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Effect of a 915-MHz simulated mobile phone signal on cognitive function in man.

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Preece, AW, Iwi, G, Davies-Smith, A, Wesnes, K, Butler, S, Lim, E, Varey, A · 1999

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Mobile phone signals at typical power levels can measurably alter brain function, specifically improving reaction times in exposed brain regions.

Plain English Summary

Summary written for general audiences

Researchers tested whether mobile phone signals at 915 MHz affect brain function by having 36 people perform cognitive tests while exposed to simulated phone radiation. They found that exposure made people react faster on choice reaction time tests, but had no effect on memory tasks. The faster reaction times suggest the phone signals may be affecting a specific brain region called the angular gyrus, which processes visual and speech information.

Why This Matters

This 1999 study provides early evidence that mobile phone radiation can measurably alter brain function, even at the relatively low power levels typical of cell phones (about 1 watt). The finding that 915 MHz signals improved reaction times while leaving memory unchanged suggests RF radiation affects specific brain regions rather than causing general cognitive impairment. What makes this research particularly significant is that it demonstrates biological effects from RF exposure levels similar to what millions of people experience daily during phone calls. The researchers noted the effect was stronger with analog signals compared to digital, which aligns with other research showing that signal modulation patterns influence biological responses. While faster reaction times might seem beneficial, any measurable change in brain function from RF exposure raises important questions about long-term neurological effects from chronic mobile phone use.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 915 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 915 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. The study examined exposure from: 915 MHz

Study Details

To examine whether a simulated mobile telephone transmission at 915 MHz has an effect on cognitive function in man.

Thirty-six subjects in two groups were each given two training sessions and then three test sessions...

In both groups, the only test affected was the choice reaction time and this showed as an increase i...

There was evidence of an increase in responsiveness, strongly in the analogue and less in the digital simulation, in choice reaction time. This could be associated with an effect on the angular gyrus that acts as an interface between the visual and speech centres and which lies directly under and on the same side as the antenna. Such an effect could be consistent with mild localized heating, or possibly a non-thermal response, which is nevertheless power-dependent.

Cite This Study
Preece, AW, Iwi, G, Davies-Smith, A, Wesnes, K, Butler, S, Lim, E, Varey, A (1999). Effect of a 915-MHz simulated mobile phone signal on cognitive function in man. Int J Radiat Biol 75(4):447-456, 1999.
Show BibTeX
@article{preece_1999_effect_of_a_915mhz_2529,
  author = {Preece and AW and Iwi and G and Davies-Smith and A and Wesnes and K and Butler and S and Lim and E and Varey and A},
  title = {Effect of a 915-MHz simulated mobile phone signal on cognitive function in man.},
  year = {1999},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/10331850/},
}
PubMed: 10331850

Cited By (341 papers)

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Quick Questions About This Study

Yes, a 1999 study found that 915 MHz mobile phone signals made people react faster on choice reaction time tests. The researchers tested 36 participants and discovered the radiation exposure decreased reaction times, suggesting the signals may affect the angular gyrus brain region that processes visual and speech information.
Research suggests 915 MHz phone signals may affect the angular gyrus, a brain region that interfaces between visual and speech centers. A 1999 study found faster reaction times during exposure, with researchers noting this brain area lies directly under where phone antennas are positioned during calls.
A 1999 study found that 915 MHz mobile phone radiation had no effect on memory function. Researchers tested word, number, picture recall, and spatial memory in 36 participants, finding no changes in any memory tasks despite the radiation affecting reaction times in other tests.
Only choice reaction time tests showed changes from 915 MHz phone radiation exposure in a 1999 study. Memory tests including word recall, number recall, picture recall, and spatial memory remained unaffected, indicating the radiation specifically impacts reaction speed rather than memory formation or retrieval.
Researchers suggest 915 MHz phone radiation effects could result from either mild localized heating or a non-thermal response that's still power-dependent. The 1999 study found faster reaction times during exposure but couldn't definitively determine whether the brain changes resulted from heating or other mechanisms.