This work was supported by the Japan Society for the Promotion of Science KAKENHI Grants JP17J40084, JP18K15339, JP18H05009, JP18H01411, JP18K18835, and JP17K18855. We also thank the technician (Yoshihiko Tamura) in our laboratory for helping us craft the raised angle.

Written informed consent was obtained from the subjects in compliance with the policies of the local medical ethics committee of Okayama University. The testing procedures gained review and consent from the local medical ethics committee of Okayama University.
1. Detailed composition and function of equipment
<ol>
	<li>Tactile angle stimuli
	<ol>
		<li>The TSPAS uses two-dimensional (2D) raised angles to slide passively across the skin and form a tactile spatial representation of the angles (Figure 2). The tactile angles consist of plastic lines and square bases, which are both made from a transparent acrylic sheet. Because the lines composing the angles are equal and symmetrical, by symmetrically changing the spatial dimensions of the lines, all types of raised plane angles can be created.</li>
		<li>Using a milling machine, cut the acrylic sheet into the polyline with two equal lines (8.0 mm long, 1.5 mm wide, and 1.0 mm high) symmetrically distributed along an imaginary bisector and the square base (40.0 mm long and wide, 3.0 mm high).</li>
		<li>Glue the polyline to the center of the square base to create a 2D raised tactile angle stimulus.</li>
		<li>Make pieces with angle sizes ranging from 50&#176; to 70&#176; in 2&#176; increments. The end point distances (d, see Figure 2) of these angles are 6.8 mm, 7.0 mm, 7.3 mm, 7.5 mm, 7.8 mm, 8.0 mm (60&#176; angle), 8.2 mm, 8.5 mm, 8.7 mm, 8.9 mm, and 9.2 mm. To reduce the impact of the end point distance on angle discrimination to the minimum, use a 60&#176; angle as the reference angle, and other angles as comparison angles.</li>
		<li>Make up 20 pairs of discriminated angles, including 20 identical reference angles and 10 pairs of identical comparison angles whose measured accuracies are &#177; 0.2&#176;. Ensure that the reference angle is presented first 50% of the time when each pair is tested. The experiment can be easily and conveniently updated with tactile angle stimuli.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61218/61218fig02.jpg" /> 
Figure 2: Example of tactile angle stimuli. 
(A) An example of the reference angle (60&#176;) and two (50&#176; and 70&#176;) of the ten comparison angles used in the experiment. In particular, detailed parameters of the reference angle were drawn. d represents the end point distance, R represents the radius of curvature in the local apex, and r represents the radius of curvature in the end point. (B) Example of a raised angle seen in 3D. The height of the raised line is 1.0 mm from the 3D view. <a href="https://www.jove.com/files/ftp_upload/61218/61218fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Hand plate
	<ol>
		<li>To stabilize the subject&#39;s hand, craft a hand plate perpendicular to the electronic slide (Figure 3). First, using a milling machine, cut a 5.0 mm thick acrylic sheet into a 14.0 cm x 22.0 cm rectangle plate, and then fasten the rectangle plate to a base (14.0 cm wide, 14.0 cm long, and 8.5 high) with tape and glue. After that, using a milling machine, cut a rectangular opening (2.5 cm wide and 5.0 cm long) in the upper left corner of the plate. This allows only the index finger to contact the angle stimulus. Before the experiment, fix the subject&#39;s right hand wrist with nylon tape, and then instruct the subjects to lightly place their right index fingers at the opening of the plate.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61218/61218fig03.jpg" /> 
Figure 3: Hand position of the subject and tactile angle stimuli movement direction. 
