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At least 1,009 records · Page 56Linked to original sources

PubMed1997

The perception of biological motion across apertures.

To understand the visual analysis of biological motion, subjects viewed dynamic, stick figure renditions of a walker, car, or scissors through apertures. As a result of the aperture problem, the motion of each visible edge was ambiguous. Subjects readily identified the human figure but were unable to identify the car or scissors through invisible apertures. Recognition was orientation specific and robust across a range of stimulus durations, and it benefited from limb orientation cues. The results support the theory that the visual system performs spatially global analyses to interpret biological logical motion displays.

Adult↗

PubMed2004

[Analysis of intraspecific divergence of hexaploid wheat Triticum spelta L. by chromosome C-banding].

Intraspecific divergence of hexaploid wheat Triticum spelta was studied by chromosome C-banding in 41 accessions of different geographic origins. The spelt accessions did not differ in karyotype structure or heterochromatin distribution from common wheat, but showed greater intraspecific polymorphism for chromosome rearrangements (translocations, inversions) and banding patterns. On evidence of C-banding patterns, spelt was assumed to occupy an intermediate position between tetraploid and hexaploid wheat species. Accessions of the Asian spelt subspecies had more diverse banding patterns than European accessions. A relatively high frequency of chromosome rearrangements was observed in Iranian accessions. Visual analysis revealed high uniformity of chromosome banding patterns in T. spelta populations of Afghanistan, Spain, and Germany (Bavarian group), suggesting a significant role of the founder effect in their evolution.

Afghanistan↗

PubMed1996

Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 1. Effect of tablet geometry in buffered medium.

The dissolution rate of a solid drug from the gastrointestinal (GI) tract is affected by the properties and flow dynamics of the liquid medium surrounding the tablet, as well as by the chemical nature of the drug. In this study, naproxen was used as a poorly soluble model drug. The dissolution medium was buffered with acetate, citrate, or phosphate buffer of varied concentrations and pH. GI flow conditions around a stationary tablet were simulated in a laminar flow device by anchoring the tablet on the floor of its channel having a rectangular cross section. Fresh, buffered solution was passed across the tablet and the effluent was collected for analysis and calculation of the dissolution rate. The dissolution rate was found to vary nonlinearly with the exposed tablet height, reaching a maximum at a tablet height approximately half the channel height. This maximum rate was attributed to an optimal combination of (1) eddy mixing and local turbulence generated by the flow impingement on the bluff object (tablet) and (2) the exposed tablet surface area available for dissolution. This effect was further confirmed by using dye-enhanced visual analysis of flow patterns at varied flow rates and exposed tablet heights. Elevation of the tablet to approximately the channel half-height significantly magnified the dissolution rate increase observed on exposure to buffered medium. Thus, tablet height and exposed surface area are major factors in determining dissolution rate, especially in conditions where the dissolving species reacts with the solvent. These results suggest that standard in vitro dissolution rate methods do not qualitatively indicate incremental changes in rate with altered tablet geometry or dissolution medium.

Digestive System↗

PubMed1993

Influence of platelet size before coronary angioplasty on subsequent restenosis.

Platelet size has been shown to reflect platelet activity. We prospectively measured the mean platelet volume (MPV) in 47 patients undergoing single vessel angioplasty for symptomatic angina. The patients underwent repeat angiography 4-8 months later irrespective of symptomatic status. Restenosis was assessed quantitatively by hand held calliper measurements of the lesion and qualitatively by a return of angina, ST segment changes on an exercise test and visual analysis of the lesion severity by two experienced angiographers. Twenty-four patients developed recurrent angina during the follow-up period, the MPV in the group with chest pain was 8.54 +/- 0.60 fl compared to 8.1 +/- 0.69 fl in the asymptomatic group (P = 0.04). Twenty two patients had significant ST segment changes at exercise. In this group the MPV was 8.6 +/- 0.56 fl compared to 8.0 +/- 0.70 fl for the group with a negative test (P = 0.002). Similarly visually assessed angiographic stenosis showed a significant increase in the restenotic group (8.6 +/- 0.56 vs. 8.0 +/- 0.61 fl, P = 0.001). The relative odds for developing clinically defined restenosis were 10.2 times greater if the pre-procedural MPV lay in the upper compared to the lowest quartile. There was a positive correlation between MPV and change in minimal luminal diameter between post angioplasty and follow-up angiography, assessed quantitatively, r = +0.56, P = 0.016. There was no association between clinical or angiographic definitions of restenosis and haemoglobin, red cell count, mean corpuscular volume, white cell count or platelet count. Platelet size may influence the development of restenosis after successful coronary angioplasty.

