Figure 2. Three methods were used to stimulate basiconic sensilla.

Upper: CO₂ responses were recorded from ab1C neurons using the apparatus of Fig. 1. Ethyl butyrate stimulation of ab3A neurons used the same apparatus with a filter paper cartridge delivering the odorant into the air/propylene stream. Optical stimulation of ab1C and ab3A neurons containing channelrhodoposin-2 was performed by a high intensity blue light emitting diode via a fiber optic. Lower: Multiple action potential recordings were separated by cluster analysis. Raw recordings from an ab1 sensillum to CO₂ (left) and ab3 sensillum to light (right) are shown together with the inputs (PID and light traces), and the separated action potential times.