PROJECT SUMMARY Sensory experiences during development profoundly influence sensory processing in mature animals. Since most of an animal’s sensory experiences are multimodal, the activity of one sensory modality often causes long-term changes in another modality. Such cross-modal plasticity not only leads to compensation for sensory functions in the case of sensory deprivation, but also allows normal individuals to respond properly to sensory stimuli in their unique habitats or situations and contributes to individual’s differences in the perception of multisensory cues. Despite the importance of cross-modal plasticity, the underlying circuit and molecular mechanisms are poorly understood. The objective of the parent grant R01NS104299 is to identify the mechanisms that underlie cross-modal plasticity in the developing somatosensory system of Drosophila larvae, and provide circuit and molecular models for guiding future studies in other species. The central hypothesis is that gentle mechanosensory inputs during development strengthen serotonergic inhibition of the synaptic transmission from nociceptors to multisensory second-order neurons (MSONs), which is achieved through specific genes in the MSONs. The requested Research Supplement to Promote Diversity in Health-Related Research will support the training of an outstanding postbaccalaureate. The research proposed will supplement the originally proposed studies to ensure the successful attainment of its aims. Two studies are proposed to supplement the original Aim 2: (1) determine whether FMRP is required for cross-model behavioral plasticity; and (2) determine whether cross-modal plasticity affects neural ensemble activities. These research activities will expand the research experiences of the supplementee. Moreover, they will provide opportunities for her to learn scientific writing, oral presentation skills, and networking. These training will position her strongly for a health-related research career.