SEARCH · Search PubMed

Results for “vision transformers”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed1991

[Quantitative evaluation of flicker ERG wave forms in low vision patients].

Flicker ERGs of 30 Hz were recorded for 46 eyes (23 cases) of low vision, including 38 eyes with retinal diseases and 8 eyes with optic neuropathy, and also for 39 normal eyes. The abnormality ratios were compared with regard to (1) the directly measured peak to peak amplitude and pseudo-phase, and (2) the amplitude and phase of fundamental response component (30 Hz) by discrete Fourier transform (DFT). All eyes with optic neuropathy showed normal flicker ERG, while the abnormality ratios of the directly measured pseudophase and the phase by DFT were 60.9% in 28 eyes and 82.6% in 38 eyes with retinal diseases respectively, the difference being statistically significant (P less than 0.05). These findings suggest that DFT for flicker ERG is more useful in quantitative evaluation of the retinal function.

Adolescent↗

PubMed2005

Bezold-Brücke effect in normal trichromats and protanopes.

Luminance-dependent change in color appearance--the Bezold-Brücke effect--was investigated in protanopes and related to that in normal trichromats. Spectral lights were presented at six luminance levels covering mesopic, low, and high photopic vision-across three log steps from 0.76 to 760 Td. To judge color appearance, a variant of the color-naming method was used with four primary basic color terms and a "White" response. This modification enabled us to examine apparent saturation changes along with the Bezold-Brücke hue shift. Color-naming frequency functions were acquired across ten presentations of each stimulus. Since protanopes name colors idiosyncratically, changes in color appearance cannot be quantified directly from the color-naming functions. To circumvent the difficulty, these functions were transformed into color similarity measures for analysis with multidimensional scaling purported to reconstruct individual color spaces. In these, luminance-dependent shifts in color appearance were represented by means of geometric displacements. We found that for normal trichromats, shifts measured in this way agreed with those derived in our study directly, and with the hue shifts reported in earlier studies. For protanopes, contrary to some models of dichromatic vision, changes in color appearance are significant and indicate superimposed shifts in hue and saturation. The results obtained for normal trichromats, especially for protanopes, imply that nonlinearity in the yellow-blue opponent system is insufficient to explain the Bezold-Brücke effect, given the nature of the saturation shift and the demonstrated divergence between unique hues and invariant hues.

Adult↗

PubMed2001

Mechanisms for sensorimotor adaptation to rotated visual input.

Using the multiple-exposure approach, we investigated sensorimotor adaptation by exposing human subjects to different angles of visual rotation in a tracking task. Generally, the tracking error was high at the onset of the visual rotation and gradually declined towards the baseline level during the exposure period. In experiment A, we confirmed that the initial tracking error increases more than proportionally with the angle of rotation. In experiment C, we were unable to confirm intermanual transfer, and attribute this discrepancy with previous literature to details of the experimental tasks. In our main experiment, B, we found that pre-exposure to 45 degrees or 60 degrees of visual rotation facilitated the subsequent adaptation to a 90 degrees rotation, with the facilitatory effect being more pronounced following the 60 degrees rotation. We interpret this finding as evidence that adaptation is achieved by a gradual process, which progresses from small angles of output transformation through intermediate values up to the prescribed angle of rotation.

Adaptation, Physiological↗

PubMed2002

Using sensory weighting to model the influence of canal, otolith and visual cues on spatial orientation and eye movements.

