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At least 397 records · Page 22Linked to original sources

PubMed2004

More workload on the central executive of working memory, less attention capture by novel visual distractors: evidence from an fMRI study.

The present study examined the interaction of the central executive in working memory with visual attention. Native Chinese participants were given two versions of a number subtraction task, one of low demand and one of high demand, and were asked to ignore a simultaneously presented peripheral distractor. The distractor could be Chinese or Korean characters, familiar or novel to participants, respectively. Compared with the low-demand subtraction task, brain regions commonly associated with central executive functions, including left middle prefrontal cortex, anterior cingulate cortex, and precentral gyrus/sulcus, were significantly activated in the high-demand task. Critically, there was a significant interaction between distractor type and task demand. Novel distractors captured attention and elicited automatic visual analysis, shown by primary visual cortex activation, only when the subtraction task was of low demand but not when it was of high demand. The results provide confirmatory evidence that the extent to which higher level cognitive resources, specifically, the central executive component of working memory, are absorbed by a cognitive task has an impact upon automatic processing that occurs in response to distracting items.

Adult↗

PubMed2003

Methods for analysis and visualization of SNP genotype data for complex diseases.

SNP markers are becoming central for studying genetic determinants of complex diseases. Large SNP data collected in such studies call for the development of specialized analysis tools. We present methods for selecting sets of SNPs that can be associated to sample properties in case/control studies. We also describe how scoring and selection can be statistically tested. This is done at the single locus as well as at the set level.

Bayes Theorem↗

PubMed2000

Detection of female carriers of congenital color-vision deficiencies by visual pigment gene analysis.

PURPOSE: Congenital color-vision deficiencies are frequent among males, 4.7-8.0%, suggesting that female carriers are present at a frequency of 9-15%. The purpose of this study was to determine whether carriers could be detected by analysis of the visual pigment genes. METHODS: DNA from 29 males with congenital color-vision deficiencies, from their mothers, and from 117 randomly-selected females was analyzed. The most upstream genes, the downstream genes, and the most downstream genes in the red/green pigment gene arrays were amplified separately by PCR. Exon 5 of each gene was analyzed by single-strand conformation polymorphisms (SSCP). RESULTS: Analysis of the visual pigment genes suggests that one of the 29 mothers examined is a female protan and two others are carriers of both protan and deutan defects. The remaining 26 mothers were confirmed to be carriers of congenital color-vision deficiencies. Unusual patterns were observed in 15 (13%) of the randomly-selected females; among them, 5 appeared to be protan carriers and at least 4 to be deutan carriers. CONCLUSIONS: Female carriers of congenital color-vision deficiencies can be detected by analysis of the visual pigment genes. Since the proportion of females showing unusual patterns was slightly higher than expected, some must be false-positives and require more detailed examination.

Color Perception↗

PubMed1985

Analysis of visual scanning patterns of pistol shooters.

Visual behaviour of pistol shooters of various levels of experience was studied using a video-oculometric technique to record the direction of gaze. A spatio-temporal analysis of the fixation patterns of subjects (five international pistol shooters and five international pentathletes) found that patterns were related to the level of skill. The pentathletes, whose level was lower, positioned their gaze on the weapon sight and visually followed the movement of the weapon towards the target. The pistol shooters appeared to use negative feedback in bringing up their weapons, so reducing the angle formed by the weapon, target and gaze. They fixed their gaze directly on the target or between the target and the weapon. Observations showed a prolonged time of attack (means = 1.107 s vs 0.558 s; P less than 0.001) and a shorter stabilization time (means = 0.714 s vs 1.216 s; P less than 0.001) for the most expert shooters. The psycho-physiological mechanisms which were the basis of these patterns and the reasons why shooters chose them are discussed.

Humans↗

PubMed2006

Analysis and visualization of cell movement in the developing zebrafish brain.

