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At least 163 records · Page 9Linked to original sources
PubMed2006

Two psychophysical channels of whisker deflection in rats align with two neuronal classes of primary afferents.

The rat whisker system has evolved into in an excellent model system for sensory processing from the periphery to cortical stages. However, to elucidate how sensory processing finally relates to percepts, methods to assess psychophysical performance pertaining to precise stimulus kinematics are needed. Here, we present a head-fixed, behaving rat preparation that allowed us to measure detectability of a single whisker deflection as a function of amplitude and peak velocity. We found that velocity thresholds for detection of small-amplitude stimuli (<3 degrees) were considerably higher than for detection of large-amplitude stimuli (>3 degrees). This finding suggests the existence of two psychophysical channels mediating detection of whisker deflection: one channel exhibiting high amplitude and low velocity thresholds (W1), and the other channel exhibiting high velocity and low amplitude thresholds (W2). The correspondence of W1 to slowly adapting (SA) and W2 to rapidly adapting (RA) neuronal classes in the trigeminal ganglion was revealed in acute neurophysiological experiments. Neurometric plots of SA and RA cells were closely aligned to psychophysical performance in the corresponding W1 and W2 parameter ranges. Interestingly, neurometric data of SA cells fit the behavior best if it was based on a short time window integrating action potentials during the initial phasic response, in contrast to integrating across the tonic portion of the response. This suggests that detection performance in both channels is based on the assessment of very few spikes in their corresponding groups of primary afferents.

Afferent Pathways↗
PubMed1991

A new measure for determining the degree of abnormality of psychophysical tuning curves in hearing-impaired subjects.

Psychophysical tuning curves were determined in hearing-impaired and normal-hearing subjects. Frequency selectivity, determined from the tuning curves of the hearing-impaired, decreased with increasing hearing impairment. As this may be attributed to the subjects' hearing impairment as well as to the inevitably higher test (probe)-tone level, we also collected psychophysical tuning curves from normal-hearing subjects as a function of test-tone level. Their frequency selectivity also decreased with test-tone level, but to a lesser degree. This indicates a real decrease in frequency selectivity in hearing-impaired subjects. Two measures were used to describe frequency selectivity, the d1oct and the newly introduced AALD. The latter is the average absolute difference in masker levels between the individual's psychophysical tuning curve and the average normal tuning curve, obtained at the same test-tone level. The AALD turned out to be a more sensitive tool for measuring pathological frequency selectivity than the d1oct.

Adolescent↗
PubMed2002

[Assessment of hearing in children with infantile cerebral palsy. Comparison of psychophysical and electrophysical examination].

Assessment of hearing in children with various types of cerebral palsy was the aim of the study. The audiologic and laryngologic examinations were performed in 32 children with cerebral palsy. Audiologic examinations encompass impedance audiometry, otoacoustic emissions (DPOAE), brainstem evoked audiometry (ABR) and also psychophysical studies depending on possibility of co-operation with children--tonal and speech audiometry. On the ground of psychophysical studies hypacusis was recognised in 37.5% of children. In 25% of cases tonal audiometry could not be done because of mental status of the child. Hypacusis was most common in extrapyramidal type of cerebral palsy. Abnormal morphology of ABR was observed in 71.9% of cases, in 18.7% of them it could be explained by the threshold of hearing. There was always lack of stapedial reflex in cases with abnormal morphology of ABR. In some cases auditory neuropathy could be recognised on the basis of audiological examinations. In many cases the discrepancies between psychophysical and objective methods of investigation were observed. Results of hearing examinations in children with cerebral palsy should be evaluated very carefully on the basis of cross checking principle because of observed inconsistencies in audiometric tests.

Adolescent↗
PubMed2003

[Psychophysical and electrophysiological tests in diagnosis of the early sign of glaucomatous optic neuropathy].

