Article

The alteration of spontaneous low frequency oscillations caused by acute electromagnetic fields exposure

Authors:
  • PingAn Tech
  • China Academy of Information and Communications Technology
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Abstract

The motivation of this study is to evaluate the possible alteration of regional resting state brain activity induced by the acute radiofrequency electromagnetic field (RF-EMF) exposure (30min) of Long Term Evolution (LTE) signal. We designed a controllable near-field LTE RF-EMF exposure environment. Eighteen subjects participated in a double-blind, crossover, randomized and counterbalanced experiment including two sessions (real and sham exposure). The radiation source was close to the right ear. Then the resting state fMRI signals of human brain were collected before and after the exposure in both sessions. We measured the amplitude of low frequency fluctuation (ALFF) and fractional ALFF (fALFF) to characterize the spontaneous brain activity. We found the decreased ALFF value around in left superior temporal gyrus, left middle temporal gyrus, right superior temporal gyrus, right medial frontal gyrus and right paracentral lobule after the real exposure. And the decreased fALFF value was also detected in right medial frontal gyrus and right paracentral lobule. The study provided the evidences that 30min LTE RF-EMF exposure modulated the spontaneous low frequency fluctuations in some brain regions. With resting state fMRI, we found the alteration of spontaneous low frequency fluctuations induced by the acute LTE RF-EMF exposure.

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... The inconsistency could partly be attributed to different exposure frequencies, modulation modes, and exposure durations [Zhang et al., 2017]. For 4G-related signals, only our two previous studies have investigated the acute effect of long-term evolution (LTE) EMF exposure on human brain function [Lv et al., 2014;Yang et al., 2016] using EEG and functional magnetic resonance imaging (fMRI). We found that 30 min of LTE-EMF exposure modulated the alpha/ beta EEG bands [Yang et al., 2016] and spontaneous low-frequency fluctuations [Lv et al., 2014] in some brain regions. ...
... For 4G-related signals, only our two previous studies have investigated the acute effect of long-term evolution (LTE) EMF exposure on human brain function [Lv et al., 2014;Yang et al., 2016] using EEG and functional magnetic resonance imaging (fMRI). We found that 30 min of LTE-EMF exposure modulated the alpha/ beta EEG bands [Yang et al., 2016] and spontaneous low-frequency fluctuations [Lv et al., 2014] in some brain regions. Since LTE networks have been widely deployed, we should make more effort to evaluate the possible effects of LTE-EMF exposure from different perspectives. ...
... Functional segregation (or local integration) emphasizes distributed processing within different brain regions, whereas functional integration (or global integration) stresses long-range interactions across regions [Sporns et al., 2004;Park and Friston, 2013]. Previous neurophysiological studies have observed that EMF-induced changes in brain activity occur not only in the region near the exposure site but also in remote regions and even in contralateral brain regions [Croft et al., 2010;Lv et al., 2014;Roggeveen et al., 2015a;Yang et al., 2016]. This phenomenon of remote effects inspired us to investigate whether EMF exposure modulated functional integration between different brain regions. ...
Article
By now, the neurophysiological effect of electromagnetic field (EMF) exposure and its underlying regulating mechanisms are not well manifested. In this study, we aimed to investigate whether acute long‐term evolution (LTE) EMF exposure could modulate brain functional connectivity using regional homogeneity (ReHo) method and seed‐based analysis on resting‐state functional magnetic resonance imaging (fMRI). We performed the LTE‐EMF exposure experiment and acquired the resting‐state brain activities before and after EMF exposure. Then we applied ReHo index to characterize the localized functional connectivity and seed‐based method to evaluate the inter‐regional functional connectivity. Statistical comparisons were conducted to identify the possible evidence of brain functional connectivity modulation induced by the acute LTE‐EMF exposure. We found that the acute LTE‐EMF exposure modulated localized intra‐regional connectivity (p < 0.05, AlphaSim corrected, voxel size ≥ 18) and inter‐regional connectivity in some brain regions (p < 0.05, AlphaSim corrected, voxel size ≥ 18). Our results may indicate that the approaches relying on network‐level inferences could provide deeper insight into the acute effect on human functional activity induced by LTE‐EMF exposure. Bioelectromagnetics. 40:42–51, 2019.
... Checking the articles' references did not result in inclusion of further articles. Of the 16 studies, two studies used MRI for data acquisition [Curcio et al., 2012;Lv et al., 2014], one used PET scans [Volkow et al., 2011], and the rest utilized EEG. The studies primarily investigated the potential physiological effect induced by RF-EMFs. ...
... It should be noted that one study assessed not only the effect of phone use, but also the mixed effect of caffeine and simultaneous MP exposure. Typically, double/single blind randomized counterbalanced crossover design was used [Lowden et al., 2011;Volkow et al., 2011;Curcio et al., 2012;Schmid et al., 2012a,b;Vecchio et al., 2012b;Loughran et al., 2013;Lv et al., 2014;Ghosn et al., 2015;Roggeveen et al., 2015b;Yang et al., 2016], in which participants were exposed to two different conditions. In the sham condition, the MP was switched "on" but without global system for mobile communication (GSM) RF; in the real condition, the phone was switched "on" with GSM RF. ...
... It was suggested that if MP emissions affect the excitability of neurons, that this would be at a relatively restricted local level undetectable using traditional fMRI techniques. In comparison, Lv et al. [2014] found decreased amplitude of low frequency fluctuations (ALFF) in the BOLD signal in several regions (left superior temporal gyrus, left middle temporal gyrus, right superior temporal gyrus, right medial frontal gyrus, and right paracentral lobule) during rest after real exposure. ALFF was calculated as total power within a frequency range between 0.01 and 0.1 Hz, and thus indexed strength or intensity of low frequency oscillations [Lv et al., 2014]. ...
Article
Full-text available
Due to its attributes, characteristics, and technological resources, the mobile phone (MP) has become one of the most commonly used communication devices. Historically, ample evidence has ruled out the substantial short-term impact of radiofrequency electromagnetic field (RF-EMF) emitted by MP on human cognitive performance. However, more recent evidence suggests potential harmful effects associated with MP EMF exposure. The aim of this review is to readdress the question of whether the effect of MP EMF exposure on brain function should be reopened. We strengthen our argument focusing on recent neuroimaging and electroencephalography studies, in order to present a more specific analysis of effects of MP EMF exposure on neurocognitive function. Several studies indicate an increase in cortical excitability and/or efficiency with EMF exposure, which appears to be more prominent in fronto-temporal regions and has been associated with faster reaction time. Cortical excitability might also underpin disruption to sleep. However, several inconsistent findings exist, and conclusions regarding adverse effects of EMF exposure are currently limited. It also should be noted that the crucial scientific question of the effect of longer-term MP EMF exposure on brain function remains unanswered and essentially unaddressed. Bioelectromagnetics. 9999:1-10, 2017.© 2017 Wiley Periodicals, Inc.
... Due to the popularity of mobile co mmunications over the past few years, a large number of studies have investigated the possible effects of radiofrequency electromagnetic fields (EM F) on human brain [1,2]. In addition to using behavioral and cognitive measures to evaluate the external performances [3], many studies have attempted to apply the neurophysiologic or neuroimage approaches to investigate whether EMF exposure modulates the internal brain activities, which are reflected as the signals of electrical activ ity [4,5], cortical excitability [6], cerebral blood flo w [7], brain g lucose metabolis m [8] or hemodynamic response [9,10]. Lots of significant evidences have been found with these techniques. ...
... Studies with this method have demonstrated that interhemispheric functional connectivity has the marked and regionally specific age-related changes during the lifespan [16] and its pattern was altered in patients with some neurological diseases [17]. Although there have been two fMRI studies about the local brain activities during resting state [10] or performing a cognitive task [9] induced by the EMF exposure, to our knowledge, no previous study has applied the VM HC method based on fMRI data to examine the effects of EMF exposure on the interhemispheric functional connectivity. ...
... In our previous study, we have reported preliminarily that 30 min Long Term Evolution (LTE) EMF exposure could modulate the amplitude of spontaneous low frequency fluctuations (ALFF) during resting state in some brain regions over the two hemispheres [10]. But it is unknown whether interhemispheric functional connectivity would be altered by the EMF exposure. ...
... 5 However, the results of resting state EEG experiments have been contradictory. For example, some studies have reported enhancement of the alpha (8)(9)(10)(11)(12) and beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) band power values after exposure to pulse-modulated 450-and 900-MHz signals, 6,7 pulse-modulated magnetic fields, 8 and active mobile phone signals. 9,10 In contrast, some studies have shown decreased alpha band activity after 20 minutes of extremely low-frequency EMF exposure, 11,12 or 5 minutes of magnetic field exposure, 13 or global system for mobile communications (GSM) EMF exposure. ...
... An emerging technology, "longterm evolution" (LTE) wireless service, has been deployed since 2009 and the number of global LTE subscribers is expected to reach 1.37 billion by the end of 2015. 22 Other than our previous functional magnetic resonance imaging (fMRI) study, 23 there are very few reports on the effect of exposure to LTE EMF on brain function. ...
... We previously found that 30 minutes of exposure to LTE EMF modulated the spontaneous low-frequency fluctuations. 23 We were interested in confirming our previous results using another neurophysiological method and also sought to assess the evolution of the effect over time during such exposure. In this article, we have investigated for the first time the changes in the resting state EEG caused by exposure to LTE signals. ...
Article
Long-term evolution (LTE) wireless telecommunication systems are widely used globally, which has raised a concern that exposure to electromagnetic fields (EMF) emitted from LTE devices can change human neural function. To date, few studies have been conducted on the effect of exposure to LTE EMF. Here, we evaluated the changes in electroencephalogram (EEG) due to LTE EMF exposure. An LTE EMF exposure system with a stable power emission, which was equivalent to the maximum emission from an LTE mobile phone, was used to radiate the subjects. Numerical simulations were conducted to ensure that the specific absorption rate in the subject's head was below the safety limits. Exposure to LTE EMF reduced the spectral power and the interhemispheric coherence in the alpha and beta bands of the frontal and temporal brain regions. No significant change was observed in the spectral power and the inter-hemispheric coherence in different timeslots during and after the exposure. These findings also corroborated those of our previous study using functional magnetic resonant imaging.
... In order to avoid the subjective bias or any other influences, we designed a double-blind, crossover, randomized and counterbalanced exposure study. The exposure setup was similar to our previous studies [13,14]. In brief, the exposure source was simulated by a dipole antenna (SPEAG AG, Zurich, Switzerland) which was placed on the right ear with 1 cm distance, and the LTE exposure signal at 2.573 GHz was produced by a CMW 500 (R&S, Munich, Germany) and an RF amplifier (AR, Bothell, WA, USA). ...
... In our previous work, we have applied the resting state functional magnetic resonance imaging (fMRI) technique to examine the change of spontaneous brain activities induced by LTE EMF exposure [14]. After the real exposure, we found that the decreased amplitude of low frequency fluctuation in some brain regions which mostly located in medial frontal gyrus, left and right temporal gyrus [14]. ...
