Do you remember the first time you went through a romantic breakup? Maybe you have vivid memories of your wedding day. How about the address of your first home or your first telephone number? Those are a little harder.
The more distant or insignificant the memory, the more difficult it is to recall. But does a memory ever completely go away?
Perhaps not, according to groundbreaking research by Dominican University Neuroscience professors Bob and Irina Calin-Jageman.
Their newest research paper, which made the January cover of the peer-reviewed science journal, Learning & Memory, shows that genetic fragments of memory remain in the brains of sea slugs even after the memory seems forgotten.
“We’re fairly confident that this is the first work to show that genetic changes evoked by learning can outlast recall,” Bob Calin-Jageman, professor of psychology and director of Dominican’s neuroscience program, said in a statement announcing the findings. “Our research indicates that even as memories fade, some molecular fragments of the memory can persist in the brain, where they might kickstart relearning. We’re excited that this work might open up new avenues to understanding the neuroscience of forgetting.”
In their experiment, the Calin-Jagemans subjected Aplysia californica, a type of sea slug, to an electric shock on one side of its body. They were then able to track 30,000 genes in the slug’s brain, finding that one day after the shock 1,200 genes were altered through memory.
One week later, that number of active remembering genes had dropped to 11. Those few remaining genes show that a trace fragment of a memory still exists and could be used for relearning, the research suggests.
“It’s not zero, which is the exciting part,” Dominican biology professor Irina Calin-Jageman said in a telephone interview.
She noted in the news release: “This is evidence that the brain holds weak physical traces of previous experiences; that the brain is reconfigured in a way that is different than before.”
The Calin-Jagemans say the sea slug is an ideal candidate for tracking memories because the genetic makeup is far simpler than that of humans or more sophisticated animals. Aplysia californica’s nervous system has about 10,000 neurons, while humans have roughly 80 billion. This makes the neurons easier to isolate and record.
Although the research focuses on the memories of sea slugs, the Calin-Jagemans believe it could one day be used to better understand how more complex animals store and discard memories.
“It’s so fundamental; it will contribute to our understanding of how all nervous systems work and learn,” Irina Calin-Jageman said, noting that practical applications for their findings could be quite a way down the road.
“Forgetting is something we really don’t understand,” she said. “Most of the scientific research has been on how information gets into the brain, not how it fades.
“If we can better understand forgetting, perhaps we can discover breakthrough pharmaceuticals or methods to help slow down the process.”