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At least 739 records · Page 41Linked to original sources

PubMed1999

Visual discrimination after anterior temporal lobectomy in humans.

OBJECTIVE: To determine whether right anterior temporal lobectomy (RTL) results in perceptual deficits, and whether the perception of particular stimulus features (i.e., shape, motion, color) is affected differentially. BACKGROUND: RTL results in abnormal visual discrimination, recognition, and recall of pictorial material that cannot be easily specified verbally, such as designs and faces. It is unclear whether stimuli must be conceptually meaningful to elicit perceptual deficits. METHODS: Tests were constructed to assess a wide spectrum of basic visual discrimination abilities with simple, meaningless stimuli. The performance of nine patients who underwent left temporal lobectomy (LTL) and nine patients who underwent RTL were compared with that of normal control individuals. The mean excision size along lateral cortex was 3.7 cm for the LTL group and 5.6 cm for the RTL group; mean mesial excision size was 5.2 cm for LTL and 4.6 cm for RTL. RESULTS: Basic visual discrimination capacities were demonstrated to be essentially intact after LTL and RTL, except for a mild loss of blue color discrimination after RTL. CONCLUSIONS: There is little evidence that RTL produces perceptual impairments limited to the domain of pattern perception, or generalizable to nonmeaningful stimuli. The perceptual loss after RTL may be largely restricted to extraction of meaning, and related to the disruption of the circuits that connect the outcome of visual analysis to previously stored semantic information.

Adult↗

PubMed1986

Local and global visual processing.

The fundamental sinusoidal components of a chequerboard pattern are oriented at 45 degrees to the orientation of the chequerboard edges. Removal of one of the fundamental sinusoids (at +45 degrees) creates a useful pattern for studying the mechanisms of visual analysis. Close up, the pattern appears to be oriented +45 degrees, although there is no global energy at that orientation, implying local analysis. At a distance, the perceived diagonality switches to -45 degrees implying access to global information. Measurements show that contrast thresholds for seeing diagonality at +45 degrees follow closely those for detecting the 5th harmonic component of the pattern, over a wide range of spatial frequencies and luminances. Low pass filtering also causes the pattern to be perceived according to its global energy, provided that the cutoff frequency is set to remove the fifth harmonic. We conclude that, at least for this particular stimulus, the visual system performs a local analysis if the fifth harmonic is visible and a global analysis if not.

Form Perception↗

PubMed1985

Quantitative planar thallium-201 stress scintigraphy: a critical evaluation of the method.

The results of quantitative analysis of planar thallium-201 stress scintigraphy are superior to those of visual analysis. The increased sensitivity for detection of coronary artery disease is associated with maintenance of specificity. Consequently, we believe that quantitative analysis is the state-of-the-art for planar 201Tl stress scintigraphy. We emphasize that for reliable and reproducible results, rigorous quality control and strict adherence to a standardized imaging protocol are necessary. An important feature is clarity of display of computer data. In our experience, the most important feature for making quantitative analysis reliable and accessible for a broader user market is simultaneous display of the lower limits of normal with processed patient data. This provides a simple visual impression of the degree and extent of abnormal 201Tl distribution and kinetics relative to the lower limit of normal.

Coronary Disease↗

PubMed2000

Angiogenesis monitored by perfusion with a space-filling microbead suspension.

Numerous laboratories are focusing efforts on delivering gene products to induce or prevent the development of new blood vessels in adults, with the hope of rescuing ischemic tissues, circumventing cardiac bypass surgery, or inhibiting tumor growth. Current approaches to the assessment of vascular continuity involve the introduction of either dyes or fluorescent microspheres to track blood flow. However, dyes and dextrans are subject to leakage when vessels are hyperpermeable, a situation that may occur in studies of tumor vasculature and during efforts to stimulate therapeutic angiogenesis. Furthermore, the microspheres that are used for flow studies do not allow a comprehensive visual analysis of vascular continuity. Here we report a method for the visual assessment of microvascular continuity in mouse muscle under circumstances in which vessels are leaky. The approach involves perfusion of the vasculature with fluorescent beads that are much smaller than those used for flow studies. The suspension behaves like a fluid and completely fills the vessels, yet the beads do not leak from VEGF-permeablized capillaries and remain localized in histological sections. Use of beads with the proper fluorescence emission wavelengths allows immunofluorescent colocalization with vessel-specific markers. We compare this improved method with other methods for tracking vascular continuity involving dextrans and larger beads. This approach should aid in the dynamic study of tumor angiogenesis and the evaluation of efforts to deliver angiogenic factors.