... In our previous work, we have applied the resting state functional magnetic resonance imaging (fMRI) technique to examine the change of spontaneous brain activities induced by LTE EMF exposure [14]. After the real exposure, we found that the decreased amplitude of low frequency fluctuation in some brain regions which mostly located in medial frontal gyrus, left and right temporal gyrus [14]. Due to the compatibility with exposure system, EEG signals could be simultaneously examined during the EMF exposure. ...
Article
Full-text available
In this paper, we aimed to investigate the possible interactions between human brain and radiofrequency electromagnetic fields (EMF) with electroencephalogram (EEG) technique. Unlike the previous studies which mainly focused on EMF effect on local brain activities, we attempted to evaluate whether the EMF emitted from Long Term Evolution (LTE) devices can modulate the functional connectivity of brain electrical activities. Ten subjects were recruited to participate in a crossover, double-blind exposure experiment which included two sessions (real and sham exposure). In each session, LTE EMF exposure (power on or off) lasted for 30 min and the EEG signals were collected with 32 channels throughout the experiment. Then we applied the synchronization likelihood method to quantify the neural synchronization over the whole brain in different frequency bands and in different EEG record periods. Our results illustrated that the short-term LTE EMF exposure would modulate the synchronization patterns of EEG activation across the whole brain.
... Besides the findings on regional brain, some studies have demonstrated that acute EMF exposure could modulate the interhemispheric synchronization of temporal and frontal resting EEG rhythms in normal subjects [2] and epileptic patients [3]. Our recent study applied resting state fMRI to investigate the influence of Long Term Evolution (LTE) EMF exposure on brain [4]. We found spontaneous low frequency oscillations were altered by LTE EMF exposure in some brain regions. ...
... We designed a controllable near-field LTE EMF exposure environment (figure 1) [4]. 21 right-handed healthy subjects were enrolled to participate in a double, crossover, randomized and counterbalanced experiment including two sessions In each session, the EMF exposure (real or sham) lasted for 30 min. ...
... We examined the amplitude of low frequency fluctuation (ALFF) of brain activity [6], and found three brain regions showing significantly decreased ALFF values after real exposure [4]. Then we selected these three regions as seed volumes for the functional connectivity analyses. ...
Conference Paper
Full-text available
Background / Purpose: Recently, many studies have applied neurophysiologic or neuroimage approaches to investigate the possible effects of radiofrequency electromagnetic fields (EMF) on the human brain. Besides the findings on regional brain, some studies have demonstrated that acute EMF exposure could modulate the interhemispheric synchronization of temporal and frontal resting EEG rhythms in normal subjects and epileptic patients. Main conclusion: Acute LTE EMF exposure can modulate the resting state functional connectivity.
... These results consistently validated the simultaneous modulation of different brain units owing to the LTE-EMF exposure. By LTE exposure, the decreased EEG alpha and beta band power (Yang et al. 2016) and the altered interhemispheric synchronization pattern of EEG activation (Lv et al. 2014a, b) have also been reported. Furthermore, the lack of effect on awake EEG has also been published (Nakatani-Enomoto et al. 2020). ...
... It may indicate the disruption of the normal synchronization ability by LTE EMF exposure. A similar effect has also been reported by our EEG studies (Lv et al. 2014a, b) but not in a recent study (Nakatani-Enomoto et al. 2020). A marked increase in the clustering coefficient was observed at the contralateral medial frontal lobe (SMA_L and MCG_L) and ipsilateral inferior and medial frontal lobe (IFGtriang_R, MCG_R). ...
Article
Full-text available
Human exposure to the electromagnetic field emitted by wireless communication systems has raised public concerns. There were claims of the potential association of some neurophysiological disorders with the exposure, but the mechanism is yet to be established. The wireless networks, recently, experience a transition from the 4th generation (4G) to 5th generation (5G), while 4G long-term evolution (LTE) is still the frequently used signal in wireless communication. In the study, exposure experiments were conducted using the LTE signal. The subjects were divided into sham and real exposure groups. Before and after the exposure experiments, they underwent functional magnetic resonance imaging. Within-session and between-session comparisons have been executed for functional connectivity and network properties. Individual specific absorption rate (SAR) was also calculated. The results indicated that acute LTE exposure beneath the safety limits modulated both the functional connection and graph-based properties. To characterize the effect of functional activity, SAR averaged over a certain tissue mass was not an appropriate metric. The potential neurophysiological effect of 5G exposure has also been discussed in the study.
... 10,11 It has also been defined that there is not only the risk of acoustic neuroma but also glioma [12][13][14][15][16] and that risk increases with increase in the duration of cell phone use. Lv et al. 17 reported that the radiofrequency radiations from LTE 46 technology affect brain neural activity in both the closer brain region and in remote region including the left hemisphere of the brain. ...
... These changes indicate disturbed or 'non emotional' state of the test rats. 17,28 The non emotionality of rats was also visible by the stretch-attend postures and freezing behavior shown by test animals. ...
Article
Full-text available
Abstract Objectives:The goals of this study were: (1) to obtain basic information about the effects of long-term use of mobile phones on cytological makeup of the hippocampus in rat brains (2) to evaluate the effects on antioxidant status, and (3) to evaluate the effects on cognitive behavior particularly on learning and memory. Methods:Rats (age 30 days, 120 ± 5 g) were exposed to 900 MHz radio waves by means of a mobile hand set for 4 hours per day for 15 days. Effects on anxiety, spatial learning, and memory were studied using the open field test, the elevated plus maze, the Morris water maze (MWM), and the classic maze test. Effects on brain antioxidant status were also studied. Cresyl violet staining was done to assess the neuronal damage. Result:A significant change in behavior, i.e., more anxiety and poor learning was shown by test animals as compared to controls and sham group. A significant change in the level of antioxidant enzymes and non-enzymatic antioxidants, and an increase in lipid peroxidation were observed in the test rats. Histological examination showed neurodegenerative cells in hippocampal sub regions and the cerebral cortex. Discussion:Thus our findings indicate extensive neurodegeneration on exposure to radio waves. Increased production of reactive oxygen species due to exhaustion of enzymatic and non-enzymatic antioxidants and increased lipid peroxidation indicate extensive neurodegeneration in selective areas of CA1, CA3, DG, and the cerebral cortex. This extensive neuronal damage results in alterations in behavior related to memory and learning. Keywords: Antioxidant enzymes, Anxiety, Behavior, Lipid peroxidation, Mobile radiations, Neurodegeneration
... 10,11 It has also been defined that there is not only the risk of acoustic neuroma but also glioma [12][13][14][15][16] and that risk increases with increase in the duration of cell phone use. Lv et al. 17 reported that the radiofrequency radiations from LTE 46 technology affect brain neural activity in both the closer brain region and in remote region including the left hemisphere of the brain. ...
... These changes indicate disturbed or 'non emotional' state of the test rats. 17,28 The non emotionality of rats was also visible by the stretch-attend postures and freezing behavior shown by test animals. ...
Article
Full-text available
Abstract Objectives:The goals of this study were: (1) to obtain basic information about the effects of long-term use of mobile phones on cytological makeup of the hippocampus in rat brains (2) to evaluate the effects on antioxidant status, and (3) to evaluate the effects on cognitive behavior particularly on learning and memory. Methods:Rats (age 30 days, 120 ± 5 g) were exposed to 900 MHz radio waves by means of a mobile hand set for 4 hours per day for 15 days. Effects on anxiety, spatial learning, and memory were studied using the open field test, the elevated plus maze, the Morris water maze (MWM), and the classic maze test. Effects on brain antioxidant status were also studied. Cresyl violet staining was done to assess the neuronal damage. Result:A significant change in behavior, i.e., more anxiety and poor learning was shown by test animals as compared to controls and sham group. A significant change in the level of antioxidant enzymes and non-enzymatic antioxidants, and an increase in lipid peroxidation were observed in the test rats. Histological examination showed neurodegenerative cells in hippocampal sub regions and the cerebral cortex. Discussion:Thus our findings indicate extensive neurodegeneration on exposure to radio waves. Increased production of reactive oxygen species due to exhaustion of enzymatic and non-enzymatic antioxidants and increased lipid peroxidation indicate extensive neurodegeneration in selective areas of CA1, CA3, DG, and the cerebral cortex. This extensive neuronal damage results in alterations in behavior related to memory and learning. Keywords: Antioxidant enzymes, Anxiety, Behavior, Lipid peroxidation, Mobile radiations, Neurodegeneration
... The effect of an acute 30 min head exposure to a 2.573 GHz LTE signal on the global neuronal networks activity was recently explored in healthy human volunteers. Using resting state functional resonance magnetic imaging, it was observed that the LTE exposure could induce alterations in spontaneous slow frequency fluctuations and in intraregional or interregional connectivities, whereas spatial peak SAR levels averaged over 10 g of tissue were estimated to vary from 0.42 to 1.52 W/kg, according to subjects [7][8][9] . Under similar exposure conditions (30 min duration, peak SAR level estimated at 1.34 W/kg using a representative human head model) electroencephalographic analyses indicated reduced spectral powers and interhemispheric coherences in the alpha and beta bands 10 . ...
Article
Full-text available
Increased needs for mobile phone communications have raised successive generations (G) of wireless technologies, which could differentially affect biological systems. To test this, we exposed rats to single head-only exposure of a 4G long-term evolution (LTE)-1800 MHz electromagnetic field (EMF) for 2 h. We then assessed the impact on microglial space coverage and electrophysiological neuronal activity in the primary auditory cortex (ACx), under acute neuroinflammation induced by lipopolysaccharide. The mean specific absorption rate in the ACx was 0.5 W/kg. Multiunit recording revealed that LTE-EMF triggered reduction in the response strength to pure tones and to natural vocalizations, together with an increase in acoustic threshold in the low and medium frequencies. Iba1 immunohistochemistry showed no change in the area covered by microglia cell bodies and processes. In healthy rats, the same LTE-exposure induced no change in response strength and acoustic threshold. Our data indicate that acute neuroinflammation sensitizes neuronal responses to LTE-EMF, which leads to an altered processing of acoustic stimuli in the ACx.
... The effect of an acute 30 min head exposure to a 2.573 GHz LTE signal on the global neuronal networks activity was recently explored in healthy human volunteers. Using resting state functional resonance magnetic imaging, it was observed that the LTE exposure induced alterations in spontaneous slow frequency fluctuations and in intraregional or interregional connectivities (Lv et al. 2014;Wei et al. 2019;Yang et al. 2021). Under similar exposure conditions, electroencephalographic analyses indicated reduced spectral powers and interhemispheric coherences in the alpha and beta bands (Yang et al. 2017). ...
