Cortical sources of resting-state EEG rhythms in "experienced" HIV subjects under antiretroviral therapy.

OBJECTIVE: Treatment-naïve patients with human immunodeficiency virus (HIV) are characterized by diffuse abnormalities of resting-state cortical electroencephalographic (EEG) rhythms (Babiloni et al., 2012a). Here, we tested the hypothesis that these EEG rhythms vary as a function of the systemic immune activity and antiretroviral therapy (ART) in HIV patients. METHODS: Resting-state eyes-closed EEG data were recorded in 68 ART-HIV patients (mini mental state evaluation (MMSE) of 27.5 ± 0.3 SEM), in 60 treatment-naïve HIV subjects (MMSE of 27.5 ± 0.4 SEM) and in 75 age-matched cognitively normal subjects (MMSE of 29.3 ± 0.1 SEM). Based on the CD4 lymphocytes' count, we divided ART-HIV subjects into two subgroups: those with CD4>500 cells/µl (ART-HIV+) and those with CD4<500 cells/µl (ART-HIV-). EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-12 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). Cortical EEG sources were estimated by LORETA software. RESULTS: Widespread theta, alpha, and beta sources were lower in ART-HIV subjects than in control subjects. Furthermore, occipital and temporal alpha 1 sources were lower in treatment-naïve HIV than in ART-HIV subjects. Moreover, the opposite was true for widespread pathological delta sources. Finally, parietal, occipital, and temporal alpha 1 sources were lower in ART-HIV- than in ART-HIV+ subjects. CONCLUSIONS: In ART-HIV subjects, cortical sources of resting-state alpha rhythms are related to systemic immune activity and cART. SIGNIFICANCE: This EEG procedure may produce biomarkers of treatment response in patients' brain compartments for longitudinal clinical studies.

Mechanisms of cortical neural synchronization related to healthy and impaired consciousness: evidence by quantitative electroencephalographic studies.

In this paper, we review the contribution of our research group to the study of human consciousness by quantitative electroencephalographic (EEG) techniques. We posit that EEG techniques can be extremely useful for a direct measurement of brain electrophysiological activity related to human consciousness for their unsurpassable high temporal resolution (milliseconds). This activity can be expressed in terms of event-related potentials as well as changes of EEG rhythms of interest, for example the dominant alpha rhythms (about 8-12 Hz). The results of our studies, and those of several independent groups, lead support to the hypothesis that these techniques provide important insights about the neurophysiologic mechanisms underlying cortical neural synchronization/desynchronization and the regulation of neuromodulatory systems (e.g. dopaminergic, noradrenergic, cholinergic, etc.) at the basis of brain arousal and consciousness in healthy subjects and in patients with impairment of the consciousness. A possible interaction of these mechanisms and the drugs administered to patients with consciousness disorders is discussed.

Inter-hemispherical functional coupling of EEG rhythms during the perception of facial emotional expressions.

OBJECTIVE: Brain rhythms of both hemispheres are involved in the processing of emotional stimuli but their interdependence between the two hemispheres is poorly known. Here we tested the hypothesis that passive visual perception of facial emotional expressions is related to a coordination of the two hemispheres as revealed by the inter-hemispherical functional coupling of brain electroencephalographic (EEG) rhythms. METHODS: To this aim, EEG data were recorded in 14 subjects observing emotional faces with neutral, happy or sad facial expressions (about 33% for each class). The EEG data were analyzed by directed transfer function (DTF), which estimates directional functional coupling of EEG rhythms. The EEG rhythms of interest were theta (about 4-6 Hz), alpha 1 (about 6-8 Hz), alpha 2 (about 8-10 Hz), alpha 3 (about 10-12 Hz), beta 1 (13-20 Hz), beta 2 (21-30 Hz), and gamma (31-44 Hz). RESULTS: In the frontal regions, inter-hemispherical DTF values were bidirectionally higher in amplitude across all frequency bands, during the perception of faces with sad compared to neutral or happy expressions. CONCLUSIONS: These results suggest that the processing of emotional negative facial expressions is related to an enhancement of a reciprocal inter-hemispherical flux of information in frontal cortex, possibly optimizing executive functions and motor control. SIGNIFICANCE: Dichotomical view of hemispherical functional specializations does not take into account remarkable reciprocal interactions between frontal areas of the two hemispheres during the processing of negative facial expressions.

