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PubMedDate not supplied

Digital vision theory: Boolean logic model.

Guild (1932) stated the general requirements for processing signals in color vision system and a digital format of his paradigm is developed in this paper. The disk structure generates the digital receptor pulse. The input modalities form sets, linked by intersections, joins, and complement junctions. The synapses are elements in these junctions. Complex synapses form complex junctions to create Boolean logic processing. A computer program using these Boolean logic functions calculates: Light and dark adaptation responses; Color matching and spectral coordinate functions; Chromatic adaptation and color shift responses; and dynamic neural responses. These calculations compare favorably with the experimental data.

Adaptation, Physiological↗

PubMedDate not supplied

Development of stereoscopic acuity: longitudinal study using a computer-based random-dot stereo test.

PURPOSE: To investigate the development of stereoscopic acuity (stereoacuity) in children longitudinally. METHODS: Seven full-term normal infants whose age at the beginning of the study was between 12 and 23 weeks were studied. A computer-based random-dot test of stereoscopic vision (TV-Random Dot Stereo Test) was used to measure stereoacuity. The test was repeated at 2- to 3-month intervals until the children reached 2 years of age, and then every 6 to 12 months until they reached 5 years of age. RESULTS: All of the infants were found to have a stereoacuity of 2480 seconds of arc (2480'') with this test by 26 weeks of age. The first reliable measurement of stereoacuity was obtained from a 16-week-old infant. Stereoacuity did not improve significantly between 6 and 12 months, but it improved rapidly after 12 months. All children had a stereoacuity of 100'' with the Titmus Stereo Tests at 5 years of age, but the best stereoacuity with the TV-Random Dot Stereo Test was 229'' at 28.9 months. CONCLUSIONS: The development of stereoacuity studied longitudinally was similar to that obtained by cross-sectional studies. The TV-Random Dot Stereo Test is a useful program for measuring stereopsis in preverbal children.

Child Development↗

PubMed1988

Optic nerve decompression.

Post-traumatic deterioration of vision requires thorough ophthalmologic evaluation, as well as computed tomographic scanning of the orbits and central visual pathways if no obvious ocular origins of the visual decrement are detected. When optic nerve trauma is a suspected etiology, the patient should be treated with megadose intravenous steroids, as well as optic nerve decompression performed after 12 to 24 hours if improvement of vision fails to occur.

Craniocerebral Trauma↗

PubMed1989

Optic gliomas in children with neurofibromatosis type 1.

To determine the frequency and natural history of tumors of the optic nerves and chiasm in patients with neurofibromatosis type 1, we obtained computed tomographic scans of 65 children who had no known visual or ocular abnormalities before their initial evaluation. Optic gliomas were detected in 10 children (15%). The median age of children with gliomas was 4.3 years (mean 5.8 years, range 9 months to 21 years). Three children (30%) had isolated, unilateral tumors, three (30%) had bilateral tumors, and four (40%) had involvement of the optic chiasm and of one or both nerves. Definite abnormalities of vision were found in only two children (20%). Five additional children were referred to the clinic after evaluation of ophthalmologic complaints led to the diagnosis of neurofibromatosis type 1: three had unilateral exophthalmos and two had plexiform neurofibromas of the eyelid with associated glaucoma. Ipsilateral optic gliomas were found in all five children; one child also had a contralateral tumor. Optic gliomas are commonly identified in young children with neurofibromatosis type 1 who have no ocular or visual abnormalities. Optic nerve gliomas may be associated with plexiform neurofibromas of the eyelid and glaucoma.

Adolescent↗

PubMed2000

Nonhomogeneous resolution of images of natural scenes.

