Auditory Gamma Research Articles

Reliable measurement of auditory-driven gamma synchrony with a single EEG electrode: A simultaneous EEG-MEG study

ObjectiveAuditory-driven gamma synchrony (GS) is linked to the function of a specific cortical circuit based on a parvalbumin+ and pyramidal neuron loop. This circuit is impaired in neuropsychiatric conditions (i.e. schizophrenia, Alzheimer's disease, stroke etc.) and its relevance in clinical practice is increasingly being recognized. Auditory stimulation at a typical gamma frequency of 40 Hz can be applied as a ‘stress test’ of excitation/inhibition (E/I) of the entire cerebral cortex, to drive GS and record it with magnetoencephalography (MEG) or high-density electroencephalography (EEG). However, these two techniques are costly and not widely available. Therefore, we assessed whether a single EEG electrode is sufficient to provide an accurate estimate of the auditory-driven GS level of the entire cortical surface while expecting the highest correspondence in the auditory and somatosensory cortices. MethodsWe measured simultaneous EEG-MEG in 29 healthy subjects, utilizing 3 EEG electrodes (C4, F4, O2) and a full MEG setup. Recordings were performed during binaural exposure to auditory gamma stimulation and during silence. We compared GS measurement of each of the three EEG electrodes separately against full MEG mapping. Time-resolved phase locking value (PLVt) was computed between EEG signals and cortex reconstructed MEG signals. ResultsDuring auditory stimulation, but not at rest, EEG captures a significant amount of GS, especially from both auditory cortices and motor-premotor regions. This was especially true for frontal (C4) and central electrodes (F4). Discussion and ConclusionsWhile hd-EEG and MEG are necessary for accurate spatial mapping of GS at rest and during auditory stimulation, a single EEG channel is sufficient to detect the global level of GS. These results have great translational potential for mapping GS in standard clinical settings.

A Randomized, Double‐blind, Sham‐controlled, Adaptive‐Design Pivotal Trial of Sensory Stimulation in Subjects with Alzheimer’s Disease

AbstractBackgroundIn three prospective clinical trials (Overture: NCT03556280, Etude: NCT03661034, Flicker: NCT03543878) non‐invasive, visual and auditory gamma (40 Hz) sensory stimulation diminished Alzheimer’s disease (AD) symptoms, including a reduction in decline in cognitive and functional symptoms. These trials initiated the design of the Cognito Therapeutics sponsored Hope pivotal trial which examines the safety and efficacy of Cognito Therapeutics’ Sensory Stimulation System.MethodThe US‐based multicenter Hope trial will randomize (1:1) approximately 500 subjects aged 50 and older diagnosed with mild to moderate AD (MMSE 15‐26) and will stratify them to active and sham in a blinded manner across MMSE score ranges: 15‐20 and 21‐26. Subjects in both study arms will self‐administer therapy via the Sensory Stimulation System for 60 minutes daily for 12 months. An interim analysis will employ the promising zone methodology, allowing the sample size to be adjusted if the effect is trending toward success, but additional subjects are needed to maintain greater than 80% power.ResultThe primary outcome measure will be the Alzheimer’s Disease Cooperative Study – Activities of Daily Living (ADCS‐ADL) test. Changes in function and cognition will be evaluated using a combined statistical test for ADCS‐ADL and the Mini Mental State Exam (MMSE). The key secondary outcome is change in cognition using the MMSE. Other clinical efficacy assessments include instrumental activities of daily living (IADL), Zarit Burden Index (ZBI), the Clinical Dementia Rating Scale (CDR) and The Neuropsychiatric Inventory anxiety subscale (NPI – Anxiety). Key biomarker assessments include whole brain, white matter, and hippocampal volume and occipital cortical thickness. Sleep fragmentation will be assessed in a subgroup of subjects using actigraphy. Exploratory measures will include additional brain structural change, plasma biomarkers, EEG assessed coherence, and at‐home tablet‐based tasks. Safety will be evaluated via routine clinical laboratory assessments, review of adverse events, concurrent medication use, physical and neurological exams, vital signs, MRI, and a suicidality scale.ConclusionThe Hope pivotal trial is designed to demonstrate the efficacy and safety of daily in‐home gamma sensory stimulation in AD patients to support a regulatory filing with the FDA.

