EEG spectra in dyslexic and control boys during resting conditions

Abstract

We studied the resting eyes open and eyes closed EEG in carefully screened samples of 9–13-year-old dyslexic and control boys within a 2-cohort cross-validation design with repeat testing 1–3 years later. We found: (1) no difference between groups in delta or theta activity in either cohort or in repeat testing 1–3 years later; (2) in the dyslexics, decreased beta (19–24 c/sec) activity at bilateral central, parietal and mid-temporal leads referenced to vertex; (3) inconsistent group differences in the alpha band: the first cohort dyslexics had lower alpha power than did the controls, but there was no group difference in the second cohort; and (4) significant relative delta differences between groups in the first cohort, which were shown to be a statistical artifact of the use of relative power. We conclude that: (1) dyslexia per se is not associated with increased absolute power in the delta and theta bands; (2) lower power in the high beta band is reliably found in these samples of dyslexics without other disorders; and (3) alpha power levels are not consistently lower in the dyslexic group.