Operant conditioning of antennal muscle activity in the honey bee (Apis mellifera L.)

Antennal movements of the honey bee can be conditioned operantly under laboratory conditions. Using this behavioural paradigm we have developed a preparation in which the activity of a single antennal muscle has been operantly conditioned. This muscle, the fast flagellum flexor muscle, is innervated by an identified motoneuron whose action potentials correlate 1:1 with the muscle potentials. The activity of the fast flagellum flexor muscle was recorded extracellularly from the scapus of the antenna. The animal was rewarded with a drop of sucrose solution whenever the muscle activity exceeded a defined reward threshold. The reward threshold was one standard deviation above the mean spontaneous frequency prior to conditioning. After ten conditioning trials, the frequency of the muscle potentials had increased significantly compared to the spontaneous frequency. The conditioned changes of frequency were observed for 30 min after conditioning. No significant changes of the frequency were found in the yoke control group. The firing pattern of the muscle potentials did not change significantly after conditioning or feeding. Fixing the antennal joints reduces or abolishes associative operant conditioning. The conditioned changes of the frequency of muscle potentials in the freely moving antenna are directly comparable to the behavioural changes during operant conditioning.