OLFACTORY BULB RESPONSES IN THE TURTLE, WITH SPECIAL REFERENCE TO THE DEEP NEGATIVE SPIKE

Abstract

The orthodromic cortical response induced by the olfactory nerve stimulation was analysed by the depth recording and also the commissural and the antidromic stimulations. The following results were obtained;1. The orthodromic cortical response (OCR) consists of two components: the initial potential and the slow potential, negative in sign, at the cortical surface. When recording in the external plexiform layer, the negative deep spike of 3-5 msec duration occurred, following by the slow potential. The latency is about 15 msec from the onset of the initial potential and remains constant throughout the external plexiform layer. The recovery process of deep spike is extremely slow, requiring 2 sec or more for full recovery. In the deeper layer, unit discharge appeared.2. In the internal granular layer the commissural cortical response (CCR) consists of positive-negative slow potential having a long latency of 60 msec. The deep spike does not interact with the preceding CCR.3. The antidromic stimulation induces the grouped spike discharges and slow potential in the depth recording. The both negative slow potentials of OCR and antidromic cortical response (ACR) are depressed by the commissural stimulation, but the deep spike of OCR and the grouped spikes of ACR do not interact with the commissural stimulation.From the above findings, it seems likely that the deep spike is generated in the radially oriented secondary element, namely the apical dendrites of the mitral cell.