OBJECTIVEImpulsivity is one of the core symptoms of children with attention deficit hyperactivity disorder (ADHD). In order to understand the neuromechanism of the impulsive behaviors in ADHD children, this study investigated the specific functional areas of the brain by functional MRI.

METHODSThe subjects consisted of 10 ADHD children with impulsivity, 7 ADHD children without impulsivity and 9 normal children. A functional MRI examination was performed when the subjects were instructed to finish GO and STOP tasks with the GO-STOP impulsivity paradigm. The MRI data during the two tasks of GO and STOP were averaged and the corresponding activation regions between groups were compared.

RESULTSThe data from the GO task revealed that the main activation regions of the normal children included frontal pole (superior frontal gyrus, middle frontal gyrus and medial frontal gyrus); the main activation regions of ADHD children without impulsivity were cerebellum (posterior lobe and anterior lobe bouton) and cingulated gyrus; those of ADHD children with impulsivity were medial globus pallidus and insula. The data from the STOP task showed that the main activation regions of normal children included superior frontal gyrus and middle frontal gyrus; those of ADHD children without impulsivity were middle frontal gyrus and cingulate gyrus; those of ADHD children with impulsivity were uncus and putamen. The activation regions of ADHD children with impulsivity were much fewer than the other two groups.

CONCLUSIONSThe behavior of impulsivity-control involves a number of specific functional areas in the cerebral cortex. Compared with normal children, ADHD children without impulsivity have weaker brain function and brain activation, and ADHD children with impulsivity demonstrate much fewer brain activation regions, worse brain function and little awareness of the cerebral cortex.