Animals↗

PubMedDate not supplied

Combination of multiple pencil-beam imaging to computed storage phosphor radiography: a new method.

Computed radiography (CR) with storage phosphors offers a wide dynamic range and improved sensitivity compared to film-screen technology. CR was combined in this study with a prototype multiple pencil-beam (MPB) imaging device which has been shown to be very effective in scatter reduction. The combination was analyzed and compared to the standard technique of grid screening in two ways: a free-response ROC (FROC) analysis was first performed followed by a blinded test arrangement for visual analysis of image quality in a series of computed radiography of the lumbar spine by both the MPB and grid modalities. The results of the FROC study showed a statistically significant (P less than or equal to 0.01) improvement in signal detection. The MPB-CR images of the lumbar spine had more contrast but also a slightly mottled or grainy appearance. Image quality was found good but contrast processing was criticized because it seemed to result in a too steep display of contrast in MPB imaging. This should be avoidable by changing the image processing parameters.

Adult↗

PubMed2001

Magnetization transfer measurements of the hippocampus in the early diagnosis of Alzheimer's disease.

We measured magnetization transfer ratios (MTRs) of the hippocampus in 38 patients with Alzheimer's disease (AD), including very mild (Clinical Dementia Rating [CDR] 0.5, n=12), mild (CDR 1, n=14), and moderate stages (CDR 2, n=12), and in 21 healthy elderly control subjects. Medial temporal lobe atrophy was graded subjectively on a five-point scale by two observers blinded to clinical data. Compared with the controls, each of the AD groups, including the very mild group, had significant atrophy of the medial temporal lobe and a decrease in MTRs of the hippocampus. Logistic regression analysis revealed that the overall discrimination rate with MTR measurement and visual analysis of the atrophy was 85% and 73% between the control group and the CDR 0.5 group, 89% and 80% between the control group and the CDR 1 group, and 100% and 91% between the control group and the CDR 2 group, respectively. MTR measurements may provide additional information in detecting structural damage of the hippocampus of AD and be helpful in providing improved diagnosis and early detection of AD.

Aged↗

PubMed1996

Fourier phase mapping of the human heart. The use of spatial modulation of magnetization cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Fourier phase mapping of cine cardiac magnetic resonance (MR) imaging offers noninvasive analysis of temporal cardiac activation patterns. The aim of our investigation was to extend this analysis to intramyocardial dynamics. METHODS: A fast-imaging with steady-state precision (FISP) two-dimensional gradient echo spatial modulation of magnetization (SPAMM) sequence and a segmented two-dimensional FISP-SPAMM sequence were applied to acquire cine MR images of the complete cardiac cycle on a 1.5-tesla imager. Signal intensity data were submitted to pixel-wise Fourier phase analysis. Color-encoded amplitude and phase maps were displayed for visual analysis. RESULTS: Using the unsegmented SPAMM two-dimensional FISP sequence, a more consistent tag-to-myocardium contrast and a higher number of cardiac phases was achieved than by using the segmented version of this sequence. The typical tag displacement reflected complex intramyocardial dynamics, including rotation. Phase mapping displayed a pattern of contraction consistent with electrophysiologic concepts of cardiac activation. In contrast, the segmented sequence did not reflect any differences in the onset of cardiac contraction, although tag displacement was apparent with this sequence as well. CONCLUSIONS. Fourier phase mapping of cardiac MR imaging tagging studies allows for noninvasive analysis of intramyocardial activation patterns. A temporal resolution of 50 mseconds per image at a heart rate of 75 beats per minute allows for an assessment of spatial differences in the onset of myocardial activation.

Adult↗

PubMed1995

Quantitative DNA analysis: a comparison of conventional DNA ploidy analysis and teleploidy.

