Sex differences during development in cortical temporal processing and event related potentials in wild-type and fragile X syndrome model mice.

BACKGROUND: Autism spectrum disorder (ASD) is currently diagnosed in approximately 1 in 44 children in the United States, based on a wide array of symptoms, including sensory dysfunction and abnormal language development. Boys are diagnosed ~ 3.8 times more frequently than girls. Auditory temporal processing is crucial for speech recognition and language development. Abnormal development of temporal processing may account for ASD language impairments. Sex differences in the development of temporal processing may underlie the differences in language outcomes in male and female children with ASD. To understand mechanisms of potential sex differences in temporal processing requires a preclinical model. However, there are no studies that have addressed sex differences in temporal processing across development in any animal model of ASD. METHODS: To fill this major gap, we compared the development of auditory temporal processing in male and female wildtype (WT) and Fmr1 knock-out (KO) mice, a model of Fragile X Syndrome (FXS), a leading genetic cause of ASD-associated behaviors. Using epidural screw electrodes, we recorded auditory event related potentials (ERP) and auditory temporal processing with a gap-in-noise auditory steady state response (ASSR) paradigm at young (postnatal (p)21 and p30) and adult (p60) ages from both auditory and frontal cortices of awake, freely moving mice. RESULTS: The results show that ERP amplitudes were enhanced in both sexes of Fmr1 KO mice across development compared to WT counterparts, with greater enhancement in adult female than adult male KO mice. Gap-ASSR deficits were seen in the frontal, but not auditory, cortex in early development (p21) in female KO mice. Unlike male KO mice, female KO mice show WT-like temporal processing at p30. There were no temporal processing deficits in the adult mice of both sexes. CONCLUSIONS: These results show a sex difference in the developmental trajectories of temporal processing and hypersensitive responses in Fmr1 KO mice. Male KO mice show slower maturation of temporal processing than females. Female KO mice show stronger hypersensitive responses than males later in development. The differences in maturation rates of temporal processing and hypersensitive responses during various critical periods of development may lead to sex differences in language function, arousal and anxiety in FXS.

The Latency of Auditory Event-Related Potential P300 Prolonged in School-Age Students with Unilateral Hearing Loss in a Mandarin Learning Environment.

Our study investigated the differences in speech performance and neurophysiological response in groups of school-age children with unilateral hearing loss (UHL) who were otherwise typically developing (TD). We recruited a total of 16 primary school-age children for our study (UHL = 9/TD = 7), who were screened by doctors at Shin Kong Wu-Ho-Su Memorial Hospital. We used the Peabody Picture Vocabulary Test-Revised (PPVT-R) to test word comprehension, and the PPVT-R percentile rank (PR) value was proportional to the auditory memory score (by The Children's Oral Comprehension Test) in both groups. Later, we assessed the latency and amplitude of auditory ERP P300 and found that the latency of auditory ERP P300 in the UHL group was prolonged compared with that in the TD group. Although students with UHL have typical hearing in one ear, based on our results, long-term UHL might be the cause of atypical organization of brain areas responsible for auditory processing or even visual perceptions attributed to speech delay and learning difficulties.

Distributed representations of prediction error signals across the cortical hierarchy are synergistic.

A relevant question concerning inter-areal communication in the cortex is whether these interactions are synergistic. Synergy refers to the complementary effect of multiple brain signals conveying more information than the sum of each isolated signal. Redundancy, on the other hand, refers to the common information shared between brain signals. Here, we dissociated cortical interactions encoding complementary information (synergy) from those sharing common information (redundancy) during prediction error (PE) processing. We analyzed auditory and frontal electrocorticography (ECoG) signals in five common awake marmosets performing two distinct auditory oddball tasks and investigated to what extent event-related potentials (ERP) and broadband (BB) dynamics encoded synergistic and redundant information about PE processing. The information conveyed by ERPs and BB signals was synergistic even at lower stages of the hierarchy in the auditory cortex and between auditory and frontal regions. Using a brain-constrained neural network, we simulated the synergy and redundancy observed in the experimental results and demonstrated that the emergence of synergy between auditory and frontal regions requires the presence of strong, long-distance, feedback, and feedforward connections. These results indicate that distributed representations of PE signals across the cortical hierarchy can be highly synergistic.

