de Tommaso M, Rossi P, Falsaperla R, Francesco Vde V, Santoro R, Federici A. 2009. Mobile phones exposure induces changes of contingent negative variation in humans. Neurosci Lett. 464(2):79-83.
The use of mobile phones, especially those based on GSM communication protocol, has grown in recent years, raising concerns about the potential effects on users’ brains. A recent review concluded that GSM signals may induce changes in brain excitability. The authors suggest that the effect of low-level magnetic fields at Extremely Low Frequencies (ELF) produced by the battery and internal circuitry of the phones should also be considered. The initial contingent negative variation (iCNV) is an electrical signal produced by the brain in response to stimuli, while a subject is waiting for a second event and preparing for task performance.
The aim of this study was to test iCNV changes induced by 900MHz GSM exposure in a double blind design in healthy volunteers under three experimental conditions: (A) exposed; (B) sham exposed; and (C) off.
Ten healthy right-handed volunteers (5 male, 5 female) aged 20-31 years old were included. The exposure set-up consisted of a mobile phone mounted on the left hand side of a plastic helmet. The B phone was modified so that when the phone was turned on, the internal circuitry was active, but no radiofrequency power was delivered by the antenna. Subjects were seated in a comfortable chair facing speakers from which two acoustic stimuli were delivered between 4 and 6 seconds apart, S1 (warning stimulus), and S2 (imperative stimulus). Upon hearing S2, subjects pressed a button on a box they held in their hands as fast as possible. Thirty electrodes were positioned on the subjects’ scalp to measure iCNV. For each subject, iCNV was measured for 10 minutes in each of the three experimental conditions. Exposure conditions occurred in a random order and were performed on the same day with a 10 minute time interval between each exposure.
The amplitude of the iCNV signal was significantly reduced during both the A and B exposure conditions compared to condition C. In addition, the iCNV habituation index was reduced in the A and B exposure conditions compared to the C condition.
Interpretation and Limitations
The findings of this study are in accordance with other studies on brain function in relation to mobile phone exposure. One study found an increase in brain activity in the motor region directly exposed to the GSM signal. Therefore, it may be that the observed iCNV amplitude reduction may be the result of general deactivation of a specific area of the brain that is compensating for the hyper-excitability of the motor areas of the brain directly exposed to EMF. Although condition B produced the same results as condition A, the effects were more exaggerated in condition A, suggesting that both ELF and GSM signals contribute to the results. The main limitation of this study is the small sample size.
Mobile phone exposure may act on brain electrical activity, reducing the arousal and expectation of warning stimulus, caused by both the GSM signal and the low magnetic field induced by battery and internal circuits.