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Results for “Pattern Recognition, Physiological”

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At least 595 records · Page 33Linked to original sources
PubMed2003

DMBT1, a regulator of mucosal homeostasis through the linking of mucosal defense and regeneration?

DMBT1 (deleted in malignant brain tumor 1), which encodes a large scavenger receptor cysteine rich (SRCR) B protein, has been proposed to be a tumor suppressor gene, due to the high frequency of its homozygous deletion and the lack of expression in a variety of cancers. However, studies on its physiological functions and its relationship with tumorigenesis are still at an initial stage. Two mucosal defense-related molecules, gp-340 and salivary agglutinin, have been identified to be alternatively spliced products of DMBT1, which suggests that DMBT1 is a pattern recognition receptor in innate immunity. Meanwhile, results from immunohistochemical staining and studies at the cellular level, began to associate DMBT1 with a proliferation to differentiation switching process in gastrointestinal epithelial cells. Together with its up-regulation in inflammation, these findings suggest that DMBT1 might be a local regulator of homeostasis, possibly through linking mucosal inflammation to the modulation of epithelial regeneration, and whose abnormality is a frequent cause of malignancy.

Agglutinins↗
PubMed1990

Prolactin and related peptides in pregnancy.

This brief review has attempted to portray the complex involvement of prolactin in pregnancy. Pituitary prolactin production and lactotroph proliferation are markedly affected by oestrogens and pregnancy. Enlargement of pre-existing prolactinomas may occur during pregnancy induced with dopamine agonist drugs, and this can be a major clinical problem with larger tumours. Prolactin is produced by late luteal and decidualized endometrium as well as by the pituitary gland, but much less is known about its secretory regulation or its function. The family of prolactin-related protein hormones is rapidly expanding with the recognition of placental lactogens, variant growth hormone, proliferin, decidual luteotropin, and at least two further prolactin-related peptides in rodents. This complex system of related but distinct protein hormones, with different temporal patterns of production during gestation, suggests an important physiological role, but it remains to be seen to what extent they are involved in placental function itself, maternal metabolism or fetal growth.

Animals↗
PubMed1990

Moon illusion in pictures: a multimechanism approach.

The existence of the moon illusion in pictorial representations was demonstrated in 6 experiments. Ss either judged the size of the moon in pictures, depicted as on the horizon or high in the sky, or drew horizon and elevated moons. The horizon moon was consistently judged to be larger than the elevated moon, independent of the angle at which the pictures are viewed. The distance paradox usually observed with the moon illusion (horizon moon apparently closer than the elevated moon) also exists in pictures. The magnitude of both size and distance effects depends on the salience of depicted depth cues. The pattern of results suggests that the moon illusion is caused by several interacting mechanisms and that use of pictorial stimuli may allow the separation of various cognitive from physiological contributions to the illusion.

Attention↗
PubMed2005

Innate control of adaptive immunity via remodeling of lymph node feed arteriole.

The adaptive immune system relies on rare cognate lymphocytes to detect pathogen-derived antigens. Naïve lymphocytes recirculate through secondary lymphoid organs in search of cognate antigen. Here, we show that the naïve-lymphocyte recirculation pattern is controlled at the level of innate immune recognition, independent of antigen-specific stimulation. We demonstrate that inflammation-induced lymphocyte recruitment to the lymph node is mediated by the remodeling of the primary feed arteriole, and that its physiological role is to increase the efficiency of screening for rare antigen-specific lymphocytes. Our data reveal a mechanism of innate control of adaptive immunity: by increasing the pool of naïve lymphocytes for detection of foreign antigens via regulation of vascular input to the local lymph node.

Animals↗
PubMedDate not supplied

Context and occasion setting in Drosophila visual learning.

In a permanently changing environment, it is by no means an easy task to distinguish potentially important events from negligible ones. Yet, to survive, every animal has to continuously face that challenge. How does the brain accomplish this feat? Building on previous work in Drosophila melanogaster visual learning, we have developed an experimental methodology in which combinations of visual stimuli (colors and patterns) can be arranged such that the same stimuli can either be directly predictive, indirectly predictive, or nonpredictive of punishment. Varying this relationship, we found that wild-type flies can establish different memory templates for the same contextual color cues. The colors can either leave no trace in the pattern memory template, leading to context-independent pattern memory (context generalization), or be learned as a higher-order cue indicating the nature of the pattern-heat contingency leading to context-dependent memory (occasion setting) or serve as a conditioned stimulus predicting the punishment directly (simple conditioning). In transgenic flies with compromised mushroom-body function, the sensitivity to these subtle variations is altered. Our methodology constitutes a new concept for designing learning experiments. Our findings suggest that the insect mushroom bodies stabilize visual memories against context changes and are not required for cognition-like higher-order learning.

