PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Differential Threshold”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1976

[The capacity to destinguish changes in the intensity as a function of volume and frequency (author's transl)].

Békésy audiometry equipment was used for investigations carried out in 15 test persons to study the intensity differentiation threshold. We tried to find the degree of intensity required to recognize given dB changes in the intensity. The results achieved very well coincide with those established by other authors. It was possible to statistically prove the volume dependence of the intensity differentiation threshold, it was, however, not possible to establish any frequency dependence. The relations of our result with the SISI test are under discussion.

Audiometry↗
PubMed1979

Evaluation of color discrimination in the white region.

Reference and test stimuli were produced on two separate color television screens to evaluate the color discrimination ability of the human eye for near-white colors. Each test stimulus had a luminance approximately equal to that of the reference, but was slightly different in chromaticity, e.g., [deltax] less than 0.01, [deltay] less than 0.01. The evaluation involved 20 persons observing 26 sets of color stimuli of 16-cd/m2 luminance, and 21 persons observing sets of color stimuli of 253 cd/m2. Observers were requested to categorize the color differences they perceived on a six-level rating scale. The results indicate that the differential thresholds for color difference of near-whites are between 4 and 8 CD (Color Difference), except in the bluish region.

Color Perception↗
PubMed1979

Spatial firing patterns of auditory neuron network modelling by computer simulation.

This communication examines, in digital computer simulated network, input signals and response patterns established at excitatory neurons' level i.e. the membrane potential of neuron soma. It is restricted to spatial patterns of the auditory neuron networks and time factor for nervous conduction and transmission is neglected compared with long maintained membrane potentials of neuron somas. The model analyzes the change in the spatial patterns of the membrane potential in the two dimensional networks of the auditory system. In order to evaluate the contribution of the various parameters, it is started that the simplest model has only one parameter, lateral inhibition. The other parameters are then added, one at a time, to successive models. The lateral inhibition is a necessary condition in the auditory nervous system if any sharpening of the response areas in the single neurons is to occur. A necessary condition for the validity of the model is that is should be applicable to the other senses such as vision and chemical patterns, taste. The threshold feature of auditory neurons aids in producing a sharpening in the neuron of the auditory relay nuclei. It does this clipping the spatial response patterns in one dimensional arrays of excitatory neurons. Recurrent inhibition seems a necessary condition in the sensory nervous system that any kinds of input signals are to be preserved over a wide range of stimulus intensity. In other words, this network has a wide dynamic range against any kinds of input signals. A simple self-recurrent negative feedback does not contribute to the sharpening, but more complex socalled averaged type does. A neuron network is capable of responding stably to stimuli with a wide range of intensity and with any kind of spatial patterns if there is a simple negative feedback mechanism. When there is no negative feedback, input signals soon disappear or saturate in the neuron network. Therefore, recurrent inhibition is the most important mechanism. Spontaneous activity appears to aid in the sharpening by providing a kind of contrast, that is by reducting the amount of activity in neurons adjacent to the excitatory area. Moreover, the effect of spontaneous activity in the model seems to make repples around the excitatory area and suggests that an introduction of activity at any stage of the networks, from whatever source for example reticulum formation and thalamus, might appreciably alter the response patterns at subsequent neuron network. This suggests that the mechanism of the consciousness that might be controlled by the thalamus and or reticular formation. These two dimensional neuron networks may be expanded to three dimensional neuron networks. The former might simulate the auditory nervous system while the latter might simulate the visual system.

Animals↗
PubMedDate not supplied

Psychoacoustic evaluation of present prostheses.

A battery of psychoacoustic tests, designed to specify auditory discriminations possible with present, single-channel auditory prostheses, was administered successfully to 12 of the 13 subjects. While no subject was able to perform all discriminations required by this battery of tests, there was no discrimination that at least one subject did not perform successfully. The typical subject could 1) discriminate intensity differences within normal limits for frequencies below 1000 Hz; 2) discriminate frequency differences quite normally at 125 and 250 Hz, but not at all at 1000 or 2000 Hz; 3) discriminate differences in signal duration, temporal patterning (rhythm), and spectrum (e.g., tone vs narrow-band noise); and 4) discriminate between pairs of synthesized vowel-like sounds. The results of masking experiments could only be interpreted in terms of intensity discrimination. Several subjects were able to relate stimulus intensity to loudness for low-frequency sounds; and they could relate stimulus frequency to pitch for signals below 25 Hz. The intelligibility of the subjects' speech was found to improve when their prostheses were activated.

