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At least 415 records · Page 23Linked to original sources
PubMed2005

Staring in the eye of auditory neglect: comments on 'gaze direction modulates auditory spatial deficits in stroke patients with neglect'.

In the current issue of Cortex, Pavani and colleagues show that directing gaze toward the contralesional hemifield significantly diminishes the auditory deficits associated with unilateral neglect. The authors suggest that this beneficial effect of gaze direction may arise due to the recruitment of crossmodal attentional links between audition and vision. A complementary interpretation of these findings is that directing gaze toward neglected sound sources encourages the recoding of auditory spatial location in a relatively preserved frame of reference, and that it is through this coordinate transformation process that awareness of auditory stimuli may be regained. Rehabilitation strategies aimed at recoding stimuli within relatively preserved reference frames may be a useful step forward in managing unilateral neglect.

Attention↗
PubMed1999

Remodelling colour contrast: implications for visual processing and colour representation.

Colour contrast describes the influence of one colour on the perception of colours in neighbouring areas. This study addresses two issues: (i) the accurate representation of the colour changes; (ii) the underlying visual mechanisms. Observers viewed a haploscopic display in which a standard display was presented to one eye and a matching display to the other. The matches could be represented accurately using a diagram that is a logarithmic transformation of the MacLeod-Boynton (r, b) (1979) chromaticity diagram. Since haploscopic presentation has been described as isolating retinal processes (Whittle, P., & Challands, P.D.C. (1969). The effect of background luminance on the brightness of flashes. Vision Research, 9, 1095-1110; Chichilnisky, E.J., & Wandell, B.A. (1995). Photoreceptor sensitivity changes explain color appearance shifts induced by large uniform backgrounds in dichoptic matching. Vision Research, 35, 239-254), the results are discussed in terms of receptor sensitivity changes and the ratio of receptor contrasts.

Adult↗
PubMed1987

Computer automated cell size and shape analysis in cryomicroscopy.

Computer vision techniques have been developed for quantitative analysis of size and shape changes in cells frozen on a cryomicroscope. The analysis is based on implementation of standard serial edge detection algorithms in conjunction with a shape transform to isolate individual cells in complex scenes which may include adjacent and overlying ice crystals. In the present study the sensitivity of the automated analysis procedure is evaluated for images obtained by various microscope optical systems for progressive degrees of subject blurring by defocusing. Size measurements in calibration trials for freezing latex spheres with extracellular ice in the field of view were least sensitive for bright field images, although the most consistent data was obtained by differential interference contrast microscopy. In all cases phase contrast images produced the least accurate data. An example analysis is presented for the freezing of pancreas beta-cells.

Algorithms↗
PubMed1996

Visuomotor modules in the vertebrate brain.

Most accounts of vision assume that its function is largely perceptual, providing an internal model or representation of the external world that serves as the visual foundation for thought and action. However, the evolutionary origins of vision are not representational. Vision evolved not to provide perception of the world but to provide distal control of the many different movements that animals make. Moreover, many of these visuomotor control systems are quite modular in their input-output organization. In humans and other primates, these visuomotor modules function quite independently from the neural mechanisms mediating perception-based knowledge of the world. This division of labour between action systems and perception systems can be seen in the organization of the visual pathways in the primate cerebral cortex. The ventral stream of projections from striate cortex to inferotemporal cortex is critical to the visual perception of objects and is intimately connected with the cognitive operations, while the dorsal stream projecting from striate cortex to the posterior parietal region is essential for the required visuomotor transformations for the on-line control of skilled actions directed at those objects. The perceptual representations constructed by the ventral stream allow us to select a particular course of action with respect to objects and events in the world; the visuomotor transformations carried out by the dorsal stream allow us to program and direct any visually guided movements that are required to carry out that course of action. Thus, to understand the organization of the visual system(s), it is necessary to understand the requirements of the different output systems that vision serves.

Animals↗
PubMed2001

Sapir's vision of culture and personality.

For Edward Sapir the concept of culture was a reification of processes that were rooted in individuals' personality and psychology. Sapir suggested that psychiatry's focus on individual biography and pathology gives it unique relevance for social science efforts to understand the mechanisms of cultural transmission and transformation. As a discipline that must integrate culture and biology in theory and practice, psychiatry can provide a corrective to the extremes of biological or cultural reductionism. Although mainstream psychiatry has largely abdicated the role it once had in the social sciences, the interdisciplinary field of cultural psychiatry may meet some of Sapir's hopes. Recent work in cultural psychiatry is centrally concerned with illness narratives that arise from the interaction of personal and collective meaning. Illness narratives may serve individual defensive functions, position individuals in a social world, and help to maintain overarching cultural formations. They also may challenge or subvert existing cultural meanings and create new forms of discourse. The close analysis of how cultural and individual meanings interact that is provided by cultural psychiatry has much to offer the wider field of cultural anthropology.

