Poststroke QEEG informs early prognostication of cognitive impairment

Cognitive impairment is a common consequence of stroke, but remains difficult to predict. We investigate the ability of early QEEG assessment to inform such prediction, using binary logistic regression. Thirty‐five patients (12 female, ages 18–87) suffering middle cerebral artery, ischemic stroke were studied. Resting‐state EEG was recorded 48–239 h after symptom onset. Relative power for delta, theta, alpha, and beta bands, delta:alpha ratio, and peak alpha frequency were analyzed. Montreal Cognitive Assessment (MoCA) was administered, where possible, on day of EEG and at median 99 days (range 69–138) poststroke. Eight patients could not complete the baseline MoCA, and four the follow‐up MoCA, for varying reasons (most commonly, stroke symptoms). Fifteen patients (48%) had cognitive impairment (MoCA score ≤25) at follow‐up. One QEEG index was able to correctly predict presence/absence of cognitive impairment in 24/31 patients (77.4%), whereas predischarge MoCA did so in 23 patients. This index, relative theta frequency (4–7.5 Hz) power, was computed from only three posterior electrodes over the stroke‐affected hemisphere. Its predictive accuracy (three electrodes) was higher than that of any “global” QEEG measure (averaged over 19 electrodes). These results may signify association between poststroke alpha slowing and cognitive impairment, which may be mediated by attentional (dys)function, which warrants further investigation. Pending further studies, QEEG measure(s)—from a few electrodes—could inform early prognostication of poststroke cognitive outcomes (and clinical decisions), particularly when cognitive function cannot be adequately assessed (due to symptoms, language, or other issues) or when assessment is equivocal.     

Electrophysiological analysis of a sensorimotor integration task

The present experiment aimed at investigating electrophysiologic changes observed as beta band asymmetry, by Quantitative Electroencephalography (qEEG), when individuals performed a reaching motor task (catching a ball in free fall). The sample was composed of 23 healthy individuals, of both sexes, with ages varying between 25 and 40 years old. All the subjects were right handed. A two-way ANOVA was applied for the statistical analysis, to verify the interaction between task moment (i.e., 2 s before and 2 s after ball's fall) and electrode (i.e., frontal, central and temporal regions). The first analysis compared electrodes placed over the somatosensory cortex. Central sites (C3–C4) were compared with temporal regions (T3–T4). The results showed a main effect for moment and position. The second analysis was focused over the premotor cortex, which was represented by the electrodes placed on the frontal sites (F3–F4 versus F7–F8), and a main effect was observed for position. Taken together, these results show a pattern of asymmetry in the somatosensory cortex, associated with a preparatory mechanism when individuals have to catch an object during free fall. With respect to task moment, after the ball's fall, the asymmetry was reduced. Moreover, the difference in asymmetry between the observed regions were related to a supposed specialization of areas (i.e., temporal and central). The temporal region was associated with cognitive processes involved in the motor action (i.e., explicit knowledge). On the other hand, the central sites were related to the motor control mechanisms per se (i.e., implicit knowledge). The premotor cortex, represented by two frontal regions (i.e., F3–F4 versus F7–F8), showed a decrease on neural activity in the contralateral hemisphere (i.e., to the right hand). This result is in agreement with other experiments suggesting a participation of the frontal cortex in the planning of the apprehension task. This sensorimotor paradigm may contribute to the repertoire of tasks used to study clinical conditions such as depression, alzheimer and Parkinson diseases.     

Induced EEG alpha oscillations are related to mental rotation ability: The evidence for neural efficiency and serial processing

People with better skills in mental rotation require less time to decide about the identity of rotated images. In the present study, alphanumeric characters rotated in the frontal plane were employed to assess the relationship between rotation ability and EEG oscillatory activity. Response latency, a single valid index of performance in this task, was significantly associated with the amplitude of induced oscillations in the alpha (8–13 Hz) and the low beta band (14–20 Hz). In accordance with the neural efficiency hypothesis, less event-related desynchronization (ERD) was related to better (i.e. faster) task performance. The association between response time and ERD was observed earlier (∼600–400 ms before the response) over the parietal cortex and later (∼400–200 ms before the response) over the frontal cortex. Linear mixed-effect regression analysis confirmed that both early parietal and late frontal alpha/beta power provided significant contribution to prediction of response latency. The result indicates that two distinct serially engaged neurocognitive processes comparably contribute to mental rotation ability. In addition, we found that mental rotation-related negativity, a slow event-related potential recorded over the posterior cortex, was unrelated to the asymmetry of alpha amplitude modulation.     

