Maturation of inhibitory and excitatory motor cortex pathways in children

• Published in: Brain & development (Tokyo. 1979) 2009-08, Vol.31 (7), p.562-567
• Main Authors: Walther, Michael, Berweck, Steffen, Schessl, Joachim, Linder-Lucht, Michaela, Fietzek, Urban M, Glocker, Franz X, Heinen, Florian, Mall, Volker
• Format: Article
• Language: English
• Subjects: Adolescent; Adolescent Development - physiology; Adult; Aging; Child; Child Development - physiology; Children; Cortical excitability; Efferent Pathways - growth & development; Efferent Pathways - physiology; Electromyography; Evoked Potentials, Motor; Female; Humans; Intracortical facilitation; Intracortical inhibition; Male; Motor Cortex - growth & development; Motor Cortex - physiology; Motor cortex maturation; Neural Inhibition - physiology; Neurology; Neuronal plasticity; Transcranial Magnetic Stimulation; Young Adult
• ISSN: 0387-7604; 1872-7131
• DOI: 10.1016/j.braindev.2009.02.007

Abstract Objective To study intracortical inhibition and facilitation with paired-pulse transcranial magnetic stimulation in children, adolescents and adults. Methods : Paired-pulse transcranial magnetic stimulation (interstimulus intervals (ISI): 1, 3, 5, 10 and 20 ms) was applied over the primary motor cortex (M1) in 30 healthy subjects (range 6–30 years, median age 15 years and 8 months, SD 7,9) divided in three groups: adults (⩾ 18 years), adolescents (> 10 and < 18 years) and children (⩽ 10 years). Results : We observed significantly less intracortical inhibition (SICI) in children’s M1 compared to that of adults. Adolescents showed significantly less SICI at the 5 ms interval than did adults. No significant differences were apparent in intracortical facilitation (ICF). Conclusion : We postulate that, as in adults, the maturing M1 possesses horizontal glutamatergic cross-links that represent the neuronal substrate of excitatory intracortical pathways. GABAergic interneurons, the neuronal substrate of inhibitory intracortical pathways, mature between childhood and adulthood. Reduced GABAergic inhibition may facilitate neuronal plasticity and motor learning in children.