High-frequency (>60 Hz) neuroelectric signals likely have functional roles distinct from low-frequency (<30 Hz) signals. While high-gamma activity (>60 Hz) does not simply equate to neuronal spiking, they are highly correlated, having similar information encoding. High-gamma activity is typically considered broadband and poorly phase-locked to sensory stimuli and thus is typically analyzed after transformations into absolute amplitude or spectral power. However, those analyses discard signal polarity, compromising the interpretation of neuroelectric events that are essentially dipolar. In the spectrotemporal profiles of field potentials in auditory cortex, we show high-frequency spectral peaks not phase-locked to sound onset, which follow the broadband peak of phase-locked onset responses. Isolating the signal components comprising the high-frequency peaks reveals narrow-band high-frequency oscillatory events, whose instantaneous frequency changes rapidly from >150 to 60 Hz, which may underlie broadband high-frequency spectral peaks in previous reports. The laminar amplitude distributions of the isolated activity had two peak positions, while the laminar phase patterns showed a counterphase relationship between those peaks, indicating the formation of dipoles. Our findings suggest that nonphase-locked HGA arises in part from oscillatory or recurring activity of supragranular-layer neuronal ensembles in auditory cortex.

BACKGROUND:  Chronic unilateral hearing loss causes imbalanced auditory input to the brain that triggers cortical reorganization. The effect of sensorineural hearing loss on the central auditory system (CAS) has been thoroughly studied, while there is a paucity of research on the effect of conductive hearing loss (CHL). The aim of this study was to assess the P1-N1-P2 cortical auditory evoked response potential (CAEP) in adult individuals with chronic acquired unilateral CHL.
METHODS:  This study included 108 participants of both genders: 54 patients with unilateral chronic CHL who were compared to well-matched 54 controls. All were subjected to history-taking, otologic examination, basic audiological evaluation, and bone conduction N1-P2 CAEP.
RESULTS:  The affected ears of the cases showed highly statistically significant shorter CAEPs N1, P2, N1-P2 latencies but not P1, and showed highly statistically significant larger N1, P2, N1P2, amplitude than the control group. Latencies decreased and amplitudes increased as the degree of CHL increased, but were not affected by patients\' age, side, or duration of the CHL. Cases with tinnitus had statistically significant and worse results than those without tinnitus.
CONCLUSIONS:  Unilateral chronic CHL might enhance neurocortical plasticity, with greater changes occurring at greater degrees of the CHL.

The current study investigated the effect of lower frequency input on stream segregation acuity in older, normal hearing adults. Using event-related brain potentials (ERPs) and perceptual performance measures, we previously showed that stream segregation abilities were less proficient in older compared to younger adults. However, in that study we used frequency ranges greater than 1500 Hz. In the current study, we lowered the target frequency range below 1500 Hz and found similar stream segregation abilities in younger and older adults. These results indicate that the perception of complex auditory scenes is influenced by the spectral content of the auditory input and suggest that lower frequency ranges of input in older adults may facilitate listening ability in complex auditory environments. These results also have implications for the advancement of prosthetic devices.

Congenital or early-onset unilateral hearing loss (UHL) can disrupt the normal development of the auditory system. In extreme cases of UHL (i.e., single sided deafness), consistent cochlear implant use during sensitive periods resulted in cortical reorganization that partially reversed the detrimental effects of unilateral sensory deprivation. There is a gap in knowledge, however, regarding cortical plasticity i.e. the brain\'s capacity to adapt, reorganize, and develop binaural pathways in milder degrees of UHL rehabilitated by a hearing aid (HA). The current study was set to investigate early-stage cortical processing and electrophysiological manifestations of binaural processing by means of cortical auditory evoked potentials (CAEPs) to speech sounds, in children with moderate to severe-to-profound UHL using a HA. Fourteen children with UHL (CHwUHL), 6-14 years old consistently using a HA for 3.5 (±2.3) years participated in the study. CAEPs were elicited to the speech sounds /m/, /g/, and /t/ in three listening conditions: monaural [Normal hearing (NH), HA], and bilateral [BI (NH + HA)]. Results indicated age-appropriate CAEP morphology in the NH and BI listening conditions in all children. In the HA listening condition: (1) CAEPs showed similar morphology to that found in the NH listening condition, however, the mature morphology observed in older children in the NH listening condition was not evident; (2) P1 was elicited in all but two children with severe-to-profound hearing loss, to at least one speech stimuli, indicating effective audibility; (3) A significant mismatch in timing and synchrony between the NH and HA ear was found; (4) P1 was sensitive to the acoustic features of the eliciting stimulus and to the amplification characteristics of the HA. Finally, a cortical binaural interaction component (BIC) was derived in most children. In conclusion, the current study provides first-time evidence for cortical plasticity and partial reversal of the detrimental effects of moderate to severe-to-profound UHL rehabilitated by a HA. The derivation of a cortical biomarker of binaural processing implies that functional binaural pathways can develop when sufficient auditory input is provided to the affected ear. CAEPs may thus serve as a clinical tool for assessing, monitoring, and managing CHwUHL using a HA.