Detailed reconstruction of the spatiotemporal history of embryonic cells is key to understanding tissue formation processes but is often complicated by the large number of cells involved, particularly so in vertebrates. Through a combination of high-resolution time-lapse lineage tracing and antibody staining, we have analyzed the movement of mesencephalic and metencephalic cell populations in the early zebrafish embryo. To facilitate the analysis of our cell tracking data, we have created TracePilot, a software tool that allows interactive manipulation and visualization of tracking data. We demonstrate its utility by showing novel visualizations of cell movement in the developing zebrafish brain. TracePilot (http://www.mpi-cbg.de/tracepilot) is Java-based, available free of charge, and has a program structure that allows the incorporation of additional analysis tools.

Animals↗

PubMed1979

[Further research on the functional asymmetry between the superior and inferior visual hemifields: analysis of the reaction time to simultaneous stimulation of the two hemi-fields].

It has been previously reported that presentation of square-wave gratings to either side of the horizontal meridian of the visual field gives rise to different Simple Reaction Times (RTs), depending upon the spatial frequency of the stimuli. Specifically, for 1 c/deg stimulus RT is faster in the lower hemefield, whereas the reverse is true for 3 c/deg pattern, RT being faster in the upper visual field. In the reported experiment, RT to simultaneous presentation of either the same (alternatively 1 c/deg or 3 c/deg) or different (i.e. 1 c/deg and 3 c/deg combined) spatial frequencies to both hemifields was analyzed. The data show that whenever the two half components correspond to different RTs, the resulting RT equates that of the faster component. Conversely, when the two components give rise to identical RTs, the resulting RT does not differ from the value obtained with each half stimulus. Implications of this result for the functional organization of the visual system are discussed.

Adult↗

PubMed1995

[Visual function analysis of diabetic retinopathy using a contrast sensitivity analyser and usefulness of nicardipine hydrochloride].

Contrast sensitivity was measured in patients with mild diabetic retinopathy using a contrast sensitivity analyser on a personal computer to evaluate visual function. The effect of nicardipine hydrochloride for visual function in mild diabetic retinopathy was also evaluated. Suppression of contrast sensitivity in a comprehensive band of spatial frequency was seen in the patients with normal visual acuity. Apparent improvement of contrast sensitivity was seen in the patients after 3 months of nicardipine hydrochloride treatment. It became clear that even if patients with mild diabetic retinopathy have normal visual acuity, measurement of contrast sensitivity is very important to evaluate the visual function. We also found that nicardipine hydrochloride is effective in treating the impairment of visual function in patients with mild diabetic retinopathy.

Adult↗

PubMed2006

Spatiotemporal tuning of rapid interactions between visual-motion analysis and reaching movement.

In addition to the goal-directed preplanned control, which strongly governs reaching movements, another type of control mechanism is suggested by recent findings that arm movements are rapidly entrained by surrounding visual motion. It remains, however, controversial whether this rapid manual response is generated in a goal-oriented manner similarly to preplanned control or is reflexively and directly induced by visual motion. To investigate the sensorimotor process underlying rapid manual responses induced by large-field visual motion, we examined the effects of contrast and spatiotemporal frequency of the visual-motion stimulus. The manual response amplitude increased steeply with image contrast up to 10% and leveled off thereafter. Regardless of the spatial frequency, the response amplitude increased almost proportionally to the logarithm of stimulus speed until the temporal frequency reached 15-20 Hz and then fell off. The maximum response was obtained at the lowest spatial frequency we examined (0.05 cycles/degrees). These stimulus specificities are surprisingly similar to those of the reflexive ocular-following response induced by visual motion, although there is no direct motor entrainment from the ocular to manual responses. In addition, the spatiotemporal tuning is clearly different from that of perceptual effects caused by visual motion. These comparisons suggest that the rapid manual response is generated by a reflexive sensorimotor mechanism. This mechanism shares a distinctive visual-motion processing stage with the reflexive control for other motor systems yet is distinct from visual-motion perception.

Adult↗

PubMed1991

Graphical analysis and visualization of three-dimensional properties of molecules and solids.

