Neurolinguistic Deficits and the Left Hemisphere in the Reading Disabled

The relationship between cerebral laterality and neuropsychological functions, particularly phonemic analysis, was examined in a group of 20 reading disabled (RD) and 20 nonreading disabled (NRD) 8- to 12-year-old boys. Compared with NRD children, RD children exhibited an equivalent right ear and left hemispheric superiority for reporting dichotically presented words. However, even with experimental control for attention, the RD boys’ performance was poorer than NRD boys with both left and right ears. In addition, the RD children displayed poor performance on nine scales of the Luria Nebraska Neuropsychological Battery-Children’s Revision (LNNB-CR), and had the most difficulty with the scales and items designed to tap left hemispheric dysfunction (i.e., the Left Sensorimotor, Receptive Speech, Expressive Language, Reading, and Writing scales). All of the RD children also performed poorer than any NRD child on a test of phonemic analysis, the Lindamood Test of Auditory Conceptualization (LAC), which assesses phonemic functions presumably best processed by the left hemisphere. In contrast, the RD children performed equivalently to NRD children on tasks considered best performed by the right hemisphere, including dichotically presented melodies and the Visual and Right Sensorimotor scales of LNNB-CR. The “left hemispheric” tasks tended to be more strongly correlated with each other, and less strongly correlated with “right hemispheric” tasks. These data were interpreted as supportive of the notion that RD children display similar patterns of general hemispheric specialization as NRD children, but have problems with specific, and predominately left hemispheric, cognitive processes which are critical to reading.