Familial clustering and DRD4 effects on electroencephalogram measures in multiplex families with attention deficit/hyperactivity disorder.

OBJECTIVE: The current study tests electroencephalogram (EEG) measures as a potential endophenotype for attention deficit/hyperactivity disorder (ADHD) by examining sibling and parent-offspring similarity, familial clustering with the disorder, and association with the dopamine receptor D4 (DRD4) candidate gene. METHOD: The sample consists of 531 participants (191 parents and 340 children) from 132 multiplex families with ADHD who participated in a larger genetics study. All members of the families underwent extensive assessment including semi-structured diagnostic interviews and EEG recording. RESULTS: Strong sibling similarity and parent-offspring correlations in EEG power emerged, suggesting high trait heritability. Increased theta power was observed among children with ADHD when compared with unaffected children, and there were no differences according to ADHD subtype. Within the parent sample, ADHD diagnostic status and ADHD subtype group differences emerged in the theta, alpha, and beta frequency bands. DRD4 effects for both parents and children were apparent in the beta frequency band and for children only in the theta frequency band. CONCLUSIONS: This study suggests that EEG measures are a promising avenue of study in the search for putative endophenotypes for ADHD, and that variability at the DRD4 gene may contribute to this endophenotype.

Attention modulates beta oscillations during prolonged tactile stimulation.

The inter-play between changes in beta-band (14-30-Hz) cortical rhythms and attention during somatosensation informs us about where and when relevant processes occur in the brain. As such, we investigated the effects of attention on somatosensory evoked and induced responses using vibrotactile stimulation and magnetoencephalographic recording. Subjects received trains of vibration at 23 Hz to the right index finger while watching a movie and ignoring the somatosensory stimuli or paying attention to the stimuli to detect a change in the duration of the stimulus. The amplitude of the evoked 23-Hz steady-state response in the contralateral primary somatosensory cortex (SI) was enhanced by attention and the underlying dipole source was located 2 mm more medially, indicating top-down recruitment of additional neuronal populations for the functionally relevant stimulus. Attentional modulation of the somatosensory evoked response indicates facilitation of early processing of the tactile stimulus. Beta-band activity increased after vibration offset in the contralateral primary motor cortex (MI) [event-related synchronization (ERS)] and this increase was larger for attended than ignored stimuli. Beta-band activity decreased in the ipsilateral SI prior to stimulus offset [event-related desynchronization (ERD)] for attended stimuli only. Whereas attention modulation of the evoked response was confined to the contralateral SI, event-related changes of beta-band activity involved contralateral SI-MI and inter-hemispheric SI-SI connections. Modulation of neural activity in such a large sensorimotor network indicates a role for beta activity in higher-order processing.

Endogenous control of waking brain rhythms induces neuroplasticity in humans.

This study explores the possibility of noninvasively inducing long-term changes in human corticomotor excitability by means of a brain-computer interface, which enables users to exert internal control over the cortical rhythms recorded from the scalp. We demonstrate that self-regulation of electroencephalogram rhythms in quietly sitting, naive humans significantly affects the subsequent corticomotor response to transcranial magnetic stimulation, producing durable and correlated changes in neurotransmission. Specifically, we show that the intrinsic suppression of alpha cortical rhythms can in itself produce robust increases in corticospinal excitability and decreases in intracortical inhibition of up to 150%, which last for at least 20 min. Our observations may have important implications for therapies of brain disorders associated with abnormal cortical rhythms, and support the use of electroencephalogram-based neurofeedback as a noninvasive tool for establishing a causal link between rhythmic cortical activities and their functions.

Syntactic unification operations are reflected in oscillatory dynamics during on-line sentence comprehension.

