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Anatomical atypia in autistic people ? Fine morphological analyses contradict the results of the last decade


There is no consensus on the presence of anatomical atypia in the cerebellum of people with autism. In an attempt to provide a clear answer, an international consortium coordinated by researchers from UNIACT and BAOBAB (NeuroSpin) studied the morphology of the cerebellar gray matter in 274 autistic individuals and 219 control subjects and used several algorithms that calculate the volume of the different structures of the cerebellum. The results suggest that there is no singularity in the cerebellar anatomy of people with autism.


Published on 6 February 2023

DISCREPANCY BETWEEN THE DIFFERENT STUDIES

Although anatomical atypia have been reported in the cerebellum of people with autism, there does not seem to be a consensus on these. Located at the base of the brain, this area contains more than 50% of cerebral neurons and is involved in social cognition. The reasons for the discrepancies between the numerous studies are probably multiple :

  •  if atypia do exist, they may only concern specific regions of the cerebellum that have not been studied in detail in the published works ;
  • there would be several subgroups of atypia corresponding to distinct subgroups in the autism spectrum ;
  •  several of the studies lack statistical power ;
  • several methods of brain parcelling have been used in the studies, they are not equivalent ;
  •  there is a need to better quantify individual deviations from normal.

    • A ROBUST MORPHOLOGICAL ANALYSIS

    In an attempt to provide a clear answer, a European consortium coordinated by researchers from UNIACT and BAOBAB (NeuroSpin department) decided to study the morphology of the cerebellar gray matter in 274 individuals with autism and 219 control subjects from a multicenter European cohort, EU-AIMS LEAP[1]. To ensure the robustness of their results, the researchers performed a lobular parcellation of the cerebellum with two different methods and used an algorithm that calculates the volume of the different structures of the cerebellum at the voxel scale (voxel-to-voxel morphometric analysis). They also took a meta-analytic approach (incorporating parameters such as age, gender, intracranial volume, IQ...) and performed statistical analyses with linear and multivariate approaches to capture the diversity of cerebellar anatomy in individuals with autism and control subjects. Finally, they performed a dimensional analysis of cerebellar anatomy in an independent cohort of 352 individuals with autism-related symptoms.

    The researchers found no significant differences in the cerebellum between individuals with autism and controls. In addition, there were no significant differences in their normative patterns in the cerebellum in individuals with autism. Finally, they found no evidence of cerebellar atypia associated with age, IQ, gender or social functioning.

    Despite positive results published over the past decade from relatively small samples, their findings thus suggest that there is no singularity in the cerebellar anatomy of individuals with autism.

    Contact Joliot : 

    Josselin Houenou (josselin.houenou@cea.fr)

    This work has benefited from European funding, through two projects EU-Aims and AIMS-2-TRIAL from the action of Innovative Medicines initiative (IMI)
    [1] European Autism Interventions– A Multicentre Study for Developing New Medications; Longitudinal European Autism Project

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