The aim of this research is to model and simulate the loss of visual resolution as a function of retinal eccentricity in the perception of natural scenes. The model of visual resolution is based on a space-variant low-pass filter, having a variable convolution kernel according to retinal eccentricity. The parameters of the model are computed from psychophysical measures of visual acuity as a function of retinal eccentricity. The implementation of the model allowed us to generate images of scenes with nonhomogeneous space-variant resolution, simulating the filtering executed by the eye. These scenes are used to test and optimise the model by means of experiments in static vision (through tachistoscopic presentations) and in dynamic vision where the resolution of the scene is computed, in real-time, as a function of the location of gaze.

Contrast Sensitivity↗

PubMed1992

Information industry leaders share visions of future. Interview by Carolyn Dunbar and Michael L. Laughlin.

Computers in Healthcare editors Carolyn Dunbar and Michael L. Laughlin spoke to nearly a hundred exhibitors during the 1992 Healthcare Information and Management Systems Society last February in Tampa, Fla. The themes of these conversations invariably turned to patient-focused systems, standards, integration and, of course, controlling healthcare costs. Many HIMSS participants offered valuable insights, and unfortunately space does not permit us to run every interview. In the following interviews, however, three industry leaders share visions of where their companies--and the industry--are headed.

Attitude of Health Personnel↗

PubMed1997

Physiological computation of binocular disparity.

We previously proposed a physiologically realistic model for stereo vision based on the quantitative binocular receptive field profiles mapped by Freeman and coworkers. Here we present several new results about the model that shed light on the physiological processes involved in disparity computation. First, we show that our model can be extended to a much more general class of receptive field profiles than the commonly used Gabor functions. Second, we demonstrate that there is, however, an advantage of using the Gabor filters: similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity. Third, we prove that the complex cells as described by Freeman et al. compute disparity by effectively summing up two related cross products between the band-pass filtered left and right retinal image patches. This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as few as two complex cells at each spatial location are sufficient for a reasonable estimation of binocular disparity. Fifth, we find that our model can be significantly improved by considering the fact that complex cell receptive field are, on average, larger than those of simple cells. This fact is incorporated into the model by averaging over several quadrature pairs of simple cells with nearby and overlapping receptive fields to construct a model complex cell. The disparity tuning curve of the resulting complex cell is much more reliable than the constructed from a single quadrature pair of simple cells used previously, and the computed disparity maps for random dot stereograms with the new algorithm are very similar to human perception, with sharp transitions at disparity boundaries. Finally, we show that under most circumstances our algorithm works equally well with either of the two well-known receptive field models in the literature.

Algorithms↗

PubMed2004

Techniques for radiofrequency ablation of head and neck tumors.

OBJECTIVES: To describe the various techniques that have been developed for application of radiofrequency ablation in the palliative treatment of recurrent and advanced head and neck malignant tumors. DESIGN: Case series with a follow-up of 3 to 18 months. SETTING: Faculty practice, research protocol, tertiary care academic medical center. PATIENTS: Fifteen treatments were administered over a 3-year period to 12 patients with advanced and/or recurrent tumors. Eleven tumors were squamous cell carcinomas of the oral cavity, oropharynx, and maxillary sinus, and 1 tumor was a medullary thyroid carcinoma. Three of the 12 patients were treated on 2 separate occasions. Patients were selected as a referred sample and sent specifically for treatment with radiofrequency ablation because they were not candidates for the standard curative options of radiation or surgery. No patient refused enrollment, nor were any patients withdrawn because of adverse events. INTERVENTION: Radiofrequency ablation is a method of localized hyperthermia resulting in tissue necrosis. Ninety to 150 W of energy is applied, achieving intratumoral temperatures of 60 to 110 degrees C for 5 to 15 minutes per ablation. Techniques have been developed to apply radiofrequency ablation under direct vision, endoscopically, percutaneously, and with ultrasound and computed tomographic guidance. RESULTS: The radiofrequency ablation probe was accurately placed and treatment administered on 15 occasions. No perioperative deaths occurred. One patient suffered a stroke. Subjective patient improvement was reported with regard to pain (n=9), appearance (n=3), and function (n=4).

Aged↗

PubMed1991

Gastrin-releasing peptide gene products in midtrimester human fetal lung with and without maternal smoking history during pregnancy.

A preliminary morphological study on human fetal lungs with positive maternal smoking history demonstrated alterations of the neuroepithelial bodies (NEBs). We studied human fetal lung tissue between the gestational ages of 12 weeks and 19 weeks, comprising 12 cases with a smoking history during pregnancy (Group 1) and eight cases without a smoking history during pregnancy (Group 2). We demonstrated, by immunocytochemistry, the presence of gastrin-releasing peptide (GRP) gene products: GRP 14-27 in all 20 cases, and C terminal peptide of pro-GRP (C-flanking peptide) in 17 cases. Quantification of the neuroepithelial cells (NECs) was made by computer-enhanced image analysis using the Context Vision system, expressing 1) the total stained areas of the NECs per unit area of section and 2) the total staining areas of the NECs per unit area of airway epithelium, measured as the area of cytokeratin immunoreactivity in an adjacent section. The results show no statistically significant difference between groups 1 and 2 for either GRP 14-27 or C-flanking peptides. The apparent lack of influence of maternal smoking during pregnancy on the expression of GRP gene products in the NECs could be a reflection of inherently reduced reactivity of the cells during the gestation period studied. However, a larger series is needed before any conclusions can be made. Alternatively, the adverse effects of smoking might be reflected during the canalicular phase of lung development; an increased immunoreactivity appears to be present during that period. The expression of pro-GRP gene products in the pulmonary NECs of older fetuses and neonates with maternal smoking history during pregnancy requires further study.

Female↗

PubMed1996

Speed estimates from grating patches are not contrast-normalized.

We have previously shown that the perceived speed of a moving grating depends upon its contrast, with lower-contrast patterns appearing to move more slowly than otherwise identical higher-contrast patterns. To explain this finding while remaining consistent with the findings of McKee, Silverman and Nakayama [(1986) Vision Research, 26, 609-619], we proposed that this misperception might arise from a modified version of the contrast-normalization procedure, envisaged by Adelson and Bergen [(1986) The extraction of spatio-temporal energy in human and machine vision (pp. 135-139). Charleston, S.C.: IEEE Computer Society] as a necessary second stage of motion-energy models of human motion processing. Specifically, our previous results might be explained if the two gratings to be compared interfered with each other's normalization. To test this hypothesis we performed two experiments. Experiment 1 demonstrates that the contrast effects persist even when two grating patches to be compared are presented up to 5 sec apart so that they would not be expected to bias each other's normalization. Experiment 2 shows that the contrast effects are unchanged when the two grating patches are surrounded by a range of patterns whose contrast would be expected to interfere with any normalization process. These two results allow the rejection of the contrast-normalized motion-energy hypothesis as an explanation of human speed perception. We discuss the consequences of these results on models of speed processing in the human visual system.

Contrast Sensitivity↗

PubMed2004

Parasagittal meningioma en plaque with extracranial extension presenting diffuse massive hyperostosis of the skull.

BACKGROUND: We describe a case of convexity meningioma en plaque (MEP) invading the skull and scalp with diffuse massive hyperostosis, presenting striking radiological findings. CASE DESCRIPTION: A 48-year-old woman was admitted to our hospital with headache, general fatigue, diplopia, and blurred vision. A skull X-ray film, computed tomography (CT), and 3-dimensional CT demonstrated diffuse significant hyperostosis and sclerosis in the cranial vault. Magnetic resonance (MR) imaging revealed a frontoparietal, well-enhanced extra-axial mass lesion, which is compatible with findings of MEP. The tumor was partially resected. Histological examination revealed massive tumor invasion into the dura mater, hyperostotic skull, and scalp. CONCLUSION: Hyperostosis is frequently observed in MEP, although there has been no report of a case of MEP such as ours demonstrating diffuse tumor extension and diffuse hyperostosis. Analyzing the CT finding of hyperostotic bone is useful for differentiation of MEP from other diseases that include a hyperostotic condition.

