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There is trial-to-trial variability in the reaction time to stimulus presentation. Since this variability exists even in an identical stimulus condition, it reflects the internal neural dynamics of the brain. To understand the neural dynamics that influence the reaction time, we conducted an electroencephalogram (EEG) experiment in which participants were asked to press a response button as quickly as possible when a stimulus was visually presented. Phase-locking factor analysis revealed that phase resetting in two frequency bands, which appeared 0.2 s after the stimulus presentation, characterized the reaction time. The combination of the theta band phase resetting in the left parietal region and the delta band phase resetting mainly in the posterior region was associated with the fastest reaction time, whereas delta band phase resetting without theta band phase resetting was associated with the faster reaction time. The results indicated that there were frequency-dependent effects in the relationships between the EEG phase resetting and reaction time.

BACKGROUND: Noninvasive transcranial electrical stimulation (tES) research has been plagued with inconsistent effects. Recent work has suggested neuroanatomical and neurophysiological variability may alter tES efficacy. However, direct evidence is limited. OBJECTIVE: We have previously replicated effects of transcranial alternating current stimulation (tACS) on improving multitasking ability in young adults. Here, we attempt to assess whether these stimulation parameters have comparable effects in older adults (aged 60–80 years), which is a population known to have greater variability in neuroanatomy and neurophysiology. It is hypothesized that this variability in neuroanatomy and neurophysiology will be predictive of tACS efficacy. METHODS: We conducted a pre-registered study where tACS was applied above the prefrontal cortex (between electrodes F3-F4) while participants were engaged in multitasking. Participants were randomized to receive either 6-Hz (theta) tACS for 26.67 minutes daily for three days (80 minutes total; Long Exposure Theta group), 6-Hz tACS for 5.33 minutes daily (16-minutes total; Short Exposure Theta group), or 1-Hz tACS for 26.67 minutes (80 minutes total; Control group). To account for neuroanatomy, magnetic resonance imaging data was used to form individualized models of the tACS-induced electric field (EF) within the brain. To account for neurophysiology, electroencephalography data was used to identify individual peak theta frequency. RESULTS: Results indicated that only in the Long Theta group, performance change was correlated with modeled EF and peak theta frequency. Together, modeled EF and peak theta frequency accounted for 54% – 65% of the variance in tACS-related performance improvements, which sustained for a month. CONCLUSION: These results demonstrate the importance of individual differences in neuroanatomy and neurophysiology in tACS research and help account for inconsistent effects across studies.

The amygdala is a medial temporal lobe structure known to be involved in processing emotional conflict. However, its role in processing non-emotional conflict is not well understood. Previous studies have utilized the Stroop Task to examine brain modulation of humans under the color-word conflict scenario, which is non-emotional conflict processing, and found hippocampal theta-band (4-7 Hz) modulation. This study aims to survey amygdaloid theta power changes during non-emotional conflict processing using intracranial depth electrodes in nine epileptic patients (3 female; age 20-62). All patients were asked to perform a modified Stroop task. During task performance, local field potential (LFP) data was recorded from macro contacts sampled at 2 K Hz and used for analysis. Mean theta power change from baseline was compared between the incongruent and congruent task condition groups using a paired sample t-test. Seven patients were available for analysis after artifact exclusion. In five out of seven patients, statistically significant increases in theta-band power from baseline were noted during the incongruent task condition (paired sample t-test p 0.001), including one patient exhibiting theta power increases in both task conditions. Average response time was 1.07 s (failure trials) and 1.04 s (success trials). No speed-accuracy tradeoff was noted in this analysis. These findings indicate that human amygdaloid theta-band modulation may play a role in processing non-emotional conflict. It builds directly upon work suggesting that the amygdala processes emotional conflict and provides a neurophysiological mechanism for non-emotional conflict processing as well.