Cortical sources of resting-state EEG rhythms are abnormal in naïve HIV subjects.

OBJECTIVE: The aim of the study was to test the hypothesis that cortical sources of resting-state electroencephalographic (EEG) rhythms show peculiar frequency/spatial features in naïve human subjects with human immunodeficiency virus (HIV) compared to healthy control subjects. METHODS: Resting-state eyes-closed EEG data were recorded in 18 naïve HIV subjects (15 males; mean age 39 years±2.0 standard error of mean, SEM) and in 18 age-matched cognitively normal subjects (15 males; 38.7years±2.2 SEM). EEG rhythms of interest were delta (2-4Hz), theta (4-8Hz), alpha1 (8-10Hz), alpha2 (10-12Hz), beta1 (13-20Hz) and beta2 (20-30Hz). Cortical EEG sources were estimated by normalised, low-resolution electromagnetic tomography (LORETA). RESULTS: Mini Mental State Evaluation (MMSE) score was lower in HIV (26.5 ± 0.7 SEM) than in healthy (29.2 ± 0.5 SEM) subjects (p<0.05). Central and parietal delta sources showed higher amplitude in the HIV than in control subjects. Furthermore, topographically widespread, cortical sources of resting-state alpha rhythms were lower in amplitude in HIV subjects than in control subjects. CONCLUSIONS: The present results suggest that topography and frequency of the cortical sources of resting-state EEG rhythms can distinguish groups of HIV and control subjects. SIGNIFICANCE: These results encourage future studies in an enlarged cohort of HIV subjects to test the hypothesis that the present methodological approach provides clinically useful information for an early detection of the effect of HIV infection on brain and cognitive functions.

Cortical sources of EEG rhythms in congestive heart failure and Alzheimer's disease.

INTRODUCTION: The brain needs continuous oxygen supply even in resting-state. Hypoxia enhances resting-state electroencephalographic (EEG) rhythms in the delta range, and reduces those in the alpha range, with a pattern similar to that observed in Alzheimer's disease (AD). Here we tested whether resting-state cortical EEG rhythms in patients with congestive heart failure (CHF), as a model of acute hypoxia, present frequency similarities with AD patients, comparable by cognitive status revealed by the mini mental state examination (MMSE). METHODS: Eyes-closed EEG data were recorded in 10 CHF patients, 20 AD patients, and 20 healthy elderly subjects (Nold) as controls. LORETA software estimated cortical EEG generators. RESULTS: Compared to Nold, both AD and CHF groups presented higher delta (2-4Hz) and lower alpha (8-13Hz) temporal sources. The highest delta and lowest alpha sources were observed in CHF subjects. In these subjects, the global amplitude of delta sources correlated with brain natriuretic peptide (BNP) level in the blood, as a marker of disease severity. CONCLUSIONS: Resting-state delta and alpha rhythms suggest analogies between the effects of acute hypoxia and AD neurodegeneration on the cortical neurons' synchronization. SIGNIFICANCE: Acute ischemic hypoxia could affect the mechanisms of cortical neural synchronization generating resting state EEG rhythms, inducing the "slowing" of EEG rhythms typically observed in AD patients.

Cortical sources of resting state EEG rhythms are abnormal in dyslexic children.

