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

Summary

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.

Abstract

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.

Introduction

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's surr....

Protocol

The study was reviewed and approved by the Neuroscience Institute'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

1. Stimulus preparation
   1. 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, ....

Results

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 .......

Discussion

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.

Materials

Name	Company	Catalog Number	Comments
Audacity	Audacity team	audacityteam.org	Free, open source, cross-platform audio editing software
Audiometer	Resonance	r17a
EEG analysis Software	Neuronic , S.A.
EEG recording Software	Neuronic , S.A.
Electro-Cap	Electro-cap International, Inc.	E1-M	Cap with 19 active electrodes, adjustable straps and chest harness.
Electro-gel	Electro-cap International, Inc.
External computer speakers
Freesound	Music technology group	freesound.org	Database of Creative Commons Licensed sounds
Hook and loop fastner	Velcro
IBM SPSS (Statistical Package for th Social Sciences)	IBM
Individual electrodes	Cadwell		Gold Cup, 60 in
MEDICID-5	Neuronic, S.A.		EEG recording equipment (includes amplifier and computer).
Nuprep	Weaver and company		ECG & EEG abrasive skin prepping gel
Portable computer with touch screen	Dell
SEVITAC-D	Centro Camac, Argentina. Patented by Luis Campos (2002).	http://sevitac-d.com.ar/	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.
Stimulus presentation Software Mindtracer	Neuronics, S.A.
Stimulation computer monitor and keyboard
Tablet computer	Lenovo
Ten20 Conductive Neurodiagnostic Electrode paste	weaver and company