The right hand of the subject was secured with nylon tape, and the subject was instructed to place his or her right index finger into the opening in the plate. The angle stimuli were clamped on the apparatus and were horizontally moved by the electronic slide to passively slide across the fingerpad. <a href="https://www.jove.com/files/ftp_upload/61218/61218fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>Motorized linear slide
	<ol>
		<li>The electronic slide with a maximum motion distance of 51.0 cm is moved in a straight direction using an easy linear motion motor with 5.0 cm high, 5.4 cm wide, and 71.0 cm long (see Table of Materials), which is a linear-motion system. Connect the motor to a personal computer and set and edit various data using dedicated data editing software (see Table of Materials). Ensure that these settings can make the electronic slide move a specified distance using a given speed with respect to the reference point. This is necessary when moving the angle stimuli directly from an arbitrary position to a specified position.</li>
	</ol>
	</li>
	<li>Computer control system
	<ol>
		<li>The TSPAS is a semiautomatic, computer-controlled system. The data editing software used to control the movement of the slide is PC-based software for editing the data necessary for the operation of motorized actuators. In the experiment, set the velocity of the slide at 20 mm/s and its moving distance at 80 mm for each trial. Each time a button is clicked, the slide moves as previously set.</li>
	</ol>
	</li>
</ol>
2. Running an experiment
<ol>
	<li>Before the experiment, first set the motion type as &#8216;INC&#8217;, motion distance as &#8216;80 mm&#8217;, motion speed as &#8216;20 mm/s&#8217;, motion function as &#8216;single&#8217;, and axis as &#8216;ID = 0&#8217; in the data editing software (see the operating manual in the Table of Materials for instructions on how to set parameters) to ensure that the electronic slide can move both at a distance of 80 mm and a speed of 20 mm/s forward and backward, and at other distances and speeds.</li>
	<li>Recruit subjects whose fingers are free of injuries and calluses. Try to recruit an equal number of male and female subjects within the age range from 18&#8211;35 years old. Note that there is a difference in tactile spatial acuity between female and male subjects, as well as old and young subjects25,26.</li>
	<li>Blindfold the subject and sit him or her at a table with the apparatus (Figure 1). Fix the right hand of the subject with nylon tape and subsequently instruct the subject to lightly place his or her right index finger at the opening of the hand plate (Figure 3).</li>
	<li>Clamp a pair of angles, including the reference angle and the comparison angle, on the slide. After clicking the button, the pair of angles slide for a total distance of 80 mm. They passively go across the index fingerpad at a speed of 20 mm/s. Because there is a distance of 31.8 &#177; 0.8 mm between the reference angle and comparison angle, their interstimulus time interval is approximately 1.6 s.</li>
	<li>After the subject perceives the sizes of the angles, he or she orally reports which of the two angles is larger. If the subject cannot identify which angle is larger, he or she can indicate that the angles are the same. Register the answer of the subject as the response data. After that, the next pair of angles will be continually replaced, presented, and perceived in the same way.</li>
	<li>There are a total of 10 pairs of angles in the formal experiment. Present each pair 10x in a pseudorandom order in which the reference angle passes first 50% of the time. Thus, the experiment contains 100 trials. To avoid uncomfortable sensations on the index finger, after each series of 20 trials have the subject take a 3 min break. Before the experiment, each subject practices 10 trials with other angles to be familiar with the experimental procedure. The experiment should last ~40 min.</li>
</ol>

