Brain reprograms itself after stroke--Functional MRI reveals brain's innate plasticity and charts a direction for rehabilitation

February 17, 2001

Functional imaging of the brain demonstrates that this highly complex organ adapts to injury by redistributing its cognitive workload across established neural networks and recruiting local cortical areas to fill in for lost functions like speech and language comprehension.

"Functional MRI [magnetic resonance imaging] indicates that the dogma that some areas of the brain are not important for normal function is clearly fallacious," said Dr. Keith Thulborn, director of MR research at the University of Illinois at Chicago at the annual meeting of the American Association for the Advancement of Science in San Francisco. "Loss of any brain tissue is likely to compromise the reserve capacity of many large-scale neurocognitive networks that will ultimately be reflected in the performance of more difficult tasks or recovery from subsequent disease processes."

Watching the brain at work with a very-high-field MRI scanner, Thulborn has mapped a two-stage recovery process in patients who lost their language skills after strokes. In one patient suffering from damage to Wernicke's area (the region in the left cortex that controls the understanding of language), functional MRI showed that the brain initially recouped by allocating speech comprehension to an area on the opposite side of the brain. Over time, while Wernicke's area remained damaged, an adjacent area took on this cognitive task.

The ability of the brain to maintain performance by recruiting undamaged portions of the cortex may suggest why functional recovery can occur even after large strokes, said Thulborn.

One key factor in recovery time, Thulborn suggested, is whether white matter has been damaged. White matter consists of myelinated neuronal axons that serve as cables linking the different areas of the cortex. When these are injured, vital connections needed to allocate functions elsewhere are lost.

"The involvement of white matter tracts portends slower and reduced recovery," said Thulborn. "This may reflect reduced capacity to redistribute workload when the connectivity through white matter is disrupted."

While functional MRI has been largely used in research to map brain functions, it is just beginning to find clinical applications. At the UIC Medical Center, Thulborn is collaborating with other physicians, psychologists and therapists to use the technology in designing and monitoring rehabilitation programs aimed at restoring lost cognitive and motor skills. In this role, Thulborn said, functional MRI can guide and refine therapies to enhance the brain's innate plasticity.

The very-high-field MRI scanner works by picking up faint magnetic signals in the underlying tissue. As neurons become increasingly active in specific regions of the brain, blood flow surges to those regions and blood volume expands.

In the process, deoxygenated blood is replaced with oxygenated blood, the two differing in their magnetic properties. The MRI scanner is able to detect this magnetic change, although minute, because of the scanner's high magnetic field strength: 3.0 Tesla, twice that of MRI scanners more commonly deployed in clinical settings. (A Tesla is equivalent to 10,000 gauss; the magnetic field strength of Earth is less than one gauss.) Cross-sectional images are made through the entire brain to create a three-dimensional view. The images must be run through a series of statistical programs so that they can be correctly interpreted.

To obtain images of the working brain, patients are placed on a table and moved into the center of the magnet. The images are taken while patients are engaged in a set of cognitive tasks devised to correlate functional activities with specific areas of the brain. To map the language comprehension network of the brain, for example, patients are given sentences of varying complexity to read and asked to answer true/false questions by pressing a finger switch. To map the motor and sensory areas, patients simply tap a finger.

Thulborn cautioned that these cognitive tasks must be carefully selected if they are to be of value in answering clinical questions. Moreover, they need to be "robust," or reproducible, and appropriate to the patient's level of education and cognitive and motor abilities. "Careful attention to matching the skills of each patient to the stimulus task is required to avoid variable performance that may alter the functional mapping," said Thulborn.
-end-
For more information about the University of Illinois at Chicago, visit www.uic.edu.

University of Illinois at Chicago

Related Language 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.

How effective are language learning apps?
Researchers from Michigan State University recently conducted a study focusing on Babbel, a popular subscription-based language learning app and e-learning platform, to see if it really worked at teaching a new language.

Chinese to rise as a global language
With the continuing rise of China as a global economic and trading power, there is no barrier to prevent Chinese from becoming a global language like English, according to Flinders University academic Dr Jeffrey Gil.

'She' goes missing from presidential language
MIT researchers have found that although a significant percentage of the American public believed the winner of the November 2016 presidential election would be a woman, people rarely used the pronoun 'she' when referring to the next president before the election.

How does language emerge?
How did the almost 6000 languages of the world come into being?

New research quantifies how much speakers' first language affects learning a new language
Linguistic research suggests that accents are strongly shaped by the speaker's first language they learned growing up.

Why the language-ready brain is so complex
In a review article published in Science, Peter Hagoort, professor of Cognitive Neuroscience at Radboud University and director of the Max Planck Institute for Psycholinguistics, argues for a new model of language, involving the interaction of multiple brain networks.

Do as i say: Translating language into movement
Researchers at Carnegie Mellon University have developed a computer model that can translate text describing physical movements directly into simple computer-generated animations, a first step toward someday generating movies directly from scripts.

Learning language
When it comes to learning a language, the left side of the brain has traditionally been considered the hub of language processing.

Learning a second alphabet for a first language
A part of the brain that maps letters to sounds can acquire a second, visually distinct alphabet for the same language, according to a study of English speakers published in eNeuro.

Read More: Language News and Language 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.