Magnetic analyses of hippocampal material from deceased normal and epileptic subjects, and from the surgically removed epileptogenic zone of a living patient have been carried out. All had magnetic characteristics similar to those reported for other parts of the brain . These characteristics along with low temperature analysis indicate that the magnetic material is present in a wide range of grain sizes. The low temperature analysis also revealed the presence of magnetite through manifestation of its low temperature transition. The wide range of grain sizes is similar to magnetite produced extracellularly by the GS15 strain of bacteria and unlike that found in magnetotactic bacteria MV-1, which has a restricted grain size range. Optical microscopy of slices revealed rare 5-10 micron clusters of finer opaque particles, which were demonstrated with Magnetic Force Microscopy to be magnetic. One of these was shown with EDAX to contain All, Ca, Fe, and K, with approximate weight percentages of 55, 19, 19, and 5, respectively.
Bibliographical noteFunding Information:
We thank Dr. Mark Rosenthaol f The School of Medicine,U CLA and SepulvedaV eteran'sA dministratioMn edicalC enter,D r. W. W. Tourtellottea ndDr. H. GregorW ieserf or makingh ippocampussa m-ples availablef or us. We thank Mr. Colby Boles of Digital Instruments,S antaB arbara,f or Magnetic Force Microscopei magesa nd Dr. Michael Richardsono, f St. Francis Hospital,S antaB arbara,f or drawing our attentionto the literatureo n brain sand. M. F. thanks ProfessoWr illiamLowrie and his colleaguefso r makinga sabbatical at ETH-H6nggerberpgo ssible,d uringwhich this project was initiated.W e also thanko ne anonymourse viewerw, hosec ommentcso n-tributedg reatlyt o the final versiono f this paper.T his work is supported by the Swiss National Funds Grant No. 21-29834.90a nd a UCSB AcademicS enateG rant.T he work was revieweda ndapproved by the InstitutionR eviewBoard (IRB) at UCSB and by the University Hospital Medical Ethics Committeein Zurich.