EFFECTS OF AGING ON VISUAL-DISCRIMINATION LEARNING IN DROSOPHILA-MELANOGASTER

Two experiments examined conditioned suppression of the Proboscis Exte nsion Response (PER), unconditionally released by sucrose stimulation of gustatory tarsal receptors, in young (7-day-old), middle-aged (30-d ay-old) and old (50-day-old) Drosophila melanogaster males, reared at 25-degrees-C. Individual flies were trained in a differential conditio ning procedure in which a white stimulus signalled a quinine reinforce r, whereas a black stimulus was non-reinforced. When trained from the outset with the discriminative procedure, flies of all ages acquired t he discrimination, although the acquisition of PER suppression to the white stimulus was retarded in middle-aged and old flies. The retardat ion of the acquisition of PER suppression in middle-aged and old flies was replicated in a second study in which the flies received simple c onditioning to the white stimulus prior to discrimination training.