Search Results (30)

Background/Objectives: In the early stage of presbycusis, patients experience reduced speech perception in noisy environments despite normal audiometry, normally known as hidden hearing loss. Diagnostic indicators like the reduced amplitude of ABR wave I, elevated extended high-frequency threshold (EHT), and decreased middle ear muscle reflex (MEMR) amplitude aim to identify biomarkers of peripheral auditory pathology but remain inconsistent. Mismatch negativity (MMN) is a cortical auditory evoked potential generated when the brain detects sound changes. This study aimed to assess MMN as a diagnostic tool for hidden hearing loss in adults. Methods: Seventy-three subjects with normal hearing underwent an extended pure-tone audiogram examination ranging from 0.125 to 16 kHz and a subsequent MMN assessment with two different paradigms: a speech (ba/da) and a tone (1/2 kHz) paradigm. The MMN’s amplitude and latency were measured and analyzed. Results: The outcome shows a significant age-related effect on MMN amplitude in the speech condition (χ² = 13.0, p = 0.002). Specifically, the MMN amplitude in the 25–30-year-old group was significantly smaller than in the 20–25-year-old group (p = 0.0015, Cohen’s d = 0.63). Additionally, no further effects of age were observed on the cortical potentials examined. Also, neither tone nor speech paradigms showed a significant influence of EHT on the amplitude or latency of either MMN or P300. Conclusions: The application of MMN as an electrophysiological tool to diagnose hidden hearing loss in normal hearing adults has limitations. However, in contrast to MMN responses to tonal stimuli, the present study reveals that MMN amplitude obtained with speech stimuli may indicate early signs of central auditory deficits. Full article

Background/Objectives: Since high frequencies are susceptible to disruption in various types of hearing loss, a symptom which is common in people with tinnitus, the aim of the study was to investigate EEG cortical auditory evoked and P300 responses to both a high- and low frequency-centered oddball paradigm to begin to establish the most suitable cognitive physiologic testing conditions for those with both unimpaired hearing and those with hearing impairments. Methods: Cortical auditory evoked potential (CAEP) P1, N1, P2 and P300 (subtraction wave) peaks were identified in response to high- (standard: 6000 Hz, deviant: 8000 Hz) and low frequency (Standard: 375 Hz, Deviant: 500 Hz) oddball paradigms. Each paradigm was presented at various intensity levels. Latencies and amplitudes were then computed for each condition to assess the effects of frequency and intensity. Results: Stimulus intensity had no effect on either the high- or low frequency paradigms of P300 characteristics. In contrast, for the low frequency paradigm, intensity influenced the N1 latency and P2 amplitude, while for the high frequency paradigm intensity influenced P1 and P2 latency and P2 amplitude. Conclusions: Obligatory CAEP components responded more readily to stimulus frequency and intensity changes, and one possible consideration is that higher frequencies could play a role in the response characteristics exhibited by N1 (except for N1 amplitude) and P2, given their involvement in attentional processes linked to the detection of warning cues. P300 latency and amplitude were not influenced by such factors. These findings support the hypothesis that disentangling the cognitive from the more sensory-based response is possible, even in those with hearing loss, provided that the patient’s hearing loss is considered when determining the presentation level. While the present study was performed in participants with unimpaired hearing, these data set up future studies investigating the effectiveness of using similar methods in hearing-impaired persons. Full article

Background/Objectives: The cortical auditory evoked potential P1 response is a biomarker of cortical auditory maturation for tracking longitudinal cortical maturation in children with hearing loss after treatment with hearing aids and/or cochlear implants. In conjunction with hearing treatments, children with hearing loss commonly receive language therapy services. However, the effect of language therapy on cortical maturation in hearing loss is less well studied. Methods: This study explored auditory cortical maturation changes, using the P1 response, with coinciding language changes, utilizing the Preschool Language Scales test, following approximately six months of supplemental listening and spoken language therapy services in 39 children with hearing aids or cochlear implants. Results: Following supplemental language therapy, P1 latencies significantly decreased in all children, at a rate found to be significantly faster than expected for typical maturation. Language scores also significantly improved beyond expected maturation effects and were correlated with P1 latencies following supplemental therapy. Overall, with approximately six months of therapy, the children in this study made significantly greater gains of 9 to 10 months in total language and expressive communication. A subgroup analysis revealed that children with cochlear implants showed significantly lower language scores than their chronological age following supplemental therapy, while children with hearing aids obtained language scores that were not significantly different to their chronological age at follow-up. Conclusions: Overall, the results from this study showed that supplemental language therapy resulted in more typical auditory cortical maturation and improved language abilities and that the P1 CAEP response can objectively track neuroplastic changes in children as a function of language therapy provided in conjunction with hearing aids and CIs. Full article

