Alpha Event-related Synchronization Research Articles

Theta and alpha activity are differentially associated with physiological and rating scale measures of affective processing in adolescents with but not without ADHD.

Although atypical theta and alpha activity may be biomarkers of attention-deficit/hyperactivity disorder (ADHD) outcomes such as atypical affective processing and attention, the exact nature of the relations of these characteristics is unknown. We examined in age- and sex-matched adolescents (N = 132; Mage = 14.944, years, SD = .802) with and without ADHD, whether resting state (RS) theta and alpha power or theta and alpha event-related synchronization (ERS) during affect regulation (1) differ between adolescents with and without ADHD; (2) are differentially associated with event-related potential (ERP) and parent- and self-report measures of affective processing and inattention, given ADHD status and sex, and (3) are differentially lateralized, given ADHD status and sex. Adolescents with ADHD exhibited lower RS frontal-midline alpha power than adolescents without ADHD. In adolescents with ADHD, right parietal theta ERS was positively associated with the ERP measure of elaborate affective/motivational processing and right parietal RS alpha power was negatively associated with self-reported positive affectivity. In adolescents without ADHD, associations were nonsignificant. There was no disassociation of theta and alpha activity with affective processing and inattention. Consistent with clinical impressions, the between-group difference in frontal-midline theta ERS was more marked in boys than girls.

Alpha Oscillations During Effortful Continuous Speech: From Scalp EEG to Ear-EEG.

The purpose of this study was to investigate alpha power as an objective measure of effortful listening in continuous speech with scalp and ear-EEG. Scalp and ear-EEG were recorded simultaneously during presentation of a 33-s news clip in the presence of 16-talker babble noise. Four different signal-to-noise ratios (SNRs) were used to manipulate task demand. The effects of changes in SNR were investigated on alpha event-related synchronization (ERS) and desynchronization (ERD). Alpha activity was extracted from scalp EEG using different referencing methods (common average and symmetrical bi-polar) in different regions of the brain (parietal and temporal) and ear-EEG. Alpha ERS decreased with decreasing SNR (i.e., increasing task demand) in both scalp and ear-EEG. Alpha ERS was also positively correlated to behavioural performance which was based on the questions regarding the contents of the speech. Alpha ERS/ERD is better suited to track performance of a continuous speech than listening effort. EEG alpha power in continuous speech may indicate of how well the speech was perceived and it can be measured with both scalp and Ear-EEG.

Time-frequency neural dynamics of ADHD children and adolescents during a Working Memory task

The present report analyzed the time-frequency changes in Event-Related Spectral perturbations (ERSP) in a sample of ADHD children and adolescents compared to a normodevelopment (ND) sample. A delayed match-to-sample (DMTS) test of working memory (WM) was presented to a group of ADHD subjects (N = 29) and compared with ND group (N = 34) with ages between 6 and 17 years old. Time-frequency decomposition was computed through wavelets. ADHD subjects presented higher Reaction Time (RT), Standard Deviation of RT (Std of RT), and a reduced percentage of correct responses. The results showed a complex pattern of oscillatory bursts during the encoding, maintenance, and recognition phases with similar dynamics in both groups. ADHD children presented a reduced Event-Related Synchronization (ERS) in the Theta range during the encoding phase, and also a reduced Alpha ERS during the late period of the maintenance phase. S1 Early theta ERS was positively correlated with Std of RT. Behavioral data, early Theta, and late Alpha ERS classified correctly above 70 % of ADHD and ND subjects when a linear discriminant analysis was applied. The reduced encoding and maintenance impaired brain dynamics of ADHD subjects would justify the poorer performance of this group of subjects.

Assessing the Longitudinal Relationship between Theta-Gamma Coupling and Working Memory Performance in Older Adults.

Theta-gamma coupling (TGC) is a neurophysiologic mechanism that supports working memory (WM). TGC is associated with N-back performance, a WM task. Similar to TGC, theta and alpha event-related synchronization (ERS) and desynchronization (ERD) are also associated with WM. Few studies have examined the longitudinal relationship between WM performance and TGC, ERS, or ERD. This study aimed to determine if changes in WM performance are associated with changes in TGC (primary aim), as well as theta and alpha ERS or ERD over 6 to 12 weeks. Participants included 62 individuals aged 60 and older with no neuropsychiatric conditions or with remitted Major Depressive Disorder (MDD) and no cognitive disorders. TGC, ERS, and ERD were assessed using electroencephalography (EEG) during the N-back task (3-back condition). There was an association between changes in 3-back performance and changes in TGC, alpha ERD and ERS, and theta ERS in the control group. In contrast, there was only a significant association between changes in 3-back performance and changes in TGC in the subgroup with remitted MDD. Our results suggest that the relationship between WM performance and TGC is stable over time, while this is not the case for changes in theta and alpha ERS and ERD.

