Towards an Understanding of the Mechanism of Action of Methylphenidate in ADHD

Stop Signal Task,EEG,MRI

Approximately 1-in-20 children worldwide have Attention Deficit Hyperactivity Disorder
 (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.
 
 This project aims to ultimately improve clinical management of children with ADHD.
 Methylphenidate, a stimulant medication, is used as the first-option pharmacological
 treatment for ADHD and often successfully reduces problem behaviour. Although Methylphenidate
 can be extremely effective, it does not work for every child. There is currently no
 'objective' way (e.g., blood test or brain scan) to measure if a child is genuinely
 responding to Methylphenidate. Instead, clinicians must rely on reports from parents and
 teachers, an approach that is problematic and that often leads to delays in optimising ADHD
 treatment. The absence of a biological test to quantify Methylphenidate response is primarily
 because we do not understand exactly how Methylphenidate changes behaviours to produce the
 known beneficial effects. This lack of knowledge is despite the very common use of this
 medication.
 
 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 will be collected while children with ADHD are performing two computer-game like tasks.
 One task measures the child's ability to hold back impulsive actions (inhibition) and the
 other assesses how they learn from positive and negative outcomes (reward processing). The
 data from the two tasks, the EEG recording and the fMRI scan will be analysed using advanced
 computer-modelling approaches to determine exactly how Methylphenidate changes behaviour.
 
 This project is important because if we can understand the brain mechanisms affected by
 Methylphenidate, we can ultimately develop a computerised measure that will allow clinicians
 to predict whether a child is going to respond to this treatment 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.