Auditory Gamma Entrainment Leads to Theta Oscillations Asymmetric behavior in both Alzheimer’s Disease and Healthy Participants

AbstractBackgroundBrain oscillations known for handling various information across brain. The gamma rhythms observed in high‐level cognitive process (Fries et al., Trends in neurosciences 2018) and theta cycle observed to process sensory information and interact with gamma oscillations (Amemiya et al., Cell Reports 2018). Disruption in synchronization of gamma oscillations have been observed in Alzheimer’s disease patients (Uhlhaas et al., Neuron 2006). Gamma stimulation had been shown to reduce the mentioned dysfunction and reported to have therapeutic results (Martorell et al., Cell 2019; Suk et al. Alzheimer’s and Dementia 2020). This study examines the effect of gamma band activity induced by auditory chirp stimulation as a driver for other frequency sources. The chirp signal is designed to entrain 40Hz which had been shown to have therapeutics effects.Method33 participants were included in this study including 17 mild AD, 6 MCI and 10 healthy elderlies. A session consists of interleaved periods of forty second stimulation and twenty second silence. The stimulation is a 5kHz tone modulated by a 40Hz chirp at 0.1 duty cycle. EEG data were collected by a 10/20 system. Relative magnitude of the 40Hz oscillations with respect to neighbors’ magnitude during the stimulation was measured as an indicator of the entrained gamma oscillations. Total participants are categorized into entrained and not‐entrained group based on the indicator. Phase locking Value (PLV) is then calculated in theta frequency band.Result40Hz entrainment have been observed in healthy participants and also some Alzheimer’s disease patients. Based on the power spectral density (PSD) at forty hertz 23 entrained and 10 not‐entrained participants are separated and PLV analysis have been calculated for the two groups. Theta oscillatory asymmetry have been observed in posterior temporal cortex during auditory stimulation.ConclusionEntraining gamma oscillations using auditory stimulation results in cross frequency variation. Phase‐amplitude or phase‐phase coupling measures the simultaneous correlation between specific oscillations. This study suggests that despite the concurrent association of theta‐gamma frequencies, some brain network changes occur in response to gamma oscillation which should be more discussed in related researches.

Combined multi-session transcranial alternating current stimulation (tACS) and language skills training improves individual gamma band activity and literacy skills in developmental dyslexia

Developmental dyslexia is characterized by the pathologically diminished ability to acquire reading and spelling skills. Accurate processing of acoustic information at the phonemic scale is crucial for successful sound-to-letter-mapping which, in turn, is elemental in reading and spelling. Altered activation patterns in the auditory cortex are thought to provide the neurophysiological basis for the inaccurate phonemic perception. Recently, transcranial electrical stimulation has been shown to be an effective method to ameliorate cortical activation patterns in the auditory cortex. In a sample of children and adolescents with dyslexia, we investigated the effect of multi-session transcranial alternating current stimulation delivered concurrently with a phonological training and in combination with a behavioral literacy skills training. Over a 5-week period the participants received 10 training sessions while gamma-tACS was administered over bilateral auditory cortex. We found that gamma-tACS shifted the peak frequency of auditory gamma oscillations reflecting a more fine-grained processing of time-critical acoustic information. This amelioration was accompanied by increased phonemic processing skills. Moreover, individuals who received gamma-tACS showed significant improvements in their spelling skills four months after the intervention. Our results demonstrate that multi-session gamma-tACS enhances the effects of a behavioral intervention and induces long-term improvement on literacy skills in dyslexia.

Neuromagnetic 40 Hz Auditory Steady-State Response in the left auditory cortex is related to language comprehension in children with Autism Spectrum Disorder

Language impairment is comorbid in most children with Autism Spectrum Disorder (ASD), but its neural mechanisms are still poorly understood. Some studies hypothesize that the atypical low-level sensory perception in the auditory cortex accounts for the abnormal language development in these children. One of the potential non-invasive measures of such low-level perception can be the cortical gamma-band oscillations registered with magnetoencephalography (MEG), and 40 Hz Auditory Steady-State Response (40 Hz ASSR) is a reliable paradigm for eliciting auditory gamma response. Although there is research in children with and without ASD using 40 Hz ASSR, nothing is known about the relationship between this auditory response in children with ASD and their language abilities measured directly in formal assessment.In the present study, we used MEG and individual brain models to investigate 40 Hz ASSR in primary-school-aged children with and without ASD. It was also used to assess how the strength of the auditory response is related to language abilities of children with ASD, their non-verbal IQ, and social functioning. A total of 40 children were included in the study.The results demonstrated that 40 Hz ASSR was reduced in the right auditory cortex in children with ASD when comparing them to typically developing controls. Importantly, our study provides the first evidence of the association between 40 Hz ASSR in the language-dominant left auditory cortex and language comprehension in children with ASD. This link was domain-specific because the other brain-behavior correlations were non-significant.

