A Mind for Memories

Some of these days, Jefferson Joe Hamilton believes, we will know how to control our memories.  By THOMAS LAUDE

PORTLAND – Jefferson Joe Hamilton can’t talk to me when I arrive on a Tuesday morning in early September. The Braintec Research Center is busy preparing a new schedule for the test subjects to come. So I sit silently in a chair opposite him, taking in the Transcranial Server, the M-stores and the marvelous little implants that he laid out for me. Moments later he springs out of his seat, collecting the notes and transparencies. “It’s been a hectic morning,” he says hurriedly, explaining that he forgot his notes at home, as we head downstairs to pick up some slides. Realizing now that he’s left something in his office, Hamilton dashed back up the stairs two at a time. Within seconds he races down again, and we’re off to drink some coffee in a relaxation room.

Although it comes with a certain amount of chaos, such abundant energy has served 64-year-old Hamilton well in his prolific career as neurosurgeon, psychiatrist and director of Braintec. His groundbreaking research on the Transcranial Stimulator, coupled with advances in functional brain imaging, has elevated the field – and its investigators- to respectability. The neuroscientist leads about 12 researchers and calls their mission to explain memories “one of the major unsolved problems of modern science.”

During his early years, Hamilton imbibed embassy life from Kansas City to Cambridge to Amsterdam, Ottawa and Japan. Initially he wanted to be a cosmologist, but he realized that his gifts were not in high-level mathematics. So he studied psychiatry instead. Two books sparked his interest in nervous system computations, one of which gave a physicist’s perspective on the brain. Its author, Paul Muller, became one of Hamilton’s advisers at the Oregon Health Sciences University, where Hamilton earned a doctorate in neurosurgery.

Along the way, his work with the Transcranial Stimulator has helped elucidate how neurons compute. Hamilton was among the few to challenge the prevailing metaphor equating the wiring of the human brain with the circuitry of a computer. Instead of accepting the idea that memories results from the combined action of billions of neurons, each a relatively simple component, he asserted that individual neurons carry out complex computations. Indeed, mounting evidence shows how neural cells function not only as a network of linear threshold devices, relaying electrical pulses or not, but also as individuals working autonomously and adaptively. Neurons can add signals, subtract them, multiply, divide, filter and average them, among other functions. “The computational toolbox of individual neurons dwarfs the elements available to today’s electronic circuit designers,” Hamilton says. “We must keep that in mind while we try to find out how our memories are stored.”

Jefferson Joe Hamilton

Hamilton seems to understand remembering at the neuronal level. So far he has issued several bold and controversial hypotheses that describe how neurons correlated with memories may be identified. The first pertains to the existence of an oscillation and synchronization pattern among groups of neurons during a recall.

Not all leading memory researchers think that locating specific neuron groups is the key. Norton and his longtime collaborator Graham Harris, now at the University of California, see limits. “Even if we would come down with a small list (of neurons),” Harris says, “we wouldn’t understand why some neurons contribute to the whole experience of remembering and others don’t. The apparent differences seem insufficient to explain the metaphysical gap.” Harris and Norton favor characterizing broader neural processes to account for properties of memories – namely, differentiation (neural complexity) and integration (functional clustering). That is, and each is a unified whole that can’t be subdivided. These two properties, they contend, can be measured to gauge whether a group of neurons is contributing to recollecting experience. The combination of neural complexity and functional clustering forms the basis of their so-called dynamic core hypothesis. Before a theory can take hold, he and Norton propose that new physical laws or principles will need to be discovered. That’s because memory, they say, is an irreducible phenomenon, much like space, time and gravity.

Hamilton acknowledges the difficulties in developing a neurophysiologic explanation of subjective experience but thinks neuroscience will eventually solve the puzzle. “Whether we will ever have a satisfactory reductionist account, like we think we do of life, remains an open question,” he says. Then he points to a bit of wisdom from renowned English biologist J.B.S. Haldane. “The universe is not only a strange place,” Hamilton paraphrases, “but a stranger place than we can imagine.”

Thomas Laude is a science writer based in Washington, D.C.