Abnormal early stages of task stimulus processing in children with attention-deficit hyperactivity disorder--evidence from event-related gamma oscillations.
OBJECTIVE
Attention-related differences in early stages of stimulus processing were assessed in healthy controls and children with attention-deficit hyperactivity disorder (ADHD) by analyzing phase-locked gamma band (31-63 Hz) responses to auditory stimuli in a selective-attention task.


METHODS
A total of 28 children aged 9-12 years (ADHD and matched healthy controls) pressed a button in response to each target stimulus presented at the attended side (right or left). Auditory gamma band responses (GBRs) within 0-120 ms were analyzed at 8 electrodes with wavelet transform. Effects of attended channel, stimulus type, and group were evaluated for GBR power and phase-locking.


RESULTS
For both groups, GBRs had a frontal-central distribution, were significantly larger and more strongly phase-locked to target than to non-target stimuli, and did not differentiate the attended from the unattended channel. ADHD children produced larger and more strongly phase-locked GBRs than controls only to right-side stimuli, irrespective of whether these were the attended or the ignored stimuli.


CONCLUSIONS
The association between auditory GBR and motor task stimulus in children suggests that phase-locked gamma oscillations may reflect processes of sensory-motor integration. ADHD-related deviations of GBRs indicate that early mechanisms of auditory stimulus processing are altered in ADHD, presumably as a result of impaired motor inhibition.
Yordanova
J
J
Institute of Physiology, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 23, 1113, Sofia, Bulgaria.
Banaschewski
T
T
Kolev
V
V
Woerner
W
W
Rothenberger
A
A
D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies