Auditory processing indexed by stimulus-induced alpha desynchronization in children.

By means of magnetoencephalography (MEG), we investigated event-related synchronization and desynchronization (ERS/ERD) in auditory cortex activity, recorded from twelve children aged four to six years, while they passively listened to a violin tone and a noise-burst stimulus. Time-frequency analysis using Wavelet Transform was applied to single-trials of source waveforms observed from left and right auditory cortices. Stimulus-induced changes in non-phase-locked activities were evident. ERS in the beta range (13-30 Hz) lasted only for 100 ms after stimulus onset. This was followed by prominent alpha ERD, which showed a clear dissociation between the upper (12 Hz) and lower (8 Hz) alpha range in both left and right auditory cortices for both stimuli. The time courses of the alpha ERD (onset around 300 ms, peak at 500 ms, offset after 1500 ms) were similar to those previously found for older children and adults with auditory memory related tasks. For the violin tone only, the ERD lasted longer in the upper than the lower alpha band. The findings suggest that induced alpha ERD indexes auditory stimulus processing in children without specific cognitive task requirement. The left auditory cortex showed a larger and longer-lasting upper alpha ERD than did the right auditory cortex, likely reflecting hemispheric differences in maturational stages of neural oscillatory mechanisms.     

An event-related potential study on cross-modal conversion of Chinese characters

In the current study, we explored the effects of ERPs (event-related potentials), related to the cross-modal transfer from visual input to phonological retrieval. Using Chinese single-character words, participants were asked to make orthographic (intra-modal) and phonological (cross-modal) responses to visually presented words. By comparing the cross-modal and intra-modal tasks, we found that both tasks evoke similar activity in the early stage of lexical processing, showing the same pattern of N2 effect (a negative component peaking around 220 ms) and P2 effect (a positive component peaking around 270 ms). However, the effect of the task was significant in the 300-700 ms time window, consisting of a frontal-based N400 effect and a parietal based late positive component (LPC) effect. These findings suggest that the frontal-based N400 is associated with orthography-to-phonology mapping in Chinese, and the LPC reflects greater requirement of maintaining retrieved information in working memory for the cross-modal processing.     

Auditory processing in an inter-modal oddball task: effects of a combined auditory/visual standard on auditory target ERPs.

Previous research examining auditory target ERPs in an inter-modal oddball task has shown that early components are affected by intra-modal processes, whilst components in the later part of the ERP, around 200-400 ms, are affected by both inter-modal and intra-modal processes. These findings led to the conclusion that there are separate stages of auditory target processing--an early modality-specific stage and a later context-dependent stage. The present study investigated this further by simultaneously presenting a visual standard stimulus with an auditory standard stimulus in an oddball task. The aim was to determine whether the inclusion of the visual standard stimulus in this task affected the ERP to targets. The auditory-visual oddball task consisted of a regularly presented combined auditory and visual standard stimulus (80%) and an infrequent auditory target (20%). The ERPs to targets in the auditory-visual oddball task were compared to those in an auditory oddball task, which had identical auditory stimuli and no visual standards. The results showed that the early components N100, P200 and N200 did not differ between tasks. This was in line with earlier results, and confirmed that activity up to 200 ms is unaffected by visual standard stimuli. The later components P250, P300 and P350 were larger and showed topographic differences in the auditory-visual oddball task. This was interpreted as reflecting separate inter-modal and intra-modal processes at later stages. In particular, the P300 and P350 components were argued to represent separate inter-modal and intra-modal components. Overall, this study provides further evidence of auditory processing occurring in two stages, an early modality-dependent stage and a later context-dependent stage.     

