“There are a lot of changes that happen at organ or body scale, over hours to weeks, which cannot be tracked over time,” says Edward Boyden, the Y. Eva Tan Professor in Neurotechnology, a professor of biological engineering and brain and cognitive sciences at MIT, a Howard Hughes Medical Institute investigator, and a member of MIT’s McGovern Institute for Brain Research and Koch Institute for Integrative Cancer Research.If the technique could be extended to work over longer time periods, it could also be used to study processes such as aging and disease progression, the researchers say.“It’s not only a snapshot in time, but also records past history, just like how tree rings can permanently store information over time as the wood grows.”Recording eventsIn this study, the researchers first used their system to record activation of c-fos in neurons growing in a lab dish.To explore whether this approach could work in the brains of animals, the researchers programmed brain cells of mice to generate protein chains that would reveal when the animals were exposed to a particular drug.The researchers designed their system to be modular, so that different epitope tags can be swapped in, or different types of cellular events can be detected, including, in principle, cell division or activation of enzymes called protein kinases, which help control many cellular pathways."