OBJECTIVE: Previous studies have been inconclusive whether dominant resting state alpha rhythms differ in amplitude in dyslexic subjects when compared to control subjects, being these rhythms considered as a reflection of effective cortical neural synchronization and cognition. Here we used a validated EEG source estimation to test the hypothesis that resting state alpha rhythms are abnormal in dyslexic subjects and are related to reading deficits. METHODS: Eyes-closed resting state electroencephalographic (EEG) data were recorded in 26 dyslexics (12 males, mean age of 11 years ± 0.5 standard error of mean, SEM) and 11 age-matched normal control subjects (8 males, mean age of 11 years ± 0.7 SEM). EEG rhythms of interest, based on individual alpha frequency peak, were the following: about 2-4 Hz (delta), 4-6 Hz (theta), 6-8 Hz (alpha 1), 8-10 Hz (alpha 2), and 10-12 Hz (alpha 3). For the higher frequencies, we selected beta 1 (13-20 Hz), beta 2 (20-30 Hz), and gamma (30-40 Hz). Cortical EEG sources were estimated by low resolution electromagnetic tomography (LORETA). LORETA solutions were normalized across all voxels and frequencies. RESULTS: Compared to the control children, the dyslexics showed lower amplitude of parietal, occipital, and temporal alpha 2 and alpha 3 sources. In the dyslexics, some of these sources were correlated to reading time of pseudo-words (parietal alpha 2, r=-0.56, p=0.02; parietal alpha 3, r=-0.58, p=0.02; temporal alpha 3, r=-0.57, p=0.02); the higher the alpha power, the shorter the reading time. CONCLUSIONS: Dyslexic children are characterized by limited abnormalities of resting state EEG rhythms as to topography (posterior regions) and frequency (alpha), which were related to phonological encoding (pseudo-words reading). SIGNIFICANCE: Dyslexia may be associated to some functional impairment of cortical neuronal synchronization mechanisms involved in the resting state condition.

Mobile phone emission increases inter-hemispheric functional coupling of electroencephalographic α rhythms in epileptic patients.

It has been reported that GSM electromagnetic fields (GSM-EMFs) of mobile phones modulate - after a prolonged exposure - inter-hemispheric synchronization of temporal and frontal resting electroencephalographic (EEG) rhythms in normal young and elderly subjects (Vecchio et al., 2007, 2010). Here we tested the hypothesis that this can be even more evident in epileptic patients, who typically suffer from abnormal mechanisms governing synchronization of rhythmic firing of cortical neurons. Eyes-closed resting EEG data were recorded in ten patients affected by focal epilepsy in real and sham exposure conditions. These data were compared with those obtained from 15 age-matched normal subjects of the previous reference studies. The GSM device was turned on (45 min) in the "GSM" condition and was turned off (45 min) in the other condition ("sham"). The mobile phone was always positioned on the left side in both patients and control subjects. Spectral coherence evaluated the inter-hemispheric synchronization of EEG rhythms at the following frequency bands: delta (about 2-4 Hz), theta (about 4-6 Hz), alpha1 (about 6-8 Hz), alpha2 (about 8-10 Hz), and alpha3 (about 10-12 Hz). The effects on the patients were investigated comparing the inter-hemispheric EEG coherence in the epileptic patients with the control group of subjects evaluated in the previous reference studies. Compared with the control subjects, epileptic patients showed a statistically significant higher inter-hemispheric coherence of temporal and frontal alpha rhythms (about 8-12 Hz) in the GSM than "Sham" condition. These results suggest that GSM-EMFs of mobile phone may affect inter-hemispheric synchronization of the dominant (alpha) EEG rhythms in epileptic patients. If confirmed by future studies on a larger group of epilepsy patients, the modulation of the inter-hemispheric alpha coherence due to the GSM-EMFs could have clinical implications and be related to changes in cognitive-motor function.

Brains "in concert": frontal oscillatory alpha rhythms and empathy in professional musicians.

