[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
Abstract
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
1999;45:495-503
Received: 25 June 1998; Revised: 15 December 1998; Accepted: 16 December 1998
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