This is a coming-of-age story — involving your brain.
That’s how W.A. Harris opened his virtual Harvard Science Book Talk on Monday. The talk, presented by the University’s Division of Science, Cabot Science Library, and Harvard Book Store, brought Harris together with old friend Joshua Sanes, the Jeff C. Tarr Professor of Molecular and Cellular Biology at Harvard and director of the Center for Brain Science. The neuroscientists discussed Harris’ new book, “Zero to Birth: How the Human Brain Is Built,” which elucidates how one cell develops into the complex operational centers that not only make us human, but also individuals, with entirely unique traits, behaviors, and, yes, malfunctions.
Harris presented the relevant evolutionary history, crediting the many pioneering neuroscientists who uncovered how the “Adams and Eves of our brains” were born. One, Santiago Ramón y Cajal, created the first drawings of intricate neuron trees, which are still widely studied. Another, Conrad Hal Waddington, likened the development of different neuron types to a ball rolling down an uneven hill.
“The neural stem cells are a bit unpredictable,” Harris explained. “We can’t predict exactly where they’ll land, but they will create the right amount of neuron types.”
Other 20th-century neuroscientists, including Roger Sperry, took a more hands-on approach, Harris said. Sperry removed, flipped, and reinserted a frog’s eye, leaving the amphibian with an upside-down world. And while the neurons adapted, rewiring to restore vision, the eye was not so nimble. To look up, the frog looked down — for the rest of its life.
Moving from amphibian to mammal, David Hubel and Torsten Wiesel deprived a kitten of vision in one eye to see how the limitation might affect a growing brain. When they restored vision after the kitten reached 3 months old, the duo discovered that the animal never gained sight in the closed eye.