Offering some hope for patients in the early stages of Alzheimer’s disease, a new UCLA study suggests that lost memories can be restored, researchers announced today.
For decades, most neuroscientists believed that memories are stored at the synapses — the connections between brain cells, or neurons — which are destroyed by Alzheimer’s disease. But the new study provides evidence contradicting the idea.
“Long-term memory is not stored at the synapse,” said David Glanzman, a senior author of the study, and a UCLA professor of integrative biology and physiology, and neurobiology.
“That’s a radical idea, but that’s where the evidence leads,” he said. “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 findings were published recently in eLife, an online science journal.
Glanzman’s research team studies a type of marine snail called Aplysia to understand the animal’s learning and memory. The Aplysia displays a defensive response to protect its gill from potential harm, and the researchers are especially interested in its withdrawal reflex and the sensory and motor neurons that produce it.
They enhanced the snail’s withdrawal reflex by giving it several mild electrical shocks on its tail. The enhancement lasts for days after a series of electrical shocks, which indicates the snail’s long-term memory. Glanzman explained that the shock causes the hormone serotonin to be released in the snail’s central nervous system.
Long-term memory is a function of the growth of new synaptic connections caused by the serotonin, said Glanzman, a member of UCLA’s Brain Research Institute.
As long-term memories are formed, the brain creates new proteins involved in making new synapses. If that process is disrupted — for example by a concussion or other injury –the proteins may not be synthesized and long- term memories cannot form.
Glanzman said the research could have significant implications for people with Alzheimer’s disease. Specifically, just because the disease is known to destroy synapses in the brain doesn’t mean that memories are destroyed, he said.
“As long as the neurons are still alive, the memory will still be there, which means you may be able to recover some of the lost memories in the early stages of Alzheimer’s,” Glanzman said, adding that in the later stages of the disease, neurons die, which likely means that the memories cannot be recovered.
