New findings published in Frontiers in Psychiatry show that adults with ADHD exhibit altered resting state function connectivity (RSFC) of the anterior insula, a crucial region of the salience network, as well as part of the regions in the default mode network (DMN).
The results suggest that disrupted salience network default mode network (SN-DMN) functional connectivity may be involved in executive function impairments, especially with working memory. Moreover, deficits of the anterior insula might play a role in the pathophysiology of ADHD.
A group of investigators in China, led by Qihua Zhao, of the Peking University Sixth Hospital, Institute of Mental Health, Beijing, compared resting state functional MRI data in 28 adults with ADHD and 30 matched healthy controls (HC). In addition, correlations were investigated using self-ratings of executive functions, including inhibition, shifting, and working memory.
“This study was the first to detect the abnormality of the insular subregions’ functional networks among adults with ADHD and determine that the executive function factor scores are associated with RSFC of the anterior insula with the precuneus and temporal gyrus in the HC group,” the authors wrote. “However, there is no correlation of the executive function factor and with the RSFC of the anterior insula in the ADHD group.”
They added that in adults with ADHD, the normal correlations between working memory and RSFC of the anterior insula were disrupted, indicating that working memory and other SN-DMN networks might be involved in executive function impairment in adult ADHD.
All participants were right-handed, had no history of head trauma with loss of consciousness, no history of neurological illness or severe disease (including diagnosis of psychiatric disorders), and no excessive head movements. HCs were matched for sex, age, and IQ.
In addition to the anterior insula, functional networks of mid-insula and posterior insula were explored. Global signal regression (GSR) is controversial, so data processing included ‘with’ and ‘without’ GSR. Self-administered rating scales included the ADHD Rating Scale-IV (ADHD RS-IV), the Behavior Rating Inventory of Executive Function-Adult version (BRIEF-A), and a 3-point Likert scale.
No baseline differences in demographics were detected between groups. Two subtypes of ADHD were noted: 21 were of the inattentive subtype (ADHD-I), and 7 were combined subtype (ADHD-C). Based on the rating scales, the ADHD group showed significantly higher ADHD RS-IV scores and working memory, inhibition, and shifting factor scores compared to HCs.
The authors noted several limitations of the study. Two subtypes of ADHD (ADHD-I and ADHD-C) were included, participants had high IQs, and some received medication treatment before assessment. In addition, the results of the ‘with’ and ‘without’ GSR analyses showed a different pattern.
“The results indicate that disrupted SN-DMN networks might be involved in executive function impairment in adults with ADHD, especially working memory,” the researchers concluded. “Our findings suggest that deficits of [the anterior insula] particularly, which refer to abnormal salient stimuli allocation, might be involved in working memory impairment in patients with ADHD.”
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