Visual field losses and changes of the optic nerve disk are signs of optic neuropathy in glaucoma; psychophysical and electrophysiological tests can contribute to an early detection of glaucomatous optic neuropathy. Electrophysiological methods, like pattern electroretinogram (PERG) and visual induced cortical potentials can be useful in the diagnosis of glaucoma since they are compatible with the functions of retinal ganglion cells. A combination of psychophysical and electrophysiological examination methods contribute to an early diagnosis of glaucoma because they make it possible to study different aspects of visual functions. The results of psychophysical tests correlate to a greater extent than electrophysiological tests with defects in visual fields. Temporal, temporal-and-spatial contrast sensitivity and visual induced cortical potentials, whose changes are detected in the "preperimetric" stage of glaucoma, are the most sensitive parameters, while PERG changes later. Both the color contrast and light PERGs reduce in glaucoma. However, a significant correlation was detected only between the reduction of the color contrast PERG and visual field defects. A reduced sensitivity of dark and color channels of the retinal cone systems was also registered. Defects of color sensitivity are more pronounced and they precede the onset of light sensitivity changes. Defects of color and contrast sensitivity are an early sign of the progressing of optic neuropathy in glaucoma.

Contrast Sensitivity↗
PubMed2005

[Comparing the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear].

OBJECTIVE: The purpose of this study is to compare the characteristics of psychophysical tests between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear and to analyse the characteristics of psychophysical and impedance tests for cochlear implant patients with large vestibular aqueduct syndrome. METHOD: One hundred and thirty-one cochlear implant pre-lingual deafness patients participated in this study. They received cochlear implant surgery at the age of 1.5 to 12 years old from Nov, 1998 to Aug, 2003. The patients were divided into two groups. Group A had 111 patients with normal inner ear. Group B had 20 patients with radiographically proven large vestibular aqueduct syndrome. All of the patients were inserted with Nucleus 24M. The time of the first programming session was approximately 4 weeks after surgery. The psychophysical tests included T and C-Level tests. The programming techniques used in the test were suitable for the age of the patients. The R116 and R126 software were used to test the impedance of the electrodes automatically. RESULT: Using the independent-samples t-test, the impedance and T/C-Level of each electrode did not differ significantly between group A and B ( P > 0.05). The impedance and T/C-Level were not significantly different between group A and B at the time of switch-on, 1 week, 2 weeks, 3 weeks, 2 months, 3 months, 6 months, 9 months and 1 year after switch-on (P > 0.05). CONCLUSION: The parameters of mapping were not significantly different between cochlear implant children with large vestibular aqueduct syndrome and normal inner ear. The management and procedure of mapping used in cochlear implant children with normal inner ear can be used in the children with large vestibular aqueduct syndrome.

Case-Control Studies↗
PubMed1991

Psychophysical power functions of exercise limiting symptoms in coronary heart disease.

Thirty consecutive male patients with angiographically determined multivessel disease and ten healthy volunteers were subjected to a symptom limited exercise test with stepwise increments of 10 W every minute. Leg exertion, breathlessness, and chest pain were rated according to a category-ratio scale with 10 degrees and psychophysical power functions computed. Depending on whether chest pain was the limiting symptom, patients were subdivided into groups A (N = 20) and B (N = 10). Exercise capacity did not differ between groups A and B. Both groups terminated the exercise test at lower work loads and lower symptom intensities than the healthy volunteers. Psychophysical power functions were similar for leg exertion in the three groups while the growth of breathlessness was lower in group B. In group A the intensity of chest pain increased more rapidly than leg exertion or breathlessness. In conclusion, those patients with coronary heart disease interrupt the exercise test at lower ratings of leg exertion and breathlessness than healthy volunteers. The psychophysical power functions do not grow more rapidly for these sensory modalities in patients than in healthy volunteers.

Anxiety↗
PubMed1984

Effect of psychophysical backward masking on human brain-stem responses (ABR).