Angioplasty, Balloon, Coronary↗

PubMed2000

Perceptual learning of the detection of features in X-ray images: a functional role for improvements in adults' visual sensitivity?

Recent perceptual learning research has found long-term increases in the sensitivity of adults' perceptual systems. The authors examined whether such changes could partly explain improvement on tasks such as perception of medical X-ray images. Experiment 1 found experts' sensitivity to low-contrast dots in X-rays was better than novices'. Experiment 2 found a direction of luminance contrast-specific improvement in novices' detection of low-contrast dots in X-rays as a result of practice. Experiment 3 found a partly specific improvement in novices' detection of low-contrast features in real medical X-rays as a result of practice. Results suggest that experience enhances sensitivity to the critical dimensions of visual analysis for detecting abnormalities in X-ray images. Importantly, they demonstrate a real-world adaptive functional role for the long-term flexibility of sensory systems in adulthood.

Adult↗

PubMedDate not supplied

Are the preferred directions of neurons in cat extrastriate cortex related to optic flow?

It has been proposed that one area of extrastriate cortex in the cat, the lateral suprasylvian area (LS), plays an important role in visual analysis during locomotion (Rauschecker et al., 1987). Cells in LS reportedly tend to prefer directions along a trajectory originating at the center of gaze, and passing outward through the receptive-field center. Such directions coincide with the directions of image motion in an optic flow field, the pattern seen by locomoting observers when they fixate the point towards which they are heading (Gibson, 1950). We re-examined this issue for cells in LS with receptive fields in the lower visual field. Cells recorded posterior to Horsley-Clarke A2 showed a clear correlation between preferred direction and receptive-field location, but not that predicted: preferred directions were generally orthogonal to "optic flow" directions. Since these cells were all located posterior to those in studies showing a bias for "optic flow" directions, we hypothesized that there are two cell populations within LS, an anterior population that tends to prefer radial-outward directions, and a posterior population that tends to prefer directions orthogonal to radial. Data from earlier mapping experiments (Sherk & Mulligan, 1993) supported this idea.

Animals↗

PubMed2002

Individual variations in the sulcal anatomy of the basal temporal lobe and its relevance for epilepsy surgery: an anatomical study performed using magnetic resonance imaging.

OBJECT: The concept of selective amygdalohippocampectomy is based on pathophysiological insights into the epileptogenicity of the hippocampal region and the definition of the clinical syndrome of mesial temporal lobe epilepsy (TLE). High-resolution magnetic resonance (MR) imaging allows correlation of the site of histologically conspicuous tissue with anatomical structure. The highly variable sulcal pattern of the basal temporal lobe, however, definitely complicates the morphometric analysis of histomorphologically defined subdivisions of the hippocampal region. The goal of this study was to define individual variations in the sulcal anatomy on the basis of preoperative MR images obtained in patients suffering from TLE. METHODS: The authors analyzed coronal MR images obtained in 50 patients for the presence of and intrinsic relationships among the rhinal, collateral, and occipitotemporal sulci. The surface relief of consecutive sections of 100 temporal lobes was graphically outlined and the resulting maps were used for visual analysis. The sulci were characterized by measurement of their depth, distance to the temporal horn, and laterality. The anatomical measurements and frequencies of sulcal patterns were assessed for statistical correlation with patients' histories and the lateralization of the seizure focus. CONCLUSIONS: Statistical assessment shows that patient sex is a significant factor in sulcal patterns. Anatomical measurements are significantly decreased on the side of the seizure origin, which relates to loss of white matter, a known morphological abnormality associated with TLE. Magnetic resonance imaging allows for accurate preoperative knowledge of individual sulcal patterns and facilitates intraoperative orientation to anatomical landmarks.

