment to moment. Thus the outcome can be thought of as an intelligent, elegant solution to the problem posed by the transforming proximal stimulus.
A Distractive Effect of Peripheral Attention on Foveal Trigram Recognition
Authors: Bodis-Wollner I
Published: January 2007

The recognizability of tachistoscopically presented foveal trigrams was investigated as a function of paying attention, or not paying attention, to simultaneously exposed parafoveal trigrams. The same set of stimuli was presented in both conditions. All six observers made a significant number of errors at 50 ms stimulus duration in the attentive condition. This occurred even though they could not correctly report the parafoveal stimulus. Performance reached 95% correct at 200 ms stimulus duration, just when parafoveal trigrams were occasionally identified. At 50 ms stimulus duration in the attentive condition, errors were more marked for non-wordlike center trigrams. When the parafoveal trigram was non-wordlike, its distractive effect was greater than when it was wordlike. Neither distance nor position of the parafoveal trigrams were significant factors. The distractive effect of peripheral attention on recognition of letter stimuli suggests that information from parafoveal stimuli is available through attention. The results do not suggest that during a short exposure parafoveal information triggers attention: they rather indicate that conscious attention determines the processing of parafoveal stimuli.
Is Gradual Recognition of Pictures by Ethiopian Subjects a Differentiation Process or a Pattern Construction Process?
Authors: Kennedy J M
Published: January 2007

Reanalysis of protocols from a report by Deregowski et al. favours the hypothesis that nonpictorial peoples viewing pictorial test materials may initially recognize details and gradually build up a composite structure, rather than—as Deregowski et al. proposed—engage in a process of differentiation, from a global mass towards finer discriminations.
Experience of Tactile Vision
Authors: Guarniero G
Published: January 2007

The accompanying paper was written following a three-week training course with the Tactile Vision Substitution System (TVSS) under development at the Department of Visual Sciences, University of the Pacific, San Francisco. The instrumentation has been described elsewhere by Collins and Madey (1974) and perceptual studies and underlying theory by Bach-y-Rita et al. (1969), White et al. (1970), and Bach-y-Rita (1972). The present paper is a personal account that provides insight into a perceptual aspect of sensory substitution studies.
The Surrogate Functions of Lines in Visual Perception: Evidence from Antipodal Rock and Cave Artwork Sources
Authors: Kennedy J M , Silver Judy
Published: January 2007

Lines in outline pictures may function as surrogates for features of the visible environment, without explicit tutoring in a convention (unlike representation in words). This interpretation of line representation is supported by the finding that drawings from ancient sources—in antipodal regions of the world—contain outline depiction of the same features as are found in modern outline sketches.
Use of Sensory Recombination and Somatosensory Deafferentation Techniques in the Investigation of Sensory-Motor Integration
Authors: Taub E , Goldberg I A
Published: January 2007

Sensory rearrangement and somatosensory deafferentation experiments are being employed in this laboratory, both singly and in combination, as complementary research strategies for elucidating the role of direct sensory feedback in the learning and performance of various categories of movement.

In deafferentation experiments on adolescent monkeys, we found that movements of almost all types can be learned and performed in the absence of guidance from the periphery. Moreover, recent work with primate infants deafferented on the first day of life has demonstrated that somatosensory feedback and spinal reflexes are also not necessary, after birth, for the ontogenetic development of most types of movement performed by the forelimbs.

Sensory rearrangement studies with human subjects were directed at examining prism adaptation as a learning phenomenon. One experiment showed that, in controlling the rate of performance of an operant response, decreases in the amount of lateral displacement of vision could be used as a reward, and increases could be used as a punishment. These results support the central condition required by our previously formulated avoidance theory of prism adaptation, namely that the sensory discordance produced by prisms is aversive. In three further experiments, distribution of practice—a standard learning variable—was found to be a powerful means of manipulating such effects as (i) magnitude of adaptation, (ii) intermanual transfer, and (iii) adaptation when the subject observes his passively moved limb during the exposure period.