Dissecting Mismatch Negativity: Early and Late Subcomponents for Detecting Deviants in Local and Global Sequence Regularities.

Mismatch negativity (MMN) is commonly recognized as a neural signal of prediction error evoked by deviants from the expected patterns of sensory input. Studies show that MMN diminishes when sequence patterns become more predictable over a longer timescale. This implies that MMN is composed of multiple subcomponents, each responding to different levels of temporal regularities. To probe the hypothesized subcomponents in MMN, we record human electroencephalography during an auditory local-global oddball paradigm where the tone-to-tone transition probability (local regularity) and the overall sequence probability (global regularity) are manipulated to control temporal predictabilities at two hierarchical levels. We find that the size of MMN is correlated with both probabilities and the spatiotemporal structure of MMN can be decomposed into two distinct subcomponents. Both subcomponents appear as negative waveforms, with one peaking early in the central-frontal area and the other late in a more frontal area. With a quantitative predictive coding model, we map the early and late subcomponents to the prediction errors that are tied to local and global regularities, respectively. Our study highlights the hierarchical complexity of MMN and offers an experimental and analytical platform for developing a multitiered neural marker applicable in clinical settings.

Decoding predicted musical notes from omitted stimulus potentials.

Electrophysiological studies have investigated predictive processing in music by examining event-related potentials (ERPs) elicited by the violation of musical expectations. While several studies have reported that the predictability of stimuli can modulate the amplitude of ERPs, it is unclear how specific the representation of the expected note is. The present study addressed this issue by recording the omitted stimulus potentials (OSPs) to avoid contamination of bottom-up sensory processing with top-down predictive processing. Decoding of the omitted content was attempted using a support vector machine, which is a type of machine learning. ERP responses to the omission of four target notes (E, F, A, and C) at the same position in familiar and unfamiliar melodies were recorded from 25 participants. The results showed that the omission N1 were larger in the familiar melody condition than in the unfamiliar melody condition. The decoding accuracy of the four omitted notes was significantly higher in the familiar melody condition than in the unfamiliar melody condition. These results suggest that the OSPs contain discriminable predictive information, and the higher the predictability, the more the specific representation of the expected note is generated.

Frequency-dependent temporary threshold shifts in the Eastern painted turtle (Chrysemys picta picta).

Testudines are a highly threatened group facing an array of stressors, including alteration of their sensory environment. Underwater noise pollution has the potential to induce hearing loss and disrupt detection of biologically important acoustic cues and signals. To examine the conditions that induce temporary threshold shifts (TTS) in hearing in the freshwater Eastern painted turtle (Chrysemys picta picta), three individuals were exposed to band limited continuous white noise (50-1000 Hz) of varying durations and amplitudes (sound exposure levels ranged from 151 to 171 dB re 1 µPa2 s). Control and post-exposure auditory thresholds were measured and compared at 400 and 600 Hz using auditory evoked potential methods. TTS occurred in all individuals at both test frequencies, with shifts of 6.1-41.4 dB. While the numbers of TTS occurrences were equal between frequencies, greater shifts were observed at 600 Hz, a frequency of higher auditory sensitivity, compared to 400 Hz. The onset of TTS occurred at 154 dB re 1 µPa2 s for 600 Hz, compared to 158 dB re 1 µPa2 s at 400 Hz. The 400-Hz onset and patterns of TTS growth and recovery were similar to those observed in previously studied Trachemys scripta elegans, suggesting TTS may be comparable across Emydidae species.

Exploring the relationship between auditory late latency response and language age in children using cochlear implant.

