The time course of auditory perceptual learning: neurophysiological changes during speech-sound training

Influence of monaural auditory stimulation combined with music on brain activity

Introduction

Recently, the increasing attention to mental states and psychophysical health has fueled the research into methods that can aid in relaxation and recovery. Traditional methods like meditation and sauna, while effective, have their limitations; thus, the need for more accessible and convenient alternatives.

Methods

Our innovative approach combines monaural beats with music, attempting to replicate the relaxing effects of a sauna in the auditory domain.

Results

In comparison to normal music and silent condition, the power of the theta active band significantly increased when listening to our modified music. Furthermore, after listening to modified music, there was a significant increase in mismatch negativity (MMN) amplitude in the oddball task. Additionally, participants' subjective responses to a questionnaire indicated significant changes in body relaxation and other metrics after listening to the processed music.

Discussion

This state is considered similar to the "totonou" state, which manifests in physical and mental feelings of relaxation, pleasure, and mental clarity in the sauna. Thus, the present research proposes a convenient method for achieving relaxation, opening an avenue for individuals to customize their "totonou" music based on personal preferences.

A study on neural changes induced by sauna bathing: Neural basis of the "totonou" state

Saunas are becoming increasingly popular worldwide, being an activity that promotes relaxation and health. Intense feelings of happiness have been reported shortly after enjoying a hot sauna and cold water, what is known in Japan as the "totonou" state. However, no research has investigated what occurs in the brain during the "totonou" state. In the present study, participants underwent a sauna phase, consisting of three sets of alternating hot sauna, cold water, and rest. We elucidated changes in brain activity and mood in the "totonou" state by measuring and comparing brain activity and emotional scales before and after the sauna phase and during the rest phase in each set. We found significant increases in theta and alpha power during rest and after the sauna phase compared to before the sauna phase. Moreover, in an auditory oddball task, the p300 amplitude decreased significantly and MMN amplitude increased significantly after the sauna phase. The increase in MMN indicates higher activation of the pre-attentional auditory process, leading to a decrease in attention-related brain activity P300. Hence, the brain reaches in a more efficient state. Further, the response time in behavioral tasks decreased significantly. In addition, the participants' subjective responses to the questionnaire showed significant changes in physical relaxation and other indicators after being in the sauna. Finally, we developed an artificial intelligence classifier, obtaining an average accuracy of brain state classification of 88.34%. The results have potential for future application.

Atypical Neural Plasticity and Behavioral Effects of Trustworthiness Learning in Borderline Personality Disorder Features

This study distinguishes interpersonal trust learning with a novel trust learning paradigm in participants high (H-BPD) and low (L-BPD) in BPD features. Neutral faces were paired with trust-relevant behaviors in four conditions: trustworthy, untrustworthy, ambiguously trustworthy, and mixed trustworthiness. After training, participants rated faces on untrustworthiness as electroencephalographic measures were recorded. H-BPD rated neutral faces as significantly more untrustworthy than L-BPD at both time periods. Negative and ambiguous trustworthiness pairing conditions led to higher ratings of untrustworthiness, whereas trustworthy and mixed descriptors led to lower ratings of untrustworthiness. Learning enhanced the amplitude of an early sensory event-related potential (ERP) component (i.e., P1) for both groups. The slow-wave ERP, an index of sustained attention, revealed greater focus after learning to trustworthy descriptors in H-BPD and to untrustworthy descriptors in L-BPD. H-BPD utilized greater effort to overcome an inherent mistrust bias and L-BPD to overcome unexpected untrustworthy information.

Benefits of intervention in the Central Auditory Nervous System in individuals with Neurofibromatosis Type 1

OBJECTIVE

To verify the effectiveness of acoustically controlled auditory training in individuals with Neurofibromatosis Type 1.

METHODS

The sample consisted of individuals with Neurofibromatosis Type 1, randomly distributed into two groups, making up the intervention group: individuals undergoing formal auditory training; and the comparison group: individuals who were not submitted to the intervention. Behavioral assessment of central auditory processing and electrophysiological evaluation, composed by Brainstem Auditory Evoked Potential and Long Latency-P300 Auditory Evoked Potential, were evaluated in three moments of evaluations: initial evaluation, reevaluation and after four months of reevaluation and comparing the performance between the groups.

RESULTS

Better performances in central auditory processing were observed after the formal auditory training in the intervention group with significant differences between the evaluations and performance maintenance four months after the end of the training. Significant differences were observed between the groups in the evaluations after the intervention. The electrophysiological evaluation shows unsystematic variation in the short latency potentials and changes in the long latency potentials with the appearance of the P3 wave after the intervention. The behavioral and electrophysiological evaluation in group that was not submitted to the intervention demonstrated that there is no improvement without the intervention, with deterioration of performance. Significant differences were observed in the behavioral and electrophysiological evaluations, in favor of the group submitted to formal auditory training.

CONCLUSIONS

Formal auditory training is effective in rehabilitation in individuals with Neurofibromatosis Type 1.

DESCRIPTORS/KEYWORDS

Neurofibromatosis 1; Hearing Disorders; Auditory Perceptual Disorders; Acoustic Stimulation; Evoked Potentials, Auditory.

Non-game like training benefits spoken foreign-language processing in children with dyslexia

Children with dyslexia often face difficulties in learning foreign languages, which is reflected as weaker neural activation. However, digital language-learning applications could support learning-induced plastic changes in the brain. Here we aimed to investigate whether plastic changes occur in children with dyslexia more readily after targeted training with a digital language-learning game or similar training without game-like elements. We used auditory event-related potentials (ERPs), specifically, the mismatch negativity (MMN), to study learning-induced changes in the brain responses. Participants were 24 school-aged Finnish-speaking children with dyslexia and 24 age-matched typically reading control children. They trained English speech sounds and words with “Say it again, kid!” (SIAK) language-learning game for 5 weeks between ERP measurements. During the game, the players explored game boards and produced English words aloud to score stars as feedback from an automatic speech recognizer. To compare the effectiveness of the training type (game vs. non-game), we embedded in the game some non-game levels stripped of all game-like elements. In the dyslexia group, the non-game training increased the MMN amplitude more than the game training, whereas in the control group the game training increased the MMN response more than the non-game training. In the dyslexia group, the MMN increase with the non-game training correlated with phonological awareness: the children with poorer phonological awareness showed a larger increase in the MMN response. Improved neural processing of foreign speech sounds as indicated by the MMN increase suggests that targeted training with a simple application could alleviate some spoken foreign-language learning difficulties that are related to phonological processing in children with dyslexia.

