Comparison of attention and brain functional connectivity between patient groups with schizophrenia and attention deficit hyperactivity disorder.

Schizophrenia and attention deficit hyperactivity disorder (ADHD) have many contradicting features, but both these disorders share inattention as a core symptom. This study explored how the characteristics of inattention differ between the two disorders. 20 patients with schizophrenia, 20 patients with adult ADHD and 20 healthy controls participated in this study. Comprehensive attention test, Korean Wechsler adult intelligence scale-IV and resting-state functional magnetic resonance imaging (fMRI) were collected, among other things. The schizophrenia and ADHD groups showed low and high levels of functional connectivity in the default mode network (DMN), respectively. Functional connectivity level within the DMN was also positively correlated with processing speed index in the schizophrenia group and positively correlated with the number of divided-attention commission errors in the ADHD group. These results show that schizophrenia and adult ADHD have similarities in the characteristics of attention deficit, in that both may arise from dysregulation within the DMN. However, the differences in the levels of functional connectivity in the DMN between these groups affect how inattention manifests in each group.