Honeybee olfactory sensilla behave as integrated processing units

Honeybee placode sensilla contain 18–35 olfactory receptor neurons. In insects, such neurons are thought to not interact with one another before reaching the central nervous system. Extracellular, multiunit recordings were made from the placodes and separated into spike shape classes, termed subplacode units. An analysis of the response spectra of subplacode units demonstrated that subplacode units with similar response spectra were more likely to be found in different placodes than in the same placode. An analysis was made of the mean interspike intervals and its variation for whole placodes and subplacode units. The coefficient of variation for whole placodes was less than that for subplacode units. Whole placode spike trains are therefore more uniform than subplacode spike trains, indicating that neurons might not be firing independently of each other.