Playing music in ensemble represents a unique human condition/performance where musicians should rely on empathic relationships. Recent theories attribute to frontal Brodmann areas (BAs) 44/45 and 10/11 a neural basis for "emotional" and "cognitive" empathy. We hypothesized that activity of these structures reflects empathy trait in professional musicians playing in ensemble. Simultaneous electroencephalographic (EEG) alpha rhythms (8-12 Hz) were recorded in three saxophone quartets during music performance in ensemble (EXECUTION), video observation of their own performance (OBSERVATION), a control task (CONTROL), and resting state (RESTING). EEG source estimation was performed. Results showed that the higher the empathy quotient test score, the higher the alpha desynchronization in right BA 44/45 during the OBSERVATION referenced to RESTING condition. Empathy trait score and alpha desynchronization were not correlated in other control areas or in EXECUTION/CONTROL conditions. These results suggest that alpha rhythms in BA 44/45 reflect "emotional" empathy in musicians observing own performance.

Mobile phone emission modulates event-related desynchronization of α rhythms and cognitive-motor performance in healthy humans.

OBJECTIVES: It has been shown that electromagnetic fields of Global System for Mobile Communications phone (GSM-EMFs) affect human brain rhythms (Vecchio et al., 2007, 2010), but it is not yet clear whether these effects are related to alterations of cognitive functions. METHODS: Eleven healthy adults underwent two electroencephalographic (EEG) sessions separated by 1 week, following a cross-over, placebo-controlled, double-blind paradigm. In both sessions, they performed a visual go/no-go task before real exposure to GSM-EMFs or after a sham condition with no EMF exposure. In the GSM real session, temporal cortex was continuously exposed to GSM-EMFs for 45 min. In the sham session, the subjects were not aware that the EMFs had been switched off for the duration of the experiment. In the go/no-go task, a central fixation stimulus was followed by a green (50% of probability) or red visual stimulus. Subjects had to press the mouse button after the green stimuli (go trials). With reference to a baseline period, power decrease of low- (about 8-10 Hz) and high-frequency (about 10-12 Hz) alpha rhythms indexed the cortical activity. RESULTS: It was found less power decrease of widely distributed high-frequency alpha rhythms and faster reaction time to go stimuli in the post- than pre-exposure period of the GSM session. No effect was found in the sham session. CONCLUSIONS: These results suggest that the peak amplitude of alpha ERD and the reaction time to the go stimuli are modulated by the effect of the GSM-EMFs on the cortical activity. SIGNIFICANCE: Exposure to GSM-EMFs for 45 min may enhance human cortical neural efficiency and simple cognitive-motor processes in healthy adults.

Cortical sources of resting state electroencephalographic rhythms in Parkinson's disease related dementia and Alzheimer's disease.

OBJECTIVE: Here we test the hypothesis that cortical source mapping of resting state electroencephalographic (EEG) rhythms could characterize neurodegenerative disorders inducing cognitive impairment such as Parkinson's disease related dementia (PDD) and Alzheimer's disease (AD). METHODS: To address this issue, eyes-closed resting state EEG rhythms were recorded in 13 PDD, 20 AD, and 20 normal elderly (Nold) subjects. Age, gender, and education were carefully matched across the three groups. Mini Mental State Evaluation (MMSE) score probed subjects' global cognitive status, and was matched between the PDD and AD groups. 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). EEG cortical sources were estimated by low resolution brain electromagnetic source tomography (LORETA). RESULTS: With respect to the Nold and AD groups, the PPD group was characterized by peculiar abnormalities of central delta sources and posterior cortical sources of theta and beta1 rhythms. With respect to the Nold group, the PDD and AD groups mainly pointed to lower posterior cortical sources of alpha1 rhythms, which were positively correlated to MMSE score across all PDD and AD subjects as a whole (the lower the alpha sources, the lower the MMSE score). This alpha decrease was greater in the AD than PPD patients. CONCLUSIONS: The results suggest that topography and frequency of eyes-closed resting state cortical EEG rhythms distinguished PDD and AD groups. SIGNIFICANCE: We report the existence of different effects of neurodegeneration on the cortical neural synchronization mechanisms generating resting state EEG rhythms in PDD and AD patients.

