Alpha Rhythm

The development of an innovative functional assessment procedure based on the combination of electroencephalography (EEG) and robot-assisted upper limb devices may provide new insights into the dynamics of cortical reorganization promoted by rehabilitation. The aim of this study was to evaluate changes in event-related synchronization/desynchronization (ERS/ERD) in alpha and beta bands in a patient with pure sensory stroke who underwent a specific rehabilitation program for somatic sensation recovery. A 49-year-old, right-handed woman (time since stroke, 12 months) with severe upper limb somatic sensation deficits was tested using validated clinical scales and a standardized video-EEG system combined with the Bi-Manu-Track robotassisted arm trainer protocol. The patient underwent a 3-month home-based rehabilitation program for promoting upper limb recovery (1 hour a day for 5 days a week). She was tested before treatment, at 1-month, and at 3-month during treatment. Results showed progressive recovery of upper limb function over time. These effects were associated with specific changes in the modulation of alpha and beta event-related synchronization/desynchronization. This unique study provides new perspectives for the assessment of functional deficits and changes in cortical activity promoted by rehabilitation in poststroke patients.

Two questions were addressed in the present study: (1) Do autistic and normally developing children exhibit regionally specific differences in electroencephalographic (EEG) activity? (2) Do subgroups of autistic children classified according to Wing and Gould's (1979) system which emphasizes degree of social impairment exhibit distinct patterns of EEG activity? Twenty-eight children with autism (5 to 18 years of age) and two groups of normally developing children (one matched on chronological age and the other on receptive language level) participated. EEG was recorded from left and right frontal, temporal, and parietal regions during an alert baseline condition. Compared to normally developing children, autistic children exhibited reduced EEG power in the frontal and temporal regions, but not in the parietal region. Differences were more prominent in the left than the right hemisphere. Furthermore, subgroups of autistic children based on Wing and Gould's system displayed distinct patterns of brain activity. Compared to autistic children classified as “active-but-odd,” “passive” autistic children displayed reduced alpha EEG power in the frontal region.

The alpha rhythm in the EEG is 8-12 Hz activity present when a subject is awake with eyes closed. In this study, we used simultaneous EEG and fMRI to make maps of regions whose MRI signal changed reliably with modulation in posterior alpha activity. We scanned 11 subjects as they rested with eyes closed. We found that increased alpha power was correlated with decreased MRI signal in multiple regions of occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula. These results are consistent with animal experiments and point to the alpha rhythm as an index of cortical inactivity that may be generated in part by the thalamus. These results also may have important implications for interpretation of resting baseline in fMRI studies.

Growing evidence suggests that loudness dependency of auditory evoked potentials (LDAEP) and resting EEG alpha and theta may be biological markers for predicting response to antidepressants. In spite of this promise, little is known about the joint reliability of these markers, and thus their clinical applicability. New standardized procedures were developed to improve the compatibility of data acquired with different EEG platforms, and used to examine test-retest reliability for the three electrophysiological measures selected for a multisite project-Establishing Moderators and Biosignatures of Antidepressant Response for Clinical Care (EMBARC). Thirty-nine healthy controls across four clinical research sites were tested in two sessions separated by about 1 week. Resting EEG (eyes-open and eyes-closed conditions) was recorded and LDAEP measured using binaural tones (1000 Hz, 40 ms) at five intensities (60-100 dB SPL). Principal components analysis of current source density waveform...

■ Ongoing variability in neural signaling is an intrinsic property of the brain. Often this variability is considered to be noise and ignored. However, an alternative view is that this variability is fundamental to perception and cognition and may be particularly important in decision-making. Here, we show that a momentary measure of occipital alpha-band power (8-13 Hz) predicts choices about where human participants will focus spatial attention on a trial-by-trial basis. This finding provides evidence for a mechanistic account of decision-making by demonstrating that ongoing neural activity biases voluntary decisions about where to attend within a given moment. ■

Recent studies have suggested an information-processing bias in social phobia (SP). Little is known about the electrophysiological correlates of anxiety in SP. The aim of the present study was to investigate the quantitative electroencephalogram (EEG) in 25 drug-free patients with SP as compared with age- and sex-matched normal controls and to correlate anxiety and depressive symptoms with EEG data. EEG was recorded under vigilance-controlled and resting conditions. The Spielberger State and Trait Anxiety Scale (STAI) and the Beck Depression Inventory (BDI) were administered to assess anxiety and depression levels. Multivariate analysis of variance revealed significant differences between patients and controls, specifically frontopolarly and right centrally. Statistical analysis demonstrated a decrease in absolute and relative delta, theta power, alpha-adjacent slow-beta and fast beta power and an increase in absolute and relative intermediate beta power, as well as an acceleration ...