The sensory weighting model is a general model of sensory integration that consists of three processing layers. First, each sensor provides the central nervous system (CNS) with information regarding a specific physical variable. Due to sensor dynamics, this measure is only reliable for the frequency range over which the sensor is accurate. Therefore, we hypothesize that the CNS improves on the reliability of the individual sensor outside this frequency range by using information from other sensors, a process referred to as "frequency completion." Frequency completion uses internal models of sensory dynamics. This "improved" sensory signal is designated as the "sensory estimate" of the physical variable. Second, before being combined, information with different physical meanings is first transformed into a common representation; sensory estimates are converted to intermediate estimates. This conversion uses internal models of body dynamics and physical relationships. Third, several sensory systems may provide information about the same physical variable (e.g., semicircular canals and vision both measure self-rotation). Therefore, we hypothesize that the "central estimate" of a physical variable is computed as a weighted sum of all available intermediate estimates of this physical variable, a process referred to as "multicue weighted averaging." The resulting central estimate is fed back to the first two layers. The sensory weighting model is applied to three-dimensional (3D) visual-vestibular interactions and their associated eye movements and perceptual responses. The model inputs are 3D angular and translational stimuli. The sensory inputs are the 3D sensory signals coming from the semicircular canals, otolith organs, and the visual system. The angular and translational components of visual movement are assumed to be available as separate stimuli measured by the visual system using retinal slip and image deformation. In addition, both tonic ("regular") and phasic ("irregular") otolithic afferents are implemented. Whereas neither tonic nor phasic otolithic afferents distinguish gravity from linear acceleration, the model uses tonic afferents to estimate gravity and phasic afferents to estimate linear acceleration. The model outputs are the internal estimates of physical motion variables and 3D slow-phase eye movements. The model also includes a smooth pursuit module. The model matches eye responses and perceptual effects measured during various motion paradigms in darkness (e.g., centered and eccentric yaw rotation about an earth-vertical axis, yaw rotation about an earth-horizontal axis) and with visual cues (e.g., stabilized visual stimulation or optokinetic stimulation).

Darkness↗

PubMed1995

Cerebral lateralization for the processing of spatial coordinates and categories in left-and right-handers.

Subjects judged whether a tachistoscopially lateralized drawing was identical or different to a drawing seen immediately before in free vision. The drawings depicted natural objects (e.g. animals). On half of the trials the tachistoscopic drawing presented the same objects but either the categorical or the coordinate spatial relations (according to Kosslyn's definitions [23]) between the objects were transformed. In the first experiment 38 right-handed subjects (half males and half females) were tested. Categorical judgements were faster when the match drawing appeared in the right visual field, whereas coordinate judgements were faster when the match drawing appeared in the left visual field. In the second experiment 26 right-handed and 40 left-handed subjects participated. Almost all the subjects were female. Right-handed subjects replicated the findings of the subjects in the first experiment. However, the LHs did not show any difference in response times between spatial conditions and visual fields. These findings support Kosslyn's hypothesis that the left and right hemispheres are specialized respectively for processing categorical and coordinate spatial relations. Moreover, they also suggest that this lateralization pattern is not typical of left-handers.

Adolescent↗

PubMed2006

Co-constructing local meanings for child health indicators in community-based information systems: the UThukela District Child Survival Project in KwaZulu-Natal.

In changing the context regarding the situation of vulnerable children in rural South Africa, understanding the role of communication in the design of community-based child health information systems (HIS) is key. Communication goes beyond language. The importance of translation of terms and concepts used to negotiate between different meanings and logics is explored in this paper. In striving for the 'ideal speech situation' [J. Habermas, Structural Transformation of the Public Sphere, The MIT Press, Cambridge, MA, 1989], or, in other words, creating an enabling environment in which people can participate in debate and discussion on equal terms, there is a need to develop a codetermined vision; to understand local meanings of and for childhood illness; to understand communication systems and the context in which they occur; and to connect with networks beyond the localised setting, such as provincial or national health authorities. We provide a theoretical and practical framework in which important aspects of communication related to IS design can be highlighted and against which the implementation of an IS can be reviewed. The South African case study from the UThukela District Child Survival Project in KwaZulu-Natal, illustrates how this approach was used in co-constructing local meanings for child health indicators in a community-based information system.

Child↗

PubMed2005

Homography-based visual servo regulation of mobile robots.

A monocular camera-based vision system attached to a mobile robot (i.e., the camera-in-hand configuration) is considered in this paper. By comparing corresponding target points of an object from two different camera images, geometric relationships are exploited to derive a transformation that relates the actual position and orientation of the mobile robot to a reference position and orientation. This transformation is used to synthesize a rotation and translation error system from the current position and orientation to the fixed reference position and orientation. Lyapunov-based techniques are used to construct an adaptive estimate to compensate for a constant, unmeasurable depth parameter, and to prove asymptotic regulation of the mobile robot. The contribution of this paper is that Lyapunov techniques are exploited to craft an adaptive controller that enables mobile robot position and orientation regulation despite the lack of an object model and the lack of depth information. Experimental results are provided to illustrate the performance of the controller.

