Auditory N1 Research Articles

Predictors of chronicity in alcohol use disorder: an evoked response potential study

Introduction Evoked response potentials (ERP) can reliably map key neurocognitive processes which are putatively responsible for chronic alcohol use disorder (AUD). Aim of the present study was to study P300 auditory odd ball and N400 visual semantic incongruity paradigm mapping executive functions rubric as a potential biomarker predicting chronicity in AUDs. Methodology: 60 right handed 18 to 54 years age subjects were divided into chronic “CAD” and non chronic alcohol dependence “NAD” in addition to healthy control “HC” (N = 30). Subjects were assessed by Addiction Severity Index (ASI), P300 auditory odd ball paradigm in midline region and visual N400 semantic incongruity task in centro-parietal region in a cross sectional design. Results: All the three groups differed significantly for P300 and N400 amplitude in all the leads with maximum attenuation seen in CAD. On discriminant function analysis (DFA), P300 Pz and N 400 C2 amplitude values could accurately classified 78.3% subjects. Composite sensitivity and specificity of the two predictor variables differentiating CAD subjects from NAD were 79.31 and 77.41%. receiver operating characteristic curve generated an area under the curve of .758 and .847 i.e., “fair to good” ability to predict CAD from NAD. Conclusion: We conclude that specific ERP paradigm can be used as a state marker to map the cognitive deficits and as a biomarker to detect chronic AUDs.

Reduced Left Primary Auditory Cortex Dynamic Range in the First Episode Schizophrenia-Spectrum? A Preliminary Report

Individuals with long-term schizophrenia fail to increase auditory N100 with increasing stimulus intensity. It is unknown if first psychotic episode schizophrenia spectrum individuals (FESz) display impaired “loudness-dependence” (a measure of auditory cortex dynamic range). We present a preliminary analysis of M100 (N100’s magnetic counterpart) primary auditory cortex (PAC) source activity evoked at different stimulus intensities in FESz compared to matched healthy controls (HC).

Varying effect of noise on sound onset and acoustic change evoked auditory cortical N1 responses evoked by a vowel-vowel stimulus

IntroductionAccording to previous studies noise causes prolonged latencies and decreased amplitudes in acoustic change evoked cortical responses. Particularly for a consonant-vowel stimulus, speech shaped noise leads to more pronounced changes on onset evoked response than acoustic change evoked response. Reasoning that this may be related to the spectral characteristics of the stimuli and the noise, in the current study a vowel-vowel stimulus (/ui/) was presented in white noise during cortical response recordings. The hypothesis is that the effect of noise will be higher on acoustic change N1 compared to onset N1 due to the masking effects on formant transitions. MethodsOnset and acoustic change evoked auditory cortical N1-P2 responses were obtained from 21 young adults with normal hearing while presenting 1000 ms /ui/ stimuli in quiet and in white noise at +10 dB and 0 dB signal-to-noise ratio (SNR). ResultsIn the quiet and +10 dB SNR conditions, the N1-P2 responses to both onset and change were present. In the +10 dB SNR condition acoustic change N1-P2 peak-to-peak amplitudes were reduced and N1 latencies were prolonged compared to the quiet condition. Whereas there was not a significant change in onset N1 latencies and N1-P2 peak-to-peak amplitudes in the +10 dB SNR condition. In the 0 dB SNR condition change responses were not observed but onset N1-P2 peak-to-peak amplitudes were significantly lower, and onset N1 latencies were significantly higher compared to the quiet and the 10 dB SNR conditions. Onset and change responses were also compared with each other in each condition. N1 latencies and N1-P2 peak to peak amplitudes of onset and acoustic change were not significantly different in the quiet condition. Whereas at 10 dB SNR, acoustic change N1 latencies were higher and N1-P2 amplitudes were lower than onset latencies and amplitudes. To summarize, presentation of white noise at 10 dB SNR resulted in the reduction of acoustic change evoked N1-P2 peak-to-peak amplitudes and the prolongation of N1 latencies compared to quiet. Same effect on onsets were only observed at 0 dB SNR, where acoustic change N1 was not observed. In the quiet condition, latencies and amplitudes of onsets and changes were not different. Whereas at 10 dB SNR, acoustic change N1 latencies were higher, amplitudes were lower than onset N1. Discussion/conclusionsThe effect of noise was found to be higher on acoustic change evoked N1 response compared to onset N1. This may be related to the spectral characteristics of the utilized noise and the stimuli, possible differences in acoustic features of sound onsets and acoustic changes, or to the possible differences in the mechanisms for detecting acoustic changes and sound onsets. In order to investigate the possible reasons for more pronounced effect of noise on acoustic changes, future work with different vowel-vowel transitions in different noise types is suggested.

