© Sven HuathTRACES OF MEMORY New technologies and new ideas have revived the hunt for the physical basis of memory, challenging existing notions of where memories are stored.
People tend to think of memories as deeply personal, ephemeral possessions - snippets of emotions, words, colors and smells stitched into our unique neural tapestries as life goes on. But a strange series of experiments conducted decades ago offered a different, more tangible perspective. The mind-bending results have gained unexpected support from recent studies.
In 1959, James Vernon McConnell, a psychologist at the University of Michigan in Ann Arbor,
painstakingly trained small flatworms called planarians to associate a shock with a light. The worms remembered this lesson, later contracting their bodies in response to the light.
One weird and wonderful thing about planarians is that they can regenerate their bodies - including their brains. When the trained flatworms were cut in half, they regrew either a head or a tail, depending on which piece had been lost. Not surprisingly, worms that kept their heads and regrew tails retained the memory of the shock, McConnell found. Astonishingly, so did the worms that grew replacement heads and brains. Somehow, these fully operational, complex arrangements of brand-spanking-new nerve cells had acquired the memory of the painful shock, McConnell reported.
In subsequent experiments, McConnell went even further,
attempting to transfer memory from one worm to another. He tried grafting the head of a trained worm onto the tail of an untrained worm, but he couldn't get the head to stick. He injected trained planarian slurry into untrained worms, but the recipients often exploded. Finally, he ground up bits of the trained planarians and fed them to untrained worms. Sure enough, after their meal, the untrained worms seemed to have traces of the memory - the cannibals recoiled at the light.
Comment: It would be interesting to know how the scientists determined the cave has been used by the hammerheads for a million years...