Perceptual andMotor Inhibition in ADHD:Evidence for a specific impairment?

Objective: Inhibition, one of the core executive processes in executive functioning
(Miyake et al., 2000) is generally not considered as an unitary construct
(see for example, Friedman & Miyake, 2004; Nassauer & Halperin,
2003). Following the perceptual versus motor dissociation proposed by
Nassauer and Halperin (2003), we studied perceptual and motor inhibition
in children with AttentionDeficit andHyperactivity Disorder (ADHD). Participants and Methods: Sixteen 7-12 years old children with
ADHD and 30 matched control children were administered a version
of the Conflict Resolution task (Nassauer & Halperin, 2003) adapted
for children.
In this task, the perceptual inhibition task required the children to respond
to the direction of a dog (running towards the left or the right)
while ignoring its location (left or right) on a computer screen. In the
motor inhibition task, the children had to press a key corresponding to
the opposite direction of a centrally running dog.
Results: Comparisons analyses of inhibition performances between
ADHD children and matched controlled subjects showed that ADHD
children performed significantly less accurately for stimulus-stimulus
characteristic conflicts (i.e., perceptual inhibition) than for stimulus-
response conflicts (i.e., motor inhibition), which suggests a specific
impairment in perceptual inhibition in our group of ADHD
children.
Conclusions: In conclusion, this study supports the presence of two
forms of inhibition which can be differentiated and specifically impaired
in 7- to 12-year-old ADHD children.