Research Advances Improve Outlook for Reading Disorders

by James Cavuoto, editor

Recent advances in our understanding of brain processes involved with reading and language learning have created an opportunity for new neurotech strategies for treating reading disorders. About 10 percent of the U.S. population suffers from dyslexia, a condition that makes learning to read difficult.

One of the first neurotech firms to target language learning disorders was Scientific Learning, Inc., an Oakland, CA software firm founded by cortical plasticity pioneer Michael Merzenich. Merzencich, an early researcher in the cochlear implant field, discovered a neural circuit in primary auditory cortex involved with frequency discrimination that is faulty in children with dyslexia. Scientific Learning’s software targets this task—and that brain region—in a training regimen that improves phoneme detection and reading ability.

A combination of brain scans and reading tests has revealed that several regions in the brain are responsible for allowing humans to read. Recent findings open up the possibility that individuals who have difficulty reading may only need additional training for specific parts of the brain—targeted therapies that could more directly address their individual weaknesses.

“Reading is a complex task. No single part of the brain can do all the work,” said Qinghua He, postdoctoral research associate at the USC Brain and Creativity Institute and the first author of a recent study published in the Journal of Neuroscience. The study looked at the correlation between reading ability and brain structure revealed by fMRI scans of more than 200 participants.

The study first collected data for seven different reading tests of a sample over 400 participants. These tests were aimed to explore three aspects of their reading ability: phonological decoding ability; form-sound association; and naming speed. Each of these aspects, it turned out, was related to gray matter volume in different parts of the brain.

The MRI analysis showed that phonological decoding ability was strongly connected with gray matter volume in the left superior parietal lobe; form-sound association was strongly connected with the hippocampus and cerebellum; and naming speed lit up a variety of locations around the brain.

Dyslexia is usually diagnosed around second grade, but the results of a recent study from MIT could help identify those children before they even begin reading. The study, done with researchers at Boston Children’s Hospital, found a correlation between poor pre-reading skills in kindergartners and the size of a brain structure that connects two language-processing areas. Previous studies showed that in adults with poor reading skills, the arcuate fasciculus is smaller and less organized than in adults who read normally.

The researchers focused on three white-matter tracts associated with reading skill: the arcuate fasciculus, the inferior longitudinal fasciculus, and the superior longitudinal fasciculus. When comparing the brain scans and the results of several different types of pre-reading tests, the researchers found a correlation between the size and organization of the arcuate fasciculus and performance on tests of phonological awareness.