AIM & OBJECTIVES: The study aimed to compare P1 latency and P1-N1 amplitude with receptive and expressive language ages in children using cochlear implant (CI) in one ear and a hearing aid (HA) in non-implanted ear. METHODS: The study included 30 children, consisting of 18 males and 12 females, aged between 48 and 96 months. The age at which the children received CI ranged from 42 to 69 months. A within-subject research design was utilized and participants were selected through purposive sampling. Auditory late latency responses (ALLR) were assessed using the Intelligent hearing system to measure P1 latency and P1-N1 amplitude. The assessment checklist for speech-language skills (ACSLS) was employed to evaluate receptive and expressive language age. Both assessments were conducted after cochlear implantation. RESULTS: A total of 30 children participated in the study, with a mean implant age of 20.03 months (SD: 8.14 months). The mean P1 latency and P1-N1 amplitude was 129.50 ms (SD: 15.05 ms) and 6.93 µV (SD: 2.24 µV) respectively. Correlation analysis revealed no significant association between ALLR measures and receptive or expressive language ages. However, there was significant negative correlation between the P1 latency and implant age (Spearman's rho = -0.371, p = 0.043). CONCLUSIONS: The study suggests that P1 latency which is an indicative of auditory maturation, may not be a reliable marker for predicting language outcomes. It can be concluded that language development is likely to be influenced by other factors beyond auditory maturation alone.

[A study of mismatched negative in normal hearing patients of different ages].

Objective:To study the characteristics of Mismatch negativity（MMN） in normal hearing patients of different ages, and to compare the MMN of normal hearing subjects at different ages to explore the differences in MMN between different ages. Methods:MMN test was performed on both ears using the classic Oddball mode. A frequency of 1 000 Hz（standard stimuli） and 2 000 Hz（deviant stimuli） was used to evoked the MMN. According to different age groups: the juvenile group（7-17 years old）, the youth group（18-44 years old）, the middle-aged group（45-59 years old）, and the elderly group（60-75 years old）, with 25 cases in each group. The MMN characteristics of normal hearing subjects in different age groups were analyzed statistically and the differences between groups were compared. All subjects underwent pure tone threshold test, tympanic reactance test and ABR test before MMN test. Results:MMN waveform could be elicited from both ears of 100 subjects. Among them, the average latency of the juvenile group was（159.70±20.34） ms while the average amplitude was（4.34±2.26） µV, For the youth group, the average latency was（166.01±28.67） ms and the average amplitude was（3.70±2.28） µV. Then in the middle-aged group, the average latency was（175.16±37.24） ms, meanwhile, the average amplitude was（2.69±0.84） µV. Finally, the elderly group has an average latency of（178.03±14.37） ms and an average amplitude of（2.11±0.70） µV. Therefore, there was no statistical difference in latency and amplitude between all groups（P>0.05）, and there was no statistical difference in latency and amplitude between left and right ears among all subjects as a whole（P>0.05）. However, when the left and right ears of all groups were compared, it was found that the latency between the left and right ears of the Juvenile group had statistical significance（P<0.05）, and the amplitude difference was not statistically significant（P>0.05）, while the latency and amplitude differences between the left and right ears of other groups had no statistical significance（P>0.05）. There were also no significant differences in latency and amplitude between men and women（P>0.05）. Conclusion:There was no statistically significant difference in the latency and amplitude of mismatched negative among normal hearing subjects of different ages, and no statistically significant difference in the MMN latency and amplitude between the left and right ears of subjects and between men and women. Therefore, the study inferred that the auditory cerebral cortex of subjects aged 7-75 years old maintained a stable state for a long time after maturity, and the latency and amplitude of mismatched negative waves were relatively stable. It is not affected by age, gender and ear side, and can stably reflect the auditory cortex function of the subjects. It has broad application prospects in clinical practice, and provides a reliable detection means for future research on the changes of the auditory cerebral cortex of patients, which is worthy of our further research and clinical promotion.

Modulatory Effects on Laminar Neural Activity Induced by Near-Infrared Light Stimulation with a Continuous Waveform to the Mouse Inferior Colliculus In Vivo.

