Name: assessment of audio-tactile sensory substitution training in participants with profound deafness using the event-related potential technique
Uploaded: 2022-09-07T13:40:00.000+00:00
Duration: 11 min 39 s
Description: Watch this Scientific Journal Video about Assessment of Audio-Tactile Sensory Substitution Training in Participants with Profound Deafness Using the Event-Related Potential Technique at JoVE.com

We thank all the participants and their families, as well as the institutions that made this work possible, in particular, Asociaci&#243;n de Sordos de Jalisco, Asociaci&#243;n Deportiva, Cultural y Recreativa de Silentes de Jalisco, Educaci&#243;n Incluyente, A.C., and Preparatoria No. 7. We also thank Sandra M&#225;rquez for her contribution to this project. This work was funded by GRANT SEP-CONACYT-221809, GRANT SEP-PRODEP 511-6/2020-8586-UDG-PTC-1594, and the Neuroscience Institute (Universidad de Guadalajara, Mexico).

The study was reviewed and approved by the Neuroscience Institute&#39;s Ethics Committee (ET062010-88, Universidad de Guadalajara), ensuring all procedures were conducted in accordance with the Declaration of Helsinki. All participants agreed to participate voluntarily and gave written informed consent (when underaged, parents signed consent forms).
1. Experimental design
<ol>
	<li>Stimulus preparation
	<ol>
		<li>Search in Creative Commons licensed sound databases to select a set of animal sounds in .wav format. The stimuli in this study consisted of five different animal sounds: dog barking, cow mooing, horse neighing, donkey braying, and elephant trumpeting. 
		NOTE: The sound stimuli used here were previously selected as a collection of sounds for the vibrotactile discrimination training program in our earlier studies9,10.</li>
		<li>Edit the sound files using a free, open-source audio editor to standardize the intensity and length of the stimuli to 1500 ms. For this protocol, standardize at a linear scale from 0 to 8000 Hz, at a gain of 20 dB, and at a range of 80 dB based on the parameters established in the previous studies9,10 using the same vibrotactile stimulation system.</li>
		<li>Save the formatted audio files in a 32-bit float format with a 48,000 Hz project rate.</li>
	</ol>
	</li>
	<li>Paradigm setup in the electrophysiology presentation software
	<ol>
		<li>Design a continuous performance task (CPT) using an experimental design and stimulus presentation software, assigning the stimuli to one of the two conditions: (a) target (T) stimulus (dog barking in 20% of trials) and (b) non-target (NT) stimuli (the remaining four animal sounds for the other 80%). 
		NOTE: Each condition was labeled with the same code to synchronize stimulus presentation marks when programming the EEG protocol in the recording software.</li>
		<li>Build a pseudo-randomized stimulus-presentation using the software platform in which the five animal sounds (dog, cow, horse, donkey, and elephant) are each presented 20% of the time. Check that the target stimulus (dog barking) never occurs more than twice in succession.</li>
		<li>Specify the desired interstimulus interval (ISI) and the total response time, and select the response keys that will be used to automatically collect behavioral data for target (T) stimuli responses. Here, a fixed 2000 ms ISI list for 150 trials and the correct response for the T stimuli were programmed via the left control key on a standard computer keyboard. Participants were given a 3500 ms time window for a behavioral response (starting at stimulus presentation).</li>
	</ol>
	</li>
</ol>
2. Participant selection
<ol>
	<li>Recruit potential participants with profound bilateral sensorineural hearing loss diagnosis and collect demographic data, including age, sex, hand preference, and educational history.</li>
	<li>Conduct semi-structured clinical interviews to screen participants for personal or family history of psychiatric, neurological, or neurodegenerative illness and to collect information pertaining to deafness clinical history: the age of onset, etiology, and hearing-aid use history, as well as their preferred communication mode (oral, manual, or bilingual).</li>
	<li>Conduct audiological tests (pure-tone air hearing-thresholds) using an audiometer to confirm the severity of hearing loss.
	<ol>
		<li>In a sound-attenuated room, sit directly in front of the participant and properly place headphones on them.</li>
		<li>Instruct the participants to raise their dominant hand to signal whenever they can hear the tone being presented through the headphones.</li>
		<li>Ranging from 20 dB to 110 dB intensity levels, present a pure-tone at six octaves in the following ascending order: 250, 500, 1000, 2000, 4000, and 8000 Hz, starting with the left ear and repeating the same steps for the right ear.
		<ol>
			<li>Calculate the patient pure-tone average (PTA) by averaging the hearing thresholds at 500, 1000, 2000, and 4000 Hz for each ear. The hearing-loss severity inclusion criteria for the study is a bilateral pure tone average (PTA) greater than 90 dB.</li>
