Hyperacuity tasks have been suggested for the assessment of potential visual function in the presence of cataracts. To test this suggestion, hyperacuity thresholds for an oscillating bar were measured in 30 subjects with idiopathic cataract and in 24 age-matched normals over a range of oscillation frequencies. Each subject's cataract was ...

In this study, the cross-correlation function was applied in the evaluation of MLR thresholds in the low and middle frequencies. The parameters of the cross-correlation function consist of the correlation coefficient at a lag-time of zero (RO), the maximum correlation coefficient (RM), and the latency delay on the lag-time axis ...

Increment thresholds were determined for bichromatic mixtures of 660 and 520 nm (red + green), and 440 or 460 and 570 nm (blue + yellow). These measurements were made against a 1000-td white background that was surrounded by a larger, luminance matched annulus that appeared steady or flickered at 10 ...

We investigated the effects of contrast and temporal frequency on vernier edge alignment thresholds. Edges were defined by the presence of a 180 deg phase difference in the temporal modulation waveform of adjacent rectangles with spatially uniform luminances. Thresholds of 10 arc sec or less could be obtained at high ...

A prototype automated flicker perimeter was used to investigate flicker luminance thresholds in glaucoma patients (n = 11), ocular hypertensives (high risk n = 10, low and intermediate risk n = 21) and normal controls (n = 10). Differential light sensitivity was measured for one eye of each subject using ...

We have estimated the absolute threshold of congenic albino and pigmented mice (C57) using ERG, pupillary light reflex, and VEP. We are unable to detect strain differences using ERGs or VEPs, but pupillary thresholds appear to be different. In addition, as we have previously reported for rats, VEP thresholds are ...

Research assessed the independent contribution of the trigeminal and olfactory nerves to the detection of airborne chemicals by measuring nasal detection thresholds in subjects clinically diagnosed as lacking a functional sense of smell (anosmics) and in matched normal controls (normosmics). Anosmics can provide only odor-unbiased pungency thresholds. Normosmics provided odor ...

Nerve conduction studies and measurements of thermal thresholds (hot and cold) were performed in 25 healthy control subjects and 24 patients with carpal tunnel syndrome: first, to compare the extent of abnormality demonstrable in the function of large and small afferent axons; second, to correlate these abnormalities with clinical severity; ...

Stereoacuity thresholds improve considerably with practice when measured using three vertical lines 15' apart horizontally and presented briefly. For experienced observers, these thresholds are relatively independent of exposure time for stimulus durations smaller than 100 msec. The thresholds are 2-3 times larger when the outer flanking lines are shown continuously ...

Twenty-four healthy human subjects provided thresholds for their perception of pressure, sharpness, and pain. Mechanical forces were applied to the dorsal surface of the digits with flat-tipped probes of various sizes. Thresholds (expressed as force) increased with increasing probe size, as previously described. There was no evidence of a laterality ...

High-pass resolution perimetry is a new technique that uses a vanishing optotype as the test stimulus. This type of stimulus is thought to produce steeper frequency-of-seeing curves than the stimulus used in conventional automated perimetry, resulting in a lower variability in threshold estimates. The purpose of this study was to ...

1. Benzodiazepines (BZDs) impair sensitivity to temporally modulated visual stimuli (flicker). Critical flicker-fusion frequency (CFF) is commonly used as a measure of this effect, but it only measures sensitivity to a narrow range of frequencies, usually above 25 Hz. Are other frequencies more sensitive to the effects of BZDs? 2. ...

We recently found that vibratory detection threshold is greatly influenced by the algorithm of testing. Here, we study the influence of stimulus characteristics and algorithm of testing and estimating threshold on cool (CDT), warm (WDT), and heat-pain (HPDT) detection thresholds. We show that continuously decreasing (for CDT) or increasing (for ...

Three adult female chickens were trained to detect pure tones using a positive reinforcement paradigm. A modified perometer estimation-through sequential testing (PEST) threshold determination procedure was used to measure the audiogram between 250 and 5500 Hz, at 0.1-octave steps over most of the range. For the mean audiogram, threshold increased ...

Previous investigators have elicited spectral sensitivity functions for the chromatic and achromatic systems by manipulating the stimulus spatiotemporal parameters. An alternative strategy for obtaining these two functions is to use a single set of stimulus parameters and vary the threshold criterion. This can be accomplished by determining colour and flicker ...

Critical fusion frequencies have been evaluated in heterochromatic red-green flicker as a function of red-green luminous modulation defined by mL = (R-G)/(R+G)%, at five different mean luminance levels, two test sizes (2 degrees and 5 degrees) and square wave stimuli. The extreme values mL = +/- 100 correspond to ordinary ...