Preprint
Full-text available
Increased needs in mobile phone communications have raised successive generations (G) of wireless technologies, which could differentially affect biological systems. We have assessed how a single 2h head-only exposure to a 4G long term evolution (LTE)-1800 MHz electromagnetic field (EMF) impacts on the microglial space coverage and the electrophysiological neuronal activity in the primary auditory cortex (ACx) in rats submitted to an acute neuroinflammation induced by lipopolysaccharide. The mean specific absorption rate in the ACx was 0.5 W/kg. Multiunit recording revealed that LTE-EMF triggered reduction in the response strength to pure tones and to natural vocalizations, together with an increase in acoustic threshold in the low and medium frequencies. Iba1 immunohistochemistry showed no change in the area covered by microglia cell bodies and processes. In healthy rats, the same LTE-exposure induced no change in response strength and acoustic threshold. Our data indicate that an acute neuroinflammation sensitize neuronal responses to LTE-EMF, which leads to an altered processing of acoustic stimuli in the ACx.
... We attributed the difference to the distinctive brain parcellation or the metrics using in these studies. For example, Lv et al. (35) demonstrated that short-term LTE EMF exposure would modulate the interhemispheric homotopic functional connectivity, specifically decreasing amplitude of low frequency fluctuations (ALFF) in resting state around the medial frontal gyrus and the paracentral lobule during the real exposure (36). The study was based on brain anatomy of larger scale (hemisphere). ...
Article
Full-text available
Neurophysiological effect of human exposure to radiofrequency signals has attracted considerable attention, which was claimed to have an association with a series of clinical symptoms. A few investigations have been conducted on alteration of brain functions, yet no known research focused on intrinsic connectivity networks, an attribute that may relate to some behavioral functions. To investigate the exposure effect on functional connectivity between intrinsic connectivity networks, we conducted experiments with seventeen participants experiencing localized head exposure to real and sham time-division long-term evolution signal for 30 min. The resting-state functional magnetic resonance imaging data were collected before and after exposure, respectively. Group-level independent component analysis was used to decompose networks of interest. Three states were clustered, which can reflect different cognitive conditions. Dynamic connectivity as well as conventional connectivity between networks per state were computed and followed by paired sample t -tests. Results showed that there was no statistical difference in static or dynamic functional network connectivity in both real and sham exposure conditions, and pointed out that the impact of short-term electromagnetic exposure was undetected at the ICNs level. The specific brain parcellations and metrics used in the study may lead to different results on brain modulation.
... Since the spread of the wireless connection in the radio frequency range a series of researches on its biological activity was carried out; the results of the research, despite their contradictoriness, show that EMR RF may influence negatively the health status. As of today we can single out a series of works, demonstrating the risk of origin of insomnia [12], depression, hypertension [10], the influence on the activity of some areas of the human brain [15], the lowering of humans and animals' spermatozoa mobility [14]. And an absolutely special situation emerged due to the extensive spread (in most cases irradiating us without notification) of the Wi-Fi standard wireless connection. ...
... The decrease in the intensity of the effect at lower level about four times is much less than Trunk et al. 20132.18 Lv, Su et al. 2014Lv, Chen et al. 20142-1.5 Croft et al. 2010Leung et al. 2011;Lowden et al. 2011;Vecsei et al. 2013;Sauter et al. 2015;Lustenberger et al. 2015;Verrender et al. 2016;Yang et al. 2017;Vecsei et al. 2018;Dalecki et al. 2018;Loughran et al. 2019;Lowden et al. 2019Stefanics et al. 2008Croft et al. 2010;Riddervold et al. 2010;Danker-Hopfe et al. 2011;Nakatani-Enomoto et al. 2013Trunk et al. 2015;Eggert et al. 2015 1.5-1 Hung et al. 2007;Krause et al. 2007;Luria et al. 2009;Wiholm et al. 2009;Lustenberger et al. 2015;Verrender et al. 2016;Yang et al. 2017;Dalecki et al. 2018;Loughran et al. 2019Fritzer et al. 2007Haarala et al. 2007;Krause et al. 2007;Kleinlogel et al. 2008aKleinlogel et al. , 2008bHillert et al. 2008;Kwon et al. 2009Kwon et al. , 2010Loughran et al. 2013 1-0.5 Bardasano et al. 2007;Curcio et al. 2008;Croft et al. 2008;de Tommaso et al. 2009;Curcio et al. 2009;Croft et al. 2010;Vecchio et al. 2010;Leung et al. 2011;Ghosn et al. 2015;Curcio et al. 20150.5-0.1 Bachmann, Tomson, et al. 2007Bachmann et al. 2018: Hung et al. 2007Hinrikus Bachmann, Lass, Tomson, et al. 2008;Hinrikus, Bachmann, Lass, Karai, et al. 2008;Hinrikus et al. 2009;Suhhova et al. 2009;Lustenberger et al. 2013;Suhhova et al. 2013;Hinrikus et al. 2017Regel, Gottselig, et al. 2007Eltiti et al. 2009 <0 expected according to the decrease of SAR (100 times). The relative decrease of the effect is rather close to the change in field strength (10 times). ...
Article
Purpose: This review aims to estimate the threshold of radiofrequency electromagnetic field (RF EMF) effects on human brain based on analyses of published research results. To clarify the threshold of the RF EMF effects, two approaches have been applied: 1) the analyses of restrictions in sensitivity for different steps of the physical model of low-level RF EMF mechanism and 2) the analyses of experimental data to clarify the dependence of the RF EMF effect on exposure level based on the results of published original neurophysiological and behavioral human studies for 15 years 2007-2021. Conclusions: The analyses of the physical model of non-thermal mechanisms of RF EMF effect leads to conclusion that no principal threshold of the effect can be determined. According to the review of experimental data, the rate of detected RF EMF effects is 76.7% in resting EEG studies, 41.7% in sleep EEG and 38.5% in behavioral studies. The changes in EEG probably appear earlier than alterations in behavior become evident. The lowest level of RF EMF at which the effect in EEG was detected is 2.45 V/m (SAR =0.003 W/kg). There is a preliminary indication that the dependence of the effect on the level of exposure follows rather field strength than SAR alterations. However, no sufficient data are available for clarifying linearity-nonlinearity of the dependence of effect on the level of RF EMF. The finding that only part of people are sensitive to RF EMF exposure can be related to immunity to radiation or hypersensitivity. The changes in EEG caused by RF EMF appeared similar in the majority of analyzed studies and similar to these in depression. The possible causal relationship between RF EMF effect and depression among young people is highly important problem.
... Although the disturbing 40 Hz component was removed from the EEG by filtering it is not clear whether parameter shifts or other interference with the EEG recording system may account for at least a part of the differences observed in this single-blind study. Lv et al. (2014) used resting state BOLD fMRI signals (BOLD: blood oxygen level dependent) to analyse possible effects of a 30-min RF-EMF exposure to an LTE signal (2.573 GHz) on spontaneous low frequency oscillations. The study design was double-blind, crossover, randomized and counter-balanced. ...
... Using both ALFF and fALFF led to different results in our sample. As these are different measures, different outcomes are possible and have been reported in previous studies (Cui et al., 2014;Lv et al., 2014). Given the higher sensitivity of fALFF compared to ALFF it is not surprising that we found stronger differences using this measure, however these results might be less stable (Zou et al., 2008;Zuo et al., 2010). ...
Article
Full-text available
Auditory hallucinations, the perception of a sound without a corresponding source, are common in people with hearing impairment. Two forms can be distinguished: simple (i.e., tinnitus) and complex hallucinations (speech and music). Little is known about the precise mechanisms underlying these types of hallucinations. Here we tested the assumption that spontaneous activity in the auditory pathways, following deafferentation, underlies these hallucinations and is related to their phenomenology. By extracting (fractional) Amplitude of Low Frequency Fluctuation ([f]ALFF) scores from resting state fMRI of 18 hearing impaired patients with complex hallucinations (voices or music), 18 hearing impaired patients with simple hallucinations (tinnitus or murmuring), and 20 controls with normal hearing, we investigated differences in spontaneous brain activity between these groups. Spontaneous activity in the anterior and posterior cingulate cortex of hearing-impaired groups was significantly higher than in the controls. The group with complex hallucinations showed elevated activity in the bilateral temporal cortex including Wernicke's area, while spontaneous activity of the group with simple hallucinations was mainly located in the cerebellum. These results suggest a decrease in error monitoring in both hearing-impaired groups. Spontaneous activity of language-related areas only in complex hallucinations suggests that the manifestation of the spontaneous activity represents the phenomenology of the hallucination. The link between cerebellar activity and simple hallucinations, such as tinnitus, is new and may have consequences for treatment.
... It has been confirmed that the people living in the vicinity of mobile phone base stations suffer from headache, memory changes, dizziness, tremors, depressive symptoms, and sleep disturbances (Abdel-Rassoul et al. 2007;Behari 2010). There are many reports that confirm the effects of CP-emitted EMF on brain function (Lowden et al. 2011;Volkow et al. 2011;Schmid et al. 2012;Vecchio et al. 2012;Lv et al. 2014;Ghosn et al. 2015;Roggeveen et al. 2015;Bhangari et al. 2018). Furthermore, DNA breakage (Lixia et al. 2006;Sun et al. 2006;Pandey et al. 2017;Alkis et al. 2019); altered circadian rhythm of melatonin secretion (Wilson et al. 1990;Touitou and Selmaoui 2012); altered sleep quality (Akerstedt et al. 1999;Graham and Cook 1999); nausea, headache, dizziness, irritability, discomfort, appetite loss, depression, memory loss, difficulty in concentration (Schreier et al. 2006); poor cognitive performance (Sienkiewicz et al. 2005;Bak et al. 2010;Deniz et al. 2017); childhood brain cancer (Wiedemann and Schütz 2011); reproduction and infertility (Altun et al. 2018;Fatehi et al. 2018;Grigor'ev et al. 2018;Kesari et al. 2018); auditory system (Çeliker et al. 2017); and neurological disorders (Valentini et al. 2007) have been attributed to EMF. ...
Article
We examined the effects of short- and long-duration exposure to cell phone radiation (CPR) on phototactic response (PR) and circadian characteristics of locomotor-activity rhythm, respectively, in zebrafish. We exposed four groups (10 in each) randomly selected fish to CPR emitted by a 2300 MHz 4G cell phone for 0.5 h, 1 h, 2 h, 3 h, and 4 h duration at two different time points of a day, i.e. morning and evening, to assess the PR. We also studied the effects of 1 week CPR exposure on circadian rhythm in locomotor activity pattern in eight singly housed zebrafish. We had eight singly housed sham-exposed zebrafish as the control. Results of two-way ANOVA revealed statistically significant effects of the factors exposure time and exposure duration on the PR of zebrafish. Fish exhibited photo-positive response till 2 h following morning exposure, and thereafter, showed photo-negative response with increased duration of exposure. During evening exposure, the fish were mostly photo-negative. However, 1 week exposure to CPR did not produce any significant effects on the circadian characteristics of locomotor activity rhythm. It is concluded that the CPR might alter phototaxis, but not the parameters of circadian rhythm in locomotor activity pattern of zebrafish.