In an experiment combining the two techniques, the amount of prism aftereffect in monkeys with deafferented forelimbs was compared with the amount in normal monkeys as a means of evaluating the ‘proprioceptive change’ hypothesis of prism adaptation. The results provided supporting evidence for the theory, indicating that the adaptation involved a recalibration of motor—kinesthetic systems rather than a change in visual perception.
The Subject: A Neglected Factor in Recombination Research
Authors: Warren D H , Platt B B
Published: January 2007

Individual differences in adaptability to visual rearrangement have typically been ignored as a subject of investigation. However, it is clear that there is marked variability among subjects in terms of the extent to which they adapt, and possibly the form in which their adaptation takes. The present investigation examined the different ways in which subjects respond to the same experimental demands in a prism-adaptation experiment. Furthermore, a number of relevant ‘perceptual traits’ (for example the ability to fixate a visual target) were measured and found to correlate, in varying degrees, with adaptation. In general, the conclusion drawn from the latter results was that subjects who have relatively good control over their eye movements and fixations will reveal adaptation in terms mostly of the felt position of the exposed limb; subjects with relatively good control over their limb movements will adapt more in terms of their vision and hence will demonstrate a significant degree of intermanual transfer.
The Role of Figure Orientation and Apparent Depth in the Perception of the Horizontal—Vertical Illusion
Authors: Schiffman Harvey R , Thompson Jack G
Published: January 2007

An experiment was performed which examined the role of figural orientation directly, and the role of an inappropriately invoked size-constancy mechanism indirectly, in the actuation and magnitude of the horizontal—vertical illusion. When the vertical line of the stimulus figure was aligned above the horizontal line, the illusory effect was significant and positive; in contrast, when the vertical line was located below the horizontal line, the illusion was negative. Under the assumption that a vertical line can appear as a foreshortened line in depth, these findings support an explanation based on the operation of a misapplied size-constancy mechanism.
Description of a New Visual Illusion: A Drawing of a Four-Dimensional Cube
Authors: Finch Dennis
Published: January 2007

The visual responses evoked by an oblique projection of a four-dimensional cube are discussed and attention is drawn to the visual complexity and illusions evoked by this figure.
A Size Illusion Based upon a Minimal Interposition Cue
Authors: Coren Stanley , Girgus Joan S
Published: January 2007

It has often been suggested that many visual geometric illusions are caused by inappropriate constancy scaling triggered by depth cues implicit in the two-dimensional array. A new size illusion based upon a minimal interposition cue is presented, which seems to support this contention. Asymmetries in the results suggest that the major component of the illusion is overestimation of apparently more distant targets rather than underestimation of apparently closer targets.
Observations on Binocular Spatial Frequency Reduction in Random Noise
Authors: Tyler Christopher W
Published: January 2007

Binocular spatial frequency reduction for random visual noise stimuli is contrasted with MacKay's (1964) homogenisation effect. Several observations lead to suggestions about the anatomical sites of these two perceptual effects.
On the Ability to Discriminate Original from Mirror-Image Reproductions of Works of Art
Authors: Blount Patricia , Holmes Janet , Rodger Jill , Coltheart Max , McManus Chris
Published: January 2007

Subjects were shown pairs of slides; one member of each pair represented a painting in its correct left-right orientation and the other a mirror image of the same painting. For each pair, subjects were asked (a) to choose which they preferred, (b) to choose which they thought was the original, and (c) to rate their confidence that they had seen the picture before. Subjects were only able to discriminate between originals and mirror images for those paintings they were highly confident of having seen before.
The Perception of Linear Gestalten by Rat and Monkey: Sensory Sensitivity or the Perception of Structure?
Authors: McGonigle Brendan O , Jones Barry T
Published: January 2007

Four experiments on rats and squirrel monkeys are reported which show that the well-known transposition by animals to continuous from broken or interrupted line stimuli, first reported by Krechevsky, is attributable to their failure to transfer from simultaneous to successive discrimination of dot patterns. When given appropriate successive discrimination training, however, monkeys reverse their original preference and select dot instead of continuous line stimuli.
Effects of Exposure to a Tilted Room on Kinesthetic Postexposure Responses
Authors: Wallace Meredith , Singer George , Mottram Jan , Purcell Terry
Published: January 2007

It has been shown earlier that visual exposure to a room tilted 22° leads to long-lasting changes in visually guided postexposure judgments of the vertical in the direction of room tilt. Data from the present experiments indicate that visual exposure to the tilted room also alters kinesthetically-guided postexposure judgments of vertical in the same direction. This change occurs in responses made by both hands regardless of whether the hand tested was used to make the judgments during the exposure phase.
Asymmetry in the Müller-Lyer Illusion: Artifact or Genuine Effect?
Authors: Christie Penelope S
Published: January 2007

