Preliminary fMRI findings on the effects of event rate in adults with ADHD.
Inhibition problems in attention deficit hyperactivity disorder (ADHD) are sensitive to stimulus event rate. This pilot study explores the neural basis of this increased susceptibility to event rate in ADHD. Event-related functional magnetic resonance imaging was used in conjunction with the administration of a fast (1.5 s) and a slow (7 s) Go/No-Go task. Brain activity patterns and reaction times of ten young male adults with ADHD (two of whom were in partial remission) and ten healthy male controls were compared. The ADHD group responded slower than controls with greater variability but with similar number of errors. Accurate response inhibition in the ADHD group in the slow condition was associated with widespread fronto-striatal activation, including the thalamus. For correct Go trials only, the ADHD group compared with controls showed substantial under-activation in the slow condition. The observed abnormal brain activation in the slow condition in adults with ADHD supports a fronto-striatal etiology, and underlines a presumed activation regulation deficit. Larger sample sizes to further validate these preliminary findings are needed.
Behavioral Research Unit, Department of Pediatrics, Alberta Children's Hospital, University of Calgary, 2888 Shaganappi Trail NW, Calgary, AB T3B 6A8, Canada. libbe.kooistra@albertahealthservices.ca
Libbe
L
Kooistra
Jaap J
JJ
van der Meere
Jodi D
JD
Edwards
Bonnie J
BJ
Kaplan
Susan
S
Crawford
Bradley G
BG
Goodyear
D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000503:physiopathology*; D001931:Brain Mapping; D003342:Corpus Striatum / Q000033:anatomy & histology / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology; D056344:Executive Function / Q000502:physiology*; D005625:Frontal Lobe / Q000033:anatomy & histology / Q000503:physiopathology*; D006801:Humans; D007600:Judgment / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000503:physiopathology*; D009483:Neuropsychological Tests; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011930:Reaction Time / Q000502:physiology; D013788:Thalamus / Q000033:anatomy & histology / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult