Event-related Spectral Perturbation Research Articles

Subthalamic stimulation modulates cortical motor network activity and synchronization in Parkinson’s disease

Dynamic modulations of large-scale network activity and synchronization are inherent to a broad spectrum of cognitive processes and are disturbed in neuropsychiatric conditions including Parkinson's disease. Here, we set out to address the motor network activity and synchronization in Parkinson's disease and its modulation with subthalamic stimulation. To this end, 20 patients with idiopathic Parkinson's disease with subthalamic nucleus stimulation were analysed on externally cued right hand finger movements with 1.5-s interstimulus interval. Simultaneous recordings were obtained from electromyography on antagonistic muscles (right flexor digitorum and extensor digitorum) together with 64-channel electroencephalography. Time-frequency event-related spectral perturbations were assessed to determine cortical and muscular activity. Next, cross-spectra in the time-frequency domain were analysed to explore the cortico-cortical synchronization. The time-frequency modulations enabled us to select a time-frequency range relevant for motor processing. On these time-frequency windows, we developed an extension of the phase synchronization index to quantify the global cortico-cortical synchronization and to obtain topographic differentiations of distinct electrode sites with respect to their contributions to the global phase synchronization index. The spectral measures were used to predict clinical and reaction time outcome using regression analysis. We found that movement-related desynchronization of cortical activity in the upper alpha and beta range was significantly facilitated with 'stimulation on' compared to 'stimulation off' on electrodes over the bilateral parietal, sensorimotor, premotor, supplementary-motor, and prefrontal areas, including the bilateral inferior prefrontal areas. These spectral modulations enabled us to predict both clinical and reaction time improvement from subthalamic stimulation. With 'stimulation on', interhemispheric cortico-cortical coherence in the beta band was significantly attenuated over the bilateral sensorimotor areas. Similarly, the global cortico-cortical phase synchronization was attenuated, and the topographic differentiation revealed stronger desynchronization over the (ipsilateral) right-hemispheric prefrontal, premotor and sensorimotor areas compared to 'stimulation off'. We further demonstrated that the cortico-cortical phase synchronization was largely dominated by genuine neuronal coupling. The clinical improvement with 'stimulation on' compared to 'stimulation off' could be predicted from this cortical decoupling with multiple regressions, and the reduction of synchronization over the right prefrontal area showed a linear univariate correlation with clinical improvement. Our study demonstrates wide-spread activity and synchronization modulations of the cortical motor network, and highlights subthalamic stimulation as a network-modulating therapy. Accordingly, subthalamic stimulation may release bilateral cortical computational resources by facilitating movement-related desynchronization. Moreover, the subthalamic nucleus is critical to balance inhibitory and facilitatory cortical players within the motor program.

Phase-locked theta activity evoked in patients with severe motor and intellectual disabilities upon hearing own names.

Severe motor and intellectual disability (SMID) patients cannot express their feelings with language. Understanding what they are thinking about or how they feel is thus difficult. This study focused on brain responses to hearing their own names to clarify the situation in these patients. We performed and analyzed electroencephalography (EEG) for six patients with SMID and eleven healthy subjects. All subjects were presented with auditory stimuli including calling the subject's own name (SON) and reading words. EEG was analyzed by time-frequency analysis, event-related spectral perturbation (ERSP) to detect EEG power changes caused by EEG amplitude, and inter-trial coherence (ITC) to investigate phase-locked changes. ERSP results from healthy subjects showed significant theta power increases as a specific response to SON. While we could not identify a similar pattern in the responses of patients with SMID, analysis of ITC revealed that theta phase-locked activity increased in response to SON not only in all healthy subjects, but also in four patients. These results indicate that theta phase-locked activity in some patients with SMID was strongly associated with SON, as in healthy subjects. Our study suggests the existence of specific neural markers that signal an attentional shift in patients upon hearing SON.

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.

