Structural Architecture of the Social Brain in Adults with Autism: A Combined Cortical Thickness and Similarity Network Analysis

Abstract

Aim: Autism Spectrum Disorder (ASD) involves complex alterations in brain structure that persist across the lifespan. While structural brain alterations are known in children, the persistence of these neuroanatomical differences into adulthood remains less understood. This study examines the neuroanatomical basis of ASD in adulthood, specifically investigating how cortical thickness (CT) and structural similarity networks (SSN) are organized within the social brain network. Materials and Methods: T1-weighted MRI data were obtained for 24 adults with ASD and 24 neurotypical (NT) controls (ages 18–30) from the OpenNeuro dataset (ds002522). Image preprocessing was performed using the recon-all pipeline in FreeSurfer. We investigated CT and SSN at both: (1) the whole-brain, and (2) a hypothesis-driven level targeting 14 specific social brain network regions. CT was assessed using vertex-wise surface-based morphometry, while SSN were constructed using the Morphometric INverse Divergence (MIND) method. MIND quantifies morphological similarities based on the divergence of regional distributions for thickness, volume, surface area, mean curvature, and sulcal depth. Results: The SSN analysis revealed significantly increased nodal connectivity strength in the ASD group within the right posterior insula (p-FDR=0.04) and the orbital part of the right inferior frontal gyrus (p-FDR = 0.04). ROI-based CT comparisons and whole-brain SSN analyses showed no significant group differences. Conclusion: Our findings reveal a neuroanatomical signature in adults with ASD, characterized by localized structural hyper-connectivity within the inferior frontal gyrus and the insula. These results highlight that adult ASD is defined by persistent structural anomalies, manifesting as atypically high structural similarity within key social brain nodes rather than widespread, global network disruptions.

Keywords

• Autism Spectrum Disorder
• Structural Similarity Networks
• Morphometric INverse Divergence
• Cortical Thickness
• Social Brain

Otizmli Yetişkinlerde Sosyal Beynin Yapısal Mimarisi: Kortikal Kalınlık ve Benzerlik Ağlarının Karşılaştırması

Abstract

Otizm Spektrum Bozukluğu (OSB), yaşam boyu devam eden beyin yapısındaki karmaşık değişimleri içerir. Çocuklardaki yapısal beyin değişimleri iyi bilinse de, bu nöroanatomik farklılıkların yetişkinlikte devam edip etmediği iyi bilinmemektedir. Bu çalışma, yetişkinlikteki OSB'nin nöroanatomik temelini, özellikle kortikal kalınlık (KK) ve yapısal benzerlik ağlarının (YBA) sosyal beyin ağı içinde nasıl organize olduğunu araştırmaktadır. OpenNeuro veri setinden (ds002522) 24 OSB'li yetişkin ve 24 nörotipik (NT) kontrol grubuna (18-30 yaş arası) ait T1 ağırlıklı MRG verileri alınmıştır. Görüntü ön işleme süreçleri FreeSurfer'daki recon-all prosedürü kullanılarak gerçekleştirilmiştir. KK ve YBA değerleri (1) tüm beyin seviyesinde ve (2) 14 sosyal beyin ağı ilgi bölgesini hedefleyen hipotez odaklı seviyede incelenmiştir. KK, verteks tabanlı yüzey morfolojisi kullanılarak değerlendirilirken; YBA Morfometrik Ters Iraksama (Morphometric INverse Divergence, MIND) yöntemiyle hesaplanmıştır. MIND; kalınlık, hacim, yüzey alanı, ortalama eğrilik ve sulkal derinlik gibi bölgesel dağılımların ıraksamasına dayanarak morfolojik benzerlikleri nicelleştirmektedir. YBA analizi, OSB grubunda sağ posterior insula (p-FDR=0.04) ve sağ inferior frontal girusun orbital kısmında (p-FDR=0.04) düğüm bağlantı gücünün anlamlı derecede arttığını ortaya koymuştur. İlgi bölgesi temelli KK karşılaştırmaları ve tüm beyin YBA analizleri gruplar arasında anlamlı bir fark göstermemiştir. Bulgularımız, OSB'li yetişkinlerde inferior frontal girus ve insula içinde lokalize yapısal hiper-bağlantısallık ile karakterize bir nöroanatomik profil ortaya koymaktadır. Bu sonuçlar, yetişkinlikteki OSB'nin yaygın küresel ağ bozulmalarından ziyade, temel sosyal beyin düğümleri içinde atipik düzeyde yüksek yapısal benzerlik şeklinde tezahür eden kalıcı yapısal anomalilerle tanımlandığını öne sürmektedir.

Keywords

• Otizm Spektrum Bozukluğu
• Yapısal Benzerlik Ağları
• Morfometrik Ters Iraksama
• Kortikal Kalınlık
• Sosyal Beyin

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