... Studies that did not report basic power spectra information and/or amplitudes for the EEG (frequency bands) but used a more complex outcome parameter, e.g. spectral coherence, were also not considered in the present study: Lebedeva et al. [2000], Vecchio et al. [2007Vecchio et al. [ , 2010Vecchio et al. [ , 2012b, and Lv et al. [2014]. This results in a total of 22 eligible studies for the present review. ...
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The results of studies on possible effects of radiofrequency electromagnetic fields (RF‐EMFs) on human waking electroencephalography (EEG) have been quite heterogeneous. In the majority of studies, changes in the alpha‐frequency range in subjects who were exposed to different signals of mobile phone‐related EMF sources were observed, whereas other studies did not report any effects. In this review, possible reasons for these inconsistencies are presented and recommendations for future waking EEG studies are made. The physiological basis of underlying brain activity, and the technical requirements and framework conditions for conducting and analyzing the human resting‐state EEG are discussed. Peer‐reviewed articles on possible effects of EMF on waking EEG were evaluated with regard to non‐exposure‐related confounding factors. Recommendations derived from international guidelines on the analysis and reporting of findings are proposed to achieve comparability in future studies. In total, 22 peer‐reviewed studies on possible RF‐EMF effects on human resting‐state EEG were analyzed. EEG power in the alpha frequency range was reported to be increased in 10, decreased in four, and not affected in eight studies. All reviewed studies differ in several ways in terms of the methodologies applied, which might contribute to different results and conclusions about the impact of EMF on human resting‐state EEG. A discussion of various study protocols and different outcome parameters prevents a scientifically sound statement on the impact of RF‐EMF on human brain activity in resting‐state EEG. Further studies which apply comparable, standardized study protocols are recommended. Bioelectromagnetics. 2019;1–28. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.
... Moreover, it is experimentally proved that the exposure to the radio radiations can affect the cell growth and disturb normal fetal development [19]. Furthermore, some researchers found that 4 G wireless radiations reduce the brain functionality [20]. In addition, several potential dangers include fertility problems [21], and cardiac stress [22]. ...
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In order to respond to the increasing demand of capacity and bandwidth caused by the high number of wireless applications and users, LiFi technology was introduced. It uses the visible light spectrum instead of the radio spectrum to transmit data wirelessly through the illumination of LED lamps. The main advantage of this technology is to provide wireless communications with high data rates. Other advantages include efficiency, availability, security and safety. Also, this technology uses free unlicensed spectrum, and it is cost-effective. Additionally, unlike RF systems, no multipath fading and the transmitter and receiver circuits are not complex. However, LiFi has several issues, which include high path loss, sensitivity to blockages and Non-line-of-sight (NLOS) situations. Probably, the biggest issue of LiFi is the uplink communication which is difficult to implement due to practical and cost reasons. Several future applications of this technology include places where RF is restricted such as hospitals and airplanes. Also, it can be used for traffic management, underwater communication, and outdoor access to the Internet. Moreover, it can be combined with WiFi technology either in hybrid technique or aggregated technique. It is found that later technique gives better results. Another possible application is the optical attocells. It is found that the hexagonal cells model is the best for deterministic deployments of optical APs, whereas the hard-core point process (HCPP) model is the best for random deployments. Furthermore, LiFi can be used for multiuser access with high data rate by using non-orthogonal multiple access (NOMA) technique. Due to the great features of LiFi, more applications and everyday life devices will adopt this technology in the future. However, Because of its limitations, it may not totally replace RF technology, but they will work collaboratively to achieve a better performance.
... This metric measures the relative contribution of the low frequency oscillatory (LFO) amplitude in a specific frequency band to the total frequency band, thus reflecting the relative intensity of LFOs. Previous studies have applied both methods to the same sample group and obtain different results (Cui et al., 2014;Lv et al., 2014), which suggests an inherent difference between these two indices measuring neural activity. In recent years, both parameters have been applied to evaluate the cerebral intrinsic activity in normal subjects in an eyes-open versus an eyes-closed state (Yang et al., 2007) and in disorders such as schizophrenia (Huang et al., 2010), depression (Sambataro et al., 2014) and ADHD (Fei Li et al., 2014). ...
... LFOs can be differentiated from other oscillatory phenomenon in rodent animal, such as the heart beat and respiration, because of their slow fluctuations. They can be modulated by hypercapnia, different pharmacologic and pathologic conditions, functional stimulation and acute electromagnetic fields exposure [6], [7]. Mayhew et al. found a pervasive LFO in both brain parenchyma and microvasculature with OI and laser Doppler flow meter concurrently, and found that in amplitude the spontaneous LFOs was occasionally greater than the response signal [8]. ...
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Spontaneous low frequency oscillations (LFOs) have been found in cerebral hemodynamics and metabolisms with different techniques and species. In this study, optical imaging system was employed to detect hemodynamic changes in the anesthetized rat cerebral cortex. Under 546-nm or 630-nm illumination, the phase and amplitude distributions of spontaneous LFOs were investigated before and after single whisker stimulation. Spontaneous LFOs can be modulated by the stimulation, and we found obvious synchronization of phase distributions at around 0.1-hz in two hemispheres. After stimulation, the amplitude of spontaneous LFOs in the region of arteries was increased under 546-nm illumination, while the amplitude of spontaneous LFOs in the region of veins was increased under 630-nm illumination. The precise mechanisms and roles of spontaneous LFOs remain unclear. We speculated the extensive synchronization of LFO phases may be associated with the brain function of global alertness and vigilance.
... /news/what-s-happening-around-the-world/4g-an-increase-of-50-exposure-to-electromagnetic-waves.html) [10]. Distance within 300 meter radius of a mobile tower is considered to be a high radiation zone and people living there are more prone to ill-effects of EM radiations. ...
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In the present developed world, all of us are flooded with electromagnetic radiations (EMR) emanating from generation and transmission of electricity, domestic appliances and industrial equipments, to telecommunications and broadcasting. We have been exposed to EMR for last many decades; however their recent steady increase from artificial sources has been reported as millions of antennas and satellites irradiate the global population round the clock, year round. Needless to say, these are so integral to modern life that interaction with them on a daily basis is seemingly inevitable; hence, the EMR exposure load has increased to a point where their health effects are becoming a major concern. Delicate and sensitive electrical system of human body is affected by consistent penetration of electromagnetic frequencies causing DNA breakages and chromosomal aberrations. Technological innovations came with Pandora's Box of hazardous consequences including neurodegenerative disorders, hearing disabilities, diabetes, congenital abnormalities, infertility, cardiovascular diseases and cancer to name few, all on a sharp rise. Electromagnetic non-ionizing radiations pose considerable health threat with prolonged exposure. Mobile phones are usually held near to the brain and manifest progressive structural or functional alterations in neurons leading to neurodegenerative diseases and neuronal death. This has provoked awareness among both the general public and scientific community and international bodies acknowledge that further systematic research is needed. The aim of the present review was to have an insight in whether and how cumulative electro-magnetic field exposure is a risk factor for neurodegenerative disorders.
... Resting-state fMRI has become an increasingly popular technique of fMRI since the study of Biswal et al. (1995). It has been used extensively to study ongoing spontaneous neuronal activity (Weisskoff and Rosen, 1995;Ogawa, 2012;Lv et al., 2014). Resting-state fMRI, which does not require people to perform any task and avoids any paradigm design, might be a good method to explore the gender-difference effect in MDD patients. ...
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We examined the gender-difference effect on abnormal spontaneous neuronal activity of male and female major depressive disorder (MDD) patients using the amplitude of low-frequency fluctuation (ALFF) and the further clarified the relationship between the abnormal ALFF and differences in MDD prevalence rates between male and female patients. Fourteen male MDD patients, 13 female MDD patients and 15 male and 15 female well matched healthy controls (HCs) completed this study. The ALFF approach was used, and Pearson correlation was conducted to observe a possible clinical relevance. There were widespread differences in ALFF values between female and male MDD patients, including some important parts of the frontoparietal network, auditory network, attention network and cerebellum network. In female MDD patients, there was a positive correlation between average ALFF values of the left postcentral gyrus and the severity of weight loss symptom. The gender-difference effect leading to abnormal brain activity is an important underlying pathomechanism for different somatic symptoms in MDD patients of different genders and is likely suggestive of higher MDD prevalence rates in females. The abnormal ALFF resulting from the gender-difference effect might improve our understanding of the differences in prevalence rates between male and female MDD patients from another perspective.
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Technology has allowed us to go wireless and avoid the hassle of cables. We can now remotely turn the TVs on, start a coffee machine, and monitor babies using wireless technology. At the same time, we are exposed to unprecedented levels of electromagnetic radiation from wireless signals 24/7. is devices like mobile, TV wireless devices are safe. They are two controversial statements running till today. One group of experts saying it is safe; another group says effects on human beings a lot. This paper gives clarity how its effects on human beings, based on experimental results and survey.
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With the advancement of wireless technologies and electronic/electrical devices, humans are exposed to more complicated electric, magnetic, and electromagnetic fields (EMF), which has raised public concerns on potential health effects. Researchers have recently conducted a series of studies on diverse exposure scenarios. In addition, international standard organizations have revised safety guidelines and standards (1). These recent results and practices can enhance our knowledge in assessing health risks from the exposure to EMF (2). This Research Topic consists of 14 articles (one review article, two brief research report articles, and 11 original research articles) published in the Radiation and Health section of Frontiers in Public Health.
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Purpose The deployment of new 5G NR technology has significantly raised public concerns in possible negative effects on human health by radiofrequency electromagnetic fields (RF EMF). The current review is aimed to clarify the differences between possible health effects caused by the various generations of telecommunication technology, especially discussing and projecting possible health effects by 5G. The review of experimental studies on the human brain over the last fifteen years and the discussion on physical mechanisms and factors determining the dependence of the RF EMF effects on frequency and signal structure have been performed to discover and explain the possible distinctions between health effects by different telecommunication generations. Conclusions The human experimental studies on RF EMF effects on the human brain by 2G, 3G and 4G at frequencies from 450 to 2500 MHz were available for analyses. The search for publications indicated no human experimental studies by 5G nor at the RF EMF frequencies higher than 2500 MHz. The results of the current review demonstrate no consistent relationship between the character of RF EMF effects and parameters of exposure by different generations (2G, 3G, 4G) of telecommunication technology. At the RF EMF frequencies lower than 10 GHz, the impact of 5G NR FR1 should have no principal differences compared to the previous generations. The radio frequencies used in 5G are even higher and the penetration depths of the fields are smaller, therefore the effect is rather lower than at previous generations. At the RF EMF frequencies higher than 10 GHz, the mechanism of the effects might differ and the impact of 5G NR FR2 becomes unpredictable. Existing knowledge about the mechanism of RF EMF effects at millimeter waves lacks sufficient experimental data and theoretical models for reliable conclusions. The insufficient knowledge about the possible health effects at millimeter waves and the lack of in vivo experimental studies on 5G NR underline an urgent need for the theoretical and experimental investigations of health effects by 5G NR, especially by 5G NR FR2.
