RESEARCH ARTICLE Visuoperceptual Processing in Children With Neurofibromatosis Type 1: True Deficit or Artefact? Lien Van Eylen, 1,2,3 * Ellen Plasschaert, 4,5 Johan Wagemans, 1,6 Bart Boets, 1,3 Eric Legius, 4,5 Jean Steyaert, 1,7,8 and Ilse Noens 1,2 1 Leuven Autism Research (LAuRes), KU Leuven, Leuven, Belgium 2 Parenting and Special Education Research Unit, KU Leuven, Leuven, Belgium 3 Research Group Psychiatry, UPC-KU Leuven, Leuven, Belgium 4 Department of Human Genetics, KU Leuven, Leuven, Belgium 5 Center for Human Genetics, University Hospital Leuven, Leuven, Belgium 6 Brain and Cognition, KU Leuven, Leuven, Belgium 7 Department of Child Psychiatry, UPC-KU Leuven, Leuven, Belgium 8 Department of Clinical Genetics, University Hospital Maastricht, Maastricht, the Netherlands Manuscript Received: 2 September 2016; Manuscript Accepted: 12 December 2016 Impairments in visuoperceptual processing have long been considered a hallmark deficit of individuals with Neurofibro- matosis type 1 (NF1). However, it is unclear which specific visuoperceptual subprocesses are impaired and whether impairments on these tasks really result from visuoperceptual impairments or rather from confounding factors like Execu- tive Functioning (EF) impairments, lower intelligence (IQ) and/or co-occurring symptoms of Autism Spectrum Disorder (ASD). To answer these questions, we administered four visuoperceptual tasks and two control tasks in 39 children with NF1, 52 typically developing children and 52 children with ASD (8–18 years), all matched for age and gender. Furthermore, EF, IQ, and symptoms of ASD were assessed. Children with NF1 displayed intact visual form discrimination and intact information integration along the dorsal visual pathway. Moreover, their reduced performance on a task requiring integration of information along the ventral visual stream and their more detail-oriented processing style appeared to result from confounding EF impairments and not from visuoperceptual impairments per se. The co-occur- ring ASD symptoms and lower IQ of the children with NF1 did not impact substantially upon their visuoperceptual perfor- mance. These findings point to the large impact of EF impair- ments on the performance of visuoperceptual task and suggest that individuals with NF1 show intact visual form discrimina- tion, intact visual integration, and typical visual processing style when potential confounding factors are controlled for. This may have large repercussions for the interpretation of other findings on visuoperceptual processing in individuals with NF1. Ó 2017 Wiley Periodicals, Inc. Key words: neurofibromatosis type 1; visuospatial function- ing; executive functioning; autism spectrum disorder; con- founding factors INTRODUCTION Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder affecting approximately 1 in 2,700 newborns [Evans et al., 2010]. It is caused by a heterozygous mutation in the NF1 gene encoding neurofibromin. Diagnostic features of NF1 are caf e-au-lait spots, axillary or inguinal freckling, Lisch nodules, and neurofibromas. Other diagnostic criteria are Lien Van Eylen and Ellen Plasschaert are the joint-first authors. Conflicts of interest: All authors declare that there is no conflict of interest. Grant sponsor: Research Foundation Flanders (FWO); Grant sponsor: Marguerite–Marie Delacroix Foundation; Grant sponsor: KU Leuven; Grant sponsor: Research Council of KU Leuven.  Correspondence to: Dr. Lien Van Eylen, Research Group Psychiatry, Kapucijnenvoer 33 blok i - box 7001, 3000 Leuven, Belgium. E-mail: lien.vaneylen@kuleuven.be Article first published online in Wiley Online Library (wileyonlinelibrary.com): 00 Month 2017 DOI 10.1002/ajmg.b.32522 How to Cite this Article: Van Eylen L, Plasschaert E, Wagemans J, Boets B, Legius E, Steyaert J, Noens I. 2017. Visuoperceptual Processing in Children With Neurofibromatosis Type 1: True Deficit or Artefact? Am J Med Genet Part B 174B:342–358. Ó 2017 Wiley Periodicals, Inc. 342 Neuropsychiatric Genetics