In previous papers we proposed that an increase in delta EEG activity during mental tasks might be related to an increase in subjects' attention to internal processing, In this paper we have made a narrow band analysis to detect those EBG frequencies that change selectively during the performance of a mental task that requires attention to internal processing. Two different experiments were performed: (1) a difficult mental calculation task and a control stimulus with the same physical characteristics as the arithmetical symbols were presented in random order; (2) the, Stemberg paradigm for the analysis of short term memory using a memory set of 5 or 3 digits was also presented in random order. Referential recordings to linked ears were obtained in all leads of the lo/20 system. In the ,first experiment, the increase of power from 1.56 to 5.46 Hz was observed only during the performance of the task and not during the control condition. In the Stemberg paradigm, the increase of power from 1.56 to 3.90 Hz was greater during the difficult than during the easy condition. l!hese results support our hypothesis that an increase in delta activity may be related to attention to internal processing during the performance of a mental task. postulated the existence of two kinds, of' behavioral inhibition, both represented by slow waves in the EEG. 'Class I inhibition' would refer to a gross inactivation of an entire excitatory process; resulting in a relaxed, less active state, as in sleep. 'Class II inhibition' would selectively suppress inappropriate or non-relevant neural activity during the performance of a mental task.

The current review presents the empirical findings on varying definitions of nonrestorative sleep (NRS). Despite lacking a standard, operational definition, NRS is investigated in research studies and included in diagnostic manuals. However, because of the absence of standardization, the conclusions that can be drawn about NRS based on the current body of empirical literature are limited. A feeling of being unrefreshed upon awakening that is not accounted for by lack of sleep may occur among a substantial percentage of the population. This experience is correlated with daytime impairment, pain, fatigue, and electroencephalogram (EEG) arousals in non-REM sleep but causal links are unsubstantiated. An immediate converging of researchers toward NRS standardization is needed. We conclude that conceptualizing NRS as a primary symptom of insomnia on par with difficulty initiating sleep and difficulty maintaining sleep is empirically unsubstantiated. We recommend defining NRS as a report of persistently feeling unrefreshed upon awakening in the presence of a normal sleep duration, occurring in the absence of a sleep disorder.

Exploring EEG alpha oscillations has generated considerable interest, in particular with regards to the role they play in cognitive, psychomotor, psycho-emotional and physiological aspects of human life. However, there is no clearly agreed upon definition of what constitutes 'alpha activity' or which of the many indices should be used to characterize it. To address these issues this review attempts to delineate EEG alpha-activity, its physical, molecular and morphological nature, and examine the following indices: (1) the individual alpha peak frequency; (2) activation magnitude, as measured by alpha amplitude suppression across the individual alpha bandwidth in response to eyes opening, and (3) alpha "auto-rhythmicity" indices: which include intra-spindle amplitude variability, spindle length and steepness. Throughout, the article offers a number of suggestions regarding the mechanism(s) of alpha activity related to inter and intra-individual variability. In addition, it provides some insights into the various psychophysiological indices of alpha activity and highlights their role in optimal functioning and behavior.

Light exposure at night increases alertness; however, it is not clear if light affects nocturnal alertness in the same way that it affects measures of circadian regulation. The purpose of this study was to determine if a previously established functional relationship between light and nocturnal melatonin suppression was the same as that relating light exposure and nocturnal alertness. Four levels of narrow-band blue light at the cornea were presented during nighttime sessions. The ratio of electroencephalographic alpha power density with eyes closed to eyes open (alpha attenuation coefficient, AAC) and the Norris mood scale were used. The AAC and ratings of alertness increased monotonically with irradiance and were highly correlated. Both measures of alertness were highly correlated with model predictions of nocturnal melatonin suppression for the same circadian light stimulus, consistent with the inference that the suprachiasmatic nuclei play an important role in nocturnal alertness as well as circadian regulation.

We investigated whether creative cognition can be improved by means of cognitive and affective stimulation and whether these interventions are associated with changes of EEG alpha activity. Participants were required to generate original uses of conventional objects (Alternative Uses task, AU) while the EEG was recorded. In the cognitive stimulation condition, participants worked on the AU task subsequent to the exposure to other people's ideas. In the affective stimulation condition, they had to think creatively in positive affective states, induced via emotionally contagious sound clips. Creative cognition generally elicited alpha synchronization, most prominent in the prefrontal cortex and in the right hemisphere. The interventions were associated with stronger prefrontal alpha activity in the upper alpha band (10-12 Hz) than the control condition (no intervention), possibly indicating a state of heightened internal awareness, which might have a beneficial impact on creativity.

It has been shown that frontocentral electroencephalographic (EEG) alpha rhythms (about 10-12 Hz) were higher in amplitude in expert golfers in successful than unsuccessful putts, possibly reflecting the idea that amplitude regulation of frontocentral alpha rhythms is a physiological mechanism implied in motor control and golfer's performance ). Here, we tested the ancillary hypothesis that golfer's performance is also associated to an improved coordination of cortical activity, as reflected by functional coupling of alpha rhythms across cortical regions. To this aim, between-electrodes spectral coherence was computed from spatially enhanced EEG data of the mentioned study (i.e. right handed 12 expert golfers; augmented 10-20 system; surface Laplacian estimation). Low-(about 8-10 Hz) and high-frequency (about 10-12 Hz) alpha sub-bands were considered with reference to individual alpha frequency peak. Statistical results showed that intra-hemispheric low-frequency alpha coherence in bilateral parietal-frontal (P3-F3 and P4-F4 electrodes) and parietal-central (P3-C3 and P4-C4 electrodes) was higher in amplitude in successful than unsuccessful putts (p b 0.004). The same was true for intra-hemispheric high-frequency alpha coherence in bilateral parietal-frontal regions (p b 0.004). These findings suggest that intra-hemispheric functional coupling of cortical alpha rhythms between "visuo-spatial" parietal area and other cortical areas is implicated in fine motor control of golfer's performance.

