title: Alterations of visual and auditory evoked potentials in fragile X syndrome.
abstract: BACKGROUND
  Fragile X Syndrome (FXS) is the most common monogenic form of intellectual disability and one of the few known monogenic causes of autism. It is caused by a trinucleotide repeat expansion in the FMR1 ('Fragile X Mental Retardation 1') gene, which prevents expression of the 'Fragile X Mental Retardation Protein' (FMRP). In FXS, the absence of FMRP leads to altered structural and functional development of the synapse, while preventing activity-based synapse maturation and synaptic pruning, which are essential for normal brain development and cognitive development. Possible impairments in information processing can be non-invasively investigated using electrophysiology.
  
  
  METHODS
  We compared auditory (AEP) and visual (VEP) evoked potentials in twelve adolescents and young adults (10-22 years) affected by FXS to healthy controls matched by chronological age (N=12) and developmental age of cognitive functioning (N=9; 5-7 years), using analysis of variance.
  
  
  RESULTS
  In the visual modality, the N70 and N2 amplitude have been found increased in FXS in comparison to the chronological, but not the developmental control group at occipital sites, whereas in the auditory modality N1, P2 and N2 amplitude as well as N2 latency have been found increased in FXS, relative to both chronological and developmental control groups at mid-central sites.
  
  
  CONCLUSIONS
  The AEP/VEP profile suggests disruptions in sensory processing specific to FXS that exceed immaturity of physiological activity. In addition, the auditory modality seems to be more affected than the visual modality. Results are discussed in light of possible underlying neuronal mechanisms, including deficits in synaptic pruning and neuronal inhibition that might account for a hyperreactive nervous system in FXS.
authors.affiliation: Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, University of Montreal, Quebec, Canada; Psychology Department, University of Montreal, Quebec, Canada; Centre de Recherche en Neuropsychologie et Cognition, University of Montreal, Quebec, Canada. Electronic address: Inga.Knoth@umontreal.ca.
authors.forename: Inga Sophia
authors.initials: IS
authors.lastname: Knoth
authors.affiliation: Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, University of Montreal, Quebec, Canada.
authors.forename: Phetsamone
authors.initials: P
authors.lastname: Vannasing
authors.affiliation: Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, University of Montreal, Quebec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Major
authors.affiliation: Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, University of Montreal, Quebec, Canada.
authors.forename: Jacques L
authors.initials: JL
authors.lastname: Michaud
authors.affiliation: Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, University of Montreal, Quebec, Canada; Psychology Department, University of Montreal, Quebec, Canada; Centre de Recherche en Neuropsychologie et Cognition, University of Montreal, Quebec, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Lippé
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D002648:Child; D003192:Compulsive Behavior; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005600:Fragile X Syndrome / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012727:Sex Characteristics; D055815:Young Adult
keywords: Auditory evoked potential; Autism; Fragile X syndrome; Intellectual disability; Sensory information processing; Visual evoked potential