Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pattern Recognition, Physiological”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed2004

Components of motion perception revealed: two different after-effects from a single moving object.

If motion that one has been looking at for some time suddenly stops, or if one shifts one's gaze to a static object, one will see motion in the opposite direction: the motion after-effect. If two transparent surfaces move with different speeds in different directions, then the direction of the motion after-effect will depend on the test pattern. For such transparent surfaces both the local motion and the global percept have two components. When looking at a normal moving object, there is only one perceived global motion. However, we know that locally there can be considerable ambiguity (the aperture problem). Does one adapt to all the local components, including those that one does not perceive, or only to the perceived global motion? We designed a stimulus that is perceived to be a fast rotating object, but also has a slow local radial component of motion. By selecting an appropriate test pattern we could either get a radial or a rotating motion after-effect. Thus we show that adaptation to motion must (also) occur at a stage at which local motions have not yet been integrated to give a unified percept.

Adaptation, Physiological↗
PubMed2006

Evaluating shape after-effects with radial frequency patterns.

Mechanisms selective for complex shape are vulnerable to adaptation techniques historically used to probe those underlying performance in lower-level visual tasks. We explored the nature of these shape after-effects using radial frequency patterns. Adapting to a radial frequency pattern resulted in a strong and systematic after-effect of a pattern that was 180 degrees out of phase with the adapting pattern. This after-effect was characterized as both a shift in the point of subjective equality and an increase in response uncertainty. The after-effect transferred across adapting pattern contrast and adaptor amplitude, suggesting an involvement from shape-specific mechanisms located at higher processing stages along the visual pathway. Moreover, our results suggested that the shift in the point of subjective equality was guided by global processing mechanisms, whereas the increase in uncertainty reflected activity from local processing mechanisms. Together, these results suggest that shape-specific after-effects reflect gain control processes at various stages of processing along the ventral pathway.

Adaptation, Physiological↗
PubMed2002

Neural adjustments to image blur.

Blur is an intrinsic feature of retinal images that varies widely across images and observers, yet the world still typically appears 'in focus'. Here we examine the putative role of neural adaptation in the human perception of image focus by measuring how blur judgments depended on the state of adaptation. Exposure to unfocused images has previously been shown to influence acuity and contrast sensitivity, and here we show that adaptation can also profoundly affect the actual perception of image focus.

Adaptation, Physiological↗
PubMed2005

Improving the accuracy and reliability of motion tracking methods used for extracting temporal motor activity signals from video recordings of neonatal seizures.

This paper presents an approach for improving the accuracy and reliability of motion tracking methods developed for video based on block motion models. This approach estimates the displacement of a block of pixels between two successive frames by minimizing an error function defined in terms of the pixel intensities at these frames. The minimization problem is made analytically tractable by approximating the error function using a second-order Taylor expansion. The improved reliability of the proposed method is illustrated by its application in the extraction of temporal motor activity signals from video recordings of neonatal seizures.

Algorithms↗
PubMed2005

Automated extraction of temporal motor activity signals from video recordings of neonatal seizures based on adaptive block matching.

This paper presents an automated procedure developed to extract quantitative information from video recordings of neonatal seizures in the form of motor activity signals. This procedure relies on optical flow computation to select anatomical sites located on the infants' body parts. Motor activity signals are extracted by tracking selected anatomical sites during the seizure using adaptive block matching. A block of pixels is tracked throughout a sequence of frames by searching for the most similar block of pixels in subsequent frames; this search is facilitated by employing various update strategies to account for the changing appearance of the block. The proposed procedure is used to extract temporal motor activity signals from video recordings of neonatal seizures and other events not associated with seizures.

Algorithms↗
PubMed2000

Membrane potential and firing rate in cat primary visual cortex.