Synchronized Auditory Gamma Response to Frontal Transcranial Direct Current Stimulation (tDCS) and its Inter-Individual Variation in Healthy Humans.

In schizophrenia, a disorder associated with N-methyl-D-aspartate receptor (NMDAR) hypofunction, auditory cortical plasticity deficits have been indexed by the synchronized electroencephalographic (EEG) auditory steady-state gamma-band (40-Hz) response (ASSR) and the early auditory evoked gamma-band response (aeGBR), both considered to be target engagement biomarkers for NMDAR function, and potentially amenable to treatment by NMDAR modulators. As transcranial direct current stimulation (tDCS) is likely dependent on NMDAR neurotransmission, this preliminary study, conducted in 30 healthy volunteers, assessed the off-line effects of prefrontal anodal tDCS and sham (placebo) treatment on 40-Hz ASSR and aeGBR. Anodal tDCS failed to alter aeGBR but increased both 40-Hz ASSR power, as measured by event-related spectral perturbations (ERSP), and phase locking, as measured by inter-trial phase consistency (ITPC). Inter-individual differences in tDCS-induced increases in ERSP were negatively related to baseline ERSPs. These findings provide tentative support for further study of tDCS as a potential NMDAR neuromodulatory intervention for synchronized auditory gamma response deficits.

Safety, feasibility, and adherence of a daily, in‐home gamma sensory stimulation therapy with the Cognito Sensory Stimulation System in Alzheimer’s subjects

AbstractBackgroundNon‐invasive, visual and auditory gamma (40 Hz) sensory stimulation demonstrates clearance of β‐amyloid plaques and tau tangles, and cognition improvement in preclinical AD models (Iaccarino, 2016, Martorell, 2019). A home‐use gamma sensory stimulation device (Cognito Therapeutics, Inc., Cambridge, MA) was developed to evoke gamma oscillations in humans. The long‐term safety and feasibility of this approach has not been previously evaluated in AD subjects.MethodOverture is a prospective 6‐month treatment study in mild‐to‐moderate AD of the Cognito device. Subjects were randomized 2:1, treatment:sham. All subjects underwent in‐clinic EEG to confirm gamma entrainment and calibrate the device. Therapy was self‐administered daily during 1‐hour sessions at home with adherence logged by device. Safety assessments included adverse event (AE) monitoring, MRIs, and physical exams. Subjects and caregivers participated in multiple in‐depth interviews to assess the feasibility of this novel therapy. Subjects had the option to enter a 12‐month extension.ResultIn total, 20,562 treatment sessions have been completed by 74 subjects in the Main and Extension period. Overall rates of AEs during the Main and Extension study periods were roughly equivalent between groups (Active: 2.5/subject, Sham: 2.9/subject). There were no unexpected serious treatment emergent adverse events. Review of MR imaging data by neuroradiology demonstrated stable findings from baseline to follow‐up and absence of ARIA in all subjects. Adherence data showed that Sham participants had a final mean adherence of 95.9%±9.0%, while treatment participants had a final mean adherence of 90.2%±13.3%, and the difference was not significant in an independent‐samples, two‐tailed t‐test (p=0.14). Participants easily adopted and adhered to daily self‐administered therapy, with 60% of enrolled participants choosing to continue into the extension.ConclusionThe interim results of the study demonstrate that long‐term, daily, self‐administered, home‐use of gamma sensory stimulation is both safe and well tolerated in mild‐to‐moderate AD subjects.

Global and Parallel Cortical Processing Based on Auditory Gamma Oscillatory Responses in Humans.

