Neural activity differences between average readers and dyslexics during reading tasks

Neural activity differences between average readers and dyslexics during reading tasks

First Author: Noor Al Dahhan -- Massachusetts Institute of Technology
Additional authors/chairs: 
John R. Kirby; Donald C. Brien; Rina Gupta; Allyson Harrison; Douglas P. Munoz
Keywords: Neuroimaging, Eye movements, Rapid naming, Dyslexia, Reading
Abstract / Summary: 

Purpose
Although reading is an important skill, it remains controversial how it develops and how dysfunctions lead to reading difficulties. To further understand the processes that are involved during reading, we combined functional magnetic resonance imaging (fMRI) with eye tracking to investigate the processes underlying performance during naming speed (NS) tasks.

Methods
We recruited 18 average readers and 16 readers with dyslexia (ages 21-26), and employed an fMRI block design consisting of letter and object NS tasks in which the stimuli were either phonologically and/or visually similar to one another, while participants’ eye movements and articulations were simultaneously recorded. We examined how these manipulations influenced behavioral performance and whether they resulted in differences in neural activation.

Results
Compared to average readers, readers with dyslexia had poorer behavioral performance on all tasks and this was reflected with an increase in neural activity within the reading network. However, unlike average readers who relied on the left-dominant reading network to complete the tasks, readers with dyslexia had greater bilateral activation and recruited regions involved with memory to presumably compensate for their reading disability. Furthermore, manipulations to the letter and object NS tasks differentially activated the reading network. There was greater neural activity and poorer behavioral performance when stimuli were both visually and phonologically similar to one another compared to the single stimuli manipulation conditions.

Conclusion
These findings further our understanding of the neural substrates required for reading, and indicate that NS tasks recruit the same network of neural structures that are involved in reading and target key regions within this network. These results also further our understanding of the differences in activation within these regions between average readers and readers with dyslexia.