This study investigated differences in cognitive processes related to problem complexity. It was assumed that these differences would be reflected in respondents' EEG activity--spectral power and coherence. A second issue of the study was to compare differences between the lower (alpha(1) = 7.9-10.0 Hz), and upper alpha band (alpha(2) = 10.1-12.9 Hz). In the first experiment two well-defined problems with two levels of complexity were used. Only minor differences in EEG power and coherence measures related to problem complexity were observed. In the second experiment divergent production problems resembling tasks on creativity tests were compared with dialectic problems calling for creative solutions. Differences in EEG power measures were mainly related to the form of problem presentation (figural/verbal). In contrast, coherence was related to the level of creativity needed to solve a problem. Noticeable increased intra- and interhemispheric cooperation between mainly the far distant brain regions was observed in the EEG activity of respondents while solving the dialectic problems. These results are explained by the more intense involvement of the long cortico-cortical fiber system in creative thinking. Differences between the lower and upper alpha band were significant for the power and coherence measures. In Experiment 2, fewer differences were observed in power measures in the upper alpha band than in the lower alpha band. A reverse pattern was observed for the coherence measures. These results hint to a functional independence of the two alpha bands, however, they do not allow to draw firm conclusions about their functional meanings. The study showed that it is unlikely that individuals solve well- and ill-defined problems by employing similar cognitive strategies.

This study investigated the proposition of relaxation offered by performing the Muslim prayers by measuring the alpha brain activity in the frontal (F3-F4), central (C3-C4), parietal (P3-P4), and occipital (O1-O 2) electrode placements using the International 10-20 System. Nine Muslim subjects were asked to perform the four required cycles of movements of Dhuha prayer, and the EEG were subsequently recorded with open eyes under three conditions, namely, resting, performing four cycles of prayer while reciting the specific verses and supplications, and performing four cycles of acted salat condition (prayer movements without any recitations). Analysis of variance (ANOVA) tests revealed that there were no significant difference in the mean alpha relative power (RPa) between the alpha amplitude in the Dhuha prayer and the acted conditions in all eight electrode positions. However, the mean RPa showed higher alpha amplitude during the prostration position of the Dhuha prayer and acted condition at the parietal and occipital regions in comparison to the resting condition. Findings were similar to other studies documenting increased alpha amplitude in parietal and occipital regions during meditation and mental concentration. The incidence of increased alpha amplitude suggested parasympathetic activation, thus indicating a state of relaxation. Subsequent studies are needed to delineate the role of mental concentration, and eye focus, on alpha wave amplitude while performing worshipping acts. © Springer Science+Business Media, LLC 2011.

http://www.ncbi.nlm.nih.gov/pubmed/21965118 
http://link.springer.com/article/10.1007/s10484-011-9170-1

The EEG was recorded while subjects judged whether sequentially presented feature-concept pairs are semantically congruent. Later and without prior warning they had to perform a semantic and episodic memory task. The results show that the upper alpha band is most sensitive to the encoding and processing of semantic information. It is only the upper alpha band that distinguishes between good and bad semantic memory performers and that shows significant correlations with semantic memory performance during that time period, semantic processing actually takes place. Even when the influence of episodic memory was removed by partial correlations, a reliable association between upper alpha desynchronization and semantic memory was observed.

. The results of a specially designed memory search paradigm which maximizes episodic short-term memory STM and minimizes Ž . semantic long-term memory LTM demands show that the upper alpha band synchronizes selectively in those conditions and time intervals where episodic STM demands are maximal. This finding of a selective alpha synchronization occurring only in the upper alpha band and during highest task demands is surprising because it is well known that usually alpha desynchronizes during mental activity. Because experiments from our laboratory indicate that desynchronization in the upper alpha band is related to semantic LTM processes, the present finding suggests that a selective synchronization in this frequency band reflects inhibition of semantic LTM. It is assumed that once the capacity limits of STM are reached or exceeded, processing resources are no longer distributed and that potentially interfering, task irrelevant, brain areas or processing systems are inhibited. q

The effect of partial sleep deprivation and driving duration on subsequent alertness and performance in car drivers was investigated. Twenty healthy male subjects, between 25 and 55 years of age, free from any sleep disorder, took part in two simulated driving sessions carried out between 2 p.m. and 4 p.m. Before one session, subjects were sleep deprived as they were allowed to sleep only between 3 a.m. and 7 a.m. during the preceding night. Throughout the driving task, the subjects' driving performance, electroencephalogram and Karolinska Sleepiness Scale (KSS) score were recorded. The results revealed that sleep deprivation had an effect on KSS score but not on the (alpha + theta) spectral power, while driving duration had an effect on these two parameters. This effect was also influenced by sleep restriction. Time on driving task alone had a significant effect on driving performance; the sleep restriction having only an effect on one of the performances indices studied: the number of right edge-line crossings. These results are interpreted in terms of the relationship between level of alertness and performance impairment. D

Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ...