A simple approach is presented for visualizing three-dimensional properties of molecular and crystalline systems by using PC-based molecular drawing software. This allows a scientist with lower-cost PC-graphics capability to carry out analysis of data, such as wave functions and electron density, which would otherwise require a dedicated graphics workstation and expensive specialized software. In this approach, a data set [x,y,z,f1(x,y,z)] is transformed to a new set of data [x,y,z] for values of f1 meeting specified requirements. The function f1, which varies throughout a chemical system is difficult to visualize. However, a more manageable data set is obtained if the set of Cartesian coordinates corresponding to locations in the system where f1 has a specified value are used. This set of points can then be visualized and plotted with standard graphics software or PC-based molecular modeling programs. In addition, the use of PC-based molecular graphics permits one to superimpose the data describing molecular properties on drawings of the molecular geometry. The entire object can then be rotated to facilitate a clear analysis of the property of the molecule.

Chemical Phenomena↗

PubMed1991

Patterns in visual interpretation of coronary arteriograms as detected by quantitative coronary arteriography.

In part 1 of a three-part study, 14 novice readers and 6 experienced cardiologists interpreted phantom images of known stenosis severity. No difference between the interpretations of experienced and novice readers was detectable. Visual estimates of "moderately" severe stenosis were 30% higher than actual percent diameter stenosis. In part 2 of the study, visual interpretation of percent diameter stenosis from 212 stenoses on 241 arteriograms was compared with quantitative coronary arteriographic assessment. The visual analysis overestimated disease severity in arteries with greater than or equal to 50% diameter stenosis (except for right coronary lesions) and underestimated severity in all arteries with less than 50% diameter stenosis. Of the 241 arteriograms, 40 had quantitative and visual analysis of all three coronary arteries for assessment of significant disease. In only 62% of the cases did visual and quantitative methods agree on the presence of severe disease; visual estimates diagnosed significantly (p less than 0.05) more three-vessel disease. In part 3 of the study, comparison of percent diameter stenosis by visual estimate with quantitative coronary arteriographic assessment before and after balloon angioplasty of 38 stenoses showed that visual interpretation significantly (p less than 0.001) overestimated initial lesion severity and underestimated stenosis severity after angioplasty.

Angiography↗

PubMed1988

Parameters of exponentially damped sinusoids in noise and their application to the analysis of visual evoked potentials.

The backward prediction and singular value (SV) truncation methods for estimating multiple exponentially damped real sinusoids in noise have been studied. The basic theory and algorithm are outlined, and the effect on the error of computational parameters, such as the sampling window, the sampling rate, the order of the prediction-error filter (PEF) and the truncated point of SV, were studied using simulated data. If the computational parameters are carefully chosen, the estimate of frequency and damping factor of a damped sinusoid is quite accurate (within a certain range of signal to noise (S/N) ratio). We use this method to estimate the parameters of visual evoked potentials (VEP) and then reconstructed them from estimated parameters according to the resonant model. The error between original VEP and the reconstructed waveform is within 5%. This method can be used in the analysis and recognition of various systems.

Algorithms↗

PubMed2006

Arnold-Chiari-II malformation and cognitive functioning in spina bifida.

Spina bifida is a multifaceted neurological condition with complex neuropsychological sequelae. The cognitive outcome in spina bifida has frequently been attributed to the severity of the hydrocephalus. However, because of complex neuropathology, the influence of hydrocephalus alone does not sufficiently explain the deficits in the cognitive profile in spina bifida. To date, little is known of the role of Arnold-Chiari-II malformation (ACM) in the cognitive profile of these patients. Aim of the current study is to delineate the specific contribution of the ACM in spina bifida by comparing children with ACM and those without ACM. 46 children between 6 and 15 years of age underwent a neuropsychological assessment covering intelligence and a wide range of cognitive functions, such as visuo-motor processing, attention, memory, word fluency and speed of information processing. Comparisons were made between patients with ACM (ACM+) and those without ACM (ACM-); all children with ACM+ also had hydrocephalus. Confounding effects of global cognitive impairment were excluded, such that groups were matched on verbal IQ. Because of complex neuropathology, which is inherent to spina bifida, the method applied was based on a comparison of cognitive profiles of the study group with profiles of patients with cerebellar damage and hydrocephalus found in the literature. Impaired visual analysis and synthesis, verbal memory, and verbal fluency, even after correction for global cognitive impairment, were observed in children with ACM. The hypothesis that in addition to impairment in visual analysis and synthesis, which are related to both hydrocephalus and ACM, specific deficiencies in verbal memory and fluency may be attributed to ACM is supported.

