Name: testing tactile masking between the forearms
Uploaded: 2016-02-10T15:00:00.000+00:00
Duration: 8 min 5 s
Description: Watch this Scientific Journal Video about Testing Tactile Masking between the Forearms at JoVE.com

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 tactile stimulus delivery with a 64 bit sound card.
		<ol>
			<li>To drive the tactor, treat it as a loudspeaker. Connect a stereo audio amplifier to a 64-bit computer stereo sound card. Connect the tactor to one of the outputs of the amplifier (e.g., the &#39;left speaker out&#39;). Connect the second channel (e.g., the &#39;right speaker out&#39;) of the amplifier to a regular loudspeaker to provide auditory signals to the participant.</li>
			<li>In the computer code that is controlling the experiment, generate the waveform that will be used to vibrate the tactor (e.g., a 250 Hz sinewave of duration 100 msec), and another waveform for the auditory signal (e.g., a 3,000 Hz sinewave with a duration of 100 msec). See Example Code 1 in the Supplemental Code File.</li>
			<li>Put each of these two waveforms into a two-dimensional array. For the tactor array put the signal in the first dimension and set the second dimension to all zeros. For the sound array put the signal in the second dimension and set the first to all zeros. Play the appropriate array to the soundcard at the appropriate point in the program. See Example Code 1 in the Supplemental Code File for a demonstration of how this is done.</li>
		</ol>
		</li>
		<li>Attach the tactor to a strap with a mechanical-based fastening product.</li>
	</ol>
	</li>
	<li>Masking Stimulus
	<ol>
		<li>Provide the masking stimulus by an electric, hand-held vibrator (4 cm diameter; 83 Hz when set on &#34;low&#34;).</li>
		<li>Based on the areas where masking is to be tested, select the sites where the masking stimulus is to be applied.</li>
	</ol>
	</li>
</ol>
2. Experimental Setup and Design
<ol>
	<li>Arrange the computer and equipment on a desk, with a chair in front of it, for the experimenter.</li>
	<li>Set up a table on which participants rest their left (test) arm. Place a chair to the right side of the table. Put an armrest stand next to the chair on which the participants rest their right (masking arm) elbow. Add cushioning to the table and armrest for comfort.</li>
	<li>Arrange a loudspeaker on a mechanically isolated surface. Arrange foot pedals (connected to the left and right buttons of a computer mouse) so that the participant&#39;s feet will rest comfortably on them (Figure 1).</li>
	<li>Choose the parameters of the study, including the appropriate number of trials required to obtain a reliable estimate of the threshold (typically, between 40-50 trials) and the number of blocks into which the experiment is to be divided (e.g., two blocks of 20-25 trials per condition).</li>
	<li>Make a list of the order in which the conditions will be run. Use this list to determine where to hold the masking stimulus for each block.</li>
	<li>Enter the number of trials directly into the computer program code (e.g., ntrials = 25; See Supplemental Code File). Ensure that each block is no longer than 10 min to maintain attention.</li>
	<li>Program a two-alternative-forced-choice tactile detection task11in which stimulus intensity is controlled with a Bayesian adaptive psychophysical staircase psychometric procedure12.
	<ol>
		<li>For each trial, present two 1 sec intervals, marked by three beeps (5 kHz, 3 kHz and 5 kHz, duration 100 msec), with the 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 foot pedals (left for first, right for second). See Example Code 2, which shows how the intervals are run and scored. 
		Note: The computer scores the response as &#34;correct&#34; or &#34;wrong&#34; and the adaptive staircase chooses the next value to be presented accordingly. 
		Note: This method determines a threshold value for detecting the vibration at the test site.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/53733/53733fig1.jpg" /> 
Figure 1. Experimental Design. This figure shows the set up of the experiment and the materials used. See text for details.
3. Experimental Procedure
<ol>
	<li>Obtain written informed consent. Seat the participant in the chair with their feet resting comfortably on the response foot pedals and explain the experimental procedure.</li>
	<li>Measure and record the length of the dorsal surface of the left forearm. 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.</li>
	<li>Wrap a tensor bandage loosely around the arm several times to hold the tactor in place.</li>
	<li>Instruct participants to place their left arm on the table and rest their right elbow on the armrest. Blindfold the participant to prevent them looking at the stimulus or masking location and instruct them to look straight ahead throughout the experiment.</li>
	<li>Start with a block of 20 practice trials (without the masking stimulus) in order to familiarize participants with the tactile detection task and to allow them to become familiar with the tactile stimuli.</li>
	<li>Following the practice trials, begin the experiment, running the blocks of conditions in a random, counterbalanced order. Before beginning each block, ensure that the arms and the masking stimulus are in the correct positions.
	<ol>
		<li>For each condition, hold the masking stimulus on the chosen site, referring to the list of conditions made earlier. Cross off each condition as it is run. Hold the masking stimulus throughout each block of data collection trials maintaining approximately constant pressure. The masking stimulus can be applied through thin clothing.</li>
		<li>Run the experimental program which will run through a set number of trials as previously selected. Introduce a 2 min rest period after each short block of trials. After a given block of trials is completed, select the next site for the masking stimulus and run the program again. Repeat until all trials are completed.</li>
	</ol>
	</li>
</ol>
4. Data Analysis
<ol>
	<li>To visualize and confirm the estimate of the threshold value returned by the adaptive staircase program12, fit the participants&#39; data with a cumulative Gaussian The formula for a cumulative Gaussian (sigmoid) that goes from 50% (chance level - equal number of 0s - wrong and 1&#39;s- correct) to 100% (all 1&#39;s, all correct) is: 
	probability of a correct response = 0.5 + 0.5/(1+exp(-(x-x0)/std)) 
	where x is the intensity value tested, x0 is the 75% threshold value, and std is the standard deviation of the estimate. This formula can be fitted to the data using any curve-fitting software and the resulting x0 value compared to the adaptive staircase value.
	<ol>
		<li>Ensure that the curve goes between 50% (chance performance) and 100%. Conduct statistical analyses (e.g., t-tests or ANOVAs) on the 75% threshold values obtained under each condition of the experiment (e.g., between different masking sites) to determine if there are any differences between the conditions tested.</li>
	</ol>
	</li>
	<li>In order to identify outliers, calculate the mean and the standard deviation for a given condition. Compare each participant&#39;s score with the mean and if an individual score is more than 2 standard deviation from that mean then regard this score as an outlier and remove it from the analysis. Alternative criteria may be used if desired.</li>
	<li>To standardize the values of the intensity of the tactors (which are in in arbitrary units), convert them to decibels relative to the control thresholds (measured when the masking stimulus is applied to the control site, e.g., the shoulder). Use this formula: 
	dB = 10 x log10 (threshold value/control threshold value).</li>
</ol>

