Neuroimaging Research

Project team members: Declan Quinn, Jane McGrath, Robert Whelan, Redmond O’Connell

Approximately 1-in-20 children worldwide have ADHD, a condition associated with disabling inattention, hyperactivity and impulsivity. These problems can manifest as poor inhibitory control (e.g., difficulty holding back impulsive actions) and atypical reward processing (e.g., failing to learn from adverse outcomes). Poorly treated ADHD is associated with negative academic and socioeconomic consequences.

Methylphenidate, a stimulant medication, is used as the first-option pharmacological treatment for ADHD, is very commonly prescribed and often successfully reduces problem behaviour, as well as improving cognitive functioning. Although Methylphenidate can be extremely effective, exactly how it works to change cognitive performance is unknown. We want to understand the mechanism through which Methylphenidate improves cognition by breaking down how children with ADHD make simple decisions.

This project will investigate the specific brain processes that are affected by Methylphenidate by recording brain activity and behaviour in children with ADHD (who have already been prescribed Methylphenidate as part of their clinical care) when they are on and off this medication. Brain activity will be recorded using two separate approaches, which are both non-invasive and routinely used in Trinity College Institute of Neuroscience: electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Brain activity data (and changes in pupil size) will be recorded while children with ADHD are performing cognitive tasks called “perceptual decision-making tasks”.

Put simply, these are simple tasks where children view moving dots on a screen or a flashing image and are asked to make a quick decision about the direction of the dots or the direction the flashing image is pointing in (see below for examples). Basic cognitive tasks like these are incredibly useful as they can be broken down to help us better understand all the elements that make up decision making using mathematical models called “drift diffusion models” (click here for a great explanation of drift diffusion models on the RTE website!). When you combine these models with information about brain activity, you can create a really powerful tool for understanding how all the little pieces that make up a fundamental part of cognition like decision making change when children with ADHD take their medication!

This project is important because if we can understand the brain mechanisms affected by Methylphenidate, we may ultimately be able to develop a computerised measure that will allow clinicians to more objectively assess whether a child is responding to their medication or not. Such a measure would allow clinicians to treat ADHD more effectively and would result in children with ADHD experiencing faster relief from symptoms.

This is a collaborative study with the ‘Neuroimaging of the Children’s Attention Project’ (NICAP), https://bmcpsychiatry.biomedcentral.com/articles/10.1186/s12888-016-0770-4,  a large and comprehensive Australian longitudinal multimodal neuroimaging study led by Prof Tim Silk in Melbourne.

In Trinity College Dublin, the project is led by principal investigator Prof. Jane McGrath (Principal Investigator, Associate Professor of Child and Adolescent Psychiatry and Consultant Child and Adolescent Psychiatrist) and Prof. Rob Whelan (co-Principle Investigator, Associate Professor, School of Psychology). Michael Connaughton (PhD candidate) is currently analysing neuroimaging data collected on 150 children and adolescents with ADHD across three time-points.

The study aims to determine how brain structure and function change with age in ADHD, and whether different trajectories of brain development are associated with variations in outcomes including diagnostic persistence, and academic, cognitive, social and mental health outcomes. This project involves multimodal functional and structural neuroimaging analysis in children and adolescents with ADHD.

During the first phase of this project, a systematic review of research investigating microstructural organisation of white matter amongst children and adolescents with ADHD was carried out. The main findings were that there is atypical white matter microstructure in many neural networks in children with ADHD, and that interestingly, this atypical white matter appears to predominantly occur in brain regions that are associated with key neuropsychological functions that are atypical in ADHD. Full text of this paper is available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8842077/

Data analysis of the NICAP longitudinal ADHD dataset is ongoing.