AFFERENT AND EFFERENT INFLUENCES ON ACTIVITY PATTERN OF SINGLE OLFACTORY NEURONS

Single‐unit activity was recorded from secondary olfactory neurons in the burbot (Lota lota L.) with either microelectrodes from the cell soma in the bulb or from single fibers in the olfactory tract. Stimulation of the olfactory epithelium on the contra‐ or ipsilateral side was made with glutamic acid, morpholin, and taurin, with both the efferent system intact and with the efferent activity to the bulb blocked by cutting or cooling the olfactory tract. Statistical time‐series analyses of the impulse sequences were performed in all experimental conditions. The interval histograms obtained were highly skewed. The histograms of the fiber recordings were often bimodal, whereas in the microelectrode recordings several exponential histograms were found. The intensity functions in two‐thirds of the fiber recordings showed rhythmical time dependent oscillations in the firing probability. These oscillations seemed to be of peripheral origin. The activity from the microelectrode recordings usually revealed renewal processes. Comparisons of the different experimental conditions showed a great variety of influences of peripheral stimuli and efferent activity on the activity patterns of the secondary neurons. Most frequently the differences between different experimental conditions of one cell were smaller than the differences between cells. Therefore, it does not seem likely that differences in external conditions would be coded as variations in the time structure of the impulse sequence. © 1969 Scandinavian Physiological Society