Algorithms↗

PubMed2005

Brush allodynia in hospitalized headache patients.

OBJECTIVE: To describe the incidence and time course of dynamic mechanical allodynia (brush allodynia, BA) in an inpatient headache population. BACKGROUND: Four types of cutaneous allodynia (heat, cold, static mechanical [pressure], and dynamic mechanical [brush] allodynia) can be studied in headache patients. In episodic migraineurs, the development of cutaneous allodynia heralds a change in treatment response. However, little is known about the functional significance of BA, and little is known about the frequency of any type of cutaneous allodynia among patients with chronic or more severe headache disorders. Methods.-The protocol was approved by the institutional review board of our university hospital. A total of 78 subjects were tested for allodynia on days 1, 3, and 5 of an inpatient hospital stay using a 4 x 4 folded gauze pad stroked 10 times at three bilateral sites (forehead, jaw, and forearm). Subjects were queried about the signs and symptoms of their headaches. Headache intensity was graded with a verbal 11-point scale and the intensity of allodynia was graded using a 10 cm visual analog scale. RESULTS: A total of 61 patients had transformed migraine (TM). BA was present at some point during the hospitalization in 32 subjects (41%). Neither age nor duration of daily headache correlated with headache severity. Headache intensity, a history of sensory symptoms or weakness, and subjective blurred vision accompanying the headache correlated with the presence of BA (P< or = .05). Unilateral headaches were more likely to be associated with BA (P = .01), independent of headache severity. When headache was unilateral, BA was greatest ipsilateral to the headache. BA did not influence outcome as measured by length of stay or the likelihood of being discharged headache-free. The rate of decline of headache intensity and allodynia score were similar. CONCLUSION: BA is common in hospitalized headache patients. Subjects with more severe unilateral headaches were more likely to have BA. The presence of BA did not predict treatment failure in an inpatient setting.

Adult↗

PubMed2001

An international human becoming hermeneutic study of Tom Hegg's A cup of Christmas Tea.

This article seeks to contribute to human becoming theory and to nursing by providing an international human becoming hermeneutic study of Thomas Hegg's A Cup of Christmas Tea. The human becoming hermeneutic method was used in this study to discover emergent meanings about human experiences. Guided by the method, the authors discovered three emergent meanings: honoring the cherished; communing with the was, is, and will be; and triumphing with new vision. These meanings were synthesized by the authors. A Cup of Christmas Tea is the story of the way triumphing with new vision arises with honoring the cherished in communing with the was, is, and will be. The conclusion for families and nurses is that by remaining open to all possibilities that exist in each now, moments of serendipitous togetherness can transform human trepidation and negative views of later life.

Humans↗

PubMed2000

The importance of vitamin A in nutrition.

Preformed vitamin A (all-trans-retinol and its esters) and provitamin A (beta-carotene) are essential dietary nutrients that provide a source of retinol. Both retinyl esters and beta-carotene are metabolized to retinol. The retinol-binding proteins on binding retinol provide a means for solubilizing retinol for delivery to target tissues and for regulating retinol plasma concentrations. Oxidation of retinol provides retinal, which is essential for vision, and retinoic acid, a transcription factor ligand that has important roles in regulating genes involved in cell morphogenesis, differentiation, and proliferation. The observations that vitamin A can produce cell and tissue changes similar to those found during neoplastic transformation and that vitamin supplementation can reverse this process indicated a potential role for vitamin A in cancer prevention. Thus far, correlative epidemiological studies on vitamin A use and cancer prevention have produced mixed results, as this review indicates. Apparently, in populations deficient in vitamin A (caused by an inadequate diet or tobacco use), supplementation programs appear to be effective in reducing cancer incidence. In groups already having sufficient dietary or supplemental vitamin A, cancer prevention by added vitamin A may not be particularly effective. The most likely reason for the low efficacy in the latter groups is that feedback mechanisms that increase retinol storage in the liver limit retinol plasma levels; whereas, supplementation at higher doses causes toxicity. In addition to serving as a metabolic source of retinol, beta-carotene, along with other dietary carotenoids, function as antioxidants that can prevent carcinogenesis by decreasing the levels of the free-radicals that cause DNA damage.

