factor reduction in the induced electric field (achieved by changing the magnetic field more slowly)
had no effect on the number of spindles. Similar changes in the EEG due to EMFs of frequencies
ranging from 50 Hz to 3 GHz have been reported (4, 72).
Fig. 5.1. Change in number of spindles in the rabbit induced by exposure to 300 gauss. N is the
average number of spindles per 10 second periods that occurred during 604 exposures.
Three additional aspects of the Kholodov-Chizhenkova studies deserve mention: (1) the number
of spindles observed after a change in the magnetic field increased regardless of whether the change
was on-to-off or off-to-on (Fig. 5.1); (2) there was an after-effect in which the number of spindles
remained elevated even when the field was tumed off (Fig. 5.1); (3) the most reactive regions were the
hypothalamus and the cortex, and the least reactive region was the reticular formation of the midbrain.
Kholodov found a desynchronization reaction, but no changes in spindles or delta waves, when
rabbits were exposed for 1 minute to 500 kv/m DC electric fields (2). Lott and McCain (5) measured
the total integrated EEG in rats before, during, and after exposure to a DC field of 10 kv/m (Fig. 5.2).
They found a transient increase associated with either the application or removal of the field, a steady
response that persisted during application of the field, and an after-effect. A 640 Hz pulsed field, 40
v/m maximum, also increased the total integrated EEG, particularly for readings from the hypothalmic
region.
Fig. 5.2. Total brain activity of anesthetized rats exposed to a DC electric field of 10kv/m. Each point
represents a mean of 9 experiments; readings were not taken for 6 minutes following application of the
EMF.
At high frequencies, a different effect on the total integrated electrical activity was observed.
Goldstein (68) exposed rabbits for 5 minutes to 700-2.800 µW/cm2, 9.3 GHz, and found no EEG
changes during the exposure period. Commencing about I0 minutes after exposure, however, there
ELECTROMAGNETISM & LIFE - 72