Gamma oscillations are physiological phenomena that reflect perception and cognition, and involve parvalbumin-positive γ-aminobutyric acid-ergic interneuron function. The auditory steady-state response (ASSR) is the most robust index for gamma oscillations, and it is impaired in patients with neuropsychiatric disorders such as schizophrenia and autism. Although ASSR reduction is known to vary in terms of frequency and time, the neural mechanisms are poorly understood. We obtained high-density electrocorticography recordings from a wide area of the cortex in 8 patients with refractory epilepsy. In an ASSR paradigm, click sounds were presented at frequencies of 20, 30, 40, 60, 80, 120, and 160 Hz. We performed time-frequency analyses and analyzed intertrial coherence, event-related spectral perturbation, and high-gamma oscillations. We demonstrate that the ASSR is globally distributed among the temporal, parietal, and frontal cortices. The ASSR was composed of time-dependent neural subcircuits differing in frequency tuning. Importantly, the frequency tuning characteristics of the late-latency ASSR varied between the temporal/frontal and parietal cortex, suggestive of differentiation along parallel auditory pathways. This large-scale survey of the cortical ASSR could serve as a foundation for future studies of the ASSR in patients with neuropsychiatric disorders.

Dysfunctional auditory gamma oscillations in developmental dyslexia: A potential target for a tACS-based intervention.

Interventions in developmental dyslexia typically consist of orthography-based reading and writing trainings. However, their efficacy is limited and, consequently, the symptoms persist into adulthood. Critical for this lack of efficacy is the still ongoing debate about the core deficit in dyslexia and its underlying neurobiological causes. There is ample evidence on phonological as well as auditory temporal processing deficits in dyslexia and, on the other hand, cortical gamma oscillations in the auditory cortex as functionally relevant for the extraction of linguistically meaningful information units from the acoustic signal. The present work aims to shed more light on the link between auditory gamma oscillations, phonological awareness, and literacy skills in dyslexia. By mean of EEG, individual gamma frequencies were assessed in a group of children and adolescents diagnosed with dyslexia as well as in an age-matched control group with typical literacy skills. Furthermore, phonological awareness was assessed in both groups, while in dyslexic participants also reading and writing performance was measured. We found significantly lower gamma peak frequencies as well as lower phonological awareness scores in dyslexic participants compared to age-matched controls. Additionally, results showed a positive correlation between the individual gamma frequency and phonological awareness. Our data suggest a hierarchical structure of neural gamma oscillations, phonological awareness, and literacy skills. Thereby, the results emphasize altered gamma oscillation not only as a core deficit in dyslexia but also as a potential target for future causal interventions. We discuss these findings considering non-invasive brain stimulation techniques and suggest transcranial alternating current stimulation as a promising approach to normalize dysfunctional oscillations in dyslexia.

Modulation of auditory gamma-band responses using transcranial electrical stimulation.

Auditory gamma-band (>30 Hz) activity is a biomarker of cortical excitation/inhibition (E/I) balance in autism, schizophrenia, and bipolar disorder. We provide a comprehensive account of the effects of transcranial alternating current stimulation (tACS) and transcranial direct current stimulation (tDCS) on gamma responses. Forty-five healthy young adults listened to 40-Hz auditory click trains while electroencephalography (EEG) data were collected to measure stimulus-related gamma activity immediately before and after 10 min of 1 mA tACS (40 Hz), tDCS, or sham stimulation to left auditory cortex. tACS, but not tDCS, increased gamma power and phase locking to the auditory stimulus. However, both tACS and tDCS strengthened the gamma phase connectome, and effects persisted beyond the stimulus. Finally, tDCS strengthened the coupling of gamma activity to alpha oscillations after termination of the stimulus. No effects were observed in prestimulus gamma power, the gamma amplitude connectome, or any band-limited alpha measure. Whereas both stimulation techniques synchronize gamma responses between regions, tACS also tunes the magnitude and timing of gamma responses to the stimulus. Results reveal dissociable neurophysiological changes following tACS and tDCS and demonstrate that clinical biomarkers can be altered with noninvasive neurostimulation, especially frequency-tuned tACS.NEW & NOTEWORTHY Gamma frequency-tuned transcranial alternating current stimulation (tACS) adjusts the magnitude and timing of auditory gamma responses, as compared with both sham stimulation and transcranial direct current stimulation (tDCS). However, both tACS and tDCS strengthen the gamma phase connectome, which is disrupted in numerous neurological and psychiatric disorders. These findings reveal dissociable neurophysiological changes following two noninvasive neurostimulation techniques commonly applied in clinical and research settings.