Adaptation, Physiological↗
PubMed2006

Training cellular automata for image processing.

Experiments were carried out to investigate the possibility of training cellular automata (CA) to perform several image processing tasks. Even if only binary images are considered, the space of all possible rule sets is still very large, and so the training process is the main bottleneck of such an approach. In this paper, the sequential floating forward search method for feature selection was used to select good rule sets for a range of tasks, namely noise filtering (also applied to grayscale images using threshold decomposition), thinning, and convex hulls. Various objective functions for driving the search were considered. Several modifications to the standard CA formulation were made (the B-rule and two-cycle CAs), which were found, in some cases, to improve performance.

Algorithms↗
PubMed2006

Symmetric and asymmetric multi-modality biclustering analysis for microarray data matrix.

Machine learning techniques offer a viable approach to cluster discovery from microarray data, which involves identifying and classifying biologically relevant groups in genes and conditions. It has been recognized that genes (whether or not they belong to the same gene group) may be co-expressed via a variety of pathways. Therefore, they can be adequately described by a diversity of coherence models. In fact, it is known that a gene may participate in multiple pathways that may or may not be co-active under all conditions. It is therefore biologically meaningful to simultaneously divide genes into functional groups and conditions into co-active categories--leading to the so-called biclustering analysis. For this, we have proposed a comprehensive set of coherence models to cope with various plausible regulation processes. Furthermore, a multivariate biclustering analysis based on fusion of different coherence models appears to be promising because the expression level of genes from the same group may follow more than one coherence models. The simulation studies further confirm that the proposed framework enjoys the advantage of high prediction performance.

Algorithms↗
PubMed2006

Metabolic pathways variability and sequence/networks comparisons.

BACKGROUND: In this work a simple method for the computation of relative similarities between homologous metabolic network modules is presented. The method is similar to classical sequence alignment and allows for the generation of phenotypic trees amenable to be compared with correspondent sequence based trees. The procedure can be applied to both single metabolic modules and whole metabolic network data without the need of any specific assumption. RESULTS: We demonstrate both the ability of the proposed method to build reliable biological classification of a set of microorganisms and the strong correlation between the metabolic network wiring and involved enzymes sequence space. CONCLUSION: The method represents a valuable tool for the investigation of genotype/phenotype correlations allowing for a direct comparison of different species as for their metabolic machinery. In addition the detection of enzymes whose sequence space is maximally correlated with the metabolic network space gives an indication of the most crucial (on an evolutionary viewpoint) steps of the metabolic process.

Algorithms↗
PubMed2003

[Physiological basis of visual acuity measurement].

The paper presents information about types of acuity tasks, visual acuity limitations and contrast sensitivity function. Measurements of resolution acuity may be interpreted as estimates of spatial density of the mosaic of photoreceptors and ganglion cells of the living human eye. Physiological basis such as Raleigh's criteria, sampling theory and filtering theory of visual resolution are described.

Form Perception↗
PubMed1991

Postnatal development of cardiac and respiratory control following prenatal drug exposure.

Of primary importance in the consideration of animal models of prenatal drug exposure is the recognition of interdependence among physiologic systems, the pervading influence of sleep and waking states, and the potential interaction between drug-induced structural changes and physiologic function. It is difficult for a drug effect on the cardiovascular system not to modify respiratory pattern; any change in blood pressure, systemic perfusion, or heart rate is immediately reflected in breathing; respiratory pattern, in turn, through negative thoracic pressure and other sensory activity, can alter cardiac patterning. The respiratory system itself is one component of a somatic motor system, and neural motor control structures undergo substantial modification by drug action. Enhancing or diminishing any aspect of interaction is the influence of sleep states, which nonlinearly can alter relationships between physiologic systems, occasionally dissociating systems, as in the case of temperature effects on breathing during REM sleep. Finally, drug-induced structural changes that alter morphology of the upper airway can result in obstructive respiratory events, leading to pronounced cardiovascular sequelae.

Child, Preschool↗
PubMed1994

Effects of memory load on interhemispheric relay.

Experimentation with unilateral and bilateral tachistoscopic stimulation (the Dimond paradigm) increasingly suggests that interhemispheric cooperation (bilateral advantage) occurs or increases as a function of task complexity in general and memory load in particular. However, tachistoscopic experimentation with ipsilateral and contralateral field/hand relation conditions (the Poffenberger paradigm) has failed to provide any conclusive supporting evidence. The present investigation comprised a Sternberg "high speed memory scanning" task, modified as a go/no-go task, and formatted into the Poffenberger paradigm. Sets of items to be scanned (memory load) varied in size from one to four. A highly significant effect of load and a significant field/hand interaction were found, but the field/hand/load interaction did not reach significance. We concluded that the interhemispheric transfer time (ITT) metric drawn from this paradigm is not reliably sensitive to increasing memory load. However, our finding of significantly longer ITT in women than in men suggests that commissural anatomy and physiology may be sexually dimorphic.

