The highlights, for me, of my scientific career are of the science are directly related to my work at Cold Spring Harbor. To have the opportunity to get your hands on a new technology at its outset is just extraordinary. So, using monoclonal antibodies, I was able to understand the organization of the brain. I think deeply a cell biologist, not a system biologist. And one of the extraordinary things about the brain is that we're born with all the brain cells we'll ever have, but the connections between those cells, the circuitry of the brain develops over the course of early life. And so, we watch babies learn to walk, we will watch them learn to manipulate objects. Well, all of these things have to do with the circuits actually being connected, the wiring being laid down and selected. And what we've learned is there are critical periods in development where early on the connections are malleable, they can be changed.

But once you get to what we call a critical period, changes are not possible. One example, if a child has an eye that deviates as a lazy eye or a sleepy eye, the brain will only process one visual signal. And so, the eye that is making sense in the world, connections to the brain are made normally and the other set of signals coming from the deviating eye are suppressed, and that eye eventually becomes functionally blind. If you recognize that that's happening early on. This is for kids by six years of age, five years of age, you can patch the good eye and force the bad eye to see, thereby recovering in a stabilizing vision in the eye. Beyond seven or eight years, you can't do it. An even better example is language acquisition. So, we acquire language, the language of our environment, and you acquire that in a way that you have for your life.

If you learn languages before, another language, roughly before puberty, you can learn another language without an accent. But if you learned it after puberty, it's very hard. We have many of examples of how people are masters of the language theoretically, but in terms of producing language, they're still fettered by an accent so this is a very interesting transition in the brain from being young and plastic and malleable to being adult and fixed. Hubel and Wiesel did brilliant studies on visual system development, looking at how long, when, why, it becomes fixed. And they had established that in cats at a particular time in life, three months of age, the visual connections are stabilized, before that you can move them around. We'd do these basically experiments, changing the input to the brain. And one of the antibodies that I generated not for this purpose, ended up, ends up to be a marker for the closing of critical periods. And I did a series of experiments with marvelous colleagues, Marc A. Kastner, Doug Frost, Hubel and Wiesel, demonstrating that this particular molecule, which I went on to identify the specifics, are kind of beyond most of the audience, but it's an extracellular molecule that decorates the synapses on a neuron it is first expressed at the close of critical periods and basically behaves the way critical periods we know critical periods do to behave. So that was, I would think, the first evidence of first identification of a critical period molecule.

Susan Hockfield is a neuroscientist whose research focuses on brain development and glioma, pioneering the use of monoclonal antibody technology demonstrating that early experience results in lasting changes in the molecular structure of the brain. She is a Professor of Neuroscience and President Emerita at MIT. She was the first woman and life scientist to serve as MIT’s sixteenth president from 2004-2012.

Hockfield earned her B.A. in biology from the University of Rochester (1973) and a Ph.D. from Georgetown University at the School of Medicine (1979). In 1980, Hockfield completed an NIH postdoctoral fellowship at the University of California at San Francisco. She then joined the scientific staff at the Cold Spring Harbor Laboratory, New York where she ran her own lab for five years. She also served as director of the Summer Neurobiology Program from 1985 to 1997. In 1985, Hockfield became the William Edward Gilbert Professor of Neurobiology at Yale University. She went on to serve as the Dean of the Graduate School of Arts and Sciences from 1998-2002, and Provost from 2003-2004.

In December 2004, Hockfield assumed office as the president of the Massachusetts Institute of Technology. She held this role until June 2012 and continues to hold a faculty appointment as professor of neuroscience and as a member of the Koch Institute for Integrative Cancer Research.

Hockfield has received numerous awards including the Charles Judson Herrick Award from the American Association of Anatomists, the Wilbur Lucius Cross Award from the Yale University Graduate School, the Meliora Citation from the University of Rochester, the Amelia Earhart Award from the Women’s Union, and the Yale Science and Engineering Association 2021 Award for Distinguished Service to Industry, Commerce or Education.

She also holds honorary degrees from Brown University, Duke University, Georgetown University, Mt. Sinai School of Medicine, New York University, Northeastern University, Tsinghua University (Beijing), Université Pierre et Marie Curie, University of Edinburgh, University of Massachusetts Medical School, University of Rochester, and the Cold Spring Harbor Laboratory School of Biological Sciences.