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The authors declare that they have no competing conflicts of interest, financial or otherwise.

A new measure for tactile spatial acuity, tactile AD, is presented. In this system a pair of angles passively slides across the immobilized index fingerpad of a subject. AD combines the advantages of GO and TPD, reducing the impact of intensive cues and the neural peak impulse rate of a single point. This study shows that there is a gradual change in perceptual discrimination as the angle difference changes between the reference angle and the comparison angle4. In addition to the age effect, train...

Touch perception is a fundamental form of the sensations processed by the somatosensory system, including haptic perception and tactile perception. Passive tactile perception, as opposed to active exploration, means that the object is moved to make contact with static skin1,2. As in other senses, spatial resolution in tactile perception, also termed tactile spatial acuity, is usually represented by the tactile threshold, detection threshold, or discrimination threshold2,3. In the past 100 years, the two-point threshold has commonly been used as a measure of tactile spatial acuity4. However, many studies have indicated that the two-point threshold is an invalid index of tactile spatial ability because two-point discrimination (TPD) cannot exclude nonspatial cues (e.g., if two points are too close, they may locate a single afferent receptive field, which readily evokes increased neural activity) and maintain a stable criterion for responses3,4,5. Owing to the number of drawbacks of TPD, several new and promising methods have been developed as replacements, such as tactile grating orientation (GO)3,6, two-point orientation discrimination5, raised letter recognition, gap detection7, dot patterns, Landolt C rings8, and angle discrimination (AD)9,10. At present, because of the advantages in operating GO, as well as the spatial structure and complexity of the stimulus used, GO is increasingly used to measure tactile spatial acuity11,12,13.
Although tactile GO is thought to rely on underlying spatial mechanisms, thereby yielding a reliable measure of tactile spatial acuity, it is still debated whether GO performance is partly affected by nonspatial cues14 (e.g., intensive signs that may provide a cue to identify the difference between orientation stimuli). Additionally, GO only consists of simple spatial orientation (i.e., horizontal and vertical) tasks and primarily involves sensory processing, which limits its use when exploring the hierarchical interplay between tactile primary processing in the primary somatosensory cortex and tactile advanced possessing involving the posterior parietal cortex (PPC) and supramarginal gyrus (SMG)15,16,17. To compensate for these drawbacks, tactile AD was developed to measure tactile spatial acuity9,10. In AD, a pair of angles passively slide across the fingertip. The angles vary in size, and the subject needs to determine which of the angles is larger. To consistently accomplish this task, spatial features of tactile angles must be represented and stored in the working memory and then compared and discerned. Therefore, tactile AD involves not only primary processing but also advanced cognition of tactile perception, such as working memory and attention.
As in a variety of line orientation perception tests, in tactile AD the subject is presented successively with one reference angle and one comparison angle and is asked to indicate which is the larger angle18,19,20,21. The lines composing the angles are equal in length and symmetrically distributed along an imaginary bisector. By symmetrically changing the spatial dimensions of the lines, all types of raised plane angles can be created. Therefore, a critical advantage of this method is that the angles being differentiated have similar spatial structures. In addition, the spatial representation gained in the AD is more sequential than that gained in GO. However, the AD threshold provides evidence that tactile spatial acuity is sufficient to allow spatial discrimination between objects22. Furthermore, the tactile spatial perception of the angle may be experienced from point to line and finally form a two-dimensional plane angle in which nonspatial cues may play only a small role.
The AD threshold was found to increase with increasing age, which might result from the need for high cognitive load in the tactile AD task. Thus, it may provide a monitoring mechanism in cognitive impairment diagnosis9,10. Although AD performance is affected by age-related decline, it can be significantly improved in young people by continuous training or similar tactile task training23. Furthermore, fMRI studies showed that a delayed match-to-sample tactile angle task activated certain cortical regions responsible for working memory, such as the posterior parietal cortex17,24. These findings suggest that tactile angle discrimination is a promising measure for tactile spatial acuity involving advanced cognition. Here, the tactile AD equipment and its use is described in detail. Other tactile researchers can reproduce the AD equipment and use it in their research.
The tactile AD equipment, or tactile semiautomatic passive-finger angle stimulator (TSPAS), uses an electronic slide to convey a pair of angle stimuli to slide passively across the skin (Figure 1). The subjects&#39; arms lie comfortably, prostrate on a tabletop. The right hand sits on a hand plate in the table, and an index fingerpad is situated slightly below the opening of the plate. Computer software can control the slide, move it at a fixed speed, and move it forward and backward. As the slide moves forward, the angle stimuli slide passively across the skin at a fixed speed starting at the fingertip. When the slide moves backward to its starting position and changes to another pair of angle stimuli, the subject needs to lift the index finger up and wait for an order to lightly place it again at the opening. Thus, the equipment presents tactile angle stimuli at a controlled speed, stable contact duration, and constant interstimulus interval. The subject orally reports a sequence number, and the experimenter registers it as a response and proceeds to conduct the next trial.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61218/61218fig01.jpg" /> 
Figure 1: Overview of the TSPAS. 
The equipment consists of four parts: 1) tactile angle stimuli (i.e., the reference angle and ten comparison angles); 2) the hand plate that fixes the hand of the subject in place and keeps only the index finger in contact with the stimuli; 3) the electronic slider that carries the tactile stimuli; and 4) the personal computer (PC) control system that controls the speed and the movement distance of the electronic slide. <a href="https://www.jove.com/files/ftp_upload/61218/61218fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table>
	<tbody>
		<tr>
			<td>Acrylic sheet (3 mm)</td>
			<td>MonotaRO Co.,Ltd.</td>
			<td>33159874</td>
			<td>Good Material</td>
		</tr>
		<tr>
			<td>Acrylic sheet (1 mm)</td>
			<td>MonotaRO Co.,Ltd.</td>
			<td>45547101</td>
			<td>Good Material</td>
		</tr>
		<tr>
			<td>EZ limo (easy linear motion motor)</td>
			<td>ORIENTAL MOTOR CO., LTD. Made in Japan</td>
			<td>EZS3</td>
			<td>Good Motorized Linear Slides</td>
		</tr>
		<tr>
			<td>Data Editing Software</td>
			<td>ORIENTAL MOTOR CO., LTD. Made in Japan</td>
			<td>EZED2</td>
			<td>easy to use</td>
		</tr>
		<tr>
			<td>Operating Manual (Orientalmotor)</td>
			<td>ORIENTAL MOTOR CO., LTD. Made in Japan</td>
			<td>HL-17151-2</td>
			<td>Good Guidebook</td>
		</tr>
	</tbody>
</table>