			<li>Select participants based on the eligibility criteria. Inclusion criteria additionally include no personal or family history of psychiatric, neurological, or neurodegenerative illness and non-syndromic, prelingual profound bilateral deafness. Obtain informed consent and explain the experimental procedures to the participants. 
			&#8203;NOTE: All the forms, questionnaires, and instructions used in the study were translated to Mexican Sign Language (MSL) by a professional MSL interpreter and were presented in video format using a tablet computer. In addition, an MSL interpreter was present during all study procedures.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
3. Pre-training EEG recording session
<ol>
	<li>Participant preparation
	<ol>
		<li>Verify that the participants have come to the recording session with clean and dry hair, having not used any hair gel, conditioner, or other hair products that affect electrode impedance.</li>
		<li>Ask the participants to sit in a comfortable position, approximately 60 cm away from the stimulus screen, and use the tablet device to play the MSL videoclip with the preparation procedure description.</li>
		<li>Clean the areas where reference and electrooculogram (EOG) electrodes will be placed (earlobes, forehead, outer canthus, infraocular orbital ridges, etc.). First, wipe the skin with an alcohol swab, and then apply EEG abrasive prepping gel gently with a cotton swab to exfoliate dead skin cells on the surface.</li>
		<li>Fill the electrode gold cup with conductive electrode paste and place an electrode on each reference site, usually on the right and the left earlobes or mastoids. Repeat the steps to place at least one vertical EOG at the outer canthus and one horizontal EOG at the infraocular orbital ridge to monitor oculomotor activity (blinks and saccades). Hold the single electrodes in place with a piece of 1 in micropore tape.</li>
		<li>Ask the participants to hold their arms straight horizontally and then fit the body harness tightly but comfortably around the chest under the armpits with the snaps in the middle of the chest.</li>
		<li>Place the EEG commercial electro-cap with 19 Ag/AgCl electrodes (Fp1, Fp2, F3, F4, F7, F8, C3, C4, P3, P4, O1, O2, T3, T4, T5, T6, Fz, Cz, and Pz) topographically arranged according to the International 10-20 system. Use a measuring tape to check the participant&#39;s head circumference to ensure you use the proper cap size.</li>
		<li>Align the Cz electrode with the nose and then measure the distance from the nasion to the inion so that the Cz electrode falls precisely in the middle. Button the adjustable straps on the sides of the cap to the body harness so that the electro-cap is firmly tightened.</li>
		<li>Place the gel-filled blunt-needle syringe inside the electrode, circle the needle to remove hair, and then gently abrade the scalp region under the electrode before applying the conductive gel. Don&#39;t apply too much gel to avoid electrical bridging with neighboring electrode sites.</li>
		<li>Allow the EEG conductive gel to dry at cool room temperature.</li>
	</ol>
	</li>
	<li>Setting up the EEG recording equipment
	<ol>
		<li>Calibrate the EEG system as per the instrument&#39;s instructions, then connect the electro-cap to the amplifier set at a bandpass of 0.05-30 Hz (3 dB cutoff points of 6 dB/octave roll-off curves), a 60 Hz notch-filter, and a 200 Hz sampling rate equal to a 5 ms sampling period.</li>
		<li>Check that the impedance is below 5 K&#937; (for a low impedance system) in all electrode sites and check on the monitor that all channels are smoothly registering the electrical signals.</li>
	</ol>
	</li>
	<li>Running the experimental task
	<ol>
		<li>Position the participant in front of the computer monitor and place the keyboard at a comfortable distance.</li>
		<li>Connect the cable of the portable stimulator device (see Figure 1) to the computer system speaker&#39;s outlet and set the speaker volume to the maximum intensity level.</li>
		<li>Adjust the portable stimulator system on the participant&#39;s right index fingertip and test.</li>
		<li>Using the tablet device, play the experiment instructions and execute a practice trial to familiarize the subject with the portable stimulator device, the audio-tactile stimuli, and the task. Repeat the MSL instructions and verify comprehension.</li>
		<li>Remind the participant to respond to the dog bark stimulus by pressing the left control key with their left index finger only upon target stimulus detection and to withhold their response when any of the other four animal sounds are perceived. The CPT experimental paradigm is represented in Figure 2.</li>
		<li>Provide clear instructions for how to minimize artifacts and demonstrate the effect of artifacts on the EEG in real-time before you begin recording (recommended as a standard recording procedure in research with clinical populations20).</li>
		<li>Before starting the CPT task, check that the event-synchronization between the cognitive stimulation computer and the EEG recording computer is working properly. To do so, start recording the EEG signal and click on the communication icon in the stimulus presentation software interface. Upon clicking, the event-synchronized pulses appear at the bottom of the EEG recording screen.</li>