Simultaneous recording of electroencephalographic data in musicians playing in ensemble.

Here we describe a methodological approach for the simultaneous electroencephalographic (EEG) recording in musicians playing in ensemble. Four professional saxophonists wore pre-wired EEG caps (30 electrodes placed according to an augmented 10-20 system; cephalic reference and ground). Each cap was connected to a single multi-channel amplifier box [Brain Explorer (BE), EB-Neuro(©)]. The four boxes converged to a single workstation equipped with a software (GALILEO NT, EB-Neuro(©)) allowing the simultaneous recording of sounds, digital trigger, and EEG-electrooculographic (EOG)-electromyographic (EMG) data, and providing a separate output file for each individual. Noteworthy, the subjects were electrically decoupled to satisfy international safety guidelines. The quality of the EEG data was confirmed by the rate of artifact-free EEG epochs (about 80%) and by EEG spectral features. During the resting state, dominant EEG power density values were observed at alpha band (8-12Hz) in posterior cortex. The quality of EMG can be used to identify "on" and "off" states of the musicians' motor performance, thus potentially allowing the investigation of the relationships between EEG dynamics and different characteristics of the specific performance. During the music performance, alpha power density values decreased in amplitude in several cortical regions, whereas power density values enhanced within narrow high-frequency bands. In conclusion, the present methodological approach appeared to be suitable for simultaneous EEG recordings in musicians playing in ensemble.

Resting state eyes-closed cortical rhythms in patients with locked-in-syndrome: an EEG study.

OBJECTIVE: Locked-in syndrome (LIS) is a state of complete paralysis, except for ocular movements, which results from ventral brainstem lesions. Patients typically are fully conscious. Here we tested the hypothesis that electroencephalographic (EEG) rhythms are abnormal in LIS patients, possibly due to an impaired neural synchronization between brainstem and cerebral cortex. METHODS: Resting state eyes-closed EEG data were recorded in 13 LIS subjects and 15 cognitively normal control subjects. With reference to the individual alpha frequency (IAF), the bands of interest were delta (IAF-8 to IAF-6Hz), theta (IAF-6 to IAF-4Hz), alpha 1 (IAF-4 to IAF-2Hz), alpha 2 (IAF-2 to IAFHz), and alpha 3 (IAF to IAF+2Hz). Furthermore, beta 1 (13-20Hz) and beta 2 (20-30Hz) bands were also considered. Cortical EEG sources were estimated by low-resolution electromagnetic tomography (LORETA). RESULTS: The power of alpha 2 and alpha 3 sources in all regions was lower in patients with LIS compared to controls. The power of delta sources in central, parietal, occipital and temporal regions was higher in patients with LIS compared to controls. CONCLUSIONS: These results suggest that cortical sources of resting state eyes-closed alpha and delta rhythms are abnormal in LIS patients. SIGNIFICANCE: LIS is accompanied by a functional impairment of cortical neuronal synchronization mechanisms in the resting state condition.

Cortical sources of EEG rhythms are abnormal in down syndrome.

