Mobile phone effects on children's event-related oscillatory EEG during an auditory memory task

Purpose: To assess the effects of electromagnetic fields (EMF) emitted by mobile phones (MP) on the 1 – 20 Hz event-related brain oscillatory EEG (electroencephalogram) responses in children performing an auditory memory task (encoding and recognition).

Materials and methods: EEG data were gathered while 15 subjects (age 10 – 14 years) performed an auditory memory task both with and without exposure to a digital 902 MHz MP in counterbalanced order.

Results: During memory encoding, the active MP modulated the event-related desynchronization/synchronization (ERD/ERS) responses in the ～4 – 8 Hz EEG frequencies. During recognition, the active MP transformed these brain oscillatory responses in the ～4 – 8 Hz and ～15 Hz frequencies.

Conclusions: The current findings suggest that EMF emitted by mobile phones has effects on brain oscillatory responses during cognitive processing in children.     

Effects of electromagnetic fields emitted by cellular phones on the electroencephalogram during a visual working memory task

PURPOSE: To examine the effects of electromagnetic fields (EMF) emitted by cellular phones on the event-related desynchronization/synchronization (ERD/ERS) responses of the 4-6, 6-8, 8-10 and 10-12Hz EEG frequency bands during cognitive processing. MATERIALS AND METHODS: Twenty-four subjects performed a visual sequential letter task (n-back task) with three different working memory load conditions: zero, one and two items. All subjects performed the memory task both with and without exposure to a digital 902 MHz EMF in counterbalanced order. RESULTS: The presence of EMF altered the ERD/ERS responses in the 6-8 and 8-10 Hz frequency bands but only when examined as a function of memory load and depending also on whether the presented stimulus was a target or not. CONCLUSIONS: The results suggest that the exposure to EMF modulates the responses of EEG oscillatory activity approximately 8 Hz specifically during cognitive processes.     

Effects of electromagnetic fields emitted by cellular phones on the electroencephalogram during a visual working memory task

Purpose : To examine the effects of electromagnetic fields (EMF) emitted by cellular phones on the event-related desynchronization/synchronization (ERD/ERS) responses of the 4-6, 6-8, 8-10 and 10-12 Hz EEG frequency bands during cognitive processing. Materials and methods : Twenty-four subjects performed a visual sequential letter task (n -back task) with three different working memory load conditions: zero, one and two items. All subjects performed the memory task both with and without exposure to a digital 902MHz EMF in counterbalanced order. Results : The presence of EMF altered the ERD/ERS responses in the 6-8 and 8-10Hz frequency bands but only when examined as a function of memory load and depending also on whether the presented stimulus was a target or not. Conclusions : The results suggest that the exposure to EMF modulates the responses of EEG oscillatory activity ~8Hz specifically during cognitive processes.     

视觉记忆负荷对EEG的事件相关同步化与事件相关去同步化的影响

目的：研究视觉空间记忆和抽象几何图形记忆的工作记忆负荷对脑电事件相关同步化和去同步化的影响。方法：采用n-back范式，取n分别等于1、2、3为3种负荷水平下完成视觉空间匹配和抽象几何图形匹配两类记忆任务，并记录其脑电。结果：theta波的ERS总是伴随着alpha波的ERD出现。随着任务难度的增大，6-8Hz的theta波的ERS下降，alpha波的ERD增大，图形匹配任务引出的thetaERS和alphaERD均大于空间位置匹配任务。任务难度和任务类型的效应大多出现在CZ和FZ电极，这与任务所包含的注意和记忆的加工主要激活额叶和顶叶皮层的观点相符合。结论：EEG的ERD（或ERS）随视觉记忆负荷变化，因此可作为反映视觉记忆负荷的有效指标。     

靶音识别作业对脑波α段频率涨落特征的影响

目的 研究靶音识别作业对脑波α段频率涨落特征的影响及各优势成分的作业相关变化。方法被试为21名右利手、听力及EEG正常男性(25—35岁),记录被试闭眼状态下安静及靶音识别作业过程中的12导EEG信号,利用脑波频率涨落分析技术分析8、9、10、11、12、13Hz 6个频率成分的优势涨落特征。结果 靶音识别作业导致脑波α段频率涨落竞争结构中的主涨落成分向高频方向发展．9-10Hz优势显著下降,11—13Hz优势显著增加,各频率成分在频率竞争结构中的地位和相互作用改变：同时。作业相关的优势成分快化与各被试静态EEG有关,即围绕静态EEG功谱峰值频率,较高频率成分优势几率明显增加,较低频率成分优势几率则明显减少。结论 靶音识别作业导致脑波α段频率涨落特征的显著改变可能反映了与作业负荷有关的脑一般机能状态的增强,因此脑波α段频率涨落分析技术可能有助于作业负荷的总体及个别评价。     