		<li>Run the experimental task. Carefully observe the participant and monitor alertness, response execution, and excessive movement or blinking.</li>
		<li>Pause and allow the participant a short break in the middle of the experiment (at 4 min in the experiment) to allow them to blink, relax, and move around if needed. Finish running the experiment.</li>
	</ol>
	</li>
</ol>
4. Audio-tactile sensory substitution training program
<ol>
	<li>Consult Supplementary File 1, which contains a detailed description of the five-session program, to perform the training. Automatize the activities described using a spreadsheet to make the training more systematic and engaging for the participants. Use original images and audio recordings from9 and ask the participants to respond by tapping on a laptop touch-screen monitor. 
	&#8203;NOTE: The content and tables in this file have been reprinted with permission from9.</li>
</ol>
5. Post-training EEG recording session
<ol>
	<li>Repeat the exact same steps as specified in section 3.</li>
</ol>
6. EEG analysis
NOTE: The EEG acquisition steps were done using the EEG recording software, and the EEG processing steps were done using a separate EEG analysis software.
<ol>
	<li>EEG raw signal pre-processing
	<ol>
		<li>Define and select epochs of 1100 ms in the continuous EEG data, without the use of additional digital filters, using stimulus onset as the initial time instant (t0), and including a 100 ms pre-stimulus used for baseline correction. Supplementary Figure 1 illustrates how the 1100 ms epochs were selected according to the EEG analysis commercial software installed in the EEG recording equipment.</li>
		<li>During artifact rejection, exclude epochs of data on all channels when the voltage in a given recording epoch exceeds 100 &#181;V on any EEG or EOG channel. Also, reject artifacts by visual inspection of the epochs. See Supplementary Figure 2, which provides an example of epochs that were manually rejected due to ocular artifacts.</li>
	</ol>
	</li>
	<li>Signal averaging
	<ol>
		<li>Select an equal number of artifact-free epochs for each stimulus condition (target and non-target) in both the pre- and post-training conditions. Select the maximum epochs possible to improve the signal-to-noise ratio. Do this for each EEG record. 
		NOTE: In this protocol, we selected an average of 25 correct response epochs per condition at each timepoint since we were interested in evaluating target discrimination. Keep in mind that some ERP components do not require overt behavioral responses to be observed. Participants with less than 15 artifact-free epochs in each condition were excluded from the study.</li>
		<li>Click on the Operations menu and select the EEG window averaging option to average individual ERPs.</li>
		<li>First, select the Independent Average option to average target trials only. Then, select the other four non-target stimuli and click on the Average Together option to average.</li>
		<li>Repeat steps 6.2.2 and 6.2.3 for each participant&#39;s EEG recording in the pre-training condition and then for the post-training condition.</li>
		<li>Once all the individual ERPs are calculated, average them together to obtain the grand-mean waveforms per stimulus condition for pre- and post-training. Open any individual EP average, then go to the Operations menu and select Grand-mean averaging option. Select the participant&#39;s individual averages to be included in the group average.</li>
		<li>Choose all pre-training target averages from the drop-down list, then click the Average button, type the desired file name, and press the Return key to save. Then select all pre-training non-target averages from the drop-down list, click the Average button, type the desired file name, and again press the Return key to save.</li>
		<li>Repeat the previous steps for the post-training condition.</li>
	</ol>
	</li>
	<li>ERP visualization and analyses
	<ol>
		<li>Select the Operations&#160;menu&#160;to see the list of saved grand means. Then click on the group averages that you wish to plot. Next, click the Montage button to select the channels you want to plot.</li>
		<li>Go to the Tools menu, then click on Visualize Options to select each waveform&#39;s color and line width. Then click on the Signal menu, check the DC correction box, type in the desired baseline stimulus interval, then press the Return key.</li>
		<li>Carefully inspect the plotted grand-mean waveforms to identify the components of interest and their corresponding time windows. 
		NOTE: For this experiment, we knew that the waveforms, because of the task design and sensory pathways understudy for P3, would very likely be a positive component appearing later than 300 ms in centroparietal electrodes and with greater voltage amplitudes in the target condition.</li>
		<li>Export individual peak amplitude latencies and voltages, and then import data on a spreadsheet to build the database. Conduct a repeated-measures Analysis of Variance (ANOVA) using a statistics software.</li>
	</ol>
	</li>
</ol>