OBJECTIVE: Previous studies have been inconclusive whether dominant resting state alpha rhythms are greater or lower in amplitude in subjects with Down syndrome (DS) when compared to control subjects, ample resting alpha rhythms being considered as a reflection of good mechanisms of cortical neural synchronization. Here we tested the hypothesis that when the effects of head volume conduction are taken into account by the normalization of the cortical sources of resting alpha rhythms, these sources are lower in amplitude in DS subjects than in controls in line with typical findings in Alzheimer's disease patients. METHODS: Eyes-closed resting electroencephalographic (EEG) data were recorded in 45 DS subjects (25 males; mean age of 22.8years+/-0.7 standard error of mean (SEM)) and in 45 age-matched cognitively normal subjects (25 males; mean age of 22.4years+/-0.5 SEM). EEG rhythms of interest were delta (2-4Hz), theta (4-8Hz), alpha 1 (8-10.5Hz), alpha 2 (10.5-13Hz), beta 1 (13-20Hz), beta 2 (20-30Hz), and gamma (30-40Hz). Cortical EEG sources were estimated by low resolution electromagnetic tomography (LORETA) and normalized across all voxels and frequencies. RESULTS: Central, parietal, occipital, and temporal cortical sources of resting alpha and beta rhythms were lower in amplitude in the DS than control subjects, whereas the opposite was true for occipital delta cortical sources. A control analysis on absolute source values showed that they were globally larger in amplitude across several frequency bands in DS than control subjects. CONCLUSIONS: These results suggest that normalized cortical sources of alpha rhythms are lower in amplitude in DS than control subjects, as it is typically found in Alzheimer's disease. SIGNIFICANCE: DS is accompanied by a functional impairment of cortical neuronal synchronization mechanisms in the resting state condition.

Activity of hippocampal, amygdala, and neocortex during the Rey auditory verbal learning test: an event-related potential study in epileptic patients.

OBJECTIVE: Previous evidence in epileptic subjects has shown that theta (about 4-7Hz) and gamma rhythms (about 40-45Hz) of hippocampus, amygdala, and neocortex were temporally synchronized during the listening of repeated words successfully remembered (Babiloni et al., 2009). Here we re-analyzed those electroencephalographic (EEG) data to test whether a parallel increase in amplitude of late positive event-related potentials takes place. METHODS: Intracerebral electroencephalographic (EEG) activity had been recorded in five subjects with drug-resistant temporal lobe epilepsy, undergoing pre-surgical evaluation. During the recording of the intracerebral EEG activity, the subjects performed a computerized version of the Rey auditory verbal learning test (RAVLT). They heard the same list of 15 common words for five times. Each time, immediately after the listening of the list, the subjects were required to repeat as many words as they could recall. RESULTS: We found that late positive event-related potentials (ERPs) peaking at about 350ms post-stimulus in amygdala, hippocampus, and occipital-temporal cortex had a higher amplitude during the listening of the repeated words that were subsequently recalled than for those that were not recalled. CONCLUSIONS: Late positive ERPs reflect a functional mechanism implemented in a human brain network spanning amygdala, hippocampus, and occipital-temporal cortex which is at the basis of the memorization processes of verbal materials. SIGNIFICANCE: This ERP component is a promising neuromarker of successful memorization of repeated words in humans.

Cortical responses to consciousness of schematic emotional facial expressions: a high-resolution EEG study.

Is conscious perception of emotional face expression related to enhanced cortical responses? Electroencephalographic data (112 channels) were recorded in 15 normal adults during the presentation of cue stimuli with neutral, happy or sad schematic faces (duration: "threshold time" inducing about 50% of correct recognitions), masking stimuli (2 s), and go stimuli with happy or sad schematic faces (0.5 s). The subjects clicked left (right) mouse button in response to go stimuli with happy (sad) faces. After the response, they said "seen" or "not seen" with reference to previous cue stimulus. Electroencephalographic data formed visual event-related potentials (ERPs). Cortical sources of ERPs were estimated by LORETA software. Reaction time to go stimuli was generally shorter during "seen" than "not seen" trials, possibly due to covert attention and awareness. The cue stimuli evoked four ERP components (posterior N100, N170, P200, and P300), which had similar peak latency in the "not seen" and "seen" ERPs. Only N170 amplitude showed differences in amplitude in the "seen" versus "not seen" ERPs. Compared to the "not seen" ERPs, the "seen" ones showed prefrontal, premotor, and posterior parietal sources of N170 higher in amplitude with the sad cue stimuli and lower in amplitude with the neutral and happy cue stimuli. These results suggest that nonconscious and conscious processing of schematic emotional facial expressions shares a similar temporal evolution of cortical activity, and conscious processing induces an early enhancement of bilateral cortical activity for the schematic sad facial expressions (N170).