Anthropology, Cultural↗
PubMed1985

Incidence of dysplasia, carcinoma in situ and invasive carcinoma in colposcopic findings of atypical re-epithelization zone (A.R.Z.) and atypical transformation zone (A.T.Z.).

The Authors report their experience on 5518 colposcopic examinations and consider especially the findings of A.R.Z. and A.T.Z. and the correlation with cytologic and histologic aspects. They found a significant incidence of CIN (I, II, III) and invasive carcinoma by means of association of directed punch biopsies under colposcopic vision. Finally the importance of histological examination also in presence of negative cytologic findings is evidenced.

Adolescent↗
PubMed2004

Isoform-specific changes in scleral transforming growth factor-beta expression and the regulation of collagen synthesis during myopia progression.

The development of high myopia is associated with altered scleral extracellular matrix biochemistry. Previous studies highlight the importance of collagen turnover in this process, yet it is unclear which factors control scleral remodeling. This study used a mammalian model of myopia to investigate the capacity of TGF (transforming growth factor)-beta1, -beta2, and -beta3 to influence scleral remodeling in myopia. RT-PCR confirmed the presence of all mammalian TGF-beta isoforms in scleral tissue and scleral fibroblasts. Myopia was experimentally induced via monocular deprivation of pattern vision, and animals were allocated to two groups depending on the duration of treatment (1 or 5 days). Down-regulation of each isoform was apparent after only 1 day of myopia development (TGF-beta1, -32%; TGF-beta2, -27%; TGF-beta3, -42%). Whereas the decrease in TGF-beta1 and -beta3 expression was relatively constant between the two time points, differential down-regulation of TGF-beta2 was found between days 1 (-27%) and 5 (-50%). In vitro experiments, using primary scleral fibroblasts, demonstrated the capacity of all isoforms to increase collagen production in a dose-dependent manner. Changes in TGF-beta levels, which mimicked those during myopia induction, caused an approximately 15% reduction in collagen synthesis, which is qualitatively similar to those previously reported in vivo. These data represent the first demonstration of TGF-beta3 expression in the sclera and implicate all three TGF-beta isoforms in the control of scleral remodeling during myopia development. In addition, the early alterations in TGF-beta expression levels may reflect a role for these cytokines in mediating the retinoscleral signal that controls myopic eye growth.

Animals↗
PubMed2001

Human multisensory fusion of vision and touch: detecting non-linearity with small changes in the sensory environment.

Previous investigations using relatively large amplitude sensory stimuli or complete removal of sensory input have demonstrated non-linear processing of sensory information for postural control. In the present study, we asked whether a linear range of sensory fusion exists when smaller amplitude stimuli are used. The amplitudes of visual and somatosensory input were simultaneously co-varied within a trial. The postural responses were characterized by analyzing how the Fourier transform of postural sway at the driving frequency varied with sensory movement amplitudes. If the postural control system is linear with constant weighting of sensory inputs, then the pattern of Fourier transforms should be a linear function of movement amplitude. However, in 28 of 58 trials we observed non-linearity in this function. The results clearly show that even at very small amplitudes of sensory change, the nervous system processes multisensory information in a non-linear fashion.

Fourier Analysis↗
PubMed1998

Determining the similarity of deformable shapes.

Determining the similarity of two shapes is a significant task in both machine and human vision systems that must recognize or classify objects. The exact properties of human shape similarity judgements are not well understood yet, and this task is particularly difficult in domains where the shapes are not related by rigid transformation. In this paper we identify a number of possibly desirable properties of a shape similarity method, and determine the extent to which these properties can be captured by approaches that compare local properties of the contours of the shapes, through elastic matching. Special attention is devoted to objects that possess articulations, i.e. articulated parts. Elastic matching evaluates the similarity of two shapes as the sum of local deformations needed to change one shape into another. We show that similarities of part structure can be captured by such an approach, without the explicit computation of part structure. This may be of importance, since although parts appear to play a significant role in visual recognition, it is difficult to stably determine part structure. We also show novel results about how one can evaluate smooth and polyhedral shapes with the same method. Finally, we describe shape similarity effects that cannot be handled by current approaches.

