PHEROMONE-EVOKED POTENTIALS AND OSCILLATIONS IN THE ANTENNAL LOBES OFTHE SPHINX MOTH MANDUCA-SEXTA

Using intra- and extracellular recording methods, we studied the activ ity of pheromone-responsive projection neurons in the antennal lobe of the moth Manduca sexta. Intracellularly recorded responses of neurons to antennal stimulation with the pheromone blend characteristically i ncluded both inhibitory and excitatory stages of various strengths. To observe the activity of larger groups of neurons, we recorded respons es extracellularly in the macroglomerular complex of the antennal lobe . The macroglomerular complex is part of a specialized olfactory subsy stem and the site of first-order central processing of sex-pheromonal information. Odors such as the pheromone blend and host-plant (tobacco ) volatiles gave rise to evoked potentials that were reproducible upon repeated antennal stimulation. Evoked potentials showed overriding hi gh-frequency oscillations when the antenna was stimulated with the phe romone blend or with either one of the two key pheromone components. T he frequency of the oscillations was in the range of 30-50 Hz. Amplitu de and frequency of the oscillations varied during the response to phe romonal stimulation. Recording intracellular and extracellular activit y simultaneously revealed phase-locking of action potentials to potent ial oscillations. The results suggest that the activity of neurons of the macroglomerular complex was temporally synchronized, potentially t o strengthen the pheromone signal and to improve olfactory perception.