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PubMed2006

Characterization of surface EMG signals using improved approximate entropy.

An improved approximate entropy (ApEn) is presented and applied to characterize surface electromyography (sEMG) signals. In most previous experiments using nonlinear dynamic analysis, this certain processing was often confronted with the problem of insufficient data points and noisy circumstances, which led to unsatisfactory results. Compared with fractal dimension as well as the standard ApEn, the improved ApEn can extract information underlying sEMG signals more efficiently and accurately. The method introduced here can also be applied to other medium-sized and noisy physiological signals.

Algorithms↗
PubMed1996

Sialyl-Lewis x and Sialyl-Lewis a are associated with MUC1 in human endometrium.

Endometrial epithelial cells express MUC1 with increased abundance in the secretory phase of the menstrual cycle, when embryo implantation occurs. MUC1 is associated with the apical surface of epithelial cells and is also secreted, being detectable in uterine fluid at elevated levels in the implantation phase. However, its physiological role is uncertain; it may either inhibit intercellular adhesion by steric hindrance or carry carbohydrate recognition structures capable of mediating cell-cell interaction. Here we show that endometrial epithelium expresses both Sialyl-Lewis x (SLex) and Sialyl-Lewis a (SLea), with a distribution and pattern of menstrual cycle regulation similar to that of MUC1. Using Western blotting and double determinant ELISA of uterine flushings, we demonstrate that SLex is associated with MUC1 core protein. The endometrial carcinoma cell lines HEC1A and HEC1B are shown to express MUC1 in a mosaic pattern, while three other cell lines express much lower amounts. HEC1A expresses both SLex and SLea while HEC1B expresses SLea only. Immunoprecipitation has been used to demonstrate that SLea is associated with MUC1 in HEC1B cells, and both SLex and SLea are associated with MUC1 in HEC1A cells.

Antibodies, Monoclonal↗
PubMed2003

Rana computatrix to human language: towards a computational neuroethology of language evolution.

Walter's Machina speculatrix inspired the name Rana computatrix for a family of models of visuomotor coordination in the frog, which contributed to the development of computational neuroethology. We offer here an 'evolutionary' perspective on models in the same tradition for rat, monkey and human. For rat, we show how the frog-like taxon affordance model provides a basis for the spatial navigation mechanisms that involve the hippocampus and other brain regions. For monkey, we recall two models of neural mechanisms for visuomotor coordination. The first, for saccades, shows how interactions between the parietal and frontal cortex augment superior colliculus seen as the homologue of frog tectum. The second, for grasping, continues the theme of parieto-frontal interactions, linking parietal affordances to motor schemas in premotor cortex. It further emphasizes the mirror system for grasping, in which neurons are active both when the monkey executes a specific grasp and when it observes a similar grasp executed by others. The model of human-brain mechanisms is based on the mirror-system hypothesis of the evolution of the language-ready brain, which sees the human Broca's area as an evolved extension of the mirror system for grasping.

Adaptation, Physiological↗
PubMed1985

The bionic ear: principles and current status of cochlear prostheses.

The field of cochlear prostheses is reviewed, emphasizing the neurophysiological principles necessary for the development of a successful cochlear prosthesis. Pertinent auditory physiology is reviewed, and four conditions are proposed which, if met, should result in speech recognition by the patient with an implant. These conditions are: The surviving neural population must be adequate over the frequency distribution required to deliver the necessary information for speech discrimination. The central neural processing pattern for decoding and recognizing speech must have been established and still persist. The processing of the acoustic signal by the auditory system up to the level of the prosthesis interface must be understood and predictable from the acoustic stimulus. The relationship between the response patterns of the neural elements and the electrical stimulus must be well documented and controllable. The degree to which these conditions can presently be met is discussed, with some suggestions for future development. The function of the cochlear prosthesis is separated into a signal processing section and an electrical stimulus section. Two signal processing strategies are analog processing of the acoustic signal and speech feature extraction from the acoustic signal. Four possible electrical stimulation strategies are direct analog stimulation from the signal processor, pulse amplitude modulation, pulse width modulation, and stimulation designed to optimize the neural responses to electrical stimulation. Some of the present generation cochlear prostheses, including five approved by the FDA as investigational devices, are discussed according to this classification. The clinical results of testing these devices as aids to lip reading and as stand-alone speech reception aids are compared. All are a potential aid to lip reading. Some prosthesis designs have been implanted in patients who then showed exceptional open set speech discrimination. These exceptional patients have used both single channel and multichannel devices and devices with both analog processing and speech feature extraction strategies. These results are encouraging. More consistent and better speech reception is anticipated for the future as this field develops.

