Developmental dyslexia is cited as an example of a developmental disorder with unclear etiology, with some studies finding abnormalities in which hemisphere?

• A. Left hemisphere
• B. Right hemisphere
• C. Both hemispheres
• D. Occipital lobe

Answer: (A)

Dyslexia often reflects difficulties in phonological processing and mapping sounds to letters, functions that are predominantly handled by language-dominant circuits in the left hemisphere. Neuroimaging and neuropsychological studies frequently show abnormalities in left-hemisphere regions critical for reading, such as the temporoparietal area and the left occipitotemporal region (including the visual word form area), as well as the left arcuate fasciculus that connects core language areas. These left-sided differences align with the core reading-related deficits seen in dyslexia, making the left hemisphere the best-supported site of abnormality. By contrast, abnormalities confined to the right hemisphere or confined to occipital regions alone do not as consistently explain the specific decoding and phonological challenges characteristic of developmental dyslexia.