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Brain's memory center also key for real-time decision-making

New research shows that while the hippocampus is key to long-term memory, it also provides sorting and context for short-term memory and decision-making. Photo by toubibe/Pixabay
New research shows that while the hippocampus is key to long-term memory, it also provides sorting and context for short-term memory and decision-making. Photo by toubibe/Pixabay

June 18 (UPI) -- The hippocampus, one the brain's largest regions, is mostly known as the epicenter of long-term memory, but it handles other tasks too.

In a new study, researchers have highlighted the importance of the hippocampus to short-term and spatial memory, as well as real-time decision-making.

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The latest findings -- published Friday in the journal Science Advances -- suggests the much-studied brain region is essential to our navigational abilities.

Experiments showed that as study volunteers scan their environs, taking in navigational cues, the hippocampus becomes alive with neural activity -- fielding and sorting the short-term memories and visual information the brain uses to make decisions on the fly.

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"At any given moment, your brain rapidly initiates eye movements that you are typically unaware of," study corresponding author James Kragel said in a press release.

"Our findings suggest the hippocampus uses memory to inform where your eyes look, thereby priming the visual system to learn and reevaluate our environment on the fly," said Kragel, a postdoctoral research fellow at Northwestern University Feinberg School of Medicine.

More than just making decisions about whether to turn left or right, the hippocampus helps the brain forge connections between distinct but related visual stimuli.

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Say a person is walking down the street and sees a car parked askew in the middle of a neighbor's front yard. It's strange, but it's a busy morning, and the image gets quickly pushed aside.

A few moments later, a firetruck and ambulance rush by. Without the hippocampus, the brain might fail to associate these two short-term memories.

With a functioning hippocampus, however, a person can connect the dots and reconsider the car seen moments earlier.

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With the help of the hippocampus, these two short-term memories become a long-term memory.

"If you didn't look back and see the crash, you might not encode that important information, but in using short-term memory retrieval, you can tie those clues together and remember details that cue bigger memories," Kragel said. "It all comes down to building connections among these disparate elements that allow you to remember them later in a much easier way."

While the hippocampus can still take nostalgic daydreamers on a trip down memory lane, the new research suggests memory-making and memory-processing play an important role in our ability to process our visual, moment-to-moment experiences.

"This [understanding] is key to understanding hippocampal function and developing effective treatments for memory disorders," said study author Joel Voss, associate professor of medical social sciences, neurology, and psychiatry and behavioral sciences at Feinberg.

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"It is as if you are using your memory to plan for what to expect, and then when it mismatches with what is actually unfolding, your hippocampus gets activated to reevaluate and update your current perception of what is going on," Kragel said.

For the study, researchers recruited epilepsy patients who had come to Northwestern Memorial Hospital to order to locate the neurological origins of their seizures.

While the volunteers were in the epilepsy-monitoring unit and hooked up to electrodes, researchers had them perform a memory task.

Each study participant was made to scan a series of complex scenes, each featuring a variety of people and objects, like a person sitting at a picnic table eating lunch as park-goers and pets frolicked in the background. Afterward, the volunteers were given a memory quiz.

During the quiz, volunteers were asked whether the scenes they viewed were old or new. In addition to recording brain activity, researchers monitored the eye movements of the study participants.

Scientists found that while studying a scene for the first time, participants regularly retrained their eyes on a location they had looked at just milliseconds earlier.

The electrode showed neural activity patterns in the hippocampus shifted just prior to these "revisitation" eye movements. Additionally, each revisitation was followed by an increase in brain activity.

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"This shows that the hippocampal contribution to memory unfolds over just hundreds of milliseconds during ongoing behavior, which is surprising given that the timecourse of its involvement, typically seen in long-term memory retrieval, is usually thought to be days to years," Voss said.

The latest insights into the functionality of the hippocampus could ultimately inspire new treatments for age-related memory decline and neurodegenerative diseases like dementia, according to the researchers.

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