Cortical Auditory Evoked Potentials Research Articles

Effects of Signal Type and Noise Background on Auditory Evoked Potential N1, P2, and P3 Measurements in Blast-Exposed Veterans.

Veterans who have been exposed to high-intensity blast waves frequently report persistent auditory difficulties such as problems with speech-in-noise (SIN) understanding, even when hearing sensitivity remains normal. However, these subjective reports have proven challenging to corroborate objectively. Here, we sought to determine whether use of complex stimuli and challenging signal contrasts in auditory evoked potential (AEP) paradigms rather than traditional use of simple stimuli and easy signal contrasts improved the ability of these measures to (1) distinguish between blast-exposed Veterans with auditory complaints and neurologically normal control participants, and (2) predict behavioral measures of SIN perception. A total of 33 adults (aged 19-56 years) took part in this study, including 17 Veterans exposed to high-intensity blast waves within the past 10 years and 16 neurologically normal control participants matched for age and hearing status with the Veteran participants. All participants completed the following test measures: (1) a questionnaire probing perceived hearing abilities; (2) behavioral measures of SIN understanding including the BKB-SIN, the AzBio presented in 0 and +5 dB signal to noise ratios (SNRs), and a word-level consonant-vowel-consonant test presented at +5 dB SNR; and (3) electrophysiological tasks involving oddball paradigms in response to simple tones (500 Hz standard, 1000 Hz deviant) and complex speech syllables (/ba/ standard, /da/ deviant) presented in quiet and in four-talker speech babble at a SNR of +5 dB. Blast-exposed Veterans reported significantly greater auditory difficulties compared to control participants. Behavioral performance on tests of SIN perception was generally, but not significantly, poorer among the groups. Latencies of P3 responses to tone signals were significantly longer among blast-exposed participants compared to control participants regardless of background condition, though responses to speech signals were similar across groups. For cortical AEPs, no significant interactions were found between group membership and either stimulus type or background. P3 amplitudes measured in response to signals in background babble accounted for 30.9% of the variance in subjective auditory reports. Behavioral SIN performance was best predicted by a combination of N1 and P2 responses to signals in quiet which accounted for 69.6% and 57.4% of the variance on the AzBio at 0 dB SNR and the BKB-SIN, respectively. Although blast-exposed participants reported far more auditory difficulties compared to controls, use of complex stimuli and challenging signal contrasts in cortical and cognitive AEP measures failed to reveal larger group differences than responses to simple stimuli and easy signal contrasts. Despite this, only P3 responses to signals presented in background babble were predictive of subjective auditory complaints. In contrast, cortical N1 and P2 responses were predictive of behavioral SIN performance but not subjective auditory complaints, and use of challenging background babble generally did not improve performance predictions. These results suggest that challenging stimulus protocols are more likely to tap into perceived auditory deficits, but may not be beneficial for predicting performance on clinical measures of SIN understanding. Finally, these results should be interpreted with caution since blast-exposed participants did not perform significantly poorer on tests of SIN perception.

Auditory Gating in Hearing Loss

Sensory gating is a measure used to evaluate inhibitory deficits underlying neurological disorders. However, the effects of hearing loss (HL), thought to decrease inhibition, remain unknown on gating function. The goal of this study was to investigate gating performance in HL. This was a prospective, cross-sectional study with independent group comparison and correlational design. Eleven adults (mean age/standard deviation = 47.546 ± 7.967 years) with normal hearing (NH) and 11 adults (mean age/standard deviation = 56.273 ± 13.871 years) with mild-moderate high-frequency HL. Cortical auditory evoked potentials (CAEPs) were recorded in response to tonal pairs via high-density electroencephalography. The CAEP response to the second tone in the pair (S2) was compared with the response to the first tone in the pair (S1) within groups. Amplitude gating indices were compared between groups and correlated with auditory behavioral measures. Current density reconstructions were performed to estimate cortical gating generators. Amplitude gating indices were decreased and correlated with elevated auditory thresholds. Gating generators in temporal, frontal, and prefrontal regions were localized in the NH group, while HL gating was localized in mainly temporal and parietal areas. Reduced inhibition may be associated with compensatory cortical gating networks in HL and should be considered when utilizing gating in clinical populations.

