This work was supported by National Institute on Deafness and Other Communication Disorders Grants R21DC013915 and R01DC012502, the Natural Sciences and Engineering Research Council of Canada and the European Research Council under the European Community&#8217;s Seventh Framework Programme (FP7/2007-2013 Grant Agreement no. 339152).

The current experimental protocol follows the guidelines of ethical conduct according to the Yale University Human Investigation Committee.
1. Electroenchephalopgaphy (EEG) Preparation
<ol>
	<li>Measure head size to determine the appropriate EEG cap.</li>
	<li>Identify the location of the vertex by finding the mid-point between nasion and inion with a measuring tape.</li>
	<li>Place the EEG cap on the head using the pre-determined vertex as Cz. Examine Cz again after placing the cap by using a measuring tape as done in 1.2. Note that the EEG cap is equipped with electrode holders and the placement of the 64 electrodes (or holders) is based on a modified 10-20 system with pre-specified coordinates system based on Cz11. 
	Note: This representative application uses a 64 electrode configuration to assess scalp distribution changes and for source analysis. For simpler applications (event-related potential changes in amplitude and latency) using fewer electrodes are possible. There are two additional electrodes for ground in the EEG system used here. Those electrode holders are also included in the cap.</li>
	<li>Apply electrode gel in the electrode holders using a disposable syringe.</li>
	<li>Attach EEG electrodes (including ground electrodes) into the electrodes holders matching the labels of the electrodes and to the electrode holders on the electrode cap.</li>
	<li>Clean the skin surface with alcohol pads. 
	Note: For electrodes for detecting eye motion (electro-oculography), the skin locations are above and below the right eye (vertical eye motion), and lateral to the outer canthus of the both eyes (horizontal eye motion); for somatosensory stimulation the skin lateral to the oral angle is cleaned.</li>
	<li>Fill the four electro-oculography electrodes with the electrode gel and secure the electrodes with double-sided tape to the sites noted in 1.6.</li>
	<li>Secure all electrode cables using a Velcro strap. If required, tape the cables to participant&#39;s body or the other locations that do not introduce any additional electrical or mechanical noise.</li>
	<li>Position the participant in front of the monitor and the robot for somatosensory stimulation. Secure all electrode cables again as in 1.8.</li>
	<li>Connect the EEG and electro-oculography electrodes (including the ground electrodes) into the appropriate connecters (matching label and connecter shape) on the amplifier box of the EEG system.</li>
	<li>Check to see that the EEG signals are artifact free and that the offset value is in an acceptable range (&#60;50 &#181;V or smaller). If noisy signals or large offsets that are usually indicative of high impedance are found, correct those electrode signals by adding additional EEG gel and/or repositioning hair that is directly under the electrode.</li>
	<li>Insert the EEG-compatible earphones and confirm that the sound level is in a comfortable range based on subject report.</li>
</ol>
2. Somatosensory Stimulation
Note: The current protocol applies facial skin stretch for the purpose of somatosensory stimulation. The experimental setup with the EEG system is represented in Figure 1. The details of the somatosensory stimulation device have been described in the previous studies1,7,12-14. Briefly, two small plastic tabs (2 cm wide and 3 cm height) are attached with double-sided tape to the facial skin. The tabs are connected to the robotic device using string. The robot generates systematic skin stretch loads according to experimental designs. The setup protocol for ERP recording is as follows:
<ol>
	<li>Place the participant&#39;s head in the headrest in order to minimize head motion during stimulation. Remove carefully the electrode cables between the participant&#39;s head and headrest.</li>