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We confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.

Using ERP tools, we designed a protocol to observe and evaluate the gradual development of vibrotactile discrimination skills for distinguishing vibrotactile representations of different pure tones. Our prior work has demonstrated that vibrotactile stimulation is a viable alternative sound perception method for profoundly deaf individuals. However, because of the complexity of natural sounds compared to pure tones, the potential for language sound discrimination warrants a separate exploration.
As the first step in this direction, the current protocol focuses on the spatiotemporal appearance of ERP components to further understand the learning-related neural changes in PD subjects associated with audio-tactile discrimination of complex sounds. Even though a unique consensus regarding the P3's precise functional role in decision-making has not been reached, our results suggest that the P3 reflects a working memory-guided target identification mechanism21, a type of categorization that can be modified with practice after several training sessions as part of a goal-directed learning strategy. The P3 waveforms observed in this experiment are consistent with the proposal that this component could be tracing the identification process itself rather than being elicited by the completion of the stimulus identification22. Both behavioral and electrophysiological results support the notion that natural complex sounds, such as those used in this experiment, can be identified and distinguished through a vibrotactile discrimination process once individuals are appropriately trained. However, several limitations have been carefully considered, particularly the ideal extension of the sample. It is well-known that the clinical population afflicted with profound deafness is heterogeneous in nature. Many variables such as etiology, degree of hearing loss, age of onset, parental hearing status, language exposure, hearing aid use, and educational background are difficult to control when selecting a study sample with a severe auditory deficit. Individuals with non-syndromic, prelingual profound bilateral deafness are a complex sample to come across. We interviewed 36 candidates with profound hearing loss who were interested in participating in this study. Of those, 23 fulfilled the inclusion criteria, and only 17 completed the study (five training sessions and the pre-and post-EEG recording sessions) and had sufficient artifact-free EEG data required for ERP averaging. Most studies that include participants from a clinical population with profound bilateral deafness have broad age ranges and small heterogenous samples. During the experiment, all efforts were made to procure a sample as homogeneous as possible. 
Another essential methodological consideration in this protocol is why an average of 25 epochs per condition (25 target and 25 non-target) was used to obtain the individual ERP averages. This decision was made since it is necessary to optimize the number of trials included in an experiment by balancing the trade-off between the quality of the data and the amount of time and resources spent collecting the data. Particularly, when working with clinical populations, there are practical limits on the number of trials that can be presented in a single experiment since it is advisable to reduce the time participants spend in the lab20. Participants become fatigued and fidgety if the experiment takes too long causing an increase in the noise level in the data and negatively impacting performance on the task. It is critical to acknowledge that there is ongoing controversy as to how many trials are needed to get significant ERP effects23, because it depends on several factors such as the ERP component in question, the number of recording sites, the signal-to-noise ratio, and certain measures such as Cronbach's alpha (within acceptable parameters when greater than 0.6 or 0.07). Several sources have estimated an appropriate number of trials required for stable P300 waveforms at around 20 trials24, 36 trials25, 40 to 50 trials26, and even up to 60 trials27. More specifically, in cognitive control tasks such as the Go-NoGo paradigm, Rietdijk and colleagues28 concluded that a minimum of 14 trials were required to obtain an internally consistent estimate for the P3 in this type of task. The above-mentioned considerations were taken into account both for the experimental design and the ERP averaging technique described in this study.
In sum, event-related brain potentials are a reliable and commonly used tool for analyzing the electrical changes underlying brain function and behavior dynamics. One of the most prominent and persistent electrophysiological ERP responses is the P3 component, which is proposed as a reliable indicator for evaluating the discrimination of vibrotactile stimuli across several proposed methods29. The fact that ERPs have high internal consistency and high test-retest reliability means that they are an ideal technique for examining changes in brain activity resulting from treatment intervention in repeated-measures designs. However, it is also important to note the limitations of this ERP technique, where the small magnitudes of certain ERP components may take many trials to guarantee accurate measures, and the spatial resolution of the ERPs is much poorer than other neuroimaging techniques. As such, this technique is better suited for understanding the temporal dynamics of neurofunctional activation rather than the exact localization of this activation. 
Despite these methodological challenges, renewed exploration of the neurodevelopmental evolution and connectivity of brain differences resulting from early auditory deprivation is an opportunity to further the understanding of sensory substitution and language acquisition, specifically when turning to younger, profoundly deaf populations. ERP components remain some of the best tools available to neuroscientists to meet this challenge and have yet to yield results with important future implications.

Early profound deafness is a sensory deficit that strongly impacts oral language acquisition and the perception of environmental sounds that play an essential role in navigating everyday life for those with normal hearing. A preserved and functional auditory sensory pathway allows us to hear footsteps when someone is approaching out of visual range, react to oncoming traffic, ambulance sirens, and security alarms, and respond to our own name when someone needs our attention. Audition is, therefore, a vital sense for speech, communication, cognitive development, and timely interaction with the environment, including the perception of potential threats in one&#39;s surroundings. For decades, the viability of audio-tactile substitution as an alternative sound perception method with the potential to complement and facilitate language development in severely hearing-impaired individuals has been explored with limited results1,2,3. Sensory substitution aims to provide users with environmental information through a human sensory channel different from the one normally used; it has been demonstrated to be possible across different sensory systems4,5. Specifically, audio-tactile sensory substitution is achieved when skin mechanoreceptors can transduce the physical energy of soundwaves that compose auditory information into neuronal excitation patterns that can be perceived and integrated with the somatosensory pathways and higher order somatosensory cortical areas6.
Several studies have demonstrated that profoundly deaf individuals can distinguish musical timbre solely through vibrotactile perception7 and discriminate between same-sex speakers using spectral cues of complex vibrotactile stimuli8. More recent findings have shown that deaf individuals concretely benefitted from a brief, well-structured audio-tactile perception training program, as they significantly improved their ability to discriminate between different pure-tone frequencies9 and between pure-tones with different temporal duration10. These experiments used event-related potentials (ERPs), graph connectivity methods, and quantitative electroencephalogram (EEG) measurements to depict and analyze functional brain mechanisms. However, the neural activity associated with the discrimination of complex environmental sounds has not been examined prior to this paper.
ERPs have proven useful for studying time-locked processes, with incredible time resolution in the order of milliseconds, while performing behavioral tasks that involve attention allocation, working memory, and response selection11. As described by Luck, Woodman, and Vogel12, ERPs are intrinsically multidimensional processing measures and are therefore well suited to separately measure the subcomponents of cognition. In an ERP experiment, the continuous ERP waveform elicited by the presentation of a stimulus can be used to directly observe neural activity that is interposed between the stimulus and the behavioral response. Other advantages of the technique, such as its cost-effectiveness and non-invasive nature, make it a perfect fit to study the precise time course of cognitive processes in clinical populations. Furthermore, ERP tools applied in a repeated-measures design, in which patients&#39; electrical brain activity is recorded more than once to study changes in electrical activity after a training program or intervention, provide further insight into neural changes over time.
The P3 component, being the most extensively researched cognitive potential13, is currently recognized to respond to all kinds of stimuli, most apparently to stimuli of low probability, or of high intensity or significance, or ones that require some behavioral or cognitive response14. This component has also proven extremely useful in evaluating general cognitive efficiency in clinical models15,16. A clear advantage of assessing changes in the P3 waveform is that it is an easily observable neural response because of its greater amplitude compared to other smaller components; it has a characteristic centroparietal topographical distribution and is also relatively easy to elicit using the appropriate experimental design17,18,19.
In this context, the aim of this study is to explore the learning-related electrophysiological changes in patients with profound deafness after training for a short period in vibrotactile sound discrimination. In addition, ERP tools are applied to depict the functional brain dynamic underlying the temporary engagement of the cognitive resources demanded by the task.

