Relationship between auditory perception skills and mismatch negativity recorded in free field in cochlear-implant users

Predicting speech intelligibility from a selective attention decoding paradigm in cochlear implant users

OBJECTIVES

Electroencephalography (EEG) can be used to decode selective attention in cochlear implant (CI) users. This work investigates if selective attention to an attended speech source in the presence of a concurrent speech source can predict speech understanding in CI users.

APPROACH

CI users were instructed to attend to one out of two speech streams while EEG was recorded. Both speech streams were presented to the same ear and at different signal to interference ratios (SIRs). Speech envelope reconstruction of the to-be-attended speech from EEG was obtained by training decoders using regularized least squares. The correlation coefficient between the reconstructed and the attended (ρ_(A_SIR )) or the unattended (ρ_(U_SIR )) speech stream at each SIR was computed. Additionally, we computed the difference correlation coefficient at the same 〖(ρ〗_Diff= ρ_(A_SIR )-ρ_(U_SIR )) and opposite SIR (ρ_DiffOpp= ρ_(A_SIR )-ρ_(U_(-SIR) )). ρ_Diff compares the attended and unattended correlation coefficient to speech sources presented at different presentation levels depending on SIR. In contrast, ρ_DiffOpp compares the attended and unattended correlation coefficients to speech sources presented at the same presentation level irrespective of SIR.

MAIN RESULTS

Selective attention decoding in CI users is possible even if both speech streams are presented monaurally. A significant effect of SIR on ρ_(A_SIR ), ρ_Diff and ρ_DiffOpp, but not on ρ_(U_SIR ), was observed. Finally, the results show a significant correlation between speech understanding performance and ρ_(A_SIR ) as well as with ρ_(U_SIR ) across subjects. Moreover, ρ_DiffOpp which is less affected by the CI artifact, also demonstrated a significant correlation with speech understanding.

SIGNIFICANCE

Selective attention decoding in CI users is possible, however care needs to be taken with the CI artifact and the speech material used to train the decoders. These results are important for future development of objective speech understanding measures for CI users.

Neural Mechanisms of Hearing Recovery for Cochlear-Implanted Patients: An Electroencephalogram Follow-Up Study

Background

Patients with severe profound hearing loss could benefit from cochlear implantation (CI). However, the neural mechanism of such benefit is still unclear. Therefore, we analyzed the electroencephalogram (EEG) and behavioral indicators of auditory function remodeling in patients with CI. Both indicators were sampled at multiple time points after implantation (1, 90, and 180 days).

Methods

First, the speech perception ability was evaluated with the recording of a list of Chinese words and sentences in 15 healthy controls (HC group) and 10 patients with CI (CI group). EEG data were collected using an oddball paradigm. Then, the characteristics of event-related potentials (ERPs) and mismatch negative (MMN) were compared between the CI group and the HC group. In addition, we analyzed the phase lag indices (PLI) in the CI group and the HC group and calculated the difference in functional connectivity between the two groups at different stages after implantation.

Results

The behavioral indicator, speech recognition ability, in CI patients improved as the implantation time increased. The MMN analysis showed that CI patients could recognize the difference between standard and deviation stimuli just like the HCs 90 days after cochlear implantation. Comparing the latencies of N1/P2/MMN between the CI group and the HC group, we found that the latency of N1/P2 in CI patients was longer, while the latency of MMN in CI users was shorter. In addition, PLI-based whole-brain functional connectivity (PLI-FC) showed that the difference between the CI group and the HC group mainly exists in electrode pairs between the bilateral auditory area and the frontal area. Furthermore, all those differences gradually decreased with the increase in implantation time.

Conclusion

The N1 amplitude, N1/P2/MMN latency, and PLI-FC in the alpha band may reflect the process of auditory function remodeling and could be an objective index for the assessment of speech perception ability and the effect of cochlear implantation.