PURPOSE: The authors used a method of spatial scaling to quantify the eccentricity-related decline in differential light sensitivity as a function of visual field meridian and age. METHODS: Differential light threshold at the fovea was measured in two groups of subjects of differing age (young mean age, 23.6 yr; standard ...

OBJECTIVE: To evaluate a commercially available means of baseline-related suprathreshold examination designed to detect visual field worsening. DESIGN: Patients for whom results of a baseline series of static-threshold visual field examinations were available underwent both a second static-threshold examination (full-threshold strategy; average time, 15 minutes) and a baseline-related suprathreshold examination ...

Thresholds for discriminating the changes in the spectral shape of simultaneously presented components (profile analysis) are measured as a function of stimulus duration for various complex stimuli. For all stimuli, the threshold decreases with increasing duration until a transition time is reached, and thereafter the threshold remains constant. The amount ...

Detection thresholds to step indentations applied to touch domes were measured and compared with threshold values obtained on adjacent areas of hairy skin. The mean of the detection thresholds determined on touch domes for five subjects was 504 +/- 27 microns (SEM). The detection thresholds found off the touch domes ...

Absolute thresholds were measured psychophysically (behaviorally) and physiologically in the same subjects. Psychophysical thresholds were obtained using a modified method of limits. Physiological thresholds were based on auditory steady-state potentials recorded from the scalp. The stimuli for both types of test were click trains, periodic tone bursts and amplitude-modulated tones. ...

A computerized statistical analysis of 1,100 quadripolar electrode combinations used in epidural spinal cord stimulation therapy for the management of pain was carried out to investigate perception and tolerance thresholds. This analysis showed that the thresholds are higher at high-cervical, mid-cervical, mid-thoracic and low-thoracic spinal levels. It is also higher ...

Changes in action potentials (APs) of human soleus motor units (MUs), that occur during ischaemia produced by thigh compression, were studied in five experiments on one subject. In each experiment, a well-isolated AP of a low threshold MU was recorded by a needle electrode beginning with ischaemia onset up to ...

Contrast detection thresholds for horizontally and vertically oriented elliptical stimuli with a 2D-Gaussian luminance profile in space and a Gaussian envelope in time were measured as a function of their spatial scale parameters for two different presentation times. For slowly varying stimuli, threshold is independent of stimulus size whenever the ...

Critical flicker frequency (CFF) is the frequency at which a flickering light appears steady. It is a sensitive measure for assessing recovery from anaesthesia. The CFF is almost always determined with the method of limits by which the flickering frequency is progressively decreased (or increased) until the patient reports a ...

Benefits of high-frequency audiometry in monitoring hearing sensitivity of patients administered ototoxic medications are well established. High-frequency thresholds have been reported to be variable, due in part to small differences in the placement of the earphone diaphragm over the opening of the ear canal. Reliability may be improved by using ...

We compared within-subjects electrical thresholds and dynamic ranges obtained with direct round-window and transtympanic promontory stimulation carried out preoperatively in 12 patients who were candidates for a cochlear implant. Square waves with frequencies of 50, 100, 200, and 400 Hz were delivered in a 50% duty cycle to both sites ...

Several recent studies have reported large intersubject variability of high-frequency thresholds measured with circumaural earphones. In the present study, high-frequency thresholds of 10 subjects were measured with circumaural (Sennheiser HD-250) and insert (Etymotic ER-1) earphones at 10, 12, 14, and 16 kHz. Overall results show significantly smaller variability of the ...

Experiments are described in which the steady-state accommodation response versus stimulus curve was measured with an infrared autorefractor for high-contrast stimuli having a 100% square-wave temporal modulation of luminance in the frequency band 1-200 Hz. Slightly more accurate responses were found at frequencies approximately 50-100 Hz, i.e. above flicker fusion. ...

1. Adult owl monkeys were trained to detect a difference in the frequency of sequentially applied tactile stimuli presented to a constant, restricted location on the glabrous skin of a single finger. Psychophysical performance functions and thresholds were determined on daily sessions over a 3- to 20-wk-long training period. 2. ...

The thresholds of the generation of EP in the L field of two to nine day old pied flycatcher nestlings in response to monotonal bursts of varied frequency were investigated. The entire range of auditory sensitivity was divided into three channels on the basis of the character of the age-related ...

In perimetry, threshold is defined as the stimulus intensity at which the frequency of perception is 50%. Around the threshold, there is a transition zone in which the frequency of perception turns from 0% to 100%. We examined the frequency-of-seeing-function in 21 persons with and without pathological damage at various ...

Differential light sensitivity and high-pass resolution thresholds were studied before and after pan-retinal photocoagulation in subjects with proliferative diabetic retinopathy. The photocoagulated retinal area was measured and the relative change in ganglion cell separation was estimated. The change in differential light thresholds after treatment, when expressed in decibels, appeared to ...

