Abstract— 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.
I. INTRODUCTION
During the past few years, many neurophysiological and
neuroimage studies have been applied to investigate whether
radio frequency electromagnetic fields (EMF) produced by
mobile phone have an influence on human brain [1].
Compared with other tools, Electroencephalography (EEG)
has better compatibility with the exposure system and
therefore becomes the most widely used approach in this area
[1]. During these studies, EMF exposure environment was
setup by the real mobile phone or other experimental device.
EEG signals were then recorded to characterize the brain
activities and used to evaluate the possible modulation caused
by EMF exposure.
From the perspective of EEG data analysis, most previous
studies divided EEG signals into different frequency bands
and compared their power spectrum among different exposure
conditions. For example, resting EEG studies have
consistently reported Global System for Mobile
Communications (GSM) EMF exposure enhanced the alpha
activity in midline posterior sites [2] and other brain regions [3,
4]. It is well known that human brain is a complex
organization which simultaneously satisfies two basic
principles, that is, functional segregation of specialized neural
This work was supported by National Key Basic Research Project (Grant
No. 2011CB503705) and National Natural Science Foundation of China
(Grant No. 61201066 and 61371187).
Bin Lv, Chang Su, Lei Yang, Yi Xie and Tongning Wu are with the China
Academy of Telecommunication Research of Ministry of Industry and
Information Technology, Beijing, China. (corresponding authors: Bin Lv and
Tongning Wu. address: No. 52, Huayuanbei Road, Haidian District, Beijing,
100191, China; phone: +86-10-62304633-2084; e-mail: lvbin@catr.cn,
wutongning@catr.cn)
information processing in distinct brain regions and functional
integration of some regions into networks [5]. Thus, it is
necessary to investigate whether EMF exposure would
modulate the functional connectivity among different brain
regions. Vecchio et al used event-related coherence (ERCoh)
method to estimate the coherence variation of homotopic EEG
channels among different exposure conditions, and found that
GSM EMF from mobile phone affected the interhemispheric
synchronization of temporal and frontal resting EEG rhythms
in normal young [6] and elderly subjects [7]. However, till
now, no study investigated the EMF influence on functional
connectivity across the whole brain.
Besides coherence analysis, there have been lots of
measures to characterize EEG synchronization based on
different underlying assumptions. They can be categorized
into bivariate or multivariate, linear or nonlinear, model based
or data-driven, and so on (see more discussion in [8, 9]).
Among them, synchronization likelihood was proposed based
on the detection of simultaneously occurring patterns along
the neural signals [10]. It is a robust multivariate nonlinear
estimator which has be widely used to estimate the pattern of
statistical interdependencies between two or more EEG
signals during cognitive task [11] and the possible alternation
in patients with some brain diseases [12].
In this paper, we present our recent work about EMF effect
on brain functional connectivity with synchronization
likelihood method. We designed a controllable Long Term
Evolution (LTE) EMF exposure environment at 2.573 GHz,
and recruited ten healthy subjects to participate in the
exposure experiment. EEG signals were recorded in different
exposure conditions. Synchronization likelihood was used to
identify the functional coupling between each pair of EEG
channels. In the end, we performed statistical analysis to
evaluate whether the whole brain patterns of synchronization
likelihood were modulated by the acute LTE-related EMF
exposure.
II. METHODS
A. Experiment Setup
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). For
each subject, there were two sessions including real exposure
(power on) and sham exposure (power off). Both sessions
Whole Brain EEG Synchronization Likelihood Modulated by Long
Term Evolution Electromagnetic Fields Exposure
Bin Lv, IEEE Member, Chang Su, Lei Yang, Yi Xie, and Tongning Wu, IEEE Member
978-1-4244-7929-0/14/$26.00 ©2014 IEEE 986