Dynamic visuospatial tasks, requiring continuous engagement of attention over long time periods, have been little studied with the electroencephalogram. Specifically, the role of the theta band in these tasks is unclear, with task-related theta enhancements improving performance in some studies, and hindering it in others. In this study, 30 participants performed the Pong videogame as a dynamic visuospatial task to analyze the influence of theta and alpha amplitude as well as alpha asymmetry on performance. The theta band increased significantly at central-parietal regions and correlated negatively with performance, especially at anterior regions. The alpha band showed a significant decrease, greater at right over left parietal regions, but neither the amplitude nor the asymmetry ratio correlated with performance. With theta being an indicator of top-down cognitive control, it may be concluded that proficient performance in dynamic visuospatial tasks depends on a bottom-up guidance of attention with little top-down intervention.

According to the theories of neural plasticity and neural efficiency, professional skill training improves performance by strengthening the underlying neural mechanisms. Therefore, subjects trained professionally may exhibit changes in resting-state neurophysiological characteristics closely related to performance. To test this notion, the resting-state electroencephalogram (EEG) was measured from 35 rifle shooters after the same training regimen, and resting-state EEG characteristics were analyzed for correlations with shooting performance. The results showed a significant linear correlation between shooting performance and the coherence of electrode channels C3 and T3 in the beta1 band ( r = 0.74, P −6 ). There was also a significant linear correlation between the characteristic path length of the resting-state theta band brain network and shooting performance ( r = 0.56, P

Highlights • The theta PLV in SI and contralateral SII showed variability within 2 s after the stimulus onset. • The alpha PLV showed temporal stability within 2 s after the stimulus onset. • The neural synchrony between SI and SII varied depending on the frequency band and the inter-regions., Objectives To examine the temporal stability and variability of neuronal synchronization among the contralateral primary somatosensory cortex (cSI) and contralateral (cSII) and ipsilateral secondary somatosensory cortex (iSII) in response to median nerve stimulation. Methods Both the spontaneous magnetoencephalography (MEG) signals as the pre-stimulus condition and somatosensory evoked magnetic-fields (SEF) were recorded in eleven healthy subjects. We calculated a phase-locking value (PLV) between two areas among cSI, cSII, and iSII in five frequency bands (theta: 5–7 Hz, alpha: 8–12 Hz, beta: 15–29 Hz, gamma-1: 30–59 Hz, and gamma-2: 60–90 Hz), and compared the PLV among in pre-stimulus and stimulus conditions. Results The PLV between cSI and cSII for the theta band activity varied within 2 s from the stimulus onset. On the other hand, the PLV between cSI and iSII for the alpha band did not vary within 2 s. Conclusion The fluctuation of neuronal synchrony among sensory-related cortices in response to median nerve stimulation depends on the induced frequency band and inter-region. Significance This study is the first to report the temporal characteristic of stimulus-driven neural synchrony following somatosensory stimulation.

Eight inducer subjects who were exposed to emotional visual stimuli and eight receiver subjects were participants, and at a time changed roles. Their electrical brain activity was simultaneously recorded and processed to determine the brain wave coherence, which is an estimator of brain connectivity. A t test for independent groups was used to determine if, there is a significant different outcome concerning the number and size of the brain connections for the two groups of subjects. Trained group showed a mean of difference of the EEG coherence in the brainwave theta band during exposure to visual stimuli from resting state, significantly higher than the average of the group without specific training (t (636)=2.7, p=0.007

Cognitive control involves both proactive and reactive processes. Paradigms that rely on reactive control have shown that frontoparietal oscillatory synchronization in the theta frequency band is associated with interference control. This study examines whether proactive control is also associated with connectivity in the same frontoparietal theta network or involves a distinct neural signature. A task-switching paradigm was used to differentiate between proactive and reactive control processes, involved in preparing to switch or repeat a task and resolving post-target interference, respectively. We confirm that reactive control is associated with frontoparietal theta connectivity. Importantly, we show that proactive control is also associated with theta band oscillatory synchronization but in a different frontoparietal network. These findings support the existence of distinct proactive and reactive cognitive control processes that activate different theta frontoparietal oscillatory networks.

