UCLA Researcher's Radical Idea: 'Long-Term Memory Is Not Stored At The Synapse'

New UCLA research is challenging decades-old beliefs that memory is stored at the brain's synapses. The implications of the new research are that lost long-term memory could be restored, and offers hope for early-stage Alzheimer's disease patients.

Most neuroscientists believe that memory is stored at the synapses, or the connections between brain cells. Alzheimer's disease destroys the synapses, according to Science Daily. The new research out of UCLA challenges the belief that long-term memory is stored at the synapses and that lost memory can't be restored.

"Long-term memory is not stored at the synapse," David Glanzman, UCLA professor and senior author of the study published in eLife, said. "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 memory research was conducted on a type of snail called Aplysia. Science Daily explained how the memory research experiment was set up.

"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."

Glanzman said that when long-term memories are formed, new proteins help create new synapses, but when the process is interrupted, the proteins may not be synthesized. If that happens, long-term memory isn't formed.

"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 explained in a press release. "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."

The memory research challenged the previously held scientific belief that memories are stored in the synapses. With additional research, Glanzman found that in response to serotonin, some of the new synapses created were gone and some older synapses were also gone, but some new synapses remained. Glanzman's research found that there was no obvious pattern to which synapses remained and which memories were able to be retrieved, implying that memory is actually not stored in the synapses. The researchers were then able to encourage new synapses and restore lost memories.

"That suggests that the memory is not in the synapses but somewhere else," Glanzman explained of his radical new findings. "We think it's in the nucleus of the neurons. We haven't proved that, though."

With Alzheimer's disease patients, synapses are destroyed. Glanzman said that if memory is not actually stored there, those memories previously believed lost forever could actually be restored.

"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 explained of the new findings.

In addition to Alzheimer's disease research, this information is applicable in other areas of neuroscience. Glanzman and most other scientists used to believe that extremely traumatic memories could be permanently erased, but that may not be possible if the new research is accurate. A memory stored in a nucleus would be much more difficult to erase than a memory stored at the synapse, so the new research indicates that wiping traumatic memories would be much more challenging than previously believed.

[Photo via Pixabay]