The role of spatial selective attention in the processing of affective prosodies in congenitally blind adults: An ERP study

The question whether spatial selective attention is necessary in order to process vocal affective prosody has been controversially discussed in sighted individuals: whereas some studies argue that attention is required in order to process emotions, other studies conclude that vocal prosody can be processed even outside the focus of spatial selective attention. Here, we asked whether spatial selective attention is necessary for the processing of affective prosodies after visual deprivation from birth. For this purpose, pseudowords spoken in happy, neutral, fearful or threatening prosodies were presented at the left or right loudspeaker. Congenitally blind individuals (N = 8) and sighted controls (N = 13) had to attend to one of the loudspeakers and detect rare pseudowords presented at the attended loudspeaker during EEG recording. Emotional prosody of the syllables was task-irrelevant. Blind individuals outperformed sighted controls by being more efficient in detecting deviant syllables at the attended loudspeaker. A higher auditory N1 amplitude was observed in blind individuals compared to sighted controls. Additionally, sighted controls showed enhanced attention-related ERP amplitudes in response to fearful and threatening voices during the time range of the N1. By contrast, blind individuals revealed enhanced ERP amplitudes in attended relative to unattended locations irrespective of the affective valence in all time windows (110–350 ms). These effects were mainly observed at posterior electrodes. The results provide evidence for “emotion-general“ auditory spatial selective attention effects in congenitally blind individuals and suggest a potential reorganization of the voice processing brain system following visual deprivation from birth.

Seeing the Intensity of a Sound-producing Event Modulates the Amplitude of the Initial Auditory Evoked Response.

An auditory event is often accompanied by characteristic visual information. For example, the sound level produced by a vigorous handclap may be related to the speed of hands as they move toward collision. Here, we tested the hypothesis that visual information about the intensity of auditory signals are capable of altering the subsequent neurophysiological response to auditory stimulation. To do this, we used EEG to measure the response of the human brain (n = 28) to the audiovisual delivery of handclaps. Depictions of a weak handclap were accompanied by auditory handclaps at low (65 dB) and intermediate (72.5 dB) sound levels, whereas depictions of a vigorous handclap were accompanied by auditory handclaps at intermediate (72.5 dB) and high (80 dB) sound levels. The dependent variable was the amplitude of the initial negative component (N1) of the auditory evoked potential. We find that identical clap sounds (intermediate level; 72.5 dB) elicited significantly lower N1 amplitudes when paired with a video of a weak clap, compared with when paired with a video of a vigorous clap. These results demonstrate that intensity predictions can affect the neural responses to auditory stimulation at very early stages (<100 msec) in sensory processing. Furthermore, the established sound-level dependence of auditory N1 amplitude suggests that such effects may serve the functional role of altering auditory responses in accordance with visual inferences. Thus, this study provides evidence that the neurally evoked response to an auditory event results from a combination of a person's beliefs with incoming auditory input.

Multimodal Recognition of Emotions in Music and Facial Expressions.

The aim of the study was to investigate the neural processing of congruent vs. incongruent affective audiovisual information (facial expressions and music) by means of ERPs (Event Related Potentials) recordings. Stimuli were 200 infant faces displaying Happiness, Relaxation, Sadness, Distress and 32 piano musical pieces conveying the same emotional states (as specifically assessed). Music and faces were presented simultaneously, and paired so that in half cases they were emotionally congruent or incongruent. Twenty subjects were told to pay attention and respond to infrequent targets (adult neutral faces) while their EEG was recorded from 128 channels. The face-related N170 (160–180 ms) component was the earliest response affected by the emotional content of faces (particularly by distress), while visual P300 (250–450 ms) and auditory N400 (350–550 ms) responses were specifically modulated by the emotional content of both facial expressions and musical pieces. Face/music emotional incongruence elicited a wide N400 negativity indicating the detection of a mismatch in the expressed emotion. A swLORETA inverse solution applied to N400 (difference wave Incong. – Cong.), showed the crucial role of Inferior and Superior Temporal Gyri in the multimodal representation of emotional information extracted from faces and music. Furthermore, the prefrontal cortex (superior and medial, BA 10) was also strongly active, possibly supporting working memory. The data hints at a common system for representing emotional information derived by social cognition and music processing, including uncus and cuneus.