Adult↗
PubMed1999

Auditory-visual integration during multimodal object recognition in humans: a behavioral and electrophysiological study.

The aim of this study was (1) to provide behavioral evidence for multimodal feature integration in an object recognition task in humans and (2) to characterize the processing stages and the neural structures where multisensory interactions take place. Event-related potentials (ERPs) were recorded from 30 scalp electrodes while subjects performed a forced-choice reaction-time categorization task: At each trial, the subjects had to indicate which of two objects was presented by pressing one of two keys. The two objects were defined by auditory features alone, visual features alone, or the combination of auditory and visual features. Subjects were more accurate and rapid at identifying multimodal than unimodal objects. Spatiotemporal analysis of ERPs and scalp current densities revealed several auditory-visual interaction components temporally, spatially, and functionally distinct before 200 msec poststimulus. The effects observed were (1) in visual areas, new neural activities (as early as 40 msec poststimulus) and modulation (amplitude decrease) of the N185 wave to unimodal visual stimulus, (2) in the auditory cortex, modulation (amplitude increase) of subcomponents of the unimodal auditory N1 wave around 90 to 110 msec, and (3) new neural activity over the right fronto-temporal area (140 to 165 msec). Furthermore, when the subjects were separated into two groups according to their dominant modality to perform the task in unimodal conditions (shortest reaction time criteria), the integration effects were found to be similar for the two groups over the nonspecific fronto-temporal areas, but they clearly differed in the sensory-specific cortices, affecting predominantly the sensory areas of the nondominant modality. Taken together, the results indicate that multisensory integration is mediated by flexible, highly adaptive physiological processes that can take place very early in the sensory processing chain and operate in both sensory-specific and nonspecific cortical structures in different ways.

Acoustic Stimulation↗
PubMed2002

Objective detection of brainstem auditory evoked potentials with a priori information from higher presentation levels.

This paper describes a brainstem auditory evoked potentials (BAEPs) detection method based on supervised pattern recognition. A previously used pattern recognition technique relying on cross-correlation with a template was modified in order to include a priori information allowing detection accuracy. Reference is made to the patient's audiogram and to the latency-intensity (LI) curve with respect to physiological mechanisms. Flexible and adaptive constraints are introduced in the optimization procedure by means of eight rules. Several data samples were used in this study. The determination of parameters was performed through 270 BAEPs from 20 subjects with normal and high audiometric thresholds and through additional BAEPs from 123 normal ears and 14 ears showing prominent wave VI BAEPs. The evaluation of the detection performance was performed in two steps: first, the sensitivity, specificity and accuracy were estimated using 283 BAEPs from 20 subjects showing normal and high audiometric thresholds and secondly, the sensitivity, specificity and accuracy of the detection and the accuracy of the response threshold were estimated using 213 BAEPs from 18 patients in clinic. Taking into account some a priori information, the accuracy in BAEPs detection was enhanced from 76 to 90%. The patient response thresholds were determined with a mean error of 5 dB and a standard deviation error of 8.3 dB. Results were obtained using experimental data; therefore, they are promising for routine use in clinic.

Audiometry↗
PubMedDate not supplied

Toxicogenomics, drug discovery, and the pathologist.

The field of toxicogenomics, which currently focuses on the application of large-scale differential gene expression (DGE) data to toxicology, is starting to influence drug discovery and development in the pharmaceutical industry. Toxicological pathologists, who play key roles in the development of therapeutic agents, have much to contribute to DGE studies, especially in the experimental design and interpretation phases. The intelligent application of DGE to drug discovery can reveal the potential for both desired (therapeutic) and undesired (toxic) responses. The pathologist's understanding of anatomic, physiologic, biochemical, immune, and other underlying factors that drive mechanisms of tissue responses to noxious agents turns a bewildering array of gene expression data into focused research programs. The latter process is critical for the successful application of DGE to toxicology. Pattern recognition is a useful first step, but mechanistically based DGE interpretation is where the long-term future of these new technologies lies. Pathologists trained to carry out such interpretations will become important members of the research teams needed to successfully apply these technologies to drug discovery and safety assessment. As a pathologist using DGE, you will need to learn to read DGE data in the same way you learned to read glass slides, patiently and with a desire to learn and, later, to teach. In return, you will gain a greater depth of understanding of cell and tissue function, both in health and disease.

Animals↗
PubMed2004

Depth of word processing in Alzheimer patients and normal controls: a magnetoencephalographic (MEG) study.