Adolescent↗

PubMedDate not supplied

[Post-radiation effect on the interhemispheric asymmetry in EEG and thermography characteristics].

Complex analysis of EEG and thermographic parameters carried out in 10 healthy subjects and 34 patients, Chernobyl clean-up participants revealed a correlation between EEG and brain temperature changes in the baseline state and during mental arithmetic. During cognitive activity the maximal increase in the average EEG coherence and temperature shifts in healthy subjects were observed in the left frontotemporal and right parietotemporal areas. In patients changes in both parameters under study were most pronounced, the interhemispheric relations were impaired. The visual analysis revealed "flat" and "hypersynchronous" EEG types in patients. The dominant pathologic activity in the betal range indicative of mediobasal and oral brainstem lesions was characteristic of the flat EEG. This type of activity was observed in 60% of patients. In these cases, a general decrease in EEG coherence and temperature was most pronounced in the left hemisphere. The hypersynchronou EEG type (40% patients) was characterized by paroxysmal activity in the theta and alpha ranges suggesting diencephalic brain lesions. In these cases, EEG coherence and temperature were more variable; changes in the right hemisphere were significant, be it increase or decrease. Our complex approach to investigation of brain activity in different aspects seems to be promising in estimation of the brain functional state both in healthy persons and patients in remote terms after exposure to radiation. The specific hemispheric temperature changes revealed in Chernobyl patients especially during cognitive activity can be the sequels of postradiation disorders of vascular neuro-circulation. The EEG findings suggest subcortical disorders at different levels (diencephalic or brainstem) and functional failure of the right or left hemispheres in remote terms after exposure to radiation.

Brain↗

PubMed2004

Dynamic digital image analysis: emerging technology for particle characterization.

The feasibility of applying dynamic imaging analysis technology to particle characterization has been evaluated for application in the water sector. A system has been developed which captures in-situ images of suspended particles in a flowing sample stream and analyzes these images in real time to determine particle size and concentration. The technology can measure samples having a wide range of particle sizes (approximately 1.5 to 1,000 microm equivalent circular diameter) and concentrations (<1 to >1 million/ml). The system also provides magnified images of particles for visual analysis of properties such as size, shape and grayscale level. There are no sample preparation requirements and statistically accurate results are produced in less than three minutes per sample. The overall system architecture is described. The major design challenges in developing a practical system include obtaining adequate contrast for the range of particle materials found in typical water samples and achieving this under operating conditions permitting an adequate sample processing rate for real time feedback of results. Performance of the instrument is reported in reference to industry accepted particle standards and applications as an analytical tool for the water industries are considered.

Automation↗

PubMed1989

[Digital storage and semi-automatic analysis of esophageal pressure signals. Evaluation of a commercialized system (PC Polygraft, Synectics)].

The aim of this work was to evaluate a new commercially available pressure recording system (PC Polygraf, Synectics) and to compare this system with a classical method using perfused catheters. The PC Polygraf uses microtransducers and allows direct digitized storage and semi-automatic analysis of data. In the first part of this study, manometric assessment was conducted using only perfused catheters. The transducers were connected to both an analog recorder and to a PC Polygraf. Using the two methods of analysis, contraction amplitudes were strongly correlated (r = 0.99; p less than 0.0001) whereas durations were significantly but loosely correlated (r = 0.51; p less than 0.001). Resting LES pressure was significantly correlated (r = 0.87; p less than 0.05). In the second part of this study, simultaneous recordings of esophageal pressure were conducted in 7 patients, by placing side by side the two tubes (microtransducers and perfused catheters) with the sideholes at the same level. The characteristics of the waves were determined both by visual analysis of analog tracing and by semi-automatic analysis of digitized recording with adequate program. Mean amplitude was lower with the microtransducers than with the perfused catheters (60 vs 68 cm H2O; p less than 0.05), but the duration of waves was not significantly different when using both systems. Values obtained for each of these parameters using both methods were significantly correlated (amplitude: r = 0.74; duration: r = 0.51). The localization and the measure of the basal tone of sphincter were found to be difficult when using microtransducers. These results show that PC Polygraf allows a satisfactory analysis of esophageal pressure signals. However, only perfused catheters offer an excellent reliability for complete studies of both sphincter and peristaltism.

Adult↗

PubMed1998

Photoelastic stress analysis in a pier retainer of an anterior resin-bonded fixed partial denture.

STATEMENT OF PROBLEM: A clinical situation may arise with 2 edentulous spaces and a single intact pier tooth. A dentist may restore these edentulous spaces with a long span resin-bonded fixed partial denture using the pier and the 2 terminal abutments for bonding. PURPOSE: This study analyzed the stresses induced in a pier retainer of an anterior resin-bonded fixed partial denture and determined the effect on a pier abutment. MATERIAL AND METHODS: Photoelastic materials were selected to represent the relative stiffness of 3- and 5-unit resin-bonded fixed partial dentures. The models were scaled to x2.5 to enhance visual analysis of the stress pattern. RESULTS: Isochromatic fringes indicated a stress magnitude at the proximolingual areas of the pontic in the 3-unit resin-bonded fixed partial denture. In the 5-unit resin-bonded prosthesis, the stress pattern appeared to involve the entire surface of the pier retainer. CONCLUSION: The use of pier abutments should be avoided and it is more favorable to use 3-unit resin-bonded fixed partial dentures.

Dental Abutments↗

PubMed1985

Glucagon-evoked gastric dysrhythmias in humans shown by an improved electrogastrographic technique.

The objective of this study was to improve recording techniques for the recognition of gastric electrical dysrhythmias, and to explore the potential of pharmacologic agents to "evoke" gastric dysrhythmias. Eighteen healthy volunteers participated in 22 individual recordings, divided into two separate studies--a dose-response study and a randomized, double-blind study. The internal or mucosal electrogastrogram was recorded with a novel approach, using magnetic force to maintain internal electrodes in apposition with the gastric wall, whereas the external or cutaneous electrogastrogram, manometric activity, and respiration were measured by conventional methods. Analysis of simultaneous internal and external electrogastrographic signals, including both dysrhythmia and dysrhythmia-free intervals, revealed a good correspondence between the internal and external signals. In the dose-response study, 5 of the 6 volunteers intravenously infused with glucagon, in doses ranging from 3 to 22 micrograms/kg, developed gastric electrical dysrhythmias. In the randomized, double-blind study, 4 of 5 volunteers intravenously infused with glucagon (7 micrograms/kg) developed gastric dysrhythmias that were recognized by our improved techniques. Dysrhythmias, defined by visual analysis, consisted either of "tachygastria" (greater than or equal to 6 cycles/min for greater than or equal to 1 min) or "bradygastria" (greater than or equal to 1 cycle/min for greater than or equal to 1 min) and were evident on both internal and external electrogastrograms. Dysrhythmias were usually associated with absence of antral phasic pressure activity and frequently with nausea.

Action Potentials↗

PubMed1998

Real-time automated detection and quantitative analysis of seizures and short-term prediction of clinical onset.