Auditory Neuropathy Spectrum Disorders: From Diagnosis to Treatment: Literature Review and Case Reports.

Auditory neuropathy spectrum disorder (ANSD) refers to a range of hearing impairments characterized by deteriorated speech perception, despite relatively preserved pure-tone detection thresholds. Affected individuals usually present with abnormal auditory brainstem responses (ABRs), but normal otoacoustic emissions (OAEs). These electrophysiological characteristics have led to the hypothesis that ANSD may be caused by various dysfunctions at the cochlear inner hair cell (IHC) and spiral ganglion neuron (SGN) levels, while the activity of outer hair cells (OHCs) is preserved, resulting in discrepancies between pure-tone and speech comprehension thresholds. The exact prevalence of ANSD remains unknown; clinical findings show a large variability among subjects with hearing impairment ranging from mild to profound hearing loss. A wide range of prenatal and postnatal etiologies have been proposed. The study of genetics and of the implicated sites of lesion correlated with clinical findings have also led to a better understanding of the molecular mechanisms underlying the various forms of ANSD, and may guide clinicians in better screening, assessment and treatment of ANSD patients. Besides OAEs and ABRs, audiological assessment includes stapedial reflex measurements, supraliminal psychoacoustic tests, electrocochleography (ECochG), auditory steady-state responses (ASSRs) and cortical auditory evoked potentials (CAEPs). Hearing aids are indicated in the treatment of ANSD with mild to moderate hearing loss, whereas cochlear implantation is the first choice of treatment in case of profound hearing loss, especially in case of IHC presynaptic disorders, or in case of poor auditory outcomes with conventional hearing aids.

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.

IntroductionMost 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.ObjectiveTo 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.DesignTwelve 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.ResultsAll 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.ConclusionThese 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.

Event related potentials in cases of amblyaudia

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Amblyaudia is a weakness in the listener’s binaural processing of auditory information. Subjects with amblyaudia also demonstrate binaural integration deficits and may display similar patterns in their evoked responses in terms of latency and amplitude of these responses. The purpose of this study was to identify the presence of amblyaudia in a population of young children subjects and to measure mismatch negativity (MMN), P300 and cortical auditory evoked potentials (CAEPs) for those individuals.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; Subjects included in this study were divided into 2 groups control group that consisted of 20 normal hearing subjects with normal developmental milestones and normal speech development. The study group (GII) consisted of 50 subjects with central auditory processing disorders (CAPDs) diagnosed by central auditory screening tests. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; With using dichotic tests including dichotic digits test (DDT) and competing sentence test (CST), we could classify these cases into normal, dichotic dysaudia, amblyaudia, and amblyaudia plus with percentages (40%, 14%, 38%, 8% respectively). Using event related potentials, we found that P300 and MMN are more specific in detecting neurocognitive dysfunction related to allocation of attentional resources and immediate memory in these cases.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; The presence of amblyaudia in cases of central auditory processing disorders (CAPDs) and event related potentials is an objective tool for diagnosis, prognosis and follow up after rehabilitation.&lt;/p&gt;

Noise-Induced Change of Cortical Temporal Processing in Cochlear Implant Users.

Objectives.Cochlear implant (CI) users typically report impaired ability to understand speech in noise. Speech understanding in CI users decreases with noise due to reduced temporal processing ability, and speech perceptual errors involve stop consonants distinguished by voice onset time (VOT). The current study examined the effects of noise on various speech perception tests while at the same time used cortical auditory evoked potentials (CAEPs) to quantify the change of neural processing of speech sounds caused by noise. We hypothesized that the noise effects on VOT processing can be reflected in N1/P2 measures, the neural changes relate to behavioral speech perception performances.Methods.Ten adult CI users and 15 normal-hearing (NH) people participated in this study. CAEPs were recorded from 64 scalp electrodes in both quiet and noise (signal-to-noise ratio +5 dB) and in passive and active (requiring consonant discrimination) listening. Speech stimulus was synthesized consonant-vowels with VOTs of 0 and 50 ms. N1-P2 amplitudes and latencies were analyzed as a function of listening condition. For the active condition, the P3b also was analyzed. Behavioral measures included a variety of speech perception tasks.Results.For good performing CI users, performance in most speech test was lower in the presence of noise masking. N1 and P2 latencies became prolonged with noise masking. The P3b amplitudes were smaller in CI groups compared to NH. The degree of P2 latency change (0 vs. 50 ms VOT) was correlated with consonant perception in noise.Conclusion.The effects of noise masking on temporal processing can be reflected in cortical responses in CI users. N1/P2 latencies were more sensitive to noise masking than amplitude measures. Additionally, P2 responses appear to have a better relationship to speech perception in CI users compared to N1.

