How ‘extinction neurons’ help us block out our worst memories

A recent study could help improve treatments for PTSD, anxiety and phobias.

  • A new study examined how the effects of fear-related memories can be silenced in the brain.
  • Forming new and positive "extinction memories" can help to silence fearful memories.
  • The study found that the hippocampus plays a significant role in "extinction training."

Memories associated with traumatic events can cause unexpected problems in everyday life. A woman with a phobia of dogs might experience a rush of fear when she happens to find herself right next to a dog without a leash in the park. In cases like this, a psychologist might recommend exposure therapy, in which people with specific fears are voluntarily and incrementally exposed to the very things they fear. The goal is to create new positive memories to silence the fearful ones. These are called "extinction memories."

Scientists have long associated a part of the brain called the amygdala with fear. However, a new study focuses on the hippocampus — a brain region generally associated with memory and spatial navigation — and describes how extinction memories work not by replacing fearful memories, but rather by competing with them. This competition acts in two ways: by decreasing or silencing the activation of fear-inducing neurons and by activating a distinct set of neurons that help to reduce the fear response.

The study was published April 1 in the journal Nature Neuroscience.

"Extinction does not erase the original fear memory but instead creates a new memory that inhibits or competes with the original fear," said Michael Drew, associate professor of neuroscience and the senior author of the study, to Science Daily. "Our paper demonstrates that the hippocampus generates memory traces of both fear and extinction, and competition between these hippocampal traces determines whether fear is expressed or suppressed.

Social anxiety: How to rewire your confidence and be a better communicator

In the study, Drew and his colleagues placed mice inside a box and induced fear with a minor electric shock. The mice then associated the box with pain and displayed fearfulness when placed inside it again. But after repeatedly being placed in the box without getting shocked, the mice formed extinction memories and eventually stopped showing fear.

Using optogenetics — a method that uses light-based tools to modulate molecular events — the researchers were able to artificially induce fear in the mice in two ways: stimulating neurons associated with fear, and silencing neurons associated with the extinction training. Similarly, the researchers managed to reduce fear by silencing the fear-related neurons and stimulating the extinction neurons.

The researchers hope their findings can be used to improve treatments for post-traumatic stress disorder, phobias and anxieties.

"Artificially suppressing these so-called extinction neurons causes fear to relapse, whereas stimulating them prevents fear relapse," Drew said. "These experiments reveal potential avenues for suppressing maladaptive fear and preventing relapse."

3D printing might save your life one day. It's transforming medicine and health care.

What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.

Northwell Health
Sponsored by Northwell Health
  • Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
  • Eventually, scientists hope to print patient-specific organs that can be transplanted safely into the human body.
  • Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
Keep reading Show less

Are people getting smarter or dumber? Yes.

The Flynn effect shows people have gotten smarter, but some research claims those IQ gains are regressing. Can both be right?

Surprising Science
  • Many countries made incredible gains in IQ scores during the 20th century, averaging three IQ points per decade.
  • Studies out of Europe have shown a reversal of this trend.
  • Such declines are not universal, and researchers remain unsure of what is causing them.
Keep reading Show less

Scientists turn nuclear waste into diamond batteries

They'll reportedly last for thousands of years. This technology may someday power spacecraft, satellites, high-flying drones, and pacemakers.

Woman looking at a diamond.
popular

Nuclear energy is carbon free, which makes it an attractive and practical alternative to fossil fuels, as it doesn't contribute to global warming. We also have the infrastructure for it already in place. It's nuclear waste that makes fission bad for the environment. And it lasts for so long, some isotopes for thousands of years. Nuclear fuel is comprised of ceramic pellets of uranium-235 placed within metal rods. After fission takes place, two radioactive isotopes are left over: cesium-137 and strontium-90.

Keep reading Show less

Want to forge stronger social bonds? Bring beer.

New research shows that a healthy supply of locally-sourced beer helped maintain Wari civilization for 500 years.

Culture & Religion
  • A new analysis of an ancient Wari brewery suggests chicha helped maintain the civilization's social capital for hundreds of years.
  • Civilizations throughout the ancient world used alcoholic drinks to signify kinship, hospitality, and social cohesion.
  • The researchers hope their findings will remind us of the importance in reaffirming social institutions and sharing cultural practices — even if over coffee or tea.

Beer is history's happiest accident. Though the discovery probably happened much earlier, our earliest evidence for beer dates back roughly 13,000 years ago. Around this time, the people of the Fertile Crescent had begun to gather grains as a food source and learned that if they moistened them, they could release their sweetness to create a gruel much tastier than the grains themselves.

One day a curious — or perhaps tightfisted — hunter-gatherer hid his gruel away for a safekeeping. When he returned, he found the bowl giving off a tangy odor. Not one to waste a meal, he ate it anyway and enjoyed an unexpected, though not unpleasant, sensation of ease. By pure happenstance, this ancestor stumbled upon brewing.

That's one possible origin story, but we know that our ancestors learned to control the process, and beer took a central role in Fertile Crescent civilizations — so central that Professor Patrick McGovern, a biomolecular archaeologist at the University of Pennsylvania, argues that beer, not bread, incentivized hunter-gatherers to relinquish their nomadic ways.

Beer may also be proof of a God who wants us to be happy (Dionysus?), because the beverage* would be independently rediscovered by peoples across the ancient world, including those in China and South America.