Auditory Pathways↗
PubMed2005

Using functional magnetic resonance imaging to assess adaptation and size invariance of shape processing by humans and monkeys.

Functional magnetic resonance imaging in awake monkeys and humans was used to compare object adaptation in shape-sensitive regions of these two species under identical and different size conditions. Object adaptation was similar in humans and monkeys under both conditions. Neither species showed complete size invariance, in agreement with single-cell studies. Both the macaque inferotemporal (IT) complex and human lateral occipital complex (LOC) displayed an anteroposterior gradient in object adaptation and size invariance, with the more anterior regions being more adaptable and size invariant. The results provide additional evidence for the homology between the macaque IT cortex and human LOC but also add to the growing list of differences between human and monkey intraparietal sulcus regions.

Adaptation, Physiological↗
PubMed1979

Interpretation of blood gas analysis by physicians in a community teaching hospital.

Forty-two interns and residents on the staff of a community teaching hospital were questioned to assess their understanding of blood gas abnormalities. Misunderstandings were such that 24% of the residents and interns might have given inadequate care had their interpretations dictated practice. Few therapeutic misadventures in fact occurred, largely because of supervision. Even without supervision, it is unlikely that much harm would have come about, partly because pattern recognition and rules of thumb provided adequate guidance and partly because no notice was taken of the results of the blood gas analysis anyway. Those who wish to promote rational practice should direct their educational efforts to improved understanding of the mechanisms of hypoxaemia and of the chemical, physiological and pathophysiological interactions of PCO2, bicarbonate and pH in the various acid-base disorders.

Blood Gas Analysis↗
PubMed1996

Cortical oscillatory responses do not affect visual segmentation.

We tested the hypothesis that synchronization of oscillatory responses between populations of visually driven neurons could be the basis for visual segmentation and perceptual grouping. We reasoned that oscillations in response induced by flickering visual targets should have an effect on visual performance in these tasks. We therefore measured the psychophysical performance of human subjects in a texture segregation task. (Expt I) and in a perceptual grouping task (Expt II). In both experiments, the elements composing the stimuli were flickered and presented in a variety of flicker conditions. These experimental conditions were designed to either interfere with naturally occurring synchronization of oscillations, or to induce synchronization and bias a subject's perceptual judgment. Performance in these tasks was neither helped nor hindered by the temporal pattern of flicker. These results suggest that physiologically observed oscillatory responses are unrelated to the processes underlying visual segmentation and perceptual grouping.

Differential Threshold↗
PubMed2000

The implementation of visual routines.

Many visual tasks can be decomposed into a sequence of simpler subtasks. Ullman suggested that such subtasks are carried out by elemental operations that are implemented by specialized processes in the visual brain [Ullman, S. (1984). Visual routines. Cognition (18), 97-159]. According to this hypothesis, there are a limited number of elemental operations that, since they can be applied sequentially, may nevertheless give rise to a large number of visual routines. Examples of such elemental operations are visual search, texture segregation and contour grouping. Here we attempt to delineate how such elemental operations are implemented in the visual brain. When an image appears, feedforward processing rapidly leads to an activity pattern that is distributed across many visual areas. Thereafter, elemental operations come into play, and these are implemented by the modulation of firing rates. Firing rate modulations effectuate grouping of neural responses into coherent object representations. Moreover, they permit transfer of information from one operator to the next, which allows flexibility in the sequencing of operations. We discuss how the elemental operations provide a tool to relate cortical physiology to psychophysics, and suggest a reclassification of pre-attentive and attentive processes.

