Study: Lost Memory Can Be Restored Even If Synapses Are Destroyed

New research from UCLA indicates that contrary to long-time scientific theory, lost memories can be restored if new synapses form to reconnect neurons.

In the new study, researchers worked with a type of marine snail to analyze how long-term memory is stored in the brain, finding evidence that challenges earlier theories.

"Long-term memory is not stored at the synapse," lead researcher David Glanzman, a UCLA professor of integrative biology and physiology and of neurobiology, said in a statement. "That's a radical idea, but that's where the evidence leads. The nervous system appears to be able to regenerate lost synaptic connections. If you can restore the synaptic connections, the memory will come back. It won't be easy, but I believe it's possible."

The team gave the snail several mild electrical shocks, which caused the animal to enhance its withdrawal reflex as the hormone serotonin was released in its central nervous system. The snail's reaction to the electric shocks lasted for days, implying its long-term memory.

The study found that the formation of synaptic connections is vital to create long-term memories, but a temporary interruption of synapses after memory is established won't necessarily affect learning.

The new findings, which have vital implications for those who suffer from Alzheimer's and other conditions associated with memory loss, suggest that memory is stored in neurons since long-term memories could come back after synapses were restored.

"If you train an animal on a task, inhibit its ability to produce proteins immediately after training, and then test it 24 hours later, the animal doesn't remember the training," Glanzman said.  "However, if you train an animal, wait 24 hours, and then inject a protein synthesis inhibitor in its brain, the animal shows perfectly good memory 24 hours later.  In other words, once memories are formed, if you temporarily disrupt protein synthesis, it doesn't affect long-term memory. That's true in the Aplysia and in human's brains."