Automatic stimulus presentation for the proboscis extension reflex in diptera

An apparatus is described that automates the elicitation of the proboscis extension reflex (PER) in dipterans. The PER has been used as a measure of both classical conditioning and central excitation. Most studies of PER have employed manual stimulation, which adds inter- and intraexperimenter differences in technique as another source of variance. The advantages of this apparatus are (1) elimination of individual differences in manual techniques of experimenters as a possible source of error variance and (2) capability of stimulating several flies individually during a single session. An experiment is reported comparing the manual and automated methods.