I build AI that doesn’t just predict, but explains how complex
physical and biological systems actually work.
As the brain works, the blood flowing through it changes its magnetism by a
hair. An MRI scanner can follow that change across the whole cortex, and from the pattern
it records we can now tell what a person is listening to, and something of what they are
imagining. A thought, in other words, can be read from the magnetism of blood.
Underneath that fact lies the question that first drew me to science. Atoms are cold,
interchangeable, and indifferent; yet from assemblies of them arise cells, sentences, and
the minds that read them. How that happens, how meaning arises from matter, has been my
question ever since. It took me, after two years in the business school at Peking
University, to philosophy and physics at Vanderbilt; then to the physics of living matter
in Vijay Balasubramanian’s laboratory at the University of Pennsylvania; and finally
to the biophysics program at UC Berkeley, where I joined Jack Gallant’s lab and
found a second intellectual home at the Redwood Center for Theoretical Neuroscience with
Bruno Olshausen, who later served on my thesis committee.
At Berkeley the question became an empirical one, and that scanner was the instrument.
Its recordings are noisy, high-dimensional, and only indirectly related to the activity
of neurons; the method for reading them came from the Redwood Center: sparse coding,
which assigns each learned axis a single meaning. With it, I used machine learning to
decipher how abstract concepts such as number, space, and time are represented across the
human cortex. A second project reversed the direction: drawing on the understanding such
models provide, we built closed-loop deep brain stimulation that decodes a patient’s
movement from the brain itself and adjusts therapy for Parkinson’s disease in real
time.
Both projects point to the same conclusion. The principal constraint on scientific
progress is seldom the quality of our models. We consistently overestimate our own
ingenuity: the hypotheses we are able to write down form a measure-zero subset of what is
possible, and genuine progress has come, far more often than from new ideas, from new and
better measurements made in the environments where the systems of interest actually
operate. This is a hopeful conclusion, because instruments can be built. That is what
Erised is for: an understanding of the world at its smallest scales is more than a
technical milestone; it is a means to help the world, and the living things in it.