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The adoption of 5G technology networks provide users opportunities for faster broadband speed and reduced latency. Two memory experiments are considered in the context of future use of 5G technology for mobile phones. 120 participants are tested. A significant result of an effect is found in the change detection task. No effect is found in the Stroop task. Over the last 20 years many studies have shown inconsistent results of effect on cognitive performance. With the roll out of 5G, it is important to investigate this area further to gain a clear understanding of what these effects are. Caution is recommended for use of 5G mobile phones.
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Whether you are the usage of wireless net in an espresso shop, stealing it from the man subsequent door, or competing for bandwidth at a conference, you have probable gotten pissed off at the gradual speeds you face when extra than one system is tapped into the network. But radio waves are clearly one section of the spectrum that can raise our data. What if we can also wish to use exclusive waves to surf the internet? One German physicist. Harald Haas, has come up with a reply he calls “Data Through Illumination”—taking the fiber out of fiber optics with the resource of potential of sending records thru an LED moderate bulb that varies in intensity faster than the human eye can follow. And safety would be a snap—if you can’t see the light, you can’t get entry to the data. Li-Fi is a VLC, considered slight communication, technological perception developed by way of using a crew of scientists collectively with Dr Gordon Povey, Prof. Harald Haas and Dr Mostafa Afgani at the University of Edinburgh. The time size Li-Fi used to be coined via skill of the use of Prof. Haas when he amazed humans by means of potential of means of streaming high- definition video from a modern-day LED lamp, at TED Global in July 2011. Unseen with the resource of practicable of the human eye, this variant is used to elevate high-speed data,” says Dr Povey, Product Manager of the University of Edinburgh's Li-Fi Program ‘D-Light Project’.
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With the expanding use of wireless cellular networks, concerns have been communicated about the possible interaction of electromagnetic radiation with the human life, explicitly, the mind and brain. Mobile phones emanate radio frequency waves, a type of non-ionizing radiation, which can be absorbed by tissues nearest to where the telephone is kept. The effects on neuronal electrical activity, energy metabolism, genomic responses, neurotransmitter balance, blood–brain barrier permeability, mental psychological aptitude, sleep, and diverse cerebrum conditions including brain tumors are assessed. Health dangers may likewise develop from use of cellular communication, for instance, car accidents while utilizing the device while driving. These indirect well-being impacts surpass the immediate common troubles and should be looked into in more detail later on. In this chapter, we outline the possible biological impacts of EMF introduction on human brain.
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Mobile phones are indispensable for daily life, and the adverse effects of the electromagnetic field (EMF) emitted by mobile phones have been a great concern. We studied the effects of long-term evolution (LTE) -like EMF for 30 min on an awake electroencephalogram (EEG). Thirty-eight healthy volunteers, aged 20 to 36 years old, participated in this study. The maximum local SAR (specific absorption rate) averaged over 10-g mass was 2.0 W/kg. The EEG was recorded before and after real or sham exposures. The effects of exposure conditions (real or sham) and the recording time (before, during, and after exposure) on each EEG power spectrum of θ, α, and β frequency ranges were analyzed. The θ and α band waves were enhanced after both exposure conditions. These results may be explained by the participants' drowsiness during the EEG recording in both exposures. We conclude that an LTE-like exposure for 30 min in this study showed no detectable harmful effects on awake EEGs in healthy humans.
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Although mobile phone (MP) use has been steadily increasing in the last decades and similar positive trends are expected for the near future, systematic investigations on neurophysiological and cognitive effects caused by recently developed technological standards for MPs are scarcely available. Here, we investigated the effects of radiofrequency (RF) fields emitted by new-generation mobile technologies, specifically, Universal Mobile Telecommunications System (UMTS) and Long-Term Evolution (LTE), on intrinsic scalp EEG activity in the alpha band (8–12 Hz) and cognitive performance in the Stroop test. The study involved 60 healthy, young-adult university students (34 for UMTS and 26 for LTE) with double-blind administration of Real and Sham exposure in separate sessions. EEG was recorded before, during and after RF exposure, and Stroop performance was assessed before and after EEG recording. Both RF exposure types caused a notable decrease in the alpha power over the whole scalp that persisted even after the cessation of the exposure, whereas no effects were found on any aspects of performance in the Stroop test. The results imply that the brain networks underlying global alpha oscillations might require minor reconfiguration to adapt to the local biophysical changes caused by focal RF exposure mimicking MP use.
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There has been increasing use of mobile phones and concerns about exposure to radiofrequency electromagnetic fields (RF EMF). The aim of this study was to investigate lateralised effects of exposure on cognitive performance. Forty-eight healthy young males and females performed a dot detection task in three phone conditions, active right, active left and inactive; the completion of a well-being test followed this. Results show that reaction times (RT) are faster when the phones are switched off. In addition, RT is faster for the active phone in the right visual field when it is positioned over the right hemisphere than when the phone is positioned over the right hemisphere and in the left visual field. Also, when the active phone is over the left hemisphere, participants report greater sadness compared to the active phone over the right hemisphere. Previous studies on assymetrical brain function suggest deactivation of the left hemisphere increases negative affect. The combination of the results in the current study suggest a potential mood effect is operating.
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RLS is a best practice and represent an important surveillance and awareness-raising tool that assess how health systems behave. This research focuses on two key elements related to reporting systems: the learning component and dissemination strategies regarding the lessons learned to physicians and the accuracy of event analysis.
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Although mobile phone (MP) use has been steadily increasing in the last decades and similar positive trends are expected for the near future, systematic investigations on neurophysiological and cognitive effects caused by recently developed technological standards for MPs are scarcely available. Here, we investigated the effects of radiofrequency (RF) fields emitted by new-generation mobile technologies, specifically, Universal Mobile Telecommunications System (UMTS) and Long-Term Evolution (LTE), on intrinsic scalp EEG activity in the alpha band (8-12 Hz) and cognitive performance in the Stroop test. The study involved 60 healthy, young-adult university students (34 for UMTS and 26 for LTE) with double-blind administration of Real and Sham exposure in separate sessions. EEG was recorded before, during and after RF exposure, and Stroop performance was assessed before and after EEG recording. Both RF exposure types caused a notable decrease in the alpha power over the whole scalp that persisted even after the cessation of the exposure, whereas no effects were found on any aspects of performance in the Stroop test. The results imply that the brain networks underlying global alpha oscillations might require minor reconfiguration to adapt to the local biophysical changes caused by focal RF exposure mimicking MP use.
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Objectives: The goals of this study were: (1) to obtain basic information about the effects of long-term use of mobile phones on cytological makeup of the hippocampus in rat brains (2) to evaluate the effects on antioxidant status, and (3) to evaluate the effects on cognitive behavior particularly on learning and memory. Methods: Rats (age 30 days, 120 ± 5 g) were exposed to 900 MHz radio waves by means of a mobile hand set for 4 hours per day for 15 days. Effects on anxiety, spatial learning, and memory were studied using the open field test, the elevated plus maze, the Morris water maze (MWM), and the classic maze test. Effects on brain antioxidant status were also studied. Cresyl violet staining was done to assess the neuronal damage. Result: A significant change in behavior, i.e., more anxiety and poor learning was shown by test animals as compared to controls and sham group. A significant change in the level of antioxidant enzymes and non-enzymatic antioxidants, and an increase in lipid peroxidation were observed in the test rats. Histological examination showed neurodegenerative cells in hippocampal sub regions and the cerebral cortex. Discussion: Thus our findings indicate extensive neurodegeneration on exposure to radio waves. Increased production of reactive oxygen species due to exhaustion of enzymatic and non-enzymatic antioxidants and increased lipid peroxidation indicate extensive neurodegeneration in selective areas of CA1, CA3, DG, and the cerebral cortex. This extensive neuronal damage results in alterations in behavior related to memory and learning.
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This paper presented the dosimetric studies in the research for evaluating the relationship between the LTE exposure and the brain regional activation. Measurement was made for the net power delivered to the dipoles for each exposed volunteer. During the exposure experiment, the exposed power was strictly controlled to achieve a constant exposure dose for each person. The numerical head model of each volunteer was reconstructed basing on the MRI images. FDTD simulation was performed to calculate the realistic power distribution in different head regions for all the exposed volunteers. Effects with the existence of the EEG electrode and leads on the head during the exposure were taken into considered in term of local SAR and regional induced current to prevent abnormal results. The dosimetric results were therefore applied for LTE EMF exposure related brain activation research.
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Standing Chinese adult anatomical models are obtained from supine-postured cadaver slices. This paper presents the dosimetric differences between the supine and the standing postures over wide band frequencies and various incident configurations. Both the body level and the tissue/organ level differences are reported for plane wave and the 3T magnetic resonance imaging radiofrequency electromagnetic field exposure. The influence of posture on the whole body specific absorption rate and tissue specified specific absorption rate values is discussed.
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Digital human models are frequently obtained from supine-postured medical images or cadaver slices, but many applications require standing models. This paper presents the work of reconstructing standing Chinese adult anatomical models from supine postured slices. Apart from the previous studies, the deformation works on 2-D segmented slices. The surface profile of the standing posture is adjusted by population measurement data. A non-uniform texture amplification approach is applied on the 2-D slices to recover the skin contour and to redistribute the internal tissues. Internal organ shift due to postures is taken into account. The feet are modified by matrix rotation. Then, the supine and standing models are utilised for the evaluation of electromagnetic field exposure over wide band frequency and different incident directions.
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The digital human model is a key element in evaluating the electromagnetic field (EMF) exposure. This paper proposes the application of simplified segmented human models for EMF exposure compliance evaluation with the whole body and the localised limits. The method is based on the fact that most of the EMF power absorption is concentrated in several major tissues. Two kinds of human models were simply (the proposed method) and precisely segmented from two sets of whole body magnetic resonance imaging (MRI) scanned images. The whole body average-specific absorption rate (WBA-SAR) and the peak localised SAR averaging over 10 g tissues for the two kinds of models are calculated for various exposure configurations. The results confirmed the efficiency and the validity of the proposed method. The application as evaluating the MRI radiofrequency EMF exposure is also discussed in the paper.
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Analytic tools for addressing spontaneous brain activity, as acquired with fMRI during the “resting-state,” have grown dramatically over the past decade. Along with each new technique, novel hypotheses about the functional organization of the brain are also available to researchers. We review six prominent categories of resting-state fMRI data analysis: seed-based functional connectivity, independent component analysis, clustering, pattern classification, graph theory, and two “local” methods. In surveying these methods, we address their underlying assumptions, methodologies, and novel applications. KeywordsResting state-Functional connectivity-Brain networks
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This paper presents the work of constructing Chinese adult anatomical models and their application in evaluation of radio frequency (RF) electromagnetic field exposures. The original dataset was obtained from photos of the sliced frozen cadavers from the Chinese Visible Human Project. Details of preparing the cadaver for slicing procedures which may influence the anatomical structures are discussed. Segmentation and reconstruction were performed mainly manually by experienced anatomists. The reconstructed models represent the average Chinese in their twenties and thirties. The finest resolution for the models is 1 × 1 × 1 mm(3) with 90 identified tissues/organs for the female and 87 identified tissues/organs for the male. Tiny anatomical structures such as blood vessels with diameters of 1 mm, various glands and nerves were identified. Whole-body-averaged specific absorption rate (WBSAR) from 20 MHz to 5.8 GHz was calculated with the finite-difference time-domain method for different RF exposure configurations. The WBSAR results are consistent with those from other available models. Finally, some details about the anatomical models are discussed.