Animals↗
PubMed1996

Gratings that induce perceptual distortions mask superimposed targets.

Masking is known to depend upon the relationship between the spatial-frequency content of target and mask. This relationship has been held constant in three experiments in order to investigate the separate contribution of the spatial parameters of the mask, in this case a grating with square-wave luminance profile. Thresholds for the detection of a probe target were highest when the background grating upon which the probe was superimposed had a spatial frequency of about 4 cycles deg-1 (experiment 1) and a duty cycle of 50% (experiment 3). In experiment 2, the thresholds were strongly affected by the size of the background grating even though the size of the target was small in proportion to the grating and remained constant. The increase in threshold was linearly related to the area of visual cortex to which the grating projected. The spatial parameters of gratings that maximise masking are therefore the same as those that have been shown to be optimal for the induction of perceptual distortions, suggesting a possible physiological mechanism for both the masking and the distortions.

Adult↗
PubMed2000

Tension and stretch receptors in gastrointestinal smooth muscle: re-evaluating vagal mechanoreceptor electrophysiology.

Electrophysiological and morphological analyses of vagal mechanoreceptors in the gut wall suggest conflicting conclusions. Electrophysiology has distinguished a single general class of ending in smooth muscle, one characterized as an 'in series' tension receptor. Morphology, in contrast, has characterized two distinct specializations of vagal afferent endings in the muscle wall of the gastrointestinal (GI) tract. These two structures differ in terms of their target tissues, terminal architectures and regional distributions; they also develop on different ontogenetic timetables and depend on different trophic support in the muscle wall. On the basis of these features, we have proposed that one of the putative mechanoreceptors, the intraganglionic laminar ending (IGLE), has characteristics of a tension receptor and the other, the intramuscular array (IMA), has features of a stretch or length receptor. In a functional analogy with striated muscle proprioceptors, IGLEs should have similarities to Golgi tendon organs, whereas IMAs should have equivalencies with muscle spindle afferents. The present survey re-examines the recording analyses in light of the structural observations. This review indicates that previous electrophysiological studies are too inconclusive to refute the inference that the vagus supplies two distinct types of mechanoreceptors to the muscle wall of the GI tract. Multiple methodological constraints and sources of variance have limited the resolution of electrophysiological experiments. Specifically, these experiments have conventionally used distension stimuli that confound tension and stretch. In addition, sampling strategies have biased recording experiments towards a focus on one type of ending, the IGLE. Furthermore, putative functional properties (e.g., broad tuning) of vagal mechanoreceptors suggest that distinguishing two recording patterns will require exacting protocols. Combining a recognition of the methodological difficulties that have limited electrophysiological analyses with an understanding of the structural features of the endings, however, suggests several critical electrophysiological experiments with the resolution to distinguish two classes of response profiles. Until such experiments can be conducted, sensory physiology's axiom that 'function varies with form', taken together with a re-assessment of the existing data, suggests that the vagus nerve supplies stretch receptors as well as tension receptors to the wall of the GI tract.

Animals↗
PubMedDate not supplied

Using conceptual triangulation to develop an integrated model of the symptom experience of acute rejection after lung transplantation.

The aim of this study was to develop a comprehensive model of the symptom experience associated with the development of acute rejection after lung transplantation by integrating the findings from a theory-testing quantitative study that explored the physiologic aspects and a theory-generating qualitative study that explored the interpretive aspects. Findings from the multimethod studies were integrated using conceptual triangulation methods described by Foster (Adv Nurs Sci. 1997;20:1-12). The integrated model will guide the development of interventions to promote effective patterns of symptom recognition and reporting of acute rejection.

