Are Vermal Lobules VI-VII Smaller in Autism Spectrum Disorder?

Cerebellar volume, in particular vermal lobule areas VI-VII, have been extensively researched in individuals with autism spectrum disorder (ASD), although findings are often unclear. The aim of the present study is to consolidate all existing cerebellar and age data of individuals with ASD, and compare this data to typically developing (TD) controls. Raw data, or the means and standard deviations of cerebellar volume and age, were obtained from 17 studies (N_Cerebellum: 421 ASD and 370 TD participants; N_VI-VII: 506 ASD and 290 TD participants). Total cerebellar volume, or VI-VII area, was plotted against age and lines of fit of ASD and TD data were compared. Mean differences in cerebellar volume and VI-VII area between participants with ASD and TD participants were then compared via ANCOVA analyses. Findings revealed multiple differences in VI-VII area between participants with ASD and TD participants below 18 years of age. Additionally, cerebellar volume was greater in males with ASD than TD males between 2 and 4 years. In the present study, cerebellar volume and VI-VII area show different rates of change across age for those with autism compared with those without. These morphological differences provide a neurobiological justification to investigate related behavioural correlates.