One such peoples, the pre-Inca Wari Civilization, made beer, specifically chicha de molle, a critical component in their religious and cultural ceremonies. In fact, a study published in Sustainability in April argues that the role was so important that beer helped keep Wari civilization intact for 500 years.

Brewing social capital

Twenty years ago, a team of archaeologists with the Field Museum of Natural History, Chicago, discovered a brewery in Cerro Baúl, a mesa in southern Peru that served as an ancient Wari outpost. The brewery contained original equipment, clay storage vessels, and compartments for milling, boiling, and fermentation.

The team recently analyzed these on-site vessels to uncover the secrets of the Wari brewing process. Removing tiny amounts of material found in the spaces between the clay, they were able to reconstruct the molecules of the thousand-year-old drink. They then worked alongside Peruvian brewers to recreate the original brewing process.**

Their molecular analysis revealed several key features of the beer: The clay used to make the vessels came from a nearby site; many of the beer's ingredients, such as molle berries, are drought resistant; and though alcoholic, the beer only kept for about a week.

These details suggest that Cerro Baúl maintained a steady supply of chicha, limited by neither trade nor fair weather, and became a central hub for anyone wishing to partake. The Wari would likely make such trips during times of festivals and religious ceremonies. Social elites would consume chicha in vessels shaped like Wari gods and leaders as part of rituals attesting to social norms and a shared cultural mythology and heritage.

"People would have come into this site, in these festive moments, in order to recreate and reaffirm their affiliation with these Wari lords and maybe bring tribute and pledge loyalty to the Wari state," Ryan Williams, lead author and head of anthropology at the Field Museum, said in a release. "We think these institutions of brewing and then serving the beer really formed a unity among these populations. It kept people together."

The Wari civilization was spread over a vast area of rain forests and highlands. In a time when news traveled at the speed of a llama, such distinct and distant geography could easily have fractured the Wari civilization into competing locales.

Instead, the researchers argue, these festive gatherings (aided by the promise of beer) strengthened social capital enough to maintain a healthy national unity. This helped the Wari civilization last from 600 to 1100 CE, an impressive run for a historic civilization.

Bringing people together (since 10,000 BCE)

A Mesopotamian cylinder seal shows people drinking beer through long reed straws. Image source: Metropolitan Museum of Art.

Of course, the Wari weren't the first civilization to use beer to reaffirm bonds and maintain their social fabric. Returning to the Fertile Crescent, Sumerians regarded beer as a hallmark of their civilization.

The Sumerian Epic of Gilgamesh tells of the adventures of the titular hero and his friend Enkidu. Enkidu beings as a savage living in the wilderness, but a young woman introduces him to the ways of civilization. That orientation begins with food and beer:

"They placed food in front of him,
They placed beer in front of him,
Enkidu knew nothing about eating bread for food,
And of drinking beer he had not been taught.
The young woman spoke Enkidu, saying:
"Eat the food, Enkidu, it is the way one lives.
Drink the beer, as is the custom of the land."
Enkidu ate the food until he was sated,
He drank the beer — seven jugs! — and became expansive
and sang with joy.
He was elated and his face glowed.
He splashed his shaggy body with water
and rubbed himself with oil, and turned into a human
."

Tom Standage, who recounts this scene in his History of the World in 6 Glasses, writes: "The Mesopotamians regarded the consumption of bread and beer as one of the things that distinguished them from savages and made them fully human." Such civilized staples not only demarcated their orderly life from that of hunter-gatherers, they also served a key role in their culture's unifying mythology.

Furthermore, Standage notes, Sumerian iconography often shows two people sipping from waist-high jars through reed straws. The earliest beers were consumed in a similar fashion because technological limitations prevented baking individual cups or filtering the beverage. But the Sumerians had the pottery skills to make such cups and filter the dregs. That they kept the tradition suggests that they valued the camaraderie brought by the experience, a sign of communal hospitality and kinship.

The ancient Greek's similarly used alcohol as a means of maintaining social and political relationships — though their drink of choice was wine.

During symposiums, upper-class Greek men would gather for a night of drinking, entertainment, and social bonding. In Alcohol: A history, Rod Phillips notes that symposiums were serious affairs where art, politics, and philosophy were discussed throughout the night and could serve as rites of passage for young men. (Though, music, drinking games, and sex with prostitutes may also be found on the itinerary.)

Of course, we can amass social capital without resorting to alcohol, which has been known to damage social relationships as much as improve them.

In the 17th century, London's coffeehouses stimulated the minds of thinkers with their caffeine-laden drinks, but also served as social hubs. Unlike the examples we've explored already, these coffeehouses brought together people of different backgrounds and expertise, unifying them in their pursuit of ideas and truths. Thus, coffeehouses can be seen as the nurseries of the Enlightenment.

Relearning ancient lessons

The Field Museum archaeologists hope their research can help remind us the importance social institutions and cultural practices have in creating our common bonds, whether such institutions are BYOB or not.

"This research is important because it helps us understand how institutions create the binds that tie together people from very diverse constituencies and very different backgrounds," Williams said. "Without them, large political entities begin to fragment and break up into much smaller things. Brexit is an example of this fragmentation in the European Union today. We need to understand the social constructs that underpin these unifying features if we want to be able to maintain political unity in society."

So, grab a beer or coffee or tea, spend some time together, and raise a glass. Just try not focus too much on whether your friend ordered Budweiser's swill or an overpriced, virtue-signaling microbrew IPA.

Keep reading Show less