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.

BackgroundTouch is a crucial sense for perceiving the spatial characteristics of objects. The JVP dome was developed to evaluate tactile spatial acuity using a grating orientation task. There were few studies depicting sequences and details for the entire task, including practice, training, and testing sessions. Therefore, we proposed and elaborated a protocol for the grating orientation task using the staircase method, which required fewer testing trials compared with the method of constant stimuli.MethodsTwenty‐three healthy participants were enrolled in this experiment. The JVP domes with 11 different groove widths were used. Tactile discrimination thresholds were estimated using a two‐down‐one‐up staircase method. The experiment comprised practice, training, and testing sessions, conducted by trained examiners who performed grating stimulation on participants’ index fingerpads.ResultsAll participants passed the required accuracy in the practice and training sessions. Eight transition points were obtained in the testing session for each participant. The tactile discrimination thresholds were determined from the last six transition points. We obtained the mean tactile discrimination threshold as 1.8 ± 0.75 mm (n = 23). The results demonstrated that the proposed protocol was successfully applied to assess tactile discrimination thresholds.ConclusionsThe present study investigated the protocol of grating orientation tasks requiring a small number of testing trials with the assurance of the task quality. The feasibility study and preliminary results indicated the potentiality of this protocol for future clinical application.

Touch is a crucial sense for perceiving the spatial characteristics of objects. The JVP dome was developed to evaluate tactile spatial acuity using a grating orientation task. The application of the traditional JVP dome to assess tactile function was limited by the ceiling effect, excessive transition gap between grating widths causing inaccurate tactile discrimination threshold measurement, and predictive bias due to the common execution protocol using grating widths in sequence. In this study, we included additional grating domes and proposed a modified examining protocol for estimating tactile discrimination thresholds to improve the accuracy of tactile function assessment. Twelve healthy participants were enrolled in this experiment. Extended JVP domes with 11 different groove widths were designed. Tactile discrimination thresholds were estimated using a modified two-down-one-up staircase method. The experiment comprised practice, training, and testing sessions, conducted by trained examiners who performed grating stimulation on participants index fingerpads. All participants passed the required accuracy in the practice and training sessions. Eight transition points were obtained in the testing session for each participant, and tactile discrimination thresholds were all within the width range of the extended JVP domes. The mean tactile discrimination threshold was 2.09 ± 0.84 mm. The results demonstrated that the proposed modified JVP dome set and protocol were successfully applied to assess tactile discrimination thresholds. The modified protocol with extended JVP domes provided an effective assessment of tactile function and improved the precision of threshold measurements, avoided the ceiling effect found in traditional JVP dome, and eliminated predictive bias.