Neuroprotective effects of melatonin and omega-3 on hippocampal cells prenatally exposed to 900 MHz electromagnetic fields

Purpose: Adverse effects on human health caused by electromagnetic fields (EMF) associated with the use of mobile phones, particularly among young people, are increasing all the time. The potential deleterious effects of EMF exposure resulting from mobile phones being used in close proximity to the brain require particular evaluation. However, only a limited number of studies have investigated the effects of prenatal exposure to EMF in the development of the pyramidal cells using melatonin (MEL) and omega-3 (ω-3).

Materials and methods: We established seven groups of pregnant rats consisting of three animals each; control (CONT), SHAM, EMF, EMF?+?MEL, MEL, EMF?+?ω-3 and ω-3 alone. The rats in the EMF, EMF?+?MEL, EMF?+?ω-3 groups were exposed to 900?MHz EMF for 60?min/day in an exposure tube during the gestation period. The CONT, MEL and ω-3 group rats were not placed inside the exposure tube or exposed to EMF during the study period. After delivery, only spontaneously delivered male rat pups were selected for the establishment of further groups. Each group of offspring consisted of six animals. The optical fractionator technique was used to determine total pyramidal neuron numbers in the rat hippocampal region.

Results: The total number of pyramidal cells in the cornu ammonis (CA) in the EMF group was significantly lower than in the CONT, SHAM, EMF?+?MEL, and EMF?+?ω-3 groups. No significant difference was observed between the EMF, MEL and ω-3 groups. No difference was also observed between any groups in terms of rats’ body or brain weights.

Conclusion: MEL and ω-3 can protect the cell against neuronal damage in the hippocampus induced by 900?MHz EMF. However, further studies are now needed to evaluate the chronic effects of 900?MHz EMF on the brain in the prenatal period.     

利用fMRI研究衰老对听觉数字工作记忆的影响

目的:利用功能磁共振研究衰老对数字工作记忆的影响.材料和方法:6个青年和3个老年被试者参加了有关正序和反序记忆阿拉伯数字的工作记忆实验,同时,fMRI被用来记录大脑的反应.结果:①在青年组中,编码阶段,反序记忆左侧BA9-46区激活高于正序记忆;提取阶段,反序记忆在双侧BA7区激活点体积高于正序记忆.②老年组与青年组比较,在编码阶段反序记忆中青年组左侧BA 9-46区激活高于老年组.结论:功能磁共振有助于加深对衰老的理解.     

Functional MRI of human auditory cortex using block and event-related designs.

fMRI of human auditory cortex response to sinusoidal tones of 200, 1000, and 3000 Hz was evaluated using block design and conventional and "silent" event-related designs. Conventional event-related fMRI revealed the timecourse of the BOLD response (approximately 5 sec to peak, approximately 4 sec full-width-half-max, and approximately 14 sec recovery to baseline). Both event-related, but not block, designs provided evidence for tonotopic organization in auditory cortex. Sources of low-frequency activation were more lateral and anterior than the sources of high-frequency activation (P < or = 0.05). In the block designs, repeated rapid stimulus presentation and the co-incidence of scanner noise preclude definition of tonotopic organization revealed in event-related approaches. Magn Reson Med 45:254-260, 2001.     

5Hz和20Hz磁场对脑反应影响的比较研究

基于在脑电频率范围内的磁场刺激对脑过程可能有调制作用的假设，并在已取得 结构的基础上，本文在２２名正常被试者中比较了５Ｈｚ和２０Ｈｚ的磁场刺激对进行选择反应和选择心算时脑反应的影响。     

视觉作业负荷下脑波频率涨落特征的变化特点

目的考察静态和视觉作业负荷下的脑波α段频率涨落特征、以及视觉作业相关的变化特点。方法记录19名青年男性静态(闭眼及睁眼)和执行视觉作业过程中的EEG，应用脑波频率涨落分析技术分析状态相关的α段频率涨落特征及变化特点。结果由闭眼、睁眼至视觉作业状态，α段频率涨落优势概率分布特征显著改变，9Hz、10Hz优势下降，8Hz、11～13Hz优势上升，具有绝对优势的主涨落成分逐渐为多成分竞争所代替，前部脑区较慢成分逐渐居于优势；各脑区α段优势涨落熵值显著增加，优势涨落能量逐渐显著降低，且其增加／下降过程均具有明显的脑区性。结论脑波α段频率涨落特征指标的变化反映了视觉作业下相关脑区活动的进一步增强，表明该技术可应用于视觉作业负荷的研究。     

