Proefschrift_Broeders

Reward modulation of cognitive function: adult ADHD

ADHD (Faraone et al., 2005; Brookes et al., 2008; Franke et al., 2008; for a review, see Durston

et al., 2009; Gizer et al., 2009; Franke et al., 2010).

In summary, in this pilot study we tested the hypothesis that effects of reward motivation on

task switching and striatal BOLD signal vary as a function of

DAT1

genotype adult patients

with ADHD, when they were ON relative to OFF their methylphenidate regimen, compared

with healthy controls.

Methods

Participants

We present data from 23 patients with ADHD (mean + SE age 35.74 + 2.36; 14 men) and

26 healthy control participants (mean + SE age 38.08 + 2.00; 11 men). Patients visited our

centre on two occasions, once after intake of methylphenidate and once after withdrawal

from methylphenidate. Healthy controls were also tested on two occasions, without any

methylphenidate (

procedure

Initially we recruited 57 participants (29 patients with ADHD and 28 healthy controls) from

an ongoing study on ADHD and genetics, IMpACT-NL (Hoogman et al., 2011; Hoogman et

al., 2013; Onnink et al., 2014;

), in which they were tested

extensively, genotyped, and diagnosed (

table 4.1

). Patients were included if they met DSM-

IV-TR criteria for ADHD in childhood as well as adulthood. All participants were assessed

using the Diagnostic Interview for Adult ADHD (Kooij and Francken, 2007). The Structured

Clinical Interviews for DSM-IV (SCID-I and SCID-II) were administered. Assessments were

carried out by trained professionals (psychiatrists or psychologists). In addition, a quantitative

measure of clinical symptoms was obtained using the ADHD rating scale-IV (Kooij et al.,

2005). Exclusion criteria for participants were alcohol or substance addiction in the last 6

months, current psychosis, manic episodes, obsessive compulsive disorder or eating disorders

(assessed using SCID-I), full-scale IQ estimate < 70 (assessed using the Wechsler Adult

Intelligence Scale-III), neurological disorders, sensorimotor disabilities, and non-Caucasian

ethnicity. An additional exclusion criterion for healthy comparison subjects was a current or

past neurological or psychiatric disorder according to SCID-I.

Three patients did not complete the testing sessions. Two patients were excluded because they

did not follow instructions regarding methylphenidate withdrawal and/or intake (

procedure

)

and one because of excessive head movement. One healthy control participant was excluded

from analysis due to suboptimal quality of the structural data leading to normalization

difficulties, and one for meeting the criteria for an ADHD diagnosis according to the ADHD

rating scale-IV (Kooij et al., 2005) (

neuropsychological assessment

). Hence, 23 patients with

ADHD and 26 healthy controls were included in the final analyses.