Posterior Alpha Oscillations as an Index for the Attentional Bias in Children with Attentional Deficit Hyperactivity Disorder

Until recently, the nature of EEG abnormalities in children with Attention
Deficit Hyperactivity Disorder (ADHD) has not been decisive yet. The alpha
activity (8-14 Hz) is regarded the most fundamental and invariant component of
brain responses. According to the *inhibition timing hypothesis*, alpha
activity is thought to be involved in the suppression of irrelevant
information. In line with this hypothesis, attentional tasks in healthy
subjects have been related to higher occipital alpha power contralateral to the
unattended side than ipsilateral to the unattended side, defined by the alpha
lateralization index (ALI). ADHD might therefore be explained by an inability
to control posterior alpha and thus a deficit in the allocation of
visio-spatial attention. A recent study in adults with ADHD showed that subject
with ADHD have an attentional response bias to the right visual field compared
to the left visual field. Subjects without ADHD did not show a similar bias. In
the ALI, contrasting the difference found in healthy controls, no difference
was found between the cue and no cue condition in participants with ADHD. Since
both cognitive capacity and alpha-activity change as children get older, the
attentional bias found in adults with ADHD cannot be generalized towards
children with ADHD. Although resting state measurements in children with ADHD
have shown excess right hemisphere power to be 8 times as likely to occur as
excess left hemisphere power a direct link to cognitive performance needs to be
tested in children with ADHD.

Investigate the hypothesis that children with ADHD have difficulty with the
allocation of visio-spatial attention related to an inability to control
posterior alpha. A paradigm will be used in which the aim is to address covert
attention as similar recent studies did in adults with ADHD.

Alpha activity will be measured using EEG while performing a covert attention
task. Next, the alpha lateralization index will be calculated and correlated to
behavioural responses and severity of ADHD.

Children and their parents will have to visit the lab twice. The duration of
the first visit will depend on the necessity of doing an IQ measurement. As a
rule, only children in the ADHD-group will have had such a recent measurement.
If no recent measurement has been performed, a shortened IQ measurement will be
done in 45 minutes. During the first visit, the task that will be performed
during the second visit will be practiced for 8 minutes. In addition, the child
will be asked to do a paper and pencil task taking a couple of minutes while
the parent/representative fills out a questionnaire. Finally, the procedure of
the next visit will be explained. Following, the second visit will consist of
an EEG-measurement of approximately 90 minutes, including preparation, a short
practice session, and the actual task. Participation is not associated with any
indications of risks.

Benefit and group relatedness: Participation is of great importance since
generalization of recently obtained new insights on the nature of abnormalities
related to ADHD, will not be possible without measurement in this specific
target group. The brain develops during childhood and it is not clear yet what
ALI looks like in typically developing children, therefore it is important to
compare children with ADHD with typically developing children.