tactile semiautomatic passive-finger angle stimulator (tspas)

Passive tactile perception is the ability to passively and statically perceive stimulus information coming from the skin; for example, the ability to sense spatial information is the strongest in the skin on the hands. This ability is termed tactile spatial acuity, and is measured by the tactile threshold or discrimination threshold. At present, the two-point threshold is extensively used as a measure of tactile spatial acuity, although many studies have indicated that critical deficits exist in two-point discrimination. Therefore, a computer-controlled tactile stimulus system was developed, the tactile semiautomated passive-finger angle stimulator (TSPAS), using the tactile angle discrimination threshold as a new measure for tactile spatial acuity. The TSPAS is a simple, easily operated system that applies raised angle stimuli to a subject&#39;s passive fingerpad, while controlling movement speed, distance, and contact duration. The components of the TSPAS are described in detail as well as the procedure to calculate the tactile angle discrimination threshold.

In this study, the 3AFC (3-alternative forced-choice) technique and the logistic curve were used to estimate the tactile AD threshold. Participants were instructed to orally report the larger of the two angles perceived, or if they did not detect the difference, they could indicate the same. The equation of the logistic curve, which has been commonly applied to psychophysical experiments to measure thresholds27,28,29 is:
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Tactile Semiautomatic Passive-Finger Angle Stimulator TSPAS

Presented is the tactile semiautomated passive-finger angle stimulator TSPAS, a new way to assess tactile spatial acuity and tactile angle discrimination using a computer-controlled tactile stimulus system that applies raised angle stimuli to a subject&#39;s passive fingerpad, while controlling for movement speed, distance, and contact duration.

Tactile Semiautomatic Passive-Finger Angle Stimulator (TSPAS)

Passive tactile perception is the ability to passively and statically perceive stimulus information coming from the skin; for example, the ability to ...

tactile-semiautomatic-passive-finger-angle-stimulator-tspas

Research

JoVE Journal

Behavior

2.8K Views.  Okayama University. Presented is the tactile semiautomated passive-finger angle stimulator TSPAS, a new way to assess tactile spatial acuity and tactile angle discrimination using a computer-controlled tactile stimulus system that applies raised angle stimuli to a subject's passive fingerpad, while controlling for movement speed, distance, and contact duration.