	<li>Ask the participant to hold the safety switch for the robot.</li>
	<li>Attach plastic tabs to the target skin location using double-sided tape for somatosensory stimulation. For the representative results12,13, in which the target is the skin lateral to the oral angle, place the center of the tabs on the modiolus, a few mm lateral to the oral angle with the center of the tabs at approximately the same height of the oral angle.</li>
	<li>Adjust the configuration of the string, string supports and the robot in order to avoid EEG electrodes and cables.</li>
	<li>Apply a few facial skin stretches (one cycle sinusoid at 3 Hz with a maximum force of 4 N) to check for artifacts due to the stimulation (usually observed as relatively large amplitude and lower frequency compared with the electrophysiological response). If artifacts are observed in the EEG signals, go back to 2.4.</li>
</ol>
3. ERP Recording
<ol>
	<li>Explain the experimental task to the subject and provide practice trials (one block = 10 trials or less) to confirm if the subject understands the task clearly. 
	Note: The experimental task and stimulus presentation for ERP recording are preprogramed in software for stimulus presentation.
	<ol>
		<li>In the representative test with combined somatosensory and auditory stimulation12, apply the somatosensory stimulation associated with skin deformation to the skin lateral to the oral angle. The pattern of stretch is a one cycle sinusoid (3 Hz) with a maximum force of 4 N. A single synthesized speech utterance that is midway in a 10-step sound continuum between &#34;head&#34; and &#34;had&#34; is used for auditory stimulation.</li>
		<li>Present both stimulations separately or in combination. In the combined stimulation, test three onset timings (90 msec lead and lag, and simultaneous in somatosensory and auditory onsets: see Figure 3A).</li>
		<li>Randomize the presentation of five stimulations (somatosensory alone, auditory alone and three combined: lead, simult. and lag). Vary the inter-trial interval between 1,000 and 2,000 msec in order to avoid anticipation and habituation. The experimental task is to identify whether the presented speech sound, which is the sound that is acoustically intermediate between &#34;head&#34; and &#34;had&#39;, was &#34;head&#34; by pressing a key on a keyboard. In the somatosensory alone condition, in which there is no auditory stimulation, the participants are instructed to answer not &#34;head&#34;.</li>
		<li>Record participant judgments and the reaction time from the stimulus onset to the key press using the software for stimulus presentation. Ask the participant to gaze a fixation point on the display screen in order to reduce artifacts due to eye-movement.</li>
		<li>Remove the fixation point every 10 stimulations for a short break. (See also other example of task and stimulus presentation12,13)</li>
	</ol>
	</li>
	<li>Start the software for ERP recording at 512 Hz sampling, which also records the onset time of stimulation in the timeline of ERP data. Note that the time stamps of the stimulation, which also includes the information about the type of the stimulation, are sent for every stimulus from the software for stimulus presentation. The two programs (for ERP recording and for the stimulus presentation) are running on two separate PCs that are connected through a parallel port.</li>
	<li>Set the software for the somatosensory stimulation to the trigger-waiting mode and then start stimulus presentation by activating the software for stimulus presentation. Note that the software for the somatosensory stimulation is also running on a separate PC from the other two PCs. Record 100 ERPs per condition. 
	Note: A trigger signal for the somatosensory stimulation is received through an analog input device that is connected to a digital output device in the PC for sensory stimulation. Single somatosensory stimulation is produced per one trigger.</li>
</ol>

