LRH was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. SD was partly supported from the NSERC CREATE program.

All of the experiments were approved by the York Ethics board and all participants signed informed consent forms. The experiments were performed in accordance with the Treaty of Helsinki.
1. Stimuli
<ol>
	<li>Tactile Detection Stimulus
	<ol>
		<li>Use a tactor (1.17&#34; diameter and 0.30&#34; thick) to deliver tactile stimuli of 250 Hz vibration for 100 msec. Using a purpose-built tactor provides a linear relationship between the amount of travel and the voltage applied.</li>
		<li>Control ...

<ol>
	<li>von Be&#769;ke&#769;sy, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Sensory Inhibition. , (1967).</li><li>Uttal, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibitory+interaction+of+responses+to+electrical+stimuli+in+the+fingers.">Inhibitory interaction of responses to electrical stimuli in the fingers.</a> J. Comp. Physiol. Psych. 53 (1), 47-51 (1960).</li><li>Schmid, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+aspects+of+cutaneous+interaction+with+two-point+electrical+stimulation.">Temporal aspects of cutaneous interaction with two-point electrical stimulation.</a> J. Exp. Psychol. Gen. 61, 400-409 (1961).</li><li>Abramsky, O., Carmon, A., Bentontt, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Masking+of+and+by+tactile+pressure+stimuli.">Masking of and by tactile pressure stimuli.</a> Percept. Psychophys. 10 (5), 353-355 (1971).</li><li>Sherrick, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+double+simultaneous+stimulation+of+the+skin.">Effects of double simultaneous stimulation of the skin.</a> Am. J. Psychol. 77, 42-53 (1964).</li><li>Gilson, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrotactile+masking:+effects+of+multiple+maskers.">Vibrotactile masking: effects of multiple maskers.</a> Percept. Psychophys. 95 (4), 2213-2220 (1969).</li><li>Braun, C., Hess, H., Burkhardt, M., W&#252;hle, A., Preissl, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+right+hand+knows+what+the+left+hand+is+feeling.">The right hand knows what the left hand is feeling.</a> Exp. Brain. Res. 162 (3), 366-373 (2005).</li><li>Tam&#232;, L., Farn&#232;, A., Pavani, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+coding+of+touch+at+the+fingers:+Insights+from+double+simultaneous+stimulation+within+and+between.">Spatial coding of touch at the fingers: Insights from double simultaneous stimulation within and between.</a> Neurosci. Lett. 487 (1), 78-82 (2011).</li><li>Tam&#232;, L., Moles, A., Holmes, N. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Within+but+not+between+hands+interactions+in+vibrotactile+detection+thresholds+reflect+somatosensory+receptive+field+organization.">Within but not between hands interactions in vibrotactile detection thresholds reflect somatosensory receptive field organization.</a> Front. Psychol. 5, 1-9 (2014).</li><li>Harris, J. A., Diamond, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ipsilateral+and+contralateral+transfer+of+tactile+learning.">Ipsilateral and contralateral transfer of tactile learning.</a> Neuroreport. 11 (2), 263-266 (2000).</li><li>Fechner, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elemente der Psychophysik . , (1860).</li><li>Watson, A., Pelli, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=QUEST-A+Bayesian+adaptive+psychophysical+method.">QUEST-A Bayesian adaptive psychophysical method.</a> Percept. Psychophys. 33, 113-120 (1983).</li><li>D'Amour, S., Harris, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contralateral+tactile+masking+between+forearms.">Contralateral tactile masking between forearms.</a> Exp. Brain. Res. 232 (3), 821-826 (2014).</li><li>D'Amour, S., Harris, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrotactile+masking+through+the+body.">Vibrotactile masking through the body.</a> Exp. Brain. Res. 232 (9), 2859-2863 (2014).</li><li>Gescheider, G. A., Herman, D. D., Phillips, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Criterion+shifts+in+the+measurement+of+tactile+masking.">Criterion shifts in the measurement of tactile masking.