Neural coding in antennal olfactory cells of tsetse flies (Glossina spp.)

Spike trains from individual antennal olfactory cells of tsetse flies(Glossina spp.) obtained during steady-state conditions (spontaneous aswell as during stimulation with 1-octen-3-ol) and dynamic stimulation withrepetitive pulses of 1-octen-3-ol were investigated by studying the spikefrequency and the temporal structure of the trains. In general, stimulationchanges the intensity of the spike activity but leaves the underlyingstochastic structure unaffected. This structure turns out to be a renewalprocess. The only independently varying parameter in this process is themean interspike interval length, suggesting that olfactory cells of tsetseflies may transmit information via a frequency coding. In spike recordswith high firing rates, however, the stationary records had significantnegative first- order serial correlation coefficients and were non-renewal.Some cells in this study were capable of precisely encoding the onset ofthe odour pulses at frequencies up to at least 3 Hz. Cells with a rapidreturn to pre-stimulus activity at the end of stimulation responded moreadequately to pulsed stimuli than cells with a long increased spikefrequency. While short-firing cells process information via a frequencycode, long-firing cells responded with two distinctive phases: a phasic,non-renewal response and a tonic, renewal response which may function as amemory of previous stimulations.