Response Characteristics and Identification of Extrinsic Mushroom Body Neurons of the Bee

The activity o f single neurons with constant discharge frequencies in the area around the a-lobe o f the mushroom bodies o f the bee was recorded intracellularly. The spontaneous discharge fre­ quency o f these neurons ranged between 5 and 95 impulses per second. When stimulated, about 80 percent o f the neurons responded to at least one o f five different sensory modalities: scent; light; air current to the antennae; sugar water applied to the antennae and to the proboscis. 45 percent o f the neurons responded to two or more modalities, these multimodal neurons are com ­ mon in the median protocerebrum o f the bee. The differentiated response pattern o f the cells does not allow a simple classification. Some o f the neurons were identified after the injection o f the flu­ orescent dye Procion yellow. We found 4 neurons with arborizations in the a-lobe and the calyces o f the mushroom bodies.