Enhanced gamma-band activity in ADHD patients lacks correlation with memory performance found in healthy children.
Previous electrophysiological as well as imaging research has contributed to the understanding of impairments in attention, executive functions, and memory in patients with attention-deficit/hyperactivity disorder (ADHD). However, there is a lack of studies investigating ADHD related differences in the gamma range of human electroencephalogram (EEG), although gamma activity is strongly associated with cognitive processes impaired in ADHD patients and is also modulated by dopamine polymorphisms linked with ADHD. To close this gap, the present study compared gamma activity in ADHD children with that of healthy controls and correlated it with memory performance. EEG was recorded from 13 ADHD patients as well as 13 healthy control subjects during the encoding phase of a visual memory paradigm. In a subsequent recognition test, participants had to judge pictures as being old or new. Analysis of evoked gamma-band responses (GBRs) during stimulus encoding revealed a strong task-related enhancement for ADHD patients in parieto-occipital areas. Interestingly, this augmentation was not associated with recognition performance, whereas healthy subjects exhibited a strong positive correlation between evoked gamma activity during stimulus encoding and subsequent recognition performance. We interpret this finding as evidence of enhanced excitation levels and unspecific activation of processing resources in ADHD patients. Furthermore, enhanced GBRs in ADHD could also indicate a decrease of neuronal signal-to-noise ratio, partially caused by the genetic variations within the dopaminergic pathway of ADHD patients. The involved genetic polymorphisms have been shown to modulate evoked GBRs, which therefore could be a possible marker of impaired neurotransmission in ADHD.
Lenz
Daniel
D
Otto-von-Guericke-University Magdeburg, Department of Biological Psychology, P.O. Box 4120, 39016 Magdeburg, Germany.
Krauel
Kerstin
K
Schadow
Jeanette
J
Baving
Lioba
L
Duzel
Emrah
E
Herrmann
Christoph S
CS
D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000503:physiopathology*; D002648:Child; D015897:Comorbidity; D004298:Dopamine / Q000378:metabolism; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000033:anatomy & histology / Q000503:physiopathology; D010296:Parietal Lobe / Q000033:anatomy & histology / Q000503:physiopathology; D010775:Photic Stimulation; D011110:Polymorphism, Genetic / Q000235:genetics; D012016:Reference Values
D004298:Dopamine