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Dopamine is a brain chemical famously linked to mood and pleasure − but researchers have found multiple types of dopamine neurons with different functions



Dopamine is a brain chemical famously linked to mood and pleasure − but researchers have found multiple types of dopamine neurons with different functions

A better understanding of dopamine could to better treatments for neurodegenerative and neurodevelopmental diseases, among others.
Kateryna Kon/Science Photo Library via Getty Images

Kimberlee D'Ardenne, Arizona State University

Dopamine seems to be a moment in the zeitgeist. You may have read about it in the news, seen viral social media posts about “dopamine hacking” or listened to podcasts about how to harness what this molecule is doing in your brain to improve your mood and productivity. But recent neuroscience research suggests that popular strategies to control dopamine are based on an overly narrow view of how it functions.

Dopamine is one of the brain's neurotransmitters – tiny molecules that act as messengers between neurons. It is known for its role in tracking your reaction to rewards such as food, sex, money or answering a question correctly. There are many kinds of dopamine neurons located in the uppermost region of the brainstem that manufacture and release dopamine throughout the brain. Whether neuron type affects the function of the dopamine it produces has been an open question.

Recently published research reports a relationship between neuron type and dopamine function, and one type of dopamine neuron has an unexpected function that will likely reshape how scientists, clinicians and the public understand this neurotransmitter.

Dopamine is involved with more than just pleasure.

Dopamine neuron firing

Dopamine is famous for the role it plays in reward processing, an idea that dates back at least 50 years. Dopamine neurons monitor the difference between the rewards you thought you would get from a behavior and what you actually got. Neuroscientists call this difference a reward prediction error.


Eating dinner at a restaurant that just opened and looks likely to be nothing special shows reward prediction errors in action. If your meal is very good, that results in a positive reward prediction error, and you are likely to return and order the same meal in the future. Each time you return, the reward prediction error shrinks until it eventually reaches zero when you fully expect a delicious dinner. But if your first meal was terrible, that results in a negative reward prediction error, and you probably won't go back to the restaurant.

Dopamine neurons communicate reward prediction errors to the brain through their firing rates and patterns of dopamine release, which the brain uses for learning. They fire in two ways.

Phasic firing refers to rapid bursts that cause a short-term peak in dopamine. This happens when you receive an unexpected reward or more rewards than anticipated, like if your server offers you a dessert or includes a nice note and smiley face on your check. Phasic firing encodes reward prediction errors.

By contrast, tonic firing the slow and steady activity of these neurons when there are no surprises; it is background activity interspersed with phasic bursts. Phasic firing is like mountain peaks, and tonic firing is the valley floors between peaks.

Diagram depicting the phasic peaks and tonic valleys of dopamine levels
This diagram shows the phasic peaks and tonic valleys of dopamine levels, the former encoding unexpected rewards and the latter encoding expected .
Dreyer et al. 2010/Journal of Neuroscience, CC BY-NC-SA

Dopamine functions

Tracking information used in generating reward prediction errors is not all dopamine does. I have been all the other jobs of dopamine with interest through my own research measuring brain where dopamine neurons are located in people.

About 15 years ago, reports started coming out that dopamine neurons respond to aversive events – think brief discomforts like a puff of against your eye, a mild electric shock or losing money – something scientists thought dopamine did not do. These studies showed that some dopamine neurons respond only to rewards while others respond to both rewards and negative experiences, leading to the hypothesis that there might be more than one dopamine system in the brain.

These studies were soon followed by experiments showing that there is more than one type of dopamine neuron. So far, researchers have identified seven distinct types of dopamine neurons by looking at their genetic profiles.

A study published in August 2023 was the first to parse dopamine function based on neuron subtype. The researchers at the Dombeck Lab at Northwestern examined three types of dopamine neurons and found that two tracked rewards and aversive events while the third monitored movement, such as when the mice they studied started running faster.

Dopamine release

Recent coverage on how to control dopamine's effects is based only on the type of release that looks like peaks and valleys. When dopamine neurons fire in phasic bursts, as they do to signal reward prediction errors, dopamine is released throughout the brain. These dopamine peaks happen very fast because dopamine neurons can fire many times in less than a second.


