In the 4–7-year-old autistic children examined in this study, the volume of the Purkinje cells was 38% smaller than that of the age-matched control group [111]. Moreover, it has been reported that Purkinje cells of the autistic subjects revealed a 40% decrease in the expression of glutamic acid decarboxylase 67 (GAD67) mRNA [114]. In autism, the basket cells provide an increased GABAergic feed-forward inhibition to Purkinje cells. The result could be disruption in the timing of Purkinje cell firings and altered inhibition of the cerebellar nuclei, which could directly affect cerebello-cortical output and contribute to the changes in motor behavior and cognition observed in autism [115]. These findings and the reduced volume (by 26%) of the neurons of the dentate nucleus seen in the 4–7-year-old autistic children [111] suggest that in autism, interactions between the Purkinje cells and dentate nucleus are modified on the structural, molecular and functional levels.
