WEBVTT - BrainStuff Classics: How Does the Hippocampus Work?

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<v Speaker 1>Welcome to BrainStuff, a production of iHeartRadio. Hey, BrainStuff. I'm

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<v Speaker 1>Lauren Vogelbaum, and this is a classic episode of the podcast.

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<v Speaker 1>In this one, we get into some literal brain stuff

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<v Speaker 1>about how the hippocampus works and what can happen when

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<v Speaker 1>it doesn't work. Hey, BrainStuff. Lauren Vogelbaum here. When the

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<v Speaker 1>movie Memento came out in the year 2000, audiences were

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<v Speaker 1>stunned by the unusual storytelling. The film centered on a

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<v Speaker 1>protagonist with no long-term memory. Every few minutes, he'd forget

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<v Speaker 1>what he had just learned. And to help the audience empathize,

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<v Speaker 1>director Christopher Nolan had the story unfold in reverse chronological order.

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<v Speaker 1>It gave viewers the opportunity to piece together information the

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<v Speaker 1>same way they would if they themselves couldn't retain long-term memories—

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<v Speaker 1>And researchers have actually used this effect of this film

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<v Speaker 1>to deepen our overall understanding of the memory mechanisms in

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<v Speaker 1>the brain. One of the study authors said in a statement,

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<v Speaker 1>Memento simulates what it would feel like to be a

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<v Speaker 1>person who has suffered damage to the hippocampus that has

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<v Speaker 1>obliterated the formation of long-term memories. Even short-term memories last

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<v Speaker 1>only a couple of minutes before they're gone. The hippocampus

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<v Speaker 1>also gets damaged, albeit to a lesser extent, in cases

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<v Speaker 1>of severe and protracted stress as stress hormones gnaw the brain.

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<v Speaker 1>Brain nerds, which honestly should probably be all of us,

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<v Speaker 1>may know that the amygdala plays a major role in

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<v Speaker 1>controlling fear and the cerebellum makes coordinated movement possible. But

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<v Speaker 1>how does the hippocampus work? And why does it play

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<v Speaker 1>such a pivotal role in keeping our memories safe? We

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<v Speaker 1>spoke with psychiatrist Ellen Vora, MD. She explained that the

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<v Speaker 1>hippocampus is, quote, part of our limbic brain, a deep,

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<v Speaker 1>primitive part of our brain that's associated with emotion and memory.

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<v Speaker 1>Located in the temporal lobe, this tiny organ plays a

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<v Speaker 1>massive role in the storage of long-term memories and the

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<v Speaker 1>memory of the location of people and objects. It's named

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<v Speaker 1>for the Greek words hippo, meaning horse, and campo, meaning monster,

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<v Speaker 1>which is a word for seahorse because the structure curves

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<v Speaker 1>around like a seahorse or horseshoe. We actually have two

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<v Speaker 1>hippocampi structures, one in each hemisphere of the brain, though

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<v Speaker 1>together they're generally referred to as the singular hippocampus. And yes,

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<v Speaker 1>the hippocampus resides in the limbic system, which is associated

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<v Speaker 1>with emotions and reactions. As you might expect, people with

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<v Speaker 1>Alzheimer's disease have demonstrated damage to the hippocampus. The function

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<v Speaker 1>of the hippocampus is perhaps most clear in examples of

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<v Speaker 1>patients who have sustained damage to theirs. In the 1950s,

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<v Speaker 1>scientists William Beecher Scoville and Brenda Milner described what happened

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<v Speaker 1>to a man with epilepsy who'd received surgery on his

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<v Speaker 1>hippocampus in an effort to relieve the seizures. He retained

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<v Speaker 1>memories from his childhood, but he couldn't form new memories

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<v Speaker 1>or piece together when or where things happened. That same decade, Dr.

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<v Speaker 1>William Scoville began removing patients' hippocampus. At the time, scientists

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<v Speaker 1>knew it helped process emotions, but they weren't totally clear

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<v Speaker 1>on how. Scoville wanted to see what would happen if

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<v Speaker 1>he removed part of the brain in patients exhibiting certain symptoms,

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<v Speaker 1>like seizures. One such patient, referred to as H.M., underwent

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<v Speaker 1>the surgery and found relief from his epilepsy, but a

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<v Speaker 1>near total loss of memory. In the 1980s, Kent Cochran,

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<v Speaker 1>famously known in the psychology and neuroscience worlds as K.C.,

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<v Speaker 1>fell off his motorcycle and lost several brain structures, including

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<v Speaker 1>his hippocampus. Predictably, he lost most of his memories, but

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<v Speaker 1>held on to some specific ones from his earlier life.