Modality-specific sensory readiness for upcoming events revealed by slow cortical potentials.

Human brain activity allows to anticipate future events and to prepare the next action accordingly; consistently, event-related potential (ERP) studies found action preparatory brain activities in the premotor and prefrontal cortex. In the present study, we investigated the preparatory activity in the sensory cortical regions. Slow cortical potentials were recorded during passive tasks, i.e., subjects expected for a sensory stimulus and no motor or cognitive response were required. In particular, we tested the hypothesis that perceptual anticipatory cortical mechanisms were modality specific. Three groups of 21 young adults underwent passive perceptual tasks in different sensory modalities (visual, auditory, or somatosensory). We confirmed the presence of a visual negativity (vN) component for the visual modality starting about 800ms before stimulus with source in extrastriate areas and we found novel modality-specific sensory readiness components for the auditory and somatosensory modalities. The auditory positivity (aP) started about 800ms before stimulus with source in bilateral auditory cortices and the somatosensory negativity (sN) started about 500ms before stimulus with source in the somatosensory secondary cortex, contralateral to the stimulated hand. The scalp topography and intracranial sources of these three slow preparatory activities were mirrored with inverted polarity at early post-stimulus stage evoking the well-known visual P1, auditory N1, and somatosensory P100 components. Present findings contribute to widening the family of slow wave preparatory components, providing evidence about the relationship between top-down and bottom-up processing in sensory perception.

Sensory attenuation prevails when controlling for temporal predictability of self- and externally generated tones

Sensory attenuation of self-produced, compared to physically identical but externally produced events is a classical finding in research on perception in action. The most prominent model to explain this effect draws on an internal forward model generating predictions about action outcomes, efference copies, during action planning and initiation. Even though this finding has a long tradition in psychology and neuroscience, several studies have highlighted methodological limitations which open the door for alternative explanations of sensory attenuation effects, most notably in terms of temporal prediction. Here we present an experimental design which carefully controls for this confounding factor. Crucially, we observed the auditory N1 component of the event-related potential to be attenuated for self-generated tones as compared to externally generated tones even when a predictive cue (a bar that is continuously filling up) allows for identical temporal predictability of both events. These findings suggest that voluntary actions do indeed involve a unique, predictive component, affecting the perceptual processing of ensuing events.

Single-subject analysis of N400 event-related potential component with five different methods

There are several different approaches to analyze event-related potentials (ERPs) at single-subject level, and the aim of the current study is to provide information for choosing a method based on its ability to detect ERP effects and factors influencing the results. We used data from 79 healthy participants with EEG referenced to mastoid average and investigated the detection rate of auditory N400 effect in single-subject analysis using five methods: visual inspection of participant-wise averaged ERPs, analysis of variance (ANOVA) for amplitude averages in a time window, cluster-based non-parametric testing, a novel Bayesian approach and Studentized continuous wavelet transform (t-CWT). Visual inspection by three independent raters yielded N400 effect detection in 85% of the participants in at least one paradigm (active responding or passive listening), whereas ANOVA identified the effect in 68%, the cluster-method in 59%, the Bayesian method in 89%, and different versions of t-CWT in 22–59% of the participants. Thus, the Bayesian method was the most liberal and also showed the greatest concordance between the experimental paradigms (active/passive). ANOVA detected significant effect only in cases with converging evidence from other methods. The t-CWT and cluster-based method were the most conservative methods. As we show in the current study, different analysis methods provide results that do not completely overlap. The method of choice for determining the presence of an ERP component at single-subject level thus remains unresolved. Relying on a single statistical method may not be sufficient for drawing conclusions on single-subject ERPs.