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Resting-state functional magnetic resonance imaging (fMRI) has attracted more and more attention because of its effectiveness, simplicity and non-invasiveness in exploration of the intrinsic functional architecture of the human brain. However, user-friendly toolbox for "pipeline" data analysis of resting-state fMRI is still lacking. Based on some functions in Statistical Parametric Mapping (SPM) and Resting-State fMRI Data Analysis Toolkit (REST), we have developed a MATLAB toolbox called Data Processing Assistant for Resting-State fMRI (DPARSF) for "pipeline" data analysis of resting-state fMRI. After the user arranges the Digital Imaging and Communications in Medicine (DICOM) files and click a few buttons to set parameters, DPARSF will then give all the preprocessed (slice timing, realign, normalize, smooth) data and results for functional connectivity, regional homogeneity, amplitude of low-frequency fluctuation (ALFF), and fractional ALFF. DPARSF can also create a report for excluding subjects with excessive head motion and generate a set of pictures for easily checking the effect of normalization. In addition, users can also use DPARSF to extract time courses from regions of interest.
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Resting state functional connectivity MRI (fcMRI) is widely used to investigate brain networks that exhibit correlated fluctuations. While fcMRI does not provide direct measurement of anatomic connectivity, accumulating evidence suggests it is sufficiently constrained by anatomy to allow the architecture of distinct brain systems to be characterized. fcMRI is particularly useful for characterizing large-scale systems that span distributed areas (e.g., polysynaptic cortical pathways, cerebro-cerebellar circuits, cortical-thalamic circuits) and has complementary strengths when contrasted with the other major tool available for human connectomics-high angular resolution diffusion imaging (HARDI). We review what is known about fcMRI and then explore fcMRI data reliability, effects of preprocessing, analysis procedures, and effects of different acquisition parameters across six studies (n = 98) to provide recommendations for optimization. Run length (2-12 min), run structure (1 12-min run or 2 6-min runs), temporal resolution (2.5 or 5.0 s), spatial resolution (2 or 3 mm), and the task (fixation, eyes closed rest, eyes open rest, continuous word-classification) were varied. Results revealed moderate to high test-retest reliability. Run structure, temporal resolution, and spatial resolution minimally influenced fcMRI results while fixation and eyes open rest yielded stronger correlations as contrasted to other task conditions. Commonly used preprocessing steps involving regression of nuisance signals minimized nonspecific (noise) correlations including those associated with respiration. The most surprising finding was that estimates of correlation strengths stabilized with acquisition times as brief as 5 min. The brevity and robustness of fcMRI positions it as a powerful tool for large-scale explorations of genetic influences on brain architecture. We conclude by discussing the strengths and limitations of fcMRI and how it can be combined with HARDI techniques to support the emerging field of human connectomics.
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Usage of mobile phones is rapidly increasing, but there is limited data on the possible effects of electromagnetic field (EMF) exposure on brain physiology. We investigated the effect of EMF vs. sham control exposure on waking regional cerebral blood flow (rCBF) and on waking and sleep electroencephalogram (EEG) in humans. In Experiment 1, positron emission tomography (PET) scans were taken after unilateral head exposure to 30-min pulse-modulated 900 MHz electromagnetic field (pm-EMF). In Experiment 2, night-time sleep was polysomnographically recorded after EMF exposure. Pulse-modulated EMF exposure increased relative rCBF in the dorsolateral prefrontal cortex ipsilateral to exposure. Also, pm-EMF exposure enhanced EEG power in the alpha frequency range prior to sleep onset and in the spindle frequency range during stage 2 sleep. Exposure to EMF without pulse modulation did not enhance power in the waking or sleep EEG. We previously observed EMF effects on the sleep EEG (A. A. Borbély, R. Huber, T. Graf, B. Fuchs, E. Gallmann and P. Achermann. Neurosci. Lett., 1999, 275: 207-210; R. Huber, T. Graf, K. A. Cote, L. Wittmann, E. Gallmann, D. Matter, J. Schuderer, N. Kuster, A. A. Borbély, and P. Achermann. Neuroreport, 2000, 11: 3321-3325), but the basis for these effects was unknown. The present results show for the first time that (1) pm-EMF alters waking rCBF and (2) pulse modulation of EMF is necessary to induce waking and sleep EEG changes. Pulse-modulated EMF exposure may provide a new, non-invasive method for modifying brain function for experimental, diagnostic and therapeutic purposes.
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We assessed the relation between hemodynamic and electrical indices of brain function by performing simultaneous functional MRI (fMRI) and electroencephalography (EEG) in awake subjects at rest with eyes closed. Spontaneous power fluctuations of electrical rhythms were determined for multiple discrete frequency bands, and associated fMRI signal modulations were mapped on a voxel-by-voxel basis. There was little positive correlation of localized brain activity with alpha power (8-12 Hz), but strong and widespread negative correlation in lateral frontal and parietal cortices that are known to support attentional processes. Power in a 17-23 Hz range of beta activity was positively correlated with activity in retrosplenial, temporo-parietal, and dorsomedial prefrontal cortices. This set of areas has previously been characterized by high but coupled metabolism and blood flow at rest that decrease whenever subjects engage in explicit perception or action. The distributed patterns of fMRI activity that were correlated with power in different EEG bands overlapped strongly with those of functional connectivity, i.e., intrinsic covariations of regional activity at rest. This result indicates that, during resting wakefulness, and hence the absence of a task, these areas constitute separable and dynamic functional networks, and that activity in these networks is associated with distinct EEG signatures. Taken together with studies that have explicitly characterized the response properties of these distributed cortical systems, our findings may suggest that alpha oscillations signal a neural baseline with "inattention" whereas beta rhythms index spontaneous cognitive operations during conscious rest.
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This paper presents new definitions for obtaining reproducible results in numerical phone dosimetry. Numerous numerical dosimetric studies have been published about the exposure of mobile phone users which concluded with conflicting results. However, many of these studies lack reproducibility due to shortcomings in the description of the phone positioning. The new approach was tested by two groups applying two different numerical program packages to compare the specific anthropomorphic mannequin (SAM) to 14 anatomically correct head models. A novel definition for the positioning of mobile phones next to anatomically correct head models is given along with other essential parameters to be reported. The definition is solely based on anatomical characteristics of the head. A simple up-to-date phone model was used to determine the peak spatial specific absorption rate (SAR) of mobile phones in SAM and in the anatomically correct head models. The results were validated by measurements. The study clearly shows that SAM gives a conservative estimate of the exposure in anatomically correct head models for head only tissue. Depending on frequency, phone position and head size the numerically calculated 10 g averaged SAR in the pinna can be up to 2.1 times greater than the peak spatial SAR in SAM. Measurements in small structures, such as the pinna, will significantly increase the uncertainty; therefore SAM was designed for SAR assessment in the head only. Whether SAM will provide a conservative value for the pinna depends on the pinna SAR limit of the safety standard considered.
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Mobile phones create a radio-frequency electromagnetic field (EMF) around them when in use, the effects of which on brain physiology in humans are not well known. We studied the effects of a commercial mobile phone on regional cerebral blood flow (rCBF) in healthy humans using positron emission tomography (PET) imaging. Positron emission tomography data was acquired using a double-blind, counterbalanced study design with 12 male subjects performing a computer-controlled verbal working memory task (letter 1-back). Explorative and objective voxel-based statistical analysis revealed that a mobile phone in operation induces a local decrease in rCBF beneath the antenna in the inferior temporal cortex and an increase more distantly in the prefrontal cortex. Our results provide the first evidence, suggesting that the EMF emitted by a commercial mobile phone affects rCBF in humans. These results are consistent with the postulation that EMF induces changes in neuronal activity.
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In recent years a growing number of people have begun to use mobile phone technology. This phenomenon has raised questions and doubts about possible effects on users' brains. This literature review focuses on the human electrophysiological and neuro-metabolic effects of mobile phone (MP)-related electromagnetic fields (EMFs) published in the last 10 years. To this end, all relevant papers have been reported and, subsequently, a literature selection has been carried out by taking several criteria into account, such as: blind techniques, randomization or counter-balancing of conditions and subjects, detail of exposure characteristics and the statistical analyses used. As a result, only the studies meeting the selection criteria have been described, evaluated and discussed further. The main goal of this review is to provide a clear scenario of the most reliable experiments carried out over the last decade and to offer a critical point of view in their evaluation. It is concluded that MP-EMFs may influence normal physiology through changes in cortical excitability and that in future research particular care should be dedicated to both methodological and statistical control, the most relevant criteria in this research field.
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Committee on Identification of Research Needs Relating to Potential Biological or Adverse Health Effects of Wireless Communications Devices, National Research Council of the USA
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The goal of resting-state functional magnetic resonance imaging (FMRI) is to investigate the brain's functional connections by using the temporal similarity between blood oxygenation level dependent (BOLD) signals in different regions of the brain "at rest" as an indicator of synchronous neural activity. Since this measure relies on the temporal correlation of FMRI signal changes between different parts of the brain, any non-neural activity-related process that affects the signals will influence the measure of functional connectivity, yielding spurious results. To understand the sources of these resting-state FMRI confounds, this article describes the origins of the BOLD signal in terms of MR physics and cerebral physiology. Potential confounds arising from motion, cardiac and respiratory cycles, arterial CO2 concentration, blood pressure/cerebral autoregulation, and vasomotion are discussed. Two classes of techniques to remove confounds from resting-state BOLD time series are reviewed: 1) those utilising external recordings of physiology and 2) data-based cleanup methods that only use the resting-state FMRI data itself. Further methods that remove noise from functional connectivity measures at a group level are also discussed. For successful interpretation of resting-state FMRI comparisons and results, noise cleanup is an often over-looked but essential step in the analysis pipeline.
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An MRI time course of 512 echo-planar images (EPI) in resting human brain obtained every 250 ms reveals fluctuations in signal intensity in each pixel that have a physiologic origin. Regions of the sensorimotor cortex that were activated secondary to hand movement were identified using functional MRI methodology (FMRI). Time courses of low frequency (<0.1 Hz) fluctuations in resting brain were observed to have a high degree of temporal correlation (P < 10−3) within these regions and also with time courses in several other regions that can be associated with motor function. It is concluded that correlation of low frequency fluctuations, which may arise from fluctuations in blood oxygenation or flow, is a manifestation of functional connectivity of the brain.