As one in a series on the impact of EEG-neurofeedback in the performing arts, we set out to replicate a previous dance study in which alpha/theta (A/T) neurofeedback and heart rate variability (HRV) biofeedback enhanced performance in competitive ballroom dancers compared with controls. First year contemporary dance conservatoire students were randomised to the same two psychophysiological interventions or a choreology instruction comparison group or a no-training control group. While there was demonstrable neurofeedback learning, there was no impact of the three interventions on dance performance as assessed by four experts. However, HRV training reduced anxiety and the reduction correlated with improved technique and artistry in performance; the anxiety scale items focussed on autonomic functions, especially cardiovascular activity. In line with the putative impact of hypnogogic training on creativity A/T training increased cognitive creativity with the test of unusual uses, but not insight problems. Methodological and theoretical implications are considered.

Professionally significant enhancement of music and dance performance and mood has followed training with an EEG-neurofeedback protocol which increases the ratio of theta to alpha waves using auditory feedback with eyes closed. While originally the protocol was designed to induce hypnogogia, a state historically associated with creativity, the outcome was psychological integration, while subsequent applications focusing on raising the theta-alpha ratio, reduced depression and anxiety in alcoholism and resolved post traumatic stress syndrome (PTSD). In optimal performance studies we confirmed associations with creativity in musical performance, but effects also included technique and communication. We extended efficacy to dance and social anxiety. Diversity of outcome has a counterpart in wide ranging associations between theta oscillations and behaviour in cognitive and affective neuroscience: in animals with sensory-motor activity in exploration, effort, working memory, learning, retention and REM sleep; in man with meditative concentration, reduced anxiety and sympathetic autonomic activation, as well as task demands in virtual spatial navigation, focussed and sustained attention, working and recognition memory, and having implications for synaptic plasticity and long term potentiation. Neuroanatomical circuitry involves the ascending mescencephalic-cortical arousal system, and limbic circuits subserving cognitive as well as affective/ motivational functions. Working memory and meditative bliss, representing cognitive and affective domains, respectively, involve coupling between frontal and posterior cortices, exemplify a role for theta and alpha waves in mediating the interaction between distal and widely distributed connections. It is posited that this mediation in part underpins the integrational attributes of alpha-theta training in optimal performance and psychotherapy, creative associations in hypnogogia, and enhancement of technical, communication and artistic domains of performance in the arts.

During the past two decades growing evidence indicates that brain oscillations in the alpha band (∼10 Hz) not only reflect an "idle" state of cortical activity, but also take a more active role in the generation of complex cognitive functions. A recent study shows that more than 60% of the observed inter-subject variability in perceptual learning can be ascribed to ongoing alpha activity. This evidence indicates a significant role of alpha oscillations for perceptual learning and hence motivates to explore the potential underlying mechanisms. Hence, it is the purpose of this review to highlight existent evidence that ascribes intrinsic alpha oscillations a role in shaping our ability to learn. In the review, we disentangle the alpha rhythm into different neural signatures that control information processing within individual functional building blocks of perceptual learning. We further highlight computational studies that shed light on potential mechanisms regarding how alpha oscillations may modulate information transfer and connectivity changes relevant for learning. To enable testing of those model based hypotheses, we emphasize the need for multidisciplinary approaches combining assessment of behavior and multi-scale neuronal activity, active modulation of ongoing brain states and computational modeling to reveal the mathematical principles of the complex neuronal interactions. In particular we highlight the relevance of multi-scale modeling frameworks such as the one currently being developed by "The Virtual Brain" project.

Finding the means to efficiently summarize electroencephalographic data has been a long-standing problem in electrophysiology. A popular approach is identification of component modes on the basis of the timevarying spectrum of multichannel EEG recordings-in other words, a space/frequency/time atomic decomposition of the time-varying EEG spectrum. Previous work has been limited to only two of these dimensions. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) have been used to create space/time decompositions; suffering an inherent lack of uniqueness that is overcome only by imposing constraints of orthogonality or independence of atoms. Conventional frequency/time decompositions ignore the spatial aspects of the EEG. Framing of the data being as a three-way array indexed by channel, frequency, and time allows the application of a unique decomposition that is known as Parallel Factor Analysis (PARAFAC). Each atom is the tri-linear decomposition into a spatial, spectral, and temporal signature. We applied this decomposition to the EEG recordings of five subjects during the resting state and during mental arithmetic. Common to all subjects were two atoms with spectral signatures whose peaks were in the theta and alpha range. These signatures were modulated by physiological state, increasing during the resting stage for alpha and during mental arithmetic for theta. Furthermore, we describe a new method (Source Spectra Imaging or SSI) to estimate the location of electric current sources from the EEG spectrum. The topography of the theta atom is frontal and the maximum of the corresponding SSI solution is in the anterior frontal cortex. The topography of the alpha atom is occipital with maximum of the SSI solution in the visual cortex. We show that the proposed decomposition can be used to search for activity with a given spectral and topographic profile in new recordings, and that the method may be useful for artifact recognition and removal.