BACKGROUND: Ketamine has recently attracted considerable attention for its rapid effects on patients with major depressive disorder, including treatment-resistant depression (TRD). Despite ketamine\'s promising results in treating depression, a significant number of patients do not respond to the treatment, and predicting who will benefit remains a challenge. Although its antidepressant effects are known to be linked to its action as an antagonist of the N-methyl-D-aspartate (NMDA) receptor, the precise mechanisms that determine why some patients respond and others do not are still unclear.
OBJECTIVE: This study aims to understand the computational mechanisms underlying changes in the auditory mismatch negativity (MMN) response following treatment with intravenous ketamine. Moreover, we aim to link the computational mechanisms to their underlying neural causes and use the parameters of the neurocomputational model to make individual treatment predictions.
METHODS: This is a prospective study of 30 patients with TRD who are undergoing intravenous ketamine therapy. Prior to 3 out of 4 ketamine infusions, EEG will be recorded while patients complete the auditory MMN task. Depression, suicidality, and anxiety will be assessed throughout the study and a week after the last ketamine infusion. To translate the effects of ketamine on the MMN to computational mechanisms, we will model changes in the auditory MMN using the hierarchical Gaussian filter, a hierarchical Bayesian model. Furthermore, we will employ a conductance-based neural mass model of the electrophysiological data to link these computational mechanisms to their neural causes.
CONCLUSIONS: The findings of this study may improve understanding of the mechanisms underlying response and resistance to ketamine treatment in patients with TRD. The parameters obtained from fitting computational models to EEG recordings may facilitate single-patient treatment predictions, which could provide clinically useful prognostic information.
BACKGROUND: Clinicaltrials.gov NCT05464264. Registered June 24, 2022.

随着皮层诱发电位技术的日趋成熟，越来越多的研究通过失匹配反应来客观评估婴幼儿听觉中枢系统发育情况，本文综述了失匹配反应的前注意成分正性-失匹配反应和晚期辨别负波的基本特点及其在婴幼儿中的研究进展，为婴幼儿听觉加工机制的深入研究提供思路。.

Objective: To investigate the early auditory discrimination of vowels, consonants and lexical tones in prelingually-deafened children with cochlear implants (CI) using auditory event-related potentials. Methods: Nineteen prelingually-deafened CI children and 19 normal hearing (NH) children were recruited in this study. A multi-deviant oddball paradigm was constructed using the monosyllable/ta1/as the standard stimulus and monosyllables/tu1/,/te1/, /da1/,/ra1/,/ta4/and/ta2/as the deviant stimuli. The event-related potentials evoked by vowel, consonant and lexical tone contrasts were recorded and analyzed in the two groups. Results: NH children showed robust mismatch negativities (MMNs) to vowel, consonant and lexical tone contrasts (P<0.05), whereas CI children only showed positive mismatch responses (pMMRs) and P3a responses to the vowel (P<0.05) and consonant contrasts (P<0.05) and no significant event-related potential to the lexical tone contrasts (P>0.05). The longer pMMR and P3a peak latencies (P<0.01) but similar amplitudes (P>0.05) were found in CI children than in NH children. CI children showed weaker phase synchronization of θ oscillations than NH children (P<0.05). The duration of CI use was positively correlated with the scores of Categories of Auditory Performance (CAP) (P=0.004), Speech Intelligibility Rate (SIR) (P=0.044) and Meaningful Auditory Integration Scale (MAIS) (P=0.001) in CI children. Conclusions: Prelingually-deafened CI children can process vowels and consonants at an early stage. However, their ability of processing speech, especially lexical tones, is still more immature compared with their NH peers. The event-related potentials could be objective electrophysiological indicators reflecting the maturity of CI children\'s auditory speech functions. Long-term CI use is beneficial for prelingually-deafened children to improve auditory and speech performance.
目的： 利用听觉事件相关电位评估语前聋儿童人工耳蜗（cochlear implant，CI）植入者对元音、辅音和声调的早期听觉加工能力。 方法： 2021年2月到2024年2月期间招募19例语前聋CI儿童（男12例、女7例，年龄3~8岁，平均6.0岁）和19例听力正常（normal hearing，NH）儿童（男12例、女7例，年龄4~9岁，平均6.8岁）。使用单音节/ta1/作为标准刺激，/tu1/，/te1/，/da1/，/ra1/，/ta4/和/ta2/作为偏差刺激，构建多偏差oddball范式。记录并分析两组儿童由元音、辅音和声调变化诱发的事件相关电位。应用SPSS 24.0软件对数据进行统计学分析。 结果： NH儿童对元音、辅音和声调变化均表现出显著的失匹配负波（mismatch negativity，MMN）（P<0.05），而CI儿童对元音和辅音变化仅表现出正向失匹配反应（positive mismatch response，pMMR）（P<0.05）和P3a反应（P<0.05），且未对声调变化表现出任何事件相关电位（P>0.05）。与NH儿童相比，CI儿童的pMMR和P3a潜伏期更长（P<0.01），两组间幅值差异无统计学意义（P>0.05）。时频分析显示，CI儿童的θ频段神经振荡同步性较NH儿童低（P<0.05）。相关性分析显示，CI儿童的CI使用时间与听觉能力分级量表（Categories of Auditory Performance，CAP）（P=0.004）、言语可懂度分级量表（Speech Intelligibility Rate，SIR）（P=0.044）和有意义听觉整合量表（Meaningful Auditory Integration Scale，MAIS）（P=0.001）得分呈正相关。 结论： 语前聋CI儿童对元音和辅音具备一定的早期听觉加工能力，但与同龄NH儿童相比，语前聋CI儿童对语音尤其是声调的加工能力仍不成熟。事件相关电位可作为反映CI儿童听觉言语功能成熟度的客观电生理指标。坚持长期佩戴CI有助于语前聋儿童听觉言语能力的提高。.