Recent advancements in cognitive neuroscience have afforded a description of neural responses in terms of latent algorithmic operations. However, the adoption of this approach to human scalp electroencephalography (EEG) has been more limited, despite the ability of this methodology to quantify canonical neuronal processes. Here, we provide evidence that theta band activities over the midfrontal cortex appear to reflect a common computation used for realizing the need for cognitive control. Moreover, by virtue of inherent properties of field oscillations, these theta band processes may be used to communicate this need and subsequently implement such control across disparate brain regions. Thus, frontal theta is a compelling candidate mechanism by which emergent processes, such as 'cognitive control', may be biophysically realized.

Adults use different processing strategies to work with fractions. Depending on task requirements, they may analyze the fraction components separately (componential processing strategy, CPS) or consider the fraction as a whole (holistic processing strategy, HPS). It is so far unknown what is the brain coordination dynamics underlying these types of fraction processing strategies. To elucidate this issue, we analyzed oscillatory brain activity during a fraction comparison task, presenting pairs of fractions either with or without common components. Results show that CPS induces a left frontal-parietal alpha phase desynchronization after the onset of fraction pairs, while HPS induces an increase of phase synchrony on theta and gamma bands, over frontal and central-parietal sites, respectively. Additionally, the HPS evokes more negative ERPs around 400ms over the right frontal scalp than the CPS. This ERP activity correlates with the increase of Theta phase synchrony. Our results reveal the emergence of different functional neural networks depending on the kind of cognitive strategy used for processing fractions.

Visually induced motion sickness (VIMS) can occur via prolonged exposure to visual stimulation that generates the illusion of self-motion (vection). Not everyone is susceptible to VIMS and the neural mechanism underlying susceptibility is unclear. This study explored the differences of electroencephalographic (EEG) signatures between VIMS-susceptible and VIMS-resistant groups. Thirty-two-channel EEG data were recorded from 12 VIMS-susceptible and 15 VIMS-resistant university students while they were watching two patterns of moving dots: (1) a coherent rotation pattern (vection-inducing and potentially VIMS-provoking pattern), and (2) a random movement pattern (non-VIMS-provoking control). The VIMS-susceptible group exhibited a significantly larger increase in the parietal N2 response when exposed to the coherent rotating pattern than when exposed to control patterns. In members of the VIMS-resistant group, before vection onset, global connectivity from all other EEG electrodes to the right-temporal-parietal and to the right-central areas increased, whereas after vection onset the global connectivity to the right-frontal area reduced. Such changes were not observed in the susceptible group. Further, the increases in N2 amplitude and the identified phase synchronization index were significantly correlated with individual motion sickness susceptibility. Results suggest that VIMS susceptibility is associated with systematic impairment of dynamic cortical coordination as captured by the phase synchronization of cortical activities. Analyses of dynamic EEG signatures could be a means to unlock the neural mechanism of VIMS.

We sought to determine if attentional distraction in adolescents can modulate event-related desynchronization or synchronization (ERD or ERS) of the theta band during emotion regulation. Event-related theta oscillations were collected from 48 adolescents and young adults as they performed a distraction (counting) task while viewing affective pictures. Consistent with data from adult participants, positive and negative pictures elicited a larger theta ERS than did neutral pictures within a 100–400 ms window, indicating that early theta ERS is indicative of motivated attention to biologically salient stimuli. Counting as a distraction strategy attenuated early affective modulation of theta ERS. Moreover, theta ERS increased with age in the anterior regions of the brain regardless of valence; however, no age differences were found in the posterior regions. These results suggest that distraction depends on a top-down attentional mechanism that disrupts theta ERS for affective pictures at an early stage. Furthermore, adolescents undergo a developmental increase in oscillatory brain reorganization.

Mismatch negativity (MMN) is a negative component of event-related potential (ERP) that reflects auditory deviant detection. Previous studies repeatedly suggested that MMN is generated by the fronto–temporal network. However, it is still unclear how the frontal and temporal areas interact. To verify this, we observed the spatiotemporal pattern of inter-regional functional connectivity using phase synchrony and Granger causality, by analyzing event-related electroencephalograms (EEGs) elicited by standard and deviant tones in an oddball paradigm. Strong theta-band phase synchrony and bidirectional Granger causality were observed between the frontal and temporal areas during the processing of auditory deviants, especially at the temporal interval of MMN. Our results support the hypothesis that fronto–temporal interactions are crucial to the generation of MMN during auditory deviant processing.