Induced EEG alpha oscillations are related to mental rotation ability: The evidence for neural efficiency and serial processing

People with better skills in mental rotation require less time to decide about the identity of rotated images. In the present study, alphanumeric characters rotated in the frontal plane were employed to assess the relationship between rotation ability and EEG oscillatory activity. Response latency, a single valid index of performance in this task, was significantly associated with the amplitude of induced oscillations in the alpha (8–13 Hz) and the low beta band (14–20 Hz). In accordance with the neural efficiency hypothesis, less event-related desynchronization (ERD) was related to better (i.e. faster) task performance. The association between response time and ERD was observed earlier (∼600–400 ms before the response) over the parietal cortex and later (∼400–200 ms before the response) over the frontal cortex. Linear mixed-effect regression analysis confirmed that both early parietal and late frontal alpha/beta power provided significant contribution to prediction of response latency. The result indicates that two distinct serially engaged neurocognitive processes comparably contribute to mental rotation ability. In addition, we found that mental rotation-related negativity, a slow event-related potential recorded over the posterior cortex, was unrelated to the asymmetry of alpha amplitude modulation.     

Sequential processing of interaural timing differences for sound source segregation and spatial localization: evidence from event-related cortical potentials

Cortical processing of interaural timing differences (ITDs) was investigated with event-related potential (ERP) measurements in 16 human participants who were required in separate tasks to detect or to spatially localize dichotically embedded pitches. ITDs elicited three ERP components labeled ORN, N2, and P400. The ORN occurred at a latency of 150-250 ms and was elicited by ITDs regardless of location or task. In contrast, the N2 response (250-350 ms) was strongly modulated by location and showed larger amplitudes for the localization task than for the detection task. Finally, ITDs in the detection task elicited a P400 at a latency of 400-500 ms, but this response was entirely absent from ERPs elicited by identical stimuli in the localization task. These results are consistent with a sequential model of auditory perception in which segregation of concurrent sounds is followed by domain-specific processing of object location and identity.     

Following the time course of face gender and expression processing: A task-dependent ERP study

The effects of task demands and the interaction between gender and expression in face perception were studied using event-related potentials (ERPs). Participants performed three different tasks with male and female faces that were emotionally inexpressive or that showed happy or angry expressions. In two of the tasks (gender and expression categorization) facial properties were task-relevant while in a third task (symbol discrimination) facial information was irrelevant. Effects of expression were observed on the visual P100 component under all task conditions, suggesting the operation of an automatic process that is not influenced by task demands. The earliest interaction between expression and gender was observed later in the face-sensitive N170 component. This component showed differential modulations by specific combinations of gender and expression (e.g., angry male vs. angry female faces). Main effects of expression and task were observed in a later occipito-temporal component peaking around 230 ms post-stimulus onset (EPN or early posterior negativity). Less positive amplitudes in the presence of angry faces and during performance of the gender and expression tasks were observed. Finally, task demands also modulated a positive component peaking around 400 ms (LPC, or late positive complex) that showed enhanced amplitude for the gender task. The pattern of results obtained here adds new evidence about the sequence of operations involved in face processing and the interaction of facial properties (gender and expression) in response to different task demands.     

Phasic boosting of auditory perception by visual emotion

Emotionally negative stimuli boost perceptual processes. There is little known, however, about the timing of this modulation. The present study aims at elucidating the phasic effects of, emotional processing on auditory processing within subsequent time-windows of visual emotional, processing in humans. We recorded the electroencephalogram (EEG) while participants responded to a, discrimination task of faces with neutral or fearful expressions. A brief complex tone, which subjects, were instructed to ignore, was displayed concomitantly, but with different asynchronies respective to, the image onset. Analyses of the N1 auditory event-related potential (ERP) revealed enhanced brain, responses in presence of fearful faces. Importantly, this effect occurred at picture-tone asynchronies of, 100 and 150 ms, but not when these were displayed simultaneously, or at 50 ms or 200 ms asynchrony. These results confirm the existence of a fast-operating crossmodal effect of visual emotion on auditory, processing, suggesting a phasic variation according to the time-course of emotional processing.     