There is another way that dopamine release happens: Sometimes it increases slowly until a desired reward is obtained. Researchers discovered this ramp pattern 10 years ago in a part of the brain called the striatum. The steepness of the dopamine ramp tracks how valuable a reward is and how much effort it takes to get it. In other words, it encodes motivation.

The restaurant example can also illustrate what happens when dopamine release occurs in a ramping pattern. When you have ordered a meal you know is going to be amazing and are waiting for it to arrive, your dopamine levels are steadily increasing. They reach a crescendo when the server places the dish on your table and you sink your teeth into the first bite.

Diagram of ramp pattern dopamine release, which shows a steep rise that levels off
This diagram shows a ramp pattern dopamine release, reaching a peak when a reward is obtained.
Collins et al. 2016/Scientific Reports, CC BY

How dopamine ramps happen is still unsettled, but this type of release is thought to underlie goal pursuit and learning. Future research on dopamine ramping will affect how scientists understand motivation and will ultimately improve advice on how to optimally hack dopamine.

Dopamine(s) in disease and neurodiversity

Though dopamine is known for its involvement in drug addiction, neurodegenerative disease and neurodevelopmental conditions like attention-deficit/hyperactivity disorder, recent research suggests how scientists understand its involvement may soon need updating. Of the seven subtypes of dopamine neurons that are known so far, researchers have characterized the function of only three.

There is already some evidence that the discovery of dopamine diversity is updating scientific knowledge of disease. The researchers of the recent paper identifying the relationship between dopamine neuron type and function point out that movement-focused dopamine neurons are known to be among the hardest hit in Parkinson's disease, while two other types are not as affected. This difference might lead to more targeted treatment options.


Ongoing research untangling the diversity of dopamine will likely continue to change, and improve, our understanding of disease and neurodiversity.The Conversation

Kimberlee D'Ardenne, Assistant Research Professor in Psychology, Arizona State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Excavating data from digs done decades ago and connecting with today’s communities



theconversation.com – Emily Fletcher, Ph.D. Candidate in Archaeology, Purdue – 2024-06-18 07:39:20

Archaeologists excavate at the Gulkana Site in the 1970s.

Dr. William Workman Collection

Emily Fletcher, Purdue University

The ancestors of Alaska Native people began using local copper sources to craft intricate tools roughly 1,000 years ago. Over one-third of all copper objects archaeologists have found in this region were excavated at a single spot, named the Gulkana Site.


This is the site I've studied for the past four years as a Ph.D. student at Purdue University. In spite of its importance, the Gulkana Site is not well known.

To my knowledge, it isn't mentioned in any museums. Locals, Alaska Native Ahtna people, who descend from the site's original inhabitants, might recognize the name, but they don't know much about what happened there. Even among archaeologists, little information is available about it – just a few reports and passing mentions in a handful of publications.

However, the Gulkana Site was first identified and excavated nearly 50 years ago. What gives?

Archaeology has a data management problem, and it is not unique to the Gulkana Site. U.S. federal regulations and disciplinary standards require archaeologists to preserve records of their excavations, but many of these records have never been analyzed. Archaeologists refer to this problem as the “legacy data backlog.”


As an example of this backlog, the Gulkana Site tells a story not only about Ahtna history and copperworking innovation, but also about the ongoing value of archaeological data to researchers and the public alike.

What happens after an excavation?

In the United States, most excavations, including those that have happened at the Gulkana Site, occur through a process called Cultural Resource Management. Since the 1960s, federal regulations in the U.S. have required archaeological excavations prior to certain development projects. Regulations also require that records of any finds be preserved for future generations.

One estimate suggests that this process has created millions of records in the legacy data backlog. Archaeological data is complex, and these records include many file formats, varying from handwritten maps to pictures and spatial data.

The problem is worst for datasets that were created before computers were in common use. Research suggests that archaeologists are biased toward digital datasets, which are easier to access and use with modern methods. Ignoring nondigital datasets means not only abandoning the product of decades of archaeological work, it also silences the human experiences those datasets are meant to preserve. Once a site is excavated, this data is the only way the people who lived there can tell their story.


Archaeologists aren't sure how to resolve this problem. Many have been proposed, including the creation of new data repositories, making new use of existing datasets whenever possible, and increasing collaboration with other disciplines and with public stakeholders. One of the more creative solutions, the Vesuvius Challenge, recently made headlines for awarding its US$700,000 grand prize to a team that successfully used artificial intelligence to read ancient text.