Video: Tactile Semiautomatic Passive-Finger Angle Stimulator TSPAS

Quantitative Assessment of Cortical Auditory-tactile Processing in Children with Disabilities

Objective and easy measurement of sensory processing is extremely difficult in nonverbal or vulnerable pediatric patients. We developed a new methodology to quantitatively assess children&#39;s cortical processing of light touch, speech sounds and the multisensory processing of the 2 stimuli, without requiring active subject participation or causing children discomfort. To accomplish this we developed a dual channel, time and strength calibrated air puff stimulator that allows both tactile stimulation and sham control. We combined this with the use of event-related potential methodology to allow for high temporal resolution of signals from the primary and secondary somatosensory cortices as well as higher order processing. This methodology also allowed us to measure a multisensory response to auditory-tactile stimulation.

Objective and easy measurement of sensory processing is extremely difficult in nonverbal or vulnerable pediatric patients. We developed a new methodology to quantitatively assess infants and children&#39;s cortical processing of light touch, speech sounds, and the multisensory processing of the 2 stimuli, without requiring active subject participation or causing discomfort in vulnerable patients.

Objective and easy measurement of sensory processing is extremely difficult in nonverbal or vulnerable pediatric patients. We developed a new methodology ...

Measurement of Vibration Detection Threshold and Tactile Spatial Acuity in Human Subjects

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about mechanosensory function that are relevant for clinical diagnosis as well as for basic research. Here, we describe two psychophysical tests designed to determine the vibration detection threshold (automated system) and tactile spatial acuity (handheld device). Both procedures implement a two-interval forced-choice and a transformed-rule up and down experimental paradigm. These tests have been used to obtain mechanosensory profiles for individuals from distinct human cohorts such as twins or people with sensorineural deafness.

Here, we present protocols to determine vibration detection thresholds and tactile acuity using psychophysical methods in man.

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about ...

Testing Tactile Masking between the Forearms

Masking, in which one stimulus affects the detection of another, is a classic technique that has been used in visual, auditory, and tactile research, usually using stimuli that are close together to reveal local interactions. Masking effects have also been demonstrated in which a tactile stimulus alters the perception of a touch at a distant location. Such effects can provide insight into how components of the body's representations in the brain may be linked. Occasional reports have indicated that touches on one hand or forearm can affect tactile sensitivity at corresponding contralateral locations. To explore the matching of corresponding points across the body, we can measure the spatial tuning and effect of posture on contralateral masking. Careful controls are required to rule out direct effects of the remote stimulus, for example by mechanical transmission, and also attention effects in which thresholds may be altered by the participant's attention being drawn away from the stimulus of interest. The use of this technique is beneficial as a behavioural measure for exploring which parts of the body are functionally connected and whether the two sides of the body interact in a somatotopic representation. This manuscript describes a behavioural protocol that can be used for studying contralateral tactile masking.

Here we explore contralateral tactile masking between the forearms in which tactile detection thresholds are modulated by vibration applied to a remote site. The details of which remote sites have an effect can tell us about how the body is represented in the brain.

Masking, in which one stimulus affects the detection of another, is a classic technique that has been used in visual, auditory, and tactile research, ...

Applying Incongruent Visual-Tactile Stimuli during Object Transfer with Vibro-Tactile Feedback

The application of incongruent sensory signals that involves disrupted tactile feedback is rarely explored, specifically with the presence of vibrotactile feedback (VTF). This protocol aims to test the effect of VTF on the response to incongruent visual-tactile stimuli. The tactile feedback is acquired by grasping a block and moving it across a partition. The visual feedback is a real-time virtual presentation of the moving block, acquired using a motion capture system. The congruent feedback is the reliable presentation of the movement of the block, so that the subject feels that the block is grasped and see it move along with the path of the hand. The incongruent feedback appears as the movement of the block diverts from the actual movement path, so that it seems to drop from the hand when it is actually still held by the subject, thereby contradicting the tactile feedback. Twenty subjects (age 30.2 &#177; 16.3) repeated 16 block transfers, while their hand was hidden. These were repeated with VTF and without VTF (total of 32 block transfers). Incongruent stimuli were presented randomly twice within the 16 repetitions in each condition (with and without VTF). Each subject was asked to rate the difficulty level of performing the task with and without the VTF. There were no statistically significant differences in the length of the hand paths and durations between transfers recorded with congruent and incongruent visual-tactile signals &#8211; with and without the VTF. The perceived difficulty level of performing the task with the VTF significantly correlated with the normalized path length of the block with VTF (r = 0.675, p = 0.002). This setup is used to quantify the additive or reductive value of VTF during motor function that involves incongruent visual-tactile stimuli. Possible applications are prosthetics design, smart sport-wear, or any other garments that incorporate VTF.

