Biomedical subjects

S J Bolanowski

Publications and source records attributed to S J Bolanowski.

9 recordsLinked to original sources

PubMed1992

Effects of stimulus duration on the response properties of Pacinian corpuscles: implications for the neural code.

Based on physiological and psychophysical data, it has been suggested that the neural code for threshold detection in the P channel, mediated by Pacinian corpuscles (PCs), may be 2-4 neural impulses/stimulus (Bolanowski et al., 1988). To further test the efficacy of this code, responses from PCs were measured at different vibratory burst durations. Since it is known that the P channel has the capacity to summate vibratory stimuli temporally within the central nervous system, the effect should also be present in the physiological results. Temporal summation predicts a decrease in threshold at a rate of -3 dB/doubling of stimulus duration. Responses from single PCs were integrated by counting neural spikes over the entire burst duration. Furthermore, real-time responses were integrated with a low-pass filter, more accurately modeling the central process. For the spike-counting scheme, a criterion of 4 impulses/stimulus showed a decrease in stimulus amplitude for increases in duration similar to that obtained psychophysically. The amplitude-duration function obtained with the low-pass filter, however, resulted in a function which did not follow that obtained psychophysically, regardless of the number of impulses/stimulus. Since the P channel is known to have a central integrator, it has been concluded that activity of a single PC afferent probably is not sufficient to signal threshold in the P channel.

Afferent Pathways↗

PubMed1990

Vibrotactile intensity discrimination measured by three methods.

The difference threshold for the detection of changes in vibration amplitude was measured as a function of the intensity and frequency of stimuli delivered through a 2.9-cm2 contactor to the thenar eminence. Stimuli were either 25- or 250-Hz sinusoids, narrow-band noise centered at 250 Hz, or wideband noise. Thresholds were measured by two-interval, forced-choice tracking under three methods of stimulus presentation. In the gated-pedestal method, subjects had to judge which of two 700-ms bursts of vibration separated by 100 ms was more intense. In the continuous-pedestal method, subjects had to detect a 700-ms increment in the amplitude of an ongoing pedestal of vibration. In the two-burst-continuous-pedestal method with 1500-ms pedestals, the subject had to detect which of two successively presented pedestals contained a 500-ms amplitude increment. Thresholds were consistently lower for detecting increments in the amplitude of a continuous pedestal of vibration than for detecting amplitude differences between briefly presented successive pedestals or amplitude increments in successive pedestals. A "near miss" to Weber's law was found both for sinusoidal and for noise stimuli. The difference threshold was not affected by stimulus frequency condition.

Adult↗

PubMed1989

Vibrotactile masking: effects of stimulus onset asynchrony and stimulus frequency.

Vibrotactile thresholds for the detection of a 50-ms vibratory stimulus on the thenar eminence of the hand were measured in the presence of and in the absence of a 700-ms suprathreshold vibratory masking stimulus. When thresholds were measured in the presence of the masking stimulus, stimulus onset asynchrony (SOA) was varied so that backward, simultaneous, and forward masking could be measured. The amount of masking, expressed as threshold shift, was greatest when the test stimulus was presented near the onset or offset of the masking stimulus. For both backward and forward masking, the amount of masking decreased as a function of increasing stimulus onset asynchrony. Comparisons were made of the amounts of masking measured when the test and masking stimuli were both sinusoids, and when the test stimulus was a sinusoid and the masking stimulus was noise. In all conditions, the masked threshold decreased approximately 4.0 dB when SOA was increased from 100 to 650 ms with reference to the onset of the 700-ms masking stimulus. More simultaneous masking was observed when sinusoidal test stimuli were detected in the presence of noise than when they were detected in the presence of sinusoidal maskers of the same frequency. The functions were essentially identical for detection of a low-frequency (20 Hz) test stimulus mediated by a non-Pacinian channel and detection of a high-frequency (250 Hz) test stimulus mediated by the Pacinian channel.

Adult↗

PubMed1988

Four channels mediate the mechanical aspects of touch.