A backward-masking (BWM) paradigm was used to obtain measurements on 4 normal young adults of psychophysical BWM and of the analogous electrophysiological masking from human auditory brain-stem responses. The same stimuli and Ss were used in both experiments. Psychophysical BWM was determined to a 100-musec click masked by a 100-msec white noise after time delays of 1, 5, 10, 25, and 100 msec and at noise masker levels of 50, 65, and 80 db SPL. As previously demonstrated, more psychophysical BWM occurs at short delta ts (1 to 10 msec) than at longer delays and masked thresholds are greater as masker level increases. In the electrophysiological experiment, using delta ts = 1, 5, and 10 msec, the extent to which wave V latency was affected by the following masker was determined for various experimental conditions. Wave V latency increased with a decrease in delta t, for maskers above probe level, except that latency was not significantly affected by any masker level at delta t = 10 msec.

Acoustic Stimulation↗
PubMed1977

Mixtures of substances with similar tastes. A test of a psychophysical model of taste mixture interactions.

When substances of similar taste are mixed, the mixture can show suppression or synergism. That is, the perceived intensity of the mixture can be less than or greater than the sum of the perceived intensities of the components. In the present study, these departures from simple additivity could be predicted from the psychophysical functions relating tast intensity to stimulus concentration of the unmixed components. Psychophysical functions are said to show compression when successive increments in concentration produce progessively smaller increments in perceived intensity and to show expansion when successive increments in concentration produce progressively larger increments in perceived intensity. Suppression resulted from mixtures of substances with compressed psychophysical functions, and synergism resulted from mixtures of substances with expanded functions.

Adult↗
PubMed1994

The psychophysical power law and unilateral spatial neglect.

The relationship between objective measures and subjective experiences of sensory stimuli is described by a power law, psi = K phi beta, in which psi represents the psychological value and phi the physical value. The constant (K) and the exponent (beta) are empirically derived. This relationship is often assumed to correspond to properties of peripheral receptor sensory transduction. Patients with left-sided spatial neglect tend to bisect lines to the right of the objective midline. Line bisection bias was used as the dependent variable in how a patient with neglect and five normal subjects bisected lines of varying lengths. Analyzing these data as a power function accounted for over 99% of the variance in five different experimental conditions. The normal exponent matched the value expected from traditional psychophysical experiments of line length estimation, whereas the patient's exponent was diminished. The patient's data provide evidence for central nervous system participation in computations underlying psychophysical relationships. The notion that attentional and perceptual processes are closely linked was supported by the influence of attentional cuing on the power functions obtained in normal subjects. The descriptive precision of the power function uncovered qualitative variability in how normal subjects allocate attention across different spatial reference frames and demonstrated that this patient had a quantitative defect in directing attention across an allosteric reference frame, but a qualitative defect in directing attention across a viewer/environment reference frame.

Aged↗
PubMed1988

Discrimination strategies in animal psychophysics and their role in understanding sensory receptor function.

Discrimination is defined in a restricted sense here as a precise and specifiable relation between stimuli and responses. Experimenter control of stimulation is one significant feature of this relation. It is suggested that there may be some important differences between discrimination of drugs and exteroceptive stimulation. However, a discussion of current strategies in animal psychophysics might uncover similarities between these two discrimination formats useful in formulating questions and designing future research. Traditionally animal psychophysics has focused on basic questions of acuity and sensitivity (threshold). Beyond their obvious value in the study of comparative sensory function and evolutionary development, these experiments have provided particularly important new insights into the understanding of peripheral sensory transduction and processing and their relation to perception. Our experiments have been carried out in animals whose hearing has been impaired by drugs and cryolesions, and relations have been sought between the subsequent hearing loss and the histopathological changes occurring in the auditory receptor cells of the inner ear. But threshold sensitivity is only one of many perceptual dimensions and tells us nothing of the discriminations that are made among stimuli which are clearly above minimum detectable levels. For example, discriminations occur along stimulus dimensions such as wavelength of light, sound pressure, acoustic frequency, and so on. Sensory systems also permit the accurate location of the source of stimulation at a distance, the selection of certain frequencies or wavelengths and the rejection of others, and finally the discrimination among very complex but biologically useful signals such as speech. Prototypical experiments are described; the results suggest significant and orderly relations with peripheral sensory processing mechanisms. The power of operant behavior to examine perception from a variety of perspectives is discussed.