A Preliminary Study of the Effects of Attentive Music Listening on Cochlear Implant Users' Speech Perception, Quality of Life, and Behavioral and Objective Measures of Frequency Change Detection

Introduction

Most cochlear implant (CI) users have difficulty in listening tasks that rely strongly on perception of frequency changes (e.g., speech perception in noise, musical melody perception, etc.). Some previous studies using behavioral or subjective assessments have shown that short-term music training can benefit CI users’ perception of music and speech. Electroencephalographic (EEG) recordings may reveal the neural basis for music training benefits in CI users.

Objective

To examine the effects of short-term music training on CI hearing outcomes using a comprehensive test battery of subjective evaluation, behavioral tests, and EEG measures.

Design

Twelve adult CI users were recruited for a home-based music training program that focused on attentive listening to music genres and materials that have an emphasis on melody. The participants used a music streaming program (i.e., Pandora) downloaded onto personal electronic devices for training. The participants attentively listened to music through a direct audio cable or through Bluetooth streaming. The training schedule was 40 min/session/day, 5 days/week, for either 4 or 8 weeks. The pre-training and post-training tests included: hearing thresholds, Speech, Spatial and Qualities of Hearing Scale (SSQ12) questionnaire, psychoacoustic tests of frequency change detection threshold (FCDT), speech recognition tests (CNC words, AzBio sentences, and QuickSIN), and EEG responses to tones that contained different magnitudes of frequency changes.

Results

All participants except one finished the 4- or 8-week training, resulting in a dropout rate of 8.33%. Eleven participants performed all tests except for two who did not participate in EEG tests. Results showed a significant improvement in the FCDTs as well as performance on CNC and QuickSIN after training (p < 0.05), but no significant improvement in SSQ scores (p > 0.05). Results of the EEG tests showed larger post-training cortical auditory evoked potentials (CAEPs) in seven of the nine participants, suggesting a better cortical processing of both stimulus onset and within-stimulus frequency changes.

Conclusion

These preliminary data suggest that extensive, focused music listening can improve frequency perception and speech perception in CI users. Further studies that include a larger sample size and control groups are warranted to determine the efficacy of short-term music training in CI users.

Behavioral and electrophysiological investigation of hearing and speech outcomes in pre-linguistic deaf children with white matter changes after cochlear implantation

Background: There are some debates regarding the benefit from cochlear implantation (CI) for prelingually deaf children with white matter changes.Objective: To assess the hearing and speech outcomes of prelingually deaf children with white matter changes (group A), and those with complete deafness (group B), at 2 years after CI.Material and Methods: Study 1 included 32 and 34 children in group A and B, respectively. The Categories of Auditory Performance (CAP) and Speech Intelligibility Rate (SIR) were used to assess the performance on hearing and speech. Study 2 included eight children with white matter changes and eight with complete deafness at 2 years post-CI, and nine normal-hearing peers. The mismatch response (MMR) to the stimulus pair 'ba'/'pa' was investigated.Results: There was no significant difference on CAP or SIR scores between the children in group A and B. All children with white matter changes showed MMRs to Mandarin consonants at 2 years post-CI. And there was no significant difference on the incidence, the latency or amplitude of MMR among three groups.Conclusions and significance: Most prelingually deaf children with white matter changes got good outcomes from CI. CI is not a contraindication for most individuals with white matter changes.

Mismatch Negativity in Children with Cochlear Implant

Introduction  The mismatch negativity (MMN) is a negative long-latency auditory potential elicited by any discriminable change in a repetitive aspect of auditory stimulation. This evoked potential can provide cortical information about the sound processing, including in children who use cochlear implants. Objective  To identify MMN characteristics regarding latency, amplitude, and wave area in cochlear implanted children and to identify associations among language development, speech perception and family involvement. Methods  This is a descriptive, observational, cross-sectional study, which compared two groups: study group-children with cochlear implant, and control group-hearing children. The children were submitted to MMN evaluation with non-verbal tone burst stimulus, differing in frequency in sound field at 70 dBHL, with SmartEP equipment (Intelligent Hearing Systems, Miami, FL, USA). Speech perception and language development questionnaires were also applied, and the family participation in the rehabilitation process was classified. Results  The occurrence of MMN was 73.3% for the control group and 53.3% for the study group. Values of latency, amplitude and area of MMN of children using cochlear implants were similar to those of hearing children, and did not differ between groups. The occurrence of MMN was not correlated to the variables of hearing, language and family categories. Conclusion  Children with cochlear implants showed similar MMN responses to those of the children in the control group, with mean latency, amplitude and area of 208.9 ms (±12.8), -2.37 μV (±0.38) and 86.5 μVms (±23.4), respectively. There was no correlation between the presence of MMN and children's performance in the auditory and language development tests or family involvement during rehabilitation.

