Structural Brain Correlates of Poor Reading Comprehension

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Cognitive Neuroscience

Background:

• Poor comprehenders (PCs) have typical word reading skills but struggle with reading comprehension.
• The neurobiological underpinnings of poor reading comprehension are less understood than those of poor decoding.
• Previous studies found limited gray matter differences in PCs.

Purpose of the Study:

• To investigate the neuroanatomical differences in poor comprehenders compared to poor decoders and typical readers.
• To quantify cortical morphometric features and white matter integrity in PCs.
• To determine if distinct neuroanatomy is associated with poor reading comprehension.

Main Methods:

• Analyzed imaging data from 2,100 children (aged 8-16 years, 1,200 with imaging).
• Computed gray matter volume, cortical thickness, and surface area.
• Assessed white matter integrity using mean diffusivity, fractional anisotropy, neurite orientation, and neurite density.

Main Results:

• Identified small but widespread white matter differences in PCs, with no significant gray matter differences.
• PCs exhibited decreased white matter integrity (increased mean diffusivity, decreased neurite density) in reading-associated tracts (superior and inferior longitudinal fasciculi).
• Differences were also observed in tracts linked to cognitive performance (uncinate fasciculus).

Conclusions:

• Diffuse structural connectivity differences in white matter may underlie reading comprehension difficulties in individuals with intact decoding skills.
• These findings align with the behavioral profile of PCs, showing subclinical impairments in language and integrative cognitive processes.
• This study highlights the importance of white matter integrity for reading comprehension.