Analyzing White Matter Integrity of the Basolateral Amygdala and Subgenual Anterior Cingulate Cortex and Its Association with Depression in Adults with Autism Spectrum Disorder Using the Shannon Entropy Technique
Nishant Satapathy1, Maurizio Bergamino2, Opal Ousley3
1University of Arizona College of Medicine- Phoenix, 2Barrow Neurological Institute, 3Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine
Objective:
To evaluate Shannon entropy (SE) and fractional anisotropy (FA) as measures of white matter (WM) integrity in adults with autism (ASD) and their relationship with symptom severity and depression.
Background:
Individuals with ASD have an increased risk for depression. Neuroimaging studies indicate involvement of the basolateral amygdala (BLA), subgenual anterior cingulate cortex (sgACC), and associated WM tracts in depression.
Design/Methods:
DTI data was obtained from ABIDE II. 29 males with ASD (mean age=37.5 years; SD=16.1 years) and 29 male controls (mean age = 39.6 years; SD=15.1 years) were divided into younger (16-25 years) and older (40-64 years) groups due to original study recruitment. Whole-brain and region of interest SE and FA were calculated using FSL v.6 and Tract-Based Spatial Statistics. Main effects of age and diagnosis on SE and FA, correlations with depression and ASD symptoms, and contribution of SE and FA in predicting depression were examined.
Results:
SE was higher in the right [F(1,55)=13.084, p<.001; ηp2=.192] and left [F(1,55)=15.811, p<.001; ηp2=.223] sgACC in younger individuals. Older individuals had higher whole-brain FA [F(1,55)=4.199, p=.045; ηp2=.071]. SE correlated with ASD symptoms in the right amygdala [p=.034; r(55)= .244]; FA correlated with depression in the right [p=.033; r(56) = -.244] and left [p=.021; r(56) = -.268] amygdala and right BLA [p=.032; r(56) = -.245]. Post-hoc analyses identified higher FA in ASD in the left [F(1,55)=17.903, p<.001; ηp2=.246] and right [F(1,54)= 12.073, p=.001; ηp2=.183] posterior limbs of the internal capsule (LIC) and the left anterior LIC [F(1,55)=15.027, p<.001; ηp2=.215]. Regression analyses yielded no significant results.
Conclusions:
Age had a main effect on SE and FA in the sgACC and diagnosis had a main effect on FA in the IC. SE correlations with ASD symptomatology in the right amygdala may provide evidence for axonal remodeling and FA in the bilateral amygdala may serve as a biomarker for depression.