Digital archaeology excavates old data

Of course, such a complicated problem has no single miracle cure. In my work with the Gulkana Site, I'm employing many of these suggestions through a newer form of archaeology that some researchers are calling digital public archaeology. It combines digital archaeology, which uses computers in archaeological research, with public archaeology, which honors the public's interest in the past.

For me, archaeology looks different than what people might expect. Instead of spending my days excavating in some fabulous location, my work involves being parked at a computer for hours on end. I dig through old information instead of digging up new information.

As a digital archaeologist, I apply modern methods like AI to bring new to decades-old data about the Gulkana Site. I write software that converts 50-year-old handwritten excavation notes into a digital map that I can analyze with a computer.


Although it is less glamorous, this work is arguably more important than excavation. Excavation is merely a data collection technique; on its own, it can't reveal much about a site. This is why there is still much to learn about the Gulkana Site, even though it was excavated decades ago.

Analysis is the way archaeologists learn about the past, and computers make more methods available to us than ever before. In my work, I use computational mapping techniques to study the copper artifacts recovered from the Gulkana Site. Studying where these objects were found will help us understand if they were used by all people at the Gulkana Site or reserved for a select few.

Connecting archaeology to communities today

I am also a public archaeologist; I believe that the past is made meaningful through the people connected to it. This means that my study of the Gulkana Site would be insufficient were it conducted solely by me, alone at my computer 3,000 miles away from Alaska. Instead, I have designed my research in collaboration with descendants of the people who lived at the Gulkana Site to ensure my research holds value to them, not just to archaeologists.

In my research, this means embedding opportunities for youth involvement throughout my . Each year, I travel to Alaska to host a course about archaeology, Ahtna history, and technology in collaboration with Ahtna leadership and the local school district.


In the course, we take field trips to archaeological sites and the Ahtna Cultural Center. Kids learn about the artifacts found at the Gulkana Site and have an to make their own. Ahtna leaders share cultural knowledge with . At the end of the course, students integrate what they've learned into a video about the Gulkana Site.

The goal of my research is to bring new life to the Gulkana Site through digital methods and outreach. My experiences demonstrate that even a site excavated 50 years ago can reveal more to help us better understand the past. Perhaps more importantly, it can also help the next generation gain experience with technological skills and connect with their heritage. Old archaeological data is still meaningful in the digital age – we just have to pay attention to it.The Conversation

Emily Fletcher, Ph.D. Candidate in Archaeology, Purdue University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Keeping astronauts healthy in space isn’t easy − new training programs will prepare students to perform medicine while thousands of miles away from Earth



theconversation.com – Arian Anderson, Emergency Medicine Physician, of Colorado Anschutz Medical Campus – 2024-06-18 07:39:04

medicine professionals in consult with each other during a simulation exercise.

Katya Arquilla

Arian Anderson, University of Colorado Anschutz Medical Campus

In the coming decade, more people will go to space than ever before as human spaceflight enters a new era. NASA, the European Space Agency and other governmental agencies are partnering to develop crewed missions beyond the Moon. At the same time, these agencies are collaborating with private companies using new technologies to down the price of space exploration.


Companies such as SpaceX, Blue Origin and Sierra Space have developed vehicles with reusable boosters, automated flight systems and lightweight materials to support these deep space missions. Some even have ambitions of their own to build private space stations, Moon bases or mining operations in the coming decades.

But as these technologies and partnerships rapidly make spaceflight more accessible, new challenges emerge. For one, maintaining the health and performance of an astronaut crew. My team of researchers and educators at the University of Colorado and others around the world are looking to address this issue.

A group of people in orange jumpsuits stand around a table, with a person laying on it.

With spaceflight set to expand, astronauts will need access to medical care over longer voyages and on commercial flights.

Katya Arquilla

Emerging medical challenges in space

NASA astronauts are some of the most accomplished people on the planet, and they're some of the healthiest. Astronauts undergo extensive medical and psychological testing that in one study disqualified 26% of final-round applicants. This rigorous screening and testing effectively limits the of a medical occurring during a mission.


