Biological Effects - RF/Microwave Interaction with Biological Tissues - page 104

modulated and CW microwave exposure were found on morphology and cell
surface negative charges. As static experimental models (i.e., biochemical
models) do not give information about the transient effects and functional
changes induced by EM exposure, especially in the nervous system, an electro-
physiological approach is more appropriate to explain the phenomena in the
CNS. Such experiments [52] were performed on F 1 hybrid male anesthetized
rats. They addressed the following questions: (a) Does a weak modulated field
cause measurable effects on systemic and/or localized regulation mechanisms
in the CNS? (b) Is there any correlation between the field activated systemic
and/or localized regulatory mechanisms and the changes in CNS activity? (c)
Does evaluation of measured biopotentials provide more information about
the effects on the CNS of modulated and CW field exposure?
In two series of experiments on 40 anesthetized rats (a) before and after
10 min whole-body exposure to 2.45-GHz CW and (b) during 30 min exposure
to 16-Hz amplitude modulation 4 GHz, the effects on the CNS were observed
simultaneously with those of the cardiovascular system by quantitative
polygraphic measurements. Transient effects of absorbed CW and modulated
microwave radiation in the brain were examined in order to clarify the
involvement of physiological modalities during local and/or systemic exposure.
The local cerebral modalities (EEG, rheoencephalogram (REG), DC imped-
ance, and brain temperature) were recorded simultaneously with the systemic
regulation modalities (ECG, respiration, and rectal temperature). Slight
changes in cerebral metabolism and cerebral blood were observed during
exposure. These transient alterations did not exceed the range of normal phys-
iological variations, although various compensating factors with different
speeds were involved.
The total power of EEG spectra increased after whole-body 30 mW cm -2 ,
2.45-GHz CW exposure. No changes occurred below 10 mW cm -2 . The cere-
bral blood flow (CBF) increased above 10 mW cm -2 . The power of EEG delta
waves (0.5-4 Hz) was increased by brain localized 4-GHz CW exposure at
SAR = 42Wkg -1 , simultaneously with the REG amplitude as an index of CBF.
Amplitude modulation at 16 Hz and SAR = 8.4Wkg -1 were associated with
increased power of EEG beta waves (14.5-30 Hz). Changes were not observed
in the CBF. Continuous-wave exposure at SAR = 8.4Wkg -1 increased the CBF
but did not modify EEG spectra. Thus, the correlation between physiological
modalities in microwave-activated systemic or localized regulatory mecha-
nisms and changes in the CNS do not seem to be identical. It has not been
clarified whether the mechanisms of the observed microwave-induced modi-
fications are due to energy absorption in the brain.
The necessity for quantitative evaluation of these phenomena concerning
CNS functions is obvious.

3.2.5 Nervous System Modeling and Simulation

Models and computer simulations of nervous fibers and of the nervous system
have developed rather recently. McNeal introduced a first step in computer