Depth perception in motion parallax and stereokinesis.

Perceived depth in the stereokinetic effect (SKE) illusion and in the monocular derivation of depth from motion parallax were compared. Motion parallax gradients of velocity can be decomposed into 2 components: object- and observer-relative transformations. SKE displays present only the object-relative component. Observers were asked to estimate the magnitude and near–far order of depth in motion parallax and SKE displays. Monocular derivation of depth magnitude from motion parallax is fully accounted for by the perceptual response to the SKE, and observer-relative transformations absent in the SKE are of perceptual utility only as determinants of the near–far signing of perceived sequential depth. The amount of depth and rigidity perceived in motion parallax and SKE displays covaries with the projective size of the stimuli. The monocular derivation of depth from motion is mediated by a perceptual heuristic of which the SKE is symptomatic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motion parallax and children's distance perception.

Studied the effectiveness of motion parallax for relative and absolute distance judgments using 48 2nd, 4th, and 6th graders and college adults. Two targets were viewed either monocularly with a fixed head, monocularly with head movements providing motion parallax, or binocularly with head movements providing motion parallax. Ss adjusted the distance of a comparison rod to match the perceived distance of the target, or simply indicated which was nearer. For absolute judgments, accuracy was not affected by age level of the Ss; however, a developmental decrease in the variability of judgment was observed. There were no grade effects for relative judgments. For both judgments, the addition of motion parallax information increased accuracy. Results indicate that children are capable of registering array velocity information for distance. The ability to register self-movement or to integrate self-movement and array motion in the perception of absolute distance may account for the observed developmental changes. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is binocular correspondence and disparity still a dominant factor in binocular depth perception?

Laws of binocular correspondence and disparity are regarded as bases for explanation of most of the phenomena of binocular depth perception in the near field of vision. Abnormal phenomena such as differences in astigmatism of the 2 eyes, differences in acuity, cases of natural aniseikonia, investigated by the author, confirm the validity of the laws of correspondence and disparity and also of the law of intersection of visual directional lines. The inadequacies of other theories of binocular depth perception are pointed out and the author concludes that they cannot supplant the laws of binocular correspondence and disparity for the great majority of cases of binocular perception of depth in the near field of vision. (46 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depth perception as a function of motion parallax and absolute-distance information.

Conducted 3 experiments with 12 observers from a university community to determine whether the visual system calibrates motion parallax according to absolute-distance information in processing depth and to map the range of depth perception as a function of distance and motion parallax. The parallax was created by yoking the relative movement of random dots displayed on a CRT to the movements of the head. In Exp I, at viewing distances of 40 and 80 cm, Ss reported the apparent depth produced by motion parallax equivalent to a binocular disparity of 0.47°. The mean apparent depth at 80 cm was 2.6 times larger than at 40 cm. In Exp II, again at viewing distances of 40 and 80 cm, Ss adjusted the extent of parallax so that the apparent depth was 7.0 cm. The mean extent of parallax at 80 cm was 31% of that at 40 cm. These findings show that the visual system does calibrate motion parallax according to absolute-distance information in processing depth. In Exp III, distances ranged from 40 to 320 cm, and a wide range of parallax was used. As distance and parallax increased, the perception of a rigid 3-dimensional surface was accompanied by rocking motion; perception of depth was replaced by perception of motion in some trials at 320 cm. Moreover, the mean apparent depths were proportional to the viewing distance at 40 and 80 cm but not at 160 and 320 cm. (25 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The utility of motion parallax information for the perception and control of heading.

Two experiments in which participants were given control over the direction of computer-simulated self-motion were conducted. Environments were designed to evaluate the functionality of simple and multiple motion parallax as well as a separation ratio (?; indexing the separation of 2 objects in depth) for the perception and control of heading. Results provide a 1st indication of optimizing performance in the top end of the global optical flow velocity range available during human bipedal self-motion. The introduction of ?, developed to explain performance improvements with decreasing distance to the target, was able to account for most of the performance differences among all simulated environments. The rate of change in horizontal optical separation between at least 2 discontinuities was identified as a likely candidate for the optical foundation of the perception and control of heading during target approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accuracy and precision of binocular 3-D motion perception.