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The authors have nothing to disclose.

The studies reported here provide evidence that precisely controlled somatosensory stimulation that is produced by facial skin deformation induces cortical ERPs. Cutaneous afferents are known as a rich source of kinesthetic information3,4 in human limb movement5,6 and speech movement7,8,21. Stretching the facial skin in a manner that reflects the actual movement direction during speaking induces a kinesthetic sense similar to the corresponding movement. The current method combining precisely controlled skin stretch and ERP recordings can be used to investigate the neural basis of orofacial function during a wide range of speech behaviors.
Using mechanical stimulation and simultaneous EEG recording, it is important to monitor the ongoing signals for artifact. In particular, since the strings used to stretch the skin are located close to the EEG electrodes and cables, there is the possibility of electrical and motion artifacts being induced in the EEG signals. This artifact is distinguishable because of relatively large amplitude and lower frequency compared with the electrophysiological response. Before recording, the stimulation setup including the string configuration needs to be checked carefully to identify and eliminate any mechanical artifacts due to the stimulation. Although artifacts can be removed by post signal processing, such as filtering or independent component analysis22 similar to eye movement and blinking, cleaner signals are always more desirable.
The previous studies of somatosensory event-related potentials have mostly used brief somatosensory stimuli that were produced using mechanical23, electrical18 or laser nociceptive stimulation15. Somatosensory inputs arising from these kinds of stimulation are not associated with any particular articulatory motion in speech, and hence, they may not be suitable for investigating speech-related cortical processing. M&#246;tt&#246;nen, et al.17 had failed to show a change of magnetoenchalographic somatosensory potentials using simple lip tapping during listening to speech sounds. In contrast, deformation of the facial skin provides kinesthetic input similar to that which occurs in conjunction with speech articulatory motion21 and sensorimotor adaption7. These stimuli also interact with speech perceptual processing1,14. The somatosensory ERP from the current skin stretch perturbation is more suitable for the investigation of speech-related cortical processing than the other methods currently available for somatosensory stimulation. Several different characteristics were found between the current skin stretch stimulation and the previous methods. Further investigation including the source location is required.
Although deformation of the facial skin occurs to varying degrees during speech motion8, the skin lateral to the oral angle is densely innervated with cutaneous mechanoreceptors10,24 and may be predominantly responsible for the detection of skin stretch during speech. The skin at the corners of the mouth may be especially important for speech motor control and speech motor learning. The current approach is somewhat limited because the stretch of the skin can only be done in one direction and at one location per EEG session. Using a more complex skin deformation and evaluating multiple directions and/or multiple locations in one EEG session will provide further insight into the specific role of somatosensation in speech processing.
There are long-standing interests in speech communication studies concerning the nature of representations and processing in speech production and perception25-27. The discovery of mirror neurons28,29 reinforced the idea that motor functions are involved in speech perception. The involvement of the motor system (or the motor and premotor cortex) has also been investigated30-35 in the perception of speech sounds. Nevertheless, the link between speech production and perception is still poorly understood. Exploring possible somatosensory influences on speech perception can help us understand the neural bases of speech perception and production, and whether they overlap or link. The current technique for modulating somatosensory function has provided a new tool to investigate this important area of inquiry. The current technique has the additional advantage that it can be used in investigations of somatosensory function more generally and how it interacts with other sensory modalities in neural processing.

Speech production is dependent on both auditory and somatosensory information. The auditory and somatosensory feedback occur in combination from the earliest vocalizations produced by an infant and both are involved in speech motor learning. Recent results suggest that somatosensory processes contribute to perception as well as production. For example, the identification of speech sounds is altered when a robotic device stretches the facial skin as participants listen to auditory stimuli1. Air puffs to the cheek that coincide with auditory speech stimuli alter participants&#39; perceptual judgments2.
These somatosensory effects involve the activation of cutaneous mechanoreceptors in response to skin deformation. The skin is deformed in various ways during movement, and cutaneous mechanoreceptors are known to contribute to kinesthetic sense3,4. The kinesthetic role of cutaneous mechanoreceptors is demonstrated by recent findings5-7 that the movement-related skin strains are appropriately perceived as flexion or extension motion depending on the pattern of skin stretch6. Over the course of speech motor training, which is the repetition of specific speech utterance with concomitant facial skin stretch speech, articulatory patterns change in an adaptive manner7. These studies indicate that modulating skin stretch during action provides a method for assessing the contribution of cutaneous afferents to the kinesthetic function of the sensorimotor system.
The kinesthetic function of orofacial cutaneous mechanoreceptors has been studied mostly using psychophysiological methods7,8 and microelectrode recoding from sensory nerves9,10. Here, the current protocol focuses on the combination of orofacial somatosensory stimulation associated with facial skin deformation and event related potential (ERP) recording. This procedure has precise experimental control over the direction and timing of facial skin deformation using a computer-controlled robotic device. This allows us to test specific hypotheses about the somatosensory contribution to speech production and perception by selectively and precisely deforming facial skin in a wide range of orientations during both speech motor learning and directly in speech production and perception. ERP recording are used to noninvasively evaluate the temporal pattern and timing of the influence of somatosensory stimulation on orofacial behaviors. The current protocol then can evaluate the neural correlates of kinesthetic function and assess the contribution of the somatosensory system to both speech processing, speech production and speech perception.
To show the utility of the application of skin stretch stimulation to ERP recording, the following protocol focuses on the interaction of somatosensory and auditory input in speech perception. The results highlight a potential method to assess somatosensory-auditory interaction in speech.

