UCI study on how brains mark time may aid dementia research

UC Irvine researchers recently made a discovery in brain studies that they believe could improve understanding of memory-related diseases like dementia.

The researchers were able to capture the processes through which the brain stores information related to when events happen. Areas of the brain identified in the study have long been associated with memories of objects, but until now, little was known about how they might store information about time.

Using top-grade MRI scanners, UCI neurobiologists monitored the brain activity of college students as they watched the HBO TV series “Curb Your Enthusiasm.”

With the participants’ heads inside the scanners, they were first shown an entire episode, then still images of moments within the episode, and were asked to recall when each moment occurred. They rotated a dial to place the images on a timeline displayed on a screen.

“When we give the still image, it reactivates some of the experience,” said professor Michael Yassa, director of UCI’s Center for Neurobiology of Learning & Memory. “What happened before, what happened after, the context. … It has the notion of reactivation, or replay. Some of it might be processed as a semantic, logical flow.”

When participants were able to more accurately mark when moments of the show occurred, they activated a brain network involving the lateral entorhinal cortex and the perirhinal cortex. Those surround the hippocampus, which is thought to be the center of emotion, memory and the autonomic nervous system.

Yassa said the study suggests this is an area researchers should look at to increase knowledge about diseases such as dementia and Alzheimer’s, which are marked by age-related deficits in memory.

“We are already doing the same exact testing in older adults,” Yassa said.

Yassa is the senior author of the study, which appears in the monthly scientific journal Nature Neuroscience. But he credits graduate student Maria Montchal as “the brain behind the entire operation.”

Montchal said the research uncovered a key difference in how our brains mark time vs. how they encode information about space.

“Space and time have always been intricately linked, and the common wisdom in our field was that the mechanisms involved in one probably supported the other as well,” Montchal said. “But our results suggest otherwise.”

A similar UCI study was published last year showing that the lateral entorhinal cortex is dysfunctional in older adults with lower-than-average memory performance, but that study only looked at memory of objects.

Yassa said the latest study confirmed in humans the results of rat studies reported last summer by Nobel laureate Edvard Moser and colleagues at the Kavil Institute of Systems Neuroscience in Norway.

“To be able to have convergent evidence with such a highly regarded institution, it makes this a very real thing,” Yassa said. “I’ve gotten contacted by others in the field since, saying, ‘We find very similar things and we’re sending our research to be published.’ ”

Most laboratory studies examining time use static objects on a computer screen, Yassa said, but they tell little about how the brain processes information in the real world. That’s why the UCI study used “Curb Your Enthusiasm,” a situation comedy that mirrors real life.

“We chose this show in particular because we thought it contained events that were relatable, engaging and interesting,” he said. “We also wanted one without a laugh track.”

Yassa and Montchal’s research was backed by grants from the National Institute of Mental Health and the National Institute on Aging.

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