Adolescent↗

PubMed1995

[Detection of myocardial 123I-BMIPP distribution abnormality in patients with ischemic heart disease based on normal data file in bull's-eye polar map].

Visual interpretation of 123I-BMIPP (BMIPP) myocardial images has difficulties in detecting mild reduction in tracer uptake. We studied the significance of the objective assessment of myocardial BMIPP maldistributions at rest by using a Bull's-eye map and its normal data file for detecting ischemic heart disease. Twenty nine patients, 15 with prior myocardial infarction and 14 with effort angina were studied. The initial 15-min BMIPP image was evaluated by visual analysis and by generating the extent Bull's-eye map which exhibits regions with reduced % uptake under mean-2SD of 10 normal controls. The sensitivity for determining coronary lesions in non-infarcted myocardial regions with the extent map was superior to that with visual analysis (67% vs. 33%). In the regions supplied by the stenotic coronary artery, those which showed visually negative but positive in the map and which showed positive in both had higher incidence of wall motion abnormalities and severe coronary stenosis than those with normal findings in both. These results suggest that the objective assessment based on the normal data file in a Bull's-eye polar map is clinically important for improving the limitation of the visual interpretation in 123I-BMIPP imaging.

Adult↗

PubMed2006

Low sensitivity of three-phase bone scintigraphy for the diagnosis of repetitive strain injury.

CONTEXT AND OBJECTIVE: The diagnosis of repetitive strain injury (RSI) is subjective and solely based on clinical signs and physical examination. The aim of this paper was to assess the usefulness of three-phase bone scintigraphy (TPBS) in diagnosing RSI. DESIGN AND SETTING: Prospective study at the Division of Nuclear Medicine, Department of Radiology, School of Medical Sciences, Universidade Estadual de Campinas (UNICAMP). METHODS: Seventy-three patients (mean age 31.2 years; 47 males) with clinical suspicion of RSI in the upper limbs were studied. A total of 127 joints with suspicion of RSI were studied. The shoulders, elbows and wrists were analyzed semi-quantitatively, using the shafts of the humeri and ulnae as references. The results were compared with a control group of 40 normal individuals. The patients signs and symptoms were used as the "gold standard" for calculating the probabilities. RESULTS: From visual analysis, abnormalities were observed in the flow phase for four joints, in the blood pool phase for 11 joints and in the delayed images for 26 joints. Visual analysis of the joints of the control group did not show any abnormalities. Semi-quantitative analysis showed that most of the patients joint ratios were normal. The exceptions were the wrists of patients with left-sided RSI (p = 0.0216). However, the sensitivity (9%) and accuracy (41%) were very low. CONCLUSION: TPBS with semi-quantitative analysis has very low sensitivity and accuracy in the detection of RSI abnormalities in the upper limbs.

Adult↗

PubMed1997

[Correlation analysis between visual acuity and sitting postural parameters of young students].

