Denise L. Hamblin

Effects of mobile phone emissions on human brain activity and sleep variables

Purpose : To compare the findings of the main studies that have examined the effects of GSM mobile phone radiofrequency emissions on human brain activity and sleep variables. Materials and methods : Fourteen published studies reporting on human brain electrical activity measurements during and/or after such radiofrequency emissions were identified and compared. Conclusions : Although, in general, outcomes have been inconsistent and comparison between individual studies is difficult, enhanced electroencephalogram alpha-band power has been noted in several of the studies, a phenomenon also observed in some animal studies. Performance decrements observed in some recent extremely low frequency studies are consistent with enhanced alpha-band power, highlighting the possible role of extremely low frequency fields associated with battery current in mobile phone handsets. However, more complex cognitive tasks appear to show improved performance in relation to mobile phone exposure. Significant cognitive effects have been reported using both modulated and unmodulated radiofrequency carriers. The possibility of putative effects being due to extremely low frequency demodulation is therefore unlikely. There are no obvious associations between the site of exposure and regions of the brain from which effects are reported or implied. Lastly, radiofrequency effects have been reported to occur both during exposure and up to 1 h or so after cessation of exposure.

Examining the effects of electromagnetic fields emitted by GSM mobile phones on human event-related potentials and performance during an auditory task

OBJECTIVE Due to the widespread use of mobile phones (MP), it is important to determine whether they affect human physiology. The aim of this study was to explore the sensitivity of auditory event-related potentials to electromagnetic emissions. METHODS Twelve participants attended two sessions, 1 week apart. Participants performed an auditory oddball task while they were exposed to an active MP during one session and sham exposure during the other. Each condition lasted 1 h and order was counterbalanced. N100 and P200 latencies and amplitudes were analysed for non-target waveforms, and N200 and P300 latencies and amplitudes were analysed for target waveforms. RESULTS In real relative to sham exposure N100 amplitude and latency to non-targets were reduced, with the reduction larger over midline and right hemisphere sites. P300 latency to targets was delayed in the real exposure condition, however as this difference was greatest at left frontal and left central sites the interpretation of this result is unclear. Reaction time increased in the real relative to sham condition. No difference in accuracy was found. CONCLUSIONS The results suggest that MP exposure may affect neural activity, particularly in proximity to the phone, however caution should be applied due to the small sample size.

Effects of 2G and 3G mobile phones on performance and electrophysiology in adolescents, young adults and older adults.

OBJECTIVE This study examined sensory and cognitive processing in adolescents, young adults and older adults, when exposed to 2nd (2G) and 3rd (3G) generation mobile phone signals. METHODS Tests employed were the auditory 3-stimulus oddball and the N-back. Forty-one 13-15 year olds, forty-two 19-40 year olds and twenty 55-70 year olds were tested using a double-blind cross-over design, where each participant received Sham, 2G and 3G exposures, separated by at least 4 days. RESULTS 3-Stimulus oddball task: Behavioural: accuracy and reaction time of responses to targets were not affected by exposure. Electrophysiological: augmented N1 was found in the 2G condition (independent of age group). N-back task: Behavioural: the combined groups performed less accurately during the 3G exposure (compared to Sham), with post hoc tests finding this effect separately in the adolescents only. Electrophysiological: delayed ERD/ERS responses of the alpha power were found in both 3G and 2G conditions (compared to Sham; independent of age group). CONCLUSION Employing tasks tailored to each individuals ability level, this study provides support for an effect of acute 2G and 3G exposure on human cognitive function. SIGNIFICANCE The subtlety of mobile phone effect on cognition in our study suggests that it is important to account for individual differences in future mobile phone research.

The use of a 'phantom scalp' to assess the possible direct pickup of mobile phone handset emissions by electroencephalogram electrode leads.

A ‘Phantom Scalp’ was constructed from a conducting foam mat to form a layer under a 62-electrode electroencephalogram cap closely approximating the electrical properties of a human scalp. The mat was placed over a polystyrene manikin head to preserve a correct anatomical arrangement. Electrical signals were recorded with a Global System for Mobile (GSM) communications mobile phone handset in place against the side of the ‘head’. Amplitude spectra were compared for three phone conditions: ‘off’, ‘standby’ and ‘transmit’. At 217 Hz, significant differences were obtained between ‘transmit’ and the other two conditions, but no significant differences were noted for the physiologically important range 0.5–30 Hz. An anomalous difference was noted for one electrode in the range 30–45 Hz.