Non-impaired auditory phase locking in dyslexic adults

DYSLEXIC adults have profound difficulties in discriminating rapidly presen ted sound sequences. To test whether these deficits might be caused by impa ired neuronal phase locking to the envelopes of the sound stimuli, 20 norma l-reading and 13 dyslexic adults discriminated pitches of pure tones at sim ilar to 1 kHz (producing spectral pitch due to place coding in the cochlea) and of similar to 80 Hz amplitude modulations of white noise (producing pe riodicity pitch based on temporal information only). We proposed that a spe cific deficit in phase locking would result in a worse ability to discrimin ate periodicity than spectral pitch. The dyslexics were significantly less accurate than the control subjects in discriminating both spectral and peri odicity pitch stimuli but their performance was not disproportionally worse in the periodicity pitch task. Thus it seems that impaired neuronal phase- locking cannot explain the problems dyslexics face in processing of rapid s ound sequences. NeuroReport 10:2347-2348 (C) 1999 Lippincott Williams & Wil kins.