Tic related local field potentials in the thalamus and the effect of deep brain stimulation in Tourette syndrome: Report of three cases

ObjectiveThree patients with intractable Tourette syndrome (TS) underwent thalamic deep brain stimulation (DBS). To investigate the role of thalamic electrical activity in tic generation, local field potentials (LFP), EEG and EMG simultaneously were recorded. MethodsEvent related potentials and event related spectral perturbations of EEG and LFP, event related cross-coherences between EEG/LFP and LFP/LFP were analyzed. As time locking events, the tic onsets were used. Spontaneous tics were compared to voluntary tic mimicking. The effect of tic suppression and DBS on thalamic LFPs was evaluated. ResultsAll three patients showed time-locked and prior to onset of spontaneous motor tics thalamic synchronization and thalamo-cortical cross-coherence. Also in three patients, not time-locked to motor tics, increased intra-thalamic coherences in the 1–8Hz frequency band were found. In one patient it was demonstrated that voluntary mimicked tics were preceded by premotor cortical and thalamic potentials. In this patient unilateral thalamic DBS contralaterally decreased the background thalamic activity. ConclusionsThe present study in three cases with TS shows that spontaneous tics in TS are preceded by repetitive coherent thalamo-cortical discharges, indicating that preceding a tic the basal ganglia circuits are “charged up”, ultimately leading to a motor tic. SignificanceThalamic LFP recording may lead to more insight in underlying pathophysiological mechanisms in TS.

청각자극에 따른 세타파와 알파파의 스펙트럼적 반응

감정을 유발하는 청각자극에 따라 발생되는 EEG(Electroencephalographic) 스펙트럼 강도와 감정 반응 간의 상관관계는 중요한 변수이다. 약 20여 년 전 쾌감을 주는 청각자극에 대하여 측정된 신호의 강도가 전전두엽에서 비대칭적으로 반응을 보였다는 연구 결과가 발표되었다. 본 연구에서는 자극관련 스펙트럼적 반응(Event-related Spectral Perturbation: ERSP)이 전두엽에서 비대칭적으로 발생되는지 고찰하기 위하여 청각자극 실험을 수행하였다. 30명의 건강한 대학생 지원자들이 IADS(International Affective Digital Sounds) 실험에 참여하였다. 이 청각자극은 행복, 공포, 그리고 중립의 3단계로 분류되었으며, 데이터의 분석은 세타파(4-8Hz)와 알파파(8-13Hz)에서 이루어졌다. 알파대역의 ERSP 지도는 오른쪽 전두엽에서 행복감과 공포감의 자극에서 높은 신호의 강도를 보여주는 반면 중립성 자극에서는 왼쪽 전두엽에서 높은 신호가 발생되었다. 그러나 세타파는 행복감과 공포감의 자극에 따라 좌측 전두엽에서 높은 신호가 나타나는 반면, 중립적 자극에 따라 우측 전두엽에서 높은 신호를 보여주었다. 높은 쾌감성 자극(행복)은 상대적으로 우측 전두엽에서 높은 EEG 신호가 측정되었으며, 낮은 쾌감성 자극(중립과 공포)은 왼쪽 전두엽에서 측정되었다. 또한 가장 큰 세타파의 변화가 전두엽의 중앙에서 발생되었다. 알파파에서 행복한 청각자극에 가장 강한 신호가 전두엽 전체에서 관찰되었다. 이 결과들은 기존의 감정들과 일치되며, 세타파와 알파파가 감정처리에서 중요한 역할을 하고 있음을 시사한다. The correlations between electroencephalographic (EEG) spectral power and emotional responses during affective sound clip listening are important parameters. Hemispheric asymmetry in prefrontal activation have been proposed in two decades ago, as measured by power value, is related to reactivity to affectively pleasure audio stimuli. In this study, we designed an emotional audio stimulus experiment in order to verify frontal EEG asymmetry by analyzing Event-related Spectral Perturbation (ERSP) results. Thirty healthy college male students volunteered the stimulus experiment with the standard IADS(International Affective Digital Sounds) clips. These affective sound clips are classified in three emotion states, high pleasure-high arousal (happy), middle pleasure-low arousal (neutral) and low pleasure-high arousal (fear). The analysis of the data was performed in both theta (4-8Hz) and alpha (8-13Hz) bands. ERSP maps in the alpha band revealed that there are the stronger power responses of high pleasure (happy) in the right frontal lobe, while the stronger power responses of middle-low pleasure (neutral and fear) in the left frontal lobe. Moreover, ERSP maps in the theta band revealed that there are the stronger power responses of high arousal (fear and happy) in the left pre-frontal lobe, while the stronger responses of low arousal (neutral) in the right pre-frontal lobe. However, the high pleasure emotions (happy) can elicit greater relative right EEG activity, while the low and middle pleasure emotions (fear and neutral) can elicit the greater relative left EEG activity. Additionally, the most differences of theta band have been found out in the medial frontal lobe, which is proved as the frontal midline theta. And there are the strongest responses of happy sounds in the alpha band around the whole frontal regions. These results are well suited for emotion recognition, and provide the evidences that theta and alpha powers may have the more important role in the emotion processing than previously believed.