<table><tbody><tr><td>Audacity</td><td>Audacity team</td><td>audacityteam.org</td><td>Free, open source, cross-platform audio editing software</td></tr><tr><td>Audiometer</td><td>Resonance</td><td>r17a</td><td></td></tr><tr><td>EEG analysis Software</td><td>Neuronic&amp;nbsp;, S.A.</td><td></td><td></td></tr><tr><td>EEG recording Software</td><td>Neuronic&amp;nbsp;, S.A.</td><td></td><td></td></tr><tr><td>Electro-Cap&amp;nbsp;</td><td>Electro-cap International, Inc.</td><td>E1-M</td><td>Cap with 19 active electrodes, adjustable straps and chest harness.&amp;nbsp;</td></tr><tr><td>Electro-gel</td><td>Electro-cap International, Inc.</td><td></td><td></td></tr><tr><td>External computer speakers</td><td></td><td></td><td></td></tr><tr><td>Freesound&amp;nbsp;</td><td>Music technology group</td><td>freesound.org</td><td>Database of Creative Commons Licensed sounds</td></tr><tr><td>Hook and loop fastner</td><td>Velcro</td><td></td><td></td></tr><tr><td>IBM SPSS (Statistical Package for th Social Sciences)</td><td>IBM</td><td></td><td></td></tr><tr><td>Individual electrodes&amp;nbsp;</td><td>Cadwell</td><td></td><td>Gold Cup, 60 in</td></tr><tr><td>MEDICID-5</td><td>Neuronic, S.A.</td><td></td><td>EEG recording equipment (includes amplifier and computer).</td></tr><tr><td>Nuprep</td><td>Weaver and company</td><td></td><td>ECG &amp;amp; EEG abrasive skin prepping gel</td></tr><tr><td>Portable computer with touch screen</td><td>Dell</td><td></td><td></td></tr><tr><td>SEVITAC-D</td><td>Centro Camac, Argentina. Patented by Luis Campos (2002).</td><td>http://sevitac-d.com.ar/</td><td>Portable stimulator system is worn on the index-finger tip and it consists of a tiny flexible plastic membrane with a 78.5 mm2 surface area that vibrates in response to sound pressure waves via analog transmission. It has a sound frequency range from 10 Hz to 10 kHz.&amp;nbsp;</td></tr><tr><td>Stimulus presentation Software Mindtracer</td><td>Neuronics, S.A.</td><td></td><td></td></tr><tr><td>Stimulation computer monitor and keyboard</td><td></td><td></td><td></td></tr><tr><td>Tablet computer</td><td>Lenovo</td><td></td><td></td></tr><tr><td>Ten20 Conductive Neurodiagnostic Electrode paste</td><td>weaver and company</td><td></td><td></td></tr></tbody></table>

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.