A preliminary study of auditory mismatch response on the day of cochlear implant activation in children with hearing aids prior implantation

Objective

The study aimed to explore the characteristics of auditory mismatch response (MMR) in hearing-impaired children on the day when the cochlear implant (CI) was started (power-up) and the speech processor was programmed, and to investigate the effects of wearing hearing aids (HAs) before cochlear implantation on the early stage of postoperative auditory cortex plasticity, providing some demonstrative data for the objective evaluation of postoperative early auditory ability in children who underwent cochlear implantation.

Methods

The participants were 34 children with profound sensorineural hearing loss, who underwent cochlear implantation. The classical passive Oddball paradigm was adopted, using a pair of vowels which only have different lexical tones. The standard stimulus was /a2/ and the devious stimulus was /a4/.

Results

1) On the day of CI activation, the auditory MMR has been elicited in 30 children; the MMR incidence was 88%. 2) We observed both positive and negative auditory MMR waveforms. And logistic regression analysis showed that it was influenced by the age at cochlear implantation. 3) The duration with HA before surgery significantly influenced the MMR latency. The children with longer duration of HA use have much earlier latency of MMR. 4) There was a significant positive correlation between the age at HA use initiation and MMR amplitude. Earlier initial HA use was associated with smaller amplitude.

Conclusions

MMR in response to Mandarin lexical tone can be recorded in most pediatric patients who had experience with HA on the day of CI power up. MMR is closely associated with the age at cochlear implantation, duration of HA use, and the age at HA use initiation. Hearing-impaired children should wear HA as early as possible and ensure consistent usage.

Cortical reorganization after cochlear implantation for adults with single-sided deafness

BACKGROUND

Adults with single sided deafness (SSD) have lost binaural function, which limits sound source localization, speech understanding in noise, and quality of life. For SSD patients, restoration of bilateral auditory input is possible only with a cochlear implant (CI). In this study, cortical auditory evoked potentials (CAEPs) and behavioral performance were measured in left-implanted (SSD-CI-L) and right-implanted (SSD-CI-R) patients before and after cochlear implantation. We hypothesized that improvements in behavioral performance would be accompanied by changes in CAEPs after cochlear implantation.

DESIGN

Prospective longitudinal study.

SETTING

Tertiary referral center.

METHOD

Nine right-handed adult SSD CI patients participated in the study. CAEPs were recorded before cochlear implantation and at 6 and 12 months post-implantation. CAEPs were elicited using speech stimuli (/ba/) delivered in sound field at 70 dBA. Global field power (GFP) latency and amplitude were calculated for P1, N1 and P2 peaks at each test session. CAEP were analyzed at frontocentral (Cz) and temporal (P7, P8, T7 and T8) and mastoid electrodes (M1 and M2) contralateral to the CI ear. Behavioral measures (sentence recognition in noise, with and without spatial cues) were collected at the same test sessions as for CAEPs. Speech performance and CAEPs were also measured in a control group of normal-hearing (NH) subjects.

RESULTS

While increased N1 amplitude was observed in the scalp potential maps for GFP and Cz for SSD-CI-L patients after implantation, the changes were not statistically significant. Peak CAEP amplitude at electrodes to contralateral to the CI ear increased after cochlear implantation for all SSD-CI patients, but significant increases were observed only for mastoid sites. Peak latencies for some components at temporal and mastoid sites remained significantly longer than for the NH control group, even after cochlear implantation. For SSD-CI-R patients, P2 peak amplitude for baseline GFP and Cz was significantly lower than for the NH control group. A significant improvement for speech understanding in noise was observed at 12 months post-implantation when speech was presented to the CI ear and noise to the non-implanted ear.