Resting state cortical rhythms in athletes: a high-resolution EEG study.

The present electroencephalographic (EEG) study tested the working hypothesis that the amplitude of resting state cortical EEG rhythms (especially alpha, 8-12 Hz) was higher in elite athletes compared with amateur athletes and non-athletes, as a reflection of the efficiency of underlying back-ground neural synchronization mechanisms. Eyes closed resting state EEG data were recorded in 16 elite karate athletes, 20 amateur karate athletes, and 25 non-athletes. The EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Statistical results showed that the amplitude of parietal and occipital alpha 1 sources was significantly higher in the elite karate athletes than in the non-athletes and karate amateur athletes. Similar results were observed in parietal and occipital delta sources as well as in occipital theta sources. Finally, a control confirmatory experiment showed that the amplitude of parietal and occipital delta and alpha 1 sources was stronger in 8 elite rhythmic gymnasts compared with 14 non-athletes. These results supported the hypothesis that cortical neural synchronization at the basis of eyes-closed resting state EEG rhythms is enhanced in elite athletes than in control subjects.

Mobile phone emission modulates inter-hemispheric functional coupling of EEG alpha rhythms in elderly compared to young subjects.

OBJECTIVE: It has been reported that GSM electromagnetic fields (GSM-EMFs) of mobile phones modulate--after a prolonged exposure--inter-hemispheric synchronization of temporal and frontal resting electroencephalographic (EEG) rhythms in normal young subjects [Vecchio et al., 2007]. Here we tested the hypothesis that this effect can vary on physiological aging as a sign of changes in the functional organization of cortical neural synchronization. METHODS: Eyes-closed resting EEG data were recorded in 16 healthy elderly subjects and 5 young subjects in the two conditions of the previous reference study. The GSM device was turned on (45 min) in one condition and was turned off (45 min) in the other condition. Spectral coherence evaluated the inter-hemispheric synchronization of EEG rhythms at the following bands: delta (about 2-4 Hz), theta (about 4-6 Hz), alpha 1 (about 6-8 Hz), alpha 2 (about 8-10 Hz), and alpha 3 (about 10-12 Hz). The aging effects were investigated comparing the inter-hemispheric EEG coherence in the elderly subjects vs. a young group formed by 15 young subjects (10 young subjects of the reference study; Vecchio et al., 2007). RESULTS: Compared with the young subjects, the elderly subjects showed a statistically significant (p<0.001) increment of the inter-hemispheric coherence of frontal and temporal alpha rhythms (about 8-12 Hz) during the GSM condition. CONCLUSIONS: These results suggest that GSM-EMFs of a mobile phone affect inter-hemispheric synchronization of the dominant (alpha) EEG rhythms as a function of the physiological aging. SIGNIFICANCE: This study provides further evidence that physiological aging is related to changes in the functional organization of cortical neural synchronization.

Inter-hemispheric functional coupling of eyes-closed resting EEG rhythms in adolescents with Down syndrome.

OBJECTIVE: We tested the hypothesis that inter-hemispheric directional functional coupling of eyes-closed resting EEG rhythms is abnormal in adolescents with Down syndrome (DS). METHODS: Eyes-closed resting EEG data were recorded in 38 DS adolescents (18.7 years +/-0.67 SE, IQ=49+/-1.9 SE) and in 17 matched normal control subjects (NYoung=19.1 years +/-0.39 SE). The EEG data were recorded from 8 electrodes (Fp1, Fp2, C3, C4, T3, T4, O1, O2) referenced to vertex. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). Power of EEG rhythms was evaluated by FFT for control purposes, whereas inter-hemispheric directional EEG functional coupling was computed by directed transfer function (DTF). RESULTS: As expected, alpha, beta, and gamma power was widely higher in NYoung than DS subjects, whereas the opposite was true for delta power. As a novelty, DTF (directionality) values globally prevailed from right to left occipital areas in NYoung subjects and in the opposite direction in DS patients. A control experiment showed that this DTF difference could not be observed in the comparison between DS adults with mild cognitive impairment and normal age-matched adults. CONCLUSIONS: These results indicate a peculiar abnormal directional inter-hemispheric interplay in visual occipital areas of DS adolescents. SIGNIFICANCE: Direction of inter-hemispheric EEG functional coupling unveils a new abnormal brain network feature in DS adolescents.