<table><tbody><tr><td>EEG recording system</td><td>Biosemi</td><td>ActiveTwo</td><td></td></tr><tr><td>Robotic decice for skin stretch</td><td>Geomagic</td><td>Phantom Premium 1.0</td><td></td></tr><tr><td>EEG-compatible earphones</td><td>Etymotic research</td><td>ER3A</td><td></td></tr><tr><td>Software for visual and auditory stimulation</td><td>Neurobehavioral Systems</td><td>Presentation</td><td></td></tr><tr><td>Electrode gel</td><td>Parker Laboratories, INC</td><td>Signa gel</td><td></td></tr><tr><td>Double sided tape</td><td>3M</td><td>1522</td><td></td></tr><tr><td>Disposable syringe</td><td>Monoject</td><td>412 Curved Tip</td><td></td></tr><tr><td>Analog input device</td><td>National Instuments&amp;nbsp;</td><td>PCI-6036E</td><td></td></tr><tr><td>Degital output device</td><td>Measurement computing</td><td>USB-1208FS</td><td></td></tr></tbody></table>

somatosensory event-related potentials from orofacial skin stretch stimulation

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of providing precise and controlled stimulation. This article introduces a technique for recording somatosensory event-related potentials (ERP) that uses a novel mechanical stimulation method involving skin deformation using a robotic device. Controlled deformation of the facial skin is used to modulate kinesthetic inputs through excitation of cutaneous mechanoreceptors. By combining somatosensory stimulation with electroencephalographic recording, somatosensory evoked responses can be successfully measured at the level of the cortex. Somatosensory stimulation can be combined with the stimulation of other sensory modalities to assess multisensory interactions. For speech, orofacial stimulation is combined with speech sound stimulation to assess the contribution of multi-sensory processing including the effects of timing differences. The ability to precisely control orofacial somatosensory stimulation during speech perception and speech production with ERP recording is an important tool that provides new insight into the neural organization and neural representations for speech.

This section presents representative event-related potentials in response to somatosensory stimulation resulting from facial skin deformation. The experimental setup is represented in Figure 1. Sinusoidal stimulation was applied to the facial skin lateral to the oral angle (See Figure 3A as reference). One hundred stretch trials were recorded for each participant with 12 participants tested in total. After removing the trials with blinks and eye movement artifacts offline on the basis of the horizontal and vertical electro-oculography signals (over &#177;150 &#181;V), more than 85% of trials were averaged. EEG signals were filtered with a 0.5-50 Hz band-pass filter and re-referenced to the average across all electrodes. Figure 2 shows the average somatosensory ERP from selected representative electrodes. In frontal regions, peak negative potentials were induced at 100-200 msec post stimulus onset followed by a positive potential at 200-300 msec. The largest response was observed in the midline electrodes. Different from the previous studies of somatosensory ERP15-18, there is no earlier latency (&#60;100 msec) potentials. This temporal pattern is rather similar to the typical N1-P2 sequence following auditory stimulation19. In comparison between the corresponding pair of electrodes in left and right hemisphere, the temporal pattern is quite similar probably due to the bilateral stimulation.
<img alt="Figure 1" src="/files/ftp_upload/53621/53621fig1.jpg" /> 
Figure 1.&#160;Experimental setup. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53621/53621fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53621/53621fig2.jpg" /> 
Figure 2.&#160;Event related potentials in response to somatosensory stimulation produced by facial skin stretch. The ERPs were obtained from representative electrodes. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53621/53621fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