Test-retest reliability of electroencephalographic and magnetoencephalographic measures elicited during language tasks: A literature review

Electroencephalographic (EEG) and magnetoencephalographic (MEG) recordings during language processing can provide relevant insights on neuroplasticity in clinical populations (including patients with aphasia). To use EEG and MEG in a longitudinal way, the outcome measures should be consistent across time in healthy individuals. Therefore, the current study provides a review on the test-retest reliability of EEG and MEG measures elicited during language paradigms in healthy adults. PubMed, Web of Science and Embase were searched for relevant articles based on specific eligibility criteria. In total, 11 articles were included in this literature review. The test-retest reliability of the P1, N1 and P2 is systematically considered to be satisfactory, whereas findings are more variable for event-related potentials/fields occurring later in time. The within subject consistency of EEG and MEG measures during language processing can be influenced by multiple variables such as the stimulus presentation mode, the offline reference choice and the required amount of cognitive resources during the task. To conclude, most of the available results are favourable regarding the longitudinal use of EEG and MEG measures elicited during language paradigms in healthy young individuals. In view to the use of these techniques in patients with aphasia, future research should focus on whether the same findings apply to different age groups.

Plasticity Changes in Central Auditory Systems of School-Age Children Following a Brief Training With a Remote Microphone System

OBJECTIVES

The objective of this study was to investigate whether a brief speech-in-noise training with a remote microphone (RM) system (favorable listening condition) would contribute to enhanced post-training plasticity changes in the auditory system of school-age children.

DESIGN

Before training, event-related potentials (ERPs) were recorded from 49 typically developing children, who actively identified two syllables in quiet and in noise (+5 dB signal-to-noise ratio [SNR]). During training, children completed the same syllable identification task as in the pre-training noise condition, but received feedback on their performance. Following random assignment, half of the sample used an RM system during training (experimental group), while the other half did not (control group). That is, during training' children in the experimental group listened to a more favorable speech signal (+15 dB SNR) than children from the control group (+5 dB SNR). ERPs were collected after training at +5 dB SNR to evaluate the effects of training with and without the RM system. Electrical neuroimaging analyses quantified the effects of training in each group on ERP global field power (GFP) and topography, indexing response strength and network changes, respectively. Behavioral speech-perception-in-noise skills of children were also evaluated and compared before and after training. We hypothesized that training with the RM system (experimental group) would lead to greater enhancement of GFP and greater topographical changes post-training than training without the RM system (control group). We also expected greater behavioral improvement on the speech-perception-in-noise task when training with than without the RM system.

RESULTS

GFP was enhanced after training only in the experimental group. These effects were observed on early time-windows corresponding to traditional P1-N1 (100 to 200 msec) and P2-N2 (200 to 400 msec) ERP components. No training effects were observed on response topography. Finally, both groups increased their speech-perception-in-noise skills post-training.

CONCLUSIONS

Enhanced GFP after training with the RM system indicates plasticity changes in the neural representation of sound resulting from listening to an enriched auditory signal. Further investigation of longer training or auditory experiences with favorable listening conditions is needed to determine if that results in long-term speech-perception-in-noise benefits.

Event-Related Potential Correlates of Learning to Produce Novel Foreign Phonemes

Learning to pronounce a foreign phoneme requires an individual to acquire a motor program that enables the reproduction of the new acoustic target sound. This process is largely based on the use of auditory feedback to detect pronunciation errors to adjust vocalization. While early auditory evoked neural activity underlies automatic detection and adaptation to vocalization errors, little is known about the neural correlates of acquiring novel speech targets. To investigate the neural processes that mediate the learning of foreign phoneme pronunciation, we recorded event-related potentials when participants (N = 19) pronounced native or foreign phonemes. Behavioral results indicated that the participants' pronunciation of the foreign phoneme improved during the experiment. Early auditory responses (N1 and P2 waves, approximately 85-290 ms after the sound onset) revealed no differences between foreign and native phonemes. In contrast, the amplitude of the frontocentrally distributed late slow wave (LSW, 320-440 ms) was modulated by the pronunciation of the foreign phonemes, and the effect changed during the experiment, paralleling the improvement in pronunciation. These results suggest that the LSW may reflect higher-order monitoring processes that signal successful pronunciation and help learn novel phonemes.

Before perceptual narrowing: The emergence of the native sounds of language

The present study investigates the precursors of representations of phonemes in 4.5-month-olds. The emergence of phonemes has been mainly studied within the framework of perceptual narrowing, that is, infants tuning to their native language and losing sensitivity to non-native speech. One of the mechanisms behind this phenomenon is distributional learning. In this article, we tested the preference of 4.5-month-old infants using lists of pseudowords that resemble the vowel distribution of the native or a non-native language. We found that infants prefer listening to the lists mirroring the native language. The results suggest that infants can extract vowel information from novel stimuli, and they can map it on pre-existing knowledge on vowels that leads to a preference for the native lists.

Evaluating the Effectiveness of a New Auditory Training Program on the Speech Recognition Skills and Auditory Event-Related Potentials in Elderly Hearing Aid Users

<b><i>Introduction:</i></b> The objective of this study was to evaluate the effectiveness of a new auditory training (AT) program on the speech recognition in the noise and on the auditory event-related potentials in elderly hearing aid users. <b><i>Methods:</i></b> Thirty-three elderly individuals using hearing aids aged from 60 to 80 years participated. A new AT program was developed for the study. AT program lasts for 8 weeks and includes sound discrimination exercises and cognitive exercises. Seventeen individuals (mean age 72.17 ± 6.94) received AT and 16 individuals (mean age 71.75 ± 6.81) did not receive AT. The mismatch negativity (MMN) test and matrix test were used to evaluate the effectiveness of AT. Tests were conducted for the study group before and after the AT. The tests were carried out for the control group at the same times with the study group and the results were compared. <b><i>Results:</i></b> In comparison with the first evaluation, the last evaluation of the study group demonstrated a significant difference regarding the decrease of mean latency in the MMN wave (<i>p</i> = 0.038), and regarding the improving score of matrix test (<i>p</i> = 0.004), there was no difference in the control group. <b><i>Conclusion:</i></b> The AT program prepared for the study was effective in improving speech recognition in noise in the elderly, and the efficiency of AT could be demonstrated with MMN and matrix test.