The Müller-Lyer illusion was measured in thirty-five female subjects using the equation method. Three figures based on the illusion were used. One (outgoing fins) produced an illusion of expansion, another (ingoing fins) produced an illusion of contraction, and one was a plain line. The plain line was included to control for the error of the standard as a possible ‘contaminating factor’ which may produce asymmetry in the Müller-Lyer illusion. Although the error of the standard was found to correlate with the asymmetry to a statistically reliable degree, it accounted for only 39% of the size of the asymmetry and only 15% of the variance. At least some of the asymmetry is therefore attributable to the error of the standard, but the data indicate that there is another contributing factor (as yet unspecified). The possibility that the Müller-Lyer illusion may be inherently asymmetrical is discussed.
The Contribution of Relational Factors to Line-Length Matches
Authors: Wenderoth Peter
Published: January 2007

Both Künnapas and Rock and Ebenholtz investigated the effects of surrounding-frame size upon line-length judgments. Whereas Künnapas obtained errors of the order of 10–15%, typical of those which occur in other geometrical illusion figures, Rock and Ebenholtz reported errors closer to 100%. Rock and Ebenholtz claimed that perceived size is largely relationally determined and that this fact was obscured in Künnapas' experiment by allowing observers to compare the test lines directly with each other and within a common framework provided by the wall of the room.

On the contrary, the experiments reported here suggested that errors in the Rock and Ebenholtz study may have been inflated by their use of nondirective instructions and by the confounded effects of other variables. When the Rock and Ebenholtz experiments were repeated with adequate controls over these variables, the effect of surrounding frames on line-length matches were of the order of 15–19%, similar to those of Künnapas but much smaller than those reported by Rock and Ebenholtz. The complexity of the stimuli in the Rock and Ebenholtz type of experiment is such, however, that the effects of a number of variables and possible cue conflicts remain to be investigated.
The Perpendicular Error and the Vertical Effect in Children's Drawing
Authors: Ibbotson Andrew , Bryant Peter E
Published: January 2007

It has been known for some time that children have particular difficulty drawing lines that are not perpendicular. But this difficulty has not been studied systematically. By systematically varying, in three experiments, the baseline, the response, and the kind of figures to be copied, we showed that the tendency to draw angles as more perpendicular than they actually are is a general one which occurs as much with abstract as with meaningful material and with radically different responses. We also discovered an unexpected effect, the vertical effect, which takes the form of the error occurring much less when a vertical baseline is involved than with other baselines.
Sensory Interaction: Vision is Modulated by Hearing
Authors: Taylor Richard L , Campbell Gweneth T
Published: January 2007

An irrelevant noise was turned on at various points during a visual reaction-time task. Latencies were reliably smaller than on quiet trials, provided the noise was turned on when a subject was looking at a relevant visual stimulus. This effect occurred regardless of whether the distribution of interstimulus intervals was constant or varied during a session, as well as independently of a subject's base rate of response and level of practice in the task. But it disappeared if reaction times in completely noisy sessions were compared to performances in quiet sessions. This effect was found to vary systematically with the orientation of and the hemiretina stimulated by a test form, but not with the particular ear stimulated by a noise. A model is suggested for these and related results in which the arousal elicited by a loud sound in the central nervous system either activates associative memories of form, inhibits early components of striate cortical unit response to the intensive properties of a visual stimulus, or both.
Neural Interactions and Subjective Contours
Authors: Coren Stanley , Theodor Leonard H
Published: January 2007

Increment thresholds were measured on either side of the locus of subjective contours and in equivalent loci for control figures. The data indicate a small change in increment threshold value in the direction predicted by theories postulating neural interactive components in the formation of subjective contours.
Natural Reversing Figure: Interleaving Stars of David
Authors: Kennedy John M
Published: January 2007

A natural biological formation presents triangles forming Stars of David. Elements are readily grouped into first one, then another star.
Cue Saliency in Faces as Assessed by the ‘Photofit’ Technique
Authors: Davies Graham , Ellis Hadyn , Shepherd John
Published: January 2007

The present study attempted to assess the relative salience of different parts of the human face through the manipulation of the features contained in the Photofit Kit. Subjects observed a face constructed from the kit before attempting to identify the same face in an array of alternatives. The alternatives differed from the target in only one feature and this was systematically varied within the array. Nose changes were least likely to be noticed, followed by mouth and eyes, with foreheads producing the lowest rate of error. This order of features held irrespective of the similarity of the distractors or whether judgements were made in the presence or in the absence of the target. The chin region produced different results depending upon the similarity of the distractors. The results are discussed in relation to earlier experiments in which Photofit and previous studies of cue saliency were used.
On the Use of ‘Calibration Equations’ in Perception Research
Authors: Mershon Donald H , Kennedy Michael , Falacara Gary
Published: January 2007

