Lorna F. Halliday|J Barry|Mervyn J. Hardiman|Dorothy V. M. Bishop
Late, not early mismatch responses to changes in frequency are reduced or deviant in children with dyslexia: an event-related potential study
University College London|MRC Institute of Hearing Research|Queen's Medical Centre|University of Oxford|University of Oxford
developmental disorders oral written language linked deficits processing auditory information however findings inconsistent behavioural electrophysiological measuresin study examined eventrelated potentials erps 20 6 14yearold children developmental dyslexia 20 agematched controls divided younger 611 years n 10 older 1114 years n 10 age bands focused early mismatch negativity mmn late late discriminative negativity ldn conventional mismatch responses associated measures derived timefrequency analysis intertrial coherence eventrelated spectral perturbation responses elicited using auditory oddball task whereby stream 1000hz standards interspersed rare large 1200 hz small 1030 hz frequency deviantsconventional analyses revealed significant differences groups size mmn either large small frequency deviants however younger age band children dyslexia showed enhanced intertrial coherence theta frequency band time window corresponding mmn small deviants contrast children showed reducedamplitude ldn small deviants relative agematched controls whilst older children dyslexia showed shorter less intense period eventrelated desynchronization time windowinitial detection discrimination auditory frequency change appears normal even enhanced children dyslexia rather deficits latestage auditory processing appear feature population