Electrophysiological Evidence for Top-Down Lexical Influences on Early Speech Perception

An unresolved issue in speech perception concerns whether top-down linguistic information influences perceptual responses. We addressed this issue using the event-related-potential technique in two experiments that measured cross-modal sequential-semantic priming effects on the auditory N1, an index of acoustic-cue encoding. Participants heard auditory targets (e.g., “potatoes”) following associated visual primes (e.g., “MASHED”), neutral visual primes (e.g., “FACE”), or a visual mask (e.g., “XXXX”). Auditory targets began with voiced (/b/, /d/, /g/) or voiceless (/p/, /t/, /k/) stop consonants, an acoustic difference known to yield differences in N1 amplitude. In Experiment 1 (N = 21), semantic context modulated responses to upcoming targets, with smaller N1 amplitudes for semantic associates. In Experiment 2 (N = 29), semantic context changed how listeners encoded sounds: Ambiguous voice-onset times were encoded similarly to the voicing end point elicited by semantic associates. These results are consistent with an interactive model of spoken-word recognition that includes top-down effects on early perception.

Abnormal development of early auditory processing in 22q11.2 Deletion Syndrome

The 22q11.2 Deletion Syndrome (22q11.2 DS) is one of the highest genetic risk factors for the development of schizophrenia spectrum disorders. In schizophrenia, reduced amplitude of the frequency mismatch negativity (fMMN) has been proposed as a promising neurophysiological marker for progressive brain pathology. In this longitudinal study in 22q11.2 DS, we investigate the progression of fMMN between childhood and adolescence, a vulnerable period for brain maturation. We measured evoked potentials to auditory oddball stimuli in the same sample of 16 patients with 22q11.2 DS and 14 age-matched controls in childhood and adolescence. In addition, we cross-sectionally compared an increased sample of 51 participants with 22q11.2 DS and 50 controls divided into two groups (8–14 and 14–20 years). The reported results are obtained using the fMMN difference waveforms. In the longitudinal design, the 22q11.2 deletion carriers exhibit a significant reduction in amplitude and a change in topographic patterns of the mismatch negativity response from childhood to adolescence. The same effect, reduced mismatch amplitude in adolescence, while preserved during childhood, is observed in the cross-sectional study. These results point towards functional changes within the brain network responsible for the fMMN. In addition, the adolescents with 22q11.2 DS displayed a significant increase in amplitude over central electrodes during the auditory N1 component. No such differences, reduced mismatch response nor increased N1, were observed in the typically developing group. These findings suggest different developmental trajectories of early auditory sensory processing in 22q11.2 DS and functional changes that emerge during the critical period of increased risk for schizophrenia spectrum disorders.

Presentation Probability of Visual-Auditory Pairs Modulates Visually Induced Auditory Predictions.

Predictions about forthcoming auditory events can be established on the basis of preceding visual information. Sounds being incongruent to predictive visual information have been found to elicit an enhanced negative ERP in the latency range of the auditory N1 compared with physically identical sounds being preceded by congruent visual information. This so-called incongruency response (IR) is interpreted as reduced prediction error for predicted sounds at a sensory level. The main purpose of this study was to examine the impact of probability manipulations on the IR. We manipulated the probability with which particular congruent visual-auditory pairs were presented (83/17 vs. 50/50 condition). This manipulation led to two conditions with different strengths of the association of visual with auditory information. A visual cue was presented either above or below a fixation cross and was followed by either a high- or low-pitched sound. In 90% of trials, the visual cue correctly predicted the subsequent sound. In one condition, one of the sounds was presented more frequently (83% of trials), whereas in the other condition both sounds were presented with equal probability (50% of trials). Therefore, in the 83/17 condition, one congruent combination of visual cue and corresponding sound was presented more frequently than the other combinations presumably leading to a stronger visual-auditory association. A significant IR for unpredicted compared with predicted but otherwise identical sounds was observed only in the 83/17 condition, but not in the 50/50 condition, where both congruent visual cue-sound combinations were presented with equal probability. We also tested whether the processing of the prediction violation is dependent on the task relevance of the visual information. Therefore, we contrasted a visual-auditory matching task with a pitch discrimination task. It turned out that the task only had an impact on the behavioral performance but not on the prediction error signals. Results suggest that the generation of visual-to-auditory sensory predictions is facilitated by a strong association between the visual cue and the predicted sound (83/17 condition) but is not influenced by the task relevance of the visual information.