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This extensively revised and expanded third edition of the Artech House bestseller, Computational Electrodynamics: The Finite-Difference Time-Domain Method, offers the most up-to-date and definitive resource on this critical method for solving Maxwell’s equations. Material new to the third edition includes: • Advanced techniques for PSTD; • Advanced techniques for unconditional numerical stability; • Provably stable, hybrid FDTD-FE techniques; • Hardware acceleration for personal computers; • Convolutional PML ABCs; • Four-level, two-electron atomic systems yielding optical gain; • Photonic crystals, second-order nonlinear optical materials, plasmonics, and biophotonics; • Emerging FDTD techniques for global ULF and ELF geophysical models of the Earth. This single resource provides complete guidance on FDTD techniques and applications, from basic concepts, to the current state-of-the-art. It enables professionals to more efficiently and effectively design and analyze key electronics and photonics technologies, including wireless communications devices, high-speed digital and microwave circuits, and integrated optics. It is also ideal for senior-year and graduate-level university courses in computational electrodynamics.
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The energy requirements of the brain are very high, and tight regulatory mechanisms operate to ensure adequate spatial and temporal delivery of energy substrates in register with neuronal activity. Astrocytes-a type of glial cell-have emerged as active players in brain energy delivery, production, utilization, and storage. Our understanding of neuroenergetics is rapidly evolving from a "neurocentric" view to a more integrated picture involving an intense cooperativity between astrocytes and neurons. This review focuses on the cellular aspects of brain energy metabolism, with a particular emphasis on the metabolic interactions between neurons and astrocytes.
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The aim of this study was to investigate the effects induced by an exposure to a GSM signal (Global System for Mobile Communication) on brain BOLD (blood-oxygen-level dependent) response, as well as its time course while performing a Go-NoGo task. Participants were tested twice, once in presence of a "real" exposure to GSM radiofrequency signal and once under a "sham" exposure (placebo condition). BOLD response of active brain areas and reaction times (RTs) while performing the task were measured both before and after the exposure. RTs to the somatosensory task did not change as a function of exposure (real vs sham) to GSM signal. BOLD results revealed significant activations in inferior parietal lobule, insula, precentral and postcentral gyri associated with Go responses after both ''real'' and ''sham'' exposure, whereas no significant effects were observed in the ROI analysis. The present fMRI study did not detect any brain activity changes by mobile phones. Also RTs in a somatosensory task resulted unaffected. No changes in BOLD response have been observed as a consequence of RF-EMFs exposure.
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For the last two decades, a large number of studies have investigated the effects of mobile phone radiation on the human brain and cognition using behavioral or neurophysiological measurements. This review evaluated previous findings with respect to study design and data analysis. Provocation studies found no evidence of subjective symptoms attributed to mobile phone radiation, suggesting psychological reasons for inducing such symptoms in hypersensitive people. Behavioral studies previously reported improved cognitive performance under exposure, but it was likely to have occurred by chance due to multiple comparisons. Recent behavioral studies and replication studies with more conservative statistics found no significant effects compared with original studies. Neurophysiological studies found no significant effects on cochlear and brainstem auditory processing, but only inconsistent results on spontaneous and evoked brain electrical activity. The inconsistent findings suggest possible false positives due to multiple comparisons and thus replication is needed. Other approaches such as brain hemodynamic response measurements are promising but the findings are few and not yet conclusive. Rigorous study design and data analysis considering multiple comparisons and effect size are required to reduce controversy in this important field of research.
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The dramatic increase in use of cellular telephones has generated concern about possible negative effects of radiofrequency signals delivered to the brain. However, whether acute cell phone exposure affects the human brain is unclear. To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. Randomized crossover study conducted between January 1 and December 31, 2009, at a single US laboratory among 47 healthy participants recruited from the community. Cell phones were placed on the left and right ears and positron emission tomography with ((18)F)fluorodeoxyglucose injection was used to measure brain glucose metabolism twice, once with the right cell phone activated (sound muted) for 50 minutes ("on" condition) and once with both cell phones deactivated ("off" condition). Statistical parametric mapping was used to compare metabolism between on and off conditions using paired t tests, and Pearson linear correlations were used to verify the association of metabolism and estimated amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phone. Clusters with at least 1000 voxels (volume >8 cm(3)) and P < .05 (corrected for multiple comparisons) were considered significant. Brain glucose metabolism computed as absolute metabolism (μmol/100 g per minute) and as normalized metabolism (region/whole brain). Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 μmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67-4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95, P < .001) and normalized metabolism (R = 0.89; P < .001). In healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the region closest to the antenna. This finding is of unknown clinical significance.
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Data acquired with functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) are often interpreted in terms of the underlying neuronal activity, despite mounting evidence that these signals do not always correlate with electrophysiological recordings. Therefore, considering the increasing popularity of functional neuroimaging, it is clear that a more comprehensive theory is needed to reconcile these apparent disparities and more accurately explain the mechanisms through which various PET and fMRI signals arise. In the present article, we have turned our attention to astrocytes, which vastly outnumber neurons and are known to serve a number of functions throughout the central nervous system (CNS). For example, astrocytes are known to be critically involved in neurotransmitter uptake and recycling, and empirical data suggests that brain activation increases both oxidative and glycolytic astrocyte metabolism. Furthermore, a number of recent studies imply that astrocytes are likely to play a key role in regulating cerebral blood delivery. Therefore, we propose that, by mediating neurometabolic and neurovascular processes throughout the CNS, astrocytes could provide a common physiological basis for fMRI and PET signals. Such a theory has significant implications for the interpretation of functional neuroimaging signals, because astrocytic changes reflect subthreshold neuronal activity, simultaneous excitatory/inhibitory synaptic inputs, and other transient metabolic demands that may not elicit electrophysiological changes. It also suggests that fMRI and PET signals may have inherently less sensitivity to decreases in synaptic input (i.e. 'negative activity') and/or inhibitory (GABAergic) neurotransmission.
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Although there exist some reference and stereotactic anatomical human brain atlases, there is no equivalent cerebrovascular atlas. A 3D reference atlas of the human cerebrovasculature that is interactive, stereotactic, very detailed, completely parcellated, fully labeled, extendable, dissectible, deformable, and user friendly, is needed in education, training, research, and clinical applications. We constructed a sophisticated and very detailed cerebrovascular atlas with 1325 vascular segments, the smallest of 80 μm in diameter. The atlas was created from multiple 3 and 7T scans by employing tools and methods developed in our lab. In contrast to a sort of "sampled" vascular geometry cited in the literature, we provide information about the "continuous" geometry of the vascular model measurable in 3D at every location and along any vascular segment for both hemispheres. This cerebrovascular atlas was validated taking into account domain knowledge from various fields including angiography, neurosurgery, neuroradiology, (clinical) neuroanatomy, and terminology. Validation was considered as a confirmation of the created vascular model to a typical (conventional) cerebrovascular system with nearly average dimensions. It was done in terms of vessel subdivision, origin, course, surrounding anatomy, patterns, length, diameter, and branches. This validation demonstrates that the constructed cerebrovascular model generally represents a normal, typical cerebrovasculature with its dimensions close to average. This 7T atlas along with the vascular model is a rich source of knowledge about the human cerebrovasculature. The atlas is applicable in education, research, and clinical applications; it has already been applied in deep brain stimulation.
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Recently, a great deal of interest has arisen in resting state fMRI as a measure of tonic brain function in clinical populations. Most studies have focused on the examination of temporal correlation between resting state fMRI low-frequency oscillations (LFOs). Studies on the amplitudes of these low-frequency oscillations are rarely reported. Here, we used amplitude of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF; the relative amplitude that resides in the low frequencies) to examine the amplitude of LFO in schizophrenia. Twenty-six healthy controls and 29 patients with schizophrenia or schizoaffective disorder participated. Our findings show that patients showed reduced low-frequency amplitude in proportion to the total frequency band investigated (i.e., fALFF) in the lingual gyrus, left cuneus, left insula/superior temporal gyrus, and right caudate and increased fALFF in the medial prefrontal cortex and the right parahippocampal gyrus. ALFF was reduced in patients in the lingual gyrus, cuneus, and precuneus and increased in the left parahippocampal gyrus. These results suggest LFO abnormalities in schizophrenia. The implication of these abnormalities for schizophrenic symptomatology is further discussed.
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The human brain is a complex dynamic system capable of generating a multitude of oscillatory waves in support of brain function. Using fMRI, we examined the amplitude of spontaneous low-frequency oscillations (LFO) observed in the human resting brain and the test-retest reliability of relevant amplitude measures. We confirmed prior reports that gray matter exhibits higher LFO amplitude than white matter. Within gray matter, the largest amplitudes appeared along mid-brain structures associated with the "default-mode" network. Additionally, we found that high-amplitude LFO activity in specific brain regions was reliable across time. Furthermore, parcellation-based results revealed significant and highly reliable ranking orders of LFO amplitudes among anatomical parcellation units. Detailed examination of individual low frequency bands showed distinct spatial profiles. Intriguingly, LFO amplitudes in the slow-4 (0.027-0.073 Hz) band, as defined by Buzsáki et al., were most robust in the basal ganglia, as has been found in spontaneous electrophysiological recordings in the awake rat. These results suggest that amplitude measures of LFO can contribute to further between-group characterization of existing and future "resting-state" fMRI datasets.
Electrical stimulation studies have demonstrated that a "supplementary motor area" (SMA) exists in humans. However, its precise functional organization has not been well defined. We reviewed the extraoperative electrical stimulation studies of 15 patients with intractable epilepsy who were evaluated with chronically implanted interhemispheric subdural electrodes. SMA-type positive motor responses were elicited not only from the mesial portion of the superior frontal gyrus but also from its dorsal convexity, and from the paracentral lobule, cingulate gyrus, and precuneus. Sensory symptoms, that could not be attributed to stimulation of the primary sensory area, were elicited from the superior frontal and cingulate gyri in addition to the precuneus. Therefore, human SMA, as defined by electrical stimulation, is not always confined to the mesial portion of the superior frontal gyrus as described previously. It is also not strictly "motor" but "sensorimotor" in representation. We propose referring to this region as the "supplementary sensorimotor area" (SSMA). We observed a somatotopic organization within the SSMA with an order of lower extremity, upper extremity, and head from posterior to anterior. Sensory representation in an individual was either anterior or posterior to the positive motor representation but never both. There was a supplementary eye field within the head representation. A supplementary negative motor area was noted at the anterior aspect of the SSMA. No language area was demonstrated within the SSMA. The physiologic significance of the SSMA and functional consequences of its resection must be addressed in further studies.
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The interpretation of functional brain images is often hampered by the presence of noise. This problem is most commonly solved by using a statistical method and only considering signals that are unlikely to occur by chance. The method used should be specific and sensitive, specific because only true signals are of interest and sensitive because this will enable more information to be extracted from each experiment. Here we present a modification of the cluster analysis proposed by Roland et al. (Human Brain Mapping 1: 3-19, 1993). A covariance model is used to test hypotheses for each voxel. The generated statistical images are searched for the largest clusters. From the same data set noise images are generated. For each of these noise images the autocorrelation function is estimated. These estimates are subsequently used to generate simulated noise images, from which a distribution of cluster sizes is derived. The derived distribution is used to estimate probabilities for the clusters detected in the statistical images generated by testing the hypothesis. This presented method is shown to be specific and is further compared with SPM96 and the nonparametric method of Holmes et al. (J. Cereb. Blood Flow Metab. 16: 7-22, 1996).
