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Dielectric Properties of Brain Tissue between 0·01 and 10 GHz

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KENNETH R. FOSTER, JONATHAN L. SCHEPPS, RICHARD D. STOY, HERMAN P. SCHWAN · 1979

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Brain tissue's electrical properties change dramatically across microwave frequencies, providing the scientific foundation for understanding wireless device interactions with our heads.

Plain English Summary

Summary written for general audiences

Researchers measured how dog brain tissue responds to microwave frequencies from 0.01 to 10 GHz, finding that grey and white matter have different electrical properties that change predictably with frequency. The study revealed that brain tissue contains about 70% water in grey matter and 35% in white matter, with some water not contributing to electrical responses above 1 GHz.

Why This Matters

This foundational 1978 research provides critical baseline data that remains relevant today as we grapple with increasing microwave exposure from wireless devices. The science demonstrates that brain tissue has distinct electrical properties that vary dramatically between grey and white matter - knowledge essential for understanding how modern EMF sources interact with our heads. What makes this particularly significant is that the frequencies studied (0.01-10 GHz) encompass the range used by cell phones, WiFi, and many wireless technologies we use daily. The reality is that this type of fundamental research helped establish the scientific foundation for calculating specific absorption rates (SAR) - the measure regulators use to set exposure limits. Yet the study also reveals something concerning: not all water in brain tissue responds to microwave frequencies as expected, suggesting our understanding of EMF-brain interactions may be incomplete.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
KENNETH R. FOSTER, JONATHAN L. SCHEPPS, RICHARD D. STOY, HERMAN P. SCHWAN (1979). Dielectric Properties of Brain Tissue between 0·01 and 10 GHz.
Show BibTeX
@article{dielectric_properties_of_brain_tissue_between_0_01_and_10_ghz_g5114,
  author = {KENNETH R. FOSTER and JONATHAN L. SCHEPPS and RICHARD D. STOY and HERMAN P. SCHWAN},
  title = {Dielectric Properties of Brain Tissue between 0·01 and 10 GHz},
  year = {1979},
  
  
}

Quick Questions About This Study

Grey matter contains approximately 70% water while white matter contains only 35%, making grey matter much more electrically conductive and responsive to microwave frequencies between 0.01-10 GHz.
Scientists measured dielectric properties across 0.01 to 10 GHz, covering frequencies now used by cell phones, WiFi, Bluetooth, and other common wireless technologies in our daily environment.
Researchers found that measured water content was 10-15% higher than what contributed to electrical responses, suggesting some brain water is bound or structured differently than free water.
Around 1 GHz, brain tissue conductivity shifts from following a power law pattern to increasing quadratically with frequency due to water molecule rotation effects at higher frequencies.
Brain tissue shows rotational relaxation at 21-24 GHz, slightly below pure water's 25 GHz characteristic frequency at body temperature, indicating tissue structure affects water behavior.