Differential olfactory identification in children with autism and Asperger's disorder: a comparative and longitudinal study.

Key theories of autism implicate orbitofrontal cortex (OFC) compromise, while olfactory identification (OI) deficits are associated with OFC dysfunction. This study aimed to complete a 5-year follow-up of children with high-functioning autism (HFA) who previously lacked the normal age-OI association; and compare unirhinal-OI in children with HFA, Asperger's disorder (ASP), and controls. While both HFA and controls had improved birhinal-OI at follow-up, reduced OI in some HFA participants suggested OFC deterioration and heterogeneous OFC development. Unirhinal-OI was impaired in HFA but not ASP relative to controls, suggesting orbitofrontal compromise in HFA but integrity in ASP. Differing IQ-OI relationships existed between HFA and ASP. Findings support the hypothesis of separate neurobiological underpinnings in ASP and HFA, specifically differential orbitofrontal functioning.