Global and Parallel Cortical Processing of Auditory Gamma Oscillatory Responses in Humans

Gamma oscillation is a physiological phenomenon that reflects higher cognitive function and parvalbumin-positive GABAergic interneuron function in animals. Gamma-band auditory steady-state response (ASSR) is the most robust index for gamma oscillation, which is impaired in patients with neuropsychiatric disorders. Although ASSR reduction is known to be selective for frequency and time, the neural basis of this phenomenon is poorly understood. We directly showed in the current study that ASSR is globally distributed among the temporal, parietal, and frontal cortices using electrocorticography (ECoG) recording from a wide range of the cortex in patients with refractory epilepsy. ASSR was composed of multiple neural circuits depending on frequency and latency. Importantly, late-latency ASSR was topographically organized along the dorsal and ventral auditory pathways according to frequency tuning characteristics. These results provide a neural basis of the frequency-time dependence of ASSR reduction in patients with neuropsychiatric disorders.

Auditory gamma oscillations predict global symptomatic outcome in the early stages of psychosis: A longitudinal investigation

ObjectivesThe gamma-band auditory steady-state response (ASSR) is thought to reflect the function of parvalbumin-positive γ-aminobutyric acid (GABA)-ergic interneurons and may be a candidate biomarker in early psychosis. Although previous cross-sectional studies have shown that gamma-band ASSR is reduced in early psychosis, whether reduced gamma-band ASSR could be a predictor of the long-term prognosis remains unknown. MethodsIn this longitudinal study, we investigated the association between gamma-band ASSR reduction and future global symptomatic or functional outcome in early psychosis. We measured 40-Hz ASSR in 34 patients with recent-onset schizophrenia (ROSZ), 28 ultra-high risk (UHR) individuals, and 30 healthy controls (HCs) at baseline. After 1–2 years, we evaluated the global assessment of functioning (GAF) in the ROSZ (N = 20) and UHR (N = 20) groups. ResultsThe 40-Hz ASSR was significantly reduced in the ROSZ and UHR groups. The attenuated 40-Hz ASSR was correlated with the future global symptomatic outcome in the ROSZ, but not in the UHR groups. ConclusionsA reduction in the gamma-band ASSR after the onset of psychosis may predict symptomatic outcomes in early psychosis. SignificanceGamma-band ASSR may be a potentially useful biomarker of the long-term prognosis in patients with recent-onset schizophrenia.

Multifactorial Modeling of Impairment of Evoked Gamma Range Oscillations in Schizophrenia.

Despite a significant increase in efforts to identify biomarkers and endophenotypic measures of psychiatric illnesses, only a very limited amount of computational models of these markers and measures has been implemented so far. Moreover, existing computational models dealing with biomarkers typically only examine one possible mechanism in isolation, disregarding the possibility that other combinations of model parameters might produce the same network behavior (what has been termed “multifactoriality”). In this study we describe a step toward a computational instantiation of an endophenotypic finding for schizophrenia, namely the impairment of evoked auditory gamma and beta oscillations in schizophrenia. We explore the multifactorial nature of this impairment using an established model of primary auditory cortex, by performing an extensive search of the parameter space. We find that single network parameters contain only little information about whether the network will show impaired gamma entrainment and that different regions in the parameter space yield similar network level oscillation abnormalities. These regions in the parameter space, however, show strong differences in the underlying network dynamics. To sum up, we present a first step toward an in silico instantiation of an important biomarker of schizophrenia, which has great potential for the identification and study of disease mechanisms and for understanding of existing treatments and development of novel ones.

Thalamocortical Dysrhythmia: A Theoretical Update in Tinnitus

Tinnitus is the perception of a sound in the absence of a corresponding external sound source. Pathophysiologically it has been attributed to bottom-up deafferentation and/or top-down noise-cancelling deficit. Both mechanisms are proposed to alter auditory ­thalamocortical signal transmission, resulting in thalamocortical dysrhythmia (TCD). In deafferentation, TCD is characterized by a slowing down of resting state alpha to theta activity associated with an increase in surrounding gamma activity, resulting in persisting cross-frequency coupling between theta and gamma activity. Theta burst-firing increases network synchrony and recruitment, a mechanism, which might enable long-range synchrony, which in turn could represent a means for finding the missing thalamocortical information and for gaining access to consciousness. Theta oscillations could function as a carrier wave to integrate the tinnitus-related focal auditory gamma activity in a consciousness enabling network, as envisioned by the global workspace model. This model suggests that focal activity in the brain does not reach consciousness, except if the focal activity becomes functionally coupled to a consciousness enabling network, aka the global workspace. In limited deafferentation, the missing information can be retrieved from the auditory cortical neighborhood, decreasing surround inhibition, resulting in TCD. When the deafferentation is too wide in bandwidth, it is hypothesized that the missing information is retrieved from theta-mediated parahippocampal auditory memory. This suggests that based on the amount of deafferentation TCD might change to parahippocampocortical persisting and thus pathological theta–gamma rhythm. From a Bayesian point of view, in which the brain is conceived as a prediction machine that updates its memory-based predictions through sensory updating, tinnitus is the result of a prediction error between the predicted and sensed auditory input. The decrease in sensory updating is reflected by decreased alpha activity and the prediction error results in theta–gamma and beta–gamma coupling. Thus, TCD can be considered as an adaptive mechanism to retrieve missing auditory input in tinnitus.

Differential Alterations of Auditory Gamma Oscillatory Responses Between Pre-Onset High-Risk Individuals and First-Episode Schizophrenia.

Alterations in gamma-band auditory steady-state response (ASSR) are the most robust finding of abnormal neural oscillations in patients with first-episode (FES) and chronic schizophrenia. Gamma-band ASSRs may indicate GABAergic interneuron dysfunction. Nevertheless, it is unknown whether abnormal gamma-band ASSRs are present before the onset of psychosis. Subjects were 15 ultra-high-risk (UHR) individuals, 13 FES patients, and 21 healthy control (HC) subjects. We performed electroencephalogram recordings and measured ASSRs in each group as they were presented with click trains at 20, 30, and 40 Hz. We then conducted time-frequency analyses and calculated intertrial phase coherence and event-related spectral perturbation. The time course of gamma-band ASSRs showed significantly different features among groups. Compared with the HC group, the UHR group was characterized by intact early-latency (0-100 ms) and reduced late-latency (300-500 ms) ASSRs. In contrast, both early- and late-latency ASSRs were significantly reduced in the FES group. Gamma-band ASSRs were correlated with clinical symptoms and attentional functioning in FES (|rs| > 0.70). These results suggest differential alterations of gamma-band ASSRs between UHR and FES groups. The late-latency ASSR alteration may represent a biomarker for early detection of psychosis, while the early-latency ASSR abnormality may develop through the onset of psychosis.

Chapter 9 - Early auditory gamma band response abnormalities in first hospitalized schizophrenia

Abnormalities in coherent cortical circuit functioning, reflected in gamma band activity (to approximately 40 Hz), may be a core deficit in schizophrenia. The early auditory gamma band response (EAGBR) is a neurophysiologically simple probe of circuit functioning in primary auditory cortex. We examined the EAGBR in first hospitalized schizophrenia to assess whether it was reduced at first hospitalization. Wavelet evoked power and intertrial phase locking of the EAGBR at Fz to standard tones during an oddball target detection task were examined in 28 first hospitalized schizophrenia patients (10 female) and 44 control subjects (17 female). At first hospitalization EAGBR trial-to-trial phase locking and evoked power were significantly reduced in patients. Although reduced overall in patients, greater total symptoms were significantly associated with greater gamma phase locking and power. Additionally, greater EAGBR power was marginally associated with greater positive factor scores, hallucinations, and thinking disturbance. Abnormalities of gamma band functioning in local auditory sensory circuits are present in schizophrenia at first hospitalization further evidence that basic sensory processes are impaired in schizophrenia. It remains to be determined whether the EAGBR becomes permanently impaired with disease progression, and if its reduction is specific to schizophrenia.

