Magnetic properties of human hippocampal tissue--evaluation of artefact and contamination sources.

To investigate the possibility that postmortem chemical alteration or contamination is responsible for recent results indicating the presence of magnetite in human brain tissue and to determine whether magnetite is present in living brain tissue, we examined tissue samples resected from six patients during amygdalohippocampectomy operations. The tissue samples were sealed in sterilized vials in the operating theater and placed into liquid nitrogen directly after removal to prevent changes in tissue chemistry after the death of the brain cells. The low temperature magnetic properties of the tissue were measured to determine the presence of ferro- or ferrimagnetic material in the tissue. The results of these experiments indicate that magnetite is present in the tissue. In addition, results of experiments designed to control for airborne contamination and contamination during cauterization of vessels during surgery indicate that these are not significant sources of magnetite contamination in the tissue.