Experience Affects EEG Event-Related Synchronization in Dancers and Non-dancers While Listening to Preferred Music.

EEGs were analyzed to investigate the effect of experiences in listening to preferred music in dancers and non-dancers. Participants passively listened to instrumental music of their preferred genre for 2 min (Argentine tango for dancers, classical, or jazz for non-dancers), alternate genres, and silence. Both groups showed increased activity for their preferred music compared to non-preferred music in the gamma, beta, and alpha frequency bands. The results suggest all participants' conscious recognition of and affective responses to their familiar music (gamma), appreciation of the tempo embedded in their preferred music and emotional arousal (beta), and enhanced attention mechanism for cognitive operations such as memory retrieval (alpha). The observed alpha activity is considered in the framework of the alpha functional inhibition hypothesis, in that years of experience listening to their favorite type of music may have honed the cerebral responses to achieve efficient cortical processes. Analyses of the electroencephalogram (EEG) activity over 100s-long music pieces revealed a difference between dancers and non-dancers in the magnitude of an initial alpha event-related desynchronization (ERD) and the later development of an alpha event-related synchronization (ERS) for their preferred music. Dancers exhibited augmented alpha ERD, as well as augmented and uninterrupted alpha ERS over the remaining 80s. This augmentation in dancers is hypothesized to be derived from creative cognition or motor imagery operations developed through their dance experiences.

α-tACS over the somatosensory cortex enhances tactile spatial discrimination in healthy subjects with low alpha activity.

IntroductionSpontaneous oscillations in the somatosensory cortex, especially of the alpha (8 − 14 Hz) and gamma (60 − 80 Hz) frequencies, affect tactile perception; moreover, these oscillations can be selectively modulated by frequency‐matched transcranial alternating current stimulation (tACS) on the basis of ongoing oscillatory brain activity. To examine whether tACS can actually improve tactile perception via alpha and gamma modulation, we measured the effects of 10‐Hz and 70‐Hz tACS (α‐ and γ‐tACS) on the left somatosensory cortex on right‐finger tactile spatial orientation discrimination, and the associations between performance changes and individual alpha and gamma activities.MethodsFifteen neurologically healthy subjects were recruited into this study. Electroencephalography (EEG) was performed before the first day, to assess the normal alpha‐ and gamma‐activity levels. A grating orientation discrimination task was performed before and during 10‐Hz and 70‐Hz tACS.ResultsThe 10‐Hz tACS protocol decreased the grating orientation discrimination threshold, primarily in subjects with low alpha event‐related synchronization (ERS). In contrast, the 70‐Hz tACS had no effect on the grating orientation discrimination threshold.ConclusionsThis study showed that 10‐Hz tACS can improve tactile orientation discrimination in subjects with low alpha activity. Alpha‐frequency tACS may help identify the contributions of these oscillations to other neurophysiological and pathological processes.

Neurophysiological Correlates of Gait Retraining With Real-Time Visual and Auditory Feedback.

Most people acquire motor skills through feedback-based training. How the human brain processes sensory feedbacks during training, especially in a gait training, remain largely unclear. The purpose of this paper is to explore how humans adopt a new gait pattern to reduce impacts during walking-with the aid of visual and audio feedbacks. This paper demonstrates the features of underlying brain activity in incorporating the visual or auditory cues to acquire a new gait pattern. Electroencephalography (EEG) and peak positive acceleration (PPA) of the heel were collected from 23 participants during walking on a treadmill with no feedback, with visual feedback, or with audio feedback. The feedbacks were presented after each foot strike, where a sub-threshold PPA triggered a positive feedback (green/low-pitched), and a suprathreshold PPA triggered a negative feedback (red/high-pitched). The participants were instructed to voluntarily control their gait, so that low PPA could be achieved. This control was perturbed in some sessions by an additional cognitive task, and the influence of such distraction was also explored. The PPA was significantly lower in the sessions with visual or audio feedback than in sessions without feedback, showing an immediate improvement in gait pattern, when the feedback was provided. Different feedbacks modulated neural activities at different locations and/or levels during training. Alpha event-related synchronization (ERS) was particularly increased during the encoding of auditory feedback or the introduction of a distracting task. In the meantime, prominent frontal and posterior theta ERS were coupled with negative feedback, and strong beta event-related desynchronization (ERD) was observed only in sessions with feedbacks. Our results indicate that feedback effectively enhances motor planning when acquiring a new gait.

