Until recently, there were two competing theories regarding how the structure of the brain contributes to reading abilities, and it seemed that one or the other had to be true, not both. But a new study seems to show that they could both actually have some foundation in fact.
Phonological processing is the ability to convert written symbols into speech sounds – the ability to read out loud. For individuals with dyslexia and related conditions, this task can be immensely problematic. Researchers have long known that brain asymmetry appears to play a role in a person’s capability to read aloud effectively, but the question of what exactly the nature of that link is remains.
Researchers used MRI scans to monitor each participant’s cerebral asymmetry with a system called persistent homology. When they focused on the most asymmetric region of each individual’s brain, those with more left-brain asymmetry tended to do better at reading pseudo-words than other participants did. This supports the first theory, also known as the cerebral lateralization hypothesis.
However, on the other hand, when the researchers considered specific regions of the brain – such as a motor planning region called Brodmann Area 8 and a performance monitoring region called the dorsal cingulate – greater left-brain asymmetry seemed to be more connected with only average reading levels. This evidence supports the canalization hypothesis.
“Our findings indicate that, at a population level, structural brain asymmetries are related to the normal development of a speech sound processing ability that is important for establishing proficient reading,” says Mark Eckert, lead researcher of the study, which was conducted at the Medical University of South Carolina.
So it would seem that, as tends to happen on occasion, two things we thought were mutually exclusive can actually coexist rather peacefully. We hope that this new data helps researchers keep open minds in future studies and that more will soon be discovered about how brain structures impact reading abilities and other cognitive tasks.
For now, we hope this information is encouraging for people with dyslexia, autism, and other disorders. Don’t take your reading skills too personally, as you may not have as much control over them as you once thought!