title: Abnormal late visual responses and alpha oscillations in neurofibromatosis type 1: a link to visual and attention deficits.
abstract: BACKGROUND
  Neurofibromatosis type 1 (NF1) affects several areas of cognitive function including visual processing and attention. We investigated the neural mechanisms underlying the visual deficits of children and adolescents with NF1 by studying visual evoked potentials (VEPs) and brain oscillations during visual stimulation and rest periods.
  
  
  METHODS
  Electroencephalogram/event-related potential (EEG/ERP) responses were measured during visual processing (NF1 n = 17; controls n = 19) and idle periods with eyes closed and eyes open (NF1 n = 12; controls n = 14). Visual stimulation was chosen to bias activation of the three detection mechanisms: achromatic, red-green and blue-yellow.
  
  
  RESULTS
  We found significant differences between the groups for late chromatic VEPs and a specific enhancement in the amplitude of the parieto-occipital alpha amplitude both during visual stimulation and idle periods. Alpha modulation and the negative influence of alpha oscillations in visual performance were found in both groups.
  
  
  CONCLUSIONS
  Our findings suggest abnormal later stages of visual processing and enhanced amplitude of alpha oscillations supporting the existence of deficits in basic sensory processing in NF1. Given the link between alpha oscillations, visual perception and attention, these results indicate a neural mechanism that might underlie the visual sensitivity deficits and increased lapses of attention observed in individuals with NF1.
authors.affiliation: Visual Neuroscience Laboratory, Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, Azinhaga de Santa Comba, Coimbra 3000-548, Portugal. mjribeiro@fmed.uc.pt.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ribeiro
authors.forename: Otília C
authors.initials: OC
authors.lastname: d'Almeida
authors.forename: Fabiana
authors.initials: F
authors.lastname: Ramos
authors.forename: Jorge
authors.initials: J
authors.lastname: Saraiva
authors.forename: Eduardo D
authors.initials: ED
authors.lastname: Silva
authors.forename: Miguel
authors.initials: M
authors.lastname: Castelo-Branco