Effects related to depth of verbal information processing were investigated in probable Alzheimer's disease patients (AD) and age matched controls. During word encoding sessions 10 patients and 10 controls had either to decide whether the letter "s" appeared in visually presented words (alphabetical decision, shallow encoding), or whether the meaning of each presented word was animate or inanimate (lexical decision, deep encoding). These encoding sessions were followed by test sessions during which all previously encoded words were presented again together with the same number of new words. The task was then to discriminate between repeated and new words. Magnetic field changes related to brain activity were recorded with a whole cortex MEG.5 probable AD patients showed recognition performances above chance level related to both depths of information processing. Those patients and 5 age matched controls were then further analysed. Recognition performance was poorer in probable AD patients compared to controls for both levels of processing. However, in both groups deep encoding led to a higher recognition performance than shallow encoding. We therefore conclude that the performance reduction in the patient group was independent of depth of processing. Reaction times related to false alarms differed between patients and controls after deep encoding which perhaps could already be used for supporting an early diagnosis. The analysis of the physiological data revealed significant differences between correctly recognised repetitions and correctly classified new words (old/new-effect) in the control group which were missing in the patient group after deep encoding. The lack of such an effect in the patient group is interpreted as being due to the respective neuropathology related to probable AD. The present results demonstrate that magnetic field recordings represent a useful tool to physiologically distinguish between probable AD and age matched controls.

Aged↗
PubMedDate not supplied

Clinical skills: the physiological basis and interpretation of the ECG.

Electrocardiograph (ECG) interpretation is a complex subject that requires considerable experience. However, an understanding of the principles underlying generation of the ECG can make this learning process easier. This knowledge is necessary if interpretation is to be founded on understanding rather than being a pattern recognition-based process. The aim of this article is to introduce the practitioner to the basic processes and mechanisms that govern formation of the normal ECG. These principles will largely be applied to the normal ECG and include cardiac anatomy applied to the ECG, how the ECG leads look at the heart and how the normal ECG waveform is formed. Examples of how the ECG changes when the underlying mechanisms are disturbed will also be given. Together, this knowledge should help the practitioner to have a clearer understanding of interpreting the abnormalities seen on an ECG.

Arrhythmias, Cardiac↗
PubMed1990

Simulation of movement detection by direction-selective ganglion cells in the rabbit and squirrel retina.

A veto-gate model of movement detection by direction-selective ganglion cells in the vertebrate retina, first proposed by Barlow and Levick (1965), provides the basis for a model described in this study. The model is a simple network consisting basically of (1) two subunits that have receptive fields with a center-surround organization and an adaptational gain control, (2) a lateral inhibitory pathway, (3) a site of nonlinear interaction, followed by (4) a leaky temporal integrator. The model is tested by comparing its basic properties to those reported in the physiological literature on rabbit and squirrel direction-selective retinal ganglion cells. It is shown that the physiological findings on sensitivity to flashes, moving spots or slits, and phi-movement stimuli, can be mimicked quite well by our model. Similarities between the component processes of the subunits and known retinal processes are pointed out. The simulation studies shed a new light on some of the known properties and suggest several new, more revealing, physiological experiments. Such experiments are necessary to develop a full specification of this type of model and to fix more parameter values than is possible at present. Results of some critical experiments are predicted to enable physiologists to falsify or corroborate the model. The simulation studies also help to distinguish use from abuse of this type of model in explanations of psychophysical findings. For example, neither the most complete Barlow-Levick detector nor any stripped-down versions that retain a temporally extended lateral inhibition (which is essential to mimick the physiological findings), respond well to moving random-pixel arrays.

Animals↗
PubMed1998

Detection of global structure in Glass patterns: implications for form vision.

Glass (Nature 1969;223:578-580) patterns are random dot stimuli that generate a percept of global structure. To study the mechanisms underlying this global form perception, concentric, radial, hyperbolic, and parallel Glass patterns were constructed. Thresholds for detecting each type of pattern were measured by degrading the patterns through the addition of noise. Concentric patterns yielded the lowest thresholds for all subjects, while radial and hyperbolic patterns produced somewhat higher thresholds. For all subjects the parallel patterns produced the highest thresholds. Threshold measurements as a function of the area containing pattern structure provided evidence for global pooling of orientation information in the detection of radial and concentric Glass patterns but only local pooling in the detection of parallel patterns. Monte-Carlo simulations demonstrate that plausible neural models can accurately predict the data. These models indicate that the visual system contains networks that pool orientation information within regions 3.5-4.5 degrees in diameter in central vision. This pooling is organized to extract cross-shaped, X-shaped, and quasi-circular forms from the retinal image. The results are in good agreement with recent single unit physiology of primate area V4, an intermediate level of the form vision pathway.

Computer Graphics↗