We present a protocol to apply incongruent visual-tactile stimuli during an object transfer task. Specifically, during block transfers, performed while the hand is hidden, a virtual presentation of the block shows random occurrences of false block drops. The protocol also describes adding vibrotactile feedback while performing the motor task.

The application of incongruent sensory signals that involves disrupted tactile feedback is rarely explored, specifically with the presence of vibrotactile ...

Tactile Vibrating Toolkit and Driving Simulation Platform for Driving-Related Research

Collision warning system plays a key role in the prevention of driving distractions and drowsy driving. Previous studies have proven the advantages of tactile warnings in reducing driver&#8217;s brake response time. At the same time, tactile warnings have been proved effective in take-over request (TOR) for partially autonomous vehicles.
How the performance of tactile warnings can be optimized is an ongoing hot research topic in this field. Thus, the presented low-cost driving simulation software and methods are introduced to attract more researchers to take part in the investigation. The presented protocol has been divided into five sections: 1) participants, 2) driving simulation software configuration, 3) driving simulator preparation, 4) vibrating toolkit configuration and preparation, and 5) conducting the experiment.
In the exemplar study, participants wore the tactile vibrating toolkit and performed an established car-following task using the customized driving simulation software. The front vehicle braked intermittently, and vibrating warnings were delivered whenever the front vehicle was braking. Participants were instructed to respond as quickly as possible to the sudden brakes of the front vehicle. Driving dynamics, such as the brake response time and brake response rate, were recorded by the simulation software for data analysis.
The presented protocol offers insight into the exploration of the effectiveness of tactile warnings on different body locations. In addition to the car-following task that is demonstrated in the exemplar experiment, this protocol also provides options&#160;to apply other paradigms to the driving simulation studies by making simple software configuration without any code development. However, it is important to note that due to its affordable price, the driving simulation software and hardware introduced here may not be able to fully compete with other high-fidelity commercial driving simulators. Nevertheless, this protocol can act as an affordable and user-friendly alternative to the general high-fidelity commercial driving simulators.

This protocol describes a driving simulation platform and a tactile vibrating toolkit for the investigation of driving-related research. An exemplar experiment exploring the effectiveness of tactile warnings is also presented.&#160;

Collision warning system plays a key role in the prevention of driving distractions and drowsy driving. Previous studies have proven the advantages of ...

Assessment of Spatial Lingual Tactile Sensitivity using a Gratings Orientation Test

Individual thresholds by R-index estimates are calculated using a gratings orientation test (6 different tools of increasing grating size from 0.20-1.25 mm) to assess spatial lingual tactile sensitivity. During the experiment, the subjects are blindfolded and asked to specify the orientation of the grating (either horizontal or vertical) placed on the tongue. R-index is based on Signal Detection Theory (SDT), and it is an estimated probability of correctly identifying a target stimulus (the signal, e.g., the correct orientation) compared to an alternative stimulus (the noise, e.g., the incorrect orientation). Once the R-index values for each subject and each tool dimension are calculated, it is possible to derive the individual threshold by interpolating the two R-indices immediately below and above the established cut-off (typically 75%) based on one-sided R-index critical values. This procedure can be helpful in the medical field to study the association between oral tactile sensitivity, speech clarity, and swallowing disorders, as well as in sensory and consumer studies to explore individual variation in texture perception, food preferences, and eating behavior.

This work illustrates a standard procedure and threshold determination by the R-index to assess spatial lingual tactile sensitivity using a gratings orientation test.

Individual thresholds by R-index estimates are calculated using a gratings orientation test (6 different tools of increasing grating size from 0.20-1.25 ...