Coherent oscillations in membrane potential synchronize impulse bursts in central olfactory neurons of the crayfish

Lateral protocerebral interneurons (LPIs) in the central olfactory pathway of the freshwater crayfish Procambarus clarkii reside within the lateral pr otocerebrum and receive direct input from projection neurons of the olfacto ry midbrain. The LPIs exhibit periodic (0.5 Hz) changes in membrane potenti al that are imposed on them synaptically. Acute surgical experiments indica te that the synaptic activity originates from a group of oscillatory neuron s lying within the lateral protocerebrum. Simultaneous intracellular record ings from many LPI pairs indicate that this periodic synaptic input is sync hronous and coherent among the population of similar to 200 LPIs on each si de of the brain. In many LPIs, specific odors applied to antennules in isol ated head preparations generate long-lasting excitatory postsynaptic potent ials and impulse bursts. The impulse bursts are generated only near the pea ks of the ongoing depolarizations, similar to 1 s after stimulus applicatio n, and so the periodic baseline activity is instrumental in timing burst ge neration. Simultaneous recordings from pairs of LPIs show that, when impuls e bursts occur in both cells after an odorant stimulus, they are synchroniz ed by the common periodic depolarizations. We conclude that the common, per iodic activity in LPIs can synchronize impulse bursts in subsets of these n eurons, possibly generating powerful long-lasting postsynaptic effects in d ownstream target neurons.