Neuropsychological mechanisms of Digit Symbol Substitution Test impairment in Asperger Disorder Roni Yoran-Hegesh a,b, ⁎ , Semion Kertzman a,b , Tali Vishne b , Abraham Weizman b,c , Moshe Kotler a,b a Research Unit, Beer Yakov-Nes-Ziona Mental Health Center, Nes-Ziona, Israel b Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel c Laboratory of Biological Psychiatry, Felsenstein Medical Research Center, Petah-Tikva, Israel Received 3 November 2006; received in revised form 20 October 2007; accepted 11 November 2007 Abstract Our aim was to investigate the neurocognitive mechanisms recruited by adolescents with Asperger Disorder (AD), in comparison to controls, and to detect the underlying mechanisms during the complex information processing required for the performance of the Digit Symbol Substitution Test (DSST). Male adolescents (n = 23; mean age 15.1 ± 3.6 years) with a DSM-IV diagnosis of AD were compared with a normal male control group with similar demographic characteristics (n = 43; mean age: 15.1 ± 3.6 years). A computerized neurocognitive battery was administered and included: Inspection Time (IT), Finger Tapping Test (FTT), Simple Reaction Time (SRT), Choice Reaction Time (CRT), Digit Running task (DRT), Stroop test and Digit Symbol Substitution Test (DSST). Adolescents with AD performed significantly worse than controls on the DSST. This impaired DSST performance was related to cognitive mechanisms different from those employed by normal controls. Motor slowness and inability to deal with increased amounts of information affected the performance of the AD group, while shifting of attention was the limiting factor in the controls. Both groups were similarly dependent on response selection. This study demonstrated differences in performance in complex cognitive tasks between adolescents with AD and normal controls that may be related to differences in neurocognitive mechanisms underlying information processing. Future neuroimaging studies are needed to clarify the neural network involved in the differences in cognitive performance between AD subjects and normal controls. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Asperger's Disorder; Autistic Disorder; Digit Symbol Substitution Test; Shifting of attention; Information processing; Motor speed 1. Introduction According to the DSM-IV-TR (American Psychiatric Association, 2000) and ICD-10 (World Health Organiza- tion, 1992), Autistic Disorder includes qualitative impair- ment in social interaction and in communication and also restrictive repetitive and stereotyped patterns of behavior, interest and activities; all in the presence of delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years: (1) social interaction, (2) language as used in social communication, (3) symbolic or imaginative play. High Functioning Available online at www.sciencedirect.com Psychiatry Research 166 (2009) 35 – 45 www.elsevier.com/locate/psychres ⁎ Corresponding author. Nes-Ziona Mental Health Center, POB 1, Nes-Ziona 74100, Israel. E-mail address: rhegesh@post.tau.ac.il (R. Yoran-Hegesh). 0165-1781/$ - see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.psychres.2007.11.015