The approximately 1600 lexA driver lines in this collection were constructed using the methods described in Pfeiffer B.D., T.B. Ngo, K.L. Hibbard, C. Murphy, A. Jenett, J.W. Truman and G.M. Rubin, 2010. Refinement of Tools for Targeted Gene Expression in Drosophila. Genetics. 2010 186:735-755 . These lines express lexA under the control of defined sequence fragments from either flanking non-coding or intronic regions of associated genes. In general, these sequence fragments were previously used to make the GMR_Brain_exp_1 collection of GAL4 driver lines (FBlc0000201, aka the Rubin or Janelia GAL4 collection). However, it is important to note that most of the lexA lines have been inserted into attP40 (at 25C7 on 2L) by site-specific recombination, while the GAL4 lines are in attP2 (at 68A4 on 3L). This was done to avoid the possibility of transvection in double label experiments, but genomic position effects differ between these sites and frequently result in significant differences in the observed lexA and GAL4 expression patterns; generally the lexA patterns are a subset of the GAL4 pattern. Heather Dionne in the Rubin laboratory at Janelia Farm was the lead individual in constructing the lines, Genetic Services Inc. and BestGene performed embryo injections, and the Janelia Farm Fly Facility (managed by Todd Laverty) generated the homozygous (or balanced) stocks. Additional individuals who contributed to this work include: Rubin Lab: Teri Ngo, Chris Murphy, Barret Pfeiffer, Arnim Jenett and Aljoscha Nern. Janelia Farm Fly Facility: Karen Hibbard, Amanda Cavallaro, Don Hall, Monti Mercer, Grace Zheng, Dona Fetter, James McMahon, Jui-Chun Kao and Danielle Ruiz. Genetic Services, Inc: Susan Zusman. Janelia Farm Scientific Computing Group: Rob Svirskas.