To illustrate how the effect of the audio-tactile sensory substitution discrimination training in PD individuals can be assessed by evaluating changes in P3 in a group of 17 PD individuals (mean age = 18.5 years; SD = 7.2 years; eight females and 11 males), we created several figures to portray the ERP waveforms. The results shown in the ERP plots reveal changes in a P3-like centroparietal positive waveform which is more robust for the target stimuli after training. In the pre-training condition, ERPs suggest that the T and NT conditions are not as clearly distinguishable as in the post-training condition. Therefore, it is suggested that the five-session training program has an impact on the neural response associated with complex-sound stimuli discrimination. Figure 3 shows the pre-training grand averages, and Figure 4 shows the post-training grand averages, which portray the main results of this investigation. Figure 5 shows how these ERP waveforms are modified when plotted using a low-pass digital filter at 5 Hz. This a posteriori filtering significantly reduces the noise, introduced primarily by individual variability, while conserving the training-related changes in the P3 waveforms of interest in this investigation.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64266/64266fig1v2.jpg" /> 
Figure 1: Photograph of the portable stimulation system (left) and demonstration of how it should be placed on the index finger (right). This device consists of a tiny flexible plastic membrane with a 78.5 mm2 surface area that vibrates in response to sound pressure waves via analog transmission, a long analog speaker input cable, and a red fastening strip to adjust to the index finger. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/64266fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64266/64266fig2v2.jpg" /> 
Figure 2: Diagram of the continuous performance task (CPT). The spectral images corresponding to each of the five categories of stimulus are shown (all with a duration of 1500 ms). The target stimulus (barking) is labeled, and the ISI (inter-stimulus interval) duration is specified (2000 ms). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/64266fig2v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64266/64266fig3v2.jpg" /> 
Figure 3: Pre-training grand-mean waveforms and topographical voltage distribution maps. This figure shows the nine fronto-centro-parietal electrodes (F3, Fz, F4, C3, Cz, C4, P3, Pz, and P4) of the 10-20 system electrode array. Red lines correspond to the target condition and black lines to the non-target condition. The colored maps represent the voltage distribution in micro-volts (&#956;V) at 620 milliseconds (ms). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/64266fig3v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/64266/64266fig4v2.jpg" /> 
Figure 4: Post-training grand-mean waveforms and topographical distribution maps. This figure shows the nine fronto-centro-parietal electrodes (F3, Fz, F4, C3, Cz, C4, P3, Pz, and P4) of the 10-20 system electrode array. Red lines correspond to the target condition and black lines to the non-target condition. The colored maps represent the voltage distribution in micro-volts (&#956;V) at 620 milliseconds (ms). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/64266fig4v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64266/64266fig05.jpg" /> 
Figure 5: Pre-training (left) and post-training (right) filtered grand-mean waveforms and topographical distribution maps. This figure shows the three midline electrodes (Fz, Cz, and Pz) of the 10-20 system electrode array after an off-line digital 5 Hz low-pass filter was applied. Blue lines correspond to the target condition and black lines to the non-target condition. The colored maps represent the voltage distribution in micro-volts (&#956;V) at 630 milliseconds (ms). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/64266fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplementary Figure 1: Epoch selection in raw EEG recording using analysis software. This screenshot shows an EEG record with the signal from 21 channels (19 active electrodes and 2 oculogram electrodes). The 1100 millisecond (ms) epochs, starting at 100 ms prior to stimulus presentation, are selected in an aqua rectangle. The thin red lines at the bottom of the screen are the synchronized-stimulus presentation pulses embedded in the EEG signal. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/Supplementary figure 2.pdf" target="_blank">Please click here to download this File.</a>
Supplementary Figure 2: Examples of manually rejected epochs showing ocular artifacts. This screenshot shows an EEG record with the signal from 21 channels (19 active electrodes and two oculogram electrodes). Epochs selected in a magenta rectangle have been manually rejected because they contain ocular artifacts caused by blinking. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/Supplementary figure 3.pdf" target="_blank">Please click here to download this File.</a>
Supplementary File 1: Audio-tactile sensory substitution training program. A detailed description of the five-session program. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64266/Supplementary material 1.pdf" target="_blank">Please click here to download this File.</a>

Watch this Scientific Journal Video about Assessment of Audio-Tactile Sensory Substitution Training in Participants with Profound Deafness Using the Event-Related Potential Technique at JoVE.com

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

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, ...

assessment-audio-tactile-sensory-substitution-training-participants

Nanyang Technological University

Research

JoVE Journal

Neuroscience

1.9K Views.  Universidad de Guadalajara. Ons protocol laat zien hoe ERP's kunnen worden toegepast om leergerelateerde neurale veranderingen te onderzoeken bij proefpersonen met diepe doofheid na een korte trainingsperiode in vibrotactiele discriminatie van complexe natuurlijke geluiden. Het belangrijkste voordeel van de ERP-techniek is dat het de studie mogelijk maakt van de precieze temporele dynamiek van elektrische hersenactiviteit die ten grondslag ligt aan cognitieve verwerking tijdens audio-tactiele sensorische substitutie. De...

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

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

Combined Shuttle-Box Training with Electrophysiological Cortex Recording and Stimulation as a Tool to Study Perception and Learning

Shuttle-box avoidance learning is a well-established method in behavioral neuroscience and experimental setups were traditionally custom-made; the necessary equipment is now available by several commercial companies. This protocol provides a detailed description of a two-way shuttle-box avoidance learning paradigm in rodents (here Mongolian gerbils; Meriones unguiculatus) in combination with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical electrophysiological in vivo recordings. The detailed protocol is applicable to study multiple aspects of learning behavior and perception in different rodent species.
Site-specific ICMS of auditory cortical circuits as conditioned stimuli here is used as a tool to test the perceptual relevance of specific afferent, efferent and intracortical connections. Distinct activation patterns can be evoked by using different stimulation electrode arrays for local, layer-dependent ICMS or distant ICMS sites. Utilizing behavioral signal detection analysis it can be determined which stimulation strategy is most effective for eliciting a behaviorally detectable and salient signal. Further, parallel multichannel-recordings using different electrode designs (surface electrodes, depth electrodes, etc.) allow for investigating neuronal observables over the time course of such learning processes. It will be discussed how changes of the behavioral design can increase the cognitive complexity (e.g. detection, discrimination, reversal learning).

