Unit activity during polarization of the optic tract and lateral geniculate body

Abstract

Records of activity in single cells of the optic tract and lateral geniculate body during prolonged anodal and cathodal polarization with a large extracellular electrode indicate that both kinds of polarization applied to fiber tracts or in the nuclear region can interrupt the transmission of action spikes at strengths as low as 0.15 ma; cathodal polarization was more effective than anodal polarization. Both kinds of polarization were also found to elicit repetitive propagated activity which varied in frequency with the strength of polarizing current; anodal polarization was much more effective in this regard. Repetitive activity was generated when the polarizing electrode was placed among fibers many millimeters from their cell bodies and axonal endings and when the polarizing electrode was placed in a nuclear region. Repetitive activity during anodal polarization is believed to originate in regions of induced depolarization accompanying the outward flow of polarizing current across the membrane at some distance from the polarizing electrode.