Abnormalities in Brain Complexity in Children with Autism Spectrum Disorder: A Sleeping State Functional MRI Study.

Background and Objective: The theory of complexity loss in mentally disordered brain is widely acknowledged. However, the findings of autism research do not seem to align well with this theory. We aim to investigate the brain complexity in children with ASD (Autism Spectrum Disorders) compared with the TD (Typical Developed) children in sleeping state. Method: 42 ASD children and 42 TD children were imaged using sleep-state functional magnetic resonance imaging (ss-fMRI), and brain complexity was analyzed by employing sample entropy (SampEn) and transfer entropy (TE). For the ASD group, we also investigated the relationship of symptom severity with SampEn and with TE. Results: In compared with TD group, ASD group showed significant elevated SampEn in the right inferior frontal gyrus. However, in the group of TD, 13 pairs of brain regions exhibit higher TE compared to the ASD group. In the ASD group, the TE of 5 pairs of brain regions is higher than in the TD group. A positive correlation was found between cerebellum-amygdala TE in ASD group and ABC total scores. Conclusion: This sleeping-state fMRI study provide evidence that ASD children exhibited aberrant brain complexity in compare with the TD children. The complexity of the autistic brain is composed of aberrant randomness in brain activity and anomalous information transmission between brain regions. We propose that the abnormally diminished quantity of information transmission may potentially underlie the decreased complexity of the autistic brain.