title: [Relationship between magnocellular function and reading skills in children: a study using visual evoked potentials].
abstract: OBJECTIVE
  Developmental dyslexia (DD) is a neurodevelopmental disorder that is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. The magnocellular deficit theory is one of several hypotheses that have been proposed to explain the pathophysiology of DD. In this study, we investigated magnocellular system dysfunction in Japanese dyslexic children.
  
  
  METHODS
  Subjects were 19 dyslexic children (DD group) and 19 aged-matched healthy children (TD group). They were aged between 7 and 16 years. Reversed patterns of black and white sinusoidal gratings generated at a low spatial frequency, high reversal frequency of 7.5 Hz, and low contrasts were used specifically to stimulate the magnocellular system. We recorded visual evoked potentials (VEP) from the occipital area and examined their relationship with reading and naming tasks, such as the time to read hiragana characters, rapid automatized naming of pictured objects, and phonological manipulation.
  
  
  RESULTS
  Compared to the TD group, the DD group showed a significantly lower peak amplitude of VEPs through the complex demodulation method. Structural equation modeling showed that VEP peak amplitudes were related to the rapid automatized naming of pictured objects, and better rapid automatized naming resulted in higher reading skills. There was no correlation between VEP findings and the capacity for phonological manipulation.
  
  
  CONCLUSIONS
  VEPs in response to the magnocellular system are useful for understanding the pathophysiology of DD. Single phonological deficit may not be sufficient to cause DD.
authors.affiliation: Department of Pediatrics, Japan Community Health Care Organization Tokyo Yamate Medical Center. tomokoba@ncnp.go.jp
authors.forename: Tomoka
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Masumi
authors.initials: M
authors.lastname: Inagaki
authors.forename: Hiroko
authors.initials: H
authors.lastname: Yamazaki
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kita
authors.forename: Makiko
authors.initials: M
authors.lastname: Kaga
authors.forename: Akira
authors.initials: A
authors.lastname: Oka
mesh_terms: D000293:Adolescent; D001921:Brain / Q000502:physiology*; D002648:Child; D004410:Dyslexia / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009460:Neurologic Examination; D010775:Photic Stimulation / Q000379:methods; D011932:Reading