mice, he observed that genes in the mature B cells of the adult mice are moved around, recombined, and deleted to form the diversity of the variable region of antibodies. This process is known as V(D)J recombination. In 1983, Tonegawa also discovered a transcriptional enhancer element associated with antibody gene complex, the first cellular enhancer element. Neuroscience Shortly following his Nobel Prize in 1990, Tonegawa again changed fields from immunology to neuroscience, where he has focused his research in the ensuing years. Tonegawa's lab pioneered introductory transgenic and gene-knockout technologies in mammalian systems. He was involved in early work demonstrating the importance of CaMKII- (1992) and the NMDA receptor-dependent synaptic plasticity (1996) in memory formation. Tonegawa's lab discovered that dendritic neuronal spines in the temporal cortex are a likely target for treatment of Fragile X Syndrome. With one dosage of the inhibitor drug FRAX586, Tonegawa showed a marked reduction of FXS symptoms in the mouse model. Tonegawa was an early adopter of optogenetics and biotechnology in neuroscience research, leading to his groundbreaking work identifying and manipulating memory engram cells. In 2012, his lab demonstrated that the activation of a specific sub-population of mouse hippocampal neurons, labelled during a fear conditioning paradigm, is sufficient to evoke a behavioral response correlated with a precise memory trace. This demonstrated for the first time that memory information is stored in specific cellular ensembles in the hippocampus, now frequently called memory engram cells. More recently, his lab continues to employ optogenetic technology and virus injection techniques to expand their findings on the engram cell ensemble. Notably, Tonegawa has uncovered the role of memory engram cell ensembles in memory valence, social memory, as well as their role in brain disorders such as depression, amnesia, and Alzheimer's disease. These works provide proofs of concept for future medical treatments in humans through the manipulation of memory engram ensembles. Personal life Tonegawa currently resides in the Boston area with his wife, Mayumi Yoshinari Tonegawa, who worked as an NHK (Japan Broadcasting Corporation) director/interviewer and is now a freelance science writer. The Tonegawas have three children, Hidde Tonegawa, Hanna Tonegawa, and Satto Tonegawa (deceased). Tonegawa is a fan of the Boston Red Sox, and threw out an opening pitch during their 2004 World Series championship season. Selected awards and honors 1982 – Louisa Gross Horwitz Prize 1983 – Gairdner Foundation International Award 1984 – Order of Culture (Bunkakunsho), Emperor of