The aim of the present study was to identify cognitive alterations, as indicated by event-related potentials (ERPs), after one month of daily exposure to theta binaural beats (BBs) for 10 minutes. The recruited healthy subjects (n = 60) were equally divided into experimental and control groups. For a month, the experimental group was required to practice BBs listening daily, while the control group did not. ERPs were assessed at three separate visits over a span of one month, with a two-week interval between each visit. At each visit, ERPs were measured before and after listening. The auditory and visual ERPs significantly increased the auditory and visual P300 amplitudes consistently at each visit. BBs enhanced the auditory N200 amplitude consistently across all visits, but the visual N200 amplitude increased only at the second and third visits. Compared to the healthy controls, daily exposure to BBs for two weeks resulted in increased auditory P300 amplitude. Additionally, four weeks of BBs exposure not only increased auditory P300 amplitude but also reduced P300 latency. These preliminary findings suggest that listening to BBs at 6 Hz for 10 minutes daily may enhance certain aspects of cognitive function. However, further research is needed to confirm these effects and to understand the underlying mechanisms. Identifying the optimal duration and practice of listening to 6 Hz BBs could potentially contribute to cognitive enhancement strategies in healthy individuals.

This study investigated whether the brain utilizes morphologically induced tones for semantic processing during online speech perception. An auditory comprehension task was conducted while measuring event-related potentials (ERPs). The study tested whether a discrepancy between contextual expectations and the tonal realizations of the target word would yield an N400 effect, indicative of semantic processing difficulty. An N400 effect was observed, reflecting integration difficulty due to semantic anomalies caused by incongruent tones. Additionally, the ERPs in the congruent conditions were modulated by the cohort entropy of the target word indicating lexical competition. The late negativity observed in this study encompasses both the N400 and preactivation negativity. This overlap underscores the brain\'s potential for rapidly connecting form and meaning from different sources within the word, relying on statistically based prediction in semantic processing.

The purpose of this study was to investigate the peripheral and central auditory pathways in adult individuals after COVID-19 infection.
A total of 44 individuals aged between 19 and 58 years, of both genders, post-COVID-19 infection, confirmed by serological tests, with no previous hearing complaints and no risk factors for hearing loss, were assessed. All the participants underwent the following procedures: pure tone audiometry, logoaudiometry, immitanciometry, and Brainstem Auditory Evoked Potentials (BAEP), in addition to answering a questionnaire about auditory symptoms.
Thirteen individuals (29.5 %) had some hearing threshold impairment, mainly sensorineural hearing loss. In the BAEP, 18 individuals (40.9 %) presented longer latencies, mainly in waves III and V. According to the questionnaire answers, 3 individuals (9.1 %) reported worsened hearing and 7 (15.9 %) tinnitus that emerged after the infection. As for the use of ototoxic drugs during treatment, 7 individuals (15.9 %) reported their use, of which 5 showed abnormalities in peripheral and/or central auditory assessments.
Considering the self-reported hearing complaints after COVID-19 infection and the high rate of abnormalities found in both peripheral and central audiological assessments, it is suggested that the new COVID-19 may compromise the auditory system. Due to the many variables involved in this study, the results should be considered with caution. However, it is essential that audiological evaluations are carried out on post-COVID-19 patients in order to assess the effects of the infection in the short, medium, and long term. Future longitudinal investigations are important for a better understanding of the auditory consequences of COVID-19.