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Biomedical subjects

R T Verrillo

Publications and source records attributed to R T Verrillo.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1985

Psychophysics of vibrotactile stimulation.

The effects of a wide range of stimulus parameters upon the psychophysical responses of subjects are important to an understanding of the functional characteristics of neural systems that underlie responses to cutaneous mechanical stimulation and the interactions that may occur between these systems. This understanding may also be useful to design considerations in the development of devices for tactile communication. This paper begins with a brief description of the two major systems in terms of psychophysical measurements and then focuses on a more detailed examination of possible interactions between them. The effects of time and space variables, such as frequency, temporal and intensity relationships between stimuli, area of stimulation, and surface gradients on the skin, are considered.

Acoustic Stimulation↗
PubMed1985

Vibrotactile forward masking: psychophysical evidence for a triplex theory of cutaneous mechanoreception.

Threshold shifts for the detection of vibrotactile test stimuli were determined as a function of the intensity of a masker. A 50-ms sinusoidal test stimulus was applied to the thenar eminence of the hand 25 ms after the termination of a 700-ms sinusoidal masker applied to the same site. The frequency of the test stimulus and the frequency of the masker were varied. To eliminate the influence of the Pacinian receptor system, stimuli were delivered through a 0.01-cm2 contactor. The results support the hypothesis that the detection of vibration delivered through a small contactor is determined by two separate populations of non-Pacinian receptors. The study constitutes a psychophysical demonstration of the existence of three receptor systems responsible for the detection of vibration.

Adult↗
PubMed1983

Vibrotactile subjective magnitude as a function of hand preference.

The vibrotactile subjective magnitudes of test stimuli were determined by a psychophysical matching technique as a function of the time interval between conditioning and test stimuli in right-, left-, and ambi-handed subjects. Ipsilateral stimulation on either hand produced equal amounts of enhancement of subjective magnitude in all subjects. Contralateral stimulation produced suppression, followed by enhancement in right- and left-handers, but produced no effect in ambi-handers. The results suggest that the bilateral neural connections of ambi-handers is different from those of right- and left-handers.

Female↗
PubMed1983

Vibrotacile masking of Pacinian and non-Pacinian channels.

Vibrotactile masking functions were determined using sinusoidal and noise maskers. Results were nearly identical within the Pacinian (P) and non-Pacinian (NP) channels. At low maskers SLs there was a substantial amount of negative masking which proved not be an artifact of stimulus definition. The critical parameters for successful prediction of the data were a peripheral threshold and internal Gaussian noise. Threshold shifts in cross-channel stimulation can be attributed to the masker exceeding the detection threshold of the signal channel.

Adult↗
PubMed1983

Vibrotactile forward masking: evidence for channel independence.

Threshold shifts for the detection of vibrotactile test stimuli were determined as a function of the intensity of a masker. A 50-ms sinusoidal test stimulus was applied to the thenar eminence of the hand 25 ms after the termination of a 700-ms sinusoidal masker applied to the same site. The intensity of the masker was varied over a range of 0-44 dB SL. The frequency of the masker was either 15 or 250 Hz and the frequency of the test stimulus was either 15, 25, 100, or 250 Hz. The results support the hypothesis that the detection of vibrotactile stimuli is mediated by at least two receptor systems which do not mask each other.

Adolescent↗
PubMed1981

Absolute estimation of line length in three age groups.

The effect of age upon the subjective magnitude of line length was assessed by the method of absolute magnitude estimation in three groups of subjects with mean ages of 25, 50, and 68 years. The results showed no significant differences between the groups. When compared to data from an earlier study in which 5- to 6-year-old children were tested by the same method, the results were essentially the same, but with a slightly steeper slope for the 5- to 6-year-olds. The subjective length of lines appears to remain stable over an extended age range.

Adult↗
PubMed1980

Age related changes in the sensitivity to vibration.

Vibrotactile detection thresholds were measured for five groups of subjects grouped according to age. The age span was eight to 74 years and the mean ages of the groups were 10, 20, 35, 50, and 65 years. Measurements were made on the thenar eminence of the right hand using sinusoidal wave forms at 11 frequencies. The results show a progressive decrease in sensitivity with age at high frequencies and no change at low (25 and 40 Hz) frequencies. The results are discussed within the context of the duplex model of mechanoreception and in terms of structural changes that occur with age in the cutaneous receptors.

Adolescent↗
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↗