Abnormal functional connectivity of dynamic brain network in toddlers with autism and its correlation with symptoms

The pathogenesis of autism spectrum disorder (ASD) remains unclear. Diagnosis relies on symptoms and relevant scales, which are highly subjective. Moreover, most diagnoses are made after the age of 3, delaying treatment opportunities. This study aimed to explore dynamic functional network connectivity (dFNC) in toddlers with ASD aged 1-3 years, to identify group-level differences in dynamic functional connectivity (FC) patterns and investigate their associations with autistic symptoms, with the goal of providing preliminary neuroimaging insights into the neural mechanisms underlying ASD during this critical developmental window.

Magnetic resonance imaging (MRI) data of 41 toddlers diagnosed with ASD and 23 age- and sex-matched normal development control (NC) individuals were collected. We examined group differences in dFNC properties, including temporal characteristics of brain states, mean dwell time (MDT), state occurrence rate (OR), and state transition frequency. Correlation analyses were performed to assess the relationships between these dFNC metrics and the severity of autistic symptoms.

Compared with the NC group, toddlers with ASD spent more time in a brain state characterized by globally weak connectivity and a notable lack of between-network functional connectivity, with a significantly higher OR and nominally longer MDT. They also showed a nominally reduced MDT in a brain state marked by strong within-network connectivity and enhanced modular organization across multiple functional networks. Exploratory correlation analyses between autism metrics and dFC measures suggested several nominal associations (uncorrected p < 0.05).

Toddlers with ASD exhibit abnormal dFNC patterns, characterized by altered temporal properties of brain states and disrupted state-related connectivity profiles. These results provide empirical evidence for altered dynamic brain organization in early ASD, contributing to a better understanding of its neural underpinnings during this critical developmental window.