Brain Laterality in Dyslexia Seen during Literacy Development and Early Training

Area of Science:

• Neuroscience
• Developmental Psychology
• Education

Background:

• Language processing typically shifts to left hemisphere dominance during literacy acquisition.
• Children with dyslexia often exhibit atypical patterns in brain lateralization for language.

Purpose of the Study:

• To investigate the developmental trajectory of brain laterality for language in children with and without dyslexia before and during literacy acquisition.
• To assess the impact of early, evidence-based literacy training on brain lateralization in these groups.

Main Methods:

• Longitudinal study involving Dichotic Listening (DL) tests to assess brain laterality.
• Participants included a typical group and a dyslexia group, assessed yearly from ages 5 to 11.
• Both groups received annual literacy training sessions from ages 5 to 7.

Main Results:

• Typical group: Shift from no ear advantage (age 6) to right ear advantage (left hemisphere dominance) by ages 8 and 11.
• Dyslexia group: Right ear advantage (right hemisphere dominance) at age 6, with increasing scores but no ear dominance by age 11.
• Evidence-based training showed potential effects on both hemispheres in the dyslexia group.

Conclusions:

• Dyslexia is associated with distinct developmental patterns of brain lateralization for language.
• Early, evidence-based literacy interventions may influence hemispheric involvement in children with dyslexia.
• Further research is warranted to understand the long-term effects of training on brain organization in dyslexia.