Response characteristics and after effects of multimodal neurons in the mushroom body area of the honey bee

ABSTRACT. Single cell recordings in the mushroom body area of the bee revealed that the majority of cells responds to more than one modality. Five different modalities were tested: light, scent, sugar‐water applied to the antennae or the proboscis, and mechanical stimuli of the antennae (air puffs). The background discharge (spontaneous) frequency of the neurons was correlated with the recording site, being low in the calyx area and high in the area of the β‐lobes. No correlation between the reaction spectra of neurons and the recording location was found. A simple classification of single cells into different classes is not possible. Some units change their response pattern during recording; this is interpreted as an indication of other inputs which were not controllable in the experiments. After‐effects, lasting some seconds to minutes, were found with scent, light and sugar‐water stimuli. The olfactory and gustatory inputs obviously play an important role in activating multimodal units. Some neurons showed increasing sensitivity for a scent after a number of olfactory conditionings. An increase of sensitivity in these units is correlated with an increase of the spontaneous discharge frequency.