Measurement of cutaneous vibrotactile thresholds may be useful for assessment of the functional integrity of the somatosensory system. To validate a rapid method of determining vibrotactile thresholds that uses a commercially available electromechanical device, vibrotactile thresholds were compared with standardized physical examination findings of sensory function and electrophysiological parameters in ...

To evaluate the physiological thresholds of neuromuscular stimulation relevant to very fast NMR imaging studies that use gradient switching at frequencies of 1-2 kHz and a maximum magnetic field of up to 10 mT, a series of studies were done with human volunteers using an experimental echo planar gradient coil ...

We investigate the performance of the binary joint transform correlator (JTC) in the presence of multiple objects for two types of thresholding that are used to binarize the joint power spectrum. The first method uses the median of the joint power spectrum of the reference image and the input scene ...

The scotopic threshold response (STR) is a negative potential to low intensity light recorded from the dark-adapted retina. It reflects inner retinal function. The STR is now recorded routinely as part of our electroretinography protocol. The projected absolute threshold calculated from the amplitude versus intensity function for the STR has ...

Under most conditions, increasing the intensity of a flickering light makes the flicker more conspicuous. For a light flickering at 15 times per second, however, increasing the intensity can cause the flicker to disappear before reappearing again at higher intensities [Vision Res. 29, 1539 (1989)]. This flicker disappearance or null ...

Detection thresholds for 1000-Hz, 16-ms tone bursts were estimated for 3- and 6-month-old infants and for young adults. The test procedure used was the observer-based psychoacoustic procedure. Thresholds were estimated using two different adaptive procedures and the method of constant stimuli. There was little difference among the average thresholds determined ...

Perception thresholds for warm and cold sensation were measured by two methods, the method of levels and the method of limits, at various rates of temperature change. The following findings were obtained. (1) The threshold value is critically dependent upon the method through which it is obtained, being higher for ...

In studies of subliminal perception, a threshold for awareness is usually estimated for each S (e.g., the stimulus duration that yields chance discrimination performance). This article shows that if the S's true threshold varies randomly from trial to trial, estimation of a fixed threshold has important consequences. Specifically, the estimated ...

Ocular hypopigmentation is associated with neurological defects in structure and function. This paper investigates the absolute visual thresholds in dark-adapted hypopigmented animals compared to their normally pigmented controls. Here we asked (1) whether the threshold elevation found in hypopigmented animals is a general consequence of the reduction in melanin content; ...

Flicker sensitivities were measured for more than 100 people age 60 and older with stimulus-conditions originally designed to obtain estimates of preretinal absorption by the lens and macular pigment. Flicker sensitivities were measured on two chromatic backgrounds: a 1000-td, 480-nm background and a 5800-td, Wratten 33 background (approximately metameric with ...

Thirty-two Ss between 22 and 59 years of age yielded detection thresholds for 4 odorants over 4 sessions. The thresholds decreased and reliability increased over the course of testing. High intercorrelations between odorants and the stability of an S's relative position within the threshold distributions showed that a general factor ...

We investigate the performance of the binary joint transform correlator (JTC) for three types of thresholding used to binarize the joint power spectrum. The first thresholding method uses the median of the joint power spectrum of the reference image, which is independent of the effect of input scene noise. The ...

Although we and others have employed a thresholding strategy to extract "peak" values from positron emission tomographic (PET) regions of interest (ROIs), the effects of peak picking on fitted fluorodeoxyglucose rate constants, regional metabolic rate for glucose (rCMRglc) profiles, patterns of regional metabolic covariation, and PET-neurobehavioral correlations have not been ...

The visual threshold for standard and flickering targets was determined and compared in 8 glaucoma patients, 8 glaucoma suspects and 13 normal controls. Using a Goldmann size III standard white light target, 25 points in the central 30 degrees of the visual field were tested. The location of these points ...

We study the influence of a variable neuronal threshold on fixed points and convergence rates of an associative neural network in the presence of noise. We allow a random distribution in the activity levels of the patterns stored, and a modification to the standard Hebbian learning rule is proposed for ...

1. The spatial distribution and physiological properties of the tactile hairs and their sensory afferents of the hindlegs of the locust Schistocerca gregaria are described. Hairs occur in a consistent position from animal to animal. Hairs on the dorsal tibia are of a greater mean length, 403.1 +/- 17.9 microns, ...

The CF thresholds of three different spontaneous firing rate categories of single auditory nerve fibres were measured in guinea pigs with widely differing cochlear sensitivities. The CF thresholds for all fibres were compared to the CAP thresholds at the same frequencies. The relationship between single fibre CF threshold and CAP ...