Activities of antennal and ocellar interneurones in the protocerebrum of the honey-bee.

1. Unit responses to olfactory and mechanical stimuli of the antennae, and illumination of the ocelli, were recorded extracellularly in the protocerebrum of the honey-bee. 2. Bimodal units responded both to antennal and to ocellar stimuli; antennal units responded to the former and the ocellar units to the latter. Some antennal units responded to olfactory stimuli (olfactory units), and others responded to mechanical stimuli (mechanical units). 3. Ocellar units in the brain showed phasic responses at the start and/or cessation of illumination. Six types of responses were found. 4. About two-thirds of the bimodal units showed the same type of response to stimulation of the antennae as to stimulation of the ocelli. Most of them showed excitation by each stimulus. 5. Bimodal units were distributed around the alpha-lobe in the protocerebral lobe, whereas the antennal and the ocellar units were widely distributed. 6. By turning off the ocellar illumination, background discharge frequency, and the pattern and magnitude of responses to antennal stimuli, were changed. The activities of the ocellar units were altered by inputs from the antenna. 7. It was postulated that antennal and ocellar inputs converge and interact with each other in the protocerebral lobe of the honey-bee.