The Müller–Lyer illusion seen by the brain: An event-related brain potentials study

In two experiments, event-related brain potentials (ERPs) were used to examine the neural correlates of a visual illusion effect in Müller–Lyer illusion tasks (illusion stimuli) and baseline tasks (no-illusion stimuli). The behavioral data showed that the illusion stimuli indeed yielded an illusion effect. Scalp ERP analysis revealed its neurophysiological substrate: the Müller–Lyer illusion tasks (Illusion tasks 1–3) elicited a more negative ERP deflection than did the baseline tasks about 400 ms after onset of the stimuli. Dipole source analysis of the difference wave (Illusion task 2–Baseline task 1) and the original waveforms of the different conditions (Illusion tasks 2 and 3 and Baseline task 2) indicated that the anterior cingulate cortex (ACC)/superior frontal cortex may contribute to the illusion effect, possibly in relation to high-level cognitive control. The results indicated that apparent distortions of the Müller–Lyer illusion might be influenced by top-down control.     

Effect of deviance direction and calculation method on duration and frequency mismatch negativity (MMN)

The mismatch negativity (MMN) component of the auditory event-related potential (ERP) reflects the process of change detection in the auditory system. The present study investigated the effect of deviance direction (increment vs. decrement) and calculation method (traditional vs. same-stimulus) on the amplitude of MMN. MMN was recorded for increments and decrements in frequency and duration in 20 adults. The stimuli (standard/deviant) were 250 Hz/350 Hz (frequency MMN) and 200 ms/300 ms (duration MMN) for increment MMN and vice versa for decrement MMN. Amplitude of MMN was calculated in two ways: the traditional method (subtracting ERP to the standard from the deviant presented in the same block) and the same-stimulus method (subtracting ERP to identical stimuli presented as standard in one block and deviant in another block). We found that increments in frequency produced higher MMN amplitudes compared to decrements for both methods of calculation. For duration deviance, the decrement MMN was absent in the traditional method, while the decrement and increment MMN did not differ for the same-stimulus method. These findings suggest that the brain processes frequency increments and decrements in different ways. The results also suggest the use of same-stimulus method for the calculation of duration MMN when long duration stimuli are used.     

Neural activities of tactile cross-modal working memory in humans: an event-related potential study

In the present study, we examined the neural mechanisms underlying cross-modal working memory by analyzing scalp-recorded event-related potentials (ERPs) from normal human subjects performing tactile-tactile unimodal or tactile-auditory cross-modal delay tasks that consisted of stimulus-1 (S-1, tactile), interval (delay), and stimulus-2 (S-2, tactile or auditory). We hypothesized that there would be sequentially discrete task-correlated changes in ERPs representing neural processes of tactile working memory, and in addition, significant differences would be observed in ERPs between the unimodal task and the cross-modal task. In comparison to the ERP components in the unimodal task, two late positive ERP components (LPC-1 and LPC-2) evoked by the tactile S-1 in the delay of the cross-modal task were enhanced by expectation of the associated auditory S-2 presented at the end of the delay. Such enhancement might represent neural activities involved in cross-modal association between the tactile stimulus and the auditory stimulus. Later in the delay, a late negative component (LNC) was observed. The amplitude of LNC depended on information retained during the delay, and when the same information was retained, this amplitude was not influenced by modality or location of S-2 (auditory S-2 through headphones, or tactile S-2 on the left index finger). LNC might represent the neural activity involved in working memory. The above results suggest that the sequential ERP changes in the present study represent temporally distinguishable neural processes, such as the cross-modal association and cross-modal working memory.     

Emotion and attention in visual word processing: an ERP study

Emotional words are preferentially processed during silent reading. Here, we investigate to what extent different components of the visual evoked potential, namely the P1, N1, the early posterior negativity (EPN, around 250 ms after word onset) as well as the late positive complex (LPC, around 500 ms) respond differentially to emotional words and whether this response depends on the availability of attentional resources. Subjects viewed random sequences of pleasant, neutral and unpleasant adjectives and nouns. They were first instructed to simply read the words and then to count either adjectives or nouns. No consistent effects emerged for the P1 and N1. However, during both reading and counting the EPN was enhanced for emotionally arousing words (pleasant and unpleasant), regardless of whether the word belonged to a target or a non-target category. A task effect on the EPN was restricted to adjectives, but the effect did not interact with emotional content. The later centro-parietal LPC (450-650 ms) showed a large enhancement for the attended word class. A small and topographically distinct emotion-LPC effect was found specifically in response to pleasant words, both during silent reading and the active task. Thus, emotional word content is processed effortlessly and automatically and is not subject to interference from a primary grammatical decision task. The results are in line with other reports of early automatic semantic processing as reflected by posterior negativities in the ERP around 250 ms after word onset. Implications for models of emotion-attention interactions in the brain are discussed.     