Mapping Symbols to Sounds: Electrophysiological Correlates of the Impaired Reading Process in Dyslexia

Dyslexic and control first-grade school children were compared in a Symbol-to-Sound matching test based on a non-linguistic audiovisual training which is known to have a remediating effect on dyslexia. Visual symbol patterns had to be matched with predicted sound patterns. Sounds incongruent with the corresponding visual symbol (thus not matching the prediction) elicited the N2b and P3a event-related potential (ERP) components relative to congruent sounds in control children. Their ERPs resembled the ERP effects previously reported for healthy adults with this paradigm. In dyslexic children, N2b onset latency was delayed and its amplitude significantly reduced over left hemisphere whereas P3a was absent. Moreover, N2b amplitudes significantly correlated with the reading skills. ERPs to sound changes in a control condition were unaffected. In addition, correctly predicted sounds, that is, sounds that are congruent with the visual symbol, elicited an early induced auditory gamma band response (GBR) reflecting synchronization of brain activity in normal-reading children as previously observed in healthy adults. However, dyslexic children showed no GBR. This indicates that visual symbolic and auditory sensory information are not integrated into a unitary audiovisual object representation in them. Finally, incongruent sounds were followed by a later desynchronization of brain activity in the gamma band in both groups. This desynchronization was significantly larger in dyslexic children. Although both groups accomplished the task successfully remarkable group differences in brain responses suggest that normal-reading children and dyslexic children recruit (partly) different brain mechanisms when solving the task. We propose that abnormal ERPs and GBRs in dyslexic readers indicate a deficit resulting in a widespread impairment in processing and integrating auditory and visual information and contributing to the reading impairment in dyslexia.

Auditory hallucinations and gamma band evoked power in response to auditory stimulation and speech in schizophrenia

Auditory hallucinations and gamma band evoked power in response to auditory stimulation and speech in schizophrenia

Can pure noise have a meaning? How auditory gamma power is modulated by the familiarity of songs

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Auditory gamma activity after stimulant administration in patients with ADHD

Event Abstract Back to Event Auditory gamma activity after stimulant administration in patients with ADHD Tony W. Wilson1*, Matthew L. White2, Nichole L. Knott1 and Martin W. Wetzel3 1 University of Nebraska Medical Center, Department of Neurological Sciences, United States 2 University of Nebraska Medical Center, Department of Radiology, United States 3 University of Nebraska Medical Center, Department of Psychiatry, United States Attention-deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder affecting approximately 8% of children and persisting in 4% of adults. Symptoms include inattention, impulsivity, and hyperactivity. Regardless of age stimulant medications are the most effective treatment for ADHD, although their mechanism of action is poorly understood. In the current study, we examined auditory gamma-frequency responses before and ~75 minutes after oral amphetamine administration. Gamma activity has been implicated in the temporal binding of stimulus properties across distinct cortical areas, as well as other forms of complex information processing. Adult outpatients with ADHD listened to ~150 trials of binaurally presented click trains (inter-click-interval=25 ms; duration=500 ms; ISI=1.2 s) per session as whole-cortex magnetoencephalography (MEG) data were acquired. These data were transformed into a standard device-centered head position, corrected for head movements that occurred during the recording, coregistered to the participant’s MRI, inspected for artifacts, time-domain averaged, and bandpass filtered around the 40 Hz steady-state response. Bilateral neural generators of the peak 40 Hz response were localized and this two-source model was used to calculate an inverse spatial filter for deriving source waveforms. Our results indicated that amphetamine ingestion is associated with significantly increased gamma-band activity in the auditory cortices. These results may indicate that adults with ADHD have reduced high-frequency activity at baseline (suggesting impaired cortical inhibitory function), and that amphetamine medications act to normalize such gamma activity (and thereby GABA function) across the cortex. Work in our laboratory is currently investigating this and other competing hypotheses to characterize the implications of reduced gamma activity in patients with ADHD and the corresponding clinical benefits of stimulant therapy. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MEG: Clinical applications Citation: Wilson TW, White ML, Knott NL and Wetzel MW (2010). Auditory gamma activity after stimulant administration in patients with ADHD. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00296 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Apr 2010; Published Online: 05 Apr 2010. * Correspondence: Tony W Wilson, University of Nebraska Medical Center, Department of Neurological Sciences, Omaha, United States, tony.w.wilson@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Tony W Wilson Matthew L White Nichole L Knott Martin W Wetzel Google Tony W Wilson Matthew L White Nichole L Knott Martin W Wetzel Google Scholar Tony W Wilson Matthew L White Nichole L Knott Martin W Wetzel PubMed Tony W Wilson Matthew L White Nichole L Knott Martin W Wetzel Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.