Background/Objectives: Before a cochlear implant is considered, patients undergo various audiological tests to assess their suitability. One key test measures the auditory brainstem response (ABR) to acoustic stimuli. However, in some cases, even with maximum sound stimulation, no response is detected. Methods: The promontory test involves electrical stimulation near the auditory nerve, allowing patients to associate the sensation. Ideally, the electrode is placed in the middle ear after opening the eardrum. This method, along with trans-tympanic electrically evoked ABR in local anesthesia (LA-TT-EABR) and the cortical equivalent (LA-TT-EALR), helps assess the auditory nerve’s existence and excitability. The TympEALR test, utilizing a “tympanic LA-TT-EALR”, provides an alternative measurement. Previous research has shown the possibility of deriving brainstem and cortical potentials through trans-tympanic electrical stimulation, allowing for objective assessment of the auditory nerve’s integrity and potentially objectifying patient sensations. Results: Sixteen patients have been tested using TympEALR. In seven of these, we found a positive response. The morphology was similar to other electrically evoked cortical auditory responses (EALR), e.g., using cochlear implants or trans-tympanic stimulation electrodes. We observed a higher influence of electrical artifacts than in other EALRs. Conclusions: TympEALR showed positive results in nearly half of the study participants, potentially avoiding invasive procedures. TympEALR can be a valuable alternative to trans-tympanic methods. More research is needed to determine if a negative result suggests against cochlear implantation. Full article

At the cortical level, the central auditory neural system (CANS) includes primary and secondary areas. So far, much research has focused on recording fronto-central auditory evoked potentials/responses (P1-N1-P2), originating mainly from the primary auditory areas, to explore the neural processing in the auditory cortex. However, less is known about the secondary auditory areas. This review aimed to investigate and compare fronto-central and T-complex responses in populations at risk of auditory dysfunction, such as individuals with neurodevelopmental disorders. After searching the electronic databases (PubMed, Web of Science, Scopus, and Ovid), ten studies encompassing six neurodevelopmental disorders were included for the analysis. All experimental populations had atypical T-complexes, manifesting as an absence of evoked responses, shorter latency, and/or smaller amplitude. Moreover, in two experimental groups, dyslexia and attention deficit/hyperactivity disorder (ADHD), abnormal T-complex responses were observed despite the presence of normal fronto-central responses. The presence of abnormal T-complex responses in combination with normal fronto-central responses in the same population, using the same experiment, may highlight the advantage of the T-complex for indexing deficits in distinct auditory processes or regions, which the fronto-central response may not track. Full article