But as spaceflight becomes more accessible, astronaut crews on commercial missions will likely make up the majority of space travelers in the coming years. Private missions will be short and stay in a close orbit around Earth in the near term, but private crews will likely have less training and more chronic medical conditions than the professional astronauts currently living and working in space.

While experiments aboard the International Space Station have extensively studied the normal physiological changes occurring to the human system in weightlessness, there is limited to no data about how common chronic diseases such as diabetes or high blood pressure behave in the space .

Mars, shown from space.

During Mars missions, astronauts will be away from Earth for long periods of time, with limited access to medical resources.


This industry boom is also creating opportunities for long-duration missions to the Moon and Mars. Because of the length of missions and the distance from Earth, professional astronauts on these missions will experience prolonged weightlessness, leading to bone and muscle loss, communication delays of a few seconds up to 40 minutes, and extreme isolation for months to years at a time.


Crews must function autonomously, while being exposed to new hazards such as lunar or Martian dust. Because of the fuel required for these missions, resources will be limited to the lowest mass and volume possible.

As a result, mission planners will need to make difficult decisions to determine what supplies are truly necessary in advance, with limited or unavailable resupply opportunities for food, water and medicine. In space, for example, radiation and humidity inside a spacecraft can cause medications to deteriorate more quickly and become unavailable or even toxic to crew members.

Crews on the space station have access to a flight surgeon at Mission Control to help manage medical care in the same way telehealth is used on Earth. Crews on distant planets, however, will need to perform medical care or procedures autonomously.

In the event of a medical emergency, crews may not be able to evacuate to Earth. Unlike the space station, where medical evacuations to Earth can occur in less than 24 hours, lunar evacuations may take weeks. Evacuations from Mars may not be possible for months or even years.


Put simply, the current approaches to medical care in spaceflight will not meet the needs of future commercial and professional astronauts. Researchers will need to develop new technologies and novel training approaches to prepare future providers to treat medical conditions in space.

The current leaders in space medicine are either experts in aerospace engineering or in medicine, but rarely do experts have formal training or a complete understanding of both fields. And these disciplines often can't speak each other's language both literally and figuratively.

Training the next generation

To meet the evolving demands of human spaceflight, educators and universities are looking to develop a way to train specialists who understand both the limitations of the human body and the constraints of engineering design.

Some schools and hospitals, such as the University of Texas Medical Branch, have residency training programs for medical school graduates in aerospace medicine. Others, such as UCLA and Massachusetts General Hospital, have specialty training programs in space medicine, but these currently target fully trained emergency medicine physicians.


My team at the University of Colorado has created a program that integrates human physiology and engineering principles to train medical students to think like engineers.

Two domed tents connected by long tubes, in the desert.

The University of Colorado brings students to the desert to simulate a lunar base. Students work together to solve simulated medical issues that might occur during a space mission.

Katya Arquilla

This program aims to help students understand human health and performance in the spaceflight environment. It approaches these topics from an engineering design and constraints perspective to find to the challenges astronauts will face.

One of our most popular classes is called Mars in Simulated Surface Environments. This class puts students through engineering and medical scenarios in a simulated Mars environment in the Utah desert. Students deal with the challenges of working and providing care while wearing a spacesuit and on a desolate Mars-like landscape.


The stress of the simulations can feel real to the students, and they learn to apply their combined skill sets to care for their fellow crew members.

Educational programs like these and others aim to create cross-trained specialists who understand both patient care and the procedural nature of engineering design and can merge the two, whether for space tourists in orbit or as a pioneer to the surface of another planet.

A new period of spaceflight is here, and these programs are already training experts to make space accessible and safe.The Conversation

Arian Anderson, Emergency Medicine Physician, University of Colorado Anschutz Medical Campus

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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The Hubble telescope has shifted into one-gyro mode after months of technical issues − an aerospace engineering expert explains



theconversation.com – Panagiotis Tsiotras, Professor of Aerospace Engineering, Georgia Institute of Technology – 2024-06-17 07:13:24

The Hubble Telescope is nearing its 35th birthday.


Panagiotis Tsiotras, Georgia Institute of Technology

Imagine keeping a laser beam trained on a dime that's 200 miles away. Now imagine doing that continuously for 24 hours, while riding a merry-go-round. Seem difficult? Well, that's basically what the Hubble Space Telescope does.