CONCLUSION

After cochlear implantation, speech understanding significantly improved when speech and noise were spatially separated. The increased N1 amplitude for SSD-CI-L patients and the increased bilateral activation for all SSD-CI patients may reflect cortical reorganization and restoration of binaural function after one year of experience with the CI. However, because of the limited number of SSD patients, significant changes in cortical activity after cochlear implantation were often difficult to observe.

Toward Automated Cochlear Implant Fitting Procedures Based on Event-Related Potentials

OBJECTIVES

Cochlear implants (CIs) restore hearing to the profoundly deaf by direct electrical stimulation of the auditory nerve. To provide an optimal electrical stimulation pattern the CI must be individually fitted to each CI user. To date, CI fitting is primarily based on subjective feedback from the user. However, not all CI users are able to provide such feedback, for example, small children. This study explores the possibility of using the electroencephalogram (EEG) to objectively determine if CI users are able to hear differences in tones presented to them, which has potential applications in CI fitting or closed loop systems.

DESIGN

Deviant and standard stimuli were presented to 12 CI users in an active auditory oddball paradigm. The EEG was recorded in two sessions and classification of the EEG data was performed with shrinkage linear discriminant analysis. Also, the impact of CI artifact removal on classification performance and the possibility to reuse a trained classifier in future sessions were evaluated.

RESULTS

Overall, classification performance was above chance level for all participants although performance varied considerably between participants. Also, artifacts were successfully removed from the EEG without impairing classification performance. Finally, reuse of the classifier causes only a small loss in classification performance.

CONCLUSIONS

Our data provide first evidence that EEG can be automatically classified on single-trial basis in CI users. Despite the slightly poorer classification performance over sessions, classifier and CI artifact correction appear stable over successive sessions. Thus, classifier and artifact correction weights can be reused without repeating the set-up procedure in every session, which makes the technique easier applicable. With our present data, we can show successful classification of event-related cortical potential patterns in CI users. In the future, this has the potential to objectify and automate parts of CI fitting procedures.

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.

When Hearing Is Tricky: Speech Processing Strategies in Prelingually Deafened Children and Adolescents with Cochlear Implants Having Good and Poor Speech Performance

Cochlear implants provide individuals who are deaf with access to speech. Although substantial advancements have been made by novel technologies, there still is high variability in language development during childhood, depending on adaptation and neural plasticity. These factors have often been investigated in the auditory domain, with the mismatch negativity as an index for sensory and phonological processing. Several studies have demonstrated that the MMN is an electrophysiological correlate for hearing improvement with cochlear implants. In this study, two groups of cochlear implant users, both with very good basic hearing abilities but with non-overlapping speech performance (very good or very poor speech performance), were matched according to device experience and age at implantation. We tested the perception of phonemes in the context of specific other phonemes from which they were very hard to discriminate (e.g., the vowels in /bu/ vs. /bo/). The most difficult pair was individually determined for each participant. Using behavioral measures, both cochlear implants groups performed worse than matched controls, and the good performers performed better than the poor performers. Cochlear implant groups and controls did not differ during time intervals typically used for the mismatch negativity, but earlier: source analyses revealed increased activity in the region of the right supramarginal gyrus (220-260 ms) in good performers. Poor performers showed increased activity in the left occipital cortex (220-290 ms), which may be an index for cross-modal perception. The time course and the neural generators differ from data from our earlier studies, in which the same phonemes were assessed in an easy-to-discriminate context. The results demonstrate that the groups used different language processing strategies, depending on the success of language development and the particular language context. Overall, our data emphasize the role of neural plasticity and use of adaptive strategies for successful language development with cochlear implants.

