Detrimental neural control of precision grip lifts in children with ADHD

The aim was to investigate the performance of children with attention-defic it-hyperactivity disorder (ADHD) in tasks involving motor-memory representa tions. A special grip object recorded forces generated by the fingertips du ring a precision grip-lift task. Common objects were lifted from a linear s cale. Twenty-five boys with ADHD were evaluated and grouped according to th e presence (ADHD+) or absence (ADHD) of movement dysfunction using the Move ment Assessment Battery for Children (Henderson and Sugden 1992). Mean grou p 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-mat ched 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 movem ent. They also had difficulties in adapting the motor output to target diff erent weights, suggesting deficient anticipatory parameter control based on memory representations. The results suggest that in some children motor pr oblems are due to detrimental neural control functions rather than core sym ptoms of ADHD.