Experimental evolution of olfactory memory in Drosophila melanogaster.
In order to address the nature of genetic variation in learning performance, we investigated the response to classical olfactory conditioning in "high-learning" Drosophila melanogaster lines previously subject to selection for the ability to learn an association between the flavor of an oviposition medium and bitter taste. In a T-maze choice test, the seven high-learning lines were better at avoiding an odor previously associated with aversive mechanical shock than were five unselected "low-learning" lines originating from the same natural population. Thus, the evolved improvement in learning ability of high-learning lines generalized to another aversion learning task involving a different aversive stimulus (shock instead of bitter taste) and a different behavioral context than that used to impose selection. In this olfactory shock task, the high-learning lines showed improvements in the learning rate as well as in two forms of consolidated memory: anesthesia-resistant memory and long-term memory. Thus, genetic variation underlying the experimental evolution of learning performance in the high-learning lines affected several phases of memory formation in the course of olfactory aversive learning. However, the two forms of consolidated memory were negatively correlated among replicate high-learning lines, which is consistent with a recent hypothesis that these two forms of consolidated memory are antagonistic.
Mery
Frederic
F
Department of Biology, University of Fribourg, Chemin du Musee 10, CH-1700 Fribourg, Switzerland.
Pont
Juliette
J
Preat
Thomas
T
Kawecki
Tadeusz J
TJ
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D005075:Biological Evolution; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D005260:Female; D014644:Genetic Variation / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology*; D009812:Odorants; D012641:Selection, Genetic