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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 data are collected with stimulus intensities close to the threshold level. Blindfolding the participant and having them look straight ahead throughput the data collection period further reduced attentional effects.
It is technically very demanding to measure the actual pressure applied by a tactor. It is not sufficient to calibrate the device beforehand because the pressure exerted will also depend on how tightly the tactor is bound to the skin surface. Thus we are only able to make statements about changes in thresholds rather than the absolute values. Since in this experiment we are only looking for changes brought about by the masking stimulus, this is not a concern in this design.
By interleaving relatively short blocks (about 10 min) for each condition (i.e., each position of the masking stimulus) and presenting them in a sequence that was counterbalanced between participants the alertness of the participant is maintained.
Contralateral masking can be useful for exploring the representation of the body in the brain by revealing details of which parts are functionally connected to others. This technique provides behavioural5,7,8,13-15 evidence to support neurophysiological16-18 and neuroimaging data19-23 that suggest that the integration of somatosensory inputs from the two sides of the body occurs in a somatotopic representation. In these experiments, the effect of arm location was briefly examined by comparing masking when the hands were touching or parallel. Though a difference was found, it cannot be concluded whether it is caused from actual skin contact or arm position. In a set of new experiments, we have taken these methods and tested a variety of different arm positions of both the test and masking arms. These findings will help address whether long-range masking effects occur before or after postural information has been added.
The technique is extremely flexible and can be used to investigate any manner of interactions between different parts of the somatosensory system. For example, the frequency content of masking or testing stimulation can be varied to optimally stimulate rapidly adapting or slowly adapting sub-systems. A potential limitation of these methods is the tactile stimuli used. Using different detection and masking stimuli (such as size, frequency, duration, etc.) might reveal different results especially when measuring the spatial tuning of the masking effect. A smaller masking stimulus would allow for better precision and allow for more accurate measurements of specific areas. For future applications, this protocol could be modified by testing the masking effect using a wide range of tactile stimuli.
Research has typically concentrated on studying masking and tactile perception on the hands and fingers with relatively few studies examining the whole body14,24-27. Future directions could include testing contralateral masking on more extensive areas of the body, which might reveal unexpected connections between other body parts or within a limb that could shed light on how the three-dimensional body is represented within the brain.

