Measurement of electrical impedance in the human brain

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Abstract
The impedance of small volumes of cerebral tissue has been recorded in 5 patients with electrodes chronically implanted in a number of brain structures for 3 to 4 weeks. In patients with temporal lobe epilepsy, the abnormal hippocampus and hippocampal gyrus tended to have a relatively lower impedance than the same structures on the normal side. Moreover, normal tissue exhibited more prolonged changes in impedance following changes in alveolar CO2 pressure than did the epileptic tissue. Differences in base line impedance and reactivity to CO2 were also seen in different normal structures (amygdaloid nucleus and caudate nucleus) in patients with movement disorders. It is suggested that the measurement of impedance may be used to indicate microscopical abnormalities in tissue structure.