Background: Sensory loss may lead to intra- and cross-modal cortical reorganization. Previous research showed a significant correlation between the cross-modal contribution of the right auditory cortex to visual evoked potentials (VEP) and speech perception in cochlear implant (CI) users with prelingual hearing loss (HL), but not in those with postlingual HL. The present study aimed to explore the cortical reorganization induced by postlingual HL, particularly in the right temporal region, and how it correlates with speech perception outcome with a CI. Material and Methods: A total of 53 adult participants were divided into two groups according to hearing ability: 35 had normal hearing (NH) (mean age = 62.10 years (±7.48)) and 18 had profound postlingual HL (mean age = 63.78 years (±8.44)). VEPs, using a 29-channel electroencephalogram (EEG) system, were recorded preoperatively in the 18 patients scheduled for cochlear implantation and in 35 NH adults who served as the control group. Amplitudes and latencies of the P100, N100, and P200 components were analyzed across frontal, temporal, and occipital areas and compared between NH and HL subjects using repeated measures ANOVA. For the HL group, speech perception in quiet was assessed at 6 and 12 months of CI use. Results: No difference was found in amplitudes or latencies of the P100, N100, and P200 VEP components between the NH and HL groups. Further analysis using Spearman correlations between preoperative amplitudes and latencies of the P100, N100, and P200 VEP components at the right temporal electrode position T8 and postoperative speech perception showed that the HL group had either significantly higher or significantly lower amplitudes of the P200 component at the right temporal electrode position T8 compared to the NH controls. The HL subgroup with higher amplitudes had better speech perception than the subgroup with lower amplitudes at 6 months and 12 months of CI use. Conclusions: Preoperative evaluation of cortical plasticity can reveal plasticity profiles, which might help to better predict postoperative speech outcomes and adapt the rehabilitation regimen after CI activation. Further research is needed to understand the susceptibility of each component to cross-modal reorganization and their specific contribution to outcome prediction. Full article

Background: Many studies have demonstrated the benefits of long-term music training (i.e., musicianship) on the neural processing of sound, including simple tones and speech. However, the effects of musicianship on the encoding of simultaneously presented pitches, in the form of complex musical chords, is less well established. Presumably, musicians’ stronger familiarity and active experience with tonal music might enhance harmonic pitch representations, perhaps in an attention-dependent manner. Additionally, attention might influence chordal encoding differently across the auditory system. To this end, we explored the effects of long-term music training and attention on the processing of musical chords at the brainstem and cortical levels. Method: Young adult participants were separated into musician and nonmusician groups based on the extent of formal music training. While recording EEG, listeners heard isolated musical triads that differed only in the chordal third: major, minor, and detuned (4% sharper third from major). Participants were asked to correctly identify chords via key press during active stimulus blocks and watched a silent movie during passive blocks. We logged behavioral identification accuracy and reaction times and calculated information transfer based on the behavioral chord confusion patterns. EEG data were analyzed separately to distinguish between cortical (event-related potential, ERP) and subcortical (frequency-following response, FFR) evoked responses. Results: We found musicians were (expectedly) more accurate, though not faster, than nonmusicians in chordal identification. For subcortical FFRs, responses showed stimulus chord effects but no group differences. However, for cortical ERPs, whereas musicians displayed P2 (~150 ms) responses that were invariant to attention, nonmusicians displayed reduced P2 during passive listening. Listeners’ degree of behavioral information transfer (i.e., success in distinguishing chords) was also better in musicians and correlated with their neural differentiation of chords in the ERPs (but not high-frequency FFRs). Conclusions: Our preliminary results suggest long-term music training strengthens even the passive cortical processing of musical sounds, supporting more automated brain processing of musical chords with less reliance on attention. Our results also suggest that the degree to which listeners can behaviorally distinguish chordal triads is directly related to their neural specificity to musical sounds primarily at cortical rather than subcortical levels. FFR attention effects were likely not observed due to the use of high-frequency stimuli (>220 Hz), which restrict FFRs to brainstem sources. Full article

Cortical auditory evoked potentials (CAEPs) indicate that noise degrades auditory neural encoding, causing decreased peak amplitude and increased peak latency. Different types of noise affect CAEP responses, with greater informational masking causing additional degradation. In noisy conditions, attention can improve target signals’ neural encoding, reflected by an increased CAEP amplitude, which may be facilitated through various inhibitory mechanisms at both pre-attentive and attentive levels. While previous research has mainly focused on inhibition effects during attentive auditory processing in noise, the impact of noise on the neural response during the pre-attentive phase remains unclear. Therefore, this preliminary study aimed to assess the auditory gating response, reflective of the sensory inhibitory stage, to repeated vowel pairs presented in background noise. CAEPs were recorded via high-density EEG in fifteen normal-hearing adults in quiet and noise conditions with low and high informational masking. The difference between the average CAEP peak amplitude evoked by each vowel in the pair was compared across conditions. Scalp maps were generated to observe general cortical inhibitory networks in each condition. Significant gating occurred in quiet, while noise conditions resulted in a significantly decreased gating response. The gating function was significantly degraded in noise with less informational masking content, coinciding with a reduced activation of inhibitory gating networks. These findings illustrate the adverse effect of noise on pre-attentive inhibition related to speech perception. Full article