Change in Speech Perception and Auditory Evoked Potentials over Time after Unilateral Cochlear Implantation in Postlingually Deaf Adults

Speech perception varies widely across cochlear implant (CI) users and typically improves over time after implantation. There is also some evidence for improved auditory evoked potentials (shorter latencies, larger amplitudes) after implantation but few longitudinal studies have examined the relationship between behavioral and evoked potential measures after implantation in postlingually deaf adults. The relationship between speech perception and auditory evoked potentials was investigated in newly implanted cochlear implant users from the day of implant activation to 9 months postimplantation, on five occasions, in 10 adults age 27 to 57 years who had been bilaterally profoundly deaf for 1 to 30 years prior to receiving a unilateral CI24 cochlear implant. Changes over time in middle latency response (MLR), mismatch negativity, and obligatory cortical auditory evoked potentials and word and sentence speech perception scores were examined. Speech perception improved significantly over the 9-month period. MLRs varied and showed no consistent change over time. Three participants aged in their 50s had absent MLRs. The pattern of change in N1 amplitudes over the five visits varied across participants. P2 area increased significantly for 1,000- and 4,000-Hz tones but not for 250 Hz. The greatest change in P2 area occurred after 6 months of implant experience. Although there was a trend for mismatch negativity peak latency to reduce and width to increase after 3 months of implant experience, there was considerable variability and these changes were not significant. Only 60% of participants had a detectable mismatch initially; this increased to 100% at 9 months. The continued change in P2 area over the period evaluated, with a trend for greater change for right hemisphere recordings, is consistent with the pattern of incremental change in speech perception scores over time. MLR, N1, and mismatch negativity changes were inconsistent and hence P2 may be a more robust measure of auditory plasticity in adult implant recipients. P2 was still improving at 9 months postimplantation. Future studies should explore longitudinal changes over a longer period.

An objective auditory measure to assess speech recognition in adult cochlear implant users

OBJECTIVE

To verify if a mismatch negativity (MMN) paradigm based on speech syllables can differentiate between good and poorer cochlear implant (CI) users on a speech recognition task.

METHODS

Twenty adults with a CI and 11 normal hearing adults participated in the study. Based on a speech recognition test, ten CI users were classified as good performers and ten as poor performers. We measured the MMN with /da/ as the standard stimulus and /ba/ and /ga/ as the deviants. Separate analyses were conducted on the amplitude and latency of the MMN.

RESULTS

A MMN was evoked by both deviant stimuli in all normal hearing participants and in well performing CI users, with similar amplitudes for both groups. However, the amplitude of the MMN was significantly reduced for the poorer CI users compared to the normal hearing group and the good CI users. The latency was longer for both groups of cochlear implant users. A bivariate correlation showed a significant positive correlation between the speech recognition score and the amplitude of the MMN.

CONCLUSIONS

The MMN can distinguish between CI users who have good versus poor speech recognition as assessed with conventional tasks.

SIGNIFICANCE

Our findings suggest that the MMN can be use to assess speech recognition proficiency in CI users who cannot be tested with regular speech recognition tasks, like infants and other non-verbal populations.

Cortical encoding of pitch contour changes in cochlear implant users: a mismatch negativity study

A better understanding of melodic pitch perception in cochlear implants (CIs) may guide signal processing and/or rehabilitation techniques to improve music perception and appreciation in CI patients. In this study, the mismatch negativity (MMN) in response to infrequent changes in 5-tone pitch contours was obtained in CI users and normal-hearing (NH) listeners. Melodic contour identification (MCI) was also measured. Results showed that MCI performance was poorer in CI than in NH subjects; the MMNs were missing in all CI subjects for the 1-semitone contours. The MMNs with the 5-semitone contours were observed in a smaller proportion of CI than NH subjects. Results suggest that encoding of pitch contour changes in CI users appears to be degraded, most likely due to the limited pitch cues provided by the CI and deafness-related compromise of brain substrates.

The mismatch negativity (MMN) brain response to sound frequency changes in adult cochlear implant recipients: a follow-up study

CONCLUSION

Plasticity of auditory pitch discrimination driven by cochlear implant (CI) use uring a 2.5-year follow-up was indicated by an enhancement of the amplitude of mismatch negativity (MMN) event-related brain potential (ERP) to pure tone frequency changes.

OBJECTIVES

To follow up changes in MMN elicited to frequency and duration changes in tones during 2.5 years of CI use and to compare MMN results with audiometric speech recognition scores (SRSs).