等概率听觉选择反应中非靶ERPs的N2效应

目的研究等概率听觉选择反应任务中非靶ERPs的N2效应是否存在及其特点。方法被试者为1 6名右利手健康男性青年 ( 2 3 .2± 2 .1岁 )。刺激为听觉输入的一位数字信号序列 ( 2～ 7) ,要求被试者对靶数字进行拨开关反应 ,对非靶数字不作反应。记录 9导脑电。结果 1 )非靶ERPs产生了明显的N2 80 (N2效应 ) ,额区最为突出 ;2 )非靶ERPs中P3的潜伏期明显长于、峰值显著小于靶ERPs,且头皮分布比靶ERPs(顶区优势 )更趋于中央脑区分布。结论听觉通道亦存在非靶N2效应 ,且不能简单理解为是对靶刺激反应的抑制 ,而更可能反映了工作记忆中模式的重调过程 ,而这一过程的完成可能比靶数字出现时的反应更为复杂 ,且主要发生在额区     

Effect of 7, 14 and 21 Hz modulated 450 MHz microwave radiation on human electroencephalographic rhythms

PURPOSE: The aim of this study was to evaluate the effect of microwaves modulated at different frequencies on human electroencephalographic (EEG) rhythms. MATERIALS AND METHODS: Thirteen healthy volunteers were exposed to microwaves (450 MHz) pulse-modulated at frequencies of 7, 14 and 21 Hz. The field power density at the scalp was 0.16 mW/cm2. Our experimental protocol consisted of two five-cycle (1 min on and 1 min off) series of exposures at fixed modulation frequencies. A relative change in the EEG power with and without exposure was used as a quantitative measure. EEG frequencies recorded in the theta (4-6.8 Hz), alpha (8-13 Hz), betal (15-20 Hz), and beta2 (22-38 Hz) bands were analyzed. RESULTS: Modulated microwaves caused an increase in the average EEG alpha (17%) and beta (7%) power but the theta rhythm remained unaffected. Increases in the EEG alpha and beta power were statistically significant during the first half-period of the exposure interval (30 s) at the modulation frequencies of 14 and 21 Hz. Differences were found in individual sensitivity to exposure. Increases in the EEG beta power appeared statistically significant in the case of four subjects. CONCLUSIONS: Our findings suggest that the effect of the 450 MHz microwave radiation modulated at 7, 14 and 21 Hz varies depending on the modulation frequency. The microwave exposure modulated at 14 and 21 Hz enhanced the EEG power in the alpha and beta frequency bands, whereas no enhancement occurred during exposure to the modulation frequency of 7 Hz.     

EEG correlates of G-induced loss of consciousness

INTRODUCTION: Electroencephalographic (EEG) correlates of Gz-induced loss of consciousness (G-LOC) were examined to better understand the mechanisms of G-LOC. METHODS: There were 10 subjects (4 women) who provided 35 G-LOC episodes during which 13 channels of EEG and eye activity were recorded. Subjects simultaneously performed tracking and mathematical tasks prior to and following G-LOC. The performance data and cerebral regional oxygen saturation (rSO2), as measured using near infrared spectroscopy, were correlated with the EEG changes. RESULTS: Across all subjects, seven EEG events were identified and measured. The two most significant were found over widespread scalp sites. They were a 1-2 Hz waveform just prior to G-LOC and a very large, approximately 1 Hz waveform just prior to regaining consciousness. These were associated with a drop of rSO2 levels to approximately 90% of the pre-G-LOC baseline levels. rSO2 levels returned to pre-G-LOC levels within approximately 15 s following G-LOC while EEG and performance measures took approximately 60 s. DISCUSSION: There were two unique EEG waveforms found, one preceding unconsciousness and the other preceding the return to consciousness during G-LOC episodes. Further, the supply of oxygen to the brain was rapidly restored, within approximately 15 s, while the EEG and performance data showed that approximately 60 s were required for the brain to regain functional integrity. The delay in performance and EEG recovery following G-LOC demonstrates that the recovery of brain activity to support cognitive function requires more than just the restoration of normal oxygen levels.     