</a> Percept. Psychophys. 8, 433-436 (1970).</li><li>Iwamura, Y., Tanaka, M., Iriki, A., Taoka, M., Toda, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Processing+of+tactile+and+kinesthetic+signals+from+bilateral+sides+of+the+body+in+the+postcentral+gyrus+of+awake+monkeys.">Processing of tactile and kinesthetic signals from bilateral sides of the body in the postcentral gyrus of awake monkeys.</a> Behav. Brain. Res. 135 (1-2), 185-190 (2002).</li><li>Killackey, H. P., Gould, H. J., Cusick, C. G., Pons, T. P., Kaas, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relation+of+corpus+callosum+connections+to+architectonic+fields+and+body+surface+maps+in+sensorimotor+cortex+of+new+and+old+world+monkeys.">The relation of corpus callosum connections to architectonic fields and body surface maps in sensorimotor cortex of new and old world monkeys.</a> J. Comp. Neurol. 219 (4), 384-419 (1983).</li><li>Reed, J. L., Qi, H. X., Kaas, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatiotemporal+properties+of+neuron+response+suppression+in+owl+monkey+primary+somatosensory+cortex+when+stimuli+are+presented+to+both+hands.">Spatiotemporal properties of neuron response suppression in owl monkey primary somatosensory cortex when stimuli are presented to both hands.</a> J. Neurosci. 31 (10), 3589-3601 (2011).</li><li>Hlushchuk, Y., Hari, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+suppression+of+ipsilateral+primary+somatosensory+cortex+during+tactile+finger+stimulation.">Transient suppression of ipsilateral primary somatosensory cortex during tactile finger stimulation.</a> J. Neurosci. 26 (21), 5819-5824 (2006).</li><li>Nihashi, T., 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=Contralateral+and+ipsilateral+responses+in+primary+somatosensory+cortex+following+electrical+median+nerve+stimulation--an+fMRI+study.">Contralateral and ipsilateral responses in primary somatosensory cortex following electrical median nerve stimulation--an fMRI study.</a> Clin. Neurophysiol. 116 (4), 842-848 (2005).</li><li>Tam&#232;, L., 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=The+contribution+of+primary+and+secondary+somatosensory+cortices+to+the+representation+of+body+parts+and+body+sides:+an+fMRI+adaptation+study.">The contribution of primary and secondary somatosensory cortices to the representation of body parts and body sides: an fMRI adaptation study.</a> J. Cognitive. Neurosci. 24 (12), 2306-2320 (2012).</li><li>Tam&#232;, L., Farn&#232;, A., Pavani, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vision+of+the+body+and+the+differentiation+of+perceived+body+side+in+touch.">Vision of the body and the differentiation of perceived body side in touch.</a> Cortex. 49 (5), 1340-1351 (2013).</li><li>Tam&#232;, L., Pavani, F., Papadelis, C., Farn&#232;, A., Braun, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+integration+of+bilateral+touch+in+the+primary+somatosensory+cortex.">Early integration of bilateral touch in the primary somatosensory cortex.</a> Hum. Brain. Mapp. 36 (4), 1506-1523 (2015).</li><li>Gilson, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrotactile+masking:+Some+spatial+and+temporal+aspects.">Vibrotactile masking: Some spatial and temporal aspects.</a> Percept. Psychophys. 5 (3), 176-180 (1969).</li><li>Alliusi, E., Morgan, B., Hawkes, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Masking+of+cutaneous+sensations+in+multiple+stimulus+presentations.">Masking of cutaneous sensations in multiple stimulus presentations.</a> Percept. Motor. Skill. 20, 39-45 (1965).</li><li>Geldard, F. A., Sherrick, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+cutaneous+stimulation:+The+discrimination+of+vibratory+patterns.">Multiple cutaneous stimulation: The discrimination of vibratory patterns.</a> J. Acoust. Soc. Am. 37, 797-801 (1965).</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=Vibrotactile+loudness+addition.">Vibrotactile loudness addition.</a> Percept. Psychophys. 1, 185-190 (1966).</li></ol>