The first result shows how the timing of stimulation affects multisensory interaction during speech processing12. In this study, neural response interactions were found by comparing ERPs obtained using somatosensory-auditory stimulus pairs with the algebraic sum of ERPs to the unisensory stimuli presented separately. The pattern of auditory-somatosensory stimulations are represented in Figure 3A. Figure 3B shows the pattern of event-related potentials in response to somatosensory-auditory stimulus pairs (Red line). The black line represents the sum of individual unisensory auditory and somatosensory ERPs. The three panels correspond to the time lag between two stimulus onsets: 90 msec lead of the somatosensory onset (Left), simultaneous (Center) and 90 msec lag (Right). When somatosensory stimulation was presented 90 msec before the auditory onset, there is a difference between paired and summed responses (the left panel in Figure 3B). This interaction effect gradually decreases as a function of the time lag between the somatosensory and auditory inputs (see the change between the two dotted lines in Figure 3B). The results demonstrate that the somatosensory-auditory interaction is dynamically modified with the timing of stimulation.
<img alt="Figure 3" src="/files/ftp_upload/53621/53621fig3.jpg" /> 
&#160;
Figure 3.&#160;Event-related potentials reflect a somatosensory-auditory interaction in the context of speech perception. This Figure has been modified from Ito, et al.12 (A) temporal pattern of somatosensory and auditory stimulations. (B) Event-related potentials for combined somatosensory and auditory stimulation in three timing conditions (lead, simultaneous, and lag) at electrode Pz. The red line represents recorded responses to paired ERPs. The dashed line represents the sum of somatosensory and auditory ERPs. The vertical dotted lines define an interval 160-220 msec after somatosensory onset in which differences between &#34;pair&#34; and &#34;sum&#34; responses are assessed. Arrows represent auditory onset. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53621/53621fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The next result demonstrates that the amplitude of the somatosensory ERP increases in response to listening to speech13. The pattern of somatosensory stimulation is the same as noted above. Figure 4 shows somatosensory ERPs, which are converted into scalp current density20 in off-line analysis, at electrodes (FC3, FC5, C3) over the left sensorimotor area. Somatosensory event-related potentials were recorded while participants listen to speech in the presence of continuous background sounds. The study tested four background conditions: speech, non-speech sounds, pink-noise and silent13. The results indicated the amplitude of somatosensory event-related potentials during listening to speech sounds was significantly greater than the other three conditions. There was no significant difference in amplitude for the other three conditions. Figure 4B shows normalized peak amplitudes in the different conditions. The result indicates that listening to speech sounds alters the somatosensory processing associated with facial skin deformation.
<img alt="Figure 4" src="/files/ftp_upload/53621/53621fig4.jpg" /> 
Figure 4.&#160;Enhancement of somatosensory event-related potentials due to speech sounds. The ERPs were recorded under four background sound conditions (Silent, Pink noise, Speech and Non-speech). This Figure has been modified from Ito, et al.13 (A) Temporal pattern of somatosensory event-related potentials in the area above left motor and premotor cortex. Each color corresponds to a different background sound condition. The ERPs were converted to scalp current density20. (B) Differences in z-score magnitudes associated with the first peak of the somatosensory ERPs. Error bars are standard errors across participants. Each color corresponds to different background sound conditions, as in Panel A. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53621/53621fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation

This paper introduces a method for obtaining somatosensory event-related potentials following orofacial skin stretch stimulation. The current method can be used to evaluate the contribution of somatosensory afferents to both speech production and speech perception.

Cortical processing associated with orofacial somatosensory function in speech has received limited experimental attention due to the difficulty of ...

somatosensory-event-related-potentials-from-orofacial-skin-stretch

Nanyang Technological University

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JoVE Journal

Neuroscience

13.1K Views.  Haskins Laboratories. This paper introduces a method for obtaining somatosensory event-related potentials following orofacial skin stretch stimulation. The current method can be used to evaluate the contribution of somatosensory afferents to both speech production and speech perception.

Video: Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation

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 ...

Behavior

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during&#160;viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception.&#160; This article describes how to record motor evoked potentials (MEPs) from the lip muscles and how to disrupt the motor lip representation using repetitive TMS.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. ...

Infant Auditory Processing and Event-related Brain Oscillations

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral and temporal changes that are characteristic of human language. These abilities lay the foundation for effective language acquisition; allowing infants to hone in on the sounds of their native language. Invasive procedures in animals and scalp-recorded potentials from human adults suggest that simultaneous, rhythmic activity (oscillations) between and within brain regions are fundamental to sensory development; determining the resolution with which incoming stimuli are parsed. At this time, little is known about oscillatory dynamics in human infant development. However, animal neurophysiology and adult EEG data provide the basis for a strong hypothesis that rapid auditory processing in infants is mediated by oscillatory synchrony in discrete frequency bands. In order to investigate this, 128-channel, high-density EEG responses of 4-month old infants to frequency change in tone pairs, presented in two rate conditions (Rapid: 70 msec ISI and Control: 300 msec ISI) were examined. To determine the frequency band and magnitude of activity, auditory evoked response averages were first co-registered with age-appropriate brain templates. Next, the principal components of the response were identified and localized using a two-dipole model of brain activity. Single-trial analysis of oscillatory power showed a robust index of frequency change processing in bursts of Theta band (3 - 8 Hz) activity in both right and left auditory cortices, with left activation more prominent in the Rapid condition. These methods have produced data that are not only some of the first reported evoked oscillations analyses in infants, but are also, importantly, the product of a well-established method of recording and analyzing clean, meticulously collected, infant EEG and ERPs. In this article, we describe our method for infant EEG net application, recording, dynamic brain response analysis, and representative results.