Semantic context influences early speech perception: Evidence from electrophysiology

An unresolved issue in speech perception concerns whether top-down lexical information influences early perceptual representations. This was addressed using the event-related potential (ERP) technique to measure semantic priming effects on the auditory N1, an index of initial acoustic cue encoding. Participants saw visual primes that formed a clear association with the target (Association: “MARCHING band”), led to no specific association (Neutral: “BUTTER bomb”), or consisted of a non-word Mask. Auditory targets were stop consonants varying in voice onset time (VOT) between voiced (/b,d,g/) and voiceless (/p,t,k/) pairs. Participants were faster to identify the initial sound of the target in the Association condition than the Neutral and Mask conditions, and ERP responses showed the expected bottom-up effect of stimulus VOT (larger N1s for shorter VOTs). In Experiment 1, Association primes produced smaller N1s when targets were perfectly predictive, suggesting a top-down attentional effect. In Experiment 2, ambiguous and unexpected VOTs were added, and the results demonstrated that ambiguous VOTs in the Association condition were encoded similarly to the voicing endpoint that matched the semantic context (i.e., larger N1s for voiced expectations). These results provide the first ERP evidence that top-down lexical information directly influences early perceptual responses.

Electrophysiological alterations in motor-auditory predictive coding in autism spectrum disorder.

The amplitude of the auditory N1 component of the event‐related potential (ERP) is typically attenuated for self‐initiated sounds, compared to sounds with identical acoustic and temporal features that are triggered externally. This effect has been ascribed to internal forward models predicting the sensory consequences of one's own motor actions. The predictive coding account of autistic symptomatology states that individuals with autism spectrum disorder (ASD) have difficulties anticipating upcoming sensory stimulation due to a decreased ability to infer the probabilistic structure of their environment. Without precise internal forward prediction models to rely on, perception in ASD could be less affected by prior expectations and more driven by sensory input. Following this reasoning, one would expect diminished attenuation of the auditory N1 due to self‐initiation in individuals with ASD. Here, we tested this hypothesis by comparing the neural response to self‐ versus externally‐initiated tones between a group of individuals with ASD and a group of age matched neurotypical controls. ERPs evoked by tones initiated via button‐presses were compared with ERPs evoked by the same tones replayed at identical pace. Significant N1 attenuation effects were only found in the TD group. Self‐initiation of the tones did not attenuate the auditory N1 in the ASD group, indicating that they may be unable to anticipate the auditory sensory consequences of their own motor actions. These results show that individuals with ASD have alterations in sensory attenuation of self‐initiated sounds, and support the notion of impaired predictive coding as a core deficit underlying autistic symptomatology. Autism Res 2019, 12: 589–599. © 2019 The Authors. Autism Research published by International Society for Autism Research published by Wiley Periodicals, Inc.Lay SummaryMany individuals with ASD experience difficulties in processing sensory information (for example, increased sensitivity to sound). Here we show that these difficulties may be related to an inability to anticipate upcoming sensory stimulation. Our findings contribute to a better understanding of the neural mechanisms underlying the different sensory perception experienced by individuals with ASD.

Brain Vital Signs: Expanding From the Auditory to Visual Modality.

The critical need for rapid objective, physiological evaluation of brain function at point-of-care has led to the emergence of brain vital signs—a framework encompassing a portable electroencephalography (EEG) and an automated, quick test protocol. This framework enables access to well-established event-related potential (ERP) markers, which are specific to sensory, attention, and cognitive functions in both healthy and patient populations. However, all our applications to-date have used auditory stimulation, which have highlighted application challenges in persons with hearing impairments (e.g., aging, seniors, dementia). Consequently, it has become important to translate brain vital signs into a visual sensory modality. Therefore, the objectives of this study were to: 1) demonstrate the feasibility of visual brain vital signs; and 2) compare and normalize results from visual and auditory brain vital signs. Data were collected from 34 healthy adults (33 ± 13 years) using a 64-channel EEG system. Visual and auditory sequences were kept as comparable as possible to elicit the N100, P300, and N400 responses. Visual brain vital signs were elicited successfully for all three responses across the group (N100: F = 29.8380, p < 0.001; P300: F = 138.8442, p < 0.0001; N400: F = 6.8476, p = 0.01). Initial auditory-visual comparisons across the three components showed attention processing (P300) was found to be the most transferrable across modalities, with no group-level differences and correlated peak amplitudes (rho = 0.7, p = 0.0001) across individuals. Auditory P300 latencies were shorter than visual (p < 0.0001) but normalization and correlation (r = 0.5, p = 0.0033) implied a potential systematic difference across modalities. Reduced auditory N400 amplitudes compared to visual (p = 0.0061) paired with normalization and correlation across individuals (r = 0.6, p = 0.0012), also revealed potential systematic modality differences between reading and listening language comprehension. This study provides an initial understanding of the relationship between the visual and auditory sequences, while importantly establishing a visual sequence within the brain vital signs framework. With both auditory and visual stimulation capabilities available, it is possible to broaden applications across the lifespan.

