Scientists uncover key brain mechanism in salience processing

October 25, 2018

Scientists have discovered a new brain mechanism underlying salience processing that controls associative learning.

The salience of a stimulus is the state of being noticeable or important. Saliency detection is a key brain mechanism that facilitates learning and survival by enabling organisms to focus their limited attention resources on the most important event. The brain circuits underlying saliency detection had not previously been well understood.

A study carried out by Prof. ZHU Yingjie from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences, in collaboration with Prof. CHEN Xiaoke from Stanford University, uncovered the brain mechanism underlying salience processing. The results were published in Science as a research article on October 26.

By using fiber photometry and single-unit recording, the researchers found that neurons in the periventricular nucleus of the thalamus (PVT) are robustly activated by a variety of salient stimuli, including novel stimuli, reinforcing stimuli and their predicting cues. The responses were proportional to stimulus intensity, and a larger reward (punishment) could evoke a larger PVT response.

The salience of stimuli is not only determined by physical properties and behavioral relevance of the stimuli, but also depends on the internal homeostatic state of the animal. For example, water is a very salient stimulus when an animal is thirsty, but its saliency should decrease when an animal is in a sated state. Researchers found that PVT neuron responses to water and their predicting cues decrease after an animal had consumed a significant amount of water.

The salience of stimuli also depends on the external environment of the animal. For example, the saliency of water should decrease when a predator is present. By modulating the behavioral context, researchers showed that the PVT could dynamically track the salience of stimuli upon changes to the internal homeostatic state and external environment.

Researchers found that PVT salience is important for associative learning. Optogenetic suppression of the PVT during learning could significantly disrupt both appetitive and aversive learning.

The PVT can also be activated by internally generated emotional salience such as the disappointment associated with the omission of an expected reward. This omission response is important for extinction learning. Optogenetic suppression of the PVT can slow down extinction learning.

Prof. Robert C. Malenka, deputy director of the Stanford Neurosciences Institute, lauded the research by calling it "a very sophisticated and elegant study of how the brain processes and encodes the motivational importance or 'salience' of behaviorally significant stimuli." He expressed confidence that scientists studying brain mechanisms underlying adaptive and pathological behaviors in humans would "pay close attention to this work and begin exploring the role of this critical brain region, the PVT. "
-end-


Chinese Academy of Sciences Headquarters

Related Learning Articles from Brightsurf:

Learning the language of sugars
We're told not to eat too much sugar, but in reality, all of our cells are covered in sugar molecules called glycans.

When learning on your own is not enough
We make decisions based on not only our own learning experience, but also learning from others.

Learning more about particle collisions with machine learning
A team of Argonne scientists has devised a machine learning algorithm that calculates, with low computational time, how the ATLAS detector in the Large Hadron Collider would respond to the ten times more data expected with a planned upgrade in 2027.

Getting kids moving, and learning
Children are set to move more, improve their skills, and come up with their own creative tennis games with the launch of HomeCourtTennis, a new initiative to assist teachers and coaches with keeping kids active while at home.

How expectations influence learning
During learning, the brain is a prediction engine that continually makes theories about our environment and accurately registers whether an assumption is true or not.

Technology in higher education: learning with it instead of from it
Technology has shifted the way that professors teach students in higher education.

Learning is optimized when we fail 15% of the time
If you're always scoring 100%, you're probably not learning anything new.

School spending cuts triggered by great recession linked to sizable learning losses for learning losses for students in hardest hit areas
Substantial school spending cuts triggered by the Great Recession were associated with sizable losses in academic achievement for students living in counties most affected by the economic downturn, according to a new study published today in AERA Open, a peer-reviewed journal of the American Educational Research Association.

Lessons in learning
A new Harvard study shows that, though students felt like they learned more from traditional lectures, they actually learned more when taking part in active learning classrooms.

Learning to look
A team led by JGI scientists has overhauled the perception of inovirus diversity.

Read More: Learning News and Learning Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.