METHODS

Postlingually deafened adults with Cochlear Nucleus CI-22 and spectra processor with SPEAK strategy were recruited. MMN was measured at 1 and 2.5 years after CI activation. Repetitive 100 ms standard tones with a frequency of 500, 1000, 2000 or 4000 Hz in separate sequences were delivered to participants concentrating on a silent movie. Deviant tones occurring infrequently among standard tones were 20% lower in frequency or 50% shorter in duration than the standards. Speech recognition ability was followed with SRSs.

RESULTS

Both time from CI activation and the frequency range of tones had significant effects on the MMN amplitude. A significant enhancement was observed for the MMN elicited by 3200 Hz deviant tones among 4000 Hz standards. Also SRSs significantly increased with time and correlated with MMN amplitudes to the 3200 Hz deviants in both measurements.

Neural correlates of speech processing in prelingually deafened children and adolescents with cochlear implants

Prelingually deafened children with cochlear implants stand a good chance of developing satisfactory speech performance. Nevertheless, their eventual language performance is highly variable and not fully explainable by the duration of deafness and hearing experience. In this study, two groups of cochlear implant users (CI groups) with very good basic hearing abilities but non-overlapping speech performance (very good or very bad speech performance) were matched according to hearing age and age at implantation. We assessed whether these CI groups differed with regard to their phoneme discrimination ability and auditory sensory memory capacity, as suggested by earlier studies. These functions were measured behaviorally and with the Mismatch Negativity (MMN). Phoneme discrimination ability was comparable in the CI group of good performers and matched healthy controls, which were both better than the bad performers. Source analyses revealed larger MMN activity (155-225 ms) in good than in bad performers, which was generated in the frontal cortex and positively correlated with measures of working memory. For the bad performers, this was followed by an increased activation of left temporal regions from 225 to 250 ms with a focus on the auditory cortex. These results indicate that the two CI groups developed different auditory speech processing strategies and stress the role of phonological functions of auditory sensory memory and the prefrontal cortex in positively developing speech perception and production.

Speech perception and cortical auditory evoked potentials in cochlear implant users with auditory neuropathy spectrum disorders

OBJECTIVE

To characterize the P(1) component of long latency auditory evoked potentials (LLAEPs) in cochlear implant users with auditory neuropathy spectrum disorder (ANSD) and determine firstly whether they correlate with speech perception performance and secondly whether they correlate with other variables related to cochlear implant use.

METHODS

This study was conducted at the Center for Audiological Research at the University of São Paulo. The sample included 14 pediatric (4-11 years of age) cochlear implant users with ANSD, of both sexes, with profound prelingual hearing loss. Patients with hypoplasia or agenesis of the auditory nerve were excluded from the study. LLAEPs produced in response to speech stimuli were recorded using a Smart EP USB Jr. system. The subjects' speech perception was evaluated using tests 5 and 6 of the Glendonald Auditory Screening Procedure (GASP).

RESULTS

The P(1) component was detected in 12/14 (85.7%) children with ANSD. Latency of the P(1) component correlated with duration of sensorial hearing deprivation (*p=0.007, r=0.7278), but not with duration of cochlear implant use. An analysis of groups assigned according to GASP performance (k-means clustering) revealed that aspects of prior central auditory system development reflected in the P(1) component are related to behavioral auditory skills.

CONCLUSIONS

In children with ANSD using cochlear implants, the P(1) component can serve as a marker of central auditory cortical development and a predictor of the implanted child's speech perception performance.

The mismatch negativity (MMN)--a unique window to disturbed central auditory processing in ageing and different clinical conditions

In this article, we review clinical research using the mismatch negativity (MMN), a change-detection response of the brain elicited even in the absence of attention or behavioural task. In these studies, the MMN was usually elicited by employing occasional frequency, duration or speech-sound changes in repetitive background stimulation while the patient was reading or watching videos. It was found that in a large number of different neuropsychiatric, neurological and neurodevelopmental disorders, as well as in normal ageing, the MMN amplitude was attenuated and peak latency prolonged. Besides indexing decreased discrimination accuracy, these effects may also reflect, depending on the specific stimulus paradigm used, decreased sensory-memory duration, abnormal perception or attention control or, most importantly, cognitive decline. In fact, MMN deficiency appears to index cognitive decline irrespective of the specific symptomatologies and aetiologies of the different disorders involved.