Express saccades in cat: effects of task and target modality

Saccadic eye movements to visual, auditory, and bimodal targets were measured in four adult cats. Bimodal targets were visual and auditory stimuli presented simultaneously at the same location. Three behavioral tasks were used: a fixation task and two saccadic tracking tasks (gap and overlap task). In the fixation task, a sensory stimulus was presented at a randomly selected location, and the saccade to fixate that stimulus was measured. In the gap and overlap tasks, a second target (hereafter called the saccade target) was presented after the cat had fixated the first target. In the gap task, the fixation target was switched off before the saccade target was turned on; in the overlap task, the saccade target was presented before the fixation target was switched off. All tasks required the cats to redirect their gaze toward the target (within a specified degree of accuracy) within 500 ms of target onset, and in all tasks target positions were varied randomly over five possible locations along the horizontal meridian within the cat's oculomotor range. In the gap task, a significantly greater proportion of saccadic reaction times (SRTs) were less than 125 ms, and mean SRTs were significantly shorter than in the fixation task. With visual targets, saccade latencies were significantly shorter in the gap task than in the overlap task, while, with bimodal targets, saccade latencies were similar in the gap and overlap tasks. On the fixation task, SRTs to auditory targets were longer than those to either visual or bimodal targets, but on the gap task, SRTs to auditory targets were shorter than those to visual or bimodal targets. Thus, SRTs reflected an interaction between target modality and task. Because target locations were unpredictable, these results demonstrate that cats, as well as primates, can produce very short latency goal-directed saccades.     

Auditory probe sensitivity to mental workload changes – an event-related potential study

The goal of this study was to explore the utility of parameters of ERPs for assessment of mental workload during performance of complex tasks. In addition to a baseline auditory oddball task, 15 healthy adult volunteers performed gauge monitoring (Gauge) and mental arithmetic (Math) separately and together. Throughout the task performance three types of auditory stimuli were presented as probes, i.e. 80% 1000 Hz tones, 10% 2000 Hz tones and 10% novel sounds. The ERP components N1 and P3 were analysed, which are assumed to reflect perceptive and central processing resources. The results interpreted in the framework of capacity theory indicate high demand on processing resources already during separate performance of both tasks Gauge or Math. During simultaneous performance the workload on average exceeded the limits of processing capacity: the performance data impaired significantly. The ERP measures N1 and P3 were confirmed in their sensitivity and diagnosticity. By using novel sounds as probes with involuntary attention-capturing properties, one might overcome a problem of the irrelevant probe technique, i.e. whether the operator spends his spare capacity for processing of the irrelevant probes.     

Effects of mental workload on long-latency auditory-evoked-potential,salivary cortisol,and immunoglobulin A

This paper researches on the effects of mental workload on long-latency auditory-evoked-potential (AEP), salivary cortisol, and immunoglobulin A (IgA). 20 Healthy subjects (11 males and 9 females) participated in the experiment voluntarily. The mental task consisted of two parts: arithmetic task and reading comprehension task. The Latencies of N1, P2, N2, P3, and mismatch negativity (MMN) all increased significantly after the mental tasks were adopted at all of the three recording sites: Cz, Fz, and Pz (p < 0.05). In this experiment, changes of salivary cortisol and s-IgA levels due to mental tasks were not significant. With the introduction of mental tasks, more processing resources are allocated to the primary task (mental task), and decreased processing resources available for the secondary task (auditory task), which is reflected on the increases in the latencies of probe-evoked AEP components.     

