Integration of temperature and olfactory information in cockroach antennal lobe glomeruli

Individual neurons in the antennal lobe of the cockroach not only respond to warming, cooling and the odor of lemon oil but they also integrate the responses to simultaneously occurring temperature and olfactory stimuli. This integration results in an increase or decrease of the neuron's activity as compared to its responses to the temperature stimuli presented alone. The mean gain for a change in temperature in the warm and cold direction is 9.5 (imp s–1) °C–1 and 10.2 (imp s–1) °C–1, respectively. Thus, the average neuron elevates its impulse frequency by 1 imp s–1 when temperature is increased by 0.1°C or decreased by 0.09°C. Examination of response scatter reveals that the difference required between two warm or two cold stimuli to be discriminated is 0.5°C. Similar values for gain and resolving power are obtained for the enhanced responses to the warm-odor and the cold-odor stimulus combinations. The neurons described are: (1) local interneurons innervating a number of glomeruli distributed within the antennal lobe, and (2) projection neurons collecting information from single glomeruli at 140–280 µm from the surface of the antennal lobe and providing links with the calyces of the mushroom bodies and the lateral lobe of the protocerebrum.