Biomedical subjects

Frederic Mery

Publications and source records attributed to Frederic Mery.

5 recordsLinked to original sources

PubMed2006

Aging and its differential effects on consolidated memory forms in Drosophila.

Aging is known to be associated with a decrease of learning and memory. Little is known on the specificity of this process. In Drosophila, two forms of consolidated memory have been observed. Anesthesia-resistant memory (ARM) is formed after one or several consecutive training sessions whereas long-term memory (LTM) is formed only after multiple training sessions separated in time. Both memory forms last more than 24 h. In the present experiment I, address the question of the effect of aging on the formation of each memory form. Twenty four hours after being conditioned, old flies show similar ARM as young flies but LTM was completely abolished. Age memory impairment seems therefore to be specific to one consolidated memory form.

Aging↗

PubMed2005

A cost of long-term memory in Drosophila.

Two distinct forms of consolidated associative memory are known in Drosophila: long-term memory and so-called anesthesia-resistant memory. Long-term memory is more stable, but unlike anesthesia-resistant memory, its formation requires protein synthesis. We show that flies induced to form long-term memory become more susceptible to extreme stress (such as desiccation). In contrast, induction of anesthesia-resistant memory had no detectable effect on desiccation resistance. This finding may help to explain why evolution has maintained anesthesia-resistant memory as another form of consolidated memory, distinct from long-term memory.

Animals↗

PubMed2004

The effect of learning on experimental evolution of resource preference in Drosophila melanogaster.

Learning is thought to be adaptive in variable environments, whereas constant, predictable environments are supposed to favor unconditional, genetically fixed responses. A dichotomous view of behavior as either learned or innate ignores a potential evolutionary interaction between the learned and innate components of a behavioral response. We addressed this interaction in the context of oviposition substrate choice in Drosophila melanogaster, asking two main questions. First, will learning also evolve in a constant environment in which it always pays to show the same choice? Second, how does an opportunity to learn affect the evolution of the innate (genetic) component of oviposition substrate choice? We exposed experimental populations to four selection regimes, involving selection on oviposition substrate preference (an orange versus a pineapple medium). In two selection regimes the flies were selected for preference either for the orange medium, or for the pineapple medium. In the remaining two selection regimes the flies were also selected for preference for either orange or pineapple, but additionally could use past experience (aversion learning) to decide which medium it paid to avoid. Lines exposed to the latter selection regimes evolved improved learning ability, indicating that learning may be advantageous even if the same behavioral response is favored every generation. Furthermore, of the two selection regimes that favored oviposition on the pineapple medium, the regime that allowed for learning led to the evolution of a stronger innate preference for pineapple, than the regime that did not allow for learning. In contrast, of the two regimes that selected for oviposition on the orange medium, the one that allowed for learning led to a smaller evolutionary change of the innate preference. Thus, an opportunity to learn facilitated the evolution of innate preference under selection for preference for pineapple, but hindered it under selection for preference for orange. We discuss possible mechanisms for this effect.

Analysis of Variance↗

PubMed2003

A fitness cost of learning ability in Drosophila melanogaster.

Maintenance of substantial genetic variation for learning ability in many animal populations suggests that learning ability has fitness costs, but there is little empirical evidence for them. In this paper, we demonstrate an evolutionary trade-off between learning ability and competitive ability in Drosophila melanogaster. We show that the evolution of an improved learning ability in replicated experimental fly populations has been consistently associated with a decline of larval competitive ability, compared with replicated control populations. The competitive ability was not affected by crossing of the replicate populations within each selection regime, excluding differential inbreeding as a potential confounding factor. Our results provide evidence for a constitutive fitness cost of learning ability, i.e. one that is paid irrespective of whether or not the learning ability is actually used.

Animals↗

PubMed2002

Experimental evolution of learning ability in fruit flies.

The presence of genetic variation for learning ability in animals opens the way for experiments asking how and under what ecological circumstances improved learning ability should evolve. Here we report experimental evolution of learning ability in Drosophila melanogaster. We exposed experimental populations for 51 generations to conditions that we expected to favor associative learning with regard to oviposition substrate choice. Flies that learned to associate a chemical cue (quinine) with a particular substrate, and still avoided this substrate several hours after the cue had been removed, were expected to contribute more alleles to the next generation. From about generation 15 on, the experimental populations showed marked ability to avoid oviposition substrates that several hours earlier had contained the chemical cue. The improved response to conditioning was also expressed when the flies were faced with a choice of novel media. We demonstrate that these behavioral changes are caused by the evolution of both a higher learning rate and a better memory.

Animals↗