Hemispheric laterality assessment with dichotic digits testing in dyslexia and auditory processing disorder

One of the widely used tests to evaluate functional asymmetry of cerebral hemispheres is the dichotic listening test with the usually prevailing right ear advantage. The current study aims at assessing hemispheric laterality in an adult sample of individuals with dyslexia, with auditory processing disorder (APD), and adults experiencing comorbidity of the two mentioned disorders against a control group with normal hearing and absence of learning disabilities. Results exhibit a right hemispheric dominance for the control and APD group, a left hemispheric dominance for the group diagnosed with both dyslexia and APD, and absence of dominance for the dyslexia group. Assessment of laterality was repeatable and produced stable results, indicating a true deficit. A component of auditory processing, specifically the auditory performance in competing acoustic signals, seems to be deficient in all three groups, and laterality of hemispheric functions influenced at least for auditory-language stimuli in the two of the three groups, one being adults with dyslexia and the other being adults with comorbidity of dyslexia and APD.