Detrimental neural control of precision grip lifts in children with ADHD

The aim was to investigate the performance of children with attention-deficit-hyperactivity disorder (ADHD) in tasks involving motor-memory representations. A special grip object recorded forces generated by the fingertips during a precision grip-lift task. Common objects were lifted from a linear scale. Twenty-five boys with ADHD were evaluated and grouped according to the presence (ADHD+) or absence (ADHD) of movement dysfunction using the Movement Assessment Battery for Children (Henderson and Sugden 1992). Mean group ages were 11.4 years (range 9.0 to 11.0 years) and 11.7 years (9.0 to 15.6 years), respectively. They were compared to a control group of 25 age-matched boys, mean group age 11.8 years (range 9.0 to 13.0 years). Variability of motor performance was predominant in the ADHD+ group. Several of these participants presented a higher grip-force output during the gripping movement. They also had difficulties in adapting the motor output to target different weights, suggesting deficient anticipatory parameter control based on memory representations. The results suggest that in some children motor problems are due to detrimental neural control functions rather than core symptoms of ADHD.