Shuttle-box avoidance learning is well-established in behavioral neuroscience. This protocol describes how shuttle-box learning in rodents can be combined with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical in vivo recordings as a tool to study multiple aspects of learning and perception.

Shuttle-box avoidance learning is a well-established method in behavioral neuroscience and experimental setups were traditionally custom-made; the ...

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 ...

Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach

Acute animal preparations have been used in research prospectively investigating electrode designs and stimulation techniques for integration into neural auditory prostheses, such as auditory brainstem implants1-3 and auditory midbrain implants4,5. While acute experiments can give initial insight to the effectiveness of the implant, testing the chronically implanted and awake animals provides the advantage of examining the psychophysical properties of the sensations induced using implanted devices6,7.
Several techniques such as reward-based operant conditioning6-8, conditioned avoidance9-11, or classical fear conditioning12 have been used to provide behavioral confirmation of detection of a relevant stimulus attribute. Selection of a technique involves balancing aspects including time efficiency (often poor in reward-based approaches), the ability to test a plurality of stimulus attributes simultaneously (limited in conditioned avoidance), and measure reliability of repeated stimuli (a potential constraint when physiological measures are employed).
Here, a classical fear conditioning behavioral method is presented which may be used to simultaneously test both detection of a stimulus, and discrimination between two stimuli. Heart-rate is used as a measure of fear response, which reduces or eliminates the requirement for time-consuming video coding for freeze behaviour or other such measures (although such measures could be included to provide convergent evidence). Animals were conditioned using these techniques in three 2-hour conditioning sessions, each providing 48 stimulus trials. Subsequent 48-trial testing sessions were then used to test for detection of each stimulus in presented pairs, and test discrimination between the member stimuli of each pair. 
This behavioral method is presented in the context of its utilisation in auditory prosthetic research. The implantation of electrocardiogram telemetry devices is shown. Subsequent implantation of brain electrodes into the Cochlear Nucleus, guided by the monitoring of neural responses to acoustic stimuli, and the fixation of the electrode into place for chronic use is likewise shown.

The application of a classical fear conditioning behavioral paradigm for auditory prosthetic research in rats is described. This paradigm provides a mechanism for identifying both detection of, and discrimination between, distinct acoustic and electrical stimuli using heart-rate as an outcome measure.

Acute animal preparations have been used in research prospectively investigating electrode designs and stimulation techniques for integration into neural ...

Development of an Audio-based Virtual Gaming Environment to Assist with Navigation Skills in the Blind

Audio-based Environment Simulator (AbES) is virtual environment software designed to improve real world navigation skills in the blind. Using only audio based cues and set within the context of a video game metaphor, users gather relevant spatial information regarding a building's layout. This allows the user to develop an accurate spatial cognitive map of a large-scale three-dimensional space that can be manipulated for the purposes of a real indoor navigation task. After game play, participants are then assessed on their ability to navigate within the target physical building represented in the game. Preliminary results suggest that early blind users were able to acquire relevant information regarding the spatial layout of a previously unfamiliar building as indexed by their performance on a series of navigation tasks. These tasks included path finding through the virtual and physical building, as well as a series of drop off tasks. We find that the immersive and highly interactive nature of the AbES software appears to greatly engage the blind user to actively explore the virtual environment. Applications of this approach may extend to larger populations of visually impaired individuals.

Audio-based Environment Simulator (AbES) is virtual environment software designed to improve real world navigation skills in the blind.

Audio-based Environment Simulator (AbES) is virtual environment software designed to improve real world navigation skills in the blind. Using only audio ...

Medicine

EEG Study on Recognizing Familiar Speakers in Expressive Speech

Memorization-Based Training and Testing Paradigm for Robust Vocal Identity Recognition in Expressive Speech Using Event-Related Potentials Analysis

Recognizing familiar speakers from vocal streams is a fundamental aspect of human verbal communication. However, it remains unclear how listeners can still discern the speaker's identity in expressive speech. This study develops a memorization-based individual speaker identity recognition approach and an accompanying electroencephalogram (EEG) data analysis pipeline, which monitors how listeners recognize familiar speakers and tell unfamiliar ones apart. EEG data captures online cognitive processes during new versus old speaker distinction based on voice, offering a real-time measure of brain activity, overcoming limits of reaction times and accuracy measurements. The paradigm comprises three steps: listeners establish associations between three voices and their names (training); listeners indicate the name corresponding to a voice from three candidates (checking); listeners distinguish between three old and three new speaker voices in a two-alternative forced-choice task (testing). The speech prosody in testing was either confident or doubtful. EEG data were collected using a 64-channel EEG system, followed by preprocessing and imported into RStudio for ERP and statistical analysis and MATLAB for brain topography. Results showed an enlarged late positive component (LPC) was elicited in the old-talker compared to the new-talker condition in the 400-850 ms window in the Pz and other wider range of electrodes in both prosodies. Yet, the old/new effect was robust in central and posterior electrodes for doubtful prosody perception, whereas the anterior, central, and posterior electrodes are for confident prosody condition. This study proposes that this experiment design can serve as a reference for investigating speaker-specific cue-binding effects in various scenarios (e.g., anaphoric expression) and pathologies in patients like phonagnosia.

