Diminished auditory mismatch fields in dyslexic adults.
Electroencephalographic studies have demonstrated smaller auditory responses to infrequent deviances of speech and nonspeech sounds in dyslexic than normal-reading subjects. We used a whole-scalp neuromagnetometer to study selectively reactivity of the auditory cortices to sound deviances in 8 dyslexic and 11 normal-reading adults. Within a monotonous sequence of 50-millisecond 1000 Hz binaural tones, tones of 920 and 1080 Hz occurred with 7% probability each. Magnetic mismatch fields, elicited by the stimulus deviances, were diminished in the left hemisphere of the dyslexic subjects. The results indicate deficient change detection in the left auditory cortex of right-handed dyslexic adults.
Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland. hanna@neuro.hut.fi
Hanna
H
Renvall
Riitta
R
Hari
D000328:Adult; D001288:Attention / Q000502:physiology; D001303:Auditory Cortex / Q000503:physiopathology*; D001309:Auditory Threshold / Q000502:physiology*; D004410:Dyslexia / Q000150:complications*; D004569:Electroencephalography; D004574:Electromagnetic Fields; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006315:Hearing Loss, Functional / Q000150:complications* / Q000503:physiopathology*; D006801:Humans; D015225:Magnetoencephalography / Q000295:instrumentation; D008297:Male; D012720:Severity of Illness Index; D013067:Speech Perception / Q000502:physiology; D013997:Time Factors