Animals↗
PubMed1976

Human psychophysical analysis of receptive field-like properties: V. Adaptation of stationary and moving windmill target characteristics to clinical populations.

This paper describes the application of several key parameters of a windmill-shaped target (used in determinations of the psychophysical transient-like function) to clinical populations as a diagnostic tool for static perimetry. A technique for independently analyzing sustained- (Westheimer function) and transient-like retinally-based psychophysical responses is outlined, and stimulus characteristics, reliability and diagnostic potential of the tests are examined. Several particularly interesting clinical cases (one closure of a branch retinal arteriole) and two senile macular degeneration patients) are presented for illustrative purposes. In addition, a tentative 'working hypothesis' is presented as a basis for extensive future analysis of various clinical populations.

Aged↗
PubMed1991

Spatial frequency of the human short-wavelength-sensitive (blue) cone mechanism. Psychophysical studies and pattern-reversal visual evoked potentials.

The interactions of spatial and chromatic processing of the short-wavelength-sensitive cone mechanism were studied in humans with patterned (checkerboard) stimuli of various spatial frequency (10, 22, 44, and 85 min of are respectively), under steady exposure to yellow light (575 nm, 390 cd/m2). Psychophysical studies and pattern-reversal visual evoked potentials were employed. Parameters of the transient pattern-reversal visual evoked potentials (pattern reversal rate of 2.4 s-1) especially observed were the latencies of P2 (P100) and N3 and the amplitude of P2-N3. It was only with the largest applicable check size (85 min of arc) that both the psychophysical studies and visual evoked potentials could succeed in satisfactorily isolating the short-wavelength-sensitive cone mechanism. Pattern-reversal visual evoked potential latencies are recommended in the evaluation of this cone mechanism because of their smaller variance and higher selectivity in isolating the short-wavelength-sensitive cone mechanism than the amplitude. The peak sensitivity of this cone mechanism was shown to be about 449 nm at the corneal level. The short-wavelength sensitive cone mechanism represented the characteristics of low spatial resolution and long latencies of the pattern-reversal visual evoked potentials.

Adult↗
PubMed1996

A biologically plausible model of early visual motion processing. II: psychophysical application.

We test the model of early visual processing introduced in the companion paper by simulating a range of psychophysical phenomena. We present new data concerning our ability to discriminate the speed of drifting gratings when spatiotemporally apertured in a variety of ways. We shall investigate the role played by the aperture in modifying the grating's behaviour from its idealisation as a pure Fourier component and show that this is not negligible. Other phenomena which we simulate and explain relate to the way perceived velocity is influenced by contrast and spatial frequency. Many of our explanations are couched in terms of the relative number of cells occurring within each locale of the Fourier domain. This use of the cell density map is a unifying concept and avoids the necessity for a range of separate mechanisms. We argue that a neurophysiologically detailed model is necessary in order to explain psychophysical data (Weber fractions) which vary over less than an order of magnitude, and small deviations from veridical encoding of velocity.

Artifacts↗
PubMed1993

Cyclovergence: a comparison of objective and psychophysical measurements.

Several psychophysical procedures have been used to measure cyclovergence but none has been adequately validated with respect to an objective measure. Scleral search coils were used to measure cyclovergence induced by dichoptic textured patterns which cyclorotated in antiphase through 6 degrees at frequencies between 0.05 and 2 Hz. In one psychophysical procedure subjects nulled the apparent oscillatory motion of radial nonius lines superimposed on a small black disc at the center of a large cyclorotating display. In the second, subjects nulled the apparent inclination in depth of a vertical line displayed in the same way. The amplitude of cyclovergence measured objectively and the magnitude of oscillation of the nonius lines were similar at low stimulus frequencies. At higher frequencies of cyclorotation, both amplitudes declined but the nonius amplitude exceeded that of cyclovergence. The apparent inclination of the vertical test line, as indicated by the nulling procedure, also declined with increasing frequency of cyclorotation, but not at the same rate. At low frequencies, the apparent inclination of the test line was greater than that corresponding to the cyclodisparity induced into the line and almost as great as that corresponding to the relative disparity between the oscillating pattern and the line. The implications of these results for measuring cyclovergence and for an understanding of stimuli driving cyclovergence and perceived inclination in depth are discussed.

