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 ...

<ol>
	<li>Smith, A. M., Chapman, C. E., Donati, F., Fortier-Poisson, P., Hayward, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perception+of+simulated+local+shapes+using+active+and+passive+touch.">Perception of simulated local shapes using active and passive touch.</a> Journal of Neurophysiology. 102 (6), 3519-3529 (2009).</li><li>Reuter, E. M., Voelcker-Rehage, C., Vieluf, S., Godde, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Touch+perception+throughout+working+life:+Effects+of+age+and+expertise.">Touch perception throughout working life: Effects of age and expertise.</a> Experimental Brain Research. 216 (2), 287-297 (2012).</li><li>Craig, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grating+orientation+as+a+measure+of+tactile+spatial+acuity.">Grating orientation as a measure of tactile spatial acuity.</a> Somatosensory and Motor Research. 16 (3), 197-206 (1999).</li><li>Craig, J. C., Johnson, K. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+two-point+threshold:+Not+a+measure+of+tactile+spatial+resolution.">The two-point threshold: Not a measure of tactile spatial resolution.</a> Current Directions in Psychological Science. 9 (1), 29-32 (2000).</li><li>Tong, J., Mao, O., Goldreich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-point+orientation+discrimination+versus+the+traditional+two-point+test+for+tactile+spatial+acuity+assessment.">Two-point orientation discrimination versus the traditional two-point test for tactile spatial acuity assessment.</a> Frontiers in Human Neuroscience. 7, 1-11 (2013).</li><li>Goldreich, D., Wong, M., Peters, R. M., Kanics, I. 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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retention+of+high+tactile+acuity+throughout+the+life+span+in+blindness.">Retention of high tactile acuity throughout the life span in blindness.</a> Perception and Psychophysics. 70 (8), 1471-1488 (2008).</li><li>Yang, J., Ogasa, T., Ohta, Y., Abe, K., Wu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decline+of+human+tactile+angle+discrimination+in+patients+with+mild+cognitive+impairment+and+Alzheimer's+disease.">Decline of human tactile angle discrimination in patients with mild cognitive impairment and Alzheimer's disease.</a> Journal of Alzheimer's Disease. 22 (1), 225-234 (2010).</li><li>Wu, J., Yang, J., Ogasa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raised-angle+discrimination+under+passive+finger+movement.">Raised-angle discrimination under passive finger movement.</a> Perception. 39 (7), 993-1006 (2010).</li><li>Sathian, K., Zangaladze, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+learning+is+task+specific+but+transfers+between+fingers.">Tactile learning is task specific but transfers between fingers.</a> Perception and Psychophysics. 59 (1), 119-128 (1997).</li><li>Wong, M., Peters, R. M., Goldreich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+physical+constraint+on+perceptual+learning:+tactile+spatial+acuity+improves+with+training+to+a+limit+set+by+finger+size.">A physical constraint on perceptual learning: tactile spatial acuity improves with training to a limit set by finger size.</a> Journal of Neuroscience. 33 (22), 9345-9352 (2013).</li><li>Trzcinski, N. K., Gomez-Ramirez, M., Hsiao, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+consequences+of+experience-dependent+plasticity+on+tactile+perception+following+perceptual+learning.">Functional consequences of experience-dependent plasticity on tactile perception following perceptual learning.</a> European Journal of Neuroscience. 44 (6), 2375-2386 (2016).</li><li>Essock, E. A., Krebs, W. K., Prather, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superior+Sensitivity+for+Tactile+Stimuli+Oriented+Proximally-Distally+on+the+Finger:+Implications+for+Mixed+Class+1+and+Class+2+Anisotropies.">Superior Sensitivity for Tactile Stimuli Oriented Proximally-Distally on the Finger: Implications for Mixed Class 1 and Class 2 Anisotropies.</a> Journal of Experimental Psychology: Human Perception and Performance. 23 (2), 515-527 (1997).</li><li>Gurtubay-Antolin, A., Leon-Cabrera, P., Rodriguez-Fornells, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+evidence+of+hierarchical+cognitive+control+during+Haptic+processing:+An+fMRI+study.">Neural evidence of hierarchical cognitive control during Haptic processing: An fMRI study.</a> eNeuro. 5 (6), (2018).</li><li>Yang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+priming+modulates+the+activation+of+the+fronto-parietal+circuit+during+tactile+angle+match+and+non-match+processing:+an+fMRI+study.">Tactile priming modulates the activation of the fronto-parietal circuit during tactile angle match and non-match processing: an fMRI study.</a> Frontiers in Human Neuroscience. 8, 926 (2014).</li><li>Yu, Y., Yang, J., Ejima, Y., Fukuyama, H., Wu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetric+Functional+Connectivity+of+the+Contra-+and+Ipsilateral+Secondary+Somatosensory+Cortex+during+Tactile+Object+Recognition.">Asymmetric Functional Connectivity of the Contra- and Ipsilateral Secondary Somatosensory Cortex during Tactile Object Recognition.</a> Frontiers in Human Neuroscience. 11, (2018).</li><li>Olczak, D., Sukumar, V., Pruszynski, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Edge+orientation+perception+during+active+touch.">Edge orientation perception during active touch.</a> Journal of Neurophysiology. 120 (5), 2423-2429 (2018).</li><li>Lederman, S. J., Taylor, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perception+of+interpolated+position+and+orientation+by+vision+and+active+touch.">Perception of interpolated position and orientation by vision and active touch.</a> Perception and Psychophysics. 6 (3), 153-159 (1969).</li><li>Peters, R. M., Staibano, P., Goldreich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+orientation+perception:+An+ideal+observer+analysis+of+human+psychophysical+performance+in+relation+to+macaque+area+3b+receptive+fields.">Tactile orientation perception: An ideal observer analysis of human psychophysical performance in relation to macaque area 3b receptive fields.</a> Journal of Neurophysiology. 114 (6), 3076-3096 (2015).</li><li>Bensmaia, S. J., Hsiao, S. S., Denchev, P. V., Killebrew, J. H., Craig, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+tactile+perception+of+stimulus+orientation.">The tactile perception of stimulus orientation.</a> Somatosensory and Motor Research. 25 (1), 49-59 (2008).</li><li>Morash, V., Pensky, A. E. C., Alfaro, A. U., McKerracher, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+haptic+spatial+abilities+in+the+blind.">A review of haptic spatial abilities in the blind.</a> Spatial Cognition and Computation. 12 (2-3), 83-95 (2012).</li><li>Wang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+angle+discriminability+improvement:+roles+of+training+time+intervals+and+different+types+of+training+tasks.">Tactile angle discriminability improvement: roles of training time intervals and different types of training tasks.</a> Journal of Neurophysiology. 122 (5), 1918-1927 (2019).</li><li>Yang, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+priming+modulates+the+activation+of+the+fronto-parietal+circuit+during+tactile+angle+match+and+non-match+processing:+an+fMRI+study.">Tactile priming modulates the activation of the fronto-parietal circuit during tactile angle match and non-match processing: an fMRI study.</a> Frontiers in Human Neuroscience. 8, 926 (2014).</li><li>Peters, R. M., Hackeman, E., Goldreich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diminutive+Digits+Discern+Delicate+Details:+Fingertip+Size+and+the+Sex+Difference+in+Tactile+Spatial+Acuity.">Diminutive Digits Discern Delicate Details: Fingertip Size and the Sex Difference in Tactile Spatial Acuity.</a> Journal of Neuroscience. 29 (50), 15756-15761 (2009).</li><li>Sathian, K., Zangaladze, A., Green, J., Vitek, J. L., DeLong, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tactile+spatial+acuity+and+roughness+discrimination:+Impairments+due+to+aging+and+Parkinson's+disease.">Tactile spatial acuity and roughness discrimination: Impairments due to aging and Parkinson's disease.</a> Neurology. 49 (1), 168-177 (1997).</li><li>Hoehler, F. 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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:
<p ...