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<v Speaker 1>All things that seemed rooted in fact and devoid of

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<v Speaker 1>emotion or context. Experts later came to call these types

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<v Speaker 1>of memories semantic memories. So while patients like KC could

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<v Speaker 1>clearly keep a handful of memories intact, most were lost.

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<v Speaker 1>Recollections of personal experience are all pretty much a loss

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<v Speaker 1>in the damage or removal of the hippocampus. These types

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<v Speaker 1>of memories are now known as episodic memory. KC, for example,

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<v Speaker 1>could remember that his brother had gotten married, and he

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<v Speaker 1>could recognize family members in photos from that day, all

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<v Speaker 1>facts based in semantic memory. But he couldn't remember his

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<v Speaker 1>family reacting to the perm he had gotten for the occasion,

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<v Speaker 1>which is episodic memory. Over time, scientists came to understand

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<v Speaker 1>that the hippocampus is involved in two types of memory,

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<v Speaker 1>declarative and spatial. Declarative memories are the ones associated with

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<v Speaker 1>facts or events. Semantic memory is considered one type of

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<v Speaker 1>declarative memory, and episodic is another type. The hippocampus is

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<v Speaker 1>also involved in spatial relationship memories, the kind related to

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<v Speaker 1>roots and pathways. And it's also where short-term memories are

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<v Speaker 1>turned into long-term memories, which are then stored elsewhere in

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<v Speaker 1>the brain. Different types of illness and accidents can damage

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<v Speaker 1>the hippocampus. Doctors generally aren't removing the hippocampus for experimentation anymore,

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<v Speaker 1>like in the case of HM, though. Alzheimer's disease is

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<v Speaker 1>perhaps the most notorious destroyer of the hippocampus, as the

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<v Speaker 1>condition has been correlated with atrophy or shrinking of that

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<v Speaker 1>area of the brain. As in the case of HM,

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<v Speaker 1>epilepsy is also known to affect the hippocampus. Studies have

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<v Speaker 1>shown that between 50 to 75% of patients with epilepsy

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<v Speaker 1>have hippocampus damage. Two other serious threats to the hippocampus,

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<v Speaker 1>as mentioned above, are severe depression and stress. Studies have

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<v Speaker 1>demonstrated that the hippocampus can shrink by up to 20%

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<v Speaker 1>in people with severe depression, and reviews of studies found

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<v Speaker 1>that people with severe depression may have hippocampi that are

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<v Speaker 1>an average of 10% smaller than in those people without depression.

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<v Speaker 1>Vora said, It's a part of the brain that's very

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<v Speaker 1>susceptible to stress. We see it lose volume under conditions

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<v Speaker 1>of chronic stress and depression. Conversely, you can restore your

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<v Speaker 1>hippocampus with meditation and stress management. You want a healthy

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<v Speaker 1>hippocampus so you can remember things. A 2016 review of

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<v Speaker 1>studies found that exercise in old age may have the

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<v Speaker 1>ability to help strengthen the hippocampi's ability to generate new cells,

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<v Speaker 1>which could, in turn, help prevent cognitive decline. It's still

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<v Speaker 1>unclear how and why this works, but researchers are continuing

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<v Speaker 1>to investigate the connection. A 2017 study also found that

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<v Speaker 1>the hippocampus may play a role in many more functions

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<v Speaker 1>than memory and pathfinding. The tiny organ may also have

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<v Speaker 1>a part in enhancing the responsiveness of vision, touch, and hearing.

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<v Speaker 1>Thanks to the continued new findings, some have begun referring

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<v Speaker 1>to the hippocampus as the heart of the brain. Today's

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<v Speaker 1>episode is based on the article, Without a Hippocampus, Your

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<v Speaker 1>Long-Term Memory is History, on HowStuffWorks.com, written by Michelle Konstantinovsky.

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<v Speaker 1>BrainStuff is a production of iHeart Podcasts in partnership with

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<v Speaker 1>HowStuffWorks.com and is produced by Tyler Clang. For more shows

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<v Speaker 1>from iHeart Podcasts, visit the iHeart Radio app, Apple Podcasts,

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