Making Long-Term Memories Out Of Short-Lived Molecules
If consciousness is what makes us human, memory – it could be argued – is what defines us as individuals. Each of us carries within our brains a unique set of memories that, together, make up our life stories. But how do we remember? That is the question that drives Erin Schuman.
Over the past two centuries, biologists have continuously refined our maps of the brain, adding ever more layers and regions. In the past several decades, neurobiologists have begun to map certain functions to those different regions. Today, major projects in the U.S. and Europe aim to map every cell and connection in the human brain.
Schuman, who is director of the Department of Synaptic Plasticity at the Max Planck Institute for Brain Research, says understanding the brain’s circuitry is essential, but not the end of the story.
“Those connections are fluid, they’re dynamic,” says Schuman. “They can change with experience. They can change when neuromodulators, or different chemicals, are present in the brain. You can dramatically change a circuit.”
For that matter, the proteins that actually make up the connections between nerve cells – and which are known to be crucial in creating memories – are constantly in flux. Each individual protein has to be replaced every few days
That begs the question: How you can store information long-term, when the building blocks of memory are so transient?
Schuman says that, based on the current evidence, she thinks the answer is in the different combinations and configurations of proteins found at synapses, the points where nerve cells connect to one another.
“You can imagine it as sort of like a building, where you have a scaffold at the synapse and you can put different planks - different proteins – in different configurations,” explains Schuman. “The essence of what the synapse does is to pass information. We think that one way information is stored in the brain, is by changing the strength of communication between synapses. And that can be accomplished by changing the complement of proteins.”
But Schuman cautions it’s not as simple as one structure or synapse for each memory. Rather, she says memory is a network phenomenon.
“You have to think about it more as an orchestra, where the flutes come in and they play in different parts but in the end you have an output that is the whole orchestra,” Schuman says. “That could be a perception or a memory.”
Schuman is optimistic that one day, we might be able to reproduce the structure of a given brain (perhaps virtually) and, with the right prompt, replay the memories it encodes. Well before then, understanding which proteins play which roles in memory formation and storage could help treat diseases, like Alzheimer’s. But what really drives Schuman is something more fundamental: she’s just fascinated by figuring out how the brain does what it does.