title: One-Class Support Vector Machines Identify the Language and Default Mode Regions As Common Patterns of Structural Alterations in Young Children with Autism Spectrum Disorders.
abstract: The identification of reliable brain endophenotypes of autism spectrum disorders (ASD) has been hampered to date by the heterogeneity in the neuroanatomical abnormalities detected in this condition. To handle the complexity of neuroimaging data and to convert brain images in informative biomarkers of pathology, multivariate analysis techniques based on Support Vector Machines (SVM) have been widely used in several disease conditions. They are usually trained to distinguish patients from healthy control subjects by making a binary classification. Here, we propose the use of the One-Class Classification (OCC) or Data Description method that, in contrast to two-class classification, is based on a description of one class of objects only. This approach, by defining a multivariate normative rule on one class of subjects, allows recognizing examples from a different category as outliers. We applied the OCC to 314 regional features extracted from brain structural Magnetic Resonance Imaging (MRI) scans of young children with ASD (21 males and 20 females) and control subjects (20 males and 20 females), matched on age [range: 22-72 months of age; mean = 49 months] and non-verbal intelligence quotient (NVIQ) [range: 31-123; mean = 73]. We demonstrated that a common pattern of features characterize the ASD population. The OCC SVM trained on the group of ASD subjects showed the following performances in the ASD vs. controls separation: the area under the receiver operating characteristic curve (AUC) was 0.74 for the male and 0.68 for the female population, respectively. Notably, the ASD vs. controls discrimination results were maximized when evaluated on the subsamples of subjects with NVIQ ≥ 70, leading to AUC = 0.81 for the male and AUC = 0.72 for the female populations, respectively. Language regions and regions from the default mode network-posterior cingulate cortex, pars opercularis and pars triangularis of the inferior frontal gyrus, and transverse temporal gyrus-contributed most to distinguishing individuals with ASD from controls, arguing for the crucial role of these areas in the ASD pathophysiology. The observed brain patterns associate preschoolers with ASD independently of their age, gender and NVIQ and therefore they are expected to constitute part of the ASD brain endophenotype.
authors.affiliation: Pisa Division, National Institute for Nuclear Physics Pisa, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Retico
authors.affiliation: Pisa Division, National Institute for Nuclear PhysicsPisa, Italy; Department of Chemistry and Pharmacy, University of SassariSassari, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Gori
authors.affiliation: Pisa Division, National Institute for Nuclear PhysicsPisa, Italy; Department of Physics, University of PisaPisa, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Giuliano
authors.affiliation: Department of Developmental Neuroscience, IRCCS Stella Maris FoundationPisa, Italy; Department of Clinical and Experimental Medicine, University of PisaPisa, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Muratori
authors.affiliation: Department of Developmental Neuroscience, IRCCS Stella Maris Foundation Pisa, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Calderoni
keywords: Brain Magnetic Resonance Imaging (MRI); One-class support vector machine; autism spectrum disorders; features classification; preschool children