After months of technical issues, NASA announced June 4 that Hubble would shift into one-gyroscope mode. This essentially means that the telescope will have to rely on just one of the several gyroscopes – devices that measure an object's orientation in space – it normally uses to track and follow objects in space.

Named after astronomer Edwin Hubble, the Hubble telescope launched in 1990 into low Earth orbit. Here, it's above Earth's atmosphere, which interferes with the observations from Earth-based telescopes. During its three decades of operation, it has provided us with stunning pictures of distant galaxies and scientists to look closer to the beginning of the universe.

Hubble takes clear, high-resolution pictures of billions of light years away. To collect enough photons – light “particles” – for a high-quality picture, it essentially acts as a very low-speed camera. It keeps its aperture – that is, the opening in the lens that lets light pass through – open for up to 24 hours to take a single picture.

Anyone who has taken a at a low shutter speed knows how difficult it is to avoid ending up with a blurry image. Hubble takes this to an extreme. It needs to stay pointed at the same distant point in space with an accuracy within a few milliarcseconds – where one milliarcsecond equals one 3,600,000th of a degree – for up to 24 hours. And it needs to keep this accuracy while orbiting the Earth at 17,000 miles per hour (27,000 kilometers per hour) through extreme heat and cold.


To keep track of its target and generate clear pictures, Hubble uses what aerospace engineers like me call attitude control . All spacecraft and aircraft have an attitude control system to them point in the right direction.

What's a gyro, anyway?

An attitude control system consists of a suite of sensors measuring the orientation of the spacecraft, a set of actuators – thrusters, reaction wheels or control moment gyroscopes – that move the spacecraft around, and a flight computer. The flight computer takes the measurements from the sensors and generates the commands for the actuators.

A diagram of the Hubble, showing three boxes labeled gyros, three labeled fine guidance sensors and two labeled reaction wheels in its interior.

The gyros work in tandem with fine guidance sensors and reaction wheels to control the telescope's orientation in space.


A gyroscope is a device that measures an object's attitude, or orientation in space. In other words, it measures how much the object has rotated from some fixed point. For Hubble to know where it's pointing to take a picture, it has to know where it is in space. It needs at least three gyros – one per axis.


Hubble initially had six gyros: three main ones and three more as extras. But after more than 30 years in orbit, four of the gyros have failed from complications related to aging.

From the two remaining gyros, NASA has reserved one as a backup, so Hubble is now operating with a single gyro. But if you need at least three gyros – one per axis – to know where you are, how can Hubble figure out where it is with only one gyro?

One of Hubble's gyroscopes.

The clever answer that NASA engineers came up with is actually very simple. You can use other sensors on the telescope, such as magnetometers and star sensors, to make up for the lack of gyros.

Gyro stand-ins

Magnetometers measure Earth's local magnetic field, which scientists understand pretty accurately. You can use the magnetometers to get a rough idea of the attitude with respect to the known magnetic field direction, pretty much the same way you use a compass. A three-axis magnetometer can take measurements of the strength and direction of the Earth's magnetic field as the satellite moves along its orbit to find its orientation in space.


Or you can use star trackers or sun sensors, which are much more accurate than magnetometers. These sensors use a map of the sky and align what they see with what's on the map to figure out where they are pointing.

By combining the star trackers, sun sensors, magnetometers and a single gyro, Hubble can maintain a pointing accuracy that is very close to the three-gyro configuration – although the one-gyro configuration will limit how fast Hubble can track objects in space.

Hubble has one of the most accurate pointing attitude control systems ever built, and it has provided people with stunning pictures of the early universe. But losing all but two gyros is just another reminder that Hubble's days are numbered.

Hubble's successor, the James Webb Space Telescope, launched on Dec. 25, 2021. It is stationed 1,000,000 miles (1,609,344 km) away from Earth at what is called the second Lagrange point (L2).


At this point, the telescope, the Earth and the Sun are always aligned, and the telescope's protective sun shield blocks the Sun's rays. This feature allows its infrared camera to operate at chilly temperatures to much better-quality pictures.

While the long-enduring Hubble's discoveries opened the universe to astronomers, Webb will allow us to look deeper into the cosmos than ever before.The Conversation

Panagiotis Tsiotras, Professor of Aerospace Engineering, Georgia Institute of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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