Effects of Age and Type of Stimulus on the Cortical Auditory Evoked Potential in Healthy Malaysian Children.

Background and ObjectivesThe cortical auditory evoked potential (CAEP) is a useful objective test for diagnosing hearing loss and auditory disorders. Prior to its clinical applications in the pediatric population, the possible influences of fundamental variables on the CAEP should be studied. The aim of the present study was to determine the effects of age and type of stimulus on the CAEP waveforms.Subjects and MethodsThirty-five healthy Malaysian children aged 4 to 12 years participated in this repeated-measures study. The CAEP waveforms were recorded from each child using a 1 kHz tone burst and the speech syllable /ba/. Latencies and amplitudes of P1, N1, and P2 peaks were analyzed accordingly. ResultsSignificant negative correlations were found between age and speech-evoked CAEP latency for each peak (p< 0.05). However, no significant correlations were found between age and tone-evoked CAEP amplitudes and latencies (p>0.05). The speech syllable /ba/ produced a higher mean P1 amplitude than the 1 kHz tone burst (p=0.001).ConclusionsThe CAEP latencies recorded with the speech syllable became shorter with age. While both tone-burst and speech stimuli were appropriate for recording the CAEP, significantly bigger amplitudes were found in speech-evoked CAEP. The preliminary normative CAEP data provided in the present study may be beneficial for clinical and research applications in Malaysian children.

Recording Obligatory Cortical Auditory Evoked Potentials in Infants: Quantitative Information on Feasibility and Parent Acceptability.

With the advent of newborn hearing screening and early intervention, there is a growing interest in using supra-threshold obligatory cortical auditory evoked potentials (CAEPs) to complement established pediatric clinical test procedures. The aim of this study was to assess the feasibility, and parent acceptability, of recording infant CAEPs. Typically developing infants (n = 104) who had passed newborn hearing screening and whose parents expressed no hearing concerns were recruited. Testing was not possible in 6 infants, leaving 98, age range 5 to 39 weeks (mean age = 21.9, SD = 9.4). Three short duration speech-like stimuli (/m/, /g/, /t/) were presented at 65 dB SPL via a loudspeaker at 0° azimuth. Three criteria were used to assess clinical feasibility: (i) median test duration <30 min, (ii) >90% completion rate in a single test session, and (iii) >90% response detection for each stimulus. We also recorded response amplitude, latency, and CAEP signal to noise ratio. Response amplitudes and residual noise levels were compared for Fpz (n = 56) and Cz (n = 42) noninverting electrode locations. Parental acceptability was based on an 8-item questionnaire (7-point scale, 1 being best). In addition, we explored the patient experience in semistructured telephone interviews with seven families. The median time taken to complete 2 runs for 3 stimuli, including preparation, was 27 min (range 17 to 59 min). Of the 104 infants, 98 (94%) were in an appropriate behavioral state for testing. A further 7 became restless during testing and their results were classified as "inconclusive." In the remaining 91 infants, CAEPs were detected in every case with normal bilateral tympanograms. Detection of CAEPs in response to /m/, /g/, and /t/ in these individuals was 86%, 100%, and 92%, respectively. Residual noise levels and CAEP amplitudes were higher for Cz electrode recordings. Mean scores on the acceptability questionnaire ranged from 1.1 to 2.6. Analysis of interviews indicated that parents found CAEP testing to be a positive experience and recognized the benefit of having an assessment procedure that uses conversational level speech stimuli. Test duration, completion rates, and response detection rates met (or were close to) our feasibility targets, and parent acceptability was high. CAEPs have the potential to supplement existing practice in 3- to 9-month olds.

Comparison of Cortical Auditory Evoked Potential Findings in Presbycusis with Low and High Word Recognition Score.