Watch this Scientific Journal Video about Tactile Semiautomatic Passive-Finger Angle Stimulator TSPAS at JoVE.com

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 ...

Our method provides a new approach to measuring tactile spatial acuity. Our semiautomated system is easy to operate and can be used to control movement, speed, distance and contact duration. To prepare tactile angle stimuli, use a milling machine to cut an acrylic sheet into an 8 milliliter long, 1.5 millimeter wide, 1 millimeter high polyline with two equal lines symmetrically distributed along an imaginary bisector.And a 40 milliliter long, 40 millimeter wide, 3 millimeter high square base. Glue the polyline to the center of the square base. Degrade a 2-D raised tactile angle stimulus.Make pieces with angle sizes ranging from 50 to 70 degrees in 2-degree increments. And make up to 20 pairs of discriminated angles including 20 identical reference angles and 10 pairs of identical comparison angles with measured accuracies of plus or minus 0.2 degrees. Before beginning an experiment in the data editing software, set the motion type of the device to Increment Model.The motion distance to 80 millimeters, the motion speed to 20 millimeters per second. The motion function to single and the axis as ID equals 0. To set the electronic slide movement, distance and speed parameters, respectively.When the software parameters have been set, have the subject sit at a table with the apparatus and place a blindfold on the subject. Instruct the subject to lightly place the right index finger at the opening of the hand plate. Next, clamp a pair of angles, including the reference angle and the comparison angle, onto the slide.Instruct the subject to report which of the angles is larger as perceived by touch, and click the button. The pair of angles will slide passively across the index fingers at a speed of 20 millimeters per second for 80 millimeters. If the subject cannot identify which angle is larger, they can indicate that the angles are the same.Register the answer of the subject as the response data. Then, replace the angles and repeat the presentation in the same manner 10 times, recording the subjects response after each analysis. To avoid uncomfortable sensations on the index finger, have the subject take a three-minute break after each series of 20 trials.To apply the logistic curve to describe the angle discrimination threshold, the three alternative force-choice result must be expressed as a frequency distribution. In this coordinate, a logistic curve could be fitted by the least-square method. And the angle discrimination threshold was defined as half of the difference between the angle at accuracy rates of 25 and 75%So this technique may provide a new approach for the tactile interplay of sensory and high-order processing.

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Behavior

2.8K Görüntüleme.  Okayama University. Our method provides a new approach to measuring tactile spatial acuity. Our semiautomated system is easy to operate and can be used to control movement, speed, distance and contact duration. To prepare tactile angle stimuli, use a milling machine to cut an acrylic sheet into an 8 milliliter long, 1.5 millimeter wide, 1 millimeter high polyline with two equal lines symmetrically distributed along an imaginary bisector.And a 40 milliliter long, 40 millimeter wide, 3 millimeter high squar...