Dangerous assumptions in neuroscience
By Robert G. Shulman
I’ve spent decades in magnetic resonance research and since 1980 my colleagues and I have been studying the human brain. Like many fields of science, it is astounding to reflect on the progress made in the uses of magnetic resonance which has gone from being a physicist’s means of studying the nucleus to an omnipresent tool for clinical medicine and biological research, especially in neuroscience. Our society holds great hopes for brain research. The Obama administration recently announced a “Brain Activity Map” project that would seek “to advance the knowledge of the brain’s billions of neurons and gain greater insights into perception, actions, and ultimately, consciousness.” However, the work that my colleagues and I have done to understand brain metabolism and function argues that some of the enthusiasm shown for these methods needs a fundamental re-examination.
In essence, I have seen too much scientific work that starts with assumptions that we know and have a solid and consensus-driven understanding of concepts like memory or consciousness when in fact we do not and cannot. Countless tests of “memory” that track activated areas of the brain via fMRI have abandoned scientific observation and induction in favor of a priori assumptions about words or ideas that have value during common usage but are not empirical concepts. What we now know about consciousness from brain imaging is that certain measurable brain properties, such as the total neuronal energy consumption, are necessary for the person to be in the state of consciousness as defined by the anesthesiologist during surgery. As more properties, including brain activities, necessary for a person to be in the state of consciousness are uncovered, the better we will understand it, but we will not get there by trying to define that elusive intangible called consciousness.
While there are marvelous results to be gained from careful research on brain metabolism and blood flow as measured by fMRI, there is little to be gained by making assumptions about the human mind. We shouldn’t leap from early but exciting understanding of brain activities necessary for a person’s behavior to assumptions about mental processes presumed to underlie those behaviors. Once we are trained to do things reproducibly — like recognizing a face or avoiding a moving automobile — brain activity supports our response. While we (as scientists) know a lot about how the muscle receives electrical impulses, we would never assert that the biceps, triceps, and deltoids lift a bride over the threshold after a wedding — the groom does. Even as we learn, with astounding precision, about which areas of the visual cortex are activated when the person learns to differentiate between cars and vases, we should not assume that the brain makes this distinction. It is the person who decides and acts; it is the organ — the muscle or brain — that supports her behavior.
One can postulate many reasons for society’s enthusiasm to translate basic research into useful applications in health and control. Nevertheless, it is dangerous for a subtle collective willingness among research scientists to replace traditional scientific methods that are producing wonderful descriptions of the brain’s support of observable behaviors with claims of having found a physical basis for mental concepts like working memory or attention.
Thomas Nagel’s recent book offers a very clear lens for this approach. He proposes that science has failed as an epistemological method because material science cannot explain the mind. Nagel argues that the mind obviously exists, and since chemistry and physics can’t explain it then science has failed and we must look for alternate epistemologies. I certainly agree that physical science cannot explain mind but I would depart from Nagel’s solution for two important reasons. While he defines physical science as proposing to explain everything, the more realistic and generally held view is that science is capable of understanding some aspects of the world but not necessarily all. We can’t combine the subjective views of the mind held by literature, psychology, philosophy, and everyday life with measurements of neuronal activities to give us a scientific, objective, or complete description of mind. However this is a failing of material science only if one holds a nineteenth century view that material science can explain everything in the world, a view discarded when the limits of classical physics were revealed by quantum mechanics and relativity.
As Neils Bohr succinctly observed “Physics does not tell us what nature is but rather tells us what we can say about nature.”
Robert G. Shulman is a biophysicist who has pioneered the use of nuclear magnetic resonance (NMR) and other spectroscopic techniques in physics, biochemistry, and brain imaging. He is the author of Brain Imaging: What it Can (and Cannot) Tell Us About Consciousness. His original studies created active fields of investigation in all these disciplines. He is the Sterling Professor (Emeritus) of Molecular Biophysics and Biochemistry at Yale University where he formed the Magnetic Resonance Center, taught Biochemistry, Biophysics, and Literature, and was Director of the Division of Biological Sciences. He is a member of the National Academy of Sciences and of the Institute of Medicine.