Gogel's procedure or using ‘calibration equations’ to obtain reports of perceived distance which are at least partially independent of individual differences in response bias, was examined. The procedure involves determining the relationship between reported and physical distances in a full-cue viewing situation. By making four assumptions, this equation can be used to ‘calibrate’ responses gathered from other situations in which perceived distances are under investigation. In the present experiment, both verbal and string-pull measures of perceived distance were obtained for several objects under reduced viewing conditions. Calibration equations were determined for each response measure in a full-cue setting. The usefulness of the calibration technique was tested by comparing the differences between the two response measures for each object seen in reduced viewing, both before and after the application of the calibration procedure. The results indicated that, consistent with the usefulness of the calibration technique, group differences between the measures were almost always decreased by the procedure. However, no general improvement in the agreement of the measures was found when the data were examined on an individual basis. From the results, a modification of the method of calculating calibration equations was suggested that might increase its usefulness by simplifying the arithmetic operations required for the procedure.
Feature Analysers, Optical Illusions, and Figural Aftereffects
Authors: Oyama Tadasu
Published: January 2007

Simple displacement models cannot explain some aspects of optical illusions and figural aftereffects. The orientation-detector interaction model proposed by Blakemore and others is more suitable to explain many aspects of the Zöllner illusion, positive and negative illusions, the effect of gap between the inducing and test lines, and the anisotropy of illusions. If we hypothesize size detectors whose tuning width and distribution steps are proportional to logarithmic size, interactions between them explain well the fact that the Delboeuf illusion and figural aftereffects of circles are determined by the size ratio of the inducing to test circle, not by the absolute distance between the contours of these circles.
Visual Stimuli for Strabismic Suppression
Authors: Schor Clifton M
Published: January 2007

The effects of orientation and spatial frequency of grating stimuli upon suppression were examined with a binocular rivalry paradigm in a group of ten strabismic patients and in a control normal group. Duration, frequency, and period of rivalry were examined as functions of differences in orientation and spatial frequency of dichoptic achromatic sinusoidal gratings. Records were made of responses by the sighting and by the nonsighting eye as well as responses during periods of combined binocular vision. Strabismic subjects reported normal binocular rivalry when presented with gratings of dissimilar orientation. Suppression of the deviating eye in strabismic subjects occurred with stimuli of similar orientation and was unaffected by spatial-frequency differences between dichoptic stimuli. Suppression was most intense under conditions that normally stimulate stereopsis and sensory fusion.
The Geometry of the Correspondence between Two Retinal Projections
Authors: Ninio Jacques
Published: January 2007

Since each retinal projection of an object has some definite geometric relation to it, the two projections of a same object are related to each other. The correspondences between points, linear segments, and orientations on the two retinas are discussed thoroughly in three-dimensional geometry, and the constraints that tie the projections (the ‘projective invariants’) are presented. Some widely held conceptions on disparity or the ambiguity problem in binocular stereopsis appear to be based upon representations that are correct in particular situations, but are misleading in the general case.

I suggest that in order to achieve binocular stereopsis, the brain does not proceed by complete trial and error, but may guide its search for correspondences by taking advantage of the geometric constraints. There are at least four major possible strategies: (i) a metric strategy, as initially proposed by Julesz; (ii) a projective strategy based on the law of invariance of the anharmonic ratio and Desargue's theorem; (iii) a perspective strategy discussed in relation to the homology relationships between vanishing points and in relation to physiological studies on cells of visual cortex; and (iv) a more dynamic strategy based upon the geometric properties of the Zöllner illusion.
Stochastic Models and Fluctuations in Reversal Time of Ambiguous Figures
Authors: de Marco Angelo , Penengo Piero , Trabucco Aurelia , Borsellino Antonio , Carlini Franco , Riani Massimo , Tuccio Maria Teresa
Published: January 2007

Five probability distributions for the description of temporal fluctuations in the perception of ambiguous figures were fitted to previously obtained experimental results and classified according to their efficiency in describing the data. The gamma, Wiener, and Capocelli-Ricciardi distributions showed the highest efficiency, while the χ2 and Taylor-Aldridge distributions showed a very low efficiency. Therefore the underlying process may be described either by a simple Poisson model or by a random-walk model. For the gamma distribution there was a strong correlation between the parameters, while for the Wiener distribution this correlation was lower.