The present study was aimed to investigate the neurological impairment of alexithymic patients. Twenty four volunteers (14 alexithymic, 10 non-alexithynic) were included in this study. All participants were asked to complete the Toronto Alexithymia Scale (TAS-20) and then took a quantitative electroencephalography (qEEG) test. Significant difference was found between the two groups (alexithymic and non-alexithymic) in terms of coherency and asymmetry. Occipital inter hemispheric coherency in alexithymic in the range of theta band was reduced. Alexithymic patients revealed increased asymmetry at occipital sites in the range of 3.5-12 Hz and 3.5-7 Hz at central sites.

According to previous results, negative emotional facial expressions elicit oscillatory beta responses The present study analyzes event-related beta oscillations upon presentation of International Affective Picture System (IAPS) and aims to show whether behavior of beta in response to negative IAPS pictures also have similar dynamics IAPS pictures (unpleasant, pleasant, and neutral) were presented as a block and random passive viewing to 14 healthy subjects (8 male). Only with pictures with similar luminance level were selected as stimuli. Event-Related Potentials (ERPs) were recorded from 30 different scalp locations, and adaptive digital filtering was used for analysis in different frequency windows. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta responses (15-30 Hz) in the 0 and 300 ms time window. Beta responses were significantly higher for unpleasant pictures than for pleasant and neutral pictures (average 50%). Beta responses were significantly higher for unpleasant than for pleasant pictures over frontal, central and parietal electrode sides (p < 0.05). Furthermore, beta responses were significantly higher for unpleasant than for neutral pictures over parietal and occipital electrodes (p < 0 04) In addition, the pleasant pictures elicited higher beta responses than neutral pictures over occipital electrode sites (p < 0 04) The results of the present study indicate that negative emotions are related to increased beta responses in humans, independent of stimulus types (facial expression or IAPS pictures) Accordingly, beta responses to negative emotions are possibly a common phenomenon The standardization of luminance in pictures may reduce divergences between results from different laboratories (C) 2010 Elsevier Ireland Ltd All rights reserved.

Objective Disruption of the sense of agency and of being causally determinant in action was explored in the present research by inducing an erroneous external spatial feedback in response to the subject’s behaviour. Methods ERPs and theta frequency band oscillation (ERD) were recorded from 15 subjects when they were receiving mismatching/matching feedback information. In addition, subjective sensitivity to the external cues was monitored by BIS (Behavioral Inibition System) and BAS (Behavioral Activation System) measures. Results One negative ERP deflection of higher amplitude was revealed in response to false feedback, peaking at 210 ms post-stimulus, central-posteriorly localized. A specific cortical network, more central-posteriorly distributed, seems to be implicated. Moreover, theta synchronization was observed in response to false feedback within the posterior cortical site. Conclusions A direct relationship between ERP/theta band oscillation was supposed, as a marker of salient and unattended cues that produce an alerting response. Moreover, BIS showed an enhanced response to external feedback, and specifically to false feedback, with an increased negative deflection and theta frequency band effect. Significance ERP negativity may represent a monitoring system, comparable with erroneous feedback effect. Moreover, specific motivation towards negative context was related to higher BIS, since they were more sensitive to negative, false outcome.

The brain network between healthy individuals and patients suffering from epileptiform discharges was compared to investigate whether or not the brain network of patients with epileptiform discharges resembles a small world network. The EEG (19 channels) of the healthy subjects and patients were recorded during a state of relaxation. Segments of 2 s during the eyes closed were analyzed in the healthy individuals’ EEG. In the patients’ EEG, segments of two seconds were analyzed during epileptiform discharge. Wavelet-crosscorrelation analysis was used to obtain wavelet-crosscorrelation coefficients (WCC). WCC was calculated in the alpha bandwidth (non-discharge), and the theta band (discharge). Three network parameters were calculated: the shortest path length, the global efficiency, and the clustering coefficient. The results in the theta band showed that the shortest path length during discharge in the patients was significantly lower than non-discharge and healthy individuals. Both the clustering coefficient and global efficiency in the patients during discharge were significantly higher than non-discharge and healthy subjects. No significant results were found in the alpha band. These results suggest that the network in the brain of patients during a discharge could be more resembling to a small world network.