Resting posterior versus frontal delta/theta EEG activity is associated with extraversion and the COMT VALMET polymorphism

Recent studies suggest that resting posterior versus frontal EEG delta/theta activity (delta/theta Pz–Fz) is both sensitive to pharmacological manipulations of neural dopamine and associated with the agency facet of extraversion (i.e., a motivational disposition comprising enthusiasm, energy, assertiveness, achievement striving and social dominance). These observations suggest that posterior versus frontal resting EEG delta/theta activity may represent a useful marker for investigating the molecular genetic basis of extraversion. The present study aimed to test the novel hypothesis of an association between delta/theta Pz–Fz and a functional polymorphism of the enzyme catechol-O-methyltransferase (COMT VAL¹⁵⁸MET) involved in dopamine catabolism. This was conducted in a large EEG data set from the Brain Resource International Database (BRID; resting EEG from N = 1093 healthy individuals, 382 of which also genotyped for COMT VAL¹⁵⁸MET). In summary, we (1) showed for the first time that the VAL allele is associated with increased delta/theta Pz–Fz; (2) replicated the association between extraversion and delta/theta Pz–Fz in a large, heterogeneous sample including both genders; and (3) documented that the VAL allele of the COMT VAL¹⁵⁸MET is associated with increased extraversion scores, as previously reported for an overlapping BRID sample. This coherent pattern of findings adds further support to the suggestion that the posterior–anterior distribution of resting EEG slow wave activity in the delta/theta range represents a useful tool for probing the dopaminergic basis of extraversion.     

Age-dependent features of EEG-reactivity—Spectral,complexity, and network characteristics

Our goal was to measure indices characterizing EEG-reactivity in young and elderly subjects. It was hypothesized that EEG-reactivity as reflected by different measures would be lower in the elderly. In two age groups (young: N = 23, mean age = 21.5 ± 2.2 years; old: N = 25, mean age = 66.9 ± 3.6 years) absolute frequency spectra, Omega-complexity, synchronization likelihood and network properties (clustering coefficient and characteristic path length) of the EEG were analyzed in the delta, theta, alpha1, alpha2, beta1 and beta2 frequency bands occurring as a result of eyes opening. Absolute spectral power was higher in the young in the delta, alpha1 and alpha2 bands in the posterior area. The alpha1 peak frequency decreased following eyes opening in the young, while no change was observed in the elderly. Omega-complexity was higher in the elderly especially in the frontal area and increased following eyes opening. Values of the clustering coefficient, path length and that of the “small-world index” decreased as a result of eyes opening, the latter in the fast frequency range. The results suggest reduced reactivity in the elderly as shown by frequency spectra and decreased level of integrative activity particularly in the frontal area probably as a result of reduced interneuronal processing capacity. Indices of network characteristics reveal a shift towards more random topology especially in the beta frequencies caused by eyes opening.     

EEG activity in Carmelite nuns during a mystical experience

Mystical experiences relate to a fundamental dimension of human existence. These experiences, which are characterized by a sense of union with God, are commonly reported across all cultures. To date, no electroencephalography (EEG) study has been conducted to identify the neuroelectrical correlates of such experiences. The main objective of this study was to measure EEG spectral power and coherence in 14 Carmelite nuns during a mystical experience. EEG activity was recorded from 19 scalp locations during a resting state, a control condition and a mystical condition. In the mystical condition compared to control condition, electrode sites showed greater theta power at F3, C3, P3, Fz, Cz and Pz, and greater gamma1 power was detected at T4 and P4. Higher delta/beta ratio, theta/alpha ratio and theta/beta ratio were found for several electrode sites. In addition, FP1–C3 pair of electrodes displayed greater coherence for theta band while F4–P4, F4–T6, F8–T6 and C4–P4 pairs of electrodes showed greater coherence for alpha band. These results indicate that mystical experiences are mediated by marked changes in EEG power and coherence. These changes implicate several cortical areas of the brain in both hemispheres.     