The authors declare that they have no competing financial interests.

Here, a detailed protocol for contralateral tactile masking is described and previously published results using the technique to test tactile detection thresholds are shown. The advantage of this method is that thresholds are measured using a psychophysically rigorous technique. The two-alternative forced choice (2AFC) procedure is relatively insensitive to response bias and therefore from attentional effects. The adaptive staircase procedure for honing in on the actual threshold value is very efficient as most of the da...

Tactile masking is where a tactile stimulus at one location on the body alters the perception of a touch at another location. This is a technique pioneered by von Bekesy1to reveal location interactions, especially lateral inhibition, between areas of skin that are adjacent on the body surface. While tactile masking has been studied extensively over the years, research has mainly investigated ipsilateral tactile masking using electrical stimulation2,3, pressure4, and vibrotactile stimulation5,6. In contrast, few studies have looked at contralateral tactile masking in which the masking and probe sites may be far removed. Long-range tactile masking effects have been shown between mirror-symmetric points on the hand and arm5,7-9but these studies have been largely restricted to looking at the hands and fingers7,10, with more extensive parts of the whole body being largely ignored. A goal of such long-range masking experiments is to indicate how components of the body&#39;s representation in the brain may be functionally linked. Here, the phenomenon of long-range tactile masking is explored by investigating how vibration applied to one forearm might affect tactile sensitivity thresholds on the opposite forearm. Threshold refers to the minimum stimulus that is needed to detect a stimulus. We define this as the intensity at which the stimulus is detected 75% of the time. We used a tactile masking technique in which tactile sensitivity (the reciprocal of threshold) on one forearm is measured in the presence of a vibrating stimulus (the mask) on another part of the body. Effective masking is revealed by an increase in the detection threshold i.e., a reduction in sensitivity. The technique can be used in conjunction with other manipulations such as varying limb position or movement to explore their effects on the effectiveness of masking.
Here we used vibrotactile stimuli as the masking stimulus. The advantage of this is that the frequency, and hence the receptor type that it stimulates can be controlled. The technique could be extended to look at pain using electrical stimuli as the probe or mask or both. Also, any site can be used as the masking site allowing the investigation of acupuncture sites for example.

<table border="0" cellpadding="0" cellspacing="0" width="673">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">C-2 tactor</td>
			<td style="width:127px;">ATAC Technology; Engineering Acoustics, Inc.</td>
			<td style="width:164px;"></td>
			<td style="width:167px;">http://www.atactech.com/PR_tactors.html</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Magic Wand</td>
			<td style="width:127px;">Hitachi</td>
			<td style="width:164px;"></td>
			<td style="width:167px;">http://magicwandoriginal.com/magic-wand-original/</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:216px;">FC5 Foot Pedals</td>
			<td style="width:127px;">Yamaha Corporation</td>
			<td style="width:164px;"></td>
			<td style="width:167px;">http://ca.yamaha.com/en/products/music-production/accessories/footpedals/fc5/?mode=model</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">MATLAB</td>
			<td style="width:127px;">The Mathworks, Inc.</td>
			<td style="width:164px;"></td>
			<td style="width:167px;">http://www.mathworks.com/products/matlab/</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Velcro</td>
			<td style="width:127px;">Velcro Industries B.V.</td>
			<td style="width:164px;"></td>
			<td>http://www.velcro.com/</td>
		</tr>
	</tbody>
</table>

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.

Analyses of the data was reported in13. Tactile sensitivity (expressed relative to the thresholds measured in the control condition) on the forearm was significantly reduced (thresholds were significantly increased) when vibrotactile masking stimulation was applied to the opposite arm (Figure 2A), demonstrating a contralateral masking effect between forearms. The effect depended on the position of the masking stimulus on the masking arm, with the largest effect...

Watch this Scientific Journal Video about Testing Tactile Masking between the Forearms at JoVE.com

Testing Tactile Masking between the Forearms

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, ...