We analyze the pattern of inter-regional functional association between cortical activities during auditory oddball tasks, and the influence of task difficulty on it. Event-related electroencephalograms were recorded from 17 subjects during auditory oddball tasks with two task difficulty levels. The task difficulty was controlled by changing the difference between the frequencies of standard and target tones. The changes in behavioral response and P300 component due to the difficulty were consistent with previous findings, whereby successful control of difficulty was verified. Significant gamma- and theta-band phase synchronization (PS) was observed primarily between frontal and posterior electrodes along the midline, which is interpreted as functional connectivity among cortical regions devoted to the task execution. Apparent differences in PS were identified between two difficulties in both gamma- and theta-bands. On the whole, the number of electrode pairs showing significant PS was much smaller for higher task difficulty. The overall result is in agreement with our recent study which reported similar difference in PS due to the difficulty of 'visual' oddball task.

When participants in a gambling game are given feedback as to whether they won or lost the previous bet, a series of stereotypical brain electrical responses can be observed in the electroencephalogram (EEG) and the stimulus-locked Event-Related Potential (ERP). These include the Feedback-Related Mediofrontal Negativity (FRN), a posterior P300, and a feedback-induced increase in power at the theta (4 to 8 Hz) band over frontal scalp. Although the generators of the FRN and P300 have been studied previously, little is known about the generator of feedback-induced theta. We employed a gambling game in which participants chose either high-risk/high-reward or low-risk/low-reward bets to investigate these feedback-related responses. The FRN was not modulated by the riskiness of the bet, but both P300 and feedback-induced theta were of greater amplitude following high- relative to low-risk bets. Using a bilateral multi-source Beamformer approach, we localized the induced theta-band responses following wins and losses to partially overlapping regions in the right medial frontal cortex, possibly including the Anterior Cingulate. Using a dipole-fitting approach, we found that the generators of feedback-induced theta are anatomically distinct from those of the FRN and P300.

Objective and hypothesis Nonlinear and linear methods of EEG-complexity analysis and autonomic measures were used to characterize processes accompanying performance in a mental arithmetic task challenged by low (“social”) alcohol doses. It was expected that alcohol in such doses will dampen changes of task-related EEG-synchronization in the theta band, and those of heart rate and electrodermal activity (EDA). Methods In the mental arithmetic task addition and working memory, effort was required. The EEG, ECG and EDA were recorded in 5 conditions: task, placebo-task, low dose-task (0.2 g/kg alcohol), high dose-task (0.4 g/kg alcohol). Omega-complexity and synchronization likelihood (SL) were computed of the theta band of the EEG. Results Task-related decrease of the Omega-complexity and increase of the SL was found in the theta frequency band. Following alcohol consumption, these changes did not develop as seen especially for SL in the anterior area, although the significant effects were elicited by task performance. Conspicuous task-evoked increases were observed for ECG and EDA which were even more enhanced by alcohol. Conclusions Task-induced significant changes of the Omega-complexity and that of SL indicate increased synchrony in the theta band, probably corresponding to working memory effort. Both of these measures proved to be sensitive for the effect of low alcohol dose although these alcohol-elicited changes were not statistically significant. Task-induced heart rate and EDA increases were further intensified by alcohol probably indicating its activating effect on these autonomic measures in the dose range studied.

Our recent functional MRI and event-related potential studies suggest that neural mechanisms underlying identifications of environmental and personal risks are characterized by distinct neural structures and time courses. The current work further investigated the role of non-phase locked activity in dissociation of the neural processes of environmental and personal risks. We recorded electroencephalogram (EEG) from healthy adults when they identified risky and safe environmental or personal events depicted in words or phrases. Event-related synchronization (ERS) and desynchronization (ERD) in association with risky and safe environmental and personal events were calculated using Morlet's wavelet analysis. We found that, relative to the identification of safe environmental events, the identification of risky environmental events induced increased theta band power at 260–380 ms over the frontal cortex and increased alpha band power after 700 ms with a wide scalp distribution. Moreover, theta band powers associated with the identification of risky environmental events correlated positively with subjective ratings of the risk degree of environmental events. In contrast, the identification of risky personal events was linked to decreased alpha band power at 740–900 ms with a wide scalp distribution compared with the identification of safe personal events. Our findings indicate that theta and alpha band neural oscillations are involved in differentiation between environmental and personal risks.

