Investigation of Neuroanatomical Differences Between Autism and AspergerSyndrome

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Abstract
Autism is a pervasive developmental disorder (PDD) defined by the followingtriad of behavioral characteristics: social and communication impairmentsin combination with restricted and repetitive behaviors.1,2 Manyautistic individuals have cognitive impairments; in the literature, subjectswith an IQ of less than 70 are typically designated as having low-functioningautism (LFA), and those with an IQ of at least 70 as having high-functioningautism (HFA).3-5 Aspergersyndrome (ASP), another PDD, is similar to autism, sharing features of socialimpairment and repetitive behaviors, in the absence of communication and cognitiveimpairments (ie, phrase language developed before 36 months of age and IQ≥70).2,6,7 Because persons withHFA also have IQs of at least 70, and the DSM-IV doesnot require a history of language delay for a diagnosis of autism, this createsa diagnostic overlap between HFA and ASP, resulting in many individuals withASP who meet DSM-IV criteria for autism.4,8 As a result, many studies comparingHFA and ASP distinguish these 2 conditions according to history of phraselanguage development (HFA at 36 months or older, and ASP at younger than 36months).9-13