Deteriorated speech understanding is a common complaint in elderly people, and behavioral tests are used for routine clinical assessment of this problem. Cortical auditory evoked potentials (CAEPs) are frequently used for assessing speech detection and discrimination abilities of the elderly, and give promise for differential diagnosis of speech understanding problems. The aim of the study was to compare the P1, N1, and P2 CAEP latencies and amplitudes in presbycusis with low and high word recognition score (WRS). A cross-sectional study design was used for the study. Two groups were formed from the patients with presbycusis based on their scores on the speech recognition test. Fifty-seven elderly volunteers participated in the study. The first group composed of 27 participants with high WRS, the other group composed of 30 participants with low WRS. The CAEP waves were recorded from these participants using speech signals. Latencies and amplitudes of P1-N1-P2 waves of the two groups were compared with the t-test statistic. There were significant prolongation of P1 and N1 latencies in presbycusis with low WRS when compared with presbycusis with a relatively high word score (p < 0.05). According to the result of the research, P1 and N1 latencies of presbycusis with low WRS were longer than the participants with high WRS. Factors affecting peripheral auditory system, such as stimulus sensation level, might be responsible for P1 and N1 latency prolongation of the low WRS group.

Cortical Auditory Evoked Potentials in 2-Year-Old Subjects.

Introduction Cortical auditory evoked potentials (CAEPs) can be used to evaluate both peripheral and cortical components of auditory function, and contribute to the assessment of functional sensitivity and auditory thresholds, especially in neonates and infants. Auditory evoked potentials reflect auditory maturity and precede the acquisition of more complex auditory and cognitive skills, and are therefore crucial for speech and language development. Objective The aim of the present study was to determine the presence, latency and amplitude of CAEP components in response to verbal stimuli in children aged 2 years old. Methods The sample consisted of 19 subjects, 10 of whom were male while 9 were female. All of the participants were 24 months old at the time of assessment. Results A total of 17 of the participants displayed all components of the CAEP. Additionally, no significant differences were observed between genders or ears in the present sample. The presence of all components of the CAEP in subjects aged 2 years old confirms the existence of a critical period for the maturation of auditory pathways in the first 2 years of life. Conclusion In the present study, in addition to the P1/N1 components, it was possible to observe the presence of the CAEP P2/N2 components in individuals aged 24 months, confirming the existence of a critical period for the maturation of the auditory pathways in the first 2 years of life.

The effect of early versus late lipid infusion in parenteral nutrition on the biochemical and cortical auditory evoked potential parameters in preterm neonates

BackgroundAs brain activity depends greatly on the functions provided by lipid membranes, dietary fat in early life can affect the developing nervous system. Despite the adoption of an early more aggressive parenteral nutrition approach with amino acid infusions still reluctance to the early use of intravenous lipids in neonates.AimTo compare the effect of delayed versus early introduction of intravenous lipid in preterm on the biochemical parameters and on brain development by the cortical auditory evoked potential (CAEP) latency and amplitude.MethodsThis is a comparative study included 49 neonates admitted at the ain shams university NICUs. Participants were divided into two groups: 26 in group of early lipid infusion and 23 in late lipid infusion, Demographic data, and biochemical parameters were documented during the 1st 2 weeks of life. The CAEP was performed at age of 6 months. The latency and amplitude of P1 were recorded and compared between both groups.ResultsIn the present work we found that group of early lipid infusion had reach their full oral intake earlier with shorter duration of parenteral nutrition and length of stay. They had better weight gain and significantly better glucose level control than group of late lipid infusion. There was no significant difference in the other chemical parameters between both groups expect for the higher incidence of cholestasis in the group of late lipid infusion. At 6 months of age, the group of early lipid infusion had significantly shorter latency and amplitude of P1 than the group of late lipid infusion.ConclusionEarly effective nutrition positively affect feeding tolerance and weight gain and maturation of higher brain centers brain.

Changes in Cortical Auditory Evoked Potentials by Ipsilateral, Contralateral and Binaural Speech Stimulation in Normal-Hearing Adults.