Background. Electroencephalographic (EEG) biofeedback has been employed in substance use disorder (SUD) over the last 3 decades. SUD is a complex series of disorders with frequent comorbidities and EEG abnormalities of several types. Methods and Results. EEG biofeedback has been employed in conjunction with other therapies and may be useful in enhancing certain outcomes of therapy. Based on published clinical studies and employing efficacy criteria adapted by the Association for Applied Psychophysiology and Biofeedback and the International Society for Neurofeedback and Research, alpha theta training, either alone for alcoholism or in combination with beta training for stimulant and mixed substance abuse and combined with residential treatment programs, is probably efficacious. Conclusion. Considerations of further research design taking these factors into account are discussed and descriptions of contemporary research are given.

In previous papers we proposed that an increase in delta EEG activity during mental tasks might be related to an increase in subjects' attention to internal processing, In this paper we have made a narrow band analysis to detect those EBG frequencies that change selectively during the performance of a mental task that requires attention to internal processing. Two different experiments were performed: (1) a difficult mental calculation task and a control stimulus with the same physical characteristics as the arithmetical symbols were presented in random order; (2) the, Stemberg paradigm for the analysis of short term memory using a memory set of 5 or 3 digits was also presented in random order. Referential recordings to linked ears were obtained in all leads of the lo/20 system. In the ,first experiment, the increase of power from 1.56 to 5.46 Hz was observed only during the performance of the task and not during the control condition. In the Stemberg paradigm, the increase of power from 1.56 to 3.90 Hz was greater during the difficult than during the easy condition. l!hese results support our hypothesis that an increase in delta activity may be related to attention to internal processing during the performance of a mental task. postulated the existence of two kinds, of' behavioral inhibition, both represented by slow waves in the EEG. 'Class I inhibition' would refer to a gross inactivation of an entire excitatory process; resulting in a relaxed, less active state, as in sleep. 'Class II inhibition' would selectively suppress inappropriate or non-relevant neural activity during the performance of a mental task.

In the companion report (Başar, this volume), the physiological fundaments of alpha activity in integrative brain function are described. The present report is a review of the significant role of alpha activity in memory and cognitive processes in healthy subjects, and in cognitive impairment. The role of neurotransmitters is also described, briefly, in this context.

Cortical sources of resting eyes-closed alpha rhythms are typically abnormal in mild cognitive impairment (MCI) and Alzheimer's disease (AD) subjects. Here we tested the hypothesis of a progressive impairment of cortical alpha reactivity to eyeopening across amnesic MCI and mild AD subjects, reflecting another aspect of the impairment of cortical neural synchronization. Resting electroencephalography (EEG) data were recorded in 36 normal elderly subjects (Nold), 91 amnesic MCI, and 31 mild AD subjects during eyes-closed and -open conditions. EEG sources were estimated by LORETA software. In the eye-closed condition, posterior alpha 1 (8-10.5 Hz) sources were lower in MCI and AD than Nold subjects. The opposite was true for occipital delta sources (2-4 Hz). Reactivity to the eyes-open condition showed posterior alpha 1 and alpha 2 (10.5-13 Hz) sources was high in the Nold, intermediate in the MCI, and low in the AD subjects. Furthermore, occipital alpha 1 reactivity across MCI and AD subjects was correlated to the cognitive impairment as revealed by Mini-Mental State Examination score. In conclusion, at least at group level, the continuum across amnesic MCI and mild AD status is related to an impaired reactivity of cortical neuronal synchronization to eyes opening at alpha rhythms. memory complaints and cognitive impairment on neuropsychological testing not yet fulfilling the clinical picture of dementia . Amnesic MCI is regarded as a precursor of Alzheimer's disease (AD) [4-6] since recent studies have shown a high rate of progression to AD [3,. In cognitively intact elderly subjects, the incidence of AD ranges from 0.17 to 3.86% , while in amnesic MCI subjects it ranges from 6 to 25% . However, the "transition" hypothesis is chal-

We tested the working hypothesis that electromagnetic fields from mobile phones (EMFs) affect interhemispheric synchronization of cerebral rhythms, an important physiological feature of information transfer into the brain. Ten subjects underwent two electroencephalographic (EEG) recordings, separated by 1 week, following a crossover double-blind paradigm in which they were exposed to a mobile phone signal (global system for mobile communications; GSM). The mobile phone was held on the left side of the subject head by a modified helmet, and orientated in the normal position for use over the ear. The microphone was orientated towards the corner of the mouth, and the antenna was near the head in the parietotemporal area. In addition, we positioned another similar phone (but without battery) on the right side of the helmet, to balance the weight and to prevent the subject localizing the side of GSM stimulation (and consequently lateralizing attention). In one session the exposure was real (GSM) while in the other it was Sham; both sessions lasted 45 min. Functional interhemispheric connectivity was modelled using the analysis of EEG spectral coherence between frontal, central and parietal electrode pairs. Individual EEG rhythms of interest were delta (about 2-4 Hz), theta (about 4-6 Hz), alpha 1 (about 6-8 Hz), alpha 2 (about 8-10 Hz) and alpha 3 (about 10-12 Hz). Results showed that, compared to Sham stimulation, GSM stimulation modulated the interhemispheric frontal and temporal coherence at alpha 2 and alpha 3 bands. The present results suggest that prolonged mobile phone emission affects not only the cortical activity but also the spread of neural synchronization conveyed by interhemispherical functional coupling of EEG rhythms.