The temporal dynamics of visual working memory guidance of selective attention.

The biased competition model proposes that there is top-down directing of attention to a stimulus matching the contents of working memory (WM), even when the maintenance of a WM representation is detrimental to target relevant performance. Despite many studies elucidating that spatial WM guidance can be present early in the visual processing system, whether visual WM guidance also influences perceptual selection remains poorly understood. Here, we investigated the electrophysiological correlates of early guidance of attention by WM in humans. Participants were required to perform a visual search task while concurrently maintaining object representations in their visual WM. Behavioral results showed that response times (RTs) were longer when the distractor in the visual search task was held in WM. The earliest WM guidance effect was observed in the P1 component (90–130 ms), with match trials eliciting larger P1 amplitude than mismatch trials. A similar result was also found in the N1 component (160–200 ms). These P1 and N1 effects could not be attributed to bottom-up perceptual priming from the presentation of a memory cue, because there was no significant difference in early event-related potential (ERP) component when the cue was merely perceptually identified but not actively held in WM. Standardized Low Resolution Electrical Tomography Analysis (sLORETA) showed that the early WM guidance occurred in the occipital lobe and the N1-related activation occurred in the parietal gyrus. Time-frequency data suggested that alpha-band event-related spectral perturbation (ERSP) magnitudes increased under the match condition compared with the mismatch condition only when the cue was held in WM. In conclusion, the present study suggests that the reappearance of a stimulus held in WM enhanced activity in the occipital area. Subsequently, this initial capture of attention by WM could be inhibited by competing visual inputs through attention re-orientation, reflecting by the alpha-band rhythm.

Neural rhythmic symphony of human walking observation: Upside-down and Uncoordinated condition on cortical theta, alpha, beta and gamma oscillations.

Biological motion observation has been recognized to produce dynamic change in sensorimotor activation according to the observed kinematics. Physical plausibility of the spatial-kinematic relationship of human movement may play a major role in the top-down processing of human motion recognition. Here, we investigated the time course of scalp activation during observation of human gait in order to extract and use it on future integrated brain-computer interface using virtual reality (VR). We analyzed event related potentials (ERP), the event related spectral perturbation (ERSP) and the inter-trial coherence (ITC) from high-density EEG recording during video display onset (−200–600 ms) and the steady state visual evoked potentials (SSVEP) inside the video of human walking 3D-animation in three conditions: Normal; Upside-down (inverted images); and Uncoordinated (pseudo-randomly mixed images). We found that early visual evoked response P120 was decreased in Upside-down condition. The N170 and P300b amplitudes were decreased in Uncoordinated condition. In Upside-down and Uncoordinated conditions, we found decreased alpha power and theta phase-locking. As regards gamma oscillation, power was increased during the Upside-down animation and decreased during the Uncoordinated animation. An SSVEP-like response oscillating at about 10 Hz was also described showing that the oscillating pattern is enhanced 300 ms after the heel strike event only in the Normal but not in the Upside-down condition. Our results are consistent with most of previous point-light display studies, further supporting possible use of virtual reality for neurofeedback applications.

