Altered cortical activation and functional connectivity during fixed phrase verbal fluency in children with autism spectrum disorder.

BACKGROUND: This study examined prefrontal activation and functional connectivity during a fixed phrase verbal fluency task (VFT) in children with Autism Spectrum Disorder (ASD) compared to basic information- and Full-Scale Intelligence Quotient (FSIQ)-matched children with intellectual disability (ID), to identify neural mechanisms underlying executive dysfunction specific to ASD beyond general cognitive impairment. METHODS: The sample included 33 children diagnosed with ASD and 21 with ID, all with FSIQ < 70. Cortical hemodynamics were recorded using a 19-channel functional near-infrared spectroscopy system during a standardized phonemic VFT. Analysis focused on changes in oxyhemoglobin (Oxy-Hb) concentrations within prefrontal cortex (PFC) regions. RESULTS: Compared to the ID group, children with ASD showed significantly reduced cortical activation in prefrontal regions, including Channels 1 (t = -4.272, p < 0.01) and 2 (t = -3.827, p < 0.01), corresponding anatomically to the right inferior frontal gyrus. Functional connectivity was also significantly lower in the ASD group (p < 0.05), with a mean connectivity value of 0.191 (SD = 0.130) versus 0.230 (SD = 0.155) in the ID group. Furthermore, Oxy-Hb changes in prefrontal Channels 1 (r = -0.852, p < 0.001) and 2 (r = -0.606, p < 0.001) were negatively correlated with Childhood Autism Rating Scale total scores, indicating that decreased prefrontal activation was associated with increased clinical symptom severity. CONCLUSIONS: These findings demonstrate distinct alterations in cortical activation and functional connectivity during VFTs in children with ASD. These findings suggest that disrupted coordination among brain regions contributes to impairments in phonemic fluency and executive control in ASD. Children with ASD exhibited reduced PFC activation accompanied by weakened functional connectivity during the VFT.