Atrophy↗

PubMed2002

Adaptation to changes in vertical display gain during handwriting in Parkinson's disease patients, elderly and young controls.

Parkinson's disease (PD) patients, matched elderly controls, and normal young subjects were tested using a visuo-motor adaptation paradigm in which the gain of the vertical component of the visual feedback of handwriting was manipulated in real-time. Handwriting was performed on a digitizer tablet and displayed in real-time on a computer screen in front of the participant. Vision of the hand and pen was occluded. Feedback could be normal (pre- and post-exposure conditions), smaller, or larger than the actual handwriting (exposure conditions). All groups showed a gradual adaptation that compensated for the distorted visual feedback during the exposure conditions. Moreover, all the groups showed significant after-effects during the post-exposure conditions suggesting that all the participants learned to compensate for the novel display gains. Taken together, these data suggest that the mechanisms for visuo-motor adaptation to changes in vertical display gain during handwriting are robust to aging and early stage of PD. These results may have implications for the treatment of micrographia in Parkinsonism.

Adaptation, Psychological↗

PubMed1994

Temporary unilateral amaurosis with pneumosinus dilatans of the sphenoid sinus.

Pneumosinus dilatans (PSD), first described by Meyes in 1898, is an abnormal dilatation of one or more of the paranasal sinuses without bony erosion. The term sinus pneumocele indicates the presence of bony erosion. Review of the literature from 1968 to 1992 revealed 24 cases of idiopathic PSD and 17 cases of pneumocele of various paranasal sinuses. PSD occurred most commonly in the frontal sinus. Males were more often affected than females. The average age for males ranged from 16.5 for the maxillary sinus to 35.5 years for the sphenoid sinus. Pneumoceles occurred most commonly in the maxillary sinus. The average age for males ranged from 29 years for the frontal sinus and 47 years for the ethmoid sinus. Two patients (1 pneumocele and 1 PSD) had a temporary loss of vision. We report the case of a 37-year-old mountain climber who experienced temporary loss of vision in his left eye above 3000 m. Vision returned below 2000 m. High resolution computed tomography scan revealed pneumosinus dilatans of the sphenoid sinus with dehiscence of the optic canal on the left side. Endonasal microendoscopic resection of the anterior wall of the left sphenoid sinus was performed. The patient has remained symptom-free after 2 years of follow-up. Pneumosinus dilatans should always be considered in the differential diagnosis of sudden visual loss associated with atmospheric pressure changes.

Case Reports↗

PubMed1999

Cerebral phaeohyphomycosis caused by Ramichloridium obovoideum (Ramichloridium mackenziei): case report.

OBJECTIVE AND IMPORTANCE: Only a few cerebral infections with the dark-walled mold Ramichloridium obovoideum (Ramichloridium mackenziei) have been reported in the literature. Central nervous system infections caused by this fungus have poor prognoses; the optimal medical and surgical treatments have not yet been established. We report a case of cerebral R. obovoideum infection for which a combination of medical and surgical treatments failed. CLINICAL PRESENTATION: A 58-year-old Kuwaiti woman, with a history of chronic renal failure requiring hemodialysis, presented with a 3-day history of left frontal headache, blurry vision, dizziness, and right-sided clumsiness. Computed tomography demonstrated multiple, ring-enhancing, cerebral lesions (the largest of which measured 2-3 cm) in the deep left parieto-occipital region. INTERVENTION: A computed tomography-guided needle biopsy of the parieto-occipital lesion yielded 10 ml of dark caseous fluid. Stains demonstrated long, branching, septate hyphae. Fungal cultures grew R. obovoideum. The patient was treated with a combination of amphotericin B and itraconazole. The condition of the patient continued to deteriorate, and stereotactic aspiration of the largest lesion was performed. Despite this approach, the lesion progressed and the patient died. CONCLUSION: R. obovoideum is being increasingly recognized as a cause of cerebral abscesses in patients residing in the Middle East. Prognoses are poor, and responses to antifungal therapy are generally short-lived. Until more effective therapies are found, the greatest chance for adequate treatment involves early recognition, prompt treatment with antifungal agents, and attempts at complete resection.

