Memory (i.e. the ability to store and retrieve information) plays a crucial role in the
development of an animal’s behaviour within its lifespan and is often important for its
survival and reproductive success. Memory is itself a product of evolution and the degree to
which information is maintained in the brain varies among species and among different types
of behaviour. Findings from vertebrate behavioural pharmacology have challenged the
traditional view of memory formation as a direct flow from short-term to long-term storage.
Evidence points instead to an intricate, multiphase pathway of memory consolidation.
Different components of memory emerge at different times after the event to be memorized
has taken place. In addition, their duration and times of onset can vary with different tasks and
species.
For most of the 20th century, memory has not figured in "mainstream" evolutionary research.
However, for an evolutionary biologist these findings raise the question of the functional and
evolutionary relationships among, as well as the genetic basis of, these different components
of memory.
The central part of the project is the study of the sources of memory variation. Using
Drosophila as a model system, we investigate how genetic variation, environmental and
developmental factors may affect specifically some memory phases and how these variations
may depend on the type of cognitive task performed by the individual. As an example, we
found that flies artificially selected for improvement of a specific consolidated memory phase
showed a decrease of other memory phases suggesting a potential evolutionary trade off
between the different memory components. Such genetic trade-off may impact on the
evolution of cognitive capacities. Environmental factors are also well known to affect
phenotypic traits. We investigate the effect of social interaction on individual memory
capacities and found that some memory phases were particularly sensitive to the social
environment and this environmental effect was dependent on a mutation at the foraging locus.
Finally, variation in learning and memory are likely to depend on developmental factors. In
human, children born to older parents tend to have lower intelligence and are at higher risk for
disorders such as schizophrenia and autism. Such observations of ageing damage being passed
on from parents to offspring are not often considered within the evolutionary theory of ageing
and explanatory factors are difficult to isolate especially in human. In Drosophila, we
observed a 25% decrease of a specific memory phase due solely to the age of the parents. We
are at present trying to understand the genetic and neural bases of this parental age effect.
To extend these results and understand how the dynamic of the different memory phases may
be sensitive to the type of cognitive task performed, we are currently developing new learning
protocols involving other sensory and neuronal pathways. As an example, we developed a
social learning protocol in which flies have to use public information to choose a suitable
oviposition site. This type of experiment opens new perspectives on the study of the genetic
and neural bases of social learning.
Taken altogether these results suggest a strong interplay of factors to mold the development
and plasticity of the different memory phases. The study of this interplay is fundamental for a
better understanding of the evolution of animal cognition.