Nedivi’s first experiments focused on mice living a standard lab life, but now that she and her team have defined the normal amount of adult neural plasticity, they can examine how different environmental or genetic factors affect the growth of the brain. Previous research, for example, showed that giving young rodents toys or raising them in a varied landscape spurs the birth of new brain cells. Two-photon imaging will allow researchers to explore how living in a complex environment influences the neural organization of the brain. Lee has recently started studying how visual deprivation affects neural plasticity in the visual cortex. These projects will help researchers figure out whether different environments make the animals’ neurons grow more rapidly or rearrange more frequently, and whether those changes eventually lead to differences in behavior.
Meanwhile, Nedivi says, she has been flooded with requests from scientists studying diseases such as Alzheimer’s and schizophrenia. “Once we characterize the problem with each different disease–maybe fewer projections are growing or only a certain kind of neuron is affected–then we can tailor treatments to that problem,” she says. “We could also use this technology as a platform to screen for therapies.”
Of course, each experiment will require months at the microscope. It takes hours to image each neuron, and days to construct a three-dimensional model from the two-dimensional images. In addition, scientists will need to meticulously compare neurons from many animals to get a sense of the differences between the behavior of diseased cells and that of healthy ones. Unfortunately, time is something Nedivi currently does not have; the lab uses a customized microscope in So’s lab. Once a week, her students box up their mice and take them to the lab, imaging as many neurons as time allows. Soon Nedivi hopes to get the $500,000 necessary to set up an instrument in her own lab, which would give her researchers unlimited time to watch the brain in action.