(103) Surface Based Morphometry (SBM) in Opioid Use Disorder: A Controlled Study

Background: Research consistently indicates the association between opioid dependence and regional alteration in the brain grey matter volume in voxel-based morphometry (VBM) (Liu et al., 2009; Wang et al., 2012). However, VBM is influenced by strategies of smoothing, registration, and normalization; moreover, it cannot detect changes in cortical thickness and folding. Surface-based morphometry (SBM) can address these limitations. Little research is done on the various aspects of SBM in opioid use disorder (OUD).
Aim &

Objectives: We wanted to examine the differences in cortical thickness, sulcal depth, gyrification, and fractal dimension between individuals with OUD and age-, sex-, education-matched controls.

Methods: We recruited 31- treatment-naïve individuals with OUD and 26 non-drug using controls. We processed and analyzed T1 MR images using the SBM pipeline of the CAT-12 toolbox within the statistical parametric mapping (SPM 12). Following preprocessing, volumes were segmented using surface and thickness estimation for the region of interest analysis. We used the projection-based thickness method for the estimation of cortical thickness (Dahnke et al., 2013). Local gyrification index (GI) maps were calculated based on the absolute mean curvature approach (Luders et al., 2006). We used the FreeSurfer-based Desikan-Killiany and Destrieux Atlas for cortical parcellation. We chose two atlases because the choice of the atlas may affect the results of between-group comparisons in thickness.

Results: Mean age and years of education of the OUD group were 28 (±5) and 11.6 (± 2.4) years, respectively. There was no difference in age, sex, and education between OUD and control groups. OUD showed increased cortical thickness in bilateral superior parietal, superior frontal, and right-sided orbitofrontal, entorhinal, gyrus rectus, and anterior cingulate cortices. However, only the superior-parietal region and gyrus rectus survived the false discovery rate corrections. OUD group also had higher sulcal depth in parts of inferior, middle, and superior frontal regions, and in bilateral superior temporal cortices. GI of the OUD group was lower in the right insula but higher for the right lingual and transverse temporal regions. Finally, we observed higher fractal dimensions in the OUD group in various parts of frontal, parietal, and temporal cortices. The difference in the fractal dimension of the right superior temporal gyrus remained significant after multiple comparisons. Duration of opioid use and dependence modestly correlated with the fractal dimensions of entorhinal, orbitofrontal, and superior temporal cortices.

Conclusion: OUD is associated with changes in surface-based morphometry and changes may be influenced by the duration of opioid use.

References: Dahnke, R., Yotter, R. A., & Gaser, C., 2013. Cortical thickness and central surface estimation. Neuroimage. 65, 336-348.
Liu, H., Hao, Y., Kaneko, Y., Ouyang, X., Zhang, Y., Xu, L., Xue, Z., Liu, Z., 2009. Frontal and cingulate gray matter volume reduction in heroin dependence: optimized voxel-based morphometry. Psychiatry Clin. Neurosci. 63, 563–568.
Luders, E., Thompson, P. M., Narr, K. L., Toga, A. W., Jancke, L., & Gaser, C., 2006. A curvature-based approach to estimate local gyrification on the cortical surface. Neuroimage. 29(4), 1224-1230.
Wang, X., Li, B., Zhou, X., Liao, Y., Tang, J., Liu, T., Hu, D., Hao, W., 2012. Changes in brain gray matter in abstinent heroin addicts. Drug Alcohol Depend. 126, 304–308.

Diversity, Equity, and Inclusion: Department of Science and Technology, Ministry of Health, Government of India has sponsored our study. We conducted this study in a public-funded Institution. We have representation from various religious and economic backgrounds. We adhered to the non-discrimination-policy and ensured equal opportunity to participate to all eligible participants in the study.