Site of Origin and Reflex Behavior of Postsynaptic Negative Potentials Recorded from the Spinal Cord ‡

In a previous paper' evidence has been offered that not only the intra-medullary spike but also an early component of the following negative potential (labelled Nia) is of presynaptic origin. N1a was attributed to activity in afferent terminals. The present note deals with the site of origin FIG. 1. Cat 11-11-54. Stimulus to internal saphenous nerve. All upper traces from point 1 on the ipsilateral side. Lower traces from contralateral points 2, 3, 4, 5, and 6 respectively. Time for inner ring of records: 1000 cycle; for outer ring: 60 cycle. Note that N2 does not spread across cord. of the postsynaptic negative components, N1b, N2, (a secondary wave cropping out from the descending limb of N1b), and finally the late negative wave seen occasionally in decerebrate cats several milliseconds after the termination of the N1 N2 complex.5 The technique employed is described in the earlier paper.'