Sound Change Integration Error: An Explanatory Model of Tinnitus.

A growing body of research is focused on identifying and understanding the neurophysiological mechanisms that underlie tinnitus. Unfortunately, however, most current models cannot adequately explain the majority of tinnitus features. For instance, although tinnitus generally appears within minutes after entering a silent environment, most models postulate that tinnitus emerges over a much larger timescale (days). Similarly, there is a limited understanding of how the severity of tinnitus can differ in patients with a similar degree of hearing loss. To address this critical knowledge gap, we have formulated a novel explanatory model of tinnitus, the perception-update (PU) model, which rests on a theory of information processing and can explain several key characteristics of tinnitus onset. The PU model posits that the brain continuously updates the information received from the inner ear by comparing it to the received information immediately before. That is, the auditory system processes the relative change in sensory input, as opposed to the absolute value of the auditory input. This is analogous to the functioning of data compression technology used for music and images called differential pulse code modulation (differential PCM). The PU model proposes that the inner ear transmits sound change to the auditory cortex via an auditory N1 response, an event-related potential component that constitutes is a prime signaler of auditory input change. In cases of hearing impairment, the PU model posits that the auditory system finds itself in a state of uncertainty where perception has to be predicted based on previous stimulation parameters, which can lead to the emergence of tinnitus.

The influence of the global/local probability effect on the neural processing of cues and targets. A functional systems approach.

Global and local probability effects were explored in a visuo-auditory version of the central cue Posner's paradigm through the analysis of the neural Event-Related Potentials (ERPs) generated in the interaction between validity sequence effects (local probability) and block validity effects (global probability). Four behavioral measures (response times, correct/incorrect anticipations, and incorrect responses), three pre-target ERPs (visual P1/N1 and Contingent Negative Variation (CNV)), and six post-target ERPs (auditory N1, P2, Processing Negativity (PN), P3a, P3b and Late Slow Positivity (LSP)) were considered. Four types of trial-sequences (Valid-Valid, Invalid-Valid, Invalid-Invalid, Valid-Invalid) and three types of trial-blocks, with different validity/invalidity proportions (50%, 68%, and 86% of valid trials), were employed. Present data replicate previous reports on the validity sequence effects on ERPs (local probability): (i) higher CNV on trials preceded by valid trials; (ii) higher PN on valid trials preceded by invalid trials compared to valid trials preceded by valid trials; and (iii) higher P3a/P3b and LSP on invalid trials preceded by valid trials compared to invalid trials preceded by invalid trials. In summary, local probability showed more effects modulating the brain responses than global probability and/or their interaction. Among a number of other hypotheses, the functional systems theory would account for the ability of the previous trial to modify processing in the current trial.

Cross-modal phonetic encoding facilitates the McGurk illusion and phonemic restoration.