JPEG compression can be used on images for DNA ploidy analysis if careful consideration is given to the level of compression used for file storage. The amount of JPEG compression possible may vary depending on the type of tissue analyzed, however, a compromise may be reached for all types of tissue. JPEG compression should not go over a level of 70 for DNA analysis as this would result in possibly erroneous IOD calculation and erroneous DNA ploidy analysis. Also, the resulting file quality is so poor that even visual analysis is not possible. With careful training of personnel in cell selection, remote DNA ploidy analysis would be an effective tool for standardization and quality control in the pathology laboratory. By using remote DNA ploidy analysis, it is possible for hospitals to consolidate their workload, and make DNA ploidy analysis by image cytometry a cost effective test in the laboratory. Proficiency testing would also become possible as all laboratories performing DNA ploidy analysis would receive the same fields of view for testing. DNA ploidy analysis by image cytometry using stored images could be a versatile tool for the telepathology community.

Animals↗

PubMed2003

Electrophoretic signal comparison applied to mRNA differential display analysis.

Gene expression analysis by electrophoretic methods is currently limited by the labor-intensive visual evaluation of the electrophoretic signal profiles. For this purpose, we present a flexible approach to computer-assisted comparison of quantitative electrophoretic patterns between multiple expression signals. Gaussian curves are first fitted to the complex peak mixtures, and the resulting approximate signals are then aligned and compared on a peak-by-peak basis with respect to specific patterns defined by the investigator. The rationale of the method is to produce a compressed list of exceptional expression patterns quantified by a set of associated numeric features. A score value is attached to each pattern in such a way that large values identify the most potential findings to be focused on in visual analysis instead of the vast amount of original electrophoretic results. The validity of the method is demonstrated by analyzing a large set of electrophoretic data from mRNA differential display experiments monitoring changes in gene expression patterns in human colonic carcinoma. The automated identification of variously defined gene expression patterns agrees well with the visual evaluation of the same electropherograms. The general comparison approach may also be found useful with other gene expression profiling instruments.

Adenocarcinoma↗

PubMed1998

Subclinical rhythmic electrographic discharges of adults (SREDA) revisited: a study using digital EEG analysis.

Previous descriptions of the subclinical rhythmic electrographic discharges of adults (SREDA) have been based entirely on visual analysis of analog electroencephalographic (EEG) recordings. The introduction of digital electroencephalograms (EEGs) and advances in digital signal processing provide an opportunity to restudy in more depth the nature of SREDA. We identified nine patients who had SREDA diagnosed on a routine EEG recording since the introduction of digital EEG to our laboratory in August 1995. Following careful rereview using standard montages, six of these patients were determined to fulfill the traditional requirements for the diagnosis of SREDA, whereas three were believed to have other benign discharges. Review with Laplacian montages demonstrated that the site of the SREDA activity was maximal in the parietal region or parietocentrotemporal regions, whereas it was maximal in the temporal or frontotemporal regions in the non-SREDA discharges. Frequency analysis, using both the conventional fast Fourier transform (FFT) and time-frequency mapping with the Wigner FFT variant, demonstrated that the SREDA consisted of a complex mixture of multiple rapidly shifting frequencies which showed little spatial and temporal correlation. In contrast, the non-SREDA all consisted of a single dominant well-organized rhythmic frequency spectrum that remained stable throughout space and time.

Adult↗

PubMed2026

Bioinformatics Analysis and Experimental Validation of Key Genes Associated With Hypoxia and Ischemia in Myocardial Infarction.

BACKGROUND: This study aimed to screen and identify core hypoxia-ischemia-related genes associated with myocardial infarction (MI). METHOD: Two transcriptomic datasets, GSE97320 and GSE48060, were retrieved from the Gene Expression Omnibus (GEO) database. After data integration and batch effect elimination, differential expression analysis was performed to screen differentially expressed genes (DEGs), and the corresponding visualization analysis was conducted. Hypoxia-ischemia-related genes were acquired from the GeneCards database; hypoxia-ischemia related genes (HIRGs) were subsequently identified by intersecting the retrieved genes with screened DEGs. Gene Ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were implemented to explore the biological functions and underlying signaling pathways of HIRGs. A combination of protein-protein interaction (PPI) network analysis and random forest (RF) algorithm was applied to screen hub genes from HIRGs. The external GEO dataset GSE66360 was utilized to validate the expression patterns of candidate hub genes. Furthermore, an acute myocardial infarction (AMI) mouse model was established, and quantitative real-time polymerase chain reaction (qPCR) was performed to detect the mRNA expression levels of hub genes in myocardial tissues for in vivo validation. RESULTS: A total of 633 DEGs and 308 hypoxia-ischemia-related genes were screened in the present study, among which 21 overlapping HIRGs were obtained. PLAUR and IL1B were finally identified as two hub genes from HIRGs based on PPI network and random forest algorithm. The qPCR results revealed that the expression levels of PLAUR and IL1B were significantly upregulated in the AMI group compared with the sham operation group (p < 0.05). CONCLUSION: The present findings demonstrated that PLAUR and IL1B serve as pivotal genes involved in the pathological hypoxia-ischemia process of AMI. These two genes may act as novel biomarkers and promising therapeutic targets for the recognition and clinical intervention of hypoxia-ischemia injury following AMI.

