How Brain Is Wired for Attention

University of Utah (U of U) medical researchers have uncovered a wiring diagram that shows how the brain pays attention to visual, cognitive, sensory, and motor cues. The research provides a critical foundation for the study of abnormalities in attention that can be seen in many brain disorders such as autism, schizophrenia, and attention deficit disorder.

University of Utah (U of U) medical researchers have 
uncovered a wiring diagram that shows how the brain 
pays attention to visual, cognitive, sensory, and motor
cues. The research provides a critical foundation for 
the study of abnormalities in attention that can be seen 
in many brain disorders such as autism, 
schizophrenia, and attention deficit disorder. 
(Credit: iStockphoto/Sebastian Kaulitzki)

The study appears Nov. 1, 2010, online in the Proceedings of the National Academy of Sciences (PNAS).
"This study is the first of its kind to show how the brain switches attention from one feature to the next," says lead researcher Jeffery S. Anderson, M.D., Ph.D., U of U assistant professor of radiology. Anderson and his team used MRI to study a part of the brain known as the intraparietal sulcus. "The brain is organized into territories, sort of like a map of Europe. There are visual regions, regions that process sound and areas that process sensory and motor information. In between all these areas is the intraparietal sulcus, which is known to be a key area for processing attention," Anderson says. "We discovered that the intraparietal sulcus contains a miniature map of all of these territories. We also found an organized pattern for how control regions of the brain connect to this map in the intraparietal sulcus. These connections help our brain switch its attention from one thing to another."
In addition, scientists discovered that this miniature map of all the things one can pay attention to is reproduced in at least 13 other places in the brain. They found connections between these duplicate maps and the intraparietal sulcus. Each copy appears to do something different with the information. For instance, one map processes eye movements while another processes analytical information. This map of the world that allows us to pay attention may be a fundamental building block for how information is represented in the brain.
"The research uncovers how we can shift our attention to different things with precision," says Anderson. "It's a big step in understanding how we organize information. Furthermore, it has important implications for disease. There are several diseases or disorders where attention processing is off, such as autism, attention deficit disorder, and schizophrenia, among others. This research gives us the information to test theories and see what is abnormal. When we know what is wrong, we can talk about strategies for treatment or intervention."
Deborah Yurgelun-Todd, Ph.D., professor of psychiatry in the U of U Schoold of Medicine and an investigator with the U of U Brain Institute and the Utah Science Technology and Research Initiative (USTAR), was the principal investigator and senior author of the study. The research was funded by a National Institutes of Health grant from the National Institute on Drug Abuse.

Brain Regions Can Switch Functions in Young

A new paper from MIT neuroscientists, in collaboration with Alvaro Pascual-Leone at Beth Israel Deaconess Medical Center, offers evidence that it is easier to rewire the brain early in life. The researchers found that a small part of the brain's visual cortex that processes motion became reorganized only in the brains of subjects who had been born blind, not those who became blind later in life.

Scientists offer evidence that it is easier to rewire the 
brain early in life. Researchers found that a small part 
of the brain's visual cortex that processes motion became
reorganized only in the brains of subjects who had been 
born blind, not those who became blind later in life.
(Credit: iStockphoto/Vasiliy Yakobchuk)

The new findings, described in the Oct. 14 issue of the journal Current Biology, shed light on how the brain wires itself during the first few years of life, and could help scientists understand how to optimize the brain's ability to be rewired later in life. That could become increasingly important as medical advances make it possible for congenitally blind people to have their sight restored, said MIT postdoctoral associate Marina Bedny, lead author of the paper.

In the 1950s and '60s, scientists began to think that certain brain functions develop normally only if an individual is exposed to relevant information, such as language or visual information, within a specific time period early in life. After that, they theorized, the brain loses the ability to change in response to new input.

Animal studies supported this theory. For example, cats blindfolded during the first months of life are unable to see normally after the blindfolds are removed. Similar periods of blindfolding in adulthood have no effect on vision.

However, there have been indications in recent years that there is more wiggle room than previously thought, said Bedny, who works in the laboratory of MIT assistant professor Rebecca Saxe, also an author of the Current Biology paper. Many neuroscientists now support the idea of a period early in life after which it is difficult, but not impossible, to rewire the brain.

Bedny, Saxe and their colleagues wanted to determine if a part of the brain known as the middle temporal complex (MT/MST) can be rewired at any time or only early in life. They chose to study MT/MST in part because it is one of the most studied visual areas. In sighted people, the MT region is specialized for motion vision.

In the few rare cases where patients have lost MT function in both hemispheres of the brain, they were unable to sense motion in a visual scene. For example, if someone poured water into a glass, they would see only a standing, frozen stream of water.

Previous studies have shown that in blind people, MT is taken over by sound processing, but those studies didn't distinguish between people who became blind early and late in life.

In the new MIT study, the researchers studied three groups of subjects -- sighted, congenitally blind, and those who became blind later in life (age nine or older). Using functional magnetic resonance imaging (fMRI), they tested whether MT in these subjects responded to moving sounds -- for example, approaching footsteps.

The results were clear, said Bedny. MT reacted to moving sounds in congenitally blind people, but not in sighted people or people who became blind at a later age.

This suggests that in late-blind individuals, the visual input they received in early years allowed the MT complex to develop its typical visual function, and it couldn't be remade to process sound after the person lost sight. Congenitally blind people never received any visual input, so the region was taken over by auditory input after birth.

"We need to think of early life as a window of opportunity to shape how the brain works," said Bedny. "That's not to say that later experience can't alter things, but it's easier to get organized early on."

Bedny believes that by better understanding how the brain is wired early in life, scientists may be able to learn how to rewire it later in life. There are now very few cases of sight restoration, but if it becomes more common, scientists will need to figure out how to retrain the patient's brain so it can process the new visual input.

"The unresolved question is whether the brain can relearn, and how that learning differs in an adult brain versus a child's brain," said Bedny.

Bedny hopes to study the behavioral consequences of the MT switch in future studies. Those would include whether blind people have an advantage over sighted people in auditory motion processing, and if they have a disadvantage if sight is restored.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.