High-density electroencephalography (dEEG) is being used increasingly to study brain development and plasticity in the early years of life. Here we present an application of sophisticated analysis techniques that builds on traditional EEG recording to understand the oscillatory dynamics of rapid auditory processing in the infant brain.

Rapid auditory processing and acoustic change detection abilities play a critical role in allowing human infants to efficiently process the fine spectral ...

Event-related Potentials During Target-response Tasks to Study Cognitive Processes of Upper Limb Use in Children with Unilateral Cerebral Palsy

Unilateral Cerebral Palsy (CP) is a neurodevelopmental disorder that is a very common cause of disability in childhood. It is characterized by unilateral motor impairments that are frequently dominated in the upper limb. In addition to a reduced movement capacity of the affected upper limb, several children with unilateral CP show a reduced awareness of the remaining movement capacity of that limb. This phenomenon of disregarding the preserved capacity of the affected upper limb is regularly referred to as Developmental Disregard (DD). Different theories have been postulated to explain DD, each suggesting slightly different guidelines for therapy. Still, cognitive processes that might additionally contribute to DD in children with unilateral CP have never been directly studied. The current protocol was developed to study cognitive aspects involved in upper limb control in children with unilateral CP with and without DD. This was done by recording event-related potentials (ERPs) extracted from the ongoing EEG during target-response tasks asking for a hand-movement response. ERPs consist of several components, each of them associated with a well-defined cognitive process (e.g., the N1 with early attention processes, the N2 with cognitive control and the P3 with cognitive load and mental effort). Due to its excellent temporal resolution, the ERP technique enables to study several covert cognitive processes preceding overt motor responses and thus allows insight into the cognitive processes that might contribute to the phenomenon of DD. Using this protocol adds a new level of explanation to existing behavioral studies and opens new avenues to the broader implementation of research on cognitive aspects of developmental movement restrictions in children.

Several children with unilateral Cerebral Palsy seem to disregard the preserved capacity of their affected upper limb. This Developmental Disregard is extensively described in the literature but the involved cognitive processes have not been studied. To study underlying cognitive factors of upper limb control, an event-related potential protocol was developed.

Unilateral Cerebral Palsy (CP) is a neurodevelopmental disorder that is a very common cause of disability in childhood. It is characterized by unilateral ...

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, ...

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. ...

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

How to Find Effects of Stimulus Processing on Event Related Brain Potentials of Close Others when Hyperscanning Partners

The partners of each pair must be able to pass the McGill Friendship Questionnaire without communicating. Each partner is then seated in front of a screen in one of two adjacent rooms. These rooms are separated by a glass window through which participants communicate to maintain feelings of togetherness while being fitted with the EEG cap. After checking for adequate EEG signals, the glass is covered by a curtain to prevent visual communication. Then, partners must be silent but are instructed to try to feel in the presence of their partner during the entire experiment. Just before it starts, participants are told that each of them will be presented with one image at a time and that these images will occur at the same time for both of them on their own screen. They are also instructed that, for each trial, the simultaneous images will always be different. However, unbeknownst to them, trials are randomized: only half of them are consistent with this instruction and actually include two different images. These trials form the DSC, that is, the different-stimuli condition. The other half of the trials are inconsistent with the instruction. They include two identical images and form the ISC (identical-stimuli condition). After the experiment, participants are sorted into two groups: those who reported that they felt in the presence of their partner during the majority of the trials and those who reported they did not. The impact of the stimulus processing of the partner is found by subtracting the mean voltages of the ERPs of the ISC (inconsistent with the instructions) from the ERPs of the DSC (consistent with the instructions) in at least two time windows (TWs): firstly, in the 75 to 150 ms TW, where the absolute values of these subtractions are greater, especially at right frontal sites, in those who felt in the presence of their partner than in those who did not; secondly, in the LPP time window (i.e., from 650 to 950 ms post onset), where ERPs are significantly less positive in the DSC than in the ISC in those in whom the raw results of the early (75-150ms) subtractions are negative.