Myocardial Infarction↗

PubMed1978

Computer-assisted interpretation of clinical EEGs.

A multivariate pattern recognition technique has been developed, to distinguish the EEGs of patients with cerebral pathology from those of normal controls and to localize any abnormalities detected. Two methods of feature extraction have been used, power spectral density and slope descriptor analysis, together with various types of feature compression. These techniques have been evaluated on EEGs from 63 patients with proven pathology. Spectral analysis proved more reliable than slope descriptor analysis and predicted the site of cerebral pathology more accurately than did visual assessment of the EEGs. This apparent improvement over the diagnostic reliability of visual analysis in considered to justify further development and evaluation of this technique.

Adult↗

PubMed1999

Clinical neurophysiology in childhood headache.

Electrophysiological studies in childhood headache are of interest because of the need to make a clinical diagnosis and also because of the efficacy of physiopathological studies in juvenile age attributable to the recent outcome of the illness, with less clinical modification by environmental factors or drug use. Electrophysiological studies in childhood headache are concerned with migraine and electroencephalographic (EEG) evaluations; evoked potentials, event-related potentials and, less often, electromyographic studies are also reported. Visual analysis of EEG suggests an association between migraine and epilepsy; quantitative EEG, visual and event-related evoked potentials show fluctuating abnormalities, depending on the occurrence of the migraine attacks and permanent anomalous patterns related to the basic mechanisms underlying the disease. Blink reflex studies might suggest a primary dysfunction of the nociceptive control central system in children affected by tension-type headache and migraine. The use of neurophysiological procedures in juvenile migraine is considered limited in clinical practice and of particular interest in neurophysiological studies of headache.

Child↗

PubMed2002

Comparison of statistical parametric mapping and SPECT difference imaging in patients with temporal lobe epilepsy.

PURPOSE: Statistical parametric mapping (SPM) is an image-analysis tool that assesses the statistical significance of cerebral blood flow (CBF) changes on a voxel-by-voxel basis, thereby removing the subjectivity inherent in conventional region-of-interest (ROI) analysis. Our platform of single-photon emission computed tomography (SPECT) ictal-interictal difference imaging in clinical epilepsy has been validated for localizing seizure onset. We extend the tools of SPM by further applying statistical measures for the significance of perfusion changes in individual patients to localize epileptogenic foci in patients with defined temporal lobe epilepsy by using paired scans in this preliminary study. METHODS: Twelve patients with pairs of periictal and interictal SPECT scans were analyzed in this comparison study between SPECT difference imaging and SPM difference analysis by using a reference database of paired normal healthy images. These 12 patients possessed seizure foci localized to the mesial temporal lobe as confirmed by surgical outcome and by hippocampal sclerosis on pathology. SPM was used to identify clusters of increased or decreased CBF in each patient in contrast to our control group. RESULTS: The regions having the most significant increased or decreased CBF by SPM analysis were in agreement with regions identified by conventional difference imaging and visual analysis by viewers blinded to the results of the SPM analysis. Differentiated further by time of radiopharmaceutical injection, six of seven patients injected within 100 s of seizure onset displayed hyperperfusion changes localized to the corresponding epileptogenic temporal lobe by both techniques. Among patients receiving injections after 100 s, both techniques showed primarily regions of hypoperfusion, which again were similar between these two methods. CONCLUSIONS: The results provide strong evidence supporting SPM difference analysis in assessing regions of significant CBF change from baseline in concordance with our current clinically used technique of SPECT ictal--interictal difference imaging in epilepsy patients. Difference analysis using SPM could serve as a useful diagnostic tool in the evaluation of seizure focus in temporal lobe epilepsy.