Auditory event-related potentials and alpha oscillations in the psychosis prodrome: Neuronal generator patterns during a novelty oddball task

Prior research suggests that event-related potentials (ERP) obtained during active and passive auditory paradigms, which have demonstrated abnormal neurocognitive function in schizophrenia, may provide helpful tools in predicting transition to psychosis. In addition to ERP measures, reduced modulations of EEG alpha, reflecting top-down control required to inhibit irrelevant information, have revealed attentional deficits in schizophrenia and its prodromal stage. Employing a three-stimulus novelty oddball task, nose-referenced 48-channel ERPs were recorded from 22 clinical high-risk (CHR) patients and 20 healthy controls detecting target tones (12% probability, 500 Hz; button press) among nontargets (76%, 350 Hz) and novel sounds (12%). After current source density (CSD) transformation of EEG epochs (− 200 to 1000 ms), event-related spectral perturbations were obtained for each site up to 30 Hz and 800 ms after stimulus onset, and simplified by unrestricted time–frequency (TF) principal components analysis (PCA). Alpha event-related desynchronization (ERD) as measured by TF factor 610–9 (spectral peak latency at 610 ms and 9 Hz; 31.9% variance) was prominent over right posterior regions for targets, and markedly reduced in CHR patients compared to controls, particularly in three patients who later developed psychosis. In contrast, low-frequency event-related synchronization (ERS) distinctly linked to novels (260–1; 16.0%; mid-frontal) and N1 sink across conditions (130–1; 3.4%; centro-temporoparietal) did not differ between groups. Analogous time-domain CSD-ERP measures (temporal PCA), consisting of N1 sink, novelty mismatch negativity (MMN), novelty vertex source, novelty P3, P3b, and frontal response negativity, were robust and closely comparable between groups. Novelty MMN at FCz was, however, absent in the three converters. In agreement with prior findings, alpha ERD and MMN may hold particular promise for predicting transition to psychosis among CHR patients.     

The different P200 effects of phonological and orthographic syllable frequency in visual word recognition in Korean

The principal purpose of this study was to examine whether event-related potential (ERP) waveform amplitudes at around 200 ms are affected by first-syllable frequency. Another purpose of this study was to investigate whether the source of the amplitude at around 200 ms is phonological syllable frequency or orthographic syllable frequency. The phonological first-syllable frequency and the orthographic first-syllable frequency of Korean pseudo-words were manipulated, and ERPs were collected during a go/no-go lexical decision task. The results of this study showed that the P200 waveform is sensitive to the frequency of the first phonological syllable; specifically, pseudo-words with higher phonological first-syllable frequency produced a lower P200 amplitude than those with lower phonological first-syllable frequency. The orthographic syllable frequency did not affect the P200 waveform. The present result implies that there may be different routes by which phonological syllables and orthographic syllables are processed during the early stage of the visual word recognition process.     

Neural correlates of serial abacus mental calculation in children: a functional MRI study

Abacus experts have demonstrated extraordinary potential of mental calculation by using an imaginary abacus. But the neural correlates of abacus mental calculation and the imaginary abacus still remain unclear. Here, we report, respectively, the analysis of fMRI images of abacus experts and non-experts in response to the performance of simple and complex serial calculation by visual stimuli as well as the images of the abacus experts with performance of the same tasks by auditory stimuli. We found that activated areas were quite different between two groups. In experts, enhanced activations were mainly observed in fronto-temporal circuit (lateral premotor cortex (LPMC) and posterior temporal areas) in simple addition, but in fronto-parietal circuit (lateral premotor cortex (LPMC) and posterior superior parietal lobe (PSPL)) in complex one. By contrast, in controls, the activated areas were almost similar in both simple and complex tasks, including bilateral inferior parietal lobule, prefrontal and premotor cortices. Furthermore, visual and auditory stimuli generated almost similar activations in experts. These observations reveal that (1) abacus mental calculation induces special patterns of brain response, and simple and complex tasks are sustained by dissociated brain circuits between the temporal and parietal cortices, respectively; (2) the abacus mental calculation may rely on neural resources of visuospatial representations with a super-modal form of abacus beads; (3) the posterior temporal areas and PSPL may be recruited for imaginary abacus.     