Decreased Event-Related Beta Synchronization During Memory Maintenance Marks Early Cognitive Decline in Mild Cognitive Impairment.

Mild cognitive impairment (MCI) refers to a measurable deficit in cognition in the absence of dementia or impairment in activities of daily living. Working memory impairment is among the earliest signs of MCI. Oscillatory analysis of working memory might be a potential tool for identifying patients at increased risk of developing dementia. Our study aimed to assess the temporospatial pattern of spectral differences during working memory maintenance between MCI patients and healthy controls and to compare the sources of oscillatory activity between the two groups. Event-related spectral perturbation of 17 MCI patients and 21 healthy control participants was studied with 128-channel EEG during the Sternberg working memory task. Source localization was performed by using the eLORETA software. Among the participants, 13 MCI and 15 control participants underwent a structural brain MRI examination. Event-related synchronization (ERS) in the alpha and beta frequency band was significantly lower in MCI patients compared to healthy control participants during retention. Both study groups showed significant memory load-related enhancement in both frequency band. In the MCI group, source localization revealed significantly attenuated beta oscillatory activity in the inferior and middle temporal gyrus, in the fusiform gyrus, and in the cuneus. Beta ERS correlated significantly with the size of the hippocampus, entorhinal cortex, and parahippocampal gyrus. During the retention period, MCI is characterized by decreased alpha and beta ERS compared to controls indicating early impairment in neural networks serving working memory maintenance. The assessment of electrophysiological changes in the beta frequency range may provide a useful diagnostic tool for the early detection of cognitive impairment.

Alpha event-related synchronization after eye closing differs in Alzheimer's disease and dementia with Lewy bodies: a magnetoencephalography study.

The electroencephalography (EEG) abnormalities found in patients with dementia with Lewy bodies (DLB) are conflicting. In this study, we used magnetoencephalography, which has higher spatial resolution than electroencephalography, to explore neurophysiological features of DLB that may aid in the differential diagnosis. Six patients with DLB, 11 patients with Alzheimer's disease, and 11 age-matched normal subjects were recruited. We investigated alterations in the ratio of event-related synchronization (ERS) in the alpha band after eye-closing. Although the averaged ratio change of alpha ERS after eye-closing appeared predominantly in the posterior brain regions in all study groups, DLB patients had the weakest ratio change of alpha ERS. In particular, DLB patients exhibited a significantly reduced ratio change of alpha ERS in the bilateral inferior temporal gyrus, right occipital pole, and left parieto-occipital cortex compared to Alzheimer's disease patients or normal controls. Our findings indicated that a reduced ratio change of alpha ERS in the posterior brain regions elicited by eye-closing is a brain electromagnetic feature of DLB.

Brain responses to auditory oddball task in children with benign childhood epilepsy with centrotemporal spikes: Quantitative analysis and correlation with neuropsychological assessment scores

ObjectiveVariable degrees of cognitive dysfunction have been reported in children with benign childhood epilepsy with centrotemporal spikes (BCECTS). Our aim was to perform quantitative analyses of the brain responses to cognitive tasks using event-related desynchronization (ERD) and event-related synchronization (ERS) and correlating the results with the scores of neuropsychological tests in patients with BCECTS. MethodsThis case control study included 30 patients with BCECTS and 20 controls. Clinical assessment, neuropsychological tests, the Positive wave at 300 msec (P300) parameters recording, and quantitative electroencephalography (EEG) analysis were carried out for both groups. Alpha power ERD and ERS were measured in six different brain regions during an auditory oddball paradigm. ResultsChildren with epilepsy showed a statistically significant poorer performance in verbal intelligence quotient (IQ), performance IQ, and total scale IQ and lower number of correct responses. Moreover, both groups showed diffuse alpha power attenuation in response to the target tones. After summation of the alpha power ERD over all brain regions to get the net diffuse ERD, the patients' group showed a statistically significant smaller net alpha ERD compared with that of the control group (P=0.001). No significant correlations between the alpha ERD percentage, recorded P300 parameters, and neuropsychological tests scores were found. ConclusionsChildren with BCECTS have subtle cognitive dysfunction proved by significantly lower scores of verbal IQ and performance IQ subtests. The significantly smaller net diffuse alpha power ERD detected in children with epilepsy may be an electrophysiological indicator of disruptive brain activation in relation to cognitive attentional tasks; however, its correlation with neuropsychological tests was insignificant.