Infrared neural stimulation (INS) is a promising area of interest for the clinical application of a neuromodulation method. This is in part because of its low invasiveness, whereby INS modulates the activity of the neural tissue mainly through temperature changes. Additionally, INS may provide localized brain stimulation with less tissue damage. The inferior colliculus (IC) is a crucial auditory relay nucleus and a potential target for clinical application of INS to treat auditory diseases and develop artificial hearing devices. Here, using continuous INS with low to high-power density, we demonstrate the laminar modulation of neural activity in the mouse IC in the presence and absence of sound. We investigated stimulation parameters of INS to effectively modulate the neural activity in a facilitatory or inhibitory manner. A mathematical model of INS-driven brain tissue was first simulated, temperature distributions were numerically estimated, and stimulus parameters were selected from the simulation results. Subsequently, INS was administered to the IC of anesthetized mice, and the modulation effect on the neural activity was measured using an electrophysiological approach. We found that the modulatory effect of INS on the spontaneous neural activity was bidirectional between facilitatory and inhibitory effects. The modulatory effect on sound-evoked responses produced only an inhibitory effect to all examined stimulus intensities. Thus, this study provides important physiological evidence on the response properties of IC neurons to INS. Overall, INS can be used for the development of new therapies for neurological disorders and functional support devices for auditory central processing.

Lower Childhood Socioeconomic Status Is Associated with Greater Neural Responses to Ambient Auditory Changes in Adulthood.

Humans' early life experience varies by socioeconomic status (SES), raising the question of how this difference is reflected in the adult brain. An important aspect of brain function is the ability to detect salient ambient changes while focusing on a task. Here, we ask whether subjective social status during childhood is reflected by the way young adults' brain detecting changes in irrelevant information. In two studies (total n = 58), we examine electrical brain responses in the frontocentral region to a series of auditory tones, consisting of standard stimuli (80%) and deviant stimuli (20%) interspersed randomly, while participants were engaged in various visual tasks. Both studies showed stronger automatic change detection indexed by MMN in lower SES individuals, regardless of the unattended sound's feature, attended emotional content, or study type. Moreover, we observed a larger MMN in lower-SES participants, although they did not show differences in brain and behavior responses to the attended task. Lower-SES people also did not involuntarily orient more attention to sound changes (i.e., deviant stimuli), as indexed by the P3a. The study indicates that individuals with lower subjective social status may have an increased ability to automatically detect changes in their environment, which may suggest their adaptation to their childhood environments.

Auditory mismatch negativity in pre-manifest and manifest Huntington's disease.

AIM: The aim of this study was to investigate the characteristics of the electrophysiological brain response elicited in a passive acoustic oddball paradigm, i.e. mismatch negativity (MMN), in patients with Huntington's disease (HD) in the premanifest (pHD) and manifest (mHD) phases. In this regard, we correlated the results of event-related potentials (ERP) with disease characteristics. METHODS: This was an observational cross-sectional MMN study. In addition to the MMN recording of the passive oddball task, all subjects with first-degree inheritance for HD underwent genetic testing for mutant HTT, the Huntington's Disease Rating Scale, the Total Functional Capacity Scale, the Problem Behaviors Assessment short form, and the Mini-Mental State Examination. RESULTS: We found that global field power (GFP) was reduced in the MMN time window in mHD patients compared to pHD and normal controls (NC). In the pHD group, MMN amplitude was only slightly and not significantly increased compared to mHD, while pHD patients showed increased theta coherence between trials compared to mHD. In the entire sample of HD gene carriers, the main MMN traits were not correlated with motor performance, cognitive impairment and functional disability. CONCLUSION: These results suggest an initial and subtle deterioration of pre-attentive mechanisms in the presymptomatic phase of HD, with an increasing phase shift in the MMN time frame. This result could indicate initial functional changes with a possible compensatory effect. SIGNIFICANCE: An initial and slight decrease in MMN associated with increased phase coherence in the corresponding EEG frequencies could indicate an early functional involvement of pre-attentive resources that could precede the clinical expression of HD.

Auditory Encoding of Natural Speech at Subcortical and Cortical Levels Is Not Indicative of Cognitive Decline.

