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Abnormal early stages of task stimulus processing in children with attention-deficit hyperactivity disorder--evidence
J Yordanova1, T Banaschewski, V Kolev
1Institute of Physiology, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 23, 1113, Sofia, Bulgaria.
Insights
Children with attention-deficit hyperactivity disorder (ADHD) show altered early auditory processing, with larger and more phase-locked gamma band responses (GBRs) to right-side stimuli compared to controls. These findings suggest early sensory-motor integration deficits in ADHD.
Area of Science:
- Neuroscience
- Developmental Psychology
- Child Psychiatry
Background:
- Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention and hyperactivity.
- Early stages of stimulus processing may be affected in ADHD, impacting sensory-motor integration.
- Gamma band responses (GBRs) are sensitive neural oscillations implicated in various cognitive functions, including attention and sensory processing.
Purpose of the Study:
- To investigate attention-related differences in early auditory stimulus processing between children with ADHD and healthy controls.
- To analyze phase-locked gamma band responses (31-63 Hz) to auditory stimuli during a selective-attention task.
- To explore potential alterations in sensory-motor integration mechanisms in ADHD.
Main Methods:
- A total of 28 children (aged 9-12 years), including those with ADHD and matched healthy controls, participated.
- Participants performed a selective-attention task involving button presses to target stimuli.
- Auditory GBRs (0-120 ms) were analyzed using wavelet transform across 8 electrodes, evaluating power and phase-locking.
Main Results:
- Both groups exhibited frontal-central GBRs, stronger for target than non-target stimuli, without differentiating attended from unattended channels.
- Children with ADHD showed significantly larger and more phase-locked GBRs than controls, specifically for right-side stimuli.
- These enhanced GBRs in ADHD were observed irrespective of whether the right-side stimuli were attended or ignored.
Conclusions:
- Phase-locked gamma oscillations appear to reflect sensory-motor integration processes, linking auditory GBRs to motor task stimuli in children.
- Deviations in GBRs within the ADHD group suggest that early auditory stimulus processing mechanisms are altered.
- These alterations in ADHD are hypothesized to stem from underlying impairments in motor inhibition.
Objectives:
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.