Delay differential analysis of electroencephalographic data.

We propose a time-domain approach to detect frequencies, frequency couplings, and phases using nonlinear correlation functions. For frequency analysis, this approach is a multivariate extension of discrete Fourier transform, and for higher-order spectra, it is a linear and multivariate alternative to multidimensional fast Fourier transform of multidimensional correlations. This method can be applied to short and sparse time series and can be extended to cross-trial and cross-channel spectra (CTS) for electroencephalography data where multiple short data segments from multiple trials of the same experiment are available. There are two versions of CTS. The first one assumes some phase coherency across the trials, while the second one is independent of phase coherency. We demonstrate that the phase-dependent version is more consistent with event-related spectral perturbation analysis and traditional Morlet wavelet analysis. We show that CTS can be applied to short data windows and yields higher temporal resolution than traditional Morlet wavelet analysis. Furthermore, the CTS can be used to reconstruct the event-related potential using all linear components of the CTS.

Sensory modality-specific spatio-temporal dynamics in response to counting tasks

From perception to behavior, the human brain processes information in a flexible and abstract manner independent of an input sensory modality. However, the mechanism of such multisensory neural information processing in the brain remains under debate. Relatedly, studies often aim to investigate whether certain brain regions behave in a modality-specific manner or invariantly. Previous studies regarding multisensory information processing have commonly reported only on the activation of brain regions in response to unimodal or multimodal sensory stimuli. However, less attention has been given to the modality effect on the dynamics of such regions, which could advance our understanding of neuronal information processing. In this study, we investigated whether brain regions show modality-specific or invariant high-temporal dynamics. Electrocardiogram (EEG) was recorded from healthy, normal subjects during beep-, flash- and click-counting tasks, which corresponded to auditory, visual and tactile modalities, respectively. EEG dynamics regarding event-related spectral perturbations (ERSP) in ICA time-series data were compared across the sensory modalities using a multivariate pattern analysis. We found modality-specific EEG dynamics in the prefrontal cortex, whereas we found modality-specific and cross-modal dynamics in the early visual cortex.

Late, not early mismatch responses to changes in frequency are reduced or deviant in children with dyslexia: an event-related potential study.

BackgroundDevelopmental disorders of oral and written language have been linked to deficits in the processing of auditory information. However, findings have been inconsistent, both for behavioural and electrophysiological measures.MethodsIn this study, we examined event-related potentials (ERPs) in 20 6- to 14-year-old children with developmental dyslexia and 20 age-matched controls, divided into younger (6–11 years, n = 10) and older (11–14 years, n = 10) age bands. We focused on early (mismatch negativity; MMN) and late (late discriminative negativity; LDN) conventional mismatch responses and associated measures derived from time-frequency analysis (inter-trial coherence and event-related spectral perturbation). Responses were elicited using an auditory oddball task, whereby a stream of 1000-Hz standards was interspersed with rare large (1,200 Hz) and small (1,030 Hz) frequency deviants.ResultsConventional analyses revealed no significant differences between groups in the size of the MMN to either large or small frequency deviants. However, the younger age band of children with dyslexia showed an enhanced inter-trial coherence in the theta frequency band over the time window corresponding to the MMN to small deviants. By contrast, these same children showed a reduced-amplitude LDN for the small deviants relative to their age-matched controls, whilst the older children with dyslexia showed a shorter and less intense period of event-related desynchronization over this time window.ConclusionsInitial detection and discrimination of auditory frequency change appears normal or even enhanced in children with dyslexia. Rather, deficits in late-stage auditory processing appear to be a feature of this population.

Temporal dynamics of sensorimotor integration in speech perception and production: independent component analysis of EEG data.

Activity in anterior sensorimotor regions is found in speech production and some perception tasks. Yet, how sensorimotor integration supports these functions is unclear due to a lack of data examining the timing of activity from these regions. Beta (~20 Hz) and alpha (~10 Hz) spectral power within the EEG μ rhythm are considered indices of motor and somatosensory activity, respectively. In the current study, perception conditions required discrimination (same/different) of syllables pairs (/ba/ and /da/) in quiet and noisy conditions. Production conditions required covert and overt syllable productions and overt word production. Independent component analysis was performed on EEG data obtained during these conditions to (1) identify clusters of μ components common to all conditions and (2) examine real-time event-related spectral perturbations (ERSP) within alpha and beta bands. 17 and 15 out of 20 participants produced left and right μ-components, respectively, localized to precentral gyri. Discrimination conditions were characterized by significant (pFDR < 0.05) early alpha event-related synchronization (ERS) prior to and during stimulus presentation and later alpha event-related desynchronization (ERD) following stimulus offset. Beta ERD began early and gained strength across time. Differences were found between quiet and noisy discrimination conditions. Both overt syllable and word productions yielded similar alpha/beta ERD that began prior to production and was strongest during muscle activity. Findings during covert production were weaker than during overt production. One explanation for these findings is that μ-beta ERD indexes early predictive coding (e.g., internal modeling) and/or overt and covert attentional/motor processes. μ-alpha ERS may index inhibitory input to the premotor cortex from sensory regions prior to and during discrimination, while μ-alpha ERD may index sensory feedback during speech rehearsal and production.

Oscillation encoding of individual differences in speech perception.

Individual differences in second language (L2) phoneme perception (within the normal population) have been related to speech perception abilities, also observed in the native language, in studies assessing the electrophysiological response mismatch negativity (MMN). Here, we investigate the brain oscillatory dynamics in the theta band, the spectral correlate of the MMN, that underpin success in phoneme learning. Using previous data obtained in an MMN paradigm, the dynamics of cortical oscillations while perceiving native and unknown phonemes and nonlinguistic stimuli were studied in two groups of participants classified as good and poor perceivers (GPs and PPs), according to their L2 phoneme discrimination abilities. The results showed that for GPs, as compared to PPs, processing of a native phoneme change produced a significant increase in theta power. Stimulus time-locked analysis event-related spectral perturbation (ERSP) showed differences for the theta band within the MMN time window (between 70 and 240 ms) for the native deviant phoneme. No other significant difference between the two groups was observed for the other phoneme or nonlinguistic stimuli. The dynamic patterns in the theta-band may reflect early automatic change detection for familiar speech sounds in the brain. The behavioral differences between the two groups may reflect individual variations in activating brain circuits at a perceptual level.

Neural correlates of apparent motion perception of impoverished facial stimuli: A comparison of ERP and ERSP activity

Our brains readily decode human movements, as shown by neural responses to face and body motion. N170 event-related potentials (ERPs) are earlier and larger to mouth opening movements relative to closing in both line-drawn and natural faces, and gaze aversions relative to direct gaze in natural faces (Puce and Perrett, 2003; Puce et al., 2000). Here we extended this work by recording both ERP and oscillatory EEG activity (event-related spectral perturbations, ERSPs) to line-drawn faces depicting eye and mouth movements (Eyes: Direct vs Away; Mouth: Closed vs Open) and non-face motion controls. Neural activity was measured in 2 occipito-temporal clusters of 9 electrodes, one in each hemisphere. Mouth opening generated larger N170s than mouth closing, replicating earlier work. Eye motion elicited robust N170s that did not differ between gaze conditions. Control condition differences were seen, and generated the largest N170. ERSP difference plots across conditions in the occipito-temporal electrode clusters (Eyes: Direct vs Away; Mouth: Closed vs Open) showed statistically significant differences in beta and gamma bands for gaze direction changes and mouth opening at similar post-stimulus times and frequencies. In contrast, control stimuli showed activity in the gamma band with a completely different time profile and hemispheric distribution to facial stimuli.ERSP plots were generated in two 9 electrode clusters centered on central sites, C3 and C4. In the left cluster for all stimulus conditions, broadband beta suppression persisted from about 250ms post-motion onset. In the right cluster, beta suppression was seen for control conditions only. Statistically significant differences between conditions were confined between 4 and 15Hz, unlike the occipito-temporal sites where differences occurred at much higher frequencies (high beta/gamma).Our data indicate that N170 amplitude is sensitive to the amount of movement in the visual field, independent of stimulus type. In contrast, occipito-temporal beta and gamma activity differentiates between facial and non-facial motion. Context and stimulus configuration likely plays a role in shaping neural responses, based on comparisons of the current data to previously reported studies. Broadband suppression of central beta activity, and significant low frequency differences were likely stimulus driven and not contingent on behavioral responses.