In principle, information for 3-D motion perception is provided by the differences in position and motion between left- and right-eye images of the world. It is known that observers can precisely judge between different 3-D motion trajectories, but the accuracy of binocular 3-D motion perception has not been studied. The authors measured the accuracy of 3-D motion perception. In 4 different tasks, observers were inaccurate, overestimating trajectory angle, despite consistently choosing similar angles (high precision). Errors did not vary consistently with target distance, as would be expected had inaccuracy been due to misestimates of viewing distance. Observers appeared to rely strongly on the lateral position of the target, almost to the exclusion of the use of depth information. For the present tasks, these data suggest that neither an accurate estimate of 3-D motion direction nor one of passing distance can be obtained using only binocular cues to motion in depth. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of time and frequency manipulation on syllable perception in developmental dyslexics

Many people with developmental dyslexia have difficulty perceiving stop consonant contrasts as effectively as other people and it has been suggested that this may be due to perceptual limitations of a temporal nature. Accordingly, we predicted that perception of such stimuli by listeners with dyslexia might be improved by stretching them in time-equivalent to speaking slowly. Conversely, their perception of the same stimuli ought to be made even worse by compressing them in time-equivalent to speaking quickly. We tested 15 children with dyslexia on their ability to identify correctly consonant-vowel-consonant (CVC) stimuli that had been stretched or compressed in the time domain. We also tested their perception of the same CVC stimuli after the formant transitions had been stretched or compressed in the frequency domain. Contrary to our predictions, we failed to find any systematic improvement in their performance with either manipulation. We conclude that simple manipulations in the time and frequency domains are unlikely to benefit the ability of people with dyslexia to discriminate between CVCs containing stop consonants.     

Discrepancy between self- and observer ratings of performance in social phobics.

28 Ss meeting Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) criteria for social phobia and without comorbid affective disorder and 33 nonclinical controls were asked to present a brief, impromptu speech to a small audience. Speakers themselves, as well as members of the audience, rated each speaker on a public speaking questionnaire that included both specific items (e.g., voice shook) and global items (e.g., appeared confident). For global items, no significant difference was indicated between the 2 groups on observers' ratings of public speaking performance. However, social phobics rated their own performance worse than did nonclinical controls, and there was a significantly greater discrepancy between self and other ratings for social phobics than controls. Fear of negative evaluation was the only significant predictor of the self–other discrepancy on global items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrepancy between the renal pelvic fluctuations and the pacemaker discharges at the pelvi-calyceal border

Experiments were performed in vitro to explore the influence of isoproterenol on the canine pelvi-ureteral system. The rhythmic changes of intrapelvic pressure became no longer manifest and simultaneously recorded electromyograms revealed disappearance of peristalsis at sites distal to the upper region of renal pelvis following application of isoproterenol, while the pacemaker at the pelvi-calyceal border continued to discharge with an enhanced pace. This result has demonstrated that the renal pelvic pressure recorded during treatment with isoproterenol did not reflect the pacemaker activity of the renal pelvis.     

Discrepancy between tau immunoreactivity and argyrophilia by the Bodian method in neocortical neurons of corticobasal degeneration

BACKGROUND: The purpose of this investigation was to identify and characterize abdominal lymphomas as they occur in a large solid-organ-transplant population. METHODS: A large transplant population was isolated, and all patients developing an abdominal lymphoma were identified. These patients were further characterized after review of their medical records and radiologic examinations. RESULTS: Twenty-eight (1%) of 2925 patients developed lymphoma following transplantation. Of these 28 patients, 14 developed abdominal manifestations of disease. Examples of the wide variety of abdominal manifestations of posttransplant lymphoma are presented. Most of these patients had positive titers for Epstein-Barr virus and were treated with cyclosporin as a part of their immunotherapy. The majority of patients died secondary to this aggressive disease process. CONCLUSION: The development of lymphoma following solid organ transplantation is more common than in the general population. One-half of the patients in our study population developed abdominal manifestations of this disease.     

Developmental changes in the interface between perception and memory retrieval.

Four experiments examined how perception affects delayed recognition, visual pop out, and memory reactivation (priming) at 6 mo. Infants discriminated cues (Ls, Ts, and +s) differing in spatial arrangement or number of primitive perceptual units (textons) or both in a delayed recognition task and exhibited adultlike visual pop-out effects in a priming task. Performance at 6 mo resembled that at 3 mo and adult preattentive processing. Unlike at 3 mo, however, at 6 mo, an expectancy-based process overrode the perceptual characteristics of a novel pop-out stimulus in a delayed recognition test. Results indicate that delayed recognition memory becomes more "top down" over the 1st half-year, whereas memory priming remains age invariant and perceptually driven. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the radiologist in breast diagnosis: a surgeon''s personal view

