Scientists from the Zilkha Neurogenetic Institute and Keck School of Medicine said they are the first to develop a functional approach to studying neural circuitry in the earliest possible developmental stages through their research conducted on zebrafish.

Their study was published in the April 6 issue of the Journal of Neuroscience, the weekly journal of the Society for Neuroscience. It finds that during very early development of the brain there is a period when exuberant neural connections are being refined, leading to precisely connected neural circuits in the mature brain.

“Our findings lay a very solid basis for the view of early development of the neural connectivity. The time window when imprecise neural connectivity is being refined provides the brain circuit with an opportunity to be adapted to the specific sensory environment.” said Huizhong Tao, assistant professor of cell and neurobiology.

Previous studies on birds implied that a pruning of neural connections may occur. The current study, using a functional approach, provides direct evidence for a refinement of neural connections.

Additionally, the current study examined much earlier developmental stages than the previous studies, with stages as early as only four days after fertilization of zebrafish eggs.

The research has implications for the impact of some disease-related genes, such as the gene responsible for the fragile-X form of mental retardation, on the early development of brain circuits.

The study’s other USC researchers are Min Zhang and Yan Liu, postdoctoral research scientists at the Zilkha Institute, and Sheng-zhi Wang and Bao-hua Liu, graduate students at the Keck School. The final team member, Wen Zhong, is a researcher from Guang Dong Provincial Hospital of Traditional Chinese Medicine in Guangzhou, China.

The study was supported by the National Eye Institute and the Karl Kirchgessner Foundation.