Effects of methylphenidate on quantitative EEG of boys with attention-deficit hyperactivity disorder in continuous performance test

The purpose of this study was to investigate the effects of methylphenidate, a psychostimulant, on quantitative electroencephalography (QEEG) during the continuous performance test (CPT) in boys with attention-deficit hyperactivity disorder (ADHD). The QEEG was obtained from 20 boys with ADHD. The amplitudes of 4 bands (alpha, beta, delta, and theta) in the QEEG, as well as the theta /beta ratio, before and after the administration of methylphenidate were compared during both the resting and CPT states. Methylphenidate induced a significant increase of alpha activities in both the right and left frontal and occipital areas, an increase of beta activities in almost all areas except for the temporal region, a decrease of theta activities in both the occipital and right temporo-parietal areas, a mild decrease of delta activities in the occipito-parietal areas, and an increase of the theta/beta ratio in the right frontal and parieto-occipital, and left temporal areas during the CPT state. No significant QEEG changes were induced by the administration of methylphenidate in the resting state. These data suggest that methylphenidate has greater electrophysiological influences on the cerebral topographical activities during the performance of attentional tasks, as compared to the resting state, in boys with ADHD.     

Fluctuations between sleep and wakefulness: Wake-like features indicated by increased EEG alpha power during different sleep stages in nightmare disorder

Although a growing body of research indicates that frequent nightmares are related to impaired sleep regulation, the pathophysiology of nightmare disorder is far from being fully understood. We examined the relative spectral power values for NREM and REM sleep separately in 19 individuals with nightmare disorder and 21 healthy controls, based on polysomnographic recordings of the second nights’ laboratory sleep. Nightmare subjects compared to controls exhibited increased relative high alpha (10–14.5 Hz) and fronto-central increases in high delta (3–4 Hz) power during REM sleep, and a trend of increased fronto-central low alpha (7.75–9 Hz) power in NREM sleep. These differences were independent of the confounding effects of waking emotional distress. High REM alpha and low NREM alpha powers were strongly related in nightmare but not in control subjects. The topographical distribution and spectral components of REM alpha activity suggest that nightmare disordered subjects are characterized by wake-like electroencephalographic features during REM sleep.     

Early changes of microRNAs expression in the dorsal root ganglia following rat sciatic nerve transection

Abnormal baseline brain functional connectivity in attention-deficit/hyperactivity disorder (ADHD) has been revealed in a number of studies by using resting-state functional MRI (rfMRI). The aim of this study was to investigate the spontaneous frontal activities in medication-naïve ADHD boys using the rfMRI derived index, amplitude of low-frequency fluctuation (ALFF). In total 17 ADHD boys and 17 matched controls were recruited to undergo rfMRI scan on a 3.0 T MRI system. For each subject, six oblique slices covering the frontal areas were acquired with a rapid sampling rate (TR = 400 ms). Functional images were processed in AFNI for calculation of ALFF and then group comparison was performed using voxel-based t-test. With a corrected threshold of p < 0.05 determined by AlphaSim, we found that in comparison with controls, ADHD patients demonstrated higher ALFF values in the left superior frontal gyrus and sensorimotor cortex (SMC), and lower ALFF values in the bilateral anterior, middle cingulate and the right middle frontal gyrus (MFG). Significant correlations were found between patients’ WSCT measures and the peak ALFF located in the right MFG (r = 0.69, p = 0.02), and the left SMC (r = 0.65, p = 0.03). Our results revealed abnormal frontal activities at resting state associated with underlying physiopathology of ADHD, and suggested the ALFF analysis to be a potential approach in further exploration of this disorder.     