A preliminary randomized, controlled trial of executive function training for children with autism spectrum disorder

LAY ABSTRACT

Executive function, which is a set of thinking skills that includes stopping unwanted responses, being flexible, and remembering information needed to solve problems, is a challenge for many children on the autism spectrum. This study tested whether executive function could be improved with a computerized executive function training program under the guidance of a coach who reinforced the use of executive function skills. Seventy children with autism spectrum disorder from age 7 to 11 years of age participated in the study. They were randomly assigned to receive training or to a waiting group. The tests most likely to determine whether the training may be effective were chosen from a larger battery before the study started and included one task measuring brain responses, two measures of executive function in the lab, and a parent questionnaire. Changes in social functioning and repetitive behaviors were also explored. All children assigned to training completed the program and families generally reported the experience was positive. Brain responses of the training group changed following training, but not within the waiting group during a similar time period. Children who received training did not exhibit behavioral changes during the two the lab-based tasks. Parent report on questionnaires indicated that neither group showed a significant change in their broad use of executive function in other settings. Yet, children who received training were reported to have fewer restricted and repetitive behaviors following training. These initial findings suggest that short executive function training activities are feasible and may improve some functioning of school-aged children on the autism spectrum.

Electrophysiological and behavioral indicators of musical knowledge about unfamiliar music

Most listeners possess sophisticated knowledge about the music around them without being aware of it or its intricacies. Previous research shows that we develop such knowledge through exposure. This knowledge can then be assessed using behavioral and neurophysiological measures. It remains unknown however, which neurophysiological measures accompany the development of musical long-term knowledge. In this series of experiments, we first identified a potential ERP marker of musical long-term knowledge by comparing EEG activity following musically unexpected and expected tones within the context of known music (n = 30). We then validated the marker by showing that it does not differentiate between such tones within the context of unknown music (n = 34). In a third experiment, we exposed participants to unknown music (n = 40) and compared EEG data before and after exposure to explore effects of time. Although listeners’ behavior indicated musical long-term knowledge, we did not find any effects of time on the ERP marker. Instead, the relationship between behavioral and EEG data suggests musical long-term knowledge may have formed before we could confirm its presence through behavioral measures. Listeners are thus not only knowledgeable about music but seem to also be incredibly fast music learners.

Changes in cortical auditory evoked potentials in response to auditory training in elderly hearing aid users: A pilot study

OBJECTIVE

To compare the cortical auditory evoked potential responses pre-and post-Auditory Musical Training associated with hearing aid adaptation in elderly people with presbycusis.

DESIGN

This is a pilot, prospective, randomized, single-blind study.

STUDY SAMPLE

Eight presbiacusis elderly people between 65 and 80 years, new hearing aid users, divided into two groups participated in the study: Hearing Aid Group: use of hearing aid; and Auditory Training Group: use of hearing aid in addition to musical auditory training for 16 sessions. All participants were submitted to cortical auditory evoked potential tests with verbal stimulation in two different moments: Initial assessment, carried out before hearing aid adaptation and auditory training, and after three months, final assessment at the end of the auditory training sessions. All participants were adapted bilaterally with digital mini hearing aids.

RESULTS

There was a decrease in the P3a latency component for the Auditory Training Group when initial and final assessment were compared.

CONCLUSION

There was a change in the cortical auditory evoked potential in elderly people with presbycusis in response to the Musical Auditory Training associated with the use of hearing aids in elderly people with presbycusis.

Neural responses in novice learners' perceptual learning and generalization of lexical tones: The effect of training variability

The acoustics of lexical tones are highly variable across talkers, and require second-language (L2) learners' flexibility in accommodating talker-specific tonal variations for successful learning. This study investigated how tone training with high vs. low talker-variability modulated novice learners' neural responses to non-native tones. A passive oddball paradigm tested Mandarin-speaking participants' neural responses to Cantonese low-high and low-mid tonal contrasts in the pretest and posttest. Participants were trained using a tone identification task with feedback, either with high or low talker-variability. The results of mismatch negativity (MMN) showed no group difference in the pretest whereas the high-variability group demonstrated greater neural sensitivity to the low-high tonal contrast produced by a novel talker and a trained talker in the posttest. The finding provides (tentative) novel evidence that training variability may benefit perceptual learning of the relatively easy tone pair and facilitate the formation of talker-independent representations of non-native tones by novice learners.

Newborns' neural processing of native vowels reveals directional asymmetries

Prenatal learning of speech rhythm and melody is well documented. Much less is known about the earliest acquisition of segmental speech categories. We tested whether newborn infants perceive native vowels, but not nonspeech sounds, through some existing (proto-)categories, and whether they do so more robustly for some vowels than for others. Sensory event-related potentials (ERP), and mismatch responses (MMR), were obtained from 104 neonates acquiring Czech. The ERPs elicited by vowels were larger than the ERPs to nonspeech sounds, and reflected the differences between the individual vowel categories. The MMRs to changes in vowels but not in nonspeech sounds revealed left-lateralized asymmetrical processing patterns: a change from a focal [a] to a nonfocal [ɛ], and the change from short [ɛ] to long [ɛ:] elicited more negative MMR responses than reverse changes. Contrary to predictions, we did not find evidence of a developmental advantage for vowel length contrasts (supposedly most readily available in utero) over vowel quality contrasts (supposedly less salient in utero). An explanation for these asymmetries in terms of differential degree of prior phonetic warping of speech sounds is proposed. Future studies with newborns with different language backgrounds should test whether the prenatal learning scenario proposed here is plausible.

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Newborns’ processing of native vowels and comparable nonspeech sounds differ.

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Durational and spectral differences in stimuli were more clearly reflected by the ERPs to vowels, compared to tone complexes.

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Directional asymmetries were detected in the mismatch responses to vowel deviants.

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In the left hemisphere, a change in vowels from focal to nonfocal and from short to long resulted in a more negative MMR.

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The findings may be explained by phonetic learning prior to the 3rd day after birth.

Differential effects of long-term aerobic versus cognitively-engaging physical activity on children's visuospatial working memory related brain activation: A cluster RCT

Different types of physical activity are thought to differentially affect children's brain activation, via physiological mechanisms, or by activating similar brain areas during physical and cognitive tasks. Despite many behavioral studies relying on these mechanisms, they have been rarely studied. This study looks at both mechanisms simultaneously, by examining effects of two physical activity interventions (aerobic vs. cognitively-engaging) on children's brain activation. Functional Magnetic Resonance Imaging (fMRI) data of 62 children (48.4% boys, mean age 9.2 years) was analyzed. Children's visuospatial working memory related brain activity patterns were tested using a Spatial Span Task before and after the 14-week interventions consisting of four physical education lessons per week. The control group followed their regular program of two lessons per week. Analyses of activation patterns in SPM 12.0 revealed no activation changes between pretest and posttest (p > .05), and no differences between the three conditions in pretest-posttest changes in brain activation (p > .05). Large inter-individual differences were found, suggesting that not every child benefited from the interventions in the same way. To get more insight into the assumed mechanisms, further research is needed to understand whether, when, for whom, and how physical activity results in changed brain activation patterns.