More and more patients worldwide are diagnosed with dementia, which emphasizes the urgent need for early detection markers. In this study, we built on the auditory hypersensitivity theory of a previous study-which postulated that responses to auditory input in the subcortex as well as cortex are enhanced in cognitive decline-and examined auditory encoding of natural continuous speech at both neural levels for its indicative potential for cognitive decline. We recruited study participants aged 60 years and older, who were divided into two groups based on the Montreal Cognitive Assessment, one group with low scores (n = 19, participants with signs of cognitive decline) and a control group (n = 25). Participants completed an audiometric assessment and then we recorded their electroencephalography while they listened to an audiobook and click sounds. We derived temporal response functions and evoked potentials from the data and examined response amplitudes for their potential to predict cognitive decline, controlling for hearing ability and age. Contrary to our expectations, no evidence of auditory hypersensitivity was observed in participants with signs of cognitive decline; response amplitudes were comparable in both cognitive groups. Moreover, the combination of response amplitudes showed no predictive value for cognitive decline. These results challenge the proposed hypothesis and emphasize the need for further research to identify reliable auditory markers for the early detection of cognitive decline.

Intensity-dependent modulation of the early auditory gamma-band response in first-episode schizophrenia and its association with disease symptoms.

BACKGROUND: Gamma-band activity has been the focus of considerable research in schizophrenia. Discrepancies exist regarding the integrity of the early auditory gamma-band response (EAGBR), a stimulus-evoked oscillation, and its relationship to symptoms in early disease. Variability in task design may play a role. This study examined sensitivity of the EAGBR to stimulus intensity and its relation to symptoms and functional impairments in the first-episode schizophrenia spectrum (FESz). METHOD: Magnetoencephalography was recorded from 35 FESz and 40 matched healthy controls (HC) during presentation of 3 tone intensities (75 dB, 80 dB, 85 dB). MRIs were collected to localize auditory cortex activity. Wavelet-transformed single trial epochs and trial averages were used to assess EAGBR intertrial phase coherence (ITPC) and evoked power, respectively. Symptoms were assessed using the Positive and Negative Syndrome Scale. RESULTS: Groups did not differ in overall EAGBR power or ITPC. While HC exhibited EAGBR enhancement to increasing intensity, FESz exhibited reduced power to the 80 dB tone and, relative to HC, increased power to the 75 dB tone. Larger power and ITPC were correlated with more severe negative, thought disorganization, and resistance symptoms. Stronger ITPC was associated with impaired social functioning. DISCUSSION: EAGBR showed no overall deficit at disease onset. Rather, FESz exhibited a differential response across tone intensity relative to HC, emphasizing the importance of stimulus characteristics in EAGBR studies. Associations between larger EAGBR and more severe symptoms suggest aberrant synchronization driving overinclusive perceptual binding that may relate to deficits in executive inhibition of initial sensory activity.

Auditory oddball responses in the human subthalamic nucleus and substantia nigra pars reticulata.

The auditory oddball is a mainstay in research on attention, novelty, and sensory prediction. How this task engages subcortical structures like the subthalamic nucleus and substantia nigra pars reticulata is unclear. We administered an auditory OB task while recording single unit activity (35 units) and local field potentials (57 recordings) from the subthalamic nucleus and substantia nigra pars reticulata of 30 patients with Parkinson's disease undergoing deep brain stimulation surgery. We found tone modulated and oddball modulated units in both regions. Population activity differentiated oddball from standard trials from 200 ms to 1000 ms after the tone in both regions. In the substantia nigra, beta band activity in the local field potential was decreased following oddball tones. The oddball related activity we observe may underlie attention, sensory prediction, or surprise-induced motor suppression.

Phenotypic analysis of multielectrode array EEG biomarkers in developing and adult male Fmr1 KO mice.

Fragile X Syndrome (FXS) is a leading known genetic cause of intellectual disability with symptoms that include increased anxiety and social and sensory processing deficits. Recent electroencephalographic (EEG) studies in humans with FXS have identified neural oscillation deficits that include increased resting state gamma power, increased amplitude of auditory evoked potentials, and reduced phase locking of sound-evoked gamma oscillations. Similar EEG phenotypes are present in mouse models of FXS, but very little is known about the development of such abnormal responses. In the current study, we employed a 30-channel mouse multielectrode array (MEA) system to record and analyze resting and stimulus-evoked EEG signals in male P21 and P91 WT and Fmr1 KO mice. This led to several novel findings. First, P91, but not P21, Fmr1 KO mice have significantly increased resting EEG power in the low- and high-gamma frequency bands. Second, both P21 and P91 Fmr1 KO mice have markedly attenuated inter-trial phase coherence (ITPC) to spectrotemporally dynamic auditory stimuli as well as to 40 Hz and 80 Hz auditory steady-state response (ASSR) stimuli. This suggests abnormal temporal processing from early development that may lead to abnormal speech and language function in FXS. Third, we found hemispheric asymmetry of fast temporal processing in the mouse auditory cortex in WT but not Fmr1 KO mice. Together, these findings define a set of EEG phenotypes in young and adult mice that can serve as translational targets for genetic and pharmacological manipulation in phenotypic rescue studies.