Auditory Threshold↗
PubMed1979

Effect of information feedback on temporal discrimination in concurrent and post-feedback measures.

College students estimated time intervals (5, 6, 7, 8, and 9 sec.) where one group (N = 20) received information feedback in terms of actual interval durations and a second group (N = 18) received no information. Theshold measures were then taken for all subjects using the method of constant stimuli (comparison stimuli of 5, 6, 7, 8, and 9 sec. and a 7-sec. standard). In addition to increased accuracy and consistency of judgments, the feedback group showed a decreasing Weber fraction during the estimation phase, while the Weber fraction for the no-feedback group increased. The feedback group retained only a slight advantage in subsequent threshold measures; group differences in difference thresholds and derived nonparametric estimates of d' were nonsignificant.

Differential Threshold↗
PubMed1979

Comparison of contrast thresholds of large bars and checks measured by VECPs and psychophysically as a function of defocusing.

The effects of defocusing the image on the contrast threshold were studied both for checkerboard and bar patterns at various low spatial frequencies, and comparison was made between psychophysical results and visually evoked cortical potentials (VECPs) results. VECP threshold was defined as the contrast necessary for obtaining a criterion amplitude of 5 muV. When increasing the degree of defocusing, the lowest contrast threshold shifted towards larger checks or bars, the contrast threshold increased more abruptly for smaller sizes, and the VECP contrast thresholds increased more than the psychophysical ones, especially for smaller sizes. No significant difference was found in the contrast thresholds between the results with bar patterns and checkerboard patterns, except that for bars, the VECP threshold as defined was approx. 0.2 log units higher than those for checkerboard.

Differential Threshold↗
PubMed1979

The effects of stimulation of ear acupuncture points on the body's pain threshold.

Six ear acupuncture points, one non-acupuncture ear point, and the body locus Ho-Ku (LI-4) were electrically stimulated in order to compare the effects of stimulation on the body's pain threshold at selected loci on various points on the body by measurement with a radiation heat-type Pain Meter on 5 subjects. The ear points, with the exception of the non-acupuncture ear point, were found to be effective even in peripheral body regions in varying degrees. Ear stimulation did not increase the threshold as rapidly as Ho-Ku. In all cases where the pain threshold was raised, the effect persisted after electrical stimulation had stopped.

Acupuncture Therapy↗
PubMed1979

Interaction effects of extraversion and neuroticism on detection thresholds.

Detection thresholds for electrocutaneous stimulation were measured in young male subjects by two different methods - a method of limits and a forced-choice method - the latter assumed to be less influenced by decision processes. Relations between the threshold measures and scores in the EPI extraversion (E) and neuroticism (N) scales were studied. High N-low E ("unstable introvert") subjects had the lowest thresholds. The result is in line with the predictions made on the basis of Eysenck's personality theory.

Adult↗
PubMed1977

Factors of the langugage of pain in patient and volunteer groups.

An empirical determination of the nature and minimum number of dimension necessary to describe responses to the McGill Pain Questionnaire, and a comparison of groups, experiencing clinical or experimentally induced pain, on the dimensions were carried out. Eighty-five patients referred to a low back pain diagnostic clinic and groups of 129 volunteer students exposed to electric shock to pain threshold and pain tolerance levels described their pain using the McGill Pain Questionnaire's descriptive words. An incomplete principle component factor analysis of subjects' ratings suggested that 5 factors should be retained. These factors were judged to reflect: (I) immediated anxiety, (II) perception of harm, (III) somesthetic pressure, (IV) cutaneous sensitivity, and (V) sensory information. Canonical Analysis of Variance and univariate comparisons of back pain, threshold, and tolerance groups on these dimensions were conducted and implications for clinical and laboratory research discussed.

Adult↗
PubMed1979

Analysis of "integrate-to-threshold" neural coding schemes.

Methods of analysis for some deterministic and stochastic variants of the integrate-to-threshold neural coding scheme are presented. Adaptation phenomena are modeled by means of feedforward and feedback adaptive threshold control. Simulations of sinusoidal and step responses reproduce satisfactorily the qualitative characteristics of adaptation as compared with physiological data. It is postulated that such adaptive threshold control may be accomplished by the release, or conformation change, of molecules involved in the control of excitable-channel dynamics.

Action Potentials↗