First Language Attrition: What It Is, What It Isn't, and What It Can Be

This review aims at clarifying the concept of first language attrition by tracing its limits, identifying its phenomenological and contextual constraints, discussing controversies associated with its definition, and suggesting potential directions for future research. We start by reviewing different definitions of attrition as well as associated inconsistencies. We then discuss the underlying mechanisms of first language attrition and review available evidence supporting different background hypotheses. Finally, we attempt to provide the groundwork to build a unified theoretical framework allowing for generalizable results. To this end, we suggest the deployment of a rigorous neuroscientific approach, in search of neural markers of first language attrition in different linguistic domains, putting forward hypothetical experimental ways to identify attrition's neural traces and formulating predictions for each of the proposed experimental paradigms.

Behavioral effect of mismatch negativity neurofeedback on foreign language learning

Listening is critical for foreign language learning. Listening difficulties can occur because of an inability to perceive or recognize sounds while listening to speech, whereas successful listening can boost understanding and improve speaking when learning a foreign language. Previous studies in our laboratory revealed that EEG-neurofeedback (NF) using mismatch negativity event-related brain potential successfully induced unconscious learning in terms of auditory discrimination of speech sounds. Here, we conducted a feasibility study with a small participant group (NF group and control group; six participants each) to examine the practical effects of mismatch negativity NF for improving the perception of speech sounds in a foreign language. Native Japanese speakers completed a task in which they learned to perceive and recognize spoken English words containing the consonants "l" or "r". Participants received neurofeedback training while not explicitly attending to auditory stimuli. The results revealed that NF training significantly improved the proportion of correct in discrimination and recognition trials, even though the training time for each word pair was reduced to 20% of the training time reported in our previous study. The learning effect was not affected by training with three pairs of words with different vowels. The current results indicate that NF resulted in long-term learning that persisted for at least 2 months.

Cortical plasticity elicited by acoustically cued monetary losses: an ERP study

Both human and animal studies have demonstrated remarkable findings of experience-induced plasticity in the cortex. Here, we investigated whether the widely used monetary incentive delay (MID) task changes the neural processing of incentive cues that code expected monetary outcomes. We used a novel auditory version of the MID task, where participants responded to acoustic cues that coded expected monetary losses. To investigate task-induced brain plasticity, we presented incentive cues as deviants during passive oddball tasks before and after two sessions of the MID task. During the oddball task, we recorded the mismatch-related negativity (MMN) as an index of cortical plasticity. We found that two sessions of the MID task evoked a significant enhancement of MMN for incentive cues that predicted large monetary losses, specifically when monetary cue discrimination was essential for maximising monetary outcomes. The task-induced plasticity correlated with the learning-related neural activity recorded during the MID task. Thus, our results confirm that the processing of (loss)incentive auditory cues is dynamically modulated by previously learned monetary outcomes.

Subjective and Objective Assessments of Post-traumatic Olfactory Dysfunction

Introduction: Traumatic brain injuries are the most common cause of olfactory dysfunction. Deficits in olfaction may be conductive or neurosensory in nature, with varying degrees of impairment resulting in a diminished quality of life and an increased risk for personal injury among patients. The aim of this research is to evaluate the results of the subjective and objective quantitative examinations of olfactory function in a group of patients with post-traumatic anosmia in order to predict its value in identifying olfactory deficits in clinical practice.

Materials and Methods: The present study included 38 patients who reported anosmia or hyposmia caused by a traumatic head injury, and a group of 31 age- and sex-matched controls without olfactory dysfunction or prior history of head injury. The comparison of odor perception and identification of two oils (mint and anise) was assessed with the use of blast olfactometry with cortical olfactory event-related potentials.

Results: Subjective olfactory tests revealed anosmia or hyposmia in 94% of patients with head injury-related olfactory dysfunction. Objective tests revealed olfactory event-related potentials from cranial nerve I produced by the stimulation with both mint and anise in 20 patients (52.6%). Olfactory event-related potentials from cranial nerve V produced by the stimulation with mint were registered in 26 patients (68.4%). The lack of any responses, from both cranial nerve I and V, was found in 12 patients (32% of cases).

Conclusions: Findings from our study indicate the application of both subjective and objective examinations in the evaluation of patients with olfactory impairment. In the diagnosis of post-traumatic anosmia or hyposmia, objective examinations are particularly useful when the patients' level of cognition may be impaired or when subjects may be exaggerating their olfactory defects for a secondary gain. The diagnosis of damage to the olfactory system, specifically in the receptive part of the olfactory pathway, can be established in patients who showed reduced amplitudes or absent cortical responses in addition to absent odor identification and perception threshold in the subjective examination.

Neural Coding of Syllable-Final Fricatives with and without Hearing Aid Amplification

BACKGROUND

Cortical auditory event-related potentials are a potentially useful clinical tool to objectively assess speech outcomes with rehabilitative devices. Whether hearing aids reliably encode the spectrotemporal characteristics of fricative stimuli in different phonological contexts and whether these differences result in distinct neural responses with and without hearing aid amplification remain unclear.

PURPOSE

To determine whether the neural coding of the voiceless fricatives /s/ and /ʃ/ in the syllable-final context reliably differed without hearing aid amplification and whether hearing aid amplification altered neural coding of the fricative contrast.

RESEARCH DESIGN

A repeated-measures, within subject design was used to compare the neural coding of a fricative contrast with and without hearing aid amplification.

STUDY SAMPLE

Ten adult listeners with normal hearing participated in the study.

DATA COLLECTION AND ANALYSIS

Cortical auditory event-related potentials were elicited to an /ɑs/-/ɑʃ/ vowel-fricative contrast in unaided and aided listening conditions. Neural responses to the speech contrast were recorded at 64-electrode sites. Peak latencies and amplitudes of the cortical response waveforms to the fricatives were analyzed using repeated-measures analysis of variance.

