|
Abstract
|
Individuals with Attention Deficit Hyperactivity Disorder (ADHD) show greater Response Time Variability (RTV) when they perform cognitive tasks. Greater RTV may be linked to an inefficient shift from the resting to the active state of the brain. It has been suggested that both functional and structural connectivity of the brain are disrupted during resting and task states in individuals with ADHD. A specific connectivity pattern of the brain may be associated with a disrupted shift from one brain state to another, and this pattern may be associated with greater RTV in ADHD. One way to characterise the connectivity pattern is to apply graph analysis. This study aimed to investigate the relationship between functional connectivity of the brain, RTV, and levels of ADHD symptoms. Twenty-eight children (9-12 years) and 49 adolescents (15-18 years) performed a task called the Detection of Disappearance Task (DDT) to measure alertness while EEG was recorded. In the DDT, participants were asked to detect which digit disappeared from a display of four digits. This task requires maintenance of alertness for fast and accurate performance. The Conners 3 Questionnaire was used to measure each participant’s levels of ADHD symptoms. Functional connectivity between 64 electrodes was computed by the Phase Lag Index to form a weighted network of the brain. Graph analysis was then used to characterise the pattern of functional connectivity. Global efficiency is a measure of functional integration, and modularity is a measure of functional segregation. Greater RTV was associated with higher levels of ADHD symptoms. The graph analysis of EEG functional connectivity showed that higher integrated brain network connectivity was associated with reduced RTV. Compared with the adolescent group, children showed greater RTV, more segregated and less integrated brain networks. These findings suggest that higher integrated brain connectivity may help to produce stable responses. A better integrated brain may process and combine information more efficiently and allow for smoother shifts between different brain states. Individuals with high levels of ADHD symptoms showed less integrated brain networks and more variable responses during the task, suggesting an association between increased RTV and reduced integration of brain activity during the task.
|