PURPOSE: We describe an algorithm for rapid real-time detection, quantitation, localization of seizures, and prediction of their clinical onset. METHODS: Advanced digital signal processing techniques used in time-frequency localization, image processing, and identification of time-varying stochastic systems were used to develop the algorithm, which operates in generic or adaptable "modes." The "generic mode" was tested on (a) 125 partial seizures (each contained in a 10-min segment) involving the mesial temporal regions and recorded using depth electrodes from 16 subjects, and (b) 205 ten-minute segments of randomly selected interictal (nonseizure) data. The performance of the algorithm was compared with expert visual analysis, the current "gold standard." RESULTS: The generic algorithm achieved perfect sensitivity and specificity (no false-positive and no false-negative detections) over the entire data set. Seizure intensity, a novel measure that seems clinically relevant, ranged between 35.7 and 6129. Detection was sufficiently rapid to allow prediction of clinical onset in 92% of seizures by a mean of 15.5 s. CONCLUSIONS: This algorithm, which was implemented with a personal computer, represents a definitive step toward rapid and accurate detection and prediction of seizures. It may also enable development of intelligent devices for automated seizure warning and treatment and stimulate new study of the dynamics of seizures and of the epileptic brain.

Algorithms↗

PubMed2006

Diagnostic value of kinetic analysis using dynamic FDG PET in immunocompetent patients with primary CNS lymphoma.

PURPOSE: The purpose of this study was to investigate the accumulation of FDG in immunocompetent patients with primary central nervous system (CNS) lymphoma using qualitative and quantitative PET images and to compare baseline with follow-up PET after therapy. METHODS: Twelve immunocompetent patients with CNS lymphoma were examined. Dynamic emission data were acquired for 60 min immediately following injection of FDG. In seven patients, repeated PET studies were performed after treatment. Applying a three-compartment five-parameter model, K (1), k (2), k (3), k (4), vascular fraction (V ( B )) and cerebral metabolic rate of glucose (CMR(Glc)) were obtained. We evaluated the FDG uptake visually using qualitative and parametric images and quantitatively using parametric images. RESULTS: A total of 12 lesions were identified in ten patients with newly diagnosed CNS lymphoma. On visual analysis, ten lesions showed an increase on qualitative images, eight showed an increase on K (1) images, 12 showed an increase on k (3) images and ten showed an increase on CMR(Glc) images. On quantitative analysis, k (2), k (3) and CMR(Glc) values of the lesion were significantly different from those of the normal grey matter (p<0.02-0.0005). A total of three lesions were identified in two patients with recurrent tumour. All three lesions showed an increase on qualitative, k (3) and CMR(Glc) images. The K (1), k (2), k (3) and CMR(Glc) values after treatment were significantly different from those obtained before treatment (p<0.04-0.008). CONCLUSION: Kinetic analysis, especially with respect to k (3), using dynamic FDG PET might be helpful for diagnosis of CNS lymphoma and for monitoring therapeutic assessment.

Adult↗

PubMed1983

Cytologic and molecular analysis of 46,XXq- cells to identify a DNA segment that might serve as a probe for a putative human X chromosome inactivation center.

Cloned human X chromosome-specific DNA segments, derived from a recombinant phage library enriched for the human X and previously localized to different regions of the X, were used as probes in Southern blots to confirm the nature of a deletion of the long arm of the X chromosome as del(X)(q13) in a patient with some features of Turner's syndrome and suspected from cytologic studies to have a 46,XXq- karyotype. Two dimensional scanning densitometry of autoradiograms of the Southern blots was used to quantitate hybridization of the 32P-labeled probes, reinforcing visual analysis and permitting distinction between sequences present at one or two copies per diploid genome. Once thus characterized, DNA from the patient's cells was used in quantitatively analyzed Southern blots to refine the location of an additional DNA segment, previously mapped to somewhere in the proximal part of the long arm of the X chromosome, to the juxtacentromeric region of Xq, which has been hypothesized to be critical for X-inactivation. Cloned DNA probes such as that localized to the juxtacentromeric region of Xq should be useful for evaluating this hypothesis.

