A UCLA research team led by Israeli scientists has made a breakthrough in the field of memory research and sleep that could someday improve treatment for dementia patients.

Maya Geva-Sagiv and other researchers have been able to show that the hippocampus and frontal cortex communicate during sleep to consolidate memories, a previously unproven hypothesis, according to a study published in June in the journal Nature Neuroscience.

“It’s been proven again and again that sleep is important for memory consolidation. But it’s really a mystery what happens during sleep,” said Geva-Sagiv, lead author of the study and now a postdoctoral fellow in the Center for Neuroscience at UC Davis.

Geva-Sagiv, who was raised in Haifa, first found herself studying memory at Jerusalem’s Hebrew University, where she earned her doctorate in neuroscience.

She began by working with animals, analyzing their spatial memory systems — how they remember where something is in their environment. She became fascinated with the way that daily experiences turned into long-lasting memories in the brain, she said.

The new study, done in collaboration with labs at UCLA and Tel Aviv University, sought to understand how memory stays with us long term, said Geva-Sagiv.

To study how memories are created in the brain, the researchers selected 18 epilepsy patients at UCLA. These patients had already been implanted with electrodes that monitored their brain activity as part of their treatment under Dr. Itzhak Fried, study co-author and a neurosurgeon focused on seizure disorders.

Over the course of two nights, researchers carried out a series of tests. On the first night, participants were shown photos matching animals with celebrities. After a normal night of sleep, they were asked to remember the pairings. On the second night, participants were shown new animal-celebrity pairs and, while they slept, synchronized electrical stimulation was sent to different areas of their brains.

To conduct the tests, researchers designed an autonomous system that automatically delivered electric pulses to the brain when the participants entered REM sleep and that monitored their brain activity.

It’s been proven again and again that sleep is important for memory consolidation.

Previous studies on rodents have shown a connection between this kind of stimulation during sleep and improved memory, Geva-Sagiv said, but her study bridges the gap between what we know about the brain from animal research and what we know about the human brain.

“Because we worked with patients, we were able to record very detailed signals from brain areas and also use complex cognitive paradigms and really tap into learning and memory questions,” Geva-Sagiv said.

Geva-Sagiv and the other researchers found that patients who received synchronization-based stimulation in their frontal cortex remembered the animal-celebrity pairs better the next morning. Those who received the stimulation in other areas of the brain did not.

The clinical applications of the study could be far reaching, especially for dementia patients, she said.

Neuropathologist and UCSF professor Lea Grinberg said that the study has significant implications for her work on Alzheimer’s disease and the sleep disturbances that often come with neurodegenerative diseases.

The scientific community had already suspected that memories were solidified during sleep, Grinberg said, but Geva-Sagiv’s study is the first to demonstrate that hypothesis.

“It gives us more impetus to map exactly what Alzheimer’s disease is doing to these neurons controlling sleep and [consciousness] and get a better recipe on how to deal with it,” she said.

Geva-Sagiv, who also studied at the Technion–Israel Institute of Technology and the Weizmann Institute of Science, plans to continue focusing on memory and the brain. She wants to improve on the systems designed for this study’s research and further pinpoint where memories are created in the brain.

“What makes us human,” she said, “are memories.”