There is growing evidence suggesting that synchronization changes in the oscillatory neuronal dynamics in the EEG or MEG reflect the transient coupling and uncoupling of functional networks related to different aspects of language comprehension. In this work, we examine how sentence-level syntactic unification operations are reflected in the oscillatory dynamics of the MEG. Participants read sentences that were either correct, contained a word category violation, or were constituted of random word sequences devoid of syntactic structure. A time-frequency analysis of MEG power changes revealed three types of effects. The first type of effect was related to the detection of a (word category) violation in a syntactically structured sentence, and was found in the alpha and gamma frequency bands. A second type of effect was maximally sensitive to the syntactic manipulations: A linear increase in beta power across the sentence was present for correct sentences, was disrupted upon the occurrence of a word category violation, and was absent in syntactically unstructured random word sequences. We therefore relate this effect to syntactic unification operations. Thirdly, we observed a linear increase in theta power across the sentence for all syntactically structured sentences. The effects are tentatively related to the building of a working memory trace of the linguistic input. In conclusion, the data seem to suggest that syntactic unification is reflected by neuronal synchronization in the lower-beta frequency band.

Electroencephalogram theta/beta ratio and arousal in attention-deficit/hyperactivity disorder: evidence of independent processes.

BACKGROUND: For nearly 20 years, the theta/beta power ratio in the electroencephalogram (EEG) has been used within the attention-deficit/hyperactivity disorder (ADHD) literature as a marker of central nervous system (CNS) arousal, underpinning current models of the disorder. However, this usage has not been validated. We aimed to directly test the theta/beta ratio as a marker of arousal within this population. METHODS: Resting state EEG activity was investigated as a function of CNS arousal in two age-matched groups of boys (each n = 30), with and without ADHD. Arousal was defined in terms of skin conductance level (SCL), which has a long history as a measure of CNS arousal. RESULTS: Relative theta power and the theta/beta ratio were elevated, and SCL and relative alpha and beta power were reduced, in the ADHD group compared with control subjects. In both groups, mean alpha level correlated negatively with SCL. There was no significant correlation between the theta/beta ratio and SCL. CONCLUSIONS: These data contradict the supposed linkage between the theta/beta ratio and arousal in ADHD, confirming previous results from normal children. They suggest the need for reevaluation of current models of the disorder and reconceptualization of existing EEG data from both normal and atypical populations.

The transliminal brain at rest: baseline EEG, unusual experiences, and access to unconscious mental activity.

Transliminality reflects individual differences in the threshold at which unconscious processes or external stimuli enter into consciousness. Individuals high in transliminality possess characteristics such as magical ideation, belief in the paranormal, and creative personality traits, and also report the occurrence of manic/mystic experiences. The goal of the present research was to determine if resting brain activity differs for individuals high versus low in transliminality. We compared baseline EEG recordings (eyes-closed) between individuals high versus low in transliminality, assessed using The Revised Transliminality Scale of Lange et al. (2000). Identifying reliable differences at rest between high- and low-transliminality individuals would support a predisposition for transliminality-related traits. Individuals high in transliminality exhibited lower alpha, beta, and gamma power than individuals low in transliminality over left posterior association cortex and lower high alpha, low beta, and gamma power over the right superior temporal region. In contrast, when compared to individuals low in transliminality, individuals high in transliminality exhibited greater gamma power over the frontal-midline region. These results are consistent with prior research reporting reductions in left temporal/parietal activity, as well as the desynchronization of right temporal activity in schizotypy and related schizophrenia spectrum disorders. Further, differences between high- and low-transliminality groups extend existing theories linking altered hemispheric asymmetries in brain activity to a predisposition toward schizophrenia, paranormal beliefs, and unusual experiences.

Centrally controlled heart rate changes during mental practice in immersive virtual environment: a case study with a tetraplegic.

A tetraplegic patient was able to induce midcentral localized beta oscillations in the electroencephalogram (EEG) after extensive mental practice of foot motor imagery. This beta oscillation was used to simulate a wheel chair movement in a virtual environment (VE). The analysis of electrocardiogram (ECG) data revealed that the induced beta oscillations were accompanied by a characteristic heart rate (HR) change in form of a preparatory HR acceleration followed by a short-lasting deceleration in the order of 10-20 bpm (beats-per-minute). This provides evidence that mental practice of motor performance is accompanied not only by activation of cortical structures but also by central commands into the cardiovascular system with its nuclei in the brain stem.

Emotional & electroencephalographic responses during affective picture viewing after exercise.