EEG Dynamics and Neural Generators in Implicit Navigational Image Processing in Adults with ADHD

In contrast to childhood ADHD that is characterized by inattention, impulsivity and hyperactivity, most adults with ADHD predominantly exhibit inattention. We used a new oddball paradigm using implicit navigational images and analyzed EEG dynamics with swLORETA inverse modeling of the evoked potential generators to study cortical processing in adults with ADHD and age-matched controls. In passive observation, we demonstrated that P350 amplitude, alpha–beta oscillation event-related synchronization (ERS) anticipation, and beta event-related desynchronization (ERD) were significantly smaller in ADHD. In the active condition, P100 duration was reduced and N140 amplitude increased for both deviant and frequent conditions in the ADHD. Alpha ERS and delta-theta ERS were reduced in the ADHD in the deviant condition. The left somatosensory area (BA2) and the right parietal lobe (BA31, BA40) contributed more to the P100 generators in the control than in the ADHD group, while the left frontal lobe (BA10) contributed more to the P100 generators in the ADHD. The left inferior parietal lobe (BA40) contributed more to the N140 generators in the control than the ADHD group while the right posterior cingulate (BA30) contributed more to the N140 generators in the ADHD. These findings reinforce the notion that earlier cortical stages of visual processing are compromised in adult ADHD by inducing the emergence of different even-related potential generators and EEG dynamics in ADHD. Considering that classical approaches for ADHD diagnosis are based on qualitative clinical investigation possibly biased by subjectivity, EEG analysis is another objective tool that might contribute to diagnosis, future neurofeedback or brain stimulation therapies.

P379 Assessment of cognitive function in children with benign childhood epilepsy with centrotemporal spikes: An event related EEG desynchronization and synchronization study

Objective Quantitative analysis of brain responses to cognitive tasks using event related desynchronization (ERD) and event related synchronization (ERS) and correlation the results with scores of neuropsychological tests in patients with BCECTS. Methods Our study included 50 children (30 patients and 20 matched controls). Clinical assessment, Neuropsychological tests, Behavioral measures, P300 averaging and Quantitative EEG analysis were carried out for patients? and control groups, in addition to brain imaging for the patients. Alpha power ERD and ERS were measured as the percent decrease or increase in alpha power produced by target tones relative to reference intervals in six different brain regions during an auditory oddball paradigm. Results Epileptic children showed a statistically significant poorer cognitive performance in the neuropsychological and behavioral tests (verbal IQ, performance IQ, letter cancellation test and number of correct responses). Moreover, both groups showed diffuse alpha power attenuation in response to the target tones, however this alpha power ERD was significantly smaller in epileptic children compared to healthy group. No significant P300 wave latency or amplitude difference was elicited between both groups and no significant correlation between alpha ERD percentage and neuropsychological results. Conclusions Children with BCECTS have subtle cognitive dysfunction, particularly in the domains of language, memory, attention and executive functions. The smaller alpha power ERD in epileptic children may be an electrophysiological index of disruptive brain activation related to the cognitive dysfunction with BCECTS. However, alpha power ERD/ERS technique could be complementary rather than supplementary to neuropsychological testing in cognitive assessment of those children.

Auditory Target and Novelty Processing in Patients with Unilateral Hippocampal Sclerosis: A Current-Source Density Study

The capacity to respond to novel events is crucial for adapting to the constantly changing environment. Here, we recorded 29-channel Event Related Brain Potentials (ERPs) during an active auditory novelty oddball paradigm and used for the first time Current Source Density-transformed Event Related Brain Potentials and associated time-frequency spectra to study target and novelty processing in a group of epileptic patients with unilateral damage of the hippocampus (N = 18) and in healthy matched control participants (N = 18). Importantly, we used Voxel-Based Morphometry to ensure that our group of patients had a focal unilateral damage restricted to the hippocampus and especially its medial part. We found a clear deficit for target processing at the behavioral level. In addition, compared to controls, our group of patients presented (i) a reduction of theta event-related synchronization (ERS) for targets and (ii) a reduction and delayed P3a source accompanied by reduced theta and low-beta ERS and alpha event-related synchronization (ERD) for novel stimuli. These results suggest that the integrity of the hippocampus might be crucial for the functioning of the complex cortico-subcortical network involved in the detection of novel and target stimuli.