听觉事件相关电位(ERPs)早期和晚期成份的任务负荷效应

目的 比较不同任务负荷的听觉事件相关电位（ERPs,event-related potentials)，以探讨听觉ERPs各种成份的任务负荷效应。方法 被试者为12名右利手正常在校大学生（20－23岁）。要求被试者对4个方位的声音信号进行难度负荷不同的3种作业任务：全反应（AR）、方位区分反应（DR）、音调选择方位式区分反应（SR）。对－t和方差分析统计3种任务的听觉ERPs成份。结果1）SR反应时最长，DR次之，AR最短；2）早期成份的任务负荷效应：P1波幅随负荷的增加进行性增强；AR－ERPs的NI峰值相近，均高于SR（T）－ERPs；DR－ERPs与SR（T）－ERPs中前脑区的P2波幅无明显差异，均显著低于AR－ERPs，P2的潜伏期随负荷的增加明显缩短；3）晚期成分的任务负荷效应；随任务负荷的增加，N2（N2a/N2b),P3和SW波幅明显增强。结论 听觉ERPs早期成份和晚期成份均有明显的任务负荷效应，晚期成份的任务负荷效应可能与早期的警觉激活程度相关联。     

Frequencies contributing to functional connectivity in the cerebral cortex in "resting-state" data

BACKGROUND AND PURPOSE: In subjects performing no specific cognitive task ("resting state"), time courses of voxels within functionally connected regions of the brain have high cross-correlation coefficients ("functional connectivity"). The purpose of this study was to measure the contributions of low frequencies and physiological noise to cross-correlation maps. METHODS: In four healthy volunteers, task-activation functional MR imaging and resting-state data were acquired. We obtained four contiguous slice locations in the "resting state" with a high sampling rate. Regions of interest consisting of four contiguous voxels were selected. The correlation coefficient for the averaged time course and every other voxel in the four slices was calculated and separated into its component frequency contributions. We calculated the relative amounts of the spectrum that were in the low-frequency (0 to 0.1 Hz), the respiratory-frequency (0.1 to 0.5 Hz), and cardiac-frequency range (0.6 to 1.2 Hz). RESULTS: For each volunteer, resting-state maps that resembled task-activation maps were obtained. For the auditory and visual cortices, the correlation coefficient depended almost exclusively on low frequencies (<0.1 Hz). For all cortical regions studied, low-frequency fluctuations contributed more than 90% of the correlation coefficient. Physiological (respiratory and cardiac) noise sources contributed less than 10% to any functional connectivity MR imaging map. In blood vessels and cerebrospinal fluid, physiological noise contributed more to the correlation coefficient. CONCLUSION: Functional connectivity in the auditory, visual, and sensorimotor cortices is characterized predominantly by frequencies slower than those in the cardiac and respiratory cycles. In functionally connected regions, these low frequencies are characterized by a high degree of temporal coherence.     

Functional MR imaging in Alzheimer's disease during memory encoding

BACKGROUND AND PURPOSE: We applied functional MR imaging with a learning task in healthy elderly volunteers and in patients with Alzheimer's disease to study brain activation during memory performance. The purpose was to determine the feasibility of functional MR imaging during a learning task in healthy elderly volunteers and in patients with Alzheimer's disease and to test our hypothesis that brain activation is decreased in the medial temporal lobe (MTL) memory system in patients with Alzheimer's disease compared with control volunteers. METHODS: In 12 patients with mild to moderate forms of Alzheimer's disease and 10 elderly control volunteers, activation of the MTL memory system was studied. We used two learning tasks that required the encoding of new information into memory. After the functional MR imaging experiment, participants were tested for recognition of the encoded objects. RESULTS: In the elderly control volunteers, activation during memory encoding was observed in medial and lateral temporal lobe structures (fusiform, parietal and occipital parts, and hippocampal formation) and in the frontal cortex, as reported previously in studies of young control volunteers. Focusing on the MTL, we observed that activation was significantly decreased in patients with Alzheimer's disease compared with control volunteers in the left hippocampus and parahippocampal gyrus bilaterally during the first encoding task but not during the second (P < .05, uncorrected). CONCLUSION: Functional MR imaging with a learning task seems feasible in elderly volunteers and in patients with Alzheimer's disease. The measured functional signal decrease in MTL areas warrants further exploration of the (early) diagnostic usefulness of functional MR imaging in cases of Alzheimer's disease and other dementias.     

Brain activation in sedated children: auditory and visual functional MR imaging

PURPOSE: To map developing areas of activation with functional magnetic resonance (MR) imaging in sedated children by using passive auditory and visual tasks. MATERIALS AND METHODS: Forty children between 2 months and 9 years old were examined and grouped according to age. Children were selected from patients referred to undergo brain MR imaging. Patients received pentobarbital (3.0-7.0 mg per kilogram of body weight) or chloral hydrate (50-75 mg/kg). The functional MR imaging study was performed at the end of the examination. Paradigms consisted of flashing lights at 8 Hz displayed on special goggles and a prerecorded mother's voice presented through headphones. Activation maps were obtained from a paired t test with a P value of.0005 (uncorrected). RESULTS: The visual stimulus produced statistically significant negative values in the rostral aspect of the primary visual area (28 [90%] of 31 patients). The auditory paradigm activated either temporal or frontal areas in 26 (68%) of 31 patients. There was more frontal activation in the older children. CONCLUSION: Visual and auditory cortices can be activated in children who have been sedated. Visual responses show negative values in the rostral visual cortex, independent of age. Auditory activation is seen in temporal and frontal lobes.     

