[esnr] Dyslexia and ERPs

  • From: "Gruzelier, John H" <j.gruzelier@xxxxxxxxxxxxxx>
  • To: <esnr@xxxxxxxxxxxxx>
  • Date: Tue, 5 Oct 2004 12:49:36 +0100

Have copied this off the journal website. Copies available back channel.

Original Article
Impaired auditory frequency discrimination in dyslexia detected with mismatch 
evoked potentials 
Torsten Baldeweg, MD *, Alexandra Richardson, PhD, Sarah Watkins, MBBS, 
Christine Foale, MBBS, John Gruzelier, MA, PhD  
Division of Neuroscience and Psychological Medicine, Imperial College School of 
Medicine, London, UK    
*Correspondence to Torsten Baldeweg, Institute of Child Health and Great Ormond 
Street Hospital for Children NHS Trust, University College London Medical 
School, The Wolfson Centre, Mecklenburgh Square, London WC1N 2AP, UK

Deficits in phonological skills appear to be at the heart of reading 
disability; however, the nature of this impairment is not yet known. The 
hypothesis that dyslexic subjects are impaired in auditory frequency 
discrimination was tested by using an attention-independent auditory brain 
potential, termed mismatch negativity (MMN) while subjects performed a visual 
distractor task. In separate blocks, MMN responses to graded changes in tone 
frequency or tone duration were recorded in 10 dyslexic and matched control 
subjects. MMN potentials to changes in tone frequency but not to changes in 
tone duration were abnormal in dyslexic subjects. This physiological deficit 
was corroborated by a similarly specific impairment in discriminating tone 
frequency, but not tone duration, which was assessed separately. Furthermore, 
the pitch discrimination and MMN deficit was correlated with the degree of 
impairment in phonological skills, as reflected in reading errors of regular 
words and nonwords. It is possible that in dyslexia a persistent sensory 
deficit in monitoring the frequency of incoming sound may impair the feedback 
control necessary for the normal development of phonological skills. Ann Neurol 

Received: 25 June 1998; Revised: 15 December 1998; Accepted: 16 December 1998

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