Graft Rejection↗
PubMed1998

Free fatty acids (FFA), a link between obesity and insulin resistance.

Evidence, gained from human studies, is reviewed showing that elevation of plasma FFA levels produce peripheral and probably also hepatic insulin resistance in obese healthy and diabetic subjects. First, plasma FFA levels are elevated in most obese subjects. Second, physiological elevations of plasma FFA inhibit acutely as well as chronically insulin stimulated glucose uptake in a dose dependent fashion. Responsible for this inhibition is a FFA induced defect in insulin stimulated glucose transport and/or phosphorylation which develops after 3-4 hours of raising plasma FFA and a second defect, consisting of inhibition of glycogen synthase, the rate limiting enzyme of glycogen synthesis, which develops after 4-6 hours. FFA induced inhibition of fatty acid oxidation (Randle effect) does not affect insulin stimulated glucose uptake or glycogen synthesis and thus does not cause insulin resistance. Elevated plasma FFA levels also modestly increase insulin suppressed endogenous glucose production (EGP) although this effect has not been found by all investigators. The reasons why it has been difficult to demonstrate unequivocal effects of FFA on EGP include 1) the fact that FFA promote insulin secretion which counteracts its effect on EGP (FFA increase, while insulin decreases EGP); 2) the recognition that FFA induced increase in gluconeogenesis may be compensated by intrahepatic downregulation of EGP (i.e., by a decrease in glycogenolysis). The FFA induced insulin resistance is physiologically important during starvation by preserving carbohydrate for oxidation in the central nervous system and during pregnancy, where the well recognized accelerated starvation pattern provides carbohydrate for the growing fetus. In obesity, however, there is no need to spare carbohydrate and the FFA induced insulin resistance may result in type 2 diabetes and other cardiovascular risk factors.

Animals↗
PubMed1987

Computer database of ambulatory EEG signals.

The paper describes an ambulatory EEG database. The database contains segments of AEEGs done on 45 subjects. Each epoch (1/8th second or more) of AEEG data has been annotated into 1 of 40 classes. The classes represent background activity, paroxysmal patterns and artifacts. The majority of classes have over 200 discrete epochs. The structure is flexible enough to allow additional epochs to be readily added. The database is stored on transportable media such as digital magnetic tape or hard disk and is thus available to other researchers in the field. The database can be used to design, evaluate and compare EEG signal processing algorithms and pattern recognition systems. It can also serve as an educational medium in EEG laboratories.

Adolescent↗
PubMed2006

Hemodynamic patterns of blunt and penetrating injuries.

BACKGROUND: The aims of this prospective observational study were to describe early hemodynamic patterns of blunt and penetrating truncal injury and to evaluate outcomes prediction using noninvasive hemodynamic monitoring with a mathematical model tested against actual in-hospital outcomes. The hypothesis was that traumatic shock is a circulatory disorder that can be monitored by noninvasive hemodynamic parameters that reflect cardiac, pulmonary, and tissue perfusion functions. STUDY DESIGN: The cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SapO(2)), transcutaneous oxygen tension indexed to FiO(2) (PtcO(2)/FiO(2)), and carbon dioxide (PtcCO(2)) tensions were monitored beginning shortly after emergency department admission in 657 emergency patients with severe blunt and penetrating chest, abdominal, and extremity trauma. Of these, 113 patients had associated head injury, and these patients also were analyzed separately. A search and display mathematical model, with a decision support program, was based on continuous online, real-time, noninvasive hemodynamic monitoring. RESULTS: There were similar patterns in the blunt and penetrating injuries; the cardiac index, mean arterial pressure, pulse oximetry, transcutaneous oxygen tension indexed to FiO(2), and survival probability values of the survivors were significantly higher (p < 0.01) than the corresponding values of those who died, although heart rate and carbon dioxide tension were higher in the nonsurvivors during the first 24 hours after their emergency department admission. These patterns occurred more rapidly in patients with penetrating injuries. After initial resuscitation in the emergency department, results were correlated with actual outcomes at hospital discharge and found to be 88% correct. CONCLUSIONS: Early noninvasive hemodynamic monitoring with a computerized information system provided a feasible pattern recognition program for outcomes prediction and therapeutic decision support.

