TRANSMISSION OF IMPULSES THROUGH THE BURDACH NUCLEUS

Abstract

Following a single shock applied to a nerve of the forelimb there passes through the dorsal column to the nucleus of Burdach a volley of primary impulses succeeded after about 3 msec. by the dorsal column relay of Hursh. These impulses produce in the nucleus (surface lead) a post-primary negative potential lasting about 5 msec. During the course of this potential, impulses are discharged into the lemniscus. Conditioned transmission through the nucleus has the following properties The refractory period at the synapse is not longer than that of the primary axons. Transmission after the second of two volleys at intervals less than 5 msec. is limited to a short burst of spikes (lasting ca. 1.0 msec.) following the second primary volley by a synapse time of 0.6 msec. Addition of the later, more inhibitable, portion of the transmitted impulses starts at intervals of 5 msec. and restoration is complete at 15 to 50 msec. Thus the transmission of a tetanus through the nucleus is essentially one-to-one conduction between primary neurons and neurons of the lemniscus fibers. A positive wave lasting about 100 msec, recorded at the surface of the nucleus, is correlated with activity in the underlying reticular substance.