Cortical asymmetries at different spatial hierarchies relate to phonological processing ability.

Area of Science:

• Neuroscience
• Cognitive Science
• Developmental Psychology

Background:

• Proficient reading relies on mapping speech sounds to letters.
• Individual differences in phonological processing are linked to brain hemispheric asymmetries.
• Two hypotheses, cerebral lateralization and canalization, propose different relationships between structural asymmetry and phonological ability.

Purpose of the Study:

• To investigate the relationship between brain structural asymmetries and phonological decoding abilities.
• To test predictions of the cerebral lateralization and canalization hypotheses.
• To examine these relationships in both children and adults.

Main Methods:

• Used topological asymmetry analysis on T1-weighted brain images.
• Employed a decoding measure for phonological processing.
• Analyzed data from large samples of children (N=424) and adults (N=300).

Main Results:

• Limited association between asymmetry and decoding in classic language regions.
• Increased left hemisphere cortical asymmetry showed a modest linear association with phonological decoding accuracy (cerebral lateralization hypothesis).
• Increased asymmetry in performance monitoring and motor planning regions correlated with typical phonological decoding (canalization hypothesis).

Conclusions:

• Both cerebral lateralization and canalization hypotheses may be relevant to phonological decoding.
• The scale of brain organization influences which hypothesis best explains the observed relationships.
• Findings highlight the complex interplay between brain structure, hemispheric asymmetry, and reading development.