A comprehensive neuropsychological mapping battery for functional magnetic resonance imaging

Existing batteries for FMRI do not precisely meet the criteria for comprehensive mapping of cognitive functions within minimum data acquisition times using standard scanners and head coils. The goal was to develop a battery of neuropsychological paradigms for FMRI that can also be used in other brain imaging techniques and behavioural research. Participants were 61 healthy, young adult volunteers (48 females and 13 males, mean age: 22.25 ± 3.39 years) from the university community. The battery included 8 paradigms for basic (visual, auditory, sensory-motor, emotional arousal) and complex (language, working memory, inhibition/interference control, learning) cognitive functions. Imaging was performed using standard functional imaging capabilities (1.5-T MR scanner, standard head coil). Structural and functional data series were analysed using Brain Voyager QX2.9 and Statistical Parametric Mapping-8. For basic processes, activation centres for individuals were within a distance of 3–11 mm of the group centres of the target regions and for complex cognitive processes, between 7 mm and 15 mm. Based on fixed-effect and random-effects analyses, the distance between the activation centres was 0–4 mm. There was spatial variability between individual cases; however, as shown by the distances between the centres found with fixed-effect and random-effects analyses, the coordinates for individual cases can be used to represent those of the group. The findings show that the neuropsychological brain mapping battery described here can be used in basic science studies that investigate the relationship of the brain to the mind and also as functional localiser in clinical studies for diagnosis, follow-up and pre-surgical mapping.     

The concentrations of serum, plasma and platelet BDNF are all increased by treadmill VO₂max performance in healthy college men

An important question in healthcare for older patients is whether age-related changes in cortical reorganization can be measured with advancing age. This study investigated the factors behind such age-related changes, using time-frequency analysis of event-related potentials (ERPs). We hypothesized that brain rhythms was affected by age-related changes, which could be reflected in the ERP indices. An oddball task was conducted in two experimental groups, namely young participants (N = 15; mean age 23.7 ± 2.8 years) and older participants (N = 15; mean age 70.1 ± 7.9 years). Two types of stimuli were used: the target (1 kHz frequency) and standard (2 kHz frequency). We scrutinized three ERP indices: event-related spectral power (ERPSP), inter-trial phase-locking (ITPL), and event-related cross-phase coherence (ERPCOH). Both groups performed equally well for correct response rate. However, the results revealed a statistically significant age difference for inter-trial comparison. Compared with the young, the older participants showed the following age-related changes: (a) power activity decreased; however, an increase was found only in the late (P3, 280-450 ms) theta (4-7 Hz) component over the bilateral frontal and temporo-frontal areas; (b) low phase-locking in the early (N1, 80-140 ms) theta band over the parietal/frontal (right) regions appeared; (c) the functional connections decreased in the alpha (7-13 Hz) and beta (13-30 Hz) bands, but no difference emerged in the theta band between the two groups. These results indicate that age-related changes in task-specific brain activity for a normal aging population can be depicted using the three ERP indices.     

Brain wave synchronization and entrainment to periodic acoustic stimuli

As known, different brainwave frequencies show synchronies related to different perceptual, motor or cognitive states. Brainwaves have also been shown to synchronize with external stimuli with repetition rates of ca. 10–40 Hz. However, not much is known about responses to periodic auditory stimuli with periodicities found in human rhythmic behavior (i.e. 0.5–5 Hz). In an EEG study we compared responses to periodic stimulations (drum sounds and clicks with repetition rates of 1–8 Hz), silence, and random noise. Here we report inter-trial coherence measures taken at the Cz-electrode that show a significant increase in brainwave synchronization following periodic stimulation. Specifically, we found (1) a tonic synchronization response in the delta range with a maximum response at 2 Hz, (2) a phasic response covering the theta range, and (3) an augmented phase synchronization throughout the beta/gamma range (13–44 Hz) produced through increased activity in the lower gamma range and modulated by the stimulus periodicity. Periodic auditory stimulation produces a mixture of evoked and induced, rate-specific and rate-independent increases in stimulus related brainwave synchronization that are likely to affect various cognitive functions. The synchronization responses in the delta range may form part of the neurophysiological processes underlying time coupling between rhythmic sensory input and motor output; the tonic 2 Hz maximum corresponds to the optimal tempo identified in listening, tapping synchronization, and event-interval discrimination experiments. In addition, synchronization effects in the beta and gamma range may contribute to the reported influences of rhythmic entrainment on cognitive functions involved in learning and memory tasks.     