Amphotericin B↗

PubMed2006

Symbolic signatures for deformable shapes.

Recognizing classes of objects from their shape is an unsolved problem in machine vision that entails the ability of a computer system to represent and generalize complex geometrical information on the basis of a finite amount of prior data. A practical approach to this problem is particularly difficult to implement, not only because the shape variability of relevant object classes is generally large, but also because standard sensing devices used to capture the real world only provide a partial view of a scene, so there is partial information pertaining to the objects of interest. In this work, we develop an algorithmic framework for recognizing classes of deformable shapes from range data. The basic idea of our component-based approach is to generalize existing surface representations that have proven effective in recognizing specific 3D objects to the problem of object classes using our newly introduced symbolic-signature representation that is robust to deformations, as opposed to a numeric representation that is often tied to a specific shape. Based on this approach, we present a system that is capable of recognizing and classifying a variety of object shape classes from range data. We demonstrate our system in a series of large-scale experiments that were motivated by specific applications in scene analysis and medical diagnosis.

Algorithms↗

PubMed1994

Molecular motors and cell motility in the brain.

The advent of video computer-enhanced microscopy has provided a new vision of cell migrations, growth cones, and fast axonal transport in the nervous system. In images obtained in studies of fast transport in isolated axoplasm from the squid giant axon, a virtual torrent of membrane traffic could be seen moving in both directions. Similarly, examination of growth cones and cell migrations in vitro and in vivo revealed properties of cell motility that were previously unsuspected. Evidence has accumulated that many of these activities are driven by a variety of microtubule and microfilament based motors.

Actins↗

PubMed2002

Bioinspired engineering of exploration systems for NASA and DoD.

A new approach called bioinspired engineering of exploration systems (BEES) and its value for solving pressing NASA and DoD needs are described. Insects (for example honeybees and dragonflies) cope remarkably well with their world, despite possessing a brain containing less than 0.01% as many neurons as the human brain. Although most insects have immobile eyes with fixed focus optics and lack stereo vision, they use a number of ingenious, computationally simple strategies for perceiving their world in three dimensions and navigating successfully within it. We are distilling selected insect-inspired strategies to obtain novel solutions for navigation, hazard avoidance, altitude hold, stable flight, terrain following, and gentle deployment of payload. Such functionality provides potential solutions for future autonomous robotic space and planetary explorers. A BEES approach to developing lightweight low-power autonomous flight systems should be useful for flight control of such biomorphic flyers for both NASA and DoD needs. Recent biological studies of mammalian retinas confirm that representations of multiple features of the visual world are systematically parsed and processed in parallel. Features are mapped to a stack of cellular strata within the retina. Each of these representations can be efficiently modeled in semiconductor cellular nonlinear network (CNN) chips. We describe recent breakthroughs in exploring the feasibility of the unique blending of insect strategies of navigation with mammalian visual search, pattern recognition, and image understanding into hybrid biomorphic flyers for future planetary and terrestrial applications. We describe a few future mission scenarios for Mars exploration, uniquely enabled by these newly developed biomorphic flyers.

Algorithms↗

PubMed1985

Ventriculitis after metrizamide lumbar myelography.

A 62-year-old man underwent lumbar metrizamide myelography complicated initially by a bout of aseptic chemical meningitis. Afterward, he suffered persistent headache, nausea, and blurred vision and, 12 weeks after his myelography, computed tomographic scans showed abnormalities consistent with a chronic ventriculitis. The case is presented; its pathological substrate and clinical implications are discussed.

Cerebral Ventricles↗