Scientists have found a surprising possible explanation for the way that our human brain stores long-term memories, by reasearch with yeast and sea slugs. Sea slugs have an unusual protein, existing in two shapes. One shape of the protein is slack, and the second shape perpetuates itself indefinitely, but it can also switch back to the sluggish mode without a problem.
The scientists think that in higher organisms like humans the same proteins may use the second state of this protein to store longterm memories, referred to as synapses.
Surprisingly, the shape-shifting protein in yeast and slugs has all the hallmarks of another protein, the infamous prion, found in humans and other animals.
Such prions also assume two shapes. One serves a normal function in the brain. The second sets into motion a runaway process that converts normal prions into a toxic form. As a result, deadly clumps of protein leave holes in the brain and cause disorders like mad cow disease.
The disease-causing prion and the memory-storage protein are not identical, said Eric Kandel, a neuroscientist at Columbia Uni-versity who shared the 2000 Nobel Prize in Physiology or Medicine for his research on memory formation. But they share attributes that make prion-like behavior a perfect mechanism for storing memories.
With experience and learning, new synapses are formed and others are strengthened, Kandel said. Indeed, mechanisms determining short- and long-term memories are formed have largely been worked out. But questions of how long-term memories are actually stored and what keeps synapses from losing their connectivity under the onslaught of cellular remodeling are outstanding mysteries in biology.