Steady-State Visual Evoked Potentials: Distributed Local Sources and Wave-Like Dynamics Are Sensitive to Flicker Frequency

Summary: Steady-state visual evoked potentials (SSVEPs) are used in cognitive and clinical studies of brain function because of excellent signal-to-noise ratios and relative immunity to artifacts. SSVEPs also provide a means to characterize preferred frequencies of neocortical dynamic processes. In this study, SSVEPs were recorded with 110 electrodes while subjects viewed random dot patterns flickered between 3 and 30 Hz. Peaks in SSVEP power were observed at delta (3 Hz), lower alpha (7 and 8 Hz), and upper alpha band (12 and 13 Hz) frequencies; the spatial distribution of SSVEP power is also strongly dependent on the input frequency suggesting cortical resonances. We characterized the cortical sources that generate SSVEPs at different input frequencies by applying surface Laplacians and spatial spectral analysis. Laplacian SSVEPs recorded are sensitive to small changes (1–2 Hz) in the input frequency at occipital and parietal electrodes indicating distinct local sources. At 10 Hz, local source activity occurs in multiple cortical regions; Laplacian SSVEPs are also observed in lateral frontal electrodes. Laplacian SSVEPs are negligible at many frontal electrodes that elicit strong potential SSVEPs at delta, lower alpha, and upper alpha bands. One-dimensional (anterior-posterior) spatial spectra indicate that distinct large-scale source distributions contribute SSVEP power in these frequency bands. In the upper alpha band, spatial spectra indicate the presence of long-wavelength (> 15 cm) traveling waves propagating from occipital to prefrontal electrodes. In the delta and lower alpha band, spatial spectra indicate that long-wavelength source distributions over posterior and anterior regions form standing-wave patterns. These results suggest that the SSVEP is generated by both (relatively stationary) localized sources and distributed sources that exhibit characteristics of wave phenomena. This research was supported by NIMH grant R01-68004.     

Auditory event-related potentials and alpha oscillations in the psychosis prodrome: Neuronal generator patterns during a novelty oddball task

Prior research suggests that event-related potentials (ERP) obtained during active and passive auditory paradigms, which have demonstrated abnormal neurocognitive function in schizophrenia, may provide helpful tools in predicting transition to psychosis. In addition to ERP measures, reduced modulations of EEG alpha, reflecting top-down control required to inhibit irrelevant information, have revealed attentional deficits in schizophrenia and its prodromal stage. Employing a three-stimulus novelty oddball task, nose-referenced 48-channel ERPs were recorded from 22 clinical high-risk (CHR) patients and 20 healthy controls detecting target tones (12% probability, 500 Hz; button press) among nontargets (76%, 350 Hz) and novel sounds (12%). After current source density (CSD) transformation of EEG epochs (− 200 to 1000 ms), event-related spectral perturbations were obtained for each site up to 30 Hz and 800 ms after stimulus onset, and simplified by unrestricted time–frequency (TF) principal components analysis (PCA). Alpha event-related desynchronization (ERD) as measured by TF factor 610–9 (spectral peak latency at 610 ms and 9 Hz; 31.9% variance) was prominent over right posterior regions for targets, and markedly reduced in CHR patients compared to controls, particularly in three patients who later developed psychosis. In contrast, low-frequency event-related synchronization (ERS) distinctly linked to novels (260–1; 16.0%; mid-frontal) and N1 sink across conditions (130–1; 3.4%; centro-temporoparietal) did not differ between groups. Analogous time-domain CSD-ERP measures (temporal PCA), consisting of N1 sink, novelty mismatch negativity (MMN), novelty vertex source, novelty P3, P3b, and frontal response negativity, were robust and closely comparable between groups. Novelty MMN at FCz was, however, absent in the three converters. In agreement with prior findings, alpha ERD and MMN may hold particular promise for predicting transition to psychosis among CHR patients.     