A significant portion of hearing-impaired children have additional disabilities, but data about the maturation of their auditory cortex are scarce. In these children, behavioral tests are often unreliable, and objective tests are needed for diagnostics and follow-up. This study aimed to explore auditory cortical maturation and language development, and the usability of an objective electroencephalogram-based biomarker in children with multiple disabilities. In 65 hearing aid and cochlear implant users (36 females; 36 with multiple disabilities; 44.3 ± 18.5 months of age, mean ± SD), auditory processing was examined using the P1 cortical auditory evoked response biomarker, and language development with the Preschool Language Scales 5th edition (PLS-5). During the study, all of the children received intensive extra language therapy for six months. No significant differences were found between the groups in P1 latency development, the proportion of abnormal P1 latencies, or the number of children whose P1 latencies changed from abnormal to normal during the study. The PLS-5 total language scores, auditory comprehension scores, or expressive communication scores did not differ between groups either. The P1 latencies showed meaningful negative correlations with the language scores. The results suggest that auditory cortex development is similar in hearing-impaired children with/without additional disabilities, and the P1 biomarker is a feasible tool to evaluate central auditory maturation in children with multiple disabilities. Full article

Auditory and visually evoked potentials (EP) have the ability to monitor cognitive changes after concussion. In the literature, decreases in EP are commonly reported; however, a subset of studies shows increased cortical activity after injury. We studied auditory and visual EP in 4-week-old female Yorkshire piglets (N = 35) divided into anesthetized sham, and animals subject to single (sRNR) and repeated (rRNR) rapid non-impact head rotations (RNR) in the sagittal direction. Two-tone auditory oddball tasks and a simple white-light visual stimulus were evaluated in piglets pre-injury, and at days 1, 4- and 7 post injury using a 32-electrode net. Traditional EP indices (N1, P2 amplitudes and latencies) were extracted, and a piglet model was used to source-localize the data to estimate brain regions related to auditory and visual processing. In comparison to each group’s pre-injury baselines, auditory Eps and brain activity (but not visual activity) were decreased in sham. In contrast, sRNR had increases in N1 and P2 amplitudes from both stimuli. The rRNR group had decreased visual N1 amplitudes but faster visual P2 latencies. Auditory and visual EPs have different change trajectories after sRNR and rRNR, suggesting that injury biomechanics are an important factor to delineate neurofunctional deficits after concussion. Full article

The combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) offers an unparalleled opportunity to study cortical physiology by characterizing brain electrical responses to external perturbation, called transcranial-evoked potentials (TEPs). Although these reflect cortical post-synaptic potentials, they can be contaminated by auditory evoked potentials (AEPs) due to the TMS click, which partly show a similar spatial and temporal scalp distribution. Therefore, TEPs and AEPs can be difficult to disentangle by common statistical methods, especially in conditions of suboptimal AEP suppression. In this work, we explored the ability of machine learning algorithms to distinguish TEPs recorded with masking of the TMS click, AEPs and non-masked TEPs in a sample of healthy subjects. Overall, our classifier provided reliable results at the single-subject level, even for signals where differences were not shown in previous works. Classification accuracy (CA) was lower at the group level, when different subjects were used for training and test phases, and when three stimulation conditions instead of two were compared. Lastly, CA was higher when average, rather than single-trial TEPs, were used. In conclusion, this proof-of-concept study proposes machine learning as a promising tool to separate pure TEPs from those contaminated by sensory input. Full article