We examined the effects of 30 min of cycling exercise at a moderate intensity of 50% peak oxygen uptake, compared to 30 min of rest, on changes in emotional responses to pictorial foreground stimuli that reliably elicit unpleasant, neutral, and pleasant affect. Emotional responses were measured by self-reports of valence (unpleasant to pleasant) and arousal (low to high) and by hemispheric asymmetry (R-L) of frontal and parietal brain electroencephalographic (EEG) activity in 13 females and 21 males (24+/-3 y). Compared to after rest, self-reports of arousal in response to unpleasant slides were diminished after exercise, but self-reports of valence and frontal asymmetry of alpha frequencies were generally unchanged. Even so, there were differential responses in asymmetry in the beta frequencies in the frontal region and for alpha and beta frequencies in the parietal region, indicative of decreased activity in the left frontal and right parietal regions after exercise compared to after rest. We conclude that moderately intense cycling exercise generally does not alter emotional responding to pleasant and neutral pictures, but may reduce emotional arousal during exposure to unpleasant stimuli.

Quantitative EEG analysis in obsessive compulsive disorder.

Quantitative analysis of the EEG (q-EEG) in patients with obsessive compulsive disorder (OCD) showed a decreased beta and an increased theta power at frontotemporal regions. The patients who had higher scores in doubting test (Maudsley Obsessive Compulsive Questionnaire) and more severely ill patients shared similar q-EEG features. The relative theta powers were significantly increased and alpha powers were significantly decreased in these patients, particularly in the frontotemporal region. It was suggested that the q-EEG may be useful in investigating the OCD patients with heterogeneous characteristics.

Non-linear dynamic complexity of the human EEG during meditation.

We used non-linear analysis to investigate the dynamical properties underlying the EEG in the model of Sahaja Yoga meditation. Non-linear dimensional complexity (DCx) estimates, indicating complexity of neuronal computations, were analyzed in 20 experienced meditators during rest and meditation using 62-channel EEG. When compared to rest, the meditation was accompanied by a focused decrease of DCx estimates over midline frontal and central regions. By contrast, additionally computed linear measures exhibited the opposite direction of changes: power in the theta-1 (4-6 Hz), theta-2 (6-8 Hz) and alpha-1 (8-10 Hz) frequency bands was increased over these regions. The DCx estimates negatively correlated with theta-2 and alpha-1 and positively with beta-3 (22-30 Hz) band power. It is suggested that meditative experience, characterized by less complex dynamics of the EEG, involves 'switching off' irrelevant networks for the maintenance of focused internalized attention and inhibition of inappropriate information. Overall, the results point to the idea that dynamically changing inner experience during meditation is better indexed by a combination of non-linear and linear EEG variables.

Alpha and beta band power changes in normal and dyslexic children.

OBJECTIVE: Previous research with healthy subjects suggests that the lower alpha band reflects attentional whereas the upper alpha band semantic processes. The aim of the present study was to investigate whether dyslexics show deficits in attentional control and/or semantic encoding. METHOD: The EEG was recorded while subjects were reading numbers, words and pseudowords and analyzed in a lower and upper alpha and two beta bands (spanning a range of about 8--16 Hz). A phasic response is measured in terms of a decrease in event related band power during reading with respect to a reference interval. Tonic power is measured in terms of (log) band power during a reference interval. RESULTS: In the lower alpha band dyslexics show an increased phasic response to words and pseudowords at right hemispheric sites but a lack to respond to words at O1. The upper alpha band exhibits a highly selective phasic response to words at left frontal sites but for controls only, whereas dyslexics show a general increase in tonic upper alpha power. Whereas the low frequency beta band (beta-1a) exhibits a rather diffuse pattern, a highly selective finding was obtained for the beta-1b band. CONCLUSIONS: Dyslexics have a lack of attentional control during the encoding of words at left occipital sites and a lack of a selective topographic activation pattern during the semantic encoding of words. Because only in controls reading of words is associated with a strong beta-1b desynchronization at those recording sites which correspond to Broca's area (FC5) and the angular gyrus (CP5, P3), we may conclude that this frequency band reflects the graphemicphonetic encoding of words.