RESULTS

The P2' component of the acoustic change complex significantly differed from the syllable-final fricative contrast with and without hearing aid amplification. Hearing aid amplification differentially altered the neural coding of the contrast across frontal, temporal, and parietal electrode regions.

CONCLUSIONS

Hearing aid amplification altered the neural coding of syllable-final fricatives. However, the contrast remained acoustically distinct in the aided and unaided conditions, and cortical responses to the fricative significantly differed with and without the hearing aid.

The Effect of Visual Articulatory Information on the Neural Correlates of Non-native Speech Sound Discrimination

Behavioral studies have shown that the ability to discriminate between non-native speech sounds improves after seeing how the sounds are articulated. This study examined the influence of visual articulatory information on the neural correlates of non-native speech sound discrimination. English speakers’ discrimination of the Hindi dental and retroflex sounds was measured using the mismatch negativity (MMN) event-related potential, before and after they completed one of three 8-min training conditions. In an audio-visual speech training condition (n = 14), each sound was presented with its corresponding visual articulation. In one control condition (n = 14), both sounds were presented with the same visual articulation, resulting in one congruent and one incongruent audio-visual pairing. In another control condition (n = 14), both sounds were presented with the same image of a still face. The control conditions aimed to rule out the possibility that the MMN is influenced by non-specific audio-visual pairings, or by general exposure to the dental and retroflex sounds over the course of the study. The results showed that audio-visual speech training reduced the latency of the MMN but did not affect MMN amplitude. No change in MMN amplitude or latency was observed for the two control conditions. The pattern of results suggests that a relatively short audio-visual speech training session (i.e., 8 min) may increase the speed with which the brain processes non-native speech sound contrasts. The absence of a training effect on MMN amplitude suggests a single session of audio-visual speech training does not lead to the formation of more discrete memory traces for non-native speech sounds. Longer and/or multiple sessions might be needed to influence the MMN amplitude.

Making Sense of Mismatch Negativity

Evoked potentials provide valuable insight into brain processes that are integral to our ability to interact effectively and efficiently in the world. The mismatch negativity (MMN) component of the evoked potential has proven highly informative on the ways in which sensitivity to regularity contributes to perception and cognition. This review offers a compendium of research on MMN with a view to scaffolding an appreciation for its use as a tool to explore the way regularities contribute to predictions about the sensory environment over many timescales. In compiling this work, interest in MMN as an index of sensory encoding and memory are addressed, as well as attention. Perspectives on the possible underlying computational processes are reviewed as well as recent observations that invite consideration of how MMN relates to how we learn, what we learn, and why.

The Monetary Incentive Delay (MID) Task Induces Changes in Sensory Processing: ERP Evidence

Numerous cognitive studies have demonstrated experience-induced plasticity in the primary sensory cortex, indicating that repeated decisions could modulate sensory processing. In this context, we investigated whether an auditory version of the monetary incentive delay (MID) task could change the neural processing of the incentive cues that code expected monetary outcomes. To study sensory plasticity, we presented the incentive cues as deviants during oddball sessions recorded before and after training in the two MID task sessions. We found that after 2 days of training in the MID task, incentive cues evoked a larger P3a (compared with the baseline condition), indicating there was an enhancement of the involuntary attention to the stimuli that predict rewards. At the individual level, the training-induced change of mismatch-related negativity was correlated with the amplitude of the feedback-related negativity (FRN) recorded during the first MID task session. Our results show that the MID task evokes plasticity changes in the auditory system associated with better passive discrimination of incentive cues and with enhanced involuntary attention switching towards these cues. Thus, the sensory processing of incentive cues is dynamically modulated by previous outcomes.

Literature overview on P3 measurement as an objective measure of auditory performance in post-lingually deaf adults with a cochlear implant

Objective: Cochlear implantation results in restoration of hearing, potential cortical reorganisation and the reallocation of attentional resources to the auditory system. Hence, the distorted cortical activity of patients with profound sensorineural hearing loss may be partially reversed. The measurement of auditory event-related potentials (ERPs) forms a promising electrophysiological evaluation of the central auditory nervous system. In particular, the P3 component is hypothesised to be a differential indicator of subjective auditory discrimination. This overview discusses the association between the cortical P3 component and the performance on auditory tests in post-lingually deaf adults using a CI. Moreover, the current article proposes important guidelines on eliciting, recording and analysing ERPs in CI users.Design: The literature search was conducted in PubMed.Study sample: Articles were included if they focussed on the relationship between P3 and auditory performance of an adult CI population.Results: The higher-order processing of speech in quiet and in noise of adult CI users is correlated with the ERP components, including the P3, shedding light on neurophysiological foundations for auditory performance differences.Conclusions: There is a need for replicating studies with larger sample sizes to fully comprehend the relationship between P3 and the auditory performance of CI users.

Learning of Artificial Sensation Through Long-Term Home Use of a Sensory-Enabled Prosthesis

Upper limb prostheses are specialized tools, and skilled operation is learned by amputees over time. Recently, neural prostheses using implanted peripheral nerve interfaces have enabled advances in artificial somatosensory feedback that can improve prosthesis outcomes. However, the effect of sensory learning on artificial somatosensation has not been studied, despite its known influence on intact somatosensation and analogous neuroprostheses. Sensory learning involves changes in the perception and interpretation of sensory feedback and may further influence functional and psychosocial outcomes. In this mixed methods case study, we examined how passive learning over 115 days of home use of a neural-connected, sensory-enabled prosthetic hand influenced perception of artificial sensory feedback in a participant with transradial amputation. We examined perceptual changes both within individual days of use and across the duration of the study. At both time scales, the reported percept locations became significantly more aligned with prosthesis sensor locations, and the phantom limb became significantly more extended toward the prosthesis position. Similarly, the participant’s ratings of intensity, naturalness, and contact touch significantly increased, while his ratings of vibration and movement significantly decreased across-days for tactile channels. These sensory changes likely resulted from engagement of cortical plasticity mechanisms as the participant learned to use the artificial sensory feedback. We also assessed psychosocial and functional outcomes through surveys and interviews, and found that self-efficacy, perceived function, prosthesis embodiment, social touch, body image, and prosthesis efficiency improved significantly. These outcomes typically improved within the first month of home use, demonstrating rapid benefits of artificial sensation. Participant interviews indicated that the naturalness of the experience and engagement with the prosthesis increased throughout the study, suggesting that artificial somatosensation may decrease prosthesis abandonment. Our data showed that prosthesis embodiment was intricately related to naturalness and phantom limb perception, and that learning the artificial sensation may have modified the body schema. As another indicator of successfully learning to use artificial sensation, the participant reported the emergence of stereognosis later in the study. This study provides the first evidence that artificial somatosensation can undergo similar learning processes as intact sensation and highlights the importance of sensory restoration in prostheses.

