title: Age and medication effects on rhythmic responses in ADHD: possible oscillatory mechanisms?
abstract: Voluntary motor responses in children with attention-deficit hyperactivity disorder (ADHD) may reflect underlying neuronal oscillatory mechanisms. The aims of this study were: (1) to corroborate the presence of rhythmic motor abnormalities on tapping test in children with attention-deficit hyperactivity disorder, shown in previous studies; (2) to delineate the characteristics of ADHD children demonstrating these rhythmic abnormalities; (3) to assess the impact of methylphenidate (Ritalin) on this abnormal motor phenomenon. The study was designed in a double blind manner. Sixty-four ADHD children aged 6-12 years and 60 matched controls underwent a finger tapping test (1-5 Hz). We measured the abnormal rhythmic tapping with and without methylphenidate treatment in a double blind design. Conventional statistical analysis was used to assess the correlation of the presence of motor abnormality with various clinical characteristics (such as degree of hyperactivity/impulsivity). Fifty-six percent of children with ADHD compared to 8% of controls demonstrated abnormal rhythmic responses at a mean frequency of 3.1+/-0.9 Hz. These erroneous voluntary movements were more common in children with a greater degree of hyperactivity, in younger children but not significantly altered by methylphenidate treatment. Surprisingly, abnormal rhythmic responses showed less variability than found for responses for which the tapping was adequately paced, suggesting different motor control processes for normal and abnormal paced tapping. We speculate that rhythmic tapping responses reflect abnormal oscillatory mechanisms involved in ADHD, exacerbated in younger children with ADHD and in those in whom the hyperactivity/impulsivity is more pronounced.
authors.affiliation: Neuropediatric Unit, Shaare Zedek Medical Center, P.O. Box 3235, Jerusalem, Israel. shmaryaho@hotmail.com
authors.forename: Hilla
authors.initials: H
authors.lastname: Ben-Pazi
authors.forename: Ruth S
authors.initials: RS
authors.lastname: Shalev
authors.forename: Varda
authors.initials: V
authors.lastname: Gross-Tsur
authors.forename: Hagai
authors.initials: H
authors.lastname: Bergman
mesh_terms: D000367:Age Factors; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000188:drug therapy*; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D002540:Cerebral Cortex / Q000187:drug effects; D002648:Child; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008774:Methylphenidate / Q000627:therapeutic use*; D009415:Nerve Net / Q000187:drug effects; D009991:Oscillometry; D011597:Psychomotor Performance / Q000187:drug effects*; D013998:Time Perception / Q000187:drug effects*
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate