Cortical auditory signal processing in poor readers

Magnetoencephalographic responses recorded from auditory cortex evoked by b rief and rapidly successive stimuli differed between adults with poor vs. g ood reading abilities in four important ways. First, the response amplitude evoked by short-duration acoustic stimuli was stronger in the post-stimulu s time range of 150-200 ms in poor readers than in normal readers. Second, response amplitude to rapidly successive and brief stimuli that were identi cal or that differed significantly in frequency were substantially weaker i n poor readers compared with controls, for interstimulus intervals of 100 o r 200 ms, but not for an interstimulus interval of 500 ms. Third, this neur ological deficit closely paralleled subjects' ability to distinguish betwee n and to reconstruct the order of presentation of those stimulus sequences. Fourth, the average distributed response coherence evoked by rapidly succe ssive stimuli was significantly weaker in the beta- and gamma-band frequenc y ranges (20-60 Hz) in poor readers, compared with controls. These results provide direct electrophysiological evidence supporting the hypothesis that reading disabilities are correlated with the abnormal neural representatio n of brief and rapidly successive sensory inputs, manifested in this study at the entry level of the cortical auditory/aural speech representational s ystem(s).