Adolescent↗

PubMed2003

Neither here nor there: localizing conflicting visual attributes.

Natural visual scenes are a rich source of information. Objects often carry luminance, colour, motion, depth and textural cues, each of which can serve to aid detection and localization of the object within a scene. Contemporary neuroscience presumes a modular approach to visual analysis in which each of these attributes are processed within ostensibly independent visual streams and are transmitted to geographically distinct and functionally dedicated centres in visual cortex (van Essen & Maunsell, 1983; Zihl, von Cramon & Mai, 1983; Maunsell & Newsome, 1987; Tootell, Hadjikhani, Mendola, Marrett & Dale, 1998). In the present study we ask how the visual system localizes objects within this framework. Specifically, we investigate how the visual system assigns a unitary location to objects defined by multiple stimulus attributes, where such attributes provide conflicting positional cues. The results show that conflicting sources of visual information can be effortlessly combined to form a global estimate of spatial position, yet, this conflation of visual attributes is achieved at a cost to localization accuracy. Furthermore, our results suggest that the visual system assigns more perceptual weight (Landy, 1993; Landy & Kojima, 2001) to visual attributes which are reliably related to object contours.

Attention↗

PubMed1992

[Fourier analysis of pattern visual evoked potentials and changes of the harmonic component in longstanding optic neuritis].

To determine the clinical usefulness of Fast Fourier Transform (FFT) for the detection of abnormal pattern visual evoked potentials (P-VEPs), the P-VEPs were recorded using a checkerboard pattern (check size: 14.4') which was reversed ranging from 4 to 16 per second. Fourteen eyes of 7 patients with longstanding optic neuritis and 15 eyes of age-matched normal controls were examined. Means and the standard deviation of the square root of the FFT power as a function of spectral frequency (1.953 x fHz, f = 1-17) were calculated and statistically significant levels between the two groups were studied for each reversal rate. When the reversal rate was more than 8/sec, The 1st or 2nd harmonic components decreased significantly in optic neuritis and the significant levels (p) of the 1st harmonic component were lower than that (p) of 2nd or 3rd harmonic component. When the reversal rate was 6/sec, the 1st and 2nd harmonic components decreased significantly and 1st harmonic component had the same level of significance as the 2nd harmonic component. When the reversal rate was 4/sec, the 2nd, 3rd, 5th and 6th harmonic components decreased significantly but 1st harmonic component did not. The level of significance of the 3rd harmonic component was the lowest followed by that of 2nd harmonic component.(ABSTRACT TRUNCATED AT 250 WORDS)

Evoked Potentials, Visual↗

PubMed1993

Diagnosis and management of reading dysfunction for the primary care optometrist.

A model for the identification/diagnosis and management of reading dysfunction for the primary care optometrist is presented. The model is based upon clinical experiences in both private and academic practice and an extensive review of the literature. The model, illustrated in a series of flow charts and a table, incorporates the major perceptual dysfunctions typically encountered by patients who present with reading problems. The first part of the model, labeled fundamental, demonstrates the minimum diagnostic and management techniques for those children who appear to have reading dysfunction. The second part of the model, labeled complex, provides a more extensive diagnostic and management approach. The validity of the approach is further illustrated in a series of 13 arbitrarily selected cases of reading dysfunction which are statistically analyzed. Robust correlations are found among different tests of visual-motor skills (Bender, Test of Visual Analysis Skills), a test of short-term memory (Getman-Henderson-Marcus Test of Visual Recall), and reading decoding. Modest correlation is also found between a test of auditory perception, The Test of Auditory Analysis Skills (TAAS) and reading decoding. Direct testing for dyslexia using the Dyslexia Determination Test illustrates that not all those with reading dysfunction are dyslexic.

Adolescent↗

PubMedDate not supplied

A visual basic spreadsheet macro for recession curve analysis.

A Visual Basic program for an Excel spreadsheet was written to construct a master recession curve (MRC), using the adapted matching strip method, for recession analysis of ground water level time series. The program uses five different linear/nonlinear regression models to adjust individual recession segments to their proper positions in the MRC. The program can also be used to analyze the recession segments of other time series, such as daily stream discharge or stage. Some examples of field data from Croatia are used to illustrate the usefulness of its application.

Algorithms↗