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Tuesday, September 29, 2015

How does the brain determine what matters?

THE INSULA and the SALIENCE NETWORK 

: How does the brain determine what matters?

How does the brain determine what matters? According to a new scientific article, a brain structure called the insula is essential for selecting things out of the environment that are "salient" for an individual, and dysfunction of this system is linked to brain disorders such as autism, psychosis and dementia.
The SALIENCE NETWORK and the various aspect of the INSULA which is a key part of it are increasingly being found to be operative just about "everywhere" in an interesting balance with the DEFAULT MODE NETWORK, somehow directing or orchestrating our attention to what needs to be done and away from our internal processes.
In psychology and neuroscience, the term "salient" is used to describe a thing, person, place or event that stands out, or that is set apart from others.
First described by Greicius and Seeley in 2007, the salience network is thought to be central in prepping the brain for action, such as when a driver must respond to someone darting across the road or a student readies herself for a pop quiz. An object or event is salient if it is significant to an individual. The signals can come from inside the body, such as pain or hunger, or outside, such as the sound of a distant siren while driving in traffic.
http://www.wired.com/2013/12/the-will-to-persevere/
The findings show that the insular cortex is a complex and multi-purpose structure that can be separated into, at least, three separate regions with distinct functions. Specific subdivisions of the insular cortex, along with other cortical and subcortical regions, form a "salience network." Compromises to the integrity of this network can contribute to deficits in attention and affect, as well as social and cognitive processes.
In healthy people, the Default Mode Network and the Salience network appear to be tightly coupled. The default network is active when a person daydreams — but when something outside, such as an ambulance siren, pierces that sense of reflection, the salience network takes over. “It’s activated when you have to get rid of that internal focus and figure out what’s happening around you,” “To understand what’s going on, we need to think about how they work together.”
If you have to think about tiny regions of the brain all doing something different, it’s very hard to make sense of how activity fits together globally,” said David Sharp, a neurologist at the National Institute for Health Research in London who did the study described further below.
"We are constantly bombarded with stimuli from the environment that place demands on our attention," said author of the article. "The function of one of the insular cortex subdivisions is crucial for orchestrating activity in other brain regions that are important for guiding attention,"
See Also: Saliency, switching, attention and control: a network model of insula function. http://www.ncbi.nlm.nih.gov/pubmed/20512370
“Our brain is constantly bombarded by sensory information, and we have to score all that information in terms of how personally relevant it is for guiding our behavior,” said Seeley, a neurologist at the University of California, San Francisco, who was not involved in a new study. “The more salient something is, the more it captures our drive system, which directs behavior.”
In a rare study involving direct brain stimulation, Michael Greicius, a neurologist at Stanford University, and collaborators say they have uncovered direct evidence that a brain region known as the anterior midcingulate cortex and its surrounding network play a central role in motivation and a readiness to act.
The theory had been based on indirect data — until now. “It was a fortuitous opportunity, providing a rare piece of data that we can’t get from any other setting,” Greicius said. “It’s nice to have a human lend this first-person insight into what it feels like to have your salience network stimulated.
raise tantalizing questions about how differences in the network from one individual to the next contribute to differences in our ability to overcome challenges and cope with stress.
If you have to think about tiny regions of the brain all doing something different, it’s very hard to make sense of how activity fits together globally,” said David Sharp, a neurologist at the National Institute for Health Research in London.
brain is constantly bombarded by stimuli, and the relative salience of these inputs determines which are more likely to capture attention. A brain system known as the 'salience network', with key nodes in the insular cortices, has a central role in the detection of behaviourally relevant stimuli and the coordination of neural resources. Emerging evidence suggests that atypical engagement of specific subdivisions of the insula within the salience network is a feature of many neuropsychiatric disorders
At least part of the salience network’s role seems to be linked to something very basic: the fight or flight response. That response — an accelerated heart rate, dilated pupils and rising blood pressure, readying the body for action — may be orchestrated by the salience network
“I think it comes on line anytime there is a challenge to be met and allows the brain to marshal the body’s resources,” said Greicius. The fight or flight response would be an extreme example, “but low-level challenges still require marshaling of those physiologic resources,” he said.
Scientists don’t yet know the exact role the salience network plays in perseverance, but they do know that disrupting the network can have a profound effect. Rodents with damage to their version of the anterior cingulate give up more easily than others when trying to find food. And deterioration in the salience networks in frontotemporal dementia has been linked to lack of drive.
They theorize that paying too much attention to one’s thoughts may give them undue significance. “These disorders might be partially understood as conditions in which an excessive amount of salience is attributed to situations or stimuli that don’t merit that much attention,” Greicius said.
Too much activity in the salience network can also be problematic. Seeley and Greicius’s original study found that the people who reported the most anxiety before they entered the brain scanner also showed the strongest network connections; and hyperconnectivity in the network has been linked to autism.