Cortical Alpha Oscillations Predict Speech Intelligibility.

Understanding speech in noise (SiN) is a complex task involving sensory encoding and cognitive resources including working memory and attention. Previous work has shown that brain oscillations, particularly alpha rhythms (8–12 Hz) play important roles in sensory processes involving working memory and attention. However, no previous study has examined brain oscillations during performance of a continuous speech perception test. The aim of this study was to measure cortical alpha during attentive listening in a commonly used SiN task (digits-in-noise, DiN) to better understand the neural processes associated with “top-down” cognitive processing in adverse listening environments. We recruited 14 normal hearing (NH) young adults. DiN speech reception threshold (SRT) was measured in an initial behavioral experiment. EEG activity was then collected: (i) while performing the DiN near SRT; and (ii) while attending to a silent, close-caption video during presentation of identical digit stimuli that the participant was instructed to ignore. Three main results were obtained: (1) during attentive (“active”) listening to the DiN, a number of distinct neural oscillations were observed (mainly alpha with some beta; 15–30 Hz). No oscillations were observed during attention to the video (“passive” listening); (2) overall, alpha event-related synchronization (ERS) of central/parietal sources were observed during active listening when data were grand averaged across all participants. In some participants, a smaller magnitude alpha event-related desynchronization (ERD), originating in temporal regions, was observed; and (3) when individual EEG trials were sorted according to correct and incorrect digit identification, the temporal alpha ERD was consistently greater on correctly identified trials. No such consistency was observed with the central/parietal alpha ERS. These data demonstrate that changes in alpha activity are specific to listening conditions. To our knowledge, this is the first report that shows almost no brain oscillatory changes during a passive task compared to an active task in any sensory modality. Temporal alpha ERD was related to correct digit identification.

Cardiorespiratory Fitness Is Associated with Executive Control in Late-Middle-Aged Adults: An Event-Related (De) Synchronization (ERD/ERS) Study.

The present study sought to determine whether cardiorespiratory fitness is associated with cognitive function in late-middle-aged adults from event-related desynchronization (ERD) and event-related synchronization (ERS) perspectives. Late-middle-aged adults were categorized into either the high-fitness group or the low-fitness group based on their estimated cardiorespiratory fitness values. The participants completed the Stroop Test, which is comprised of incongruent and neutral conditions, while the brain activities were recoded. The alpha ERD and ERS values based on the equation proposed by Pfurtscheller (1977) were further calculated. The results revealed that the adults with higher levels of cardiorespiratory fitness demonstrated superior Stroop performance, regardless of Stroop congruency. While these high-fitness adults had less positive upper alpha ERD values in the later epoch window compared to their lower-fitness counterparts, they had greater lower alpha ERD values in the early epoch window. Additionally, in the late epoch window, the high-fitness adults showed less positive lower alpha ERD values on neutral, but not incongruent condition, relative to their low-fitness counterparts. These findings suggest that cardiorespiratory fitness of the late-middle-aged adults is positively associated with cognitive functioning, especially the cognitive processes related to the inhibition of task-irrelevant information and those processes required the devotion of greater amounts of attentional resources to a given task.

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.

Timely event-related synchronization fading and phase de-locking and their defects in migraine

ObjectiveTo investigate the characteristics of event-related synchronization (ERS) fading and phase de-locking of alpha waves during passive auditory stimulation (PAS) in the migraine patients. MethodsThe subjects were 16 adult women with migraine and 16 normal controls. Electroencephalographic (EEG) data obtained during PAS with standard (SS) and deviant stimuli (DS) were used. Alpha ERS fading, the phase locking index (PLI) and de-locking index (DLI) were evaluated from the 10Hz complex Morlet wavelet components at 100ms (t100) and 300ms (t300) after PAS. ResultsAt t100, significant ERS was found with SS and DS in the migraineurs and controls (P=0.000). At t300 in the controls, ERS faded to zero for DS while in the migraineurs there was no fading for DS. In both groups the PLI for SS and DS was significantly reduced, i.e. de-locked, at t300 compared to t100 (P=0.000). In the migraineurs, the DLI for DS was significantly lower than in the controls (P=0.003). ConclusionThe alpha ERS fading and phase de-locking are defective in migraineurs during passive auditory cognitive processing. SignificanceThe defects in timely alpha ERS fading and in de-locking may play a role in the different attention processing in migraine patients.

Brain oscillation and connectivity during a chemistry visual working memory task

Many studies have reported that frontal theta and posterior alpha activities are associated with working memory tasks. However, fewer studies have focused on examining whether or not the frontal alpha or posterior theta can play a role in the working memory task. This study investigates electroencephalography (EEG) dynamics and connectivity among different brain regions' theta and alpha oscillations. The EEG was collected from undergraduate students (n=64) while they were performing a Sternberg-like working memory task involving chemistry concepts. The results showed that the frontal midline cluster exhibited sustained theta augmentation across the periods of stimulus presentations, maintenance, and probe presentation, suggesting that the frontal midline theta might associate with facilitating the central execute function to maintain information in the working memory. Study of the central parietal and the occipital clusters revealed a sequence of theta augmentation followed by alpha suppression at constant intervals after the onset of stimulus and probe presentations, suggesting that the posterior theta might be associated with sensory processing, theta gating, or stimulus selection. It further suggests that the posterior alpha event-related de-synchronization (ERD) might be linked to direct information flow into and out of the long-term memory (LTM) and precede stimulus recognition. An alternating phasic alpha event-related synchronization (ERS) and ERD following the 1st stimulus and probe presentations were observed at the occipital cluster, in which alpha ERS might be linked to the inhibition of irrelevant information.

Decreased alpha event-related synchronization in the left posterior temporal cortex in schizophrenia: A magnetoencephalography-beamformer study

Alpha rhythm is one of the most prominent electromagnetic changes in the brain, and electroencephalography (EEG) alpha reactivity disturbance may sometimes represent an early sign of cerebral dysfunction. Although magnetoencephalography (MEG) has a better spatial resolution than EEG, it has not extensively been used to explore alpha-power change deficits in schizophrenia as a possible neurophysiological marker of the disease. The purpose of this study was to use MEG to identify abnormalities in alpha synchronization induced by eye-closing in schizophrenia patients compared to healthy controls, and to investigate whether alpha reactivity deficits correlate with clinical features of the disorder. MEG data were recorded in 22 schizophrenia patients and 20 age- and gender-matched controls during eyes-open/eyes-closed resting states. Cortical sources of event-related synchronization (ERS) were estimated using multiple source beamformer, and BrainVoyager was used for statistic group analysis. A significant decrease in ERS in the upper alpha band (10–13 Hz) was found in the left posterior temporal region in schizophrenia patients relative to controls, and this activity showed correlation with visual memory scores. This upper alpha ERS deficit may indicate left temporal dysfunction and visual-information processing impairment in schizophrenia, and upon further confirmation it might represent a neurophysiological state marker of the disorder.

Age-related differences on event-related potentials and brain rhythm oscillations during working memory activation

Previous functional imaging studies have pointed to the compensatory recruitment of cortical circuits in old age in order to counterbalance the loss of neural efficiency and preserve cognitive performance. Recent electroencephalographic (EEG) analyses reported age-related deficits in the amplitude of an early positive-negative working memory (PN(wm)) component as well as changes in working memory (WM)-load related brain oscillations during the successful performance of the n-back task. To explore the age-related differences of EEG activation in the face of increasing WM demands, we assessed the PN(wm) component area, parietal alpha event-related synchronization (ERS) as well as frontal theta ERS in 32 young and 32 elderly healthy individuals who successfully performed a highly WM demanding 3-back task. PN(wm) area increased with higher memory loads (3- and 2-back > 0-back tasks) in younger subjects. Older subjects reached the maximal values for this EEG parameter during the less WM demanding 0-back task. They showed a rapid development of an alpha ERS that reached its maximal amplitude at around 800 ms after stimulus onset. In younger subjects, the late alpha ERS occurred between 1,200 and 2,000 ms and its amplitude was significantly higher compared with elders. Frontal theta ERS culmination peak decreased in a task-independent manner in older compared with younger cases. Only in younger individuals, there was a significant decrease in the phasic frontal theta ERS amplitude in the 2- and 3-back tasks compared with the detection and 0-back tasks. These observations suggest that older adults display a rapid mobilization of their neural generators within the parietal cortex to manage very low demanding WM tasks. Moreover, they are less able to activate frontal theta generators during attentional tasks compared with younger persons.