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June 1964

Impedance Method for Localizing Brain Structures: An Extension of the Method

Author Affiliations

Department of Neurology, Stanford University, on leave of absence as Chief, Laboratory of Neurophysiology, Yerkes Regional Primate Research Center, Emory University, Atlanta, (Dr. Robinson) and Department of Electrical Engineering, University of Maryland (Dr. Tompkins).

Arch Neurol. 1964;10(6):563-574. doi:10.1001/archneur.1964.00460180029002

Introduction  It was previously shown6,7 that variations in impedance measured between the tip of a moving macroelectrode and some remote point could be used to identify passage of the electrode into a variety of structures deep within the brain. By this means, direct localization of the electrode with respect to certain neural structures was possible; in addition, these directly identified areas provided landmarks which served to indirectly localize an even wider variety of structures. Although stereotactic techniques were utilized to orient the electrode, final placement in accordance with impedance changes was shown to be considerably more accurate than if stereotaxis alone had been used.Verification of the localization of the electrodes by means independent of impedance variations was provided by carefully noting behavioral changes evoked by passing a train of stimulating pulses through the electrode at each millimeter of travel. Once the verification has been demonstrated, the stimulating current