INTRODUCTION: Sedating children can facilitate minor laceration repair by minimizing physical and psychic discomfort. However, some clinicians are reluctant to use sedation, in part because of concern about increased patient charges and fear that the emergency department (ED) stay will be prolonged. The purpose of this study was to determine the extent to which sedative use during the repair of simple facial lacerations in children increased the length of ED stay and patient charges. METHODS: This was a retrospective cohort study of 152 children with small, simple, facial lacerations. Patients with complex lacerations and those requiring specialty consultation were excluded. Patients, at the discretion of the treating physician, received either intramuscular ketamine (n = 14), intranasal or rectal midazolam (n = 38), or no sedation (n = 100). Length of ED stay and the total patient charges were analyzed. RESULTS: Groups were equal with respect to age, sex, and length of the wound. The mean patient time in the ED, from placement in examination room to discharge, was significantly longer for those given ketamine (149+/-37 minutes) and midazolam (98+/-31 minutes) compared with those given no sedation (82+/-28 minutes). Patient charges were also higher in those given ketamine ($695+/-172) or midazolam ($498+/-153) compared with those receiving no sedation ($390+/-86). CONCLUSIONS: The results of this study demonstrate that sedation with ketamine or midazolam increases the length of ED stay compared with using no sedation. However, the increased lengths of stay were modest, particularly for midazolam. Fear of prolonged recovery time should not dissuade clinicians from using either sedative for minor procedures. The patient charges are considerably higher with both midazolam and ketamine, but they may not reflect the actual cost of patient care.     

Interaction between affect and cognition in word perception.

Investigated the hypothesis that the accuracy with which a briefly shown word is perceived depends on both the affective tone of the word and the activation of the corresponding memory code. To increase activation, expectation and word frequency were manipulated. Ss were exposed to a 25-ms flash of a target word. They then chose, from a word pair, the target word. In half the trials, this word pair was given before the flash to create an expectation. Consistent with the hypothesis, when the words were infrequent, accuracy in perception was lower for affective than for neutral words regardless of expectation. When the words were frequent, there was no effect of affective tone in the absence of expectation; in the presence of expectation, accuracy was higher for affective than for neutral words. The valence of the affective words had no effect. Results are interpreted in terms of attentional mechanisms implicated in conscious perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactions between self-motion and depth perception in the processing of optic flow

Moving and acting in a 3D environment requires the perception of its 3D structure. Vision is known to play a crucial role in the control of self-motion, particularly through the changes in the retinal image subsequent to movements of the observer. Reciprocally, signals related to self-motion can also influence our visual perception of 3D space. These interactions between 3D visual perception and self-motion, as demonstrated behaviourally, are now better understood thanks to the development of computational models for processing moving images. They also bear a particular interest in the context of the recent intensive exploration of the inferior parietal lobe (IPL) by neurophysiologists. The IPL is now firmly established as one site of interaction between 3D visual perception and motor control. The parallel between behaviour and neurophysiology leads to a set of crucial, yet unanswered, questions.     

Relation between formant frequencies and optimal octaves in vowel perception

The purpose of this study was to investigate the relation between the traditional concept of formant frequencies and the controversial concept of optimal octaves in the perception of the vowels/i, a, u/. The vowels (produced by a male speaker of General American English) were filtered through eight bandwidths (80-160, 160-315, 315-630, 630-1,250, 1,250-2,500, 2,500-5,000, 5,000-10,000, and 10,000-20,000 Hz) and presented to two groups of subjects. One group performed similarity ratings on pairs of filtered and nonfiltered stimuli; the other identified the individual filtered and nonfiltered vowels. The optimal bandwidths derived from the data of the two groups were compared to the formant frequencies of our speaker, to those reported in the literature, and to the optimal octaves published earlier by other authors. The results showed that there were specific bandwidths which allowed for correct perception and identification of each vowel, and that these bandwidths were compatible with both the optimal octaves and the formant frequencies reported in the literature for each vowel.     

Object manipulation and motion perception: Evidence of an influence of action planning on visual processing.

In 3 experiments, the authors investigated the bidirectional coupling of perception and action in the context of object manipulations and motion perception. Participants prepared to grasp an X-shaped object along one of its 2 diagonals and to rotate it in a clockwise- or a counterclockwise direction. Action execution had to be delayed until the appearance of a visual go signal, which induced an apparent rotational motion in either a clockwise- or a counterclockwise direction. Stimulus detection was faster when the direction of the induced apparent motion was consistent with the direction of the concurrently intended manual object rotation. Responses to action-consistent motions were also faster when the participants prepared the manipulation actions but signaled their stimulus detections with another motor effector (i.e., with a foot response). Taken together, the present study demonstrates a motor-visual priming effect of prepared object manipulations on visual motion perception, indicating a bidirectional functional link between action and perception beyond object-related visuomotor associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)