Early event-related potentials changes during simple mental calculation in Chinese older adults with mild cognitive impairment: A case–control study

The aim was to examine early event-related potential (ERP) changes during mental arithmetic calculation task in mild cognitive impairment patients compared to healthy elderly. 16 mild cognitive impairment (MCI) subjects and 16 healthy Chinese older adults were studied. Event-related potentials were elicited using a simple mental calculation task. Performance on arithmetic calculation task, and the latency and amplitude of early event-related potential components (N1, P1, N170, and P2) were compared between the two groups. The reaction time of MCI group was significantly longer than that of control group (1691.03 ± 94.59 vs. 1539.55 ± 27.76, P < 0.01). The correct rate of MCI group (0.9463 ± 0.04) was significantly lower than that of control group (0.9776 ± 0.02, P < 0.01). The latency of temporal–occipital N170 and central–prefrontal P2 of MCI group were significantly prolonged compared to controls. MCI subjects presented significantly higher P2 amplitude. Compared with healthy controls, N170 was significantly lower at left temporal–occipital region and higher at right temporal–occipital region in mild cognitive impairment. Mild cognitive impairment patients had deficit on simple calculation. The early arithmetic calculation processing mechanism of mild cognitive impairment patients may be different from normal people.     

Influence of transcranial direct current stimulation of the dorsolateral prefrontal cortex on pain related emotions: A study using electroencephalographic power spectrum analysis

Pain is a multidimensional experience with sensory-discriminative, cognitive-evaluative and affective-motivational components. Emotional factors such as unpleasantness or anxiety are known to have influence on pain in humans. The aim of this single-blinded, cross over study was to evaluate the effects of transcranial direct current stimulation (tDCS) on emotional aspects of pain in pain alleviation. Fifteen subjects (5 females, 10 males) volunteered to participate in this study. In an oddball paradigm, three categories of 20 pictures (unpleasant, neutral, and pleasant) served as rare target pictures from the International Affective Picture System (IAPS). The power of the delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–25 Hz), and gamma (30–40 Hz) frequency bands in the three categories were measured using electroencephalography during an oddball paradigm at pre- and post-anodal or sham tDCS above the left dorsolateral prefrontal cortex (DLPFC). Results showed that the beta band power was significantly increased, and the alpha band power was significantly decreased during unpleasant pictures after anodal tDCS compared with sham tDCS. Furthermore, regarding unpleasant pictures, subjective reports of Self Assessment Manikin (SAM) for emotional valence after anodal tDCS showed a significant decrease of unpleasantness. Therefore, emotional aspects of pain may be effectively alleviated by tDCS of the left DLPFC as was shown not only by subjective evaluation, but also by objective observation of cerebral neural activity. This processing may be mediated by facilitation of the descending pain inhibitory system through enhancing neural activity of the left DLPFC.     

阿尔茨海默病患者定量脑电图特点

目的 探讨阿尔茨海默病（AD）患者定量脑电图（QEEG）的特点,慢波与快波比例与阿尔茨海默病认知能力的关系.方法 将30例AD患者与30例正常老人行QEEG功率谱分析及视觉脑电图（EEG）评分.功率谱按频率分：δ（0.8 ～4.0Hz）、θ（4.0～7.8Hz）、α（7.8～ 12.8Hz）、β（13.0～20.0Hz）,以δ＋θ/α＋β值作为观察评估指标进行比较.对两组全脑、额叶、颞叶、顶叶、枕叶δ＋θ/α＋β值及视觉EEG评分进行比较.将30例AD患者的简易智力状态评定量表（MMSE）评分和δ＋θ/α＋β值行Spearman相关分析.结果 AD组在全脑、额叶、颞叶、顶叶及枕叶的δ＋θ/α＋β值显著高于对照组,差异有统计学意义（t=3.11δ,2.694,3.051,3.657,4.167;P均＜0.01）.AD组的视觉EEG评分显著高于对照组,差异有统计学意义（t=4.052,P＜0.01）.30例AD患者的MMSE评分和全脑、额叶、颞叶、顶叶、枕叶δ＋θ/α＋β值呈负相关（r=-0.646-0.728,P均＜0.01）.结论 定量脑电图作为一种客观、量化的脑功能检测手段,有助于AD诊断,对AD患者认知能力评估有重要的价值.     