Case-control study on the use of cellular and cordless phones and the risk for malignant brain tumours

Purpose : To investigate the use of cellular and cordless phones and the risk for malignant brain tumours. Materials and methods : A case-control study was performed on 649 patients aged 20-80 years of both sexes with malignant brain tumour diagnosed from 1 January 1997 to 30 June 2000. All patients were alive during the time of the study and had histopathology verified brain tumours. One matched control to each case was selected from the Swedish Population Register. The study area was the Uppsala-Örebro, Stockholm, Linköping and Göteborg medical regions of Sweden. Results : Exposure was assessed by a questionnaire answered by 588 (91%) cases and 581 (90%) controls. Phone usage was defined as 'ever use' and usage starting within 1 year before diagnosis was disregarded. Overall, no significantly increased risks were found: analogue cellular phones yielded an odds ratio (OR)= 1.13, 95% confidence interval (CI)= 0.82-1.57, digital cellular phones OR = 1.13, CI= 0.86-1.48, and cordless phones OR= 1.13, CI= 0.85-1.50. For ipsilateral (same side) radiofrequency exposure, analogue mobile phones gave OR= 1.85, CI= 1.16-2.96, for all malignant brain tumours. For astrocytoma, this risk was OR= 1.95, CI= 1.12-3.39. For all malignant brain tumours, digital mobile phones yielded OR= 1.59, CI = 1.05-2.41, and cordless phones yielded OR= 1.46, CI= 0.96-2.23, in the analysis of ipsilateral exposure. Conclusion : The ipsilateral use of an analogue cellular phone yielded a significantly increased risk for malignant brain tumours.     

Correlation between BOLD-fMRI and EEG signal changes in response to visual stimulus frequency in humans.

The correlation between signals acquired using electroencephalography (EEG) and fMRI was investigated in humans during visual stimulation. Evoked potential EEG and BOLD fMRI data were acquired independently under similar conditions from eight subjects during stimulation by a checkerboard flashed at frequencies ranging from 2-12 Hz. The results indicate highly correlated changes in the strength of the EEG signal averaged over two occipital electrodes and the BOLD signal within the occipital lobe as a function of flash frequency for 7/8 subjects (average linear correlation coefficient of 0.76). Both signals peaked at approximately 8 Hz. For one subject the correlation coefficient was 0.20; the EEG signal peaked at 6 Hz and the BOLD signal peaked at 10 Hz. Overall, the EEG and BOLD signals, each averaged over 40-sec stimulation periods, appear to be coupled linearly during visual stimulation by a flashing checkerboard.     

Case-control study on the use of cellular and cordless phones and the risk for malignant brain tumours

PURPOSE: To investigate the use of cellular and cordless phones and the risk for malignant brain tumours. MATERIALS AND METHODS: A case-control study was performed on 649 patients aged 20-80 years of both sexes with malignant brain tumour diagnosed from 1 January 1997 to 30 June 2000. All patients were alive during the time of the study and had histopathology verified brain tumours. One matched control to each case was selected from the Swedish Population Register. The study area was the Uppsala-Orebro, Stockholm, Link?ping and G?teborg medical regions of Sweden. RESULTS: Exposure was assessed by a questionnaire answered by 588 (91%) cases and 581 (90%) controls. Phone usage was defined as 'ever use' and usage starting within 1 year before diagnosis was disregarded. Overall, no significantly increased risks were found: analogue cellular phones yielded an odds ratio (OR)=1.13, 95% confidence interval (CI)=0.82-1.57, digital cellular phones OR=1.13, CI=0.86-1.48, and cordless phones OR=1.13, CI=0.85-1.50. For ipsilateral (same side) radiofrequency exposure, analogue mobile phones gave OR=1.85, CI=1.16-2.96, for all malignant brain tumours. For astrocytoma, this risk was OR=1.95, CI=1.12-3.39. For all malignant brain tumours, digital mobile phones yielded OR=1.59, CI=1.05-2.41, and cordless phones yielded OR=1.46, CI=0.96-2.23, in the analysis of ipsilateral exposure. CONCLUSION: The ipsilateral use of an analogue cellular phone yielded a significantly increased risk for malignant brain tumours.