DORSAL COLUMN CONDUCTION OF GROUP I MUSCLE AFFERENT IMPULSES AND THEIR RELAY THROUGH CLARKE'S COLUMN

Abstract

Group I afferent nerve fibers terminate centrally for the most part in the upper lumbar and lower thoracic segments. During this truncated course in the dorsal columns, after supplying myotatic reflex collaterals to the motoneurons, these fibers come into relation with cells of Clarke''s column wherein is established a monosynaptic relay for the projection to the cerebellum of stretch-evoked activity. Conduction velocity of primary afferent projections of Group I fibers in the dorsal columns is non-linear, initial velocity, approximating 110 m. per sec decreasing in steps to about 1/4. Post-synaptic impulses from Clarke''s column ascend Flechsig''s tract at a uniform velocity approximately 110 m. per sec. The synaptic articulations of Group I afferent fibers with motoneurons and with cells of Clarke''s column differ characteristically, considerable summation being requisite for transmission in the motor nuclei, but not in Clarke''s column.