The Times Australia
The Times World News

.
The Times Real Estate

.

Researchers trained mice to control seemingly random bursts of dopamine in their brains, challenging theories of reward and learning

  • Written by David Kleinfeld, Professor of Physics and Neurobiology, University of California San Diego

The Research Brief[1] is a short take about interesting academic work.

The big idea

My colleagues and I recently found that we were able to train mice to voluntarily increase the size and frequency of seemingly random dopamine impulses in their brains[2]. Conventional wisdom in neuroscience has held that dopamine levels change solely in response to cues from the world outside of the brain. Our new research shows that increases in dopamine can also be driven by internally mediated changes within the brain.

Dopamine is a small molecule found in the brains of mammals and is associated with feelings of reward and happiness. In 2014, my colleagues and I invented a new method to measure dopamine in real time in different parts of the brains of mice[3]. Using this new tool, my former thesis student, Conrad Foo, found that neurons in the brains of mice release large bursts of dopamine – called impulses – for no easily apparent reason[4]. This occurs at random times, but on average about once a minute.

Pavlov was famously able to train his dogs to salivate at the sound of a bell, not the sight of food. Today, scientists believe that the bell sound caused a release of dopamine to predict the forthcoming reward[5]. If Pavlov’s dogs could control their cue-based dopamine responses with a little training, we wondered if our mice could control their spontaneous dopamine impulses. To test this, our team designed an experiment that rewarded mice if they increased the strength of their spontaneous dopamine impulses. The mice were able to not only increase how strong these dopamine releases were, but also how often they occurred. When we removed the possibility of a reward, the dopamine impulses returned to their original levels.

Researchers trained mice to control seemingly random bursts of dopamine in their brains, challenging theories of reward and learning Pavlov famously showed that cues – like food or a bell – produce a response, but new mouse research shows that dopamine impulses can occur in the absence of a cue. Maxxl²/WikimediaCommons, CC BY-SA[6][7]

Why it matters

In the 1990s, neuroscientist Wolfram Schultz discovered that an animal’s brain will release dopamine if the animal expects a reward[8], not just when receiving a reward. This showed that dopamine can be produced in response to the expectation of a reward, not just the reward itself – the aforementioned modern version of Pavlov’s dog. But in both cases dopamine is produced in response to an outside cue of some sort. While there is always a small amount of random background dopamine “noise” in the brain[9], most[10] neuroscience research[11] had not considered[12] the possibility of random dopamine impulses large enough to produce changes in brain function and memory.

Our findings challenge the idea that dopamine signals are deterministic – produced only in response to a cue – and in fact challenge some fundamental theories of learning which currently have no place for large, random dopamine impulses. Researchers have long thought that dopamine enables animals to determine which cues can guide them toward a reward. Often a sequence of cues is involved – for example, an animal may be attracted to the sound of running water that only later leads to the reward of drinking.

Our observation of spontaneous bursts of dopamine – not ones that occur in response to a cue – don’t fit neatly with this framework. We suggest that large spontaneous impulses of dopamine could break these chains of events and impair an animal’s ability to connect indirect cues to rewards. The ability to actively influence these dopamine bursts could be a mechanism for mice to minimize this hypothesized problem in learning, but that remains to be seen.

What still isn’t known

My colleagues and I still need to connect the current findings with parts of the brain known to signal with dopamine[13]. In terms of behavior – such as foraging or navigating a maze in the laboratory – what is the effect of spontaneous impulses on the ability to learn? It is tempting to wonder whether spontaneous impulses could act as a false expectation of reward. It may be the case that spontaneous impulses give animals hope that a reward of some sort is “out there.” We plan to test whether there is a causal link between the spontaneous impulses of dopamine and mice venturing out to explore their surroundings. Finally, it is unknown whether the impulses help or hinder mental ability. Since the dopamine receptors in the cortex[14] are the same receptors that are overexpressed in schizophrenia[15], we wonder whether there is a connection between spontaneous impulses and mental health.

[Over 110,000 readers rely on The Conversation’s newsletter to understand the world. Sign up today[16].]

Read more https://theconversation.com/researchers-trained-mice-to-control-seemingly-random-bursts-of-dopamine-in-their-brains-challenging-theories-of-reward-and-learning-165727

The Times Features

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

LayBy Shopping