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><tbody><tr><td>C-2 tactor</td><td>ATAC Technology; Engineering Acoustics, Inc.</td><td></td><td>http://www.atactech.com/PR_tactors.html</td></tr><tr><td>Magic Wand</td><td>Hitachi</td><td></td><td>http://magicwandoriginal.com/magic-wand-original/</td></tr><tr><td>FC5 Foot Pedals</td><td>Yamaha Corporation</td><td></td><td>http://ca.yamaha.com/en/products/music-production/accessories/footpedals/fc5/?mode=model</td></tr><tr><td>MATLAB</td><td>The Mathworks, Inc.</td><td></td><td>http://www.mathworks.com/products/matlab/</td></tr><tr><td>Velcro</td><td>Velcro Industries B.V.</td><td></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 occurring when the mask and test sites corresponded. Figure 2B shows 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 (3.3 dB compared with 0.52 dB).
<img alt="Figure 1" src="/files/ftp_upload/53733/53733fig2.jpg" /> 
Figure 2. Typical data obtained using this technique. (A) The elevation in threshold is plotted as a function of the position of the mask (shown as blue arrows in the cartoon above the graph). (B) The elevation in threshold at the probe site on the left arm caused by a masking stimulus on the corresponding site on the right arm depends on whether the arms are touching or parallel. All data are expressed in dB relative the thresholds obtain with vibration applied to a control site on the shoulder (green arrow). Standard errors are shown. N = 15. Data redrawn from D&#39;Amour and Harris, 2014.
Supplemental Code File 1. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53733/SUPPLEMENTAL_CODE_FILE.docx" target="_blank">(Please click here to download this file.)</a>

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, ...

testing-tactile-masking-between-the-forearms

Nanyang Technological University

Research

JoVE Journal

Behavior

6.3K Views.  York University. 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. 

Video: Testing Tactile Masking between the Forearms

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 ...

Creating Virtual-hand and Virtual-face Illusions to Investigate Self-representation

Studies investigating how people represent themselves and their own body often use variants of &#34;ownership illusions&#34;, such as the traditional rubber-hand illusion or the more recently discovered enfacement illusion. However, these examples require rather artificial experimental setups, in which the artificial effector needs to be stroked in synchrony with the participants&#39; real hand or face&#8212;a situation in which participants have no control over the stroking or the movements of their real or artificial effector. Here, we describe a technique to establish ownership illusions in a setup that is more realistic, more intuitive, and of presumably higher ecological validity. It allows creating the virtual-hand illusion by having participants control the movements of a virtual hand presented on a screen or in virtual space in front of them. If the virtual hand moves in synchrony with the participants&#39; own real hand, they tend to perceive the virtual hand as part of their own body. The technique also creates the virtual-face illusion by having participants control the movements of a virtual face in front of them, again with the effect that they tend to perceive the face as their own if it moves in synchrony with their real face. Studying the circumstances that illusions of this sort can be created, increased, or reduced provides important information about how people create and maintain representations of themselves.

Here, we describe virtual-hand and virtual-face illusion paradigms that can be used to study body-related self-perception/-representation. They have already been used in various studies to demonstrate that, under specific conditions, a virtual hand or face can be incorporated into one&#39;s body representation, suggesting that body representations are rather flexible.

Studies investigating how people represent themselves and their own body often use variants of &#34;ownership illusions&#34;, such as the traditional ...

A Simple Non-invasive Method for Temporary Knockdown of Upper Limb Proprioception

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are needed for clinical diagnosis of impairment, and to measure outcomes of proprioceptive training. The purpose of this simple, non-invasive method is to temporarily knockdown upper limb proprioception in healthy adults, to an extent that would be useful in the development and testing of upper limb proprioception measures. Knockdown models have two main advantages over studying humans with impaired proprioception: participant availability and the ability to control the extent of impairment across participants. Current published methods of temporary proprioception knockdown of the upper limb, such as ischemic nerve blocks and cryotherapy, are invasive, impractical, or uncomfortable for the participant. Here, vibration over the ulnar groove was used to reduce upper limb proprioception. High frequency vibration may reduce proprioceptive acuity by inhibiting pacinian corpuscle-induced input. The effect of vibration used in this protocol was confirmed using two quantitative measures. This method was simple to administer, comfortable for participants, and practical.