Objective: This study examined the use of caffeine to manipulate arousal level without the confounds associated with task-related activation. From previous work in our laboratory, an increase in skin conductance level (SCL) and EEG alpha frequency, together with a global decrease in alpha power, were used as markers of arousal increase, and we sought to identify these effects with caffeine ingestion. Methods: We examined the effect of a single oral dose of caffeine (250 mg) in a randomised double-blind placebo-controlled repeatedmeasures cross-over study. Eighteen healthy university students (mean age 21 years; 13/18 females) participated in two sessions 1 week apart. EEG and autonomic data (SCL, heart rate, systolic and diastolic blood pressure, and respiration rate) from a 2 min eyes-closed epoch, commencing approximately 30 min after ingestion of caffeine or placebo, were examined. Results: Caffeine was associated with increased SCL, a global reduction in EEG power in the alpha band, and a global increase in alpha frequency. There were no cardiovascular effects. Conclusions: The positive results are consistent with recent electrodermal and EEG studies of arousal and suggest that caffeine may be utilised as a task-free means of manipulating arousal in future investigations. Further work is necessary to clarify the absence of cardiovascular effects, and to integrate those data with emerging conceptualisations of arousal and activation. Significance: The present data support the use of caffeine as a simple tool to explore the role of arousal in both normal and atypical functioning, and this may be useful in determining the validity and importance of supposed hyper-or hypo-arousal in such syndromes as attention-deficit/hyperactivity disorder (AD/HD).

Transcranial alternating current stimulation (tACS) is used in clinical applications and basic neuroscience research. Although its behavioral effects are evident from prior reports, current understanding of the mechanisms that underlie these effects is limited. We used motion perception, a percept with relatively well known properties and underlying neural mechanisms to investigate tACS mechanisms. Healthy human volunteers showed a surprising improvement in motion sensitivity when visual stimuli were paired with 10 Hz tACS. In addition, tACS reduced the motion-after effect, and this reduction was correlated with the improvement in motion sensitivity. Electrical stimulation had no consistent effect when applied before presenting a visual stimulus or during recovery from motion adaptation. Together, these findings suggest that perceptual effects of tACS result from an attenuation of adaptation. Important consequences for the practical use of tACS follow from our work. First, because t...

Activation of a default mode network (DMN) including frontal and parietal midline structures varies with cognitive load, being more active during low-load tasks and less active during high-load tasks requiring executive control. Meditation practices entail various degrees of cognitive control. Thus, DMN activation patterns could give insight into the nature of meditation practices. This 10-week random-assignment study compared theta2, alpha1, alpha2, beta1, beta2 and gamma EEG coherence, power, and eLORETA cortical sources during eyes-closed rest and Transcendental Meditation (TM) practice in 38 male and female college students, average age 23.7 years. Significant brainwave differences were seen between groups. Compared to eyesclosed rest, TM practice led to higher alpha1 frontal log-power, and lower beta1 and gamma frontal and parietal log-power; higher frontal and parietal alpha1 interhemispheric coherence and higher frontal and frontal-central beta2 intrahemispheric coherence. eLORETA analysis identified sources of alpha1 activity in midline cortical regions that overlapped with the DMN.

SYNOPSIS Previous research on meditation and the EEG is described, and findings relating to EEG patterns during meditation are discussed. Comparisons of meditation with other altered states are reviewed and it is concluded that, on the basis of existing EEG evidence, there is some reason for differentiating between meditation and drowsing. Research on alpha-blocking and habituation of the blocking response during meditation is reviewed, and the effects of meditation on EEG patterns outside of meditation are described. In conclusion, the need for more precisely formulated research is pointed out.

Evidence is presented that EEG oscillations in the alpha and theta band reflect cognitive and memory performance in particular. Good Ž . Ž . performance is related to two types of EEG phenomena i a tonic increase in alpha but a decrease in theta power, and ii a large phasic Ž . event-related decrease in alpha but increase in theta, depending on the type of memory demands. Because alpha frequency shows large interindividual differences which are related to age and memory performance, this double dissociation between alpha vs. theta and tonic vs. phasic changes can be observed only if fixed frequency bands are abandoned. It is suggested to adjust the frequency windows of alpha and theta for each subject by using individual alpha frequency as an anchor point. Based on this procedure, a consistent interpretation of a Ž variety of findings is made possible. As an example, in a similar way as brain volume does, upper alpha power increases but theta power . decreases from early childhood to adulthood, whereas the opposite holds true for the late part of the lifespan. Alpha power is lowered and theta power enhanced in subjects with a variety of different neurological disorders. Furthermore, after sustained wakefulness and during the transition from waking to sleeping when the ability to respond to external stimuli ceases, upper alpha power decreases, whereas Ž . theta increases. Event-related changes indicate that the extent of upper alpha desynchronization is positively correlated with semantic long-term memory performance, whereas theta synchronization is positively correlated with the ability to encode new information. The reviewed findings are interpreted on the basis of brain oscillations. It is suggested that the encoding of new information is reflected by Ž . theta oscillations in hippocampo-cortical feedback loops, whereas search and retrieval processes in semantic long-term memory are reflected by upper alpha oscillations in thalamo-cortical feedback loops. q

