Effects of stimulant medication on the lateralisation of line bisection judgements of children with attention deficit hyperactivity disorder

Objectives-Deficits in the maintenance of attention may underlie problems i n attention deficit hyperactivity disorder (ADHD). Children with ADHD also show asymmetric attention deficits in traditional lateralisation and visuos patial orienting tasks, suggesting right hemispheric (and left hemispace) a ttentional disturbance. This study aimed to examine the lateralisation of s elective attention in ADHD; specifically, the effect of a moving, random do t background, and stimulant medication in the Line bisection task. Methods-The performance of children with ADHD, on and off methylphenidate, was examined using a computerised horizontal Line bisection task with movin g and blank backgrounds. Twenty children with a DSM-IV diagnosis of ADHD pa rticipated with 20 controls, individually matched for age, sex, grade at sc hool, and IQ. Twelve of the 20 children with ADHD were on stimulant medicat ion at the time of testing. Horizontal Lines of varying length were present ed in the centre of a computer screen, with either a blank background, or a moving, random dot field. The random dots moved either leftward or rightwa rd across the screen at either 40 mm/s or 80 mm/s. Results-The children with ADHD off medication bisected lines significantly further to the right compared with controls, who showed a small leftward er ror. Methylphenidate normalised the performance of the children with ADHD f or the task with the moving dots. Conclusions-These results support previous evidence for a right hemispheric hypoarousal theory of attentional dysfunction, and are consistent with the emerging picture of a lateralised dysfunction of frontostriatal circuitry in ADHD.