Although previous physiological and anatomical experiments have identified four afferent fiber types (PC, RA, SA II, and SA I) in glabrous (nonhairy) skin of the human somatosensory periphery, only three have been shown to mediate tactile (mechanoreceptive) sensation. Psychophysical evidence that four channels (P, NP I, NP II, and NP III) do, indeed, participate in the perceptual process is presented. In a series of experiments involving selective masking of the various channels, modification of the skin-surface temperature, and testing cutaneous sensitivity down to very low-vibratory frequencies, the fourth psychophysical channel (NP III) is defined. Based on these experiments and previous work from our laboratory, it is concluded that the four channels work in conjunction at threshold to create an operating range for the perception of vibration that extends from at least 0.4 to greater than 500 Hz. Each of the four channels appears to mediate specific portions of the overall threshold-frequency characteristic. Selection of appropriate neural-response criteria from previously published physiological data and correlation of their derived frequency characteristics with the four psychophysical channels indicates that each channel has its own physiological substrate: P channel and PC fibers, NP I channel and RA fibers, NP II channel and SA II fibers, and NP III channel and SA I fibers. These channels partially overlap in their absolute sensitivities, making it likely that suprathreshold stimuli may activate two or more of the channels at the same time. Thus the perceptual qualities of touch may be determined by the combined inputs from four channels.

Adult↗

PubMed1987

Perceptual "blankout" of monocular homogeneous fields (Ganzfelder) is prevented with binocular viewing.

The loss of visual perception or "blankout" which occurs when a homogeneous field (Ganzfeld) is presented monocularly is prevented when the same field is viewed binocularly. Thus, blankout cannot be retinal; and contours or transients in time and space are unnecessary for the continuous maintenance of visual perception. Experiments are reported in which blankout ensues only if the two eyes receive luminance disparities ca 0.75 log I. Furthermore, blankout is only marginally affected by stimulus intensity, nor is it dependent on stimulus hue. However, equally luminant but disparate hues presented to the two eyes produce perceptions reminiscent of blankout, with the darkness of blankout replaced with that of color. It is hypothesized that the underlying mechanisms have a commonality in the phenomena of blankout and binocular rivalry but several noncongruent features require explanation.

Depth Perception↗

PubMed1987

Contourless stimuli produce binocular brightness summation.

Absolute magnitude estimates by 16 observers reveal that complete binocular brightness summation occurs for flashed Ganzfeld conditions. In other words, the view using both eyes appears twice as bright as with one. However, using the same technique, but with 2 degrees fields, no such summation is found. In addition to showing that, on the average, human observers can act as photometers, the results suggest that either complete summation or averaging of the monocular brightness can occur, depending upon the presence of contours.

Depth Perception↗

PubMed1986

The effects of skin temperature on the psychophysical responses to vibration on glabrous and hairy skin.

Psychophysical detection thresholds for vibration were measured at the thenar eminence and volar forearm using a 0.008-cm2 (1.0-mm-diam) contactor. Measurements were made at 14 sinusoidal frequencies between 12 and 500 Hz at six skin temperatures between 15 degrees and 40 degrees C. The results are consistent with the hypothesis that three functionally discrete non-Pacinian afferent systems mediate vibrotactile responses. It was possible to identify the response characteristic of the rapidly adapting (Meissner) system, but it was not possible to isolate the responses of two slowly adapting (SAI, SAII) systems.

Humans↗

PubMed1977

Efferent optic nerve fibers mediate circadian rhythms in the Limulus eye.

When the horseshoe crab is kept in constant darkness, the lateral eye produces larger electroretinographic and optic nerve responses at night than during the day. These circadian rhythms are mediated by synchronous bursts of efferent impulses in the optic nerve trunk. The endogenous efferent activity appears to increase both the gain and the quantum catch of the photoreceptors.

Action Potentials↗

PubMed1977

Vibrotactile frequency for encoding a speech parameter.

Frequency of vibration has not been widely used as a parameter for encoding speech-derived information on the skin. Where it has been used, the frequencies employed have not necessarily been compatible with the capabilities of the tactile channel, and no determination was made of the information transmitted by the frequency variable, as differentiated from other parameters used simultaneously, such as duration, amplitude, and location. However, several investigators have shown that difference limens for vibration frequency may be small enough to make stimulus frequency useful in encoding a speech-derived parameter such as the fundamental frequency of voiced speech. In the studies reported here, measurements have been made of the frequency discrimination ability of the volar forearm, using both sinusoidal and pulse waveforms. Stimulus configurations included the constant-frequency vibrations used by other laboratories as well as frequency-modulated (warbled) stimulus patterns. The frequency of a warbled stimulus was designed to have temporal variations analogous to those found in speech. The results suggest that it may be profitable to display the fundamental frequency of voiced speech on the skin as vibratory frequency, thought it might be desirable to recode fundamental frequency into a frequency range more closely matched to the skin's capability.

Acoustics↗