Psychoacoustic and electroencephalographic responses to changes in amplitude modulation depth and frequency in relation to speech recognition in cochlear implantees.

Temporal envelope modulations (TEMs) are one of the most important features that cochlear implant (CI) users rely on to understand speech. Electroencephalographic assessment of TEM encoding could help clinicians to predict speech recognition more objectively, even in patients unable to provide active feedback. The acoustic change complex (ACC) and the auditory steady-state response (ASSR) evoked by low-frequency amplitude-modulated pulse trains can be used to assess TEM encoding with electrical stimulation of individual CI electrodes. In this study, we focused on amplitude modulation detection (AMD) and amplitude modulation frequency discrimination (AMFD) with stimulation of a basal versus an apical electrode. In twelve adult CI users, we (a) assessed behavioral AMFD thresholds and (b) recorded cortical auditory evoked potentials (CAEPs), AMD-ACC, AMFD-ACC, and ASSR in a combined 3-stimulus paradigm. We found that the electrophysiological responses were significantly higher for apical than for basal stimulation. Peak amplitudes of AMFD-ACC were small and (therefore) did not correlate with speech-in-noise recognition. We found significant correlations between speech-in-noise recognition and (a) behavioral AMFD thresholds and (b) AMD-ACC peak amplitudes. AMD and AMFD hold potential to develop a clinically applicable tool for assessing TEM encoding to predict speech recognition in CI users.

Developmental Windows for Effects of Choline and Folate on Excitatory and Inhibitory Neurotransmission During Human Gestation.

Choline and folate are critical nutrients for fetal brain development, but the timing of their influence during gestation has not been previously characterized. At different periods during gestation, choline stimulation of α7-nicotinic receptors facilitates conversion of γ-aminobutyric acid (GABA) receptors from excitatory to inhibitory and recruitment of GluR1-R2 receptors for faster excitatory responses to glutamate. The outcome of the fetal development of inhibition and excitation was assessed in 159 newborns by P50 cerebral auditory-evoked responses. Paired stimuli, S1, S2, were presented 500 msec apart. Higher P50 amplitude in response to S1 (P50S1microV) assesses excitation, and lower P50S2microV assesses inhibition in this paired-stimulus paradigm. Development of inhibition was related solely to maternal choline plasma concentration and folate supplementation at 16 weeks' gestation. Development of excitation was related only to maternal choline at 28 weeks. Higher maternal choline concentrations later in gestation did not compensate for earlier lower concentrations. At 4 years of age, increased behavior problems on the Child Behavior Checklist 1½-5yrs were related to both newborn inhibition and excitation. Incomplete development of inhibition and excitation associated with lower choline and folate during relatively brief periods of gestation thus has enduring effects on child development.

Rate dependent neural responses of interaural-time-difference cues in fine-structure and envelope.