Animals↗

PubMed1998

Functional division of the retina and binocular correspondence.

Spatial vision relies on a spatial coding of object directions sensed by the retinal photoreceptors. An empirically measured constant error in this coding of perceived space is described classically as a barrel distortion involving long horizontal lines. A Cartesian retinal coordinate system is constructed to describe the transformation from object space to perceived space. This system establishes a subjective horizontal and vertical (isoelevation and isoazimuth) grid for each eye. The retinal entities that mediate subjective sense of constant elevation (horizontal) and constant azimuth (vertical) constitute the functional division of the retina, and they are described by a model with a single parameter zp, which determines the curvatures of a set of hyperbolic isopters. Empirical isoelevation positions were measured, which were described by this model. The best-fitting zp values appeared to be independent of viewing distance, similar for the two eyes of the same observer but differing significantly among observers. The functional-retinal-division model and horizontal retinal shear, as described by Helmholtz, were used to predict the spatial distributions of binocular corresponding points. The disparity field on a frontoparallel plane at a finite viewing distance showed marked asymmetry between the upper and the lower visual fields. The hyperbolic isoelevation and isoazimuth curves dramatically exaggerated this asymmetry. This theoretical disparity field provides a guideline for experiments that attempt to show the effect of binocular disparity in the periphery.

Humans↗

PubMed2001

The Gaussian derivative model for spatial-temporal vision: I. Cortical model.

How do we see the motion of objects as well as their shapes? The Gaussian Derivative (GD) spatial model is extended to time to help answer this question. The GD spatio-temporal model requires only two numbers to describe the complete three-dimensional space-time shapes of individual receptive fields in primate visual cortex. These two numbers are the derivative numbers along the respective spatial and temporal principal axes of a given receptive field. Nine transformation parameters allow for a standard geometric association of these intrinsic axes with the extrinsic environment. The GD spatio-temporal model describes in one framework the following properties of primate simple cell fields: motion properties, number of lobes in space-time, spatial orientation. location, and size. A discrete difference-of-offset-Gaussians (DOOG) model provides a plausible physiological mechanism to form GD-like model fields in both space and time. The GD model hypothesizes that receptive fields at the first stage of processing in the visual cortex approximate 'derivative analyzers' that estimate local spatial and temporal derivatives of the intensity profile in the visual environment. The receptive fields as modeled provide operators that can allow later stages of processing in either a biological or machine vision system to estimate the motion as well as the shapes of objects in the environment.

Animals↗

PubMed2001

Self-help visions and practices in Germany.

In this article the visions, possibilities and limits of self-help in Germany are discussed and the differences in diagnosis and the modalities of help between the professional culture and a self-help group ("Nachtschwärmer") are shown on the background of cultural transformations and changes within the psychiatric system.

Germany↗

PubMed1996

Implementing comprehensive pharmaceutical services at an academic tertiary care hospital.

The implementation and impact of comprehensive pharmaceutical services at a hospital are described. Before 1992, pharmaceutical services at Detroit Receiving Hospital and University Health Center were comparable to those of many departments serving similar academic tertiary care institutions. A major conflict with the principles of pharmaceutical care existed in that specific tasks were assigned to pharmacists, so that up to four pharmacists may have been involved in one patient's drug therapy while other patients were ignored. Several steps were taken to solve this problem. The department's mission and vision statements were modified to embrace pharmaceutical care. The support of administration and department leaders was secured, pharmacist evaluations were adjusted to make pharmaceutical care skills baseline competencies, and staffing was reconfigured. A voluntary pharmaceutical care committee was formed to transform pharmaceutical services at the hospital. It was decided that all staff pharmacists would provide clinical and distributive services on a rotating basis. The drug distribution system was altered to free more pharmacist time for patient care, and two technician positions were added. The clinical program was made more patient focused. The program was implemented in a stepwise manner beginning in September 1992. Computerized systems for tracking workload and documenting clinical interventions and drug cost savings were established. Later changes included making pharmacists responsible for all patients on a medical service rather than for specific problems in a particular location and changing scheduling to enhance the continuity of care. The number of clinical interventions by pharmacists increased from 3,563 in 1993 to 15,476 (projected) in 1995, and drug cost savings and avoidance increased from $239,248 in 1992 to $562,402 (projected) in 1995. Major change was necessary to implement comprehensive pharmaceutical services at an academic tertiary care hospital.