The phonological deficit hypothesis of dyslexia has been investigated in the present research by analysing language-related lateralization of the EEG theta band in a sample of dyslexic children. To this aim, a paradigm based on word-pair visual presentation was used in which the same words were processed in Semantic and Phonological tasks. Theta band amplitude, a cortical index that has been related to working memory processing, was analysed during four different phases of word elaboration, thus allowing to measure also the temporal dynamics of word reading/encoding in the verbal working memory. Control subjects showed a specific (and therefore efficient) task-related and time-dependent cortical activation: a peak of theta activity during word reading was found that decayed during the next inter stimulus interval. Furthermore, during word presentation in the Phonological task, theta amplitude was greater on the left hemisphere. Dyslexics evidenced an altered pattern of theta activation both in the temporal dimension and in the cortical space: their peak of activity was delayed to the first inter stimulus interval after word offset and was shifted to the right hemisphere throughout the whole epoch of Phonological task and in two phases of the Semantic task. Analysis of alpha band failed to replicate the complex pattern of lateralization found for theta band in the two groups, a result that suggests a specific functional role of theta band, which cannot be interpreted as a simple marker of cortical inhibition. Results point to a deficit, in dyslexic children, to recruit left hemisphere structures for the elaboration of the phonological component of the verbal working memory. This deficit was marked by a different, unspecific and dysfunctional hemispherical asymmetry of theta activation to language, a deficit that involved also the time course of phonological linguistic elaboration.

Episodic memories consist of semantic information coupled with a rich array of contextual detail. Here, we investigate the neural processes by which information about the sensory context of a learning event is "bound" to the semantic representation of the to-be-encoded item. We present evidence that item-context binding during encoding is mediated by frontoposterior electroencephalographic (EEG) phase locking within and between hemispheres in the theta (4-8 Hz) band. During a task in which subjects encoded words in different font colors, later memory for the word was associated with sustained frontal theta activity and frontoposterior theta-band coherence, primarily within the left hemisphere. When the word-color association was later successfully retrieved, however, neurons synchronized their theta-band responses bilaterally in a more sustained fashion, particularly during the latter part of the stimulus epoch (>800 ms). Our results confirm the importance of functional coupling between frontal and posterior regions for successful encoding. One interpretation of these data is hemispheric contributions to item and context encoding may be asymmetric, with left hemisphere coherence facilitating semantic processing of an item and right hemisphere coherence facilitating processing of sensory context. Theta-band coherence may be an important mechanism by which brain networks exchange information during learning.

The aim of this study was to investigate the conflicting results in event-related desynchronization/synchronization (Pfurtscheller, 1999) in the upper alpha and theta bands related to intelligence. Two groups of individuals (high intelligent M IQ =128, and average intelligent M IQ =93), solved two memory tasks while their EEG was recorded. The data were analyzed with the ERD/ERS method and low resolution brain electromagnetic tomography (LORETA). In the upper alpha band high intelligent individuals displayed more desynchronization than did average intelligent individuals. In the theta band a minor but reverse effect was observed. The LORETA analysis indicated that average intelligent individuals displayed much higher signal to noise ratios (SNR) than did high intelligent individuals. The EEG source location for the high intelligent group was more anterior, whereas for the average intelligent group a more posterior EEG source location was observed. The findings were explained in the light of the neural efficiency model.

Event-related desynchronization (ERD) and synchronization (ERS) in the theta frequency band was measured while subjects viewed stimuli with differing emotional content (from the International Affective Picture System). A significant valence by hemisphere interaction emerged only in the anterior temporal regions, showing relatively greater right hemisphere ERS for negative and left hemisphere ERS for positive stimuli. In turn, in the posterior brain regions affectively valenced vs neutral stimuli prompted larger extent of ERS against the background of the overall right hemisphere dominance in theta synchronization. The findings document that valence discrimination is associated with the early (200–500 ms poststimulus) time-locked synchronized theta activity as well as hemispheric asymmetries in anterior-posterior direction.