ObjectivesCortical auditory evoked potentials (CAEPs) have been used to examine auditory cortical development or changes in patients with hearing loss. However, there have been no studies analyzing CAEP responses to the different sound stimulation by different stimulation sides. We characterized changes in normal CAEP responses by stimulation sides in normal-hearing adults.MethodsCAEPs from the right auditory cortex were recorded in 16 adults following unilateral (ipsilateral and contralateral) and bilateral sound stimulation using three speech sounds (/m/, /g/, and /t/). Amplitudes and latencies of the CAEP peaks in three conditions were compared.ResultsContralateral stimulation elicited larger P2-N1 amplitudes (sum of P2 and N1 amplitudes) than ipsilateral stimulation regardless of the stimulation sounds, mostly due to the larger P2 amplitudes obtained, but elicited comparable P2-N1 amplitudes to bilateral stimulation. Although the P2-N1 amplitudes obtained with the three speech sounds were comparable following contralateral stimulation, the /m/ sound elicited the largest P2-N1 amplitude in ipsilateral stimulation condition due to the largest N1 amplitude obtained, whereas /t/ elicited larger a P2-N1 amplitude than /g/ in bilateral stimulation condition due to a larger P2 amplitude.ConclusionSpectrally different speech sounds and input sides are encoded differently at the cortical level in normal-hearing adults. Standardized speech stimuli, as well as specific input sides of speech, are needed to examine normal development or rehabilitation-related changes of the auditory cortex in the future.

Cortical auditory responses according to hearing rehabilitation in unilateral hearing loss

ObjectiveTo assess the impact of rehabilitation systems (CROS: Contralateral Routing of Signal; BAHA: Bone-Anchored Hearing Aid; CI: cochlear implant) on cortical auditory evoked potentials (CAEP) and auditory performance in unilateral hearing loss. Subjects and methodTwenty-one adults with unilateral hearing loss, using CROS (n=6), BAHA (n=6) or CI (n=9), were included. Seven normal-hearing subjects served as controls. CAEPs were recorded for a (/ba/) speech stimulus; for patients, tests were conducted with and without their auditory rehabilitation. Amplitude and latency of the various CAEP components of the global field power (GFP) were measured, and scalp potential fields were mapped. Behavioral assessment used sentence recognition in noise, with and without spatial cues. ResultsOnly CI induced N1 peak amplitude change (P<0.05). CI and CROS increased polarity inversion amplitude in the contralateral ear, and frontocentral negativity on the scalp potential map. CI improved understanding when speech was presented to the implanted ear and noise to the healthy ear, and vice-versa. ConclusionCochlear implantation had the greatest impact on CAEP morphology and auditory performance. A longitudinal study could analyze progression of cortical reorganization.

Threshold Estimation Using "Chained Stimuli" for Cortical Auditory Evoked Potentials in Individuals With Normal Hearing and Hearing Impairment.

Purpose We investigated the utility of chained stimuli for threshold estimation using cortical auditory evoked potentials (CAEPs) in individuals with normal hearing sensitivity and hearing loss. The effect of the order of frequency in chained stimuli on CAEPs was also studied. Method Seventeen individuals with normal hearing and 17 individuals with mild to severe sensorineural hearing loss participated in the study. In individuals with normal hearing, CAEPs were recorded at 80 dB nHL for 4 chained stimuli with different orders of frequencies within them (Chained Stimuli 1 [CS1]: 500, 1000, 2000, 4000 Hz; Chained Stimuli 2: 4000, 2000, 1000, 500 Hz; Chained Stimuli 3: 500, 2000, 1000, 4000 Hz; Chained Stimuli 4: 4000, 1000, 2000, 500 Hz). CAEP threshold estimation was carried out using CS1 in both groups and was compared with behavioral pure-tone thresholds. Results CS1 elicited the largest amplitude responses at low and mid frequencies, whereas all 4 stimuli elicited similar amplitude responses at high frequencies. CAEP thresholds were generally within 10-20 dB above the participants' behavioral threshold in both groups. The difference between CAEP threshold and behavioral threshold was less for individuals with hearing loss compared to individuals with normal hearing. There was a significant positive correlation between CAEP threshold and behavioral threshold at all the frequencies. Conclusions CS1 could be used to elicit CAEPs for threshold estimation in adult participants with normal hearing and hearing loss of varied degrees with theoretically reduced testing time. The actual time reduction using chained stimuli and the correction factor to be applied to estimate behavioral threshold can be studied in future investigations.

