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Biomedical subjects

R T Verrillo

Publications and source records attributed to R T Verrillo.

14 recordsLinked to original sources
PubMed1979

Sensory functions in chronic neuralgia.

Eleven patients with sustained neuralgia, in most cases after traumatic nerve lesion, were subjected to quantitative sensory testing with thermal and non-noxious mechanical stimuli. Measurements were made in the pain area and at a homologous site on the contralateral normal side. All patients were hypoaesthetic with raised thresholds for warm and cold or touch, or both. Thermal pain thresholds were also raised in some patients but lowered in others indicating hypersensitivity of the nociceptor system or dysaesthesia for thermal input. In six patients single mechanical stimuli produced a painful response above the touch detection threshold. Reaction time measurements indicated that this painful response to suprathreshold mechanical pulses was measured by magnitude estimation as a function of stimulus amplitude. The results were fitted by power functions, as in normal skin, but with steeper slopes on the abnormal side. Suprathreshold hyperaesthesia (recruitment) may exist in the presence of normal threshold functioning.

Adult↗
PubMed1978

The effects of a surround on vibrotactile thresholds.

Psychophysical thresholds for the detection of vibration on the thenar eminence were measured as a function of stimulus frequency. As has been found in earlier studies, the threshold functions had two separate branches: one relatively flat branch at low frequencies and a U-shaped branch at higher frequencies. When the rigid surround which is used to confine the stimulus to the region of the vibrator contactor was removed and vibration was allowed to spread freely over the surface of the skin, thresholds along the relatively flat segment of the curve increased while thresholds along the U-shaped segment decreased. The results were interpreted in terms of the duplex model of mechanoreception.

Adult↗
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↗
PubMed1977

Enhancement of vibrotactile sensation magnitude and predictions from the duplex model of mechanoreception.

The degree to which the sensation magnitude of a vibrotactile stimulus is enhanced by a prior stimulus was studied for vibration of the thenar eminence of the right hand. Enhancement was measured by a psychophysical matching procedure in which two brief stimuli separated by a variable time interval were presented to the skin and the subject adjusted a third stimulus to match the sensation magnitude of the second stimulus. By this procedure, it is possible to determine functional relationships between enhancement and the time interval between stimuli, the intensity of the stimuli, and the frequency of the stimuli. The results were consistent with the duplex model of mechanoreception.

Differential Threshold↗
PubMed1976

Effect of double ipsilateral stimulation on vibrotactile sensation magnitude.

The phenomena of enhancement and suppression of vibrotactile subjective magnitude were investigated using a matching procedure. Results support earlier reports for audition and vibrotaction suggesting that enhancement is a fundamental sensory process. The time course is described for suppression of stimuli delivered to several different to several different pats of the body. The results are consistent with earlier studies of vibrotactile masking at threshold levels.

Adult↗