“In a sleepless hour of the night, I was trying to remember the last name of a person I have known well for more than forty years. When my spouse stirred in her sleep, I asked her. She couldn't remember either. One again I started mentally through the alphabet. "I think it starts with B," I said. Ten minutes later she rolled over and said, "The next letter is R." Bingo! The name popped into my head. Or I should say, "popped out of my head." Because it was in there somewhere, recorded in a tangle of neurons as materially as if it were written on a piece of paper.
There was a time, back when I was a young man, when some scientists thought memory might be molecular - stored as proteins or RNA molecules that have somehow been modified by experience. The molecule theory of memory rested on experiments with worms (I remember the cover illustration on Scientific American). The worms were taught to navigate a simple maze. Then they were ground up and fed to untrained worms, which seemed to navigate the maze without training. Only molecules, it was thought, could have survived the transfer. Those experiments have been discredited. Scientists now overwhelmingly believe that memories are stored as webs of connections between spider-shaped brain cells called neurons. Each neuron is connected through electrochemical connections to thousands of others. According to the current view, experience fine-tunes the connections, strengthening some, weakening others, creating a different "trace" of interconnected cells for each memory.
But truth be told, memory is still deeply mysterious. How exactly are a lifetime of memories stored and retrieved at will? We know how it works for computers, but how for the human brain? What is self-consciousness? What are dreams? This is the primary scientific agenda for the 21st century. In the middle of the night I go fishing, in that sea of potentiated synapses that are the human soul, for a name that becomes ever more difficult to extract as I get older. I troll the alphabet: A, B, C, D… The name is in there, along with a face and more that fifty years of interactions. The Nobel Prizes are waiting.”