Interactions between speech perception and production during learning of novel phonemic categories

A successful language learner must be able to perceive and produce novel sounds in their second language. However, the relationship between learning in perception and production is unclear. Some studies show correlations between the two modalities; however, other studies have not shown such correlations. In the present study, I examine learning in perception and production after training in a distributional learning paradigm. Training modality is manipulated, while testing modality remained constant. Overall, participants showed substantial learning in the modality in which they were trained; however, learning across modalities shows a more complex pattern. Although individuals trained in perception improved in production, individuals trained in production did not show substantial learning in perception. That is, production during training disrupted perceptual learning. Further, correlations between learning in the two modalities were not strong. Several possible explanations for the pattern of results are explored, including a close examination of the role of production variability, and the results are explained using a paradigm appealing to shared cognitive resources. The article concludes with a discussion of the implications of these results for theories of second-language learning, speech perception, and production.

Toward Decoding Selective Attention From Single-Trial EEG Data in Cochlear Implant Users

Previous results showed that it is possible to decode an attended speech source from EEG data via the reconstruction of the speech envelope in normal hearing (NH) listeners. However, so far it is unknown that how the performance of such a decoder is affected by the decrease in spectral resolution and the electrical artifacts introduced by a cochlear implant (CI) in users of these prostheses. NH listeners and bilateral CI users participated in the present study. Speeches from two audio books, one uttered by a male voice and one by a female voice, were presented to NH listeners and CI users. Participants were instructed to attend to one of the two speech streams presented dichotically while a 96-channel EEG was recorded. Speech envelope reconstruction from the EEG data was obtained by training decoders using a regularized least square estimation method. Decoding accuracy was defined as the percentage of accurately reconstructed trials for each subject. For NH listeners, the experiment was repeated using a vocoder to reduce spectral resolution and simulate speech perception with a CI in NH listeners. The results showed a decoding accuracy of 80.9 % using the original sound files in NH listeners. The performance dropped to 73.2 % in the vocoder condition and to 71.5 % in the group of CI users. In sum, although the accuracy drops when the spectral resolution becomes worse, the results show the feasibility to decode the attended sound source in NH listeners with a vocoder simulation, and even in CI users, albeit more training data are needed.

The Cochlear Implant EEG Artifact Recorded From an Artificial Brain for Complex Acoustic Stimuli

Electroencephalographic (EEG) recordings provide objective estimates of listeners' cortical processing of sounds and of the status of their speech perception system. For profoundly deaf listeners with cochlear implants (CIs), the applications of EEG are limited because the device adds electric artifacts to the recordings. This restricts the possibilities for the neural-based metrics of speech processing by CI users, for instance to gauge cortical reorganization due to individual's hearing loss history. This paper describes the characteristics of the CI artifact as recorded with an artificial head substitute, and reports how the artifact is affected by the properties of the acoustical input signal versus the settings of the device.

METHODS

We created a brain substitute using agar that simulates the brain's conductivity, placed it in a human skull, and performed EEG recordings with CIs from three different manufacturers. As stimuli, we used simple and complex non-speech stimuli, as well as naturally produced continuous speech. We examined the effect of manipulating device settings in both controlled experimental CI configurations and real clinical maps.

RESULTS

An increase in the magnitude of the stimulation current through the device settings increases also the magnitude of the artifact. The artifact recorded to speech is smaller in magnitude than for non-speech stimuli due to signal-inherent amplitude modulations.

CONCLUSION

The CI EEG artifact for speech appears more difficult to detect than for simple stimuli. Since the artifact differs across CI users, due to their individual clinical maps, the method presented enables insight into the individual manifestations of the artifact.

Revisiting Stress "Deafness" in European Portuguese - A Behavioral and ERP Study

European Portuguese (EP) is a language with variable stress, and the main cues for stress are duration and vowel reduction. A previous behavioral study has reported a stress “deafness” effect in EP when vowel quality cues are unavailable. The present study recorded both event-related potentials (ERPs) and behavioral data to examine the stress processing by native EP speakers in the absence of the vowel quality cues. Our behavioral result was consistent with previous research, showing that when vowel reduction is absent EP speakers demonstrated a stress “deafness” effect similar to that found in speakers of languages with fixed stress or without any lexical stress marking. In the ERP task, both the trochaic and iambic conditions yielded mismatch negativity (MMN) and late negativity, suggesting that EP speakers are able to discriminate the two stress patterns without vowel reduction at the pre-attentive stage. Moreover, the ERP and behavioral data revealed compatible results regarding the pattern of stress bias in EP. In the EPR task, the MMN and late negativity components were more negative and span over a larger temporal window in the iambic condition than in the trochaic condition, indicating a higher sensitivity for the iambic stress pattern. In the behavioral task, EP speakers responded more accurately and more quickly to the iambic stress. These results match recent developmental findings in the acquisition of stress, but speak against the dominant view in EP phonological literature which assumes penultimate stress to be the regular stress pattern. In addition, both the ERP and the behavioral data showed that EP speakers’ stress processing was influenced by their working memory (WM) capacity. The participants with high WM capacity outperformed the participants with limited WM capacity in the iambic condition. In sum, our results broaden the current knowledge on stress processing by EP speakers at both the pre-attentive and attentive levels.

A perspective on brain-behavior relationships and effects of age and hearing using speech-in-noise stimuli

Understanding speech in background noise is often more difficult for individuals who are older and have hearing impairment than for younger, normal-hearing individuals. In fact, speech-understanding abilities among older individuals with hearing impairment varies greatly. Researchers have hypothesized that some of that variability can be explained by how the brain encodes speech signals in the presence of noise, and that brain measures may be useful for predicting behavioral performance in difficult-to-test patients. In a series of experiments, we have explored the effects of age and hearing impairment in both brain and behavioral domains with the goal of using brain measures to improve our understanding of speech-in-noise difficulties. The behavioral measures examined showed effect sizes for hearing impairment that were 6-10 dB larger than the effects of age when tested in steady-state noise, whereas electrophysiological age effects were similar in magnitude to those of hearing impairment. Both age and hearing status influence neural responses to speech as well as speech understanding in background noise. These effects can in turn be modulated by other factors, such as the characteristics of the background noise itself. Finally, the use of electrophysiology to predict performance on receptive speech-in-noise tasks holds promise, demonstrating root-mean-square prediction errors as small as 1-2 dB. An important next step in this field of inquiry is to sample the aging and hearing impairment variables continuously (rather than categorically) - across the whole lifespan and audiogram - to improve effect estimates.