We have investigated the relationship between membrane potential and firing rate in cat visual cortex and found that the spike threshold contributes substantially to the sharpness of orientation tuning. The half-width at half-height of the tuning of the spike responses was 23 +/- 8 degrees, compared with 38 +/- 15 degrees for the membrane potential responses. Direction selectivity was also greater in spike responses (direction index, 0.61 +/- 0.35) than in membrane potential responses (0.28 +/- 0.21). Threshold also increased the distinction between simple and complex cells, which is commonly based on the linearity of the spike responses to drifting sinusoidal gratings. In many simple cells, such stimuli evoked substantial elevations in the mean potential, which are nonlinear. Being subthreshold, these elevations would be hard to detect in the firing rate responses. Moreover, just as simple cells displayed various degrees of nonlinearity, complex cells displayed various degrees of linearity. We fitted the firing rates with a classic rectification model in which firing rate is zero at potentials below a threshold and grows linearly with the potential above threshold. When the model was applied to a low-pass-filtered version of the membrane potential (with spikes removed), the estimated values of threshold (-54.4 +/- 1.4 mV) and linear gain (7.2 +/- 0.6 spikes. sec(-1). mV(-1)) were similar across the population. The predicted firing rates matched the observed firing rates well and accounted for the sharpening of orientation tuning of the spike responses relative to that of the membrane potential. As it was for stimulus orientation, threshold was also independent of stimulus contrast. The rectification model accounted for the dependence of spike responses on contrast and, because of a stimulus-induced tonic hyperpolarization, for the response adaptation induced by prolonged stimulation. Because gain and threshold are unaffected by visual stimulation and by adaptation, we suggest that they are constant under all conditions.

Action Potentials↗
PubMedDate not supplied

Computer-assisted ABR interpretation using the automatic construction of the latency-intensity curve.

In this paper, we present a new computerised technique for the automatic construction of the latency intensity curve (LI curve). We take a pattern recognition approach determined by a priori information. We use knowledge gained from the audiogram and from physiological considerations. Therefore, we consider all recordings at different intensities as well as results from the extraction of a single auditory brainstem response (ABR) at a given stimulus intensity. We tested our method successfully: it allows us to prevent misrecognition errors in response detection or in latency measurements. Automatic recognition of the waves and recognition by the ear, nose and throat (ENT) specialist coincided in at least 90 per cent of cases. For wave V, the average deviation between the response thresholds given by our automatic recognition algorithm and those given by the ENT specialist was 5 dB, and the average deviation of the latencies was 0.05 ms.

Auditory Threshold↗
PubMed1976

Effects of novelty and oddity on visual selective attention.

Effects of novelty and of oddity on selective attention was investigated through tachistoscopic recognition. When a pre-exposure field consisted of dots of one colour, letters of a different colour were more likely to be identified than letters of the same colour. In displays of 10 letters, two letters differing in colour from the remainder were more likely to be identified. Tachistoscopic exposure precluded determination of responses by eye movements, and there were controls for chromatic adaptation and other factors that might have biased the results.

Adaptation, Physiological↗
PubMed1977

Bronchial asthma of occupational origin: a review.

There are immediate benefits when one can establish the diagnosis of occupationally induced asthma. It is a man-made disease and is thus reversible. Diagnosis depends on knowledge of the source and types of exposure which can be correlated with the clinical, physiological and immunologic patterns of affected workers. The discovery of one case can often lead more readily to recognition of others. Individuals with asthma of an occupational origin should be removed from work. Equally as important is the initiation of proper industrial hygiene procedures which would improve the occupational environment and periodic medical surveillance of workers for the identification of early disease or individuals with few or no symptoms.

Allergens↗
PubMed2001

The 1.8-A crystal structure of a matrix metalloproteinase 8-barbiturate inhibitor complex reveals a previously unobserved mechanism for collagenase substrate recognition.