Cost Savings↗

PubMed1998

The nursing organization and the transformation of health care delivery for the 21st century.

Market transformations occurring within the health care industry require new patterns of organization and management to meet the increasing complexity of service delivery. A greater understanding of the innovation and entrepreneurial dynamic allows administrators, managers, and leaders to create a new vision of service delivery. Central management and leadership objectives include the development of service technologies that capitalize upon the inherent knowledge of workers to meet consumer needs. A strong sense of innovation and entrepreneurship leading to the introduction of new or improved nursing technologies is a primary component in the evolution of professional nursing practice for the 21st century.

Diffusion of Innovation↗

PubMed2006

Spectators & spectacles: nurses, midwives and visuality.

AIM: In this paper we reflect on how linear perspective vision influences the practice of nurses and midwives and to advance understanding of clinical practice in technologically intensive environments through examination of drawings by nurses and midwives and through critical analysis. BACKGROUND: There is increasing emphasis on vision in Western culture, and both nurses and midwives spend a great deal of time observing their clinical environment(s). Healthcare practitioners work increasingly in image-based realities and nurses rely on visual skills. Vision and visual representation are central to our practice and are important to examine because we look often at technology to assess people and care. DISCUSSION: The world in which we practise is one of meaning(s). Technological development is transformative in nature and produces changes that alter the way(s) we give care. Amongst all this change, it is unclear how we practise in environments characterized by increasing technology and it is unknown how nursing and midwifery practice alter as a result. CONCLUSION: Simple drawings included in this paper highlight an important and shared experience of clinical practice(s). They emphasize the importance and scope of the visual sense and expose practitioner behaviour that has enormous implications for current and future professional development and person-focussed care provision. Experiences described in this paper require further examination and highlight substantial changes to nurse-patient relationships, health care and the way we practise.

Attitude of Health Personnel↗

PubMed1995

Frequency characteristics of postural control of children with and without visual impairment.

During quiet standing on a force platform, centre of pressure frequency characteristics of normal and visually impaired children were investigated under four conditions: normal surface, eyes open and closed; foam surface, eyes open and closed. Total power was calculated between 0 and 4Hz. Slopes of logarithmically transformed data were used to compare relative power at high and low frequencies. Younger children had greater total power and relatively more high frequency power. The results suggest that young children (four to six years) do not normally use immediate vision in postural control. Visually impaired children have greater instability than sighted children, with greatest differences between the two groups at 10 to 12 years.

Age Factors↗

PubMed2006

Transplantable retinal pigment epithelial cell sheets for tissue engineering.

The native retinal pigment epithelium (RPE) exists as a monolayer structure and is critically involved in the maintenance of photoreceptors. Damage or destruction of the RPE due to a variety of diseases therefore often results in loss of vision. With regenerative purposes in mind, we have examined various culture conditions such as the initial cell density and the addition of various supplements in an effort to produce transplantable RPE cell sheets that can be harvested without defects. We demonstrate that the cell density in cultured RPE sheets increased linearly with the number of seeded cells and that RPE sheets were harvested without defects and limited contraction due to cytoskeletal reorganization, when TGF-beta2 was added to the growth medium. Results from histological analysis and the measurement of trans-epithelial resistance also demonstrates that these RPE cell sheets exist as monolayer structure, similar to the native RPE, with intact cell-to-cell junctions. Therefore, these methods provide significant insight into the fabrication of transplantable RPE cell sheets that can be applied to RPE regenerative therapies to restore lost vision.

Cell Count↗