The relationship between failing eyesight and the sitting posture of young students while studying was studied quantitatively. Among the 19 students who participated in this study, 9 were classified as emmetropic and 10 were myopic. The mean age was 13.2 +/- 2.2 (mean +/- standard deviation) years. Viewing distance, neck angle, viewing angle, vertical gaze direction, and ocular surface area while studying were measured from the lateral and frontal view images of video recordings of the posture. Viewing distance, accommodative power, neck angle, viewing angle, near point, and log transformed visual acuity showed significant differences between these two groups (p < 0.001). Viewing distance of myopes (15.0 +/- 1.9 cm) (mean +/- standard desviation) is shorter than that of emmetropes (30.2 +/- 4.1 cm). Accommodative power of myopes was lower than that of emmetropes. Correlation analysis revealed that the viewing distance of students significantly correlates to neck angle, viewing angle, accommodative power, near point, and visual acuity (p < 0.01). It can be surmised that the failing eyesight of young students results from postural problems such as shortness of viewing distance and increased neck flexion.

Accommodation, Ocular↗

PubMed1977

Multivariate analysis of visual evoked response.

The visual potentials evoked by flash are analyzed in healthy subjects in cases of retinal detachment, of optic nerve lesions, and of amblyopia by means of different statistical methods: 1. Analysis of the various features of the response, evaluated separately 2. Analysis of the interdependence between the measures of the various features The first method supplies information on the differences in 'size' of the curves in the various samples, the second method reveals differences of 'shape'. The second method has proved to be able to distinguish both normal conditions from pathologic impairment of optic structures and the different sites of the lesions.

Adolescent↗

PubMed1983

Natural history of platelet deposition on Dacron aortic bifurcation grafts in the first year after implantation.

This study defined the dynamics of platelet deposition on Dacron arterial grafts up to 1 year after implantation in human subjects. Indium-111 platelet imaging was performed on 8 men 1 to 2 weeks after graft implantation and on 5 of these patients at a mean of 31 weeks (range 28 to 34) and again at 55 weeks (range 50 to 62). Serial imaging was performed at 24 to 96 hours after platelet labeling and injection in each study. Quantitative analysis was performed using a graft/blood ratio that compared background-corrected indium-111 platelet activity in the graft region to whole-blood indium-111 platelet activity. Additionally, blinded qualitative visual analysis of the images compared graft activity with the activity in adjacent native arteries. The mean of all graft/blood ratios (24, 48, 72, and 96 hours) progressively decreased from 4.4 +/- 2.1 (+/- 1 standard deviation) at 1 to 2 weeks to 3.0 +/- 1.8 at 31 weeks (p = 0.002). There was no further decrease at 55 weeks (2.8 +/- 2.0). For comparison, 12 normal subjects without grafts had a mean ratio of 1.8 +/- 0.7. Visual analysis detected platelet deposition in 7 of 8 grafts at 1 to 2 weeks, 4 of 5 at 31 weeks, and 4 of 5 at 55 weeks. Deposition decreased qualitatively in 2 of 5 patients at late study. It is concluded that there is consistent, early platelet deposition on Dacron grafts in man. Although deposition decreases over 31 weeks, it remains readily detectable in most patients at 1 year. These findings suggest absent or incomplete endothelialization of the graft flow surface in humans in the first year after implantation.

Aged↗

PubMed2004

Visualization-based analysis for a mixed-inhibition binary PBPK model: determination of inhibition mechanism.

A physiologically based pharmacokinetic (PBPK) model incorporating mixed enzyme inhibition was used to determine the mechanism of metabolic interactions occurring during simultaneous exposures to the organic solvents chloroform and trichloroethylene (TCE). Visualization-based sensitivity and identifiability analyses of the model were performed to determine the conditions under which four inhibitory parameters describing inhibitor binding could be estimated. The sensitivity methods were used to reduce the 4-parameter estimation problem into two distinct 2-parameter problems. The inhibitory parameters were then estimated from multiple closed-chamber gas-uptake experiments using graphical methods. The estimated values of the four inhibitory parameters predicted that chloroform and TCE interact in a competitive manner. Based on the model analysis, we present recommendations for the design of experiments for determination of inhibition mechanism in binary chemical mixtures. We assert that a thorough analysis of the parameter-dependent sensitivity and identifiability characteristics can be used to plan efficient experimental protocols for the quantitative analysis of inhalation pharmacokinetics.

Animals↗