Modulation of the N30 generators of the somatosensory evoked potentials by the mirror neuron system

The N30 component of the somatosensory evoked potential is known to be modulated by sensory interference, motor action, movement ideation and observation. We introduce a new paradigm in which the observation task of another person's hand movement triggers the somatosensory stimulus, inducing the N30 response in participants. In order to identify the possible contribution of the mirror neuron network (MNN) to this early sensorimotor processing, we analyzed the N30 topography, the event-related spectral perturbation and the inter-trial coherence on single electroencephalogram (EEG) trials, and we applied swLORETA to localize the N30 sources implicated in the time–frequency domain at rest and during observation, as well as the generators differentiating these two contextual brain states. We found that N30 amplitude increase correlated with increased contralateral precentral alpha, frontal beta, and contralateral frontal gamma power spectrum, and with central and precentral alpha and parietal beta phase-locking of ongoing EEG signals. We demonstrate specific activation of the contralateral post-central and parietal cortex where the angular gyrus (BA39), an important MNN node, is implicated in this enhancement during observation. We conclude that this part of the MNN, involved in proprioceptive processing and more complex body-action representations, is already active prior to somatosensory input and may enhance N30.

Linking brain electrical signals elicited by current outcomes with future risk decision-making

The experience of current outcomes influences future decisions in various ways. The neural mechanism of this phenomenon may help to clarify the determinants of decision-making. In this study, thirty-nine young adults finished a risky gambling task by choosing between a high- and a low-risk option in each trial during electroencephalographic data collection. We found that risk-taking strategies significantly modulated mean amplitudes of the event-related potential (ERP) component P3, particularly at the central scalp. The event-related spectral perturbation and the inter-trial coherence measurements of the independent component analysis (ICA) data indicated that the “stay” vs. “switch” electrophysiological difference associated with subsequent decision-making was mainly due to fronto-central theta and left/right mu independent components. Event-related cross-coherence results suggested that the neural information of action monitoring and updating emerged in the fronto-central cortex and propagated to sensorimotor area for further behavior adjustment. Based on these findings of ERP and event-related oscillation (ERO) measures, we propose a neural model of the influence of current outcomes on future decisions.

A new approach for utilisation of single ERP to control multiple commands in BCI

Decomposed Event Related Potential (ERP) analysis-based concept is proposed in order to increase the control commands corresponding to single ERP in Brain Computer Interface (BCI). Hypothesis based on analysis of Event-Related Spectral Perturbation (ERSP) is generalised with decomposed ERPs, and culminative power is estimated as features of decomposed ERPs.

Event-related theta synchronization predicts deficit in facial affect recognition in schizophrenia.

Growing evidence suggests that abnormalities in the synchronized oscillatory activity of neurons in schizophrenia may lead to impaired neural activation and temporal coding and thus lead to neurocognitive dysfunctions, such as deficits in facial affect recognition. To gain an insight into the neurobiological processes linked to facial affect recognition, we investigated both induced and evoked oscillatory activity by calculating the Event Related Spectral Perturbation (ERSP) and the Inter Trial Coherence (ITC) during facial affect recognition. Fearful and neutral faces as well as nonface patches were presented to 24 patients with schizophrenia and 24 matched healthy controls while EEG was recorded. The participants' task was to recognize facial expressions. Because previous findings with healthy controls showed that facial feature decoding was associated primarily with oscillatory activity in the theta band, we analyzed ERSP and ITC in this frequency band in the time interval of 140-200 ms, which corresponds to the N170 component. Event-related theta activity and phase-locking to facial expressions, but not to nonface patches, predicted emotion recognition performance in both controls and patients. Event-related changes in theta amplitude and phase-locking were found to be significantly weaker in patients compared with healthy controls, which is in line with previous investigations showing decreased neural synchronization in the low frequency bands in patients with schizophrenia. Neural synchrony is thought to underlie distributed information processing. Our results indicate a less effective functioning in the recognition process of facial features, which may contribute to a less effective social cognition in schizophrenia.