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The aim of this work was to investigate the dependence of BOLD responses on different patterns of stimulus input/neuronal changes. In an earlier report, we described an input-state-output model that combined (i) the Balloon/Windkessel model of nonlinear coupling between rCBF and BOLD signals, and (ii) a linear model of how regional flow changes with synaptic activity. In the present investigation, the input-state-output model was used to explore the dependence of simulated PET (rCBF) and fMRI (BOLD) signals on various parameters pertaining to experimental design. Biophysical simulations were used to estimate rCBF and BOLD responses as functions of (a) a prior stimulus, (b) epoch length (for a fixed SOA), (c) SOA (for a fixed number of events), and (d) stimulus amplitude. We also addressed the notion that a single neuronal response may differ, in terms of the relative contributions of early and late neural components, and investigated the effect of (e) the relative size of the late or "endogenous" neural component. We were interested in the estimated average rCBF and BOLD responses per stimulus or event, not in the statistical efficiency with which these responses are detected. The BOLD response was underestimated relative to rCBF with a preceding stimulus, increasing epoch length, and increasing SOA. Furthermore, the BOLD response showed some highly nonlinear behaviour when varying stimulus amplitude, suggesting some form of hemodynamic "rectification." Finally, the BOLD response was underestimated in the context of large late neuronal components. The difference between rCBF and BOLD is attributed to the nonlinear transduction of rCBF to BOLD signal. Our simulations support the idea that varying parameters that specify the experimental design may have differential effects in PET and fMRI. Moreover, they show that fMRI can be asymmetric in its ability to detect deactivations relative to activations when an absolute baseline is stipulated. Finally, our simulations suggest that relative insensitivity to BOLD signal in specific regions, such as the temporal lobe, may be partly explained by higher cognitive functions eliciting a relatively large late endogenous neuronal component.
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Functional connectivity among brain regions has been investigated via an analysis of correlations between regional signal fluctuations recorded in magnetic resonance (MR) images obtained in a steady state. In comparison with studies of functional connectivity that utilize task manipulations, the analysis of correlations in steady state data is less susceptible to confounds arising when functionally unrelated brain regions respond in similar ways to changes in task. A new approach to identifying interregional correlations in steady state data makes use of two independent data sets. Regions of interest (ROIs) are defined and hypotheses regarding their connectivity are generated in one data set. The connectivity hypotheses are then evaluated in the remaining (independent) data set by analyzing low frequency temporal correlations between regions. The roles of the two data sets are then reversed and the process repeated, perhaps multiple times. This method was illustrated by application to the language system. The existence of a functional connection between Broca's area and Wernicke's area was confirmed in healthy subjects at rest. An increase in this functional connection when the language system was actively engaged (when subjects were continuously listening to narrative text) was also confirmed. In a second iteration of analyses, a correlation between Broca's area and a region in left premotor cortex was found to be significant at rest and to increase during continuous listening. These findings suggest that the proposed methodology can reveal the presence and strength of functional connections in high-level cognitive systems.
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Mobile phones (MP) are used extensively and yet little is known about the effects they may have on human physiology. There have been conflicting reports regarding the relation between MP use and the electroencephalogram (EEG). The present study suggests that this conflict may be due to methodological differences such as exposure durations, and tests whether exposure to an active MP affects EEG as a function of time. Twenty-four subjects participated in a single-blind fully counterbalanced cross-over design, where both resting EEG and phase-locked neural responses to auditory stimuli were measured while a MP was either operating or turned off. MP exposure altered resting EEG, decreasing 1-4 Hz activity (right hemisphere sites), and increasing 8-12 Hz activity as a function of exposure duration (midline posterior sites). MP exposure also altered early phase-locked neural responses, attenuating the normal response decrement over time in the 4-8 Hz band, decreasing the response in the 1230 Hz band globally and as a function of time, and increasing midline frontal and lateral posterior responses in the 30-45 Hz band. Active MPs affect neural function in humans and do so as a function of exposure duration. The temporal nature of this effect may contribute to the lack of consistent results reported in the literature.
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Functional imaging studies have shown that certain brain regions, including posterior cingulate cortex (PCC) and ventral anterior cingulate cortex (vACC), consistently show greater activity during resting states than during cognitive tasks. This finding led to the hypothesis that these regions constitute a network supporting a default mode of brain function. In this study, we investigate three questions pertaining to this hypothesis: Does such a resting-state network exist in the human brain? Is it modulated during simple sensory processing? How is it modulated during cognitive processing? To address these questions, we defined PCC and vACC regions that showed decreased activity during a cognitive (working memory) task, then examined their functional connectivity during rest. PCC was strongly coupled with vACC and several other brain regions implicated in the default mode network. Next, we examined the functional connectivity of PCC and vACC during a visual processing task and show that the resultant connectivity maps are virtually identical to those obtained during rest. Last, we defined three lateral prefrontal regions showing increased activity during the cognitive task and examined their resting-state connectivity. We report significant inverse correlations among all three lateral prefrontal regions and PCC, suggesting a mechanism for attenuation of default mode network activity during cognitive processing. This study constitutes, to our knowledge, the first resting-state connectivity analysis of the default mode and provides the most compelling evidence to date for the existence of a cohesive default mode network. Our findings also provide insight into how this network is modulated by task demands and what functions it might subserve.
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Fourteen healthy right-handed subjects were scanned using PET with a [15O]water tracer during exposure to electromagnetic field (EMF) emitted by a mobile phone and a sham-exposure under double-blind conditions. During scanning, the subjects performed a visual working memory task. Exposure to an active mobile phone produced a relative decrease in regional cerebral blood flow (rCBF) bilaterally in the auditory cortex but no rCBF changes were observed in the area of maximum EMF. It is possible that these remote findings were caused by the EMF emitted by the active mobile phone. A more likely interpretation of the present findings were a result of an auditory signal from the active mobile phone. Therefore, it is not reasoned to attribute this finding to the EMF emitted by the phone. Further study on human rCBF during exposure to EMF of a mobile phone is needed.
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A probabilistic framework is presented that enables image registration, tissue classification, and bias correction to be combined within the same generative model. A derivation of a log-likelihood objective function for the unified model is provided. The model is based on a mixture of Gaussians and is extended to incorporate a smooth intensity variation and nonlinear registration with tissue probability maps. A strategy for optimising the model parameters is described, along with the requisite partial derivatives of the objective function.
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We recorded the resting electroencephalogram of 20 healthy subjects in order to investigate the effect of electromagnetic field (EMF) exposure on EEG waking activity and its temporal development. The subjects were randomly assigned to two groups and exposed, in double-blind conditions, to a typical mobile phone signal (902.40 MHz, modulated at 217 Hz, with an average power of 0.25 W) before or during the EEG recording session. The results show that, under real exposure as compared to baseline and sham conditions, EEG spectral power was influenced in some bins of the alpha band. This effect was greater when the EMF was on during the EEG recording session than before it. The present data lend further support to the idea that pulsed high-frequency electromagnetic fields can affect normal brain functioning, also if no conclusions can be drawn about the possible health effects.
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In children with attention deficit hyperactivity disorder (ADHD), functional neuroimaging studies have revealed abnormalities in various brain regions, including prefrontal-striatal circuit, cerebellum, and brainstem. In the current study, we used a new marker of functional magnetic resonance imaging (fMRI), amplitude of low-frequency (0.01-0.08Hz) fluctuation (ALFF) to investigate the baseline brain function of this disorder. Thirteen boys with ADHD (13.0+/-1.4 years) were examined by resting-state fMRI and compared with age-matched controls. As a result, we found that patients with ADHD had decreased ALFF in the right inferior frontal cortex, [corrected] and bilateral cerebellum and the vermis as well as increased ALFF in the right anterior cingulated cortex, left sensorimotor cortex, and bilateral brainstem. This resting-state fMRI study suggests that the changed spontaneous neuronal activity of these regions may be implicated in the underlying pathophysiology in children with ADHD.
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We measured maximum temperature rises on the side of the face after 6 min of continuous mobile phone operation using two models of AMPS analog phones operating in the 835 MHz band and three early model GSM digital phones operating in the 900 MHz band. For the GSM phones the highest recorded temperature rise difference was 2.3 degrees C and for the AMPS phones it was 4.5 degrees C, both at locations on the cheek. The higher differential temperature rise between AMPS and GSM may reflect the higher maximum average operating power of AMPS (600 mW) versus GSM900 (250 mW). Additionally, we compared temperature changes at a consistent location on the cheek for an AMPS phone that was inoperative (-0.7 degrees C), transmitting at full power (+2.6 degrees C) and in stand-by mode (+2.0 degrees C). Our results suggest that direct RF heating of the skin only contributes a small part of the temperature rise and that most is due to heat conduction from the handset.
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Recent functional imaging studies have indicated that the pathophysiology of Alzheimer's disease (AD) can be associated with the changes in spontaneous low-frequency (<0.08 Hz) blood oxygenation level-dependent fluctuations (LFBF) measured during a resting state. The purpose of this study was to examine regional LFBF coherence patterns in early AD and the impact of regional brain atrophy on the functional results. Both structural MRI and resting-state functional MRI scans were collected from 14 AD subjects and 14 age-matched normal controls. We found significant regional coherence decreases in the posterior cingulate cortex/precuneus (PCC/PCu) in the AD patients when compared with the normal controls. Moreover, the decrease in the PCC/PCu coherence was correlated with the disease progression measured by the Mini-Mental State Exam scores. The changes in LFBF in the PCC/PCu may be related to the resting hypometabolism in this region commonly detected in previous positron emission tomography studies of early AD. When the regional PCC/PCu atrophy was controlled, these results still remained significant but with a decrease in the statistical power, suggesting that the LFBF results are at least partly explained by the regional atrophy. In addition, we also found increased LFBF coherence in the bilateral cuneus, right lingual gyrus and left fusiform gyrus in the AD patients. These regions are consistent with previous findings of AD-related increased activation during cognitive tasks explained in terms of a compensatory-recruitment hypothesis. Finally, our study indicated that regional brain atrophy could be an important consideration in functional imaging studies of neurodegenerative diseases.
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We tested the working hypothesis that electromagnetic fields from mobile phones (EMFs) affect interhemispheric synchronization of cerebral rhythms, an important physiological feature of information transfer into the brain. Ten subjects underwent two electroencephalographic (EEG) recordings, separated by 1 week, following a crossover double-blind paradigm in which they were exposed to a mobile phone signal (global system for mobile communications; GSM). The mobile phone was held on the left side of the subject head by a modified helmet, and orientated in the normal position for use over the ear. The microphone was orientated towards the corner of the mouth, and the antenna was near the head in the parietotemporal area. In addition, we positioned another similar phone (but without battery) on the right side of the helm