The goal of this protocol is to demonstrate a practical method to temporarily interfere with proprioception in the upper limb of healthy humans.

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are ...

Using Facial Electromyography to Assess Facial Muscle Reactions to Experienced and Observed Affective Touch in Humans

"Affective" touch is believed to be processed in a manner distinct from discriminatory touch and to involve activation of C-tactile (CT) afferent fibers. Touch that optimally activates CT fibers is consistently rated as hedonically pleasant. Patient groups with impaired social-emotional functioning also show disordered affective touch ratings. However, relying on self-reported ratings of touch has many limitations, including recall bias and communication barriers. Here, we describe a methodological approach to study affective responses to touch via facial electromyography (EMG) that circumvents the reliance on self-report ratings. Facial EMG is an objective, quantitative, and non-invasive method to measure facial muscle activity indicative of affective responses. Responses can be assessed across healthy and patient populations without the need for verbal communication. Here, we provide two separate datasets demonstrating that CT-optimal and non-optimal touch elicit distinct facial muscle reactions. Moreover, facial EMG responses are consistent across stimulus modalities, e.g. tactile (experienced touch) and visual (observed touch). Finally, the temporal resolution of facial EMG can detect responses on timescales that supersede that of verbal reporting. Together, our data suggest that facial EMG is a suitable methodology for use in affective tactile research that can be used to supplement, or in some cases, supplant, existing measures.

We describe a protocol to assess facial muscle activity in response to experienced and observed tactile stimulation using facial electromyography.

"Affective" touch is believed to be processed in a manner distinct from discriminatory touch and to involve activation of C-tactile (CT) afferent fibers. ...

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 ...

A Tactile Automated Passive-Finger Stimulator (TAPS)

Although tactile spatial acuity tests are used in both neuroscience research and clinical assessment, few automated devices exist for delivering controlled spatially structured stimuli to the skin. Consequently, investigators often apply tactile stimuli manually. Manual stimulus application is time consuming, requires great care and concentration on the part of the investigator, and leaves many stimulus parameters uncontrolled. We describe here a computer-controlled tactile stimulus system, the Tactile Automated Passive-finger Stimulator (TAPS), that applies spatially structured stimuli to the skin, controlling for onset velocity, contact force, and contact duration. TAPS is a versatile, programmable system, capable of efficiently conducting a variety of psychophysical procedures. We describe the components of TAPS, and show how TAPS is used to administer a two-interval forced-choice tactile grating orientation test.
Corresponding Author: Daniel Goldreich

A Tactile Automated Passive-Finger Stimulator TAPS

We describe a computer-controlled device for investigating the sense of touch: the Tactile Automated Passive-finger Stimulator (TAPS). We describe the components of TAPS, and show how TAPS is used to administer a two-interval forced-choice tactile grating orientation test.

Although tactile spatial acuity tests are used in both neuroscience research and clinical assessment, few automated devices exist for delivering ...

Biology

A Standardized Method for Measurement of Elbow Kinesthesia

Proprioception is an important component of controlled movement. The threshold to detection of passive movement (TDPM) is a commonly used method for quantifying the proprioceptive submodality of kinesthesia in research settings. The TDPM paradigm has been found to be valid and reliable; however, the equipment and methods used for TDPM vary between studies. In particular, the research laboratory apparatuses for producing passive movement of an extremity are often custom designed by individual laboratories or inaccessible due to high cost. There is a need for a standardized, valid, and reliable method for measuring TDPM using readily available equipment. The purpose of this protocol is to provide a standardized method for measurement of TDPM at the elbow that is economical, easy to administer, and that produces quantitative results for measurement purposes in research-based settings. This method was tested on 20 healthy adults without neurological impairment, and eight adults with chronic stroke. The results obtained suggest this method is a reliable way to quantify elbow TDPM in healthy adults, and provides initial support for validity. Researchers seeking a balance between equipment affordability and measurement precision are most likely to find this protocol of benefit.

Here, we present a standardized method for measurement of elbow passive kinesthesia using the threshold to detection of passive movement (TDPM) that is appropriate for a research setting.

Proprioception is an important component of controlled movement. The threshold to detection of passive movement (TDPM) is a commonly used method for ...