Algorithms↗
PubMedDate not supplied

[Orbital pseudotumour imitating a proliferative process].

INTRODUCTION: Orbital pseudotumour is a non-specific inflammatory process of the orbit of unknown origin. It is a rarely diagnosed disease particularly in children, which imitates a neoplastic process. Typical clinical picture is a tumour localized in the orbit, causing various degree of exophtalmus and a decrease of globe mobility and vision. The extent of intraorbital changes are revealed by imaging studies (USG, TK, MR). Diagnosis is based on histopathology of tumour sample. In treatment steroid therapy, radiotherapy or chemotherapy in resistant cases are used. Relapse and malignant transformation are observed. CASE REPORT: We present a case of a 5-years old girl with orbital pseudotumour. In the histopathological examination there a small lymphoid cells, immunohistochemically there is mixed lymphocytic T and B infiltration (CD 3 (+), CD 20 (+), bcl (+), CD 43 (-)). She was treated with steroid therapy, and achieved complete regression of the tumour. At present she is regularly oncologically examined because of the possibility of malignant transformation. CONCLUSIONS: 1. Orbital pseudotumour should be included in the differential diagnosis of children with an orbital tumour 2. Corticosteroids seem to be the treatment of choice in orbital pseudotumour 3. Children with orbital pseudotumour should be regularly oncologically examined because of the possibility of malignant transformation.

Child↗
PubMed1980

Spatial characteristics of movement detection mechanisms in human vision. I. Achromatic vision.

Threshold illumination levels, It, for visual detection of white light targets, moving across spatially structured background fields, have been measured and it is shown that, for a given background illumination level, It depends upon the spatial characteristics of the background field structure. Thus, with the background composed of a square-waveform grating of fundamental spatial frequency f cycles/deg, It is maximum for an intermediate value of f, and falls as f increases or decreases from this value. The relationship between It and f characterizes the interaction between movement detection and the background grating, and is designated the IMG function. The parametric properties of the IMG functions are described and it is established that the mechanisms which give rise to these functions are sensitive to the movement, but not the spatial structure of the target. They correspond, therefore, to the movement-sensitive Y-type mechanisms, observed in electrophysiological studies of cat and primate visual pathways. The spatial distribution of sensitivity associated with the IMG functions has been computed by 2-D transform methods, the computation yielding circularly symmetric, centre-surround antagonistic "receptive field" distributions.

Adult↗
PubMed2005

Selectivity and sparseness in the responses of striate complex cells.

Probability distributions of macaque complex cell responses to a large set of images were determined. Measures of selectivity were based on the overall shape of the response probability distribution, as quantified by either kurtosis or entropy. We call this non-parametric selectivity, in contrast to parametric selectivity, which measures tuning curve bandwidths. To examine how receptive field properties affected non-parametric selectivity, two models of complex cells were created. One was a standard Gabor energy model, and the other a slight variant constructed from a Gabor function and its Hilbert transform. Functionally, these models differed primarily in the size of their DC responses. The Hilbert model produced higher selectivities than the Gabor model, with the two models bracketing the data from above and below. Thus we see that tiny changes in the receptive field profiles can lead to major changes in selectivity. While selectivity looks at the response distribution of a single neuron across a set of stimuli, sparseness looks at the response distribution of a population of neurons to a single stimulus. In the model, we found that on average the sparseness of a population was equal to the selectivity of cells comprising that population, a property we call ergodicity. We raise the possibility that high sparseness is the result of distortions in the shape of response distributions caused by non-linear, information-losing transforms, unrelated to information theoretic issues of efficient coding.

Animals↗
PubMed2005

Retained antibiotic ophthalmic ointment on an intraocular lens 34 months after sutureless cataract surgery.

PURPOSE: To quickly examine the long-term retained oily-like material on the intraocular lens (IOL) of a sutureless cataract surgical patient. DESIGN: Observational case report. METHODS: Fourier transform infrared (FT-IR) and confocal Raman microspectroscopies were used to identify the deposited materials on explanted IOL. RESULTS: A 70-year-old man underwent a sutureless cataract surgery for his right eye. Garamycin ophthalmic ointment was postoperatively applied on the conjunctival fornix. His vision was improved to 20/25 after surgery but declined gradually to 20/400 half a year later. An oily-like hump on the anterior surface of IOL was found and he underwent IOL exchange after approximately 3 years. The oily-like material was identified by using FT-IR and Raman microspectroscopies to be garamycin ophthalmic ointment. CONCLUSIONS: Both FT-IR and Raman microspectroscopies can easily examine the retained antibiotic ophthalmic ointment on the IOL. Direct access of ophthalmic ointment into ocular anterior chamber through the sutureless incision is a potential risk.

