WINSTON-SALEM -- The brains of some people who read poorly -- especially people with dyslexia -- differ physiologically from normal readers, according to pioneering work at the Wake Forest University Baptist Medical Center.
Researchers tracking brain activity using a relatively new and sophisticated tool called Positron Emission Tomography (PET) found that differences in brain activity were greatest in a specific part of the brain called the thalamus.
The thalamus is less active in poor readers, said John R. Absher, M.D., assistant professor of neurology, who used both the PET measurements of brain metabolism and more traditional electrical measurements of brain activity to reach that conclusion. He reported his findings today at the Society for Neuroscience meeting in New Orleans.
Absher said the research "clearly related the thalamus to at least two stages of reading" and pointed to real physiological differences between good and poor readers.
"Our data are interesting because the thalamus is thought to be involved with the process of brain development," Absher said. "Genetic abnormalities affecting the thalamus have recently been identified in poor readers. Thalamic abnormalities may influence the development of many areas of the brain, including other brain areas (such as the temporal lobe) likely to be abnormal in poor readers."
In the study, Absher and his colleagues compared 20 poor readers with 20 normal readers to examine differences in both the electrical and metabolic activity of the brain.
The poor readers all had impairments in generating the correct sounds for written words and nonsense words.
The electrical activity and letter identification accuracy were measured while lower-case letters and non-letter shapes were randomly flashed on a computer screen for 30 minutes. "Differences in electrical activity and metabolism were related to specific parts of the brain and to specific stages of reading as a way to understand poor reading," Absher said.
The electrical activity was measured at 16 places on the scalp. The results pinpointed that the thalamus was less active on both sides of the brain.
Absher said the results agree with recent genetic research linking the thalamus with a form of poor reading known as developmental dyslexia. Microscopic studies also have shown abnormal thalamic structure in patients with developmental dyslexia.
Absher said the study could have important clinical implications by:
Promoting efforts to develop pre-clinical diagnosis of dyslexia using brain imaging. "Since the brain is better at reorganizing its structure early in life, it may be possible to enhance the effectiveness of reading programs by identifying potentially poor readers early in life, even before they begin to read."
Leading to an understanding of the genetics of reading.
Detailing the specific stages of reading and how the brain accomplishes reading.
Suggesting a potential mechanism for the disorganized brain structure seen in dyslexia.
"If our idea can be confirmed, it may be possible to discover the factors that lead to such brain abnormalities as seen in dyslexics," Absher said. "Only if these factors are understood can they be targeted for therapeutic intervention."
The team included two key researchers, Frank B. Wood, Ph.D., and D. Lynn Flowers, Ph.D., from a major dyslexia research program project at the Medical Center. The research was supported in part by the General Clinical Research Center, which in turn is supported by the National Institutes of Health.