Dyslexia and fMRI brain imaging

The Yale Center for Dyslexia and Creativity’s research laboratory, under the guidance of Dr Sally Shaywitz (Professor in Learning Development and Co-director of the center) was one of first to image the dyslexic brain using functional magnetic resonance imaging (fMRI). The laboratory has now imaged several thousand children and adults as they read.

fMRI is similar to MRI (often used to investigate headaches or bone injuries), but uses more sophisticated hardware and software that allows it to capture brain changes – mainly blood flow – as a person performs a specific cognitive task, for example reading. This technology has revolutionized understanding of reading and dyslexia.

Generally, the left brain controls linguistic functioning, and the right brain controls visual processing. Dr Shaywitz’s research shows these aspects may be disrupted or located differently in the dyslexic brain. Her analysis of data, using fMRI from around the world, indicates three neural systems used for reading, all in the left side of brain. In the dyslexic brain, disruption was observed in the two neural systems in the back of the brain. Thus a ‘neural signature’ for dyslexia has been observed.

Imaging also reveals compensatory overactivation in other parts of the reading system. The compensatory neural systems allow a dyslexic person to read more accurately. However, the critical visual word-form area remains disrupted and difficulties with rapid, fluent, automatic reading persist. The dyslexic continues to read slowly. In addition, neurobiological evidence is beginning to emerge indicating that many dyslexics are not able to make good use of sound-symbol linkages as they mature, and instead, they come to rely on memorized words.

A recent fMRI study also demonstrates the importance of memory systems in dyslexic readers. Together, these recent neurobiological findings suggest that as dyslexic children mature, neural systems supporting word memorization develop, rather than the systems supporting sound-symbol linkages and automatic reading that are observed in typical readers.

Functional imaging has been helpful in demonstrating that the neural systems for reading are malleable, and that the disruption in these systems in young struggling readers can be modified by an effective reading intervention. Compared to struggling readers who received other types of intervention, children who received an evidence-based application of the alphabetic principle not only improved their reading but, compared to pre-intervention brain imaging, demonstrated increased activation in the neural systems for reading. This data has important implications in teaching children to read: the provision of an evidence-based reading intervention at an early age improves reading and facilitates the development of those neural systems necessary for reading.

For more on this visit Dr Shaywitz’s knol – Dyslexia: The science of reading and dyslexia

To find out more about her other areas of research click here.