Antennal movements reveal associative learning in the American cockroach Periplaneta americana

Using antennal movements as an indicator of learning and retention, an associative learning paradigm has been developed to investigate associative memory between visual and olfactory stimuli. Experiments were performed on the restrained cockroach Periplaneta americana, which normally moves its antennae towards a localized odor source. Such "antennal projection responses" (APRs) are exploited to demonstrate long-term memory, where an APR is elicited by a conditioned stimulus (CS; green light point source) paired with a spatially coincident odor [the unconditioned stimulus (US)]. Association of the CS with the US is established after five trials. Before training, a visual cue alone does not elicit an APR. This behavior is elicited by a visual cue only after pairing it with an odor stimulus. The acquired APR to the green light cue persists for up to 72 h, indicative of long-term memory. This paradigm is thus suitable for future studies of neural correlates of learning and memory on restrained animals.