Aged↗
PubMed1995

Vision thresholds from psychometric analyses: alternatives to probit analysis.

Vision scientists and clinicians regularly obtain measures of vision and determine a person's vision threshold by choosing one of numerous methods of analysis. Analytical methods differ in their presumptions about the measures, in their complexity and in the ease of obtaining the threshold estimate. In light of these differences among so-called methods of psychometric analysis, the question is, "Do various analytical methods provide essentially equivalent vision threshold estimates or are there consequential differences that require consideration?" Measures of visual acuity, motion processing, and texture processing were obtained from 20 subjects. Each set of measures was analyzed by five psychometric methods: Logit Analysis, Normit Analysis, and linear regression of z-score transformed, logit transformed and untransformed probabilities vs. stimulus strength. The resulting thresholds were compared to the threshold obtained from Probit Analysis, which was used as a reference or "gold standard." Thresholds from the procedures were remarkably similar to those from Probit Analysis. In addition, examination of the speed of the procedures revealed that Probit Analysis was up to 10 times slower than some of the others. Considering the similarity of thresholds, the speed of computation, and the ease of implementation, Logit and Normit Analyses especially provide effective alternatives to the current gold standard, Probit Analysis, for the estimation of psychometric thresholds. In addition, z-score, logit, and linear regressions also produced unbiased threshold estimates under many circumstances, but the latter method should be applied with some caution.

Algorithms↗
PubMed2001

Developmental lesions of visual cortex influence control of reaching.

We examined visually guided reaching movements in a young adult (EW) who had extensive bilateral lesions in the visual cortex since birth. EW lacked a right occipital lobe and ventral portions of the left and had poor visual acuity (3/400), yet could point to visual targets as quickly as 9 controls with visual cortex lesions acquired in adulthood and 4 adults without neurological disease. However, EW's endpoint variability and hand movement path curvature were much greater, especially for left hand movements, in concert with large sensorimotor transformation errors. Experimental reduction of acuity (to 3/240 or worse) in the normal controls produced symmetric increases in endpoint variability but did not change hand path curvature, indicating that EW's impaired movements were not due to poor vision alone. Results suggest that visual cortex in early life supports the development of lifelong neural mechanisms for the planning and control of reaching movements.

Adult↗
PubMedDate not supplied

Evidence for processing stages in skill acquisition: a dual-task study.

We investigated the changes of resource demand during the acquisition of a sensorimotor skill, namely the tracking of a visual target under reversed visual feedback. This acquisition task was performed alone or concurrently with one of four manual reaction-time tasks as loading tasks, designed to tap different computational resources. As expected, we found tracking performance to deteriorate upon vision reversal and then to gradually improve with practice. We further found that acquisition task and loading task interfered little before vision reversal but substantially afterwards. Most importantly, we observed a different time-course of interference for each of our four loading tasks. The particular pattern led us to conclude that resources related to spatial attention and sensory transformations are in highest demand early during skill acquisition and those pertinent to movement preparation somewhat later. Our findings thus provide experimental support for the theory that motor learning progresses in stages characterized by different resource requirements.

Adult↗
PubMed2003

Multisensory integration during motor planning.

When planning goal-directed reaches, subjects must estimate the position of the arm by integrating visual and proprioceptive signals from the sensory periphery. These integrated position estimates are required at two stages of motor planning: first to determine the desired movement vector, and second to transform the movement vector into a joint-based motor command. We quantified the contributions of each sensory modality to the position estimate formed at each planning stage. Subjects made reaches in a virtual reality environment in which vision and proprioception were dissociated by shifting the location of visual feedback. The relative weighting of vision and proprioception at each stage was then determined using computational models of feedforward motor control. We found that the position estimate used for movement vector planning relies mostly on visual input, whereas the estimate used to compute the joint-based motor command relies more on proprioceptive signals. This suggests that when estimating the position of the arm, the brain selects different combinations of sensory input based on the computation in which the resulting estimate will be used.

Adult↗
PubMed1994

Transforming a hospital facility company into an integrated medical care organization.

This article outlines the steps a major integrated health delivery system in Chicago has undertaken to transition from a primarily hospital-based fee-for-service organization to an integrated medical care organization operating under full-risk capitation. The focus is on vision setting, building a foundation for change, structural building blocks, network building steps, and lessons learned to date.

Capitation Fee↗