Using Magnetic Source Imaging in our laboratory at the University of Texas in Houston, we have obtained evidence of a brain activity pattern that is peculiar to dyslexic children and dramatically different than the patterns of normal readers. Thus far, we have examined 30 children with documented dyslexia and an equal number of normal readers. In virtually all cases the pattern is almost identical, showing greater activity in certain areas of the right hemisphere (i.e. the right half of the brain), exactly opposite to those activated in the left hemisphere of normal readers during reading. In addition, the temporal course of activation (i.e., the order in which different parts of the brain work together during reading) is dramatically different between dyslexics and normal readers.

Fig 1. Three dimensional views of the surface of the brain of a dyslexic (top set of images) and a non-dyslexic child (lower set of images) during reading. Note the nearly complete absence of activity in parts of the left half of the brain (blue square) in the dyslexic reader coupled with a wealth of activity in mirror areas of the opposite half of the brain. The opposite is true in the case of the normal, non-dyslexic child.

These findings are interesting for a number of reasons: (1) Information regarding aberrant brain function was made available for individuals rather than on a group basis. This can have a significant impact from a clinical point of view, in the treatment of this condition, since MSI can serve as an objective method to follow up specific intervention strategies; (2) This was the first functional brain imaging study on dyslexia that actually examined dyslexic children rather than adults diagnosed with the disorder. It is known that, with years of training and education, dyslexics may develop compensatory strategies for learning to read. Therefore, we assessed brain function in young children who are beginning to read. The goal of the research program is to determine what goes wrong in the brain to impede this process; (3) Our findings may have important theoretical implications by providing a more complete picture of the mechanism responsible for dyslexia.
Ongoing studies now assess directly the utility of MSI procedures for detecting changes in brain function in the course of education programs that teach children basic reading skills, such as the ability to mentally manipulate the sounds of the English language and to learn associations between printed letters and their pronunciation. In the context of these studies, we have collected preliminary data from four dyslexic children before and after participating in intensive eight-week-long intervention programs that emphasize training in phonological awareness skills. Results showed marked improvement in reading fluency. The profile of all four children shows a dramatic increase in left temporoparietal activation, which renders it nearly indistinguishable from the profiles of normal readers.

Fig 2. Activation maps from another participant during pseudoword reading, before and after intervention. Note the dramatic increase in left temporoparietal activation (which is also clearly evident in Fig.1) associated with the drastic improvement in phonological decoding skills.

Only in the last decade or so, with the emergence of functional imaging methods, it has become possible to detect, localize, and quantify brain activity associated with cognitive function. Obtaining high fidelity images of regional brain activity is the first step in understanding the brain mechanisms that are responsible for such functions. Prior to these developments, the only methods available to provide accurate information regarding brain function were either invasive (i.e., involving the placement of recording or stimulating electrodes in a patient's brain) or limited in scope (such as the study of the cognitive effects of tumors and stroke). However, before these new non-invasive brain imaging techniques can be established as equal partners of traditional methods in the study of the mechanisms of cognitive function, we must show that they are capable of at least the same level or accuracy as these older methods.

This standard has lately been achieved for MSI. In a series of clinical studies, carried out in the Magnetic Source Imaging Laboratory at the University of Texas Medical School, functional imaging data were compared directly, and with excellent agreement, with the results of invasive functional brain mapping techniques considered as the "gold standards" in the field. It was only then that we decided to explore potential applications of the technique to the study of the brain mechanisms responsible for cognitive functions, such as reading, as well as for disorders believed to have a neurological basis, such as dyslexia.

Fig 3. Positioning a patient for MSI testing in the whole head neuromagnetometer at the University of Texas.

Fig 4. Distribution of magnetic fields on the head surface as measured by the whole-head neuromagnetometer.

Fig 5. Brain activation profile obtained during word reading in a normal adult reader. Dark arrows demonstrate the temporal progression of activation from areas involved in visual analysis of the word to areas believed to be involved in determining how the word is pronounced and what it means.

The reading protocols we have developed are easy to implement and brief in duration to facilitate use with young children. The laboratory is staffed by experienced psychologists and technicians. The reading research is coordinated by the faculty members in the Division of Clinical Neurosciences: Prof. Andrew Papanicolaou (Director), Dr. Panagiotis Simos, Dr. Shirin Sarkari, and Dr. Rebecca Billingsley-Marshall. It is part of a collaboratory project with the Center of Academic and Reading Skills (Department of Pediatrics) and two leading researchers in the field of Learning Disabilities, Drs. Barbara Foorman and Jack Fletcher.

Center for Clinical Neurosciences
Children's Learning Institute
University of Texas Houston Health Science Center
1333 Moursund Street Ste H114
Houston, Texas 77030