Reduced neurite density index in the prefrontal cortex of adults with autism assessed using neurite orientation dispersion and density imaging

Takashi Arai; Koji Kamagata; Wataru Uchida; Christina Andica; Kaito Takabayashi; Yuya Saito; Rukeye Tuerxun; Zaimire Mahemuti; Yuichi Morita; Ryusuke Irie; Eiji Kirino; Shigeki Aoki

doi:10.3389/fneur.2023.1110883

Reduced neurite density index in the prefrontal cortex of adults with autism assessed using neurite orientation dispersion and density imaging

Front Neurol. 2023 Aug 11:14:1110883. doi: 10.3389/fneur.2023.1110883. eCollection 2023.

Authors

Takashi Arai¹, Koji Kamagata², Wataru Uchida¹, Christina Andica^{1

2}, Kaito Takabayashi¹, Yuya Saito¹, Rukeye Tuerxun¹, Zaimire Mahemuti¹, Yuichi Morita^{1

3}, Ryusuke Irie¹, Eiji Kirino^{4

5}, Shigeki Aoki¹

Affiliations

¹ Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
² Faculty of Health Data Science, Juntendo University, Chiba, Japan.
³ Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
⁴ Department of Psychiatry, Juntendo University Graduate School of Medicine, Tokyo, Japan.
⁵ Department of Psychiatry, Juntendo University Shizuoka Hospital, Shizuoka, Japan.

Abstract

Background: Core symptoms of autism-spectrum disorder (ASD) have been associated with prefrontal cortex abnormalities. However, the mechanisms behind the observation remain incomplete, partially due to the challenges of modeling complex gray matter (GM) structures. This study aimed to identify GM microstructural alterations in adults with ASD using neurite orientation dispersion and density imaging (NODDI) and voxel-wise GM-based spatial statistics (GBSS) to reduce the partial volume effects from the white matter and cerebrospinal fluid.

Materials and methods: A total of 48 right-handed participants were included, of which 22 had ASD (17 men; mean age, 34.42 ± 8.27 years) and 26 were typically developing (TD) individuals (14 men; mean age, 32.57 ± 9.62 years). The metrics of NODDI (neurite density index [NDI], orientation dispersion index [ODI], and isotropic volume fraction [ISOVF]) were compared between groups using GBSS. Diffusion tensor imaging (DTI) metrics and surface-based cortical thickness were also compared. The associations between magnetic resonance imaging-based measures and ASD-related scores, including ASD-spectrum quotient, empathizing quotient, and systemizing quotient were also assessed in the region of interest (ROI) analysis.

Results: After controlling for age, sex, and intracranial volume, GBSS demonstrated significantly lower NDI in the ASD group than in the TD group in the left prefrontal cortex (caudal middle frontal, lateral orbitofrontal, pars orbitalis, pars triangularis, rostral middle frontal, and superior frontal region). In the ROI analysis of individuals with ASD, a significantly positive correlation was observed between the NDI in the left rostral middle frontal, superior frontal, and left frontal pole and empathizing quotient score. No significant between-group differences were observed in all DTI metrics, other NODDI (i.e., ODI and ISOVF) metrics, and cortical thickness.

Conclusion: GBSS analysis was used to demonstrate the ability of NODDI metrics to detect GM microstructural alterations in adults with ASD, while no changes were detected using DTI and cortical thickness evaluation. Specifically, we observed a reduced neurite density index in the left prefrontal cortices associated with reduced empathic abilities.

Keywords: autism; diffusion tensor imaging; diffusion-weighted imaging; gray matter; neurite orientation dispersion and density imaging; neuronal loss; surface-based cortical thickness measurement.