It is currently claimed that congenitally blind do not have visual imagery and are therefore unable to present visual contents in their dreams. The aim of our study was to quantitatively evaluate the existence of visual imagery in born-blind dreams and to correlate it with objective measures, such as sleep EEG frequency components, namely with alpha attenuation (regarded as an indicator of visual activity), and graphical analysis of dream pictorial representations. The investigation was carried out via simultaneous recordings of dream reports and polysomnography, during nocturnal sleep at volunteers' homes; scheduled regular awakenings during the night provided the data for dream and EEG analysis. In the morning, subjects were asked to make a drawing of their dream images. Congenitally blind (n510) were comparable to normal sighted subjects (n59): the two groups presented equivalent visual activity indices, and no differences in the analysis of graphical representation of dreaming imagery. However, blind subjects presented a lower rate of dream recall than sighted (27% versus 42%). Both groups had significant negative correlation between Visual Activity Index (VAI) and alpha power in the central and occipital O2 derivations (blind: C4: r520. 615, P,0.005; O2: r520.608, P,0.006; sighted: C4: r520.633, P,0.01; O2: r520.506, P,0.05). This correlation was weaker for the blind in O1 (r520.573, P,0.05) and non-existent for the sighted. Blind individuals have significantly lower alpha activity in the central derivation. In conclusion, the congenitally blind have visual content in their dreams and are able to draw it and, as expected, their VAI is negatively correlated with EEG alpha power. 

Induced alpha power (in a lower, intermediate and upper band) which is deprived from evoked electroencephalograph (EEG) activity was analyzed in an oddball task in which a warning signal (WS) preceded a target or non-target. The lower band, reflecting phasic alertness, desynchronizes only in response to the WS and target. The intermediate band, reflecting expectancy, desynchronizes about 1 s before a target or non-target appears. Upper alpha desynchronizes only after a target is presented and, thus, reflects the performance of the task which was to count the targets. Thus, only slower alpha frequencies reflect attentional demands such as alertness and expectancy.

An integrative theoretical approach about memory related oscillations is presented. The basic assumptions are that memory related oscillations are probably confined to theta and upper alpha and that other frequencies particularly in the gamma range are important for memory primarily because they become coupled to lower frequencies and/or because they play a specific role for a high precision timing of neural events (including phenomena such as LTP or LTD). In contrast to previous studies, where we related theta and upper alpha to a variety of different memory processes, we suggest here that these oscillations are associated with top-down control processes in two large storage systems, working memory (WM) and long-term memory (LTM). These systems may have their own types of top-down processes that control access to and/or manipulation of stored information. The hypothesis, suggested here is that theta and upper alpha reflect these processes which can be best studied when analyzing phase.

Past research has been unable to address whether the activity in the frontal hemispheres is related to the direction of motivation (approach versus withdrawal) or valence of emotion (positive versus negative). The present study was an attempt to address this question by using a standardized low-resolution brain electromagnetic tomography (sLORETA) which provides EEG localization measures that are independent of the recording reference. Resting EEG, self-report measures of Behavioral Activation and Inhibition System (BAS and BIS) strength, dispositional optimism and a measure of hedonic tone, were collected from 51 unselected undergraduates. Three measures of cortical activation were obtained: (a) alpha asymmetry at conventional scalp sites, (b) anterior and posterior source alpha asymmetries (sLORETA method), (c) posterior versus frontal delta and theta activity. Both alpha asymmetry measures (conventional EEG and sLORETA) yielded significant frontal and parietal asymmetry correlation patterns. Neither measure identified significant associations between resting posterior versus frontal delta and theta activity personality traits. Higher BAS was uniquely related to greater left-sided activation in the middle frontal gyrus (BA11). Optimism was associated with higher activations in the left-superior frontal gyrus (BA10) and in the right-posterior cingulate cortex (BA31).

The catecholamines-dopamine and noradrenaline-play important roles in directing and guiding behavior. Disorders of these systems, particularly within the dopamine system, are associated with several severe and chronically disabling psychiatric and neurological disorders. We used the recently published group independent components analysis (ICA) procedure outlined by Chen et al. (2013) to present the first pharmaco-EEG ICA analysis of the resting-state EEG in healthy participants administered 0.45 mg/kg dexamphetamine. Twenty-eight healthy participants between 18 and 41 were recruited. Bayesian nested-domain models that explicitly account for spatial and functional relationships were used to contrast placebo and dexamphetamine on component spectral power and several connectivity metrics. Dexamphetamine led to reductions across delta, theta, and alpha spectral power bands that were predominantly localized to Frontal and Central regions. Beta 1 and beta 2 power were reduced by dexamphe...

Visual P300 is consistently lower in alcohol-dependent individuals, their offspring and subjects at risk. Delta and theta event-related oscillations (ERO) are the major contributors to the P300 signal. The total and evoked power in delta and theta bands in the 300 to 700 ms post-stimulus window (corresponding to the zone of P300 maxima) was compared between adolescent offspring of alcoholics (high-risk) and age-matched normal controls (low-risk), to assess the utility of the risk markers.