Recent research indicates that an increase in theta band power is related to episodic memory performance. In this study with human subjects, the evoked (time locked) and induced (not time locked) theta response is analyzed in a recognition task. The results show a strong evoked theta response during an early retrieval period of up to 400 ms. Only for good memory performers theta is strictly time locked, indicating that theta peaks appear in preferred time windows after a target is presented. This effect – which coincides with a large P3 – suggests that good performance requires a strict timing of different processing stages that correspond to cycles of theta activity.

In previous papers we have proposed that in patients with space-occupying lesions, delta power was related with the volume of the lesion and theta power with the volume of the edema. In this report we analyze the evolution of 10 patients with space-occupying lesions in whom we measured the volume of the lesion and of the edema before and after treatment that produced changes in these volumes. EEGs were recorded in the leads of the 10-20 system referenced to linked earlobes. Delta and theta powers were calculated for voltage and current source densities (CSD) and compared with age-norms to compute conventional Z-maps. These maps provide probability statements about the deviation of observed values from the norm. Rank correlations between the change in the volume of the lesion before and after treatment and the change in Z-values before and after treatment were significant only in the delta band. However, rank correlations between the change in the volume of the edema and the change in EEG Z-values were only significant in the theta band. These correlations were higher for CSD than for voltage estimates. We also observed that the site of the lesion and of the edema was better represented by CSD maps than by voltage maps. These results are also in agreement with our previous reports, in which we observed more precise localization of brain lesions by CSD than by voltage estimates.

The objective of this study was to develop a method of measuring arousal level by examining the change rates with activation of the alpha band amplitude using the concept of the inverted U-shaped pattern of transition of this amplitude. We investigated change rates by inspecting the electroencephalogram, and we evaluated their correlations with a criterion index of the arousal level (a reaction time measure), and other relevant basic parameters in 14 normal volunteers. In order to confirm that alpha band amplitude change followed an inverted U-shaped curve, we examined the transition of that index in a resting-and-relaxing condition. In the third session, the change rates upon stimulation and after resting had positive and negative correlations, respectively, with the reaction time measure, verifying that they are 'negative' and 'positive' arousal level indices. Further examinations were conducted for the third session. The change rates upon stimulation and after resting had negative correlations with each other. Neither of them had a significant correlation with the alpha band amplitude. Neither alpha band frequency, alpha band amplitude, or theta band amplitude, all of which are regarded as indices for intra-subject arousal level transition, had any significant correlation with the reaction time measure. These results revealed that the change rates of the alpha band amplitude are better indices for inter-individual arousal level variation than other conventional indices.

In order to find EEG parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were realized in connection with isometric contractions (IMC). IMC were performed with submaximal and maximal subjective effort. Mean spectral power density within the theta band was found as an indicator for maximal subjective effort. The theta power across the parieto-occipital area decreases from rest through movements performed with submaximal force to movements performed with maximal effort. It is argued that this theta decrease possibly reflects a down-regulation of the posterior attention system in order to minimize the influences of external stimuli during the preparation for voluntary IMC performed with maximal subjective effort.

The age effect on coherence has been studied in control (98) and learning-disabled (LD, 54) school-aged children (from 6.0 to 16.8 years old). The EEG recordings were made at rest in 15 leads, and 105 pairwise combinations for coherence were calculated (each lead was compared with all the rest) for delta, theta, alpha, beta and total frequency bands. A significant increase of coherence with age was found in both groups, witha different pattern of maturation. In the control group, a significant increase with age was found in the coherences between posterior regions and vertex (Cz). A significant decrease with age in the coherence between frontal areas was observed, especially in the theta band. The LD group showed a different pattern: no significant relation with age was found in the coherence between any lead and vertex. A high effect of age on coherence between temporal regions was observed with a predominance of the left side in comparison with the contralateral and the ipsilateral. No decrease in frontal coherence was found: in the same region where the control group showed negative values with age, the LD groups had no age effect. The results obtained are discussed as differences in brain organization, in myelogenesis and synaptogenesis and an explanation of the etiology of LD is proposed.