Adult↗
PubMedDate not supplied

Frequency and pattern of medical emergency team activation among medical cardiology patient care units.

Medical emergency teams are developing across the United States. The organization and implementation for a rapid response team to failing medical-surgical patients has been shown to reduce in-house cardiac arrest rates. Further investigation into the frequency and pattern for rapid response team calls has been shown to have a diurnal pattern and clustered around times associated with routine care activities. The medical emergency calls in the descriptive analysis reveal that calls to the medical cardiology units constitute--% of the total calls. The calls are found to be called with--frequency during the hours of 7 AM and 7 PM. The frequency of calls is shown to be clustered around the times of. The small descriptive analysis here suggests that further investigation in the patterns and monitoring of patient for early recognition to call for help is still needed.

Academic Medical Centers↗
PubMed1994

[Visual information processing in humans].

Recent advances in parallel information processing of primates and humans have been reviewed. First, I review what is known about physiology and anatomy of the primate visual pathways. Several lines of evidence suggest that the primate visual system consists of the parvocellular (P) and the magnocellular (M) pathways. M-system originates from the A retinal ganglion cells that project to the visual cortex (V1) via the magnocellular layers of the lateral geniculate nucleus (LGN). This system plays an important role for motion and stereopsis. P-system derives from the B retinal ganglion cells that project to V1 via the parvocellular layers of the LGN. This system shows selectivity for color vision and form perception. Second, I focus on the information processing of the human visual pathways. Psychophysical evidence suggests that there are also P and M systems in humans. However, there have been few electrophysiological studies which intend to separate the responses specific to P and M systems in human visual evoked potentials (VEPs). Based on the physiological distinctions between P and M systems, the use of isoluminant color patterns and apparent motion display allows us to evaluate P and M systems, respectively.

Animals↗
PubMedDate not supplied

Still confused about rose bengal?

We have surveyed the ophthalmic literature of the last five years in an attempt to evaluate the use and usefulness of Rose Bengal staining as an aid to differential diagnosis in dry eyes. Included both as a criterion and as an adjunct measure of disease progression, Rose Bengal scores of patients with different dry eye conditions overlap, sometimes to a considerable extent. A mechanistic link between staining with this dye and disease etiology is unlikely; however, Rose Bengal could be a surrogate marker of changes in ocular surface physiology. The question whether the extent and pattern of staining with Rose Bengal provide the clinician with information not available from other tests, and in particular from fluorescein staining of the ocular surface, has to be answered positively, though the nature of this information is not clearly understood. A more widespread recognition that Rose Bengal is not a vital dye is necessary in order not to bias the interpretation of experimental results.

Biomarkers↗
PubMed1990

Electrophysiological evidence for parallel and serial processing during visual search.

Event-related potentials were recorded from young adults during a visual search task in order to evaluate parallel and serial models of visual processing in the context of Treisman's feature integration theory. Parallel and serial search strategies were produced by the use of feature-present and feature-absent targets, respectively. In the feature-absent condition, the slopes of the functions relating reaction time and latency of the P3 component to set size were essentially identical, indicating that the longer reaction times observed for larger set sizes can be accounted for solely by changes in stimulus identification and classification time, rather than changes in post-perceptual processing stages. In addition, the amplitude of the P3 wave on target-present trials in this condition increased with set size and was greater when the preceding trial contained a target, whereas P3 activity was minimal on target-absent trials. These effects are consistent with the serial self-terminating search model and appear to contradict parallel processing accounts of attention-demanding visual search performance, at least for a subset of search paradigms. Differences in ERP scalp distributions further suggested that different physiological processes are utilized for the detection of feature presence and absence.

Adolescent↗