Charles "Chuck" Stevens

Charles F. (Chuck) Stevens of the Salk Institute, Molecular Neurobiology Laboratory worked developing physics-style theories in biology. Stevens attended the Aspen Center for Physics from 1988 on, was member since 1998, and a trustee from 2001 to 2007. 

Charles F. “Chuck” Stevens (September 1, 1934 – October 21, 2022) was an American neurobiologist at the Salk Institute in La Jolla. He was the Vincent J. Coates Professor at the Salk Institute for Biological Studies and adjunct professor of pharmacology and neuroscience at UCSD’s School of Medicine. He was also an external professor and member of the science board at the Santa Fe Institute. Stevens came to the Aspen Center for Physics for the first time in 1988, was a General Member from 1998 – 2018, and a trustee from 2001 to 2007. Stevens was Chair of the Board at ACP from 2012-2015.

Stevens made several seminal discoveries regarding the molecular basis of synaptic transmission. In 2002, together with Dmitri Chklovskii, Stevens described the “3/5 Power Scaling law of neural circuits.” Stevens and Anderson used noise analysis to infer the conductance of single acetylcholine ion channels. This work paved the way for Nobel laureate Erwin Neher’s patch clamping techniques. Neher was a postdoctoral associate with Stevens at the University of Washington and then Yale University.

Stevens has a B.A. in psychology from Harvard University, where he began his education hoping to be a physician. He then received an M.D. degree at Yale University, and a Ph.D. in biophysics from Rockefeller University with Haldan Keffer Hartline. He was a member of the faculties at the University of Washington Medical School and at Yale Medical School before joining the Salk Institute.

Stevens was elected member to the National Academy of Sciences in 1982, and he was formerly an investigator of the Howard Hughes Medical Institute. He was elected a Fellow of the American Academy of Arts and Sciences in 1984. In 2000 he was awarded the NAS Award for Scientific Reviewing from the National Academy of Sciences.

Stevens says of his work, “I try to identify something that a biological system has to do, something that has to be true for the system to work. For example, in the eye there are nerve cells that send information to the brain with nerve impulses. The cells that send this information to the brain work like pixels in a digital camera and each one collects information about a tiny part of the images in the eye. How big should the pixel be? It needs to be as small as possible to get good resolution (like a 4 megapixel camera), but if it is too small, the light intensity that pixel reports to the brain is noisy and so the brain doesn’t get a good image. The problem in cameras is the same as in the eye. How does the brain deal with this? What physical principles operate to dictate the perfect pixel size for the eye of every organism? That is a question that can be tested because we understand the principles that determine the eye’s resolution and how much noise is in the image.

Another example of a physics-style biological problem is in looking at the division between ‘wire’ and ‘non-wire’ in the brain. ‘Wire’ are parts of nerve cells that send information over large distances in the brain, and ‘non-wire’ is everything else, like the special cells in between nerve cells that are the brain’s ‘packing peanuts’.  A physics-style theory tells us that the ‘wire’ takes up 3/5 of the brain volume – and it turns out that this has to be true if the brain is to work well. Researchers are now trying to figure out how, developmentally, brains manage to do that.

This is a piece of understanding the scalable architecture of the brain. All brains work about the same way. The difference between a mouse and an elephant brain is basically size: bigger body, bigger muscles, bigger eyes. But what principles enable the brain to have scalable architecture so its brain can deal effectively with a bigger body and its bigger parts? When this is understood, we know we can apply the principles to computer design but we have no idea where else this knowledge will be applied.”

Stevens concludes, “Of course, the main interest of the public is in applying biophysics to curing diseases. But the basic research must come first. Watson and Crick were doing basic research when they uncovered DNA sequencing. Only 50 years later, their basic research is impacting medicine and agriculture. Basic research will come first and then will come innovations in energy, in adapting to and controlling climate change, in new areas not yet anticipated. But first, the basic research must be done and that is the work of theoretical physicists.”