Frontal EEG response to threat, aggressive traits and a family history of alcoholism: a preliminary study.

OBJECTIVE: This study investigated the association between frontal EEG response to threat, a family history of alcoholism (positive history = FHP, negative = FHN), aggressive - antisocial traits and negative affect. METHOD: EEG in 17 FHP men and 17 FHN men was recorded while resting and while awaiting an electric shock. RESULTS: Compared with FHNs, FHPs showed significantly greater threat-induced decreases in frontal alpha, but no change in frontal beta power. FHNs had significant threat-induced increases in frontal beta power. A measure of aggressive traits, the Buss-Durkee Hostility Assault scale, was also significantly associated with greater threat-induced decreases in frontal alpha power and low reactivity to threat on frontal beta power. CONCLUSIONS: The data suggest that familial risk for alcoholism and aggressive traits may be associated with a paradoxical pattern of both increased reactivity (more alpha suppression) and decreased reactivity (no increase in beta power) to threat in frontal cortical regions. However, these results are preliminary and tentative due to limitations arising from the small sample size and the exploratory nature of this study.

Validation of a right hemisphere vigilance system as measured by principal component and factor analyzed quantitative electroencephalogram.

Arruda and colleagues [Arruda, J.E., Weiler, M.D., Valentino, D.A. et al., 1996. A guide for applying principal-component analysis and confirmatory factor analysis to qEEG data. Int. J. Psychophysiol. 23, 63-81.] recently described seven neurophysiological measures that were previously derived and confirmed using factor analytic procedures and the quantitative electroencephalogram (EEG) sampled from 208 normal controls during an auditory continuous performance test (CPT). The purpose of the present investigation was to further test the validity of these empirically derived measures by examining each measure's relationship with CPT-related declines in performance. Participants were 48 right-handed men (n = 13) and women (n = 35) who reported being free of any neurological condition, birthing complications, or loss of consciousness greater than 2 min. After completing an eyes-closed resting condition, participants performed a 23-min CPT while both quantitative EEG and behavioral performance were measured at 45, 405, 765 and 1125 s into the CPT. Bipolar recordings were gathered using the International 10-20 system, from eight sites: frontal, fronto-temporal, temporal and temporal-occipital. Multivariate and follow-up univariate tests suggest the existence of a neurophysiological system located within the right temporal region that appears essential for the maintenance of a sustained attentional state. If confirmed, the further quantification of this neurocognitive system may prove useful as part of a clinical diagnostic workup.

Alpha brainwave training and perception of time passing: preliminary findings.

The ability to generate alpha brainwaves has been associated with the self-regulation of stress. It has been suggested that generation of these brainwaves, above what is to be expected in a normal 24-hour EEG, contributes to an expanded state of consciousness. This study attempted to test Newman's theory that expansion of consciousness could be observed in perception of time passing. Twenty female college students were randomly assigned to an alpha brainwave training or beta (mock) brainwave training group. Following ten 30-minute training sessions over a five-week period of time, each subject in each group was asked to produce ten randomly assigned time intervals. Mean scores were obtained for each of the ten intervals for each group. An analysis of variance with repeated measures was used to analyze the time interval perceptions of each group. According to results obtained, both main effects and interaction effects were highly significant (p < .0001). This study offers a beginning effort to examine the consciousness altering capability of alpha brainwave generation.

[The dynamics of the dominant alpha-rhythm frequency in the perception and reproduction of time intervals]. / Dinamika dominiruiushchei chastoty al'fa-ritma pri vospriiatii i vosproizvedenii intervalov vremeni.

Dependence of the dominant alpha frequency on the processes of perception and subsequent reproduction of time intervals by rhythmic hand pressing was analysed. Two groups of subjects were separated, which demonstrated either an increase (I) or a decrease (II) in the dominant alpha frequency after the transition from perception to reproduction. In the I group 83% of the subjects reproduced time intervals with a delay. In the II group reproduction in advance was observed in 75% of the subjects. The dynamics of the dominant alpha frequency probably reflects formation of the optimal functional state underlying the individual level of activation and properties of the higher nervous activity in the subjects from both groups.