In spoken language, audiovisual (AV) perception occurs when the visual modality influences encoding of acoustic features (e.g., phonetic representations) at the auditory cortex. We examined how visual speech (mouth movements) transforms phonetic representations, indexed by changes to the N1 auditory evoked potential (AEP). EEG was acquired while human subjects watched and listened to videos of a speaker uttering consonant vowel (CV) syllables, /ba/ and /wa/, presented in auditory-only or AV congruent or incongruent contexts or in a context in which the consonants were replaced by white noise (noise replaced). Subjects reported whether they heard "ba" or "wa." We hypothesized that the auditory N1 amplitude during illusory perception (caused by incongruent AV input, as in the McGurk illusion, or white noise-replaced consonants in CV utterances) should shift to reflect the auditory N1 characteristics of the phonemes conveyed visually (by mouth movements) as opposed to acoustically. Indeed, the N1 AEP became larger and occurred earlier when listeners experienced illusory "ba" (video /ba/, audio /wa/, heard as "ba") and vice versa when they experienced illusory "wa" (video /wa/, audio /ba/, heard as "wa"), mirroring the N1 AEP characteristics for /ba/ and /wa/ observed in natural acoustic situations (e.g., auditory-only setting). This visually mediated N1 behavior was also observed for noise-replaced CVs. Taken together, the findings suggest that information relayed by the visual modality modifies phonetic representations at the auditory cortex and that similar neural mechanisms support the McGurk illusion and visually mediated phonemic restoration. NEW & NOTEWORTHY Using a variant of the McGurk illusion experimental design (using the syllables /ba/ and /wa/), we demonstrate that lipreading influences phonetic encoding at the auditory cortex. We show that the N1 auditory evoked potential morphology shifts to resemble the N1 morphology of the syllable conveyed visually. We also show similar N1 shifts when the consonants are replaced by white noise, suggesting that the McGurk illusion and the visually mediated phonemic restoration rely on common mechanisms.

Post-sauna recovery enhances brain neural network relaxation and improves cognitive economy in oddball tasks

Objective: The aim of this study was to investigate the post-sauna residual consequences on brain neural network arousal, information processing and cognitive performance.Methods: Sixteen male subjects (24 ± 1 yr.) participated in the study. Whole-body hyperthermia was induced with Finnish sauna bathing. Before and 90 min after the sauna, resting electroencephalography (EEG) for spectral analysis and EEG event-related potentials (ERPs) during oddball tasks by two modalities (auditory and visual) were recorded.Results: Sauna bathing increased rectal temperature (Tre, 37.11 ± 0.33 °C to 38.84 ± 0.32 °C) and heart rate (HR, 65.63 ± 9.39 bpm to 151.0 ± 21.8 bpm). At 90 min after the sauna, Tre (37.00 ± 0.29 °C) and HR (72.1 ± 2.80 bpm) recovered to baseline levels. An increase was found in alpha power following sauna recovery. In the visual task modality, post-sauna recovery led to enhancement in the N2 amplitude with centroparietal distribution and decreases in P3 amplitude with distribution along the frontoparietal axis for executive motor–cognitive processing. In the auditory task modality, post-sauna recovery led to a decrease in P3 amplitude with a frontoparietal distribution and this change was accompanied by auditory N2 amplitude enhancement along the centroparietal distribution for non-target cognitive processing. No significant differences in task performance were found.Conclusion: Post-sauna recovery to normothermia led to enhanced resting neural network relaxation followed by increases in cognitive processing economy for the given oddball tasks. The auditory processing was not affected more by post-sauna recovery than was visual processing. Post-sauna recovery modifications in ERP components (stimulus processing) were insufficient to affect cognitive performance in both visual and auditory task modalities.

Auditory N100 gating in patients with schizophrenia: A systematic meta-analysis

ObjectiveThe study sought to assess the presence of auditory N100 gating deficits in patients with schizophrenia by meta-analysis. MethodsLiterature was screened for studies on patients with schizophrenia that used the paired-click paradigm and reported N100 data. Both electroencephalographic and magnetoencephalographic studies were considered. N100 gating measures as well as the N100 amplitudes to the initial and repeated stimulus were extracted and subjected to a meta-analysis. ResultsThe literature research revealed 29 studies, reporting either N100 gating or N100 amplitude measures in paired-click experiments. Patients with schizophrenia exhibited less N100 gating than healthy controls across studies (mean g = −0.405, SE = 0.051). However, what appeared as a gating deficit in patients was due to reduced N100 amplitudes to the initial stimulus in this group (mean g = 0.610, SE = 0.075). Patients and controls did not differ in their N100 amplitudes to the repeated stimulus (mean g = 0.042, SE = 0.066). ConclusionThere is no evidence for an auditory N100 gating deficit in schizophrenia, but for an impaired N100 response recovery. SignificancePrevious findings on impaired N100 gating in schizophrenia patients reflect deficient processing of auditory salience rather than defective inhibition of repeating redundant auditory stimulation.