The challenge that occupied me throughout my career is how the most complicated object in the known world, the brain, is built. I started investigating neural development when I was a graduate student at Caltech (1972-1976) and I discovered genes that were involved in building the eye. As a postdoctoral fellow at Harvard Medical School (1976-1980), I began investigating the role of activity patterns in the brain in the formations of synaptic connections. I landed my first academic job at the University of California San Diego in 1980, where I worked on questions concerning how neurons send out long processes called axons that navigate through the embryonic brain to find their synaptic targets. In 1997, I moved to Cambridge. Here, I was particularly fascinated by questions of how the neurons in the brain choose their individual and cell-specific fates.
During my career, I have had the pleasure of collaborating with many wonderful scientists here and around the world. After I retired from laboratory work, I wrote a popular science book about neural development called Zero to Birth: How the Human Brain is Built. I still enjoy supervising students studying Neurobiology at Clare College.