Two are better than one: Infant language learning from video improves in the presence of peers

Studies show that young children learn new phonemes and words from humans significantly better than from machines. However, it is not clear why learning from video is ineffective or what might be done to improve learning from a screen. The present study, conducted with 9-month-old infants, utilized a manipulation-touch screen video-which allowed infants to control presentations of foreign-language video clips. We tested the hypothesis that infant learning from a screen would be enhanced in the presence of a peer, as opposed to learning alone. Brain measures of phonetic learning and detailed analyses of interaction during learning confirm the hypothesis that social partners enhance learning, even from screens.

Neural Correlates of Selective Attention With Hearing Aid Use Followed by ReadMyQuips Auditory Training Program

OBJECTIVES

The objectives of this study were to investigate the effects of hearing aid use and the effectiveness of ReadMyQuips (RMQ), an auditory training program, on speech perception performance and auditory selective attention using electrophysiological measures. RMQ is an audiovisual training program designed to improve speech perception in everyday noisy listening environments.

DESIGN

Participants were adults with mild to moderate hearing loss who were first-time hearing aid users. After 4 weeks of hearing aid use, the experimental group completed RMQ training in 4 weeks, and the control group received listening practice on audiobooks during the same period. Cortical late event-related potentials (ERPs) and the Hearing in Noise Test (HINT) were administered at prefitting, pretraining, and post-training to assess effects of hearing aid use and RMQ training. An oddball paradigm allowed tracking of changes in P3a and P3b ERPs to distractors and targets, respectively. Behavioral measures were also obtained while ERPs were recorded from participants.

RESULTS

After 4 weeks of hearing aid use but before auditory training, HINT results did not show a statistically significant change, but there was a significant P3a reduction. This reduction in P3a was correlated with improvement in d prime (d') in the selective attention task. Increased P3b amplitudes were also correlated with improvement in d' in the selective attention task. After training, this correlation between P3b and d' remained in the experimental group, but not in the control group. Similarly, HINT testing showed improved speech perception post training only in the experimental group. The criterion calculated in the auditory selective attention task showed a reduction only in the experimental group after training. ERP measures in the auditory selective attention task did not show any changes related to training.

CONCLUSIONS

Hearing aid use was associated with a decrement in involuntary attention switch to distractors in the auditory selective attention task. RMQ training led to gains in speech perception in noise and improved listener confidence in the auditory selective attention task.

Adults with Specific Language Impairment fail to consolidate speech sounds during sleep

Specific Language Impairment (SLI) is a common learning disability that is associated with poor speech sound representations. These differences in representational quality are thought to impose a burden on spoken language processing. The underlying mechanism to account for impoverished speech sound representations remains in debate. Previous findings that implicate sleep as important for building speech representations, combined with reports of atypical sleep in SLI, motivate the current investigation into a potential consolidation mechanism as a source of impoverished representations in SLI. In the current study, we trained individuals with SLI on a new (nonnative) set of speech sounds, and tracked their perceptual accuracy and neural responses to these sounds over two days. Adults with SLI achieved comparable performance to typical controls during training, however demonstrated a distinct lack of overnight gains on the next day. We propose that those with SLI may be impaired in the consolidation of acoustic-phonetic information.

Computer-Based Auditory Training Programs for Children with Hearing Impairment - A Scoping Review

Introduction  Communication breakdown, a consequence of hearing impairment (HI), is being fought by fitting amplification devices and providing auditory training since the inception of audiology. The advances in both audiology and rehabilitation programs have led to the advent of computer-based auditory training programs (CBATPs).

Objective  To review the existing literature documenting the evidence-based CBATPs for children with HIs. Since there was only one such article, we also chose to review the commercially available CBATPs for children with HI. The strengths and weaknesses of the existing literature were reviewed in order to improve further researches.

Data Synthesis  Google Scholar and PubMed databases were searched using various combinations of keywords. The participant, intervention, control, outcome and study design (PICOS) criteria were used for the inclusion of articles. Out of 124 article abstracts reviewed, 5 studies were shortlisted for detailed reading. One among them satisfied all the criteria, and was taken for review. The commercially available programs were chosen based on an extensive search in Google. The reviewed article was well-structured, with appropriate outcomes. The commercially available programs cover many aspects of the auditory training through a wide range of stimuli and activities.

Conclusions  There is a dire need for extensive research to be performed in the field of CBATPs to establish their efficacy, also to establish them as evidence-based practices.

Acoustic Cue Weighting by Adults with Cochlear Implants: A Mismatch Negativity Study

OBJECTIVES

Formant rise time (FRT) and amplitude rise time (ART) are acoustic cues that inform phonetic identity. FRT represents the rate of transition of the formant(s) to a steady state, while ART represents the rate at which the sound reaches its peak amplitude. Normal-hearing (NH) native English speakers weight FRT more than ART during the perceptual labeling of the /ba/-/wa/ contrast. This weighting strategy is reflected neurophysiologically in the magnitude of the mismatch negativity (MMN)-MMN is larger during the FRT than the ART distinction. The present study examined the neurophysiological basis of acoustic cue weighting in adult cochlear implant (CI) listeners using the MMN design. It was hypothesized that individuals with CIs who weight ART more in behavioral labeling (ART users) would show larger MMNs during the ART than the FRT contrast, and the opposite would be seen for FRT users.

DESIGN

Electroencephalography was recorded while 20 adults with CIs listened passively to combinations of 3 synthetic speech stimuli: a /ba/ with /ba/-like FRT and ART; a /wa/ with /wa/-like FRT and ART; and a /ba/ stimulus with /ba/-like FRT and /wa/-like ART. The MMN response was elicited during the FRT contrast by having participants passively listen to a train of /wa/ stimuli interrupted occasionally by /ba/ stimuli, and vice versa. For the ART contrast, the same procedure was implemented using the /ba/ and /ba/ stimuli.

RESULTS

Both ART and FRT users with CIs elicited MMNs that were equal in magnitudes during FRT and ART contrasts, with the exception that FRT users exhibited MMNs for ART and FRT contrasts that were temporally segregated. That is, their MMNs occurred significantly earlier during the ART contrast (~100 msec following sound onset) than during the FRT contrast (~200 msec). In contrast, the MMNs for ART users of both contrasts occurred later and were not significantly separable in time (~230 msec). Interestingly, this temporal segregation observed in FRT users is consistent with the MMN behavior in NH listeners.