Clinicians’ views of using cortical auditory evoked potentials (CAEP) in the permanent childhood hearing impairment patient pathway

Objective: To obtain clinicians’ views on the use of cortical auditory evoked potentials (CAEP) in the clinical pathway.Design: A questionnaire aimed at clinicians who use the HEARLab system with the Aided Cortical Assessment (ACA) Module. Results compared for Australians (where HEARLab produced) to other countries.Sample: The questionnaire was completed by 49 clinicians; 33 from Australia and 13 clinicians outside of Australia and 3 clinicians, destination unknown.Results: The findings of this research demonstrated that clinicians using CAEPs found them valuable for clinical practice. CAEPs were used to verify or modify hearing aid fittings and were used for counselling parents to reinforce the need for hearing aids. With the use of speech token as the stimulus clinicians had more relevant information to increase confidence in decision-making on paediatric hearing management.Conclusions: The main benefit from the use of CAEPs (using speech token stimuli) was for infant hearing aid fitting programmes, to facilitate earlier decisions relating to hearing aid fitting, for fine-tuning the aids and as an additional measure for cochlear implant referrals.

Early general development and central auditory system maturation in children with cochlear implants – A case series

ObjectivesA cochlear implant (CI) has the potential to improve the functioning of a deaf child in many aspects. Nevertheless, the dynamics of the general development, beyond the typically measured language abilities, directly after CI, is still unknown, especially if a child is implanted early. In this study we present a methodological framework for assessment of different domains of development, as well as the central auditory nervous system (CANS) maturation in infants and toddlers with a CI. MethodsThree children with bilateral congenital hearing loss and a unilateral CI, aged below 2.5 years, participated in a longitudinal study. Children were tested at three time points after cochlear implantation using the Polish Children Development Scale (CDS) consisting of a comprehensive battery of tests, as well as recordings of Cortical Auditory Evoked Potentials (CAEP). ResultsAll three children revealed gradual improvement in the overall CDS result as well as most of the CDS subscales. After 9 months of CI experience two younger children showed age-appropriate performance. In CAEP measurements a decrease of latency of the P1 component (an established biomarker of cortical auditory maturation) was observed in the same two children, with one achieving normal ranges of P1 latency after 9 months of CI use. ConclusionsOur novel methodological framework can be successfully applied in small children with cochlear implants. It contributes to better understanding of the general development in early implanted children. The preliminary results indicate variability in children's performance in various developmental domains and thus the need to monitor the development of each child individually and holistically.

N400 and short speech stimuli

ABSTRACT In some children who have cochlear implants (CI), the expected speech-language outcome is not achieved despite fulfilment of requirements for its successful use. This may be attributed to processing difficulties at higher levels of the auditory pathway. The aim of this study was to investigate the processing of speech stimuli at the auditory-cortex level in 20 children aged 8 to 10 years who have a hearing impairment and have been using cochlear implants, by means of cortical auditory evoked potentials (CAEP). The children were divided into two groups, depending on the outcome: 10 successful implant users and 10 unsuccessful implant users, whose speech-language development has not progressed as expected. The control group comprised of 10 age-matched children with typical hearing and speech-language development. Two double consonant+vowel syllables (CVCV) were used as stimuli, presented in an oddball paradigm that required the subjects to react consciously. Latencies and amplitudes of CAEP waves were measured. In addition to the waves that typically occur in CAEP and reflect auditory processing at the level of the auditory cortex, N400 wave (associated with semantic processing) was recorded in the normally hearing group and successful CI users, but not in the unsuccessful CI users. Additionally, successful CI users and controls had comparable latencies of the P300 wave (preceding the N400) as well. Although P300 and N400 reflect two processes, they are related so that if P300 does not reach the expected amplitude and latency, neither will N400.