Advancements in cochlear implants (CIs) have led to a significant increase in bilateral CI users, especially among children. Yet, most bilateral CI users do not fully achieve the intended binaural benefit due to potential limitations in signal processing and/or surgical implant positioning. One crucial auditory cue that normal hearing (NH) listeners can benefit from is the interaural time difference (ITD), i.e., the time difference between the arrival of a sound at two ears. The ITD sensitivity is thought to be heavily relying on the effective utilization of temporal fine structure (very rapid oscillations in sound). Unfortunately, most current CIs do not transmit such true fine structure. Nevertheless, bilateral CI users have demonstrated sensitivity to ITD cues delivered through envelope or interaural pulse time differences, i.e., the time gap between the pulses delivered to the two implants. However, their ITD sensitivity is significantly poorer compared to NH individuals, and it further degrades at higher CI stimulation rates, especially when the rate exceeds 300 pulse per second. The overall purpose of this research thread is to improve spatial hearing abilities in bilateral CI users. This study aims to develop electroencephalography (EEG) paradigms that can be used with clinical settings to assess and optimize the delivery of ITD cues, which are crucial for spatial hearing in everyday life. The research objective of this article was to determine the effect of CI stimulation pulse rate on the ITD sensitivity, and to characterize the rate-dependent degradation in ITD perception using EEG measures. To develop protocols for bilateral CI studies, EEG responses were obtained from NH listeners using sinusoidal-amplitude-modulated (SAM) tones and filtered clicks with changes in either fine structure ITD (ITDFS) or envelope ITD (ITDENV). Multiple EEG responses were analyzed, which included the subcortical auditory steady-state responses (ASSRs) and cortical auditory evoked potentials (CAEPs) elicited by stimuli onset, offset, and changes. Results indicated that acoustic change complex (ACC) responses elicited by ITDENV changes were significantly smaller or absent compared to those elicited by ITDFS changes. The ACC morphologies evoked by ITDFS changes were similar to onset and offset CAEPs, although the peak latencies were longest for ACC responses and shortest for offset CAEPs. The high-frequency stimuli clearly elicited subcortical ASSRs, but smaller than those evoked by lower carrier frequency SAM tones. The 40-Hz ASSRs decreased with increasing carrier frequencies. Filtered clicks elicited larger ASSRs compared to high-frequency SAM tones, with the order being 40 > 160 > 80> 320 Hz ASSR for both stimulus types. Wavelet analysis revealed a clear interaction between detectable transient CAEPs and 40-Hz ASSRs in the time-frequency domain for SAM tones with a low carrier frequency.

Basic Properties of Coordinated Neuronal Ensembles in the Auditory Thalamus.

Coordinated neuronal activity has been identified to play an important role in information processing and transmission in the brain. However, current research predominantly focuses on understanding the properties and functions of neuronal coordination in hippocampal and cortical areas, leaving subcortical regions relatively unexplored. In this study, we use single-unit recordings in female Sprague Dawley rats to investigate the properties and functions of groups of neurons exhibiting coordinated activity in the auditory thalamus-the medial geniculate body (MGB). We reliably identify coordinated neuronal ensembles (cNEs), which are groups of neurons that fire synchronously, in the MGB. cNEs are shown not to be the result of false-positive detections or by-products of slow-state oscillations in anesthetized animals. We demonstrate that cNEs in the MGB have enhanced information-encoding properties over individual neurons. Their neuronal composition is stable between spontaneous and evoked activity, suggesting limited stimulus-induced ensemble dynamics. These MGB cNE properties are similar to what is observed in cNEs in the primary auditory cortex (A1), suggesting that ensembles serve as a ubiquitous mechanism for organizing local networks and play a fundamental role in sensory processing within the brain.

Infant mismatch responses to speech-sound changes predict language development in preschoolers at risk for dyslexia.

OBJECTIVE: We investigated how infant mismatch responses (MMRs), which have the potential for providing information on auditory discrimination abilities, could predict subsequent development of pre-reading skills and the risk for familial dyslexia. METHODS: We recorded MMRs to vowel, duration, and frequency deviants in pseudo-words at birth and 28 months in a sample over-represented by infants with dyslexia risk. We examined MMRs' associations with pre-reading skills at 28 months and 4-5 years and compared the results in subgroups with vs. without dyslexia risk. RESULTS: Larger positive MMR (P-MMR) at birth was found to be associated with better serial naming. In addition, increased mismatch negativity (MMN) and late discriminative negativity (LDN), and decreased P-MMR at 28 months overall, were shown to be related to better pre-reading skills. The associations were influenced by dyslexia risk, which was also linked to poor pre-reading skills. CONCLUSIONS: Infant MMRs, providing information about the maturity of the auditory system, are associated with the development of pre-reading skills. Speech-processing deficits may contribute to deficits in language acquisition observed in dyslexia. SIGNIFICANCE: Infant MMRs could work as predictive markers of atypical linguistic development during early childhood. Results may help in planning preventive and rehabilitation interventions in children at risk of learning impairments.