Author Spotlight: Investigating the Impact of Emotional Prosodies on Voice Recognition and Perception

The study introduces a training-testing paradigm to investigate old/new effects of event-related potentials in confident and doubtful prosodic scenarios. Data reveals an enhanced late positive component between 400-850 ms at Pz and other electrodes. This pipeline can explore factors beyond speech prosody and their influence on cue-binding target identification.

Recognizing familiar speakers from vocal streams is a fundamental aspect of human verbal communication. However, it remains unclear how listeners can ...

Sound Source Localization Testing in Single-sided Deafness Following Bone Conduction Intervention

Single-sided deafness (SSD), where there is severe to profound hearing loss in one ear and normal hearing in the other, is a prevalent auditory condition that significantly impacts the quality of life for those affected. The ability to accurately localize sound sources is crucial for various everyday activities, including speech communication and environmental awareness. In recent years, bone conduction intervention has emerged as a promising solution for patients with SSD, offering a non-invasive alternative to traditional air conduction hearing aids. However, the effectiveness of bone conduction devices (BCDs), especially in terms of improving sound localization abilities, remains a topic of considerable interest.
Here, we present a protocol to assess the impact of bone conduction intervention on sound localization ability in patients with SSD. The protocol includes the experimental setup (a sound-treated room and a semicircular array of loudspeakers), stimuli, and data analysis methods. Participants indicate the perceived direction of noise bursts, and their responses are analyzed using root mean square error (RMSE) and bias. The results of sound localization testing before and after bone conduction intervention are reported and compared. Despite no significant differences, most patients (71%) had a localization bias clearly toward the intervention side after bone conduction intervention. The study concludes that bone conduction intervention can promptly enhance certain sound localization skills in patients with SSD, offering evidence to support the efficacy of BCDs as a treatment for SSD.

We present a protocol to evaluate the impact of bone conduction intervention on sound localization ability in patients with single-sided deafness (SSD). This protocol can be applied to assess the efficacy of bone conduction devices in restoring sound localization abilities and improving the overall quality of life for individuals with SSD.

Single-sided deafness (SSD), where there is severe to profound hearing loss in one ear and normal hearing in the other, is a prevalent auditory condition ...

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 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 ...

Assessment and Communication for People with Disorders of Consciousness

In this experiment, we demonstrate a suite of hybrid Brain-Computer Interface (BCI)-based paradigms that are designed for two applications: assessing the level of consciousness of people unable to provide motor response and, in a second stage, establishing a communication channel for these people that enables them to answer questions with either &#39;yes&#39; or &#39;no&#39;. The suite of paradigms is designed to test basic responses in the first step and to continue to more comprehensive tasks if the first tests are successful. The latter tasks require more cognitive functions, but they could provide communication, which is not possible with the basic tests. All assessment tests produce accuracy plots that show whether the algorithms were able to detect the patient&#39;s brain&#39;s response to the given tasks. If the accuracy level is beyond the significance level, we assume that the subject understood the task and was able to follow the sequence of commands presented via earphones to the subject. The tasks require users to concentrate on certain stimuli or to imagine moving either the left or right hand. All tasks are designed around the assumption that the user is unable to use the visual modality, and thus, all stimuli presented to the user (including instructions, cues, and feedback) are auditory or tactile.

With this experiment, one might be able to detect consciousness in people with disorders of consciousness. Furthermore, the approach can create a simple communication channel that enables people to give simple YES/NO answers to questions.

In this experiment, we demonstrate a suite of hybrid Brain-Computer Interface (BCI)-based paradigms that are designed for two applications: assessing the ...

Cochlear Implant Surgery and Electrically-evoked Auditory Brainstem Response Recordings in C57BL/6 Mice

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of hearing. Improvement of the implant technology is needed if CI users are to perceive music and perform in more natural environments, such as hearing out a voice with competing talkers, reflections, and other sounds. Such improvement requires experimental animals to better understand the mechanisms of electric stimulation in the cochlea and its responses in the whole auditory system. The mouse is an increasingly attractive model due to the many genetic models available. However, the limited use of this species as a CI model is mainly due to the difficulty of implanting small electrode arrays. More details about the surgical procedure are therefore of great interest to expand the use of mice in CI research.
In this report, we describe in detail the protocol for acute deafening and cochlear implantation of an electrode array in the C57BL/6 mouse strain. We demonstrate the functional efficacy of this procedure with electrically-evoked auditory brainstem response (eABR) and show examples of facial nerve stimulation. Finally, we also discuss the importance of including a deafening procedure when using a normally hearing animal. This mouse model provides a powerful opportunity to study genetic and neurobiological mechanisms that would be of relevance for CI users.

Animal models of cochlear implants can advance knowledge of the technological bases of treating permanent sensorineural hearing loss with electrical stimulation. This study presents a surgical protocol for acute deafening and cochlear implantation of an electrode array in mice as well as the functional assessment with auditory brainstem response.

Cochlear implants (CIs) are neuroprosthetic devices that can provide a sense of hearing to deaf people. However, a CI cannot restore all aspects of ...

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

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