Brain maturation at early stages may be assessed by changes in electroencephalographic connectivity (Grieve et al., 2008). We determined the differences in brain maturation between infants born at different gestational age (GA) by comparing connectivity measures obtained at comparable post-conceptional age. Electroencephalogram was recorded on twenty-six infants (23–35 weeks GA) at 35 post-conceptional weeks. Infants were divided in groups according to GA: 23–27 (ELGA), 28–32 (VLGA) and 34–35 (LGA) weeks. Data were recorded on Fp1, Fp2, Fz, C3, Cz, C4, T3, T4, O1 and O2 channels referred to linked mastoids and transformed into the frequency domain using a Fast Fourier Transformation algorithm. A single- subject-connectivity-matrix approach was used to obtain measures of global/local connectivity (clustering coefficients, strength and modularity) in delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz) and beta (13–30 Hz) bands. Functional connectivity measures were compared between subgroups. A greater mean coherence strength of the theta band of the right hemisphere in LGA compared with ELGA (p = .006) were found. The comparison at the same post- conceptional age of infants born at different gestational weeks allowed to emerge early differences in brain electrical activity suggesting altered developmental trajectories for premature infants born at lower gestational ages.

Amphetamine injection (2.5 mg/kg, SC) produced a significant quadratic trend in mean peak EEG frequencies in the theta band in one group of rats. Progressive increases in peak EEG frequencies occurred for approximately 30 min after amphetamine injection and were followed by progressive decreases through 100 min. These changes in peak EEG frequencies may have reflected pharmacokinetic properties of amphetamine. A significant and similar quadratic trend was seen in mean motor activity counts after amphetamine injection in a second group of rats. In addition, a significant positive correlation was found between amphetamine-induced effects on peak EEG frequencies and mean motor activity counts.

We have recently shown that electroencephalogram (EEG) coherence data recorded with common reference methods, including those obtained from schizophrenics, are confounded by power and phase effects. Three published reports using bipolar recordings found that EEG coherence was higher in schizophrenics; however, only medicated patients were studied. To extend these findings, we measured EEG coherence from bipolar EEG recordings in unmedicated schizophrenics (n = 10), affective disorder patients (n = 8), and normal controls (n = 13) during resting and task conditions. Seven schizophrenics were restudied after a period of neuroleptic treatment. Schizophrenics had higher across-task interhemispheric (p less than 0.05) and intrahemispheric (p less than 0.04) coherence in the theta band and tended to have higher intrahemispheric alpha coherence (p less than 0.08). Medication treatment was associated with clinical improvement and increases in spectral power, but not with changes in coherence values. These results confirm those obtained by earlier investigations and suggest that increased coherence reflects the presence of anomalous cortical organization in schizophrenics rather than medication effects or transient states related to acute clinical disturbance.

According to motivational intensity theory, effort is proportional to the level of task demand provided that success is possible and successful performance is deemed worthwhile. The current study represents a simultaneous manipulation of demand (working memory load) and success importance (financial incentive) to investigate neurophysiological (EEG) and cardiovascular measures of effort. A 2 × 2 repeated-measures study was conducted where 18 participants performed a n-back task under three conditions of demand: easy (1-back), hard (4-back) and very hard (7-back). In addition, participants performed these tasks in the presence of performance-contingent financial incentive or in a no-incentive (pilot trial) condition. Three bands of EEG activity were quantified: theta (4–7 Hz), lower-alpha (7.5–10 Hz) and upper-alpha (10.5–13 Hz). Fronto-medial activity in the theta band and activity in the upper-alpha band at frontal, central and parietal sites were sensitive to demand and indicated greatest effort when the task was challenging and success was possible. Mean systolic blood pressure and activity in the lower-alpha band at parietal sites were also sensitive to demand but also increased in the incentive condition across all levels of task demand. The results of the study largely support the predictions of motivational intensity using neurophysiological markers of effort.