The overall goal of this psycho-physical experiment is to show how touching one place can affect the perception of a touch at another location. This technique of long-range tactile masking can make important contributions to the field of perception. For example, it can tell us how the brain represents the body's surface.An advantage of this technique is that it is non-invasive, and yet, even though it's a perceptual measure, it can tell us information about how the brain is wired up. Demonstrating this technique will be Sarah. She's a graduate student in my lab, and she developed the techniques that we're demonstrating today as part of her master's thesis.Begin by preparing the tactile detection stimulus system that will be used during this experiment. Use a tactor with a 1.7 inch diameter and 0.30 inch thickness to deliver tactile stimuli with 250 hertz vibration for 100 milliseconds. Also use a 64 bit stereo sound card to control the tactile stimulus delivery.To do this, first connect a stereo audio amplifier to the sound card that will drive the tactor as a loud speaker. Next, connect the tactor to one of the outputs of the amplifier, such as the left speaker out. Then, connect the second channel to a loudspeaker to provide auditory signals.In the computer code that is controlling the experiment, generate the waveform that will be used to vibrate the tactor, and another waveform for the auditory signal. Put each of these two waveforms into a two-dimensional array. Attach the tactor to a strap with a mechanical base fastener so that it can be placed on the participant.For the masking stimulus, use an electric handheld vibrator with a four centimeter diameter, with 83 hertz vibration when set on low. Select the sites where the stimulus is to be applied based on the areas where masking is to be tested. After the tactile detection stimulus system is ready, arrange the computer and other equipment for the experiment on a desk with a chair in front of it for the experimenter.Then, set up a table on which participants will rest their left arm, where tactile stimuli will be applied, and place a chair to the right side of the table. Also place an armrest stand next to the chair, on which the participants rest their right elbow. Add cushioning to the table, and an armrest for comfort.Next, place the loudspeaker on a mechanically isolated surface. Arrange foot pedals that are connected to the left and right buttons of a computer mouse so that the participant's feet can rest comfortably on them. Be sure to make a list of the order in which the conditions will be run, and use this list during the experiment to determine where to hold the masking stimulus for each block.Enter the number of trials into the computer program code and ensure that each block is no longer than 10 minutes to maintain the participant's attention. Program a two alternative forced choice tactile detection task in which stimulus intensity is controlled with Bayesian adaptive psycho-physical staircase psychometric procedure. For each trial, present two one second intervals, marked by three beeps, with a tactile stimulus presented in the middle of one of the intervals.Have the participant indicate in which interval the stimulus was presented by means of the foot pedals. The computer scores the response as correct or wrong, and the adaptive staircase chooses the next value to be presented accordingly. This determines a threshold value for detecting vibration at the test site.Prior to the experiment, obtain written informed consent from the participant. Then, seat them in the chair with their feet resting comfortably on the response foot pedals and explain the experimental procedure. Measure and record the length of the particpant's dorsal surface of the left forearm.Then, apply the strap so the tactor is positioned in the middle of the arm, halfway between the inner angle of the elbow and the wrist crease. Wrap a tensor bandage loosely around the arm several times to hold the tactor in place. Now, instruct the participant to place their right elbow on the arm rest, and rest their left arm on the table.Then, blindfold the participant to prevent them from looking at the stimulus or the masking location, and instruct them to look straight ahead throughout the experiment. Start with a block of 20 practice trials without the masking stimulus, in order to familiarize the participant with the tactile detection task, and to allow them to become familiar with the stimuli. Following the practice run, first ensure that the arms and the masking stimulus are in the correct positions prior to each experimental block.Run the blocks of conditions in a random, counter balanced order. For each condition, refer to the list of conditions made earlier, and cross off each condition as it is run. Be sure to hold the masking stimulus throughout each block of data collection trials, maintaining approximately constant pressure.Run the experimental program with the set number of trials as previously selected, and introduce a two minute rest period after each short trial block. After a given trial block is completed, select the next site for the masking stimulus, and run the program again, and repeat this until all trials are completed. In this figure, the elevation and threshold is plotted as a function of the position of the mask.Tactile sensitivity on the forearm was significantly reduced when vibro-tactile masking stimulation was applied to the opposite arm, demonstrating a contralateral masking effect between forearms. Here, these data show that posture also plays a role on the effectiveness of masking. The masking effect was considerably stronger when the arms were touching, compared to when they were parallel.Once mastered, this technique can be done in about half an hour if it's performed properly. Although it's necessary to repeat the experiment on at least ten participants to obtain statistical validity. While attempting this procedure, it's important to remember to maintain the pressure at the masking site and to keep the participant's attention at a location that does not vary, usually straight ahead.Following the procedure, variations can be performed in order to answer additional questions, such as the dependency of these effects on the characteristics of the masking stimulus. After its development, this technique has paved the way for researchers in the field of tactile research to explore whether this phenomenon might generalize to more than just touch sensations, but also pain. After watching this video, you should have a good understanding of how to test the influence of remote tactile stimulus on touch perception at a specific site.

testing-tactile-masking-between-the-forearms

Research

JoVE Journal

Behavior

6.3K Görüntüleme.  York University. The overall goal of this psycho-physical experiment is to show how touching one place can affect the perception of a touch at another location. This technique of long-range tactile masking can make important contributions to the field of perception. For example, it can tell us how the brain represents the body's surface.An advantage of this technique is that it is non-invasive, and yet, even though it's a perceptual measure, it can tell us information about how the brain is wired up. D...