The individual zinc endoproteinases of the tissue degrading matrix metalloproteinase (MMP) family share a common catalytic architecture but are differentiated with respect to substrate specificity, localization, and activation. Variation in domain structure and more subtle structural differences control their characteristic specificity profiles for substrates from among four distinct classes (Nagase, H., and Woessner, J. F. J. (1999) J. Biol. Chem. 274, 21491-21494). Exploitation of these differences may be decisive for the design of anticancer or other drugs, which should be highly selective for their particular MMP targets. Based on the 1.8-A crystal structure of human neutrophil collagenase (MMP-8) in complex with an active site-directed inhibitor (RO200-1770), we identify and describe new structural determinants for substrate and inhibitor recognition in addition to the primary substrate recognition sites. RO200-1770 induces a major rearrangement at a position relevant to substrate recognition near the MMP-8 active site (Ala206-Asn218). In stromelysin (MMP-3), competing stabilizing interactions at the analogous segment hinder a similar rearrangement, consistent with kinetic profiling of several MMPs. Despite the apparent dissimilarity of the inhibitors, the central 2-hydroxypyrimidine-4,6-dione (barbiturate) ring of the inhibitor RO200-1770 mimics the interactions of the hydroxamate-derived inhibitor batimastat (Grams, F., Reinemer, P., Powers, J. C., Kleine, T., Pieper, M., Tschesche, H., Huber, R., and Bode, W. (1995) Eur. J. Biochem. 228, 830-841) for binding to MMP-8. The two additional phenyl and piperidyl ring substituents of the inhibitor bind into the S1' and S2' pockets of MMP-8, respectively. The crystal lattice contains a hydrogen bond between the O(gamma) group of Ser209 and N(delta)1 of His207 of a symmetry related molecule; this interaction suggests a model for recognition of hydroxyprolines present in physiological substrates. We also identify a collagenase-characteristic cis-peptide bond, Asn188-Tyr189, on a loop essential for collagenolytic activity. The sequence conservation pattern at this position marks this cis-peptide bond as a determinant for triple-helical collagen recognition and processing.

Amino Acid Sequence↗
PubMed1975

[Development and application possibilities of a computer-controlled microspectrophotometric system for cytoanalysis (CYTOS)].

A computer-assisted microspectrophotometric system for quantitative cell identification and data conversion, based on the scanned intracellular image pattern, will be introduced. The CYTOS system was developed with high flexibility for the analysis of general morphological and physiological problems of cell recognition and classification. The investigation include the quantitative transformation of extinction values in relation to cytomorphologic and cytochemical properties of a cell. In order to objectivate the subjective impression of visible or non-visible information, contained in a microscopic image, the measured extinction values were transformed in color values by a special developed interface. Each color shade corresponds to the intracellular substance concentration. The results, presented, concentrate on the CYTOS methodology, its application to the translation of data cytograms of DNA containing chromatic structures, and the intra-cytoplasmatic distribution pattern of enzyms. The CYTOS method might be considered as a useful technique revealing discrimination factors of diagnostical value.

Animals↗
PubMed2006

Kinesiological surface electromyography in normal children: range of normal activity and pattern analysis.

To document the range of activity and patterns of normal surface kinesiological electromyography in normal children, 87 children ranging from age 3 to 18 years who were developing normally were evaluated at free walking speed. Analysis was performed on 6307 gait cycles from 11 different muscles with custom software. We devised an algorithm to do a computer-based KEMG curve pattern analysis to sort out curves that did not match the physiologic muscle activity pattern, We also devised a combined preset amplitude and statistics-based criteria to satisfactorily determine the onset/cessation of KEMG activity. The measurements of timing and duration of activity, body height and weight, body mass index, cadence, stride length, and age were obtained for statistical analysis. From the pattern recognition, the medial and lateral hamstrings, gluteus maximus and medius, and gastrocnemius muscles had the highest percentage of clinically relevant curves. In most muscle groups, The KEMG curves had an average background activity of about 11-15% of maximum amplitude. The surface KEMG curves from normal subjects have 12.7% cycles that did not match their physiologic activity pattern. The timing and duration of KEMG activity was poorly or only fairly correlated with age, body height, body weight, and body mass index. The ensemble average of the linear envelope KEMG curves of each muscle could be applied as a normal database in a clinical gait analysis laboratory focusing on pediatric patients.

Adolescent↗
PubMed2000

[Recognition of multiple information of human auricular points by linear model].