Eye Movements↗
PubMed1994

Electrophysiological and psychophysical quantification of temporal summation in the human nociceptive system.

Animal experiments have shown that the nociceptive reflex can be used as an indicator of central temporal integration in the nociceptive system. The aim of the present study on humans was to investigate whether the nociceptive reflex, evoked by repetitive strong electrical sural nerve stimuli, increased when summation was reported by the volunteers. The reflexes were recorded from the biceps femoris and rectus femoris muscles in eight volunteers following a series of stimulations at 0.1, 1, 2, and 3 Hz. Each series consisted of five consecutive stimuli. Using 0.1- and 1-Hz stimulation, the reflex was not facilitated in the course of the five consecutive stimuli. Following 2- and 3-Hz stimulation, the reflex size (root mean square amplitude) increased significantly during the course of the fifth stimulus. This reflex facilitation was followed by a significant increase (summation) in the pain magnitude when compared with 1- and 0.1-Hz stimulation. Furthermore, the threshold for psychophysical summation could be determined. This threshold (stimulus intensity) decreased when the stimulus frequency (1-5 Hz) of the five consecutive stimuli was increased. The nociceptive reflex and the psychophysical summation threshold might be used to clarify and quantify aspects of temporal summation within the human nociceptive system.

Adult↗
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↗
PubMed1993

Stargardt's disease/fundus flavimaculatus: psychophysical and electrophysiologic results.

Retinal functions were analyzed psychophysically and electrophysiologically in 73 patients (146 eyes) with Stargardt's disease/fundus flavimaculatus. Patients were classified into types 1, 2, 3, and 4; patients with type 3 were subdivided into 3E and 3L (early and late onset of initial symptoms). Most had visual acuity (VA) of 20/200 or greater at initial testing. VA declined 0.25 octave/year during follow-up (mean, 6.1 years). Four of 16 patients (25%) older than 40 years had VA of 20/200 or less in the stronger eye. Psychophysical tests (flicker profile, central scotoma, dark adaptation) showed variable degrees of abnormalities. Electrophysiological tests showed significant photopic b-wave amplitude decreases, particularly in type 3E (42.2% of normal). The electro-oculogram light peak/dark trough ratio was abnormal in 60 of 132 eyes (45.5%), especially in type 3E (25 of 34 eyes, 73.5%). Visual prognosis and overall visual function varied depending upon disease type, location of retinal lesions, and age of onset. In Type 3E, overall retinal function was poorest and accompanied by the most severe decline of central vision and function in the surrounding macula.

Adolescent↗
PubMed1996

J. Plateau: on the measurement of physical sensations and on the law which links the intensity of these sensations to the intensity of the source. J. Plateau: report on 'Psychophysical study: theoretical and experimental research on the measurement of sensations, particularly sensations of light and of fatigue' by Mr. Delboeuf. 1872.

Two papers published in 1872 by the Belgian physicist Plateau are here translated into English. The first paper contains the earliest published suggestion that the relation between physical stimulus magnitude and the strength of the internal sensation evoked is a power law and has been much cited for this reason. It also describes the earliest experiment to be performed, though not the first to be reported, on the subject of the psychophysical law. The performance of that experiment antedated Fechner's Elemente der Psychophysik by about 20 years. The second paper summarises a memoir in which a colleague, Delboeuf, reports his more extensive experiments on the subject and commends that memoir to the Belgian Royal Academy. In this second paper Plateau concludes that he was mistaken in supposing the psychophysical law to be a power relation.

Habituation, Psychophysiologic↗