Absorptiometry, Photon↗

PubMed2006

Mapping implied body actions in the human motor system.

The human visual system is highly tuned to perceive actual motion as well as to extrapolate dynamic information from static pictures of objects or creatures captured in the middle of motion. Processing of implied motion activates higher-order visual areas that are also involved in processing biological motion. Imagery and observation of actual movements performed by others engenders selective activation of motor and premotor areas that are part of a mirror-neuron system matching action observation and execution. By using single-pulse transcranial magnetic stimulation, we found that the mere observation of static snapshots of hands suggesting a pincer grip action induced an increase in corticospinal excitability as compared with observation of resting, relaxed hands, or hands suggesting a completed action. This facilitatory effect was specific for the muscle that would be activated during actual execution of the observed action. We found no changes in responsiveness of the tested muscles during observation of nonbiological entities with (e.g., waterfalls) or without (e.g., icefalls) implied motion. Thus, extrapolation of motion information concerning human actions induced a selective activation of the motor system. This indicates that overlapping motor regions are engaged in the visual analysis of physical and implied body actions. The absence of motor evoked potential modulation during observation of end posture stimuli may indicate that the observation-execution matching system is preferentially activated by implied, ongoing but not yet completed actions.

Adult↗

PubMed1997

Comparative study of interictal PET and ictal SPECT in complex partial seizures.

OBJECTIVE: To compare the sensitivity of ictal 99mTc-HMPAO single photon emission computed tomography (SPECT) with interictal 18F-fluoro-deoxyglucose positron emission tomography (PET) in localization of the epileptogenic focus in patients with medically intractable complex partial seizures (MI-CPS). MATERIAL AND METHODS: Retrospective analysis was performed on patients with MI-CPS who underwent anterior temporal lobectomy from January 1993 onwards when PET became available to us for clinical studies at the Indiana University Medical Center. There were 38 female and 29 male patients (total = 67) with MI-CPS, 10 to 55.5 years of age (mean 31) and duration of their epilepsy from 1-46 years (mean 21). Interictal PET was evaluated for evidence of focal hypometabolism and ictal SPECT for focal perfusion abnormality (hyperperfusion or hypoperfusion) by visual analysis. RESULTS: Both ictal SPECT and interictal FDG-PET studies were obtained in 36 patients with MI-CPS. PET showed definite hypometabolism in 30 and questionable hypometabolism in an additional two patients. Ictal SPECT correctly localized the seizure focus in 27 patients by demonstrating ictal hyperperfusion whereas in one the hyperperfusion was falsely localized. In an additional seven patients the ictal SPECT provided probable localization by demonstrating ictal hypoperfusion in the appropriate temporal lobe. The sensitivity of ictal SPECT and interictal PET was 34/36 and 32/36, respectively, the difference was not statistically significant (chi 2y = 0.18, DF = 1, P = 0.67). In six of the 36 patients the two tests were complementary to each other in providing localizing information. CONCLUSION: Ictal SPECT and interictal PET are equally sensitive and reliable techniques in localizing the epileptogenic focus in patients with MI-CPS. They play a critical role in providing localization in MRI negative patients allowing surgical resection to be undertaken in many without additional invasive electrographic monitoring.

Adolescent↗

PubMed1979

"Circumferential profiles:" a new method for computer analysis of thallium-201 myocardial perfusion images.

A method for computer analysis of thallium-201 scintigrams is described, in which the left-ventricular activity is measured along radii constructed from the center of the left ventricle (LV) to each point on the LV circumference. Data are then displayed graphically as a "circumferential profile" of normalized activity against radial location. Thallium defects are identified and scored by comparison of the profile curve with empirically determined normal limits. In patients with coronary artery disease, defect scores were found to be quantitative and reproducible, and to agree generally with subjective visual analysis.

Adult↗