The answers to these questions are, respectively: you can, you would, and no! Modern neuroimaging has made it possible to “see” inside living, performing human brains. Using high-tech imaging tools, scientists have discovered that dyslexic brains do function in atypical ways consistent with the structural differences discovered nearly two decades ago. Finally, these are findings from the pages of scientific journals, not from science-fiction literature.
Neuroimaging provides a computer-analyzed view of how the brain looks and functions, showing which areas “are activated” (i.e., working hard) and which are not. We can watch the brain while it performs complex cognitive activities and while it is at rest, though it never really rests. While technological advances promise ever-sharper images, today’s neuroimaging techniques and computers already provide an arresting view of the brains of people with dyslexia. There are new findings on subtle structural differences, but the most intriguing findings concern functional attributes – how these brains work differently.
Dyslexia: Distinct Patterns of Brain Activity
Studies from around the world show a distinctly different pattern of brain activity in subjects with dyslexia as compared to people without dyslexia.
Neuroimaging studies from the United States, Japan, Germany, Italy, and other countries compared impaired (dyslexic) readers to unimpaired (control) readers ranging in age from 8 to 54. A variety of imaging techniques (fMRI, PET, MEG, MSI) monitored subjects’ brain activity. The most commonly used technique, fMRI, is safe and noninvasive and uses radio waves and magnetic fields to show blood flow in areas of the right and left hemispheres. Areas with increased blood flow are hard at work and show increased “activation.”
In these studies, subjects performed phonological-processing tasks (e.g., silent reading, rhyming, or pronouncing words and nonsense words). Some consistent findings emerged. The first is that during these language-based tasks, key areas of the language network in the left temporal, parietal, and occipital lobe “under-activated” in people with dyslexia, while left frontal areas “over-activated.” The second finding is that, in subjects with dyslexia, certain right-hemisphere areas “over-activated.”
What do these findings mean? In most people, left-hemisphere areas specialize in language and “activate” on language tasks, reflecting a specialized brain design that, in general, promotes efficiency. However, these new studies showed the brains of subjects with dyslexia function more bilaterally – in other words, they use areas in both hemispheres for language tasks, usually a less efficient mode for processing sequential information and certain language skills.
Bilateral and Neurocompensation
The increased activity in both the left-hemisphere frontal area and in areas of the right hemisphere may reflect compensatory mechanisms working to bypass deficiencies in left-hemisphere language areas. Neural compensation is a good strategy for circumventing specific structural and functional shortcomings, a phenomenon well-known in cerebral-stroke patients who learn to accommodate to an injury by transferring function from damaged to intact regions of the brain. A similar but developmentally unique phenomenon appears to be at work in dyslexia, though the compensation mechanism may be imperfect and inefficient, not entirely correcting the hallmark phonological difficulties often found in people with dyslexia.
Bilateral hemisphere activity also may relate to the structural symmetry in dyslexic brains. Areas in the right and left hemisphere of people with dyslexia are more symmetrical, more like mirror images, whereas these areas in most people are asymmetrical.
Educational Intervention May Change Brain Networks
A number of laboratories are working on documenting brain activity changes in people with dyslexia after educational intervention. Initial results are intriguing.
A substantial body of research demonstrates that structured-language programs effectively teach literacy skills to people with dyslexia, begging the question, do their brains change in response to this intervention and function more like unimpaired readers? Neuroimaging should reveal such a change, if it occurs.
Indeed, it appears that as struggling readers begin acquiring literacy skills, their brains do exhibit “activation patterns” similar to those of non-impaired readers. Does this mean the basic anatomical structure of the dyslexic brain changes? No. The fundamental structure does not change. But functional capacity may improve in two ways: 1) formation of new neural connections and 2) increased synaptic numbers and efficiency. Think of these changes like a computer upgrade – enhancing capacity to operate efficiently, to process complex sequential and linear information, and to improve memory storage and retrieval. For a child with dyslexia, these functional enhancements may mean the difference between success or failure in learning to read.
Implications of Brain Research
Already, we have learned the brains of subjects with dyslexia show characteristic and distinct functional differences compared to controls – less engagement of posterior left-hemisphere language areas and more bilateral processing. These findings are consistent with earlier findings from microscopic analysis of autopsied brains, showing structural variation in left hemisphere language areas and symmetry. We also have learned that environment can play a modifying role in dyslexia. The brains of subjects with dyslexia can change in response to structured-language educational intervention, functioning more like the brains of non-impaired readers. This last finding is compelling, but not surprising, and validates decades of clinical observations and reading research.
This finding also sheds light on implications that may transform education as we know it. Advancements in neuroimaging promise ever-sharper insights into the mysteries of the brain, allowing us to investigate more refined and targeted questions. Can neuroimaging studies become more precisely prescriptive, delineating which students do and do not show changes after specific interventions? Perhaps. What can we learn about the brains of people who have dyslexia in their family or who have certain genetic markers? What patterns will we see in the brains of people with excellent spatial skills, visual or auditory difficulties, or AD/HD? This is potent stuff. When we can answer critical questions like these, we may be able to prescribe educational interventions with scientific precision.
When might this prescriptive-teaching vision become a reality? Don’t plan on booking imaging appointments for Johnny or Jane in the near future. However, we are on the threshold of determining whether or not specific kinds of interventions work for specific kinds of learners. Imaging is highly statistical and, at this point, best analyzes the brain behaviors of groups of subjects, not an individual subject. However, Johnny and Jane will benefit if they are identified as members of a particular group of learners shown by neuroimaging to respond to a specific approach.
Neuroimaging is not a panacea, only a tool. There always will be children who struggle to learn to read, independent of their general cognitive abilities. Educators will struggle to find the most effective methods for teaching these children. Neuroimaging, even as it advances, will not eliminate these struggles; but it will help reduce them, significantly. Is this a scenario from the pages of science fiction literature? I think not. It is a likely outcome of a research agenda that partners neuroscientists and educators to unleash learning potential in powerful new ways. But to translate that vision into reality – to go beyond science fiction, even beyond scientific findings – requires educators, researchers, and policy makers to work together. Maybe, to dream together, too. The possibilities shrink or expand with our vision.
Technical aspects of neuroimaging are complex, and like everything related to the brain, straightforward questions yield complicated answers inspiring additional questions and ever-more complex answers. Nevertheless, neuroimaging has furnished important insights about the brain and dyslexia. For this discussion, I have summarized, and in some cases, simplified detail to highlight salient points. For those who wish to explore more technical and complex information, sources for additional reading are provided below.
- Functional Disruption in the Organization of the Brain for Reading in Dyslexia
by S E. Shaywitz , B. A. Shaywitz , K. R. Pugh, R. K. Fulbright, R. T. Constable, W. E. Mencl, D. P. Shankweiler, A. M. Liberman, P. Skudlarski, J. M. Fletcher, L. Katz, K. E. Marchione, C. Lacadie, C. Gatenby, and J. C. Gore in Proceedings of the National Academy of Sciences of the United States of America, Vol. 95, Issue 5, March 3, 1998
- Cerebral Mechanisms Involved in Word Reading in Dyslexic Children: A Magnetic Imaging Approach
by P.G.Simos, J.I. Breier, J.M. Fletcher, E. Bergman, and A.C. Papanicolau in Cerebral Cortex 2000; 10:pp. 809-816
- Developmental Dyslexia: Four Consecutive Cases with Cortical Anomalies
by A. M. Galaburda, G. F. Sherman, G. D. Rosen, F. Aboitiz, N. Geschwind in Annals of Neurology 1985;18:pp. 222-233.
- Dyslexia: Cultural Diversity and Biological Unity
by E. Paulesu, et al Science March 16, 2001; 291: pp. 2165-2167. Reprints can be ordered.