Cortical sources of resting state electroencephalographic alpha rhythms deteriorate across time in subjects with amnesic mild cognitive impairment

Cortical sources of resting state electroencephalographic (EEG) rhythms are abnormal in subjects with mild cognitive impairment (MCI). Here, we tested the hypothesis that these sources in amnesic MCI subjects further deteriorate over 1 year. To this aim, the resting state eyes-closed EEG data were recorded in 54 MCI subjects at baseline (Mini Mental State Examination I = 26.9; standard error [SE], 0.2) and at approximately 1-year follow-up (13.8 months; SE, 0.5; Mini Mental State Examination II = 25.8; SE, 0.2). As a control, EEG recordings were also performed in 45 normal elderly and in 50 mild Alzheimer's disease subjects. EEG rhythms of interest were delta (2–4 Hz), theta (4–8 Hz), alpha1 (8–10.5 Hz), alpha2 (10.5–13 Hz), beta1 (13–20 Hz), and beta2 (20–30 Hz). Cortical EEG sources were estimated using low-resolution brain electromagnetic tomography. Compared with the normal elderly and mild Alzheimer's disease subjects, the MCI subjects were characterized by an intermediate power of posterior alpha1 sources. In the MCI subjects, the follow-up EEG recordings showed a decreased power of posterior alpha1 and alpha2 sources. These results suggest that the resting state EEG alpha sources were sensitive—at least at the group level—to the cognitive decline occurring in the amnesic MCI group over 1 year, and might represent cost-effective, noninvasive and widely available markers to follow amnesic MCI populations in large clinical trials.     

Brain resting state is disrupted in chronic back pain patients

Recent brain functional magnetic resonance imaging (fMRI) studies have shown that chronic back pain (CBP) alters brain dynamics beyond the feeling of pain. In particular, the response of the brain default mode network (DMN) during an attention task was found abnormal. In the present work similar alterations are demonstrated for spontaneous resting patterns of fMRI brain activity over a population of CBP patients (n = 12, 29–67 years old, mean = 51.2). Results show abnormal correlations of three out of four highly connected sites of the DMN with bilateral insular cortex and regions in the middle frontal gyrus (p < 0.05), in comparison with a control group of healthy subjects (n = 20, 21–60 years old, mean = 38.4). The alterations were confirmed by the calculation of triggered averages, which demonstrated increased coactivation of the DMN and the former regions. These findings demonstrate that CBP disrupts normal activity in the DMN even during the brain resting state, highlighting the impact of enduring pain over brain structure and function.     

Sex differences between the combined and inattentive types of attention-deficit/hyperactivity disorder: An EEG perspective

This study investigated sex differences between the EEGs of Combined and Inattentive types of attention-deficit/hyperactivity disorder (AD/HD) within boys and girls aged 8–12 years. Subject groups included 80 AD/HD Combined type (40 boys and 40 girls), 80 AD/HD Inattentive type (40 boys and 40 girls) and 80 controls (40 boys and 40 girls). An eyes-closed resting EEG was recorded and Fourier transformed to provide estimates for absolute and relative power in the delta, theta, alpha and beta frequency bands, as well as total power and the theta/beta ratio. The boy AD/HD groups, compared with boy controls, had greater absolute and relative theta, greater theta/beta ratio, reduced absolute and relative alpha, and reduced absolute and relative beta. The girl AD/HD groups, compared with girl controls, had greater absolute delta, greater absolute and relative theta, greater theta/beta ratio, greater total power, and reduced relative delta and relative beta. Between AD/HD types, Combined type boys had globally greater absolute and relative theta, greater theta/beta ratio, and less relative alpha than Inattentive type boys. While topographical differences emerged, there were no significant global differences between AD/HD types in girls. That is, EEG differences between AD/HD types are dissimilar in boys and girls. Different EEG maturational patterns between boys and girls also obscure AD/HD-related EEG abnormalities. These results have important implications for our understanding of AD/HD in girls. Ignoring such sex differences may have compromised the value of previous AD/HD investigations, and these sex differences should be recognised in future research.