Börger N; van der Meere J
Laboratory of Experimental Psychology, Grote Kruisstratt 2/1, 9712 TS, Groningen, The Netherlands.
The goal of the current study was
to investigate whether poor motor control in children with Attention-Deficit
Hyperactivity Disorder (ADHD) was associated with a state regulation deficit.
For this purpose, 28 ADHD and 22 healthy children carried out two Go No-Go
tests: one with a fast stimulus presentation rate, and the other with a slow
stimulus presentation rate. Groups were compared on RT performance and on
specific cardiac measures, reflecting arousal, motor activation/inhibition, and
effort allocation. No group difference in the arousal measure (mean heart rate)
was found. Further, groups did not differ with respect to response inhibition:
in both the fast and slow condition, ADHD children made comparable numbers of
errors of commission to the control group, and the groups did not differ with
respect to the heart rate deceleration after the onset of the No-Go signal,
reflecting motor inhibition. Group differences were found with respect to motor
activation and effort allocation in the condition with a slow presentation
rate. In this condition: (1) ADHD children reacted more slowly to Go signals
than control children, suggesting poor motor activation; (2) the heart rate
deceleration before the onset of Go signals, which is believed to reflect motor
preparation, was less pronounced in the ADHD children; (3) after Go signals,
where a response was given, the cardiac shift from deceleration to
acceleration, indicating response initiation, was delayed in ADHD children; and
(4) ADHD children had greater heart rate variability (0.10 Hz component) than
the control group, indicating that less effort was allocated. No group
differences in motor activation and effort allocation were found in the
condition with a fast presentation rate of stimuli. We conclude, therefore,
that a slow presentation rate of stimuli brings the ADHD child in a non-optimal
activation state.