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Objective: We aimed to determine the ability of an innovative device, the Cutaneous Mechanical Stimulator (CMS), to evaluate touch sensory pathways in Human., Methods: Two experiments were conducted in 23 healthy volunteers aged 20-30 years. In the first, mechanical detection thresholds (MDTs) were assessed using Semmes-Weinstein monofilaments and the CMS. In the second experiment, touch-evoked potentials (TEPs) elicited by tactile stimulation of the CMS on the left hand dorsum and left foot dorsum were recorded. Electroencephalographic (EEG) data were recorded at each cutaneous stimulation site in blocks of 20 tactile stimulations delivered by the CMS. The data were segmented into 1000-ms epochs., Results: MDTs measured by monofilaments and by the CMS were equivalent. Analyses of TEPs showed N2 and P2 components. The latencies of the N2 components on the hand dorsum and foot dorsum resulted in an estimated average conduction velocity of about 40 m.s -1 , within the range of Aβ fibers., Conclusions: These findings showed that the CMS could assess touch sensory pathways in young adults., Significance: The CMS can offer new research perspectives, as this device allows easy assessment of the MDT and enables estimation of fiber conduction velocities after tactile stimulation by the device synchronized with EEG recordings., (Copyright © 2023 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Several methods for the measurement of tactile acuity have been devised previously, but unexpected nonspatial cues and intensive manual skill requirements compromise measurement accuracy. Therefore, we must urgently develop an automated, accurate, and noninvasive method for assessing tactile acuity. The present study develops a novel method applying a robotic tactile stimulator to automatically measure tactile acuity that comprises eye-opened, eye-closed training, and testing sessions. Healthy participants judge the orientation of a rotating grating ball presented on their index fingerpads in a two-alternative forced-choice task. A variable rotation speed of 5, 10, 40, or 160 mm/s was used for the tactile measurement at a variety of difficulties. All participants met the passing criteria for the training experiment. Performance in orientation identification, quantified by the proportion of trials with correct answers, differed across scanning directions, with the highest rotation speed (160 mm/s) having the worst performance. Accuracy did not differ between vertical and horizontal orientations. Our results demonstrated the utility of the pre-test training protocol and the functionality of the developed procedure for tactile acuity assessment. The novel protocol performed well when applied to the participants. Future studies will be conducted to apply this method to patients with impairment of light touch.

In this study, we developed a tactile stimulator capable of administering either puff- or suction-type stimuli. The system is composed of three parts: a control unit, an air-handling unit, and a stimulation unit. The control unit controls the type, intensity, and time of stimulation. The air-handling unit delivers the stimulation power quantitatively to the stimulation unit, as commanded by the control unit. The stimulation unit stably administers either type of pressure to the skin, without any change of the tactor. Although the design of the stimulator is simple, it allows for five levels of control of the stimulation intensity (2-6 psi) and 0.1-s steps of control of the stimulation time, as we confirmed by tests. Preliminary electroencephalographic and event-related potential (ERP) studies of our system in humans confirmed the presence of N100 and P300 waves at standard electrode position C3, which are related to perception and cognition, respectively, in the somatosensory area of the brain. In addition, different stimulation types (puff and suction) and intensities (2 and 6 psi) were reflected in different peak-to-peak amplitudes and slopes of the mean ERP signal. The system developed in this study is expected to contribute to human tactile studies by providing the ability to administer puff- or suction-type stimuli interchangeably.

In this study, a tactile stimulator that could separately or simultaneously display the vibrotactile and pressure sense was developed. The developed system consisted of a control unit, a drive unit, and an actuator, and can be operated with PC or manually. This system quantitatively controls the stimulation parameters such as the stimulation intensity, duration, frequency, and stimulation type. A preliminary electroencephalogram (EEG) experiment for three types of stimulation (vibrotactile, pressure sense, vibrotactile + pressure sense) highlights that the system could be used in complex tactile cognitive studies. An event-related desynchronization (ERD) and synchronization (ERS) were measured at the area of C3 and C4 for all three types of stimulation, and a clear response was identified in the contralateral somatosensory area from the brain topology. Therefore, it is expected that this system could be widely used in single and complex human tactile cognition and perception studies for vibrotactile and pressure sensation.