Brain mapping in dysphonemic dyslexia: in resting and phonemic discrimination conditions

Topographic mapping of EEG bands and alpha asymmetry were analyzed during resting conditions and an auditory phonemic discrimination task (APD) in carefully screened samples of 9.0- to 12-year-old control and dysphonemic-sequencing dyslexic children. The EEG was recorded over the entire scalp, with a linked ears reference. We found: (1) no differences between groups during resting conditions in any frequency band analyzed; (2) a left hemisphere alpha responsiveness in dyslexic children during the APD condition; and (3) a beta 2 decrease in the left posterior quadrant in dyslexics during the APD condition. We conclude that the lower alpha and beta 2 responsiveness may be due to a diminished cortical reactivity and may be related to intrinsic disorganization of the neural processors associated directly with the APD task demands, the alpha activity reflecting poor attention to an external stimuli source and the beta 2 decrease reflecting an unusual processing associated with the linguistic cognitive requirements.