Non-Invasive Modulation and Robotic Mapping of Motor Cortex in the Developing Brain

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries unique challenges in children. Similarly, transcranial direct current stimulation (tDCS) can improve motor learning in adults but has only recently been applied to children. The use of tDCS and emerging techniques like high&#8211;definition tDCS (HD-tDCS) require special methodological considerations in the developing brain. Robotic TMS motor mapping may confer unique advantages for mapping, particularly in the developing brain. Here, we aim to provide a practical, standardized approach for two integrated methods capable of simultaneously exploring motor cortex modulation and motor maps in children. First, we describe a protocol for robotic TMS motor mapping. Individualized, MRI-navigated 12x12 grids centered on the motor cortex guide a robot to administer single-pulse TMS. Mean motor evoked potential (MEP) amplitudes per grid point are used to generate 3D motor maps of individual hand muscles with outcomes including map area, volume, and center of gravity. Tools to measure safety and tolerability of both methods are also included. Second, we describe the application of both tDCS and HD-tDCS to modulate the motor cortex and motor learning. An experimental training paradigm and sample results are described. These methods will advance the application of non-invasive brain stimulation in children.

We demonstrate protocols for the modulation (tDCS, HD-tDCS) and mapping (robotic TMS) of the motor cortex in children.

Mapping the motor cortex with transcranial magnetic stimulation (TMS) has potential to interrogate motor cortex physiology and plasticity but carries ...

Neuroscience

Capturing Dynamic Finger Gesturing with High-resolution Surface Electromyography and Computer Vision

Finger gestures are a critical element in human communication, and as such, finger gesture recognition is widely studied as a human-computer interface for state-of-the-art prosthetics and optimized rehabilitation. Surface electromyography (sEMG), in conjunction with deep learning methods, is considered a promising method in this domain. However, current methods often rely on cumbersome recording setups and the identification of static hand positions, limiting their effectiveness in real-world applications. The protocol we report here presents an advanced approach combining a wearable surface EMG and finger&#160;tracking system to capture comprehensive data during dynamic hand movements. The method records muscle activity from soft printed electrode arrays (16 electrodes) placed on the forearm as subjects perform gestures in different hand positions and during movement. Visual instructions prompt subjects to perform specific gestures while EMG and finger positions are recorded. The integration of synchronized EMG recordings and finger tracking data enables comprehensive analysis of muscle activity patterns and corresponding gestures. The reported approach demonstrates the potential of combining EMG and visual tracking technologies as an important resource for developing intuitive and responsive gesture recognition systems with applications in prosthetics, rehabilitation, and interactive technologies. This protocol aims to guide researchers and practitioners, fostering further innovation and application of gesture recognition in dynamic and real-world scenarios.

The paper presents a comprehensive protocol for simultaneously recording hand-electromyography (EMG) and visual finger tracking during natural finger gesturing. The visual data is designed to serve as the ground truth for the development of accurate EMG-based computational models for finger gesture recognition.

Finger gestures are a critical element in human communication, and as such, finger gesture recognition is widely studied as a human-computer interface for ...

Bioengineering

Assessing Corticospinal Excitability During Goal-Directed Reaching Behavior

Reaching is a widely studied behavior in motor physiology and neuroscience research. While reaching has been examined using a variety of behavioral manipulations, there remain significant gaps in the understanding of the neural processes involved in reach planning, execution, and control. The novel approach described here combines a two-dimensional reaching task with transcranial magnetic stimulation (TMS) and concurrent electromyography (EMG) recording from multiple muscles. This method allows for the noninvasive detection of corticospinal activity at precise time points during the unfolding of reaching movements. The example task code includes a delayed response reaching task with two possible targets displayed &#177; 45&#176; off the midline. Single pulse TMS is delivered on the majority of task trials, either at the onset of the preparatory cue (baseline) or 100 ms prior to the imperative cue (delay). This sample design is suitable for investigating changes in corticospinal excitability during reach preparation. The sample code also includes a visuomotor perturbation (i.e., cursor rotation of &#177; 20&#176;) to investigate the effects of adaptation on corticospinal excitability during reach preparation. The task parameters and TMS delivery can be adjusted to address specific hypotheses about the state of the motor system during reaching behavior. In the initial implementation, motor evoked potentials (MEPs) were successfully elicited on 83% of TMS trials, and reach trajectories were recorded on all trials.

Reaching is a fundamental skill that allows humans to interact with the environment. Several studies have aimed to characterize reaching behavior using a variety of methodologies. This paper offers an open-source application of transcranial magnetic stimulation to assess the state of corticospinal excitability in humans during reaching task performance.

Reaching is a widely studied behavior in motor physiology and neuroscience research. While reaching has been examined using a variety of behavioral ...

Testing Tactile Masking between the Forearms

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