Accession Number:

AD0620527

Title:

THE SPECIFIC IMPEDANCE OF THE DORSAL COLUMNS OF CAT: AN ANISOTROPIC MEDIUM,

Descriptive Note:

Corporate Author:

MICHIGAN UNIV ANN ARBOR DEPT OF PHYSIOLOGY

Report Date:

1964-10-05

Pagination or Media Count:

15.0

Abstract:

Low frequency, nonstimulating current was passed from a small electrode on the surface of the dorsal columns in the cervical cord of cats. A glass microelectrode was used to record the voltage at distances of 0.5 to 2 mm from the current electrode. The voltage fell off more rapidly in depth and across the dorsal columns than it did longitudinally--the resistance was lower in the longitudinal direction. Accordingly, the dorsal columns are anisotropic. An approximate equation is presented which describes the data fairly well and which is consistent with the anatomy. From this equation, the resistivity in the longitudinal direction was 138 to 212 ohm-cm and in the transverse direction, 1,211 ohm-cm. These values are shown to be consistent with the view that the anisotropy is primarily due to current flowing longitudinally in axons. The frequency dependence of the specific impedance was also measured. Some features of this frequency dependence have no clear explanation, but some of them are consistent with a nodal membrane having a time constant of roughly 50 microseconds. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE