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Neural tube defects (NTDs) and other aspects of nervous system development are modeled in two species of frog: Xenopus laevis and Xenopus tropicalis.  These frogs are native to Southern Africa and Western Africa, resepectively, but have been a popular model organism in the scientific community since World War II.  These species are well-suited for scientific studies because of their advantageous reproductive qualities, have large, easily manipulated eggs and embryos, and are low-maintenance and cost-effective.  Over the years, the results from studies in Xenopus have helped us understand fundamental events and cues that are required for normal nervous system development in vertebrates.  Frogs are obviously very different from humans so these organisms help us understand generalities about nervous system development, regeneration, and function.  More complicated or detailed studies on NTDs, like spina bifida, are modeled in higher vertebrates with anatomy that is more similar to humans.

References:

Gurdon, John B., and Nick Hopwood. “The introduction of Xenopus laevis into developmental biology: of empire, pregnancy testing and ribosomal genes.” International Journal of Developmental Biology 44.1 (2003): 43-50.