The influence of GSM phone on electroencephalogram
is still at the stage of study [1-3]. Significantly, it is caused
by difficulties and inability to record a clear EEG during usage
of this type of telephone by the patient. Therefore for evaluation
of such influence data that was received either using the unmodulated
signal generator or by the researching residual effects after turning
of cellular phone are used very often. The both of this approaches
do not describe the real influence of modulated high frequency signal
in EEG in real time and that is why they can be used only for initial
estimation of such influence.
It should be also taken into account that cellular
phone do not provide continuous radiation, but transmits the information
partially (in frames), which means that between frames the transmitter
works with zero power. The frequency off/on of the transmitter is
approximately equal to 217 Hz. The carrier frequency is close to
900 or 1800MHz. Under influence of such signal electric currents
changing from 0 to maximum values with the period of datum portion
change approximately during 5 msec occur in the electrolytes. It
is equal to an effect of amplitude-modulated signal with 100% modulation
depth, unlike usual radiophone, in which narrow-band frequency modulation
is used and where these effects are absent.
The current in conducting medium of isotonic NaCl
solution can be easily registered using the low-frequency oscillograph
Fig.1 Snapshot from oscillograph
C1-83 screen, scanning 2mV/point, 2 msec/point. Ericsson A1018S
900 MHz phone. NaCl solution. AgCl weak-polarized EEG electrodes.
The map of the field generated by a cellular phone
is shown in Fig.2.
Fig.2. Mobile phone's electromagnetic
field map synthesized by "CST Microwave Studio" program
(published by authority of "ElectronTrade" company, Russia).
Pay attention to the very complicated spatial distribution
of a signal, and its locking in the mediums of maximum conduction.
It means, that the biggest physiological effect will be strongly
pronounced in the places of the largest area of contact with liquor.
And the locking of the field through the area of ipsilateral eyeball
makes us suggest that the influence on the basal surface of the
brain might be even more than on the areas directly adjoining with
the antenna. Besides that, all areas with intensive liquor dynamics
become (according to this scheme) the places with possible significant
local gradient appearance.
Naturally, the changes in EEG will be the most
interesting precisely during the presence of this field rather then
after its turning off. But to register an EEG signal during a cellular
phone operation is a difficult engineering task. Usual electroencephalograph
can not function with the presence of such noise (see Fig.3), and
the further trials of signal filtration are doomed to failure (detailed
research does not merge with this publication).
Nevertheless the solution exists, and blameless
registration off EEG in such conditions is possible. Analyzing the
first seconds of record, the observable changes absence amazes.
The depression of alpha activity and all prescribed test irritants
responses are registered as well. Moreover, the frequency of the
main rhythm retains with a high preciseness and the signal spectrum
changes slightly. And if to rate an EEG by each channel separately,
it can be discovered just some reliable increase in median frequency
of spectrum which coincides with the findings of other experiments
. Additionally, single sharp waves are registered in the areas
close to the antenna.
Fig.3. The noise in EEG when
turning on the cellular phone. The patient's eyes are closed. The
observation of electrophysiological laboratory of Central Clinical
Hospital N5 (Kharkov, Ukraine).
Fig.4. The EEG of a healthy patient. The patient's eyes are
closed. Moment of turning the cellular phone on is marked with
an arrow. The registration is done on the ExpertTM EEG system,
made by the TREDEX Company Ltd. (Kharkov, Ukraine).