Machine Learning EEG to Predict Cognitive Functioning and Processing Speed Over a 2-Year Period in Multiple Sclerosis Patients and Controls

Event-related potentials (ERPs) show promise to be objective indicators of cognitive functioning. The aim of the study was to examine if ERPs recorded during an oddball task would predict cognitive functioning and information processing speed in Multiple Sclerosis (MS) patients and controls at the individual level. Seventy-eight participants (35 MS patients, 43 healthy age-matched controls) completed visual and auditory 2- and 3-stimulus oddball tasks with 128-channel EEG, and a neuropsychological battery, at baseline (month 0) and at Months 13 and 26. ERPs from 0 to 700 ms and across the whole scalp were transformed into 1728 individual spatio-temporal datapoints per participant. A machine learning method that included penalized linear regression used the entire spatio-temporal ERP to predict composite scores of both cognitive functioning and processing speed at baseline (month 0), and months 13 and 26. The results showed ERPs during the visual oddball tasks could predict cognitive functioning and information processing speed at baseline and a year later in a sample of MS patients and healthy controls. In contrast, ERPs during auditory tasks were not predictive of cognitive performance. These objective neurophysiological indicators of cognitive functioning and processing speed, and machine learning methods that can interrogate high-dimensional data, show promise in outcome prediction.     

Sequential processing in the classic oddball task: ERP components,probability, and behavior

This study compared the ERP components and behavior associated with the auditory equiprobable and classic oddball tasks, to relate the cognitive processing stages in those paradigms and continue the development of the sequential processing schema. Target and nontarget ERP data were acquired from 66 healthy young adults (M_age = 20.1, SD = 2.4 years, 14 male) who completed both equiprobable (target p = 0.5) and oddball tasks (target p = 0.3). Separate temporal PCAs were used to decompose the ERP data in each task and condition, and the similarity of the components identified in each condition was examined between tasks. Probability effects on component amplitudes and behavior were also analyzed to identify task differences in cognitive demands. A highly similar series of components was identified in each task, closely matching the schema: targets elicited N1‐3, N1‐1, PN, N2c, P3b, SW1, SW2; whereas nontargets elicited N1‐3, N1‐1, PN, N2b, P3a, SW1, SW2. N1‐1 and PN amplitudes increased as stimulus probability decreased, irrespective of the condition. N2b, P3b, SW1, and SW2 amplitudes also varied between tasks, illustrating task‐specific demands on those processing stages. These findings complemented the behavioral outcomes, which demonstrated greater accuracy and control in the classic oddball task. Overall, this study demonstrated comparable processing in the auditory equiprobable and classic oddball tasks, extending the generalizability of the schema and enabling further integration of the ERP theory associated with these tasks. This study also clarifies stimulus probability effects on the schema, providing important insight into the functionality of common ERP components.     

Alpha‐band desynchronization reflects memory‐specific processes during visual change detection

Recent work investigating physiological mechanisms of working memory (WM) has revealed that modulation of alpha and beta frequency bands within the EEG plays a key role in WM storage. However, the nature of that role is unclear. In the present study, we examined event‐related desynchronization of alpha and beta (α/β‐ERD) elicited by visual tasks with and without a memory component to measure the impact of a WM demand on this electrophysiological marker. We recorded EEG from 60 healthy participants while they completed three variants on a typical change detection task: one in which participants passively viewed the sample array, passive (WM?); one in which participants viewed and attended the sample array in search of a target color but did not memorize the colors, active (WM?); and one in which participants encoded, attended to, and memorized the sample array, active (WM+). Replicating previous findings, we found that active (WM+) elicited robust α/β‐ERD in frontal and posterior electrode clusters and that α‐ERD was significantly associated with WM capacity. By contrast, α/β‐ERD was significantly smaller in the passive (WM?) and active (WM?) tasks, which did not consistently differ from one another. Furthermore, no such relationship was observed between WM capacity and desynchronization in the passive (WM?) or active (WM?) tasks. Taken together, these results suggest that α‐ERD during memory formation reflects a memory‐specific process such as consolidation or maintenance, rather than serving a generalized role in perceptual gating or engagement of attention.