Abnormal Oscillatory Neural Coupling in Children with Language-Learning Problems and Auditory Processing Disorder

Children with language-learning problems (LLP) often demonstrate auditory processing deficits on tasks using nonlinguistic stimuli, which may indicate an underlying auditory processing disorder (APD) that leads to delayed language skills. However, recent studies of event-related potentials provide evidence that APD is the result of, rather than the cause of, language impairments in children with LLP. To further address these conflicting accounts, we examined event-related spectral perturbations (ERSPs) in 14 children with LLP and in 14 age-matched, normal hearing controls. ERSPs were computed from electroencephalogram (EEG) responses to nonlinguistic speech sounds in two different stimulus rate conditions. Results revealed that children with LLP have abnormal shifts in the characteristic operating frequencies (COFs) and phase-amplitude coupling of the alpha and beta EEG bands. Further, children with LLP show multiple COFs in the beta EEG band, which are not present in normal-hearing controls. These results suggest that insufficient oscillatory neural coupling may underlie the APD and language deficits present in children with LLP and might further be explained by interhemispheric asymmetries in this population.

Concurrent working memory task decreases the Stroop interference effect as indexed by the decreased theta oscillations

Working memory (WM) tasks may increase or decrease the interference effect of concurrently performed cognitive control tasks. However, the neural oscillatory correlates of this modulation effect of WM on the Stroop task are still largely unknown. In the present study, behavioral and electroencephalographic (EEG) data were recorded from 32 healthy participants during their performance of the single Stroop task and the same task with a concurrent WM task. We observed that the Stroop interference effect represented in both response times (RTs) and theta-band event-related spectral perturbation (ERSP) magnitude reduced under the dual-task condition compared with the single-task condition. The reduction of interference in theta-band ERSP was further positively correlated with interference reduction in RTs, and was mainly explained by the source in the left middle frontal gyrus. In conclusion, the present study suggests that the effect of concurrent WM tasks on the reduction of the Stroop interference effect can be indexed by EEG oscillations in theta-band rhythm in the centro-frontal regions and this modulation was mediated by the reduced cognitive control under the concurrent WM task.

Gravity Influences Top-Down Signals in Visual Processing

Visual perception is not only based on incoming visual signals but also on information about a multimodal reference frame that incorporates vestibulo-proprioceptive input and motor signals. In addition, top-down modulation of visual processing has previously been demonstrated during cognitive operations including selective attention and working memory tasks. In the absence of a stable gravitational reference, the updating of salient stimuli becomes crucial for successful visuo-spatial behavior by humans in weightlessness. Here we found that visually-evoked potentials triggered by the image of a tunnel just prior to an impending 3D movement in a virtual navigation task were altered in weightlessness aboard the International Space Station, while those evoked by a classical 2D-checkerboard were not. Specifically, the analysis of event-related spectral perturbations and inter-trial phase coherency of these EEG signals recorded in the frontal and occipital areas showed that phase-locking of theta-alpha oscillations was suppressed in weightlessness, but only for the 3D tunnel image. Moreover, analysis of the phase of the coherency demonstrated the existence on Earth of a directional flux in the EEG signals from the frontal to the occipital areas mediating a top-down modulation during the presentation of the image of the 3D tunnel. In weightlessness, this fronto-occipital, top-down control was transformed into a diverging flux from the central areas toward the frontal and occipital areas. These results demonstrate that gravity-related sensory inputs modulate primary visual areas depending on the affordances of the visual scene.