Neurodevelopment and asymmetry of auditory-related responses to repetitive syllabic stimuli in preterm neonates based on frequency-domain analysis

Sensory development of the human brain begins prenatally, allowing cortical auditory responses to be recorded at an early age in preterm infants. Despite several studies focusing on the temporal characteristics of preterm infants’ cortical responses, few have been conducted on frequency analysis of these responses. In this study, we performed frequency and coherence analysis of preterm infants’ auditory responses to series of syllables and also investigated the functional brain asymmetry of preterm infants for the detection of the regularity of auditory stimuli. Cortical auditory evoked potentials (CAEPs) were recorded in 16 preterm infants with a mean recording age of 31.48 weeks gestational age (29.57–34.14 wGA) in response to a repetitive syllabic stimulus. Peak amplitudes of the frequency response at the target frequency and the first harmonic, as well as the phase coherence (PC) at the target frequency were extracted as age-dependent variables. A functional asymmetry coefficient was defined as a lateralization index for the amplitude of the target frequency at each electrode site. While the findings revealed a significant positive correlation between the mean amplitude at the target frequency vs. age (R2 = 0.263, p = 0.042), no significant correlation was observed for age-related changes of the mean amplitude at the first harmonic. A significant correlation was also observed between the mean PC and age (R2 = 0.318, p = 0.023). A right hemisphere lateralization over many channels was also generally observed. The results demonstrate that rightward lateralization for slow rate modulation, previously observed in adults, children and newborns, appears to be in place at a very young age, even in preterm infants.

Spatial hearing processing: electrophysiological documentation at subcortical and cortical levels

Objective: Recognition of target signal improves when the target and distracted sources are spatially separated, an effect defined as ‘spatial release from masking’ (SRM). The neural mechanisms underpinning SRM are complicated and still need to be identified. The aim of this study was to identify whether objective correlates of SRM can be recorded in either the brainstem or cortex (or both).Materials and methods: In response to 200 target stimulus blocks, auditory brainstem responses (ABRs), frequency-following responses (FFRs) and cortical auditory evoked potentials (CAEPs) were recorded concurrently from 13 normally hearing adults utilizing two stimulus patterns, flat and staircase, in the presence of randomized distractors at −5, 0, 5, 10 and 15 dB SNR, and in co-located and separated spatial locations.Results: FFR F0 amplitude increased for the flat stimuli at −5 dB SNR, ABR wave V latency decreased for both flat and staircase stimuli in all SNRs and for P1 and N1 latencies due to the noisy CAEPs, drawing any significant conclusion could be subject to further investigation.Conclusion: These findings suggest that SRM can be objectively recorded concurrently in both the brainstem and auditory cortex. It is speculated that the central auditory system can suppress background noise based on spatial information commencing from the brainstem and that this capability is remarkable in more difficulty listing situations. This study may pave the way to evaluate spatial processing electrophysiologically utilizing FFR amplitude, ABR and CAEPs latencies condition to confirmation of the results of this study, at least at the level of the cortex in future investigation.

Effects of Age, Cognition, and Neural Encoding on the Perception of Temporal Speech Cues.

Older adults commonly report difficulty understanding speech, particularly in adverse listening environments. These communication difficulties may exist in the absence of peripheral hearing loss. Older adults, both with normal hearing and with hearing loss, demonstrate temporal processing deficits that affect speech perception. The purpose of the present study is to investigate aging, cognition, and neural processing factors that may lead to deficits on perceptual tasks that rely on phoneme identification based on a temporal cue – vowel duration. A better understanding of the neural and cognitive impairments underlying temporal processing deficits could lead to more focused aural rehabilitation for improved speech understanding for older adults. This investigation was conducted in younger (YNH) and older normal-hearing (ONH) participants who completed three measures of cognitive functioning known to decline with age: working memory, processing speed, and inhibitory control. To evaluate perceptual and neural processing of auditory temporal contrasts, identification functions for the contrasting word-pair WHEAT and WEED were obtained on a nine-step continuum of vowel duration, and frequency-following responses (FFRs) and cortical auditory-evoked potentials (CAEPs) were recorded to the two endpoints of the continuum. Multiple linear regression analyses were conducted to determine the cognitive, peripheral, and/or central mechanisms that may contribute to perceptual performance. YNH participants demonstrated higher cognitive functioning on all three measures compared to ONH participants. The slope of the identification function was steeper in YNH than in ONH participants, suggesting a clearer distinction between the contrasting words in the YNH participants. FFRs revealed better response waveform morphology and more robust phase-locking in YNH compared to ONH participants. ONH participants also exhibited earlier latencies for CAEP components compared to the YNH participants. Linear regression analyses revealed that cortical processing significantly contributed to the variance in perceptual performance in the WHEAT/WEED identification functions. These results suggest that reduced neural precision contributes to age-related speech perception difficulties that arise from temporal processing deficits.