Scientists at CNRS, Aix-Marseille Université and AP-HM have identified a cerebral marker specific to autism that can be detected by MRI and is present as from the age of two years. The abnormality thus detected consists in a less deep fold in Broca’s area, a region of the brain specialized in language and communication, functions that are impaired in autistic patients. This discovery may assist in the earlier diagnosis and management of these patients. It has been made possible by the medical imaging processing skills of the Institut de Neurosciences de la Timone (CNRS/Aix-Marseille Université) and access to a homogeneous cohort of patients diagnosed at a very young age and all assessed using the same protocol at the Centre de Ressources Autisme PACA. The results of their collaboration are published on 12 January 2016 in Biological Psychiatry: Cognitive Neurosciences and Neuroimaging.
The autistic spectrum covers a range of neuro-developmental disorders (typical autism, Asperger’s syndrome or pervasive developmental disorders not otherwise specified) which mainly affect social relationships and communication. These disorders are associated with abnormal development of the brain. Recent neuroimaging findings have notably suggested the existence of abnormal cortical folding (the formation of convolutions on the surface of the brain). However, standard neuro-anatomical measurement techniques had failed until now to demonstrate any markers specific to each of these disorders, and notably typical autism.
Scientists at the Institut de Neurosciences de la Timone (in Marseille, France) focused on a new geometric marker called the “sulcal pit”. This is the deepest point of each sulcus in the cerebral cortex, from which points all the folds on the brain’s surface develop. They are therefore put in place at a very early developmental stage, probably under genetic influences, which means they are indicators adapted to comparisons between different individuals.
Based on MRI findings, the scientists observed the sulcal pits of 102 young boys aged 2 to 10 years, who were placed in three groups (those with autistic disorder, pervasive developmental disorder not otherwise specified, and typically developing children). By comparing these three groups, they discovered that in Broca’s area (a region known to be involved in language and communication), the maximum depth of a sulcus was less among autistic children when compared with the other two groups. Interestingly, this highly localized atrophy was correlated with the social communication performance of children in the autistic group: the deeper the sulcal pits, the more impaired were their skills in terms of language production.
This abnormality specific to autistic children may therefore constitute a biomarker for the disease that could enable their earlier diagnosis and management, as from the age of two years. Indeed, at present, autism can only be diagnosed based on clinical signs, through the observation of children and interviews with their parents*.
This study has also enabled a discovery concerning brain development. While it was previously thought that cortical folding was complete at birth, the scientists observed that some folds (the most superficial) continued to deepen with age and in an identical manner in both autistic and other children. Biomedical research may therefore help to improve our understanding of the mechanisms of life.
* This is generally only achieved at the age of 4½ years in France.
Source: Véronique Etienne – CRNS
Image Source: The image is credited to SCALP team / INT
Original Research: Abstract for “Localized Misfolding Within Broca’s Area as a Distinctive Feature of Autistic Disorder” by Lucile Brun, Guillaume Auzias, Marine Viellard, Nathalie Villeneuve, Nadine Girard, François Poinso, David Da Fonseca and Christine Deruelle. in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. Published online January 2016 doi:10.1016/j.bpsc.2015.11.003
Localized Misfolding Within Broca’s Area as a Distinctive Feature of Autistic Disorder
Recent neuroimaging studies suggest that autism spectrum disorder results from abnormalities in the cortical folding pattern. Usual morphometric measurements have failed to provide reliable neuroanatomic markers. Here, we propose that sulcal pits, which are the deepest points in each fold, are suitable candidates to uncover this atypical cortical folding.
Sulcal pits were extracted from a magnetic resonance imaging database of 102 children (1.5–10 years old) distributed in three groups: children with autistic disorder (n = 59), typically developing children (n = 22), and children with pervasive developmental disorder not otherwise specified (n = 21). The geometrical properties of sulcal pits were compared between these three groups.
Fold-level analyses revealed a reduced pit depth in the left ascending ramus of the Sylvian fissure in children with autistic disorder only. The depth of this central fold of Broca’s area was correlated with the social communication impairments that are characteristic of the pathology.
Our findings support an atypical gyrogenesis of this specific fold in autistic disorder that could be used for differential diagnosis. Sulcal pits constitute valuable markers of the cortical folding dynamics and could help for the early detection of atypical brain maturation.
“Localized Misfolding Within Broca’s Area as a Distinctive Feature of Autistic Disorder” by Lucile Brun, Guillaume Auzias, Marine Viellard, Nathalie Villeneuve, Nadine Girard, François Poinso, David Da Fonseca and Christine Deruelle. in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. Published online January 2016 doi:10.1016/j.bpsc.2015.11.003