Capturing the dynamics of response variability in the brain in ADHD

Area of Science:

• Neuroscience
• Developmental Psychology
• Cognitive Science

Background:

• Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with heightened intra-individual variability in cognitive task response times.
• Developmental trajectories of this variability and its link to cognitive performance in ADHD remain underexplored.

Purpose of the Study:

• To investigate developmental changes in intra-individual response time variability in ADHD.
• To examine the relationship between these variability measures and cognitive performance, specifically on a go-no-go task.
• To explore the neural correlates of these developmental changes using fMRI.

Main Methods:

• Utilized an ex-Gaussian distribution to model response times, differentiating between fast response variability and attention lapses.
• Collected fMRI data from 20 individuals with ADHD and 20 typically developing controls (aged 7-24 years) during a go-no-go task.
• Analyzed developmental changes in ex-Gaussian parameters (sigma for fast variability, tau for lapses) and their correlation with task performance and brain activation.

Main Results:

• Ex-Gaussian measures predicted no-go performance better than traditional reaction time metrics.
• ADHD subjects showed age-related decreases in fast response variability (sigma) but not attention lapses (tau), unlike controls who decreased in both.
• Age-related reductions in variability predicted task performance in controls, but not in ADHD.
• Neural activation in the dorsal anterior cingulate gyrus (dACG) showed distinct relationships with variability and performance across groups and age.

Conclusions:

• Sophisticated measures of intra-individual variability capture task performance dynamics and neural changes missed by traditional methods.
• Developmental changes in response variability differ between ADHD and typically developing individuals, with implications for cognitive control.
• Neural mechanisms underlying cognitive performance and its development in ADHD are distinct from those in typical development.