Investigating Delay Discounting and Reward Dependence in ADHD and comorbid conditions using fMRI*

Dysregulation of dopaminergic neurotransmission is one of the key mechanisms
underpinning attention deficit / hyperactivity disorder (ADHD) (DelCampo et al
2011), as well as underpinning the most common comorbid disorders (obesity,
addictions and affective disorders, Whiton et al 2015). The dopaminergic system
is an important link between attention deficit syndrome and the development of
the aforementioned comorbid disorders. One of the behavioral equivalents of the
dopaminergic system is the processing of rewards or positively evaluated
stimuli. Experimentally, this can be measured by two paradigms: "Delay
Discounting": deferred rewards appear to be less valuable than immediate
rewards (McClure 2004), and "reward anticipation": the timing of the reward and
the anticipation of a reward are temporally separated; Knutson et al 2000). At
present, the mechanism responsible for the association between ADHD and these
the comorbid disorders mentioned has not been experimentally studied.

To investigate the role of the dopaminergic system in reward discounting and
reward anticipation in ADHD and comorbid disorders. The study investigates the
following question: Do patients with ADHD without comorbidity differ from those
with ADHD and comorbidities (substance abuse, mood disorders or obesity) in
terms of dopaminergic involvement?

This is a fMRT approach to study the dopaminergic system in ADHD patients
without comorbid disorders (n = 34) as well as those with comorbid disorder
(substance abuse, depression or obesity, n = 34 in each case). So far, there is
no study that has investigated both "delay discounting" and "reward
anticipation" in the same subjects.

Participants will also undergo a 1-hour MRI session. The degree of anxiety and
pleasure will be monitored before and during the MRI session. If participants
show resistance, the procedure will be stopped immediately. Participants will
be 18-50 years old. There are no special risks associated with our research and
we have ample experience with all these types of procedures