Cortical sources of resting-state alpha rhythms are abnormal in persistent vegetative state patients.

OBJECTIVE: High power of pre-stimulus cortical alpha rhythms (about 8-12 Hz) underlies conscious perception in normal subjects. Here we tested the hypothesis that these rhythms are abnormal in persistent vegetative state (PVS) patients, who are awake but not aware of self and environment. METHODS: Clinical and resting-state, eyes-closed electroencephalographic (EEG) data were taken from a clinical archive. These data were recorded in 50 PVS subjects (level of cognitive functioning--LCF score: I-II) and in 30 cognitively normal subjects. Rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). Cortical sources were estimated by low-resolution electromagnetic tomography (LORETA). Based on LCF score at 3-months follow-up, PVS patients were retrospectively divided into three groups: 30 subjects who did not recover (NON-REC patients; follow-up LCF: I-II), 8 subjects classified as minimally conscious state patients (MCS patients; follow-up LCF: III-IV), and 12 subjects who recovered (REC patients; follow-up LCF: V-VIII). RESULTS: Occipital source power of alpha 1 and alpha 2 was high in normal subjects, low in REC patients, and practically null in NON-REC patients. A Cox regression analysis showed that the power of alpha source predicted the rate of the follow up recovery, namely the higher its power, the higher the chance to recover consciousness. Furthermore, the MCS patients showed intermediate values of occipital alpha source power between REC and NON-REC patients. CONCLUSIONS: These results suggest that cortical sources of alpha rhythms are related to the chance of recovery at a 3-months follow-up in patients in persistent vegetative state. SIGNIFICANCE: Cortical sources of resting alpha rhythms might predict recovery in PVS patients.

Hippocampal, amygdala, and neocortical synchronization of theta rhythms is related to an immediate recall during rey auditory verbal learning test.

It is well known that theta rhythms (3-8 Hz) are the fingerprint of hippocampus, and that neural activity accompanying encoding of words differs according to whether the items are later remembered or forgotten ["subsequent memory effect" (SME)]. Here, we tested the hypothesis that temporal synchronization of theta rhythms among hippocampus, amygdala, and neocortex is related to immediate memorization of repeated words. To address this issue, intracerebral electroencephalographic (EEG) activity was recorded in five subjects with drug-resistant temporal lobe epilepsy (TLE), under presurgical monitoring routine. During the recording of the intracerebral EEG activity, the subjects performed a computerized version of Rey auditory verbal learning test (RAVLT), a popular test for the clinical evaluation of the immediate and delayed memory. They heard the same list of 15 common words for five times. Each time, immediately after listening the list, the subjects were required to repeat as many words as they could recall. Spectral coherence of the intracerebral EEG activity was computed in order to assess the temporal synchronization of the theta (about 3-8 Hz) rhythms among hippocampus, amygdala, and temporal-occipital neocortex. We found that theta coherence values between amygdala and hippocampus, and between hippocampus and occipital-temporal cortex, were higher in amplitude during successful than unsuccessful immediate recall. A control analysis showed that this was true also for a gamma band (40-45 Hz). Furthermore, these theta and gamma effects were not observed in an additional (control) subject with drug-resistant TLE and a wide lesion to hippocampus. In conclusion, a successful immediate recall to the RAVLT was associated to the enhancement of temporal synchronization of the theta (gamma) rhythms within a cerebral network including hippocampus, amygdala, and temporal-occipital neocortex.