Effects of mental workload on long-latency auditory-evoked-potential, salivary cortisol, and immunoglobulin A

This paper researches on the effects of mental workload on long-latency auditory-evoked-potential (AEP), salivary cortisol, and immunoglobulin A (IgA). 20 Healthy subjects (11 males and 9 females) participated in the experiment voluntarily. The mental task consisted of two parts: arithmetic task and reading comprehension task. The Latencies of N1, P2, N2, P3, and mismatch negativity (MMN) all increased significantly after the mental tasks were adopted at all of the three recording sites: Cz, Fz, and Pz (p<0.05). In this experiment, changes of salivary cortisol and s-IgA levels due to mental tasks were not significant. With the introduction of mental tasks, more processing resources are allocated to the primary task (mental task), and decreased processing resources available for the secondary task (auditory task), which is reflected on the increases in the latencies of probe-evoked AEP components.

Mismatch negativity and adaptation measures of the late auditory evoked potential in cochlear implant users

A better understanding of the neural correlates of large variability in cochlear implant (CI) patients' speech performance may allow us to find solutions to further improve CI benefits. The present study examined the mismatch negativity (MMN) and the adaptation of the late auditory evoked potential (LAEP) in 10 CI users. The speech syllable /da/ and 1-kHz tone burst were used to examine the LAEP adaptation. The amount of LAEP adaptation was calculated according to the averaged N1-P2 amplitude for the LAEPs evoked by the last 3 stimuli and the amplitude evoked by the first stimulus. For the MMN recordings, the standard stimulus (1-kHz tone) and the deviant stimulus (2-kHz tone) were presented in an oddball condition. Additionally, the deviants alone were presented in a control condition. The MMN was derived by subtracting the response to the deviants in the control condition from the oddball condition. Results showed that good CI performers displayed a more prominent LAEP adaptation than moderate-to-poor performers. Speech performance was significantly correlated to the amount of LAEP adaptation for the 1-kHz tone bursts. Good performers displayed large MMNs and moderate-to-poor performers had small or absent MMNs. The abnormal electrophysiological findings in moderate-to-poor performers suggest that long-term deafness may cause damage not only at the auditory cortical level, but also at the cognitive level.

Ear selection and pediatric cochlear implants: a preliminary examination of speech production outcomes

OBJECTIVE

The goal of the current study was to examine whether ear selection (left versus right) for cochlear implantation results in significant differences in speech production outcomes.

METHODS

Ten children with right-ear implants were compared to five children with left-ear implants on intelligibility of speech produced in single words, sentences, and conversation as well as on accuracy of speech sounds produced during administration of a single word articulation test and in conversational speech.

RESULTS

The children with right-ear implants performed significantly better than those with left-ear implants but only on the single word tasks. No significant differences were observed at the sentence or conversational speech levels.

CONCLUSION

Findings are discussed relative to the possibility that the obtained ear of implantation differences (if real) may disappear over time. Such a conclusion is quite tentative however given the small sample size in the current study. Such a limitation may also explain why no differences were obtained for the connected speech measures. Further study of ear selection outcomes is clearly indicated.

The mismatch negativity (MMN) in basic research of central auditory processing: a review

In the present article, the basic research using the mismatch negativity (MMN) and analogous results obtained by using the magnetoencephalography (MEG) and other brain-imaging technologies is reviewed. This response is elicited by any discriminable change in auditory stimulation but recent studies extended the notion of the MMN even to higher-order cognitive processes such as those involving grammar and semantic meaning. Moreover, MMN data also show the presence of automatic intelligent processes such as stimulus anticipation at the level of auditory cortex. In addition, the MMN enables one to establish the brain processes underlying the initiation of attention switch to, conscious perception of, sound change in an unattended stimulus stream.