This protocol describes key steps involved in assessing the sensitivity of the brain of one person to the stimulus processing of a close other by selecting pairs of partners, recording their electroencephalogram (EEG) simultaneously and computing their event-related brain potentials (ERPs).

The partners of each pair must be able to pass the McGill Friendship Questionnaire without communicating. Each partner is then seated in front of a screen ...

Assessment of Audio-Tactile Sensory Substitution Training in Participants with Profound Deafness Using the Event-Related Potential Technique

This paper examines the application of electroencephalogram-based methods to assess the effects of audio-tactile substitution training in young, profoundly deaf (PD) participants, with the aim of analyzing the neural mechanisms associated with vibrotactile complex sound discrimination. Electrical brain activity reflects dynamic neural changes, and the temporal precision of event-related potentials (ERPs) has proven to be key in studying time-locked processes while performing behavioral tasks that involve attention and working memory. 
The current protocol was designed to study electrophysiological activity in PD subjects while they performed a continuous performance task (CPT) using complex-sound stimuli, consisting of five different animal sounds delivered through a portable stimulator system worn on the right index finger. As a repeated-measures design, electroencephalogram (EEG) recordings in standard conditions were performed before and after a brief training program (five 1 h sessions over 15 days), followed by offline artifact correction and epoch averaging, to obtain individual and grand-mean waveforms. Behavioral results show a significant improvement in discrimination and a more robust P3-like centroparietal positive waveform for the target stimuli after training. In this protocol, ERPs contribute to the further understanding of learning-related neural changes in PD subjects associated with audio-tactile discrimination of complex sounds.

This protocol is designed to explore underlying learning-related electrophysiological changes in subjects with profound deafness after a short training period in audio-tactile sensory substitution by applying the event-related potential technique.

This paper examines the application of electroencephalogram-based methods to assess the effects of audio-tactile substitution training in young, ...

Effect of Odor on Brain Excitability Assessed by a Breath-Synchronized Olfactometer

Combining a Breath-Synchronized Olfactometer with Brain Simulation to Study the Impact of Odors on Corticospinal Excitability and Effective Connectivity

It is widely accepted that olfactory stimulation elicits motor behaviors, such as approaching pleasant odorants and avoiding unpleasant ones, in animals and humans. Recently, studies using electroencephalography and transcranial magnetic stimulation (TMS) have demonstrated a strong link between processing in the olfactory system and activity in the motor cortex in humans. To better understand the interactions between the olfactory and the motor systems and to overcome some of the previous methodological limitations, we developed a new method combining an olfactometer that synchronizes the random order presentation of odorants with different hedonic values and the TMS (single- and dual-coil) triggering with nasal breathing phases. This method allows probing the modulations of corticospinal excitability and effective ipsilateral connectivity between the dorsolateral prefrontal cortex and the primary motor cortex that could occur during pleasant and unpleasant odor perception. The application of this method will allow for objectively discriminating the pleasantness value of an odorant in a given participant, indicating the biological impact of the odorant on brain effective connectivity and excitability. In addition, this could pave the way for clinical investigations in patients with neurological or neuropsychiatric disorders who may exhibit&#160;odor hedonic alterations and maladaptive approach-avoidance behaviors.

Author Spotlight: Exploring Olfactory Influences on Corticospinal Excitability - Insights and Innovations in Neurological Research 

This paper describes using a breath-synchronized olfactometer to trigger single- and dual-coil transcranial magnetic stimulation (TMS) during odorant presentation synchronized to human nasal breathing. This combination allows us to objectively investigate how pleasant and unpleasant odors impact corticospinal excitability and brain-effective connectivity in a given individual.

It is widely accepted that olfactory stimulation elicits motor behaviors, such as approaching pleasant odorants and avoiding unpleasant ones, in animals ...

Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation

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