CONCLUSIONS

Results suggest that listeners with CIs who learn to classify phonemes based on formant dynamics, consistent with NH listeners, develop a strategy similar to NH listeners, in which the organization of the amplitude and spectral representations of phonemes in auditory memory are temporally segregated.

Neural discrimination of speech sound changes in a variable context occurs irrespective of attention and explicit awareness

To process complex stimuli like language, our auditory system must tolerate large acoustic variance, like speaker variability, and still be sensitive enough to discriminate between phonemes and to detect complex sound relationships in, e.g., prosodic cues. Our study determined discrimination of speech sounds in input mimicking natural speech variability, and detection of deviations in regular pitch relationships (rule violations) between speech sounds. We investigated the automaticity and the influence of attention and explicit awareness on these changes by recording the neurophysiological mismatch negativity (MMN) and P3a as well as task performance from 21 adults. The results showed neural discrimination of phonemes and rule violations as indicated by MMN and P3a, regardless of whether the sounds were attended or not, even when participants could not explicitly describe the rule. While small sample size precluded statistical analysis of some outcomes, we still found preliminary associations between the MMN amplitudes, task performance, and emerging explicit awareness of the rule. Our results highlight the automaticity of processing complex aspects of speech as a basis for the emerging conscious perception and explicit awareness of speech properties. While MMN operates at the implicit processing level, P3a appears to work at the borderline of implicit and explicit.

Is the Role of External Feedback in Auditory Skill Learning Age Dependent?

PURPOSE

The purpose of this study is to investigate the role of external feedback in auditory perceptual learning of school-age children as compared with that of adults.

METHOD

Forty-eight children (7-9 years of age) and 64 adults (20-35 years of age) conducted a training session using an auditory frequency discrimination (difference limen for frequency) task, with external feedback (EF) provided for half of them.

RESULTS

Data supported the following findings: (a) Children learned the difference limen for frequency task only when EF was provided. (b) The ability of the children to benefit from EF was associated with better cognitive skills. (c) Adults showed significant learning whether EF was provided or not. (d) In children, within-session learning following training was dependent on the provision of feedback, whereas between-sessions learning occurred irrespective of feedback.

CONCLUSIONS

EF was found beneficial for auditory skill learning of 7-9-year-old children but not for young adults. The data support the supervised Hebbian model for auditory skill learning, suggesting combined bottom-up internal neural feedback controlled by top-down monitoring. In the case of immature executive functions, EF enhanced auditory skill learning. This study has implications for the design of training protocols in the auditory modality for different age groups, as well as for special populations.

Differences in phonetic discrimination stem from differences in psychoacoustic abilities in learning the sounds of a second language: Evidence from ERP research

The scientific community has been divided as to the origin of individual differences in perceiving the sounds of a second language (L2). There are two alternative explanations: a general psychoacoustic origin vs. a speech-specific one. A previous study showed that such individual variability is linked to the perceivers’ speech-specific capabilities, rather than the perceivers’ psychoacoustic abilities. However, we assume that the selection of participants and parameters of sound stimuli might not appropriate. Therefore, we adjusted the sound stimuli and recorded event-related potentials (ERPs) from two groups of early, proficient Cantonese (L1)-Mandarin (L2) bilinguals who differed in their mastery of the Mandarin (L2) phonetic contrast /in-ing/, to explore whether the individual differences in perceiving L2 stem from participants’ ability to discriminate various pure tones (frequency, duration and pattern). To precisely measure the participants’ acoustic discrimination, mismatch negativity (MMN) elicited by the oddball paradigm was recorded in the experiment. The results showed that significant differences between good perceivers (GPs) and poor perceivers (PPs) were found in the three general acoustic conditions (frequency, duration and pattern), and the MMN amplitude for GP was significantly larger than for PP. Therefore, our results support a general psychoacoustic origin of individual variability in L2 phonetic mastery.

Unconscious improvement in foreign language learning using mismatch negativity neurofeedback: A preliminary study

When people learn foreign languages, they find it difficult to perceive speech sounds that are nonexistent in their native language, and extensive training is consequently necessary. Our previous studies have shown that by using neurofeedback based on the mismatch negativity event-related brain potential, participants could unconsciously achieve learning in the auditory discrimination of pure tones that could not be consciously discriminated without the neurofeedback. Here, we examined whether mismatch negativity neurofeedback is effective for helping someone to perceive new speech sounds in foreign language learning. We developed a task for training native Japanese speakers to discriminate between 'l' and 'r' sounds in English, as they usually cannot discriminate between these two sounds. Without participants attending to auditory stimuli or being aware of the nature of the experiment, neurofeedback training helped them to achieve significant improvement in unconscious auditory discrimination and recognition of the target words 'light' and 'right'. There was also improvement in the recognition of other words containing 'l' and 'r' (e.g., 'blight' and 'bright'), even though these words had not been presented during training. This method could be used to facilitate foreign language learning and can be extended to other fields of auditory and clinical research and even other senses.

Treinamento auditivo acusticamente controlado em um indivíduo adulto após traumatismo cranioencefálico

RESUMO A avaliação eletrofisiológica e comportamental do processamento auditivo tem sido uma importante ferramenta para o diagnóstico e monitoramento terapêutico de indivíduos pós traumatismo cranioencefálico. No presente relato de caso o paciente foi submetido à avaliação eletrofisiológica e comportamental do processamento auditivo pré e pós treinamento auditivo acusticamente controlado (TAAC) e seis meses após a intervenção. O TAAC foi organizado em oito sessões, enfocando o treinamento das habilidades auditivas de ordenação temporal, fechamento auditivo e figura-fundo. Na avaliação pós TAAC foi observada melhora quanto aos processos gnósicos de codificação, organização e não verbal. Em relação à avaliação eletrofisiológica houve melhora na morfologia e na latência das ondas do potencial evocado auditivo de tronco encefálico e na amplitude do componente potencial evocado auditivo de longa latência (P300). Na reavaliação após 6 meses do TACC foi verificada estabilidade e melhora da avaliação comportamental e eletrofisiológica. O treinamento auditivo acusticamente controlado mostrou-se eficaz ao desenvolver e refinar diferentes habilidades auditivas como demonstrado na avaliação eletrofisiológica e comportamental do processamento auditivo e os benefícios mostraram-se estáveis no longo prazo.