PROPERTIES OF CLARKES COLUMN NEURONES

Mechanisms responsible for the high efficacy of synaptic actkation of the dorsal spinocerebellar tract (DSCT) was investigated with intracellular recording from Clarke's column cells in anesthetized spinal cats. The spike potential is brief (mean duration 0.57 msec) and followed by a delayed depolarization. Our observations suggest a high safety for impulse transmission from the initial segment to the soma and from the soma to the dendrites. The afterhyperpolarization is small (<2 mV), shortlasting (30–50 msec) and has a high sensitivity to hyperpolarizing currents. There is only a small conductance change during the afterhyperpolarization. The monosynaptic group I EPSP has a mono‐exponential decay, the time course of which is explained by the passive properties of the membrane. It is postulated that the transmitter action is brief. Possible mechanisms for multiple discharges evoked by group I volleys in DSCT cells are discussed. Injected currents evoke maintained firing and within a wide range there is a linear relation between frequency and current strength (mean slope constant 4.8 imp/sec/mV). Depolarization produced by muscle stretch and injected current have equivalent effect on the firing rate. The properties of DSCT cells seem well adapted to their function to transfer sensory signals and operate over a wide frequency range © 1969 Scandinavian Physiological Society