Background: Neuronal elements underlying perception, cognition, and action exhibit distinct oscillatory phenomena, measured in humans by electro-or magnetoencephalography (EEG/MEG). So far, the correlative or causal nature of the link between brain oscillations and functions has remained elusive. A compelling demonstration of causality would primarily generate oscillatory signatures that are known to correlate with particular cognitive functions and then assess the behavioral consequences. Here, we provide the first direct evidence for causal entrainment of brain oscillations by transcranial magnetic stimulation (TMS) using concurrent EEG. Results: We used rhythmic TMS bursts to directly interact with an MEG-identified parietal a-oscillator, activated by attention and linked to perception. With TMS bursts tuned to its preferred a-frequency (a-TMS), we confirmed the three main predictions of entrainment of a natural oscillator: (1) that a-oscillations are induced during a-TMS (reproducing an oscillatory signature of the stimulated parietal cortex), (2) that there is progressive enhancement of this a-activity (synchronizing the targeted, a-generator to the a-TMS train), and (3) that this depends on the pre-TMS phase of the background a-rhythm (entrainment of natural, ongoing a-oscillations). Control conditions testing different TMS burst profiles and TMS-EEG in a phantom head confirmed specificity of a-boosting to the case of synchronization between TMS train and neural oscillator. Conclusions: The periodic electromagnetic force that is generated during rhythmic TMS can cause local entrainment of natural brain oscillations, emulating oscillatory signatures activated by cognitive tasks. This reveals a new mechanism of online TMS action on brain activity and can account for frequency-specific behavioral TMS effects at the level of biologically relevant rhythms.

The relationship of reading-writing ability and EEG coherences was studied in 84 subjects from two age groups 7.0-8.9 and 9-11.2 years old. All children were divided into three groups according to their performance on a pedagogical test: pedl, normal children; ped2, children with mild problems; ped3, children with reading-writing disability. The following results were obtained: in general, children showed higher coherences in groups with poor performance in the delta, theta and beta bands. In the alpha band, higher coherence values were related to better performance.

Introduction. -Increasing knowledge of the anatomical structures and cellular processes underlying psychiatric disorders may help bridge the gap between clinical signs and basic physiological processes. Accordingly, considerable insight has been gained in recent years into a common psychiatric condition, i.e., chronic alcoholism. Material and methods. -We reviewed various physiological parameters that are altered in chronic alcoholic patients compared to healthy individuals -continuous electroencephalogram, oculomotor measures, cognitive event-related potentials and event-related oscillations -to identify links between these physiological parameters, altered cognitive processes and specific clinical symptoms.

This study explores the physiological correlates of a highly practiced Kundalini Yoga meditator. Thoracic and abdominal breathing patterns, heart rate (HR), occipital parietal electroencephalograph (EEG), skin conductance level (SCL), and blood volume pulse (BVP) were monitored during prebaseline, meditation, and postbaseline periods. Visual analyses of the data showed a decrease in respiration rate during the meditation from a mean of 11 breaths/min for the pre- and 13 breaths/min for the postbaseline to a mean of 5 breaths/min during the meditation, with a predominance of abdominal/diaphragmatic breathing. There was also more alpha EEG activity during the meditation (M = 1.71 μV) compared to the pre- (M = .47 μV) and postbaseline (M = .78 μV) periods, and an increase in theta EEG activity immediately following the meditation (M = .62 μV) compared to the pre-baseline and meditative periods (each with M = .26 μV). These findings suggest that a shift in breathing patterns may contribute to the development of alpha EEG, and those patterns need to be investigated further.

In the present high-resolution electroencephalographic (EEG) study, event-related desynchronization/synchronization (ERD/ERS) of alpha rhythms was computed during an S1 -S2 paradigm, in which a visual cue (S1) predicted a SHORT (600 ms) or LONG (1400 ms) foreperiod, preceding a visual go stimulus (S2) triggering right or left finger movement. Could orienting attention to a selective point in time influence the alpha rhythms as a function of the SHORT vs. LONG foreperiod? Stronger selective attentional modulations were predicted for the SHORT than LONG condition. EEG data from 54 channels were ''depurated'' from phase-locked visual evoked potentials and spatially enhanced by surface Laplacian estimation (i.e., final data analysis was conducted on 16 subjects having a sufficient number of artifact-free EEG single trials). Low-band alpha rhythms (about 6 -10 Hz) were supposed to be related to anticipatory attentional processes, whereas high-band alpha rhythms (10 -12 Hz) would indicate task-specific visuo-motor processes.

To define the spectrum of the epileptic syndromes and epilepsies (other than the idiopathic epilepsies of childhood with occipital paroxysms) that can be associated with fixation-off sensitivity (FOS), delineate the electrographic types of FOS abnormalities and identify the patterns that can be associated with clinical seizures, and examine whether there may be a pure form of fixation-off sensitive epilepsy. We reviewed the clinical and video EEG data of all our patients with FOS over the last 12 years. Children with idiopathic focal epilepsies and occipital EEG paroxysms were excluded. From January 1995 to December 2006, 19 of about 8,500 patients had had one or more video-EEGs with FOS, yielding an approximate incidence of 0.2%. From the 14 patients with full clinical and EEG data available, 12 had various epilepsies that included IGE phenotypes (7), symptomatic or probably symptomatic focal (3), cryptogenic generalised (1), and adult onset idiopathic photosensitive occipital (1),...