The three variables of the electric characteristic of human auricular points can be regarded as observed targets that reflect the physiologic or pathologic changes. Medical principle design follows the theory of the channels and collaterals and the viscera-state doctrine of traditional Chinese medicine and that of the pattern recognition. The linear integration model can be established by drawing the characteristic variables of the correlation groups of the auricular points and applying the multi-variable normalization. With this model, the recognition of the three variations of the auricular points can be of use for differential diagnosis. In this paper, the test to identify the cases of Upper-Digestive tract achieves good result. This research, based on the integration of modern science with traditional Chinese medicine, provides a method for building the specialist system of the auricular point diagnosis, and probably has some prospect in clinical application.

Acupuncture Points↗
PubMed1994

Simulations of X and Y retinal ganglion cell behavior with a nonlinear push-pull model of spatiotemporal retinal processing.

This article describes a nonlinear model of neural processing in the vertebrate retina, comprising model photoreceptors, model push-pull bipolar cells, and model ganglion cells. Previous analyses and simulations have shown that with a choice of parameters that mimics beta cells, the model exhibits X-like linear spatial summation (null response to contrast-reversed gratings) in spite of photoreceptor nonlinearities; on the other hand, a choice of parameters that mimics alpha cells leads to Y-like frequency doubling. This article extends the previous work by showing that the model can replicate qualitatively many of the original findings on X and Y cells with a fixed choice of parameters. The results generally support the hypothesis that X and Y cells can be seen as functional variants of a single neural circuit. The model also suggests that both depolarizing and hyperpolarizing bipolar cells converge onto both ON and OFF ganglion cell types. The push-pull connectivity enables ganglion cells to remain sensitive to deviations about the mean output level of nonlinear photoreceptors. These and other properties of the push-pull model are discussed in the general context of retinal processing of spatiotemporal luminance patterns.

Adaptation, Physiological↗
PubMed2005

The motion aftereffect of transparent motion: two temporal channels account for perceived direction.

Adaptation to orthogonal transparent patterns drifting at the same speed produces a unidirectional motion aftereffect (MAE) whose direction is opposite the average adaptation direction. If the patterns move at different speeds, MAE direction can be predicted by an inverse vector average, using the observer's motion sensitivity to each individual pattern as vector magnitudes. These weights are well approximated by the duration of each pattern's MAE, as measured with static test patterns. However, previous efforts to use the inverse-vector-average rule with dynamic test patterns have failed. Generally, these studies have used spatially and temporally broadband test stimuli. Here, in order to gain insight into the possible contribution of temporal channels, we filtered our test pattern in the temporal domain to produce five ideal, octave-width pass-bands. MAE durations were measured for single-component stimuli drifting at various adaptation speeds and tested at a range of temporal frequencies. Then, two components with orthogonal directions and different speeds were combined and the direction of the resulting MAE was measured. The key findings are that: (i) for a given adaptation speed, the duration of a single component's MAE is dependent on test temporal frequency; (ii) the direction of MAEs produced by transparent motion (i.e., bivectorial adaptation) also varies strongly as a function test temporal frequency (by up to 90 degrees for some speed pairings); and (iii) the inverse-vector-average rule predicts the direction of the transparent MAE provided the MAE durations used to weight the vector combination were obtained from stimuli matched in adaptation speed and test temporal frequency. These results are discussed in terms of the number and shape of temporal channels in our visual system.

Adaptation, Physiological↗
PubMed2006

Adaptive norm-based coding of facial identity.

Identification of a face is facilitated by adapting to its computationally opposite identity, suggesting that the average face functions as a norm for coding identity [Leopold, D. A., O'Toole, A. J., Vetter, T., & Blanz, V. (2001). Prototype-referenced shape encoding revealed by high-level aftereffects. Nature Neuroscience, 4, 89-94; Leopold, D. A., Rhodes, G., Müller, K. -M., & Jeffery, L. (2005). The dynamics of visual adaptation to faces. Proceedings of the Royal Society of London, Series B, 272, 897-904]. Crucially, this interpretation requires that the aftereffect is selective for the opposite identity, but this has not been convincingly demonstrated. We demonstrate such selectivity, observing a larger aftereffect for opposite than non-opposite adapt-test pairs that are matched on perceptual contrast (dissimilarity). Component identities were also harder to detect in morphs of opposite than non-opposite face pairs. We propose an adaptive norm-based coding model of face identity.

Adaptation, Physiological↗