Neural electrodes are core devices for research in neuroscience, neurological diseases, and neural–machine interfacing. They build a bridge between the cerebral nervous system and electronic devices. Most of the neural electrodes in use are based on rigid materials that differ significantly from biological neural tissue in flexibility and tensile properties. In this study, a liquid-metal (LM) -based 20-channel neural electrode array with a platinum metal (Pt) encapsulation material was developed by microfabrication technology. The in vitro experiments demonstrated that the electrode has stable electrical properties and excellent mechanical properties such as flexibility and bending, which allows the electrode to form conformal contact with the skull. The in vivo experiments also recorded electroencephalographic signals using the LM-based electrode from a rat under low-flow or deep anesthesia, including the auditory-evoked potentials triggered by sound stimulation. The auditory-activated cortical area was analyzed using source localization technique. These results indicate that this 20-channel LM-based neural electrode array satisfies the demands of brain signal acquisition and provides high-quality-electroencephalogram (EEG) signals that support source localization analysis. Full article

Dysregulation of high-frequency neuronal oscillations has been implicated in the pathophysiology of schizophrenia. Chronic methamphetamine (METH) use can induce psychosis similar to paranoid schizophrenia. The current study in mice aimed to determine the effect of chronic METH treatment on ongoing and evoked neuronal oscillations. C57BL/6 mice were treated with METH or vehicle control for three weeks and implanted with extradural recording electrodes. Two weeks after the last METH injection, mice underwent three EEG recording sessions to measure ongoing and auditory-evoked gamma and beta oscillatory power in response to an acute challenge with METH (2 mg/kg), the NMDA receptor antagonist MK-801 (0.3 mg/kg), or saline control. A separate group of mice pretreated with METH showed significantly greater locomotor hyperactivity to an acute METH challenge, confirming long-term sensitisation. Chronic METH did not affect ongoing or evoked gamma or beta power. Acute MK-801 challenge reduced ongoing beta power whereas acute METH challenge significantly increased ongoing gamma power. Both MK-801 and METH challenge suppressed evoked gamma power. Chronic METH treatment did not modulate these acute drug effects. There were minor effects of chronic METH and acute METH and MK-801 on selected components of event-related potential (ERP) waves. In conclusion, chronic METH treatment did not exert neuroplastic effects on the regulation of cortical gamma oscillations in a manner consistent with schizophrenia, despite causing behavioural sensitisation. Full article

Prenatal exposure to ZIKV can cause neurologic and auditory damage. The electrophysiological responses obtained by Cortical Auditory Evoked Potentials (CAEP) may provide an objective method to investigate the function of cortical auditory pathways in children exposed to ZIKV. This case series analyzed the findings of CAEP in prenatal-period ZIKV-exposed children with and without microcephaly. The CAEP was performed in a total of 24 children. Five magnetic resonance imaging (MRI) images of the inner ear and brain of microcephalic children were analyzed and compared with CAEP measurements. Ventriculomegaly (80%), cortical/subcortical calcification (80%), and brain reduction (60%) were the most common alterations in the MRI. The P1-N1-P2 complex of the CAEP was observed in all children evaluated. The peak N2 was absent in two children. In the comparison of the CAEP measurements between the groups, children with microcephaly presented a higher amplitude of P2 (p = 0.017), which may reflect immaturity of the auditory pathways. Microcephalic and normocephalic children with prenatal exposure to ZIKV presented with the mandatory components of the CAEPs, regardless of changes in the CNS, suggesting that this population has, to some extent, the cortical ability to process sound stimuli preserved. Full article

Grounded cognition theory postulates that cognitive processes related to motor or sensory content are processed by brain networks involved in motor execution and perception, respectively. Processing words with auditory features was shown to activate the auditory cortex. Our study aimed at determining whether onomatopoetic verbs (e.g., “tröpfeln”—to dripple), whose articulation reproduces the sound of respective actions, engage the auditory cortex more than non-onomatopoetic verbs. Alpha and beta brain frequencies as well as evoked-related fields (ERFs) were targeted as potential neurophysiological correlates of this linguistic auditory quality. Twenty participants were measured with magnetoencephalography (MEG) while semantically processing visually presented onomatopoetic and non-onomatopoetic German verbs. While a descriptively stronger left temporal alpha desynchronization for onomatopoetic verbs did not reach statistical significance, a larger ERF for onomatopoetic verbs emerged at about 240 ms in the centro-parietal area. Findings suggest increased cortical activation related to onomatopoeias in linguistically relevant areas. Full article