Neurolinguistic Organization in Learning Disabled Children and Adolescents: Some Evidence from Monaural,Verbal Reaction Time

Abstract

Previous studies investigating cerebral organization in learning disabled children have suggested that hemispheric laterality for auditory-linguistic processing is not as complete as that found for their normal achieving counterparts. In addition, based on dichotic listening studies, it has been suggested that certain right hemispheric linguistic processes may be suppressed by the left hemisphere as a function of age in the learning disabled population. Measures of the absolute level of left versus right hemisphere language-processing capacity in LD children are not available, however. This information is critical for more directly testing the hemispheric inhibition theory. This study measured the influence on reaction time of the hand used to respond versus the hemisphere stimulated for a group of learning disabled children and adolescents and a group of normal-achieving peers in an attempt to obtain an index of left and right hemisphere verbal-processing ability. Results obtained tor the normal groups suggested that the right hemisphere was capable of inefficient lexical processing in the presence of a dominant left hemisphere. For the LD groups, however, results suggested that the left hemisphere was responsible solely for processing the auditory-verbal information. Right hemisphere stimulus processing was not predicted from the data. Such findings do not support the notion that LD children develop the ability to suppress right hemisphere linguistic processes as a function of age. Theoretical implications are discussed.