Genetic variation in associative learning ability of Drosophila melanogaster larvae. Seana Lymer, Julia Saltz, Sergey Nuzhdin. University of Southern California, Los Angeles, CA.

   Social learning requires the integration of associative learning, memory and social behavior (LMS), and these vary considerably among individuals within a species. Genetic differences cause alterations in neural functions that ultimately cause variability in social learning, but the genes and neural circuits that play a role in LMS are not fully understood. Here, we use Drosophila melanogaster to find the range of LMS variation in a number of natural populations. Third-instar Drosophila larvae were screened for learning and memory ability using associative conditioning. Pools of larvae were exposed simultaneously to a mild electric shock and a specific smell, training the larvae to avoid that smell. Memory for avoidance behavior was tested at short-, medium-, and long-term delays, as different neural substrates may be responsible for these types of memory. In our heterozygous populations, the larvae show genetic variation in associative learning for all memory types. While some genotypes show a robust memory in all conditions, other genotypes show memory decay over time. By combining phenotypic screens representing natural variation in larval learning ability with molecular-genetic techniques examining the mushroom body, we can identify how genetic variation is functionally responsible for individual differences in LMS.