Maturation of inhibitory and excitatory motor cortex pathways in children

Division of Neuropediatrics and Muscular Disorders, Department of Pediatrics and Adolescent Medicine, University of Freiburg, Mathildenstrasse 1, 79106 Freiburg, Germany.
Brain & development (Impact Factor: 1.88). 04/2009; 31(7):562-7. DOI: 10.1016/j.braindev.2009.02.007
Source: PubMed


To study intracortical inhibition and facilitation with paired-pulse transcranial magnetic stimulation in children, adolescents and adults.
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 (>or=18 years), adolescents (> 10 and < 18 years) and children (<or=10 years).
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).
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.

Download full-text


Available from: Florian Heinen,
  • Source
    • "However, only a few SICI studies in pediatric populations contributed to the understanding of neuromotor maturation and motor skill deficits (Garvey and Mall, 2008; Schneider et al., 2008). To date, it is known that less SICI can be detected in M1 of healthy fullterm children as compared to adults (Mall et al., 2004; Walther et al., 2009), but no TMS data is available in the preterm population for tackling the underlying neural mechanisms of motor coordination disorders. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Our study aimed to test in 8 years old children born very prematurely whether a faulty primary motor cortex (M1) functioning could parallel visuomotor coordination difficulties. Ten very preterm children (PT; gestational age ≤32 weeks; 6 boys; 8 years 6 months, SD 4 months) were compared to seven healthy term peers (4 boys; 8 years 4 months, SD 4 months). Clinical assessment comprised two standardized tests for motor skills and visuomotor coordination. Transcranial magnetic stimulation (TMS) was applied over M1 area of the preactivated first dorsal interosseous muscle to measure the corticomotor excitability and the short intracortical inhibition (SICI). PT scores were significantly lower on the Developmental Test of Visual-Motor Integration (p=0.0018) and on the Movement Assessment Battery for Children (p=0.038). In parallel, the dominant hemisphere worked differently with no SICI in PT (p=0.009) and more variability of corticomotor excitability (p=0.001). These intertwined neurophysiological findings suggest that a faulty motor programming in the dominant M1 of PT could explain visuomotor coordination deficits. Our study contributes to the understanding of possible mechanisms that underlie motor difficulties commonly observed in children who were born premature. In addition, the effectiveness of rehabilitation interventions may be better understood by applying TMS as an outcome measure in the future.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 10/2011; 123(6):1191-9. DOI:10.1016/j.clinph.2011.09.017 · 3.10 Impact Factor
  • Source
    • "Sensorimotor cortex synaptic density decreases markedly in adolescence and plateaus in young adulthood before a further progressive reduction in synaptic density begins in the fourth decade (Huttenlocher, 1979, 1990; Huttenlocher and Dabholkar, 1997; Dickstein et al., 2007). Intracortical inhibition is not mature until adulthood and is reduced in the elderly (Peinemann et al., 2001; Mall et al., 2004; Walther et al., 2009). The morphological properties of alpha-motoneurons and their excitatory and inhibitory control mature during development and are altered in the elderly (O'Sullivan et al., 1991; Erim et al., 1999; Mc Donough et al., 2001; Mentis et al., 2002; Furlan et al., 2007; Carlin et al., 2008; Sibilla and Ballerini, 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: There is increasing evidence of the importance of synchronous activity within the corticospinal system for motor control. We compared oscillatory activity in the primary sensorimotor cortex [EEG of sensorimotor cortex (SMC-EEG)] and a motor neuronal pool [surface electromyogram of opponens pollicis (OP-EMG)], and their coherence in children (4-12 years of age), young adults (20-35 years of age), and elderly adults (>55 years of age). The ratio between lower (2-13 Hz) and higher (14-32 Hz) frequencies in both SMC-EEG and OP-EMG decreased with age, correlating inversely with motor performance. There was evidence for larger, more distributed cortical networks in the children and elderly compared with young adults. Corticomuscular coherence (CMC) was present in all age groups and shifted between frontal and parietal cortical areas. In children, CMC was smaller and less stationary in amplitude and frequency than in adults. Young adults had single peaks of CMC clustered near the modal frequency (23 Hz); multiple peaks with a broad spread of frequencies occurred in children and the elderly; the further the frequency of the maximum peak CMC was from 23 Hz, the poorer the performance. CMC amplitude was inversely related to performance in young adults but was not modulated in relation to performance in children and the elderly. We propose that progressive fine-tuning of the frequency coding and stabilization of the dynamic properties within and between corticospinal networks occurs during adolescence, refining the capacity for efficient dynamic communication in adulthood. In old age, blurring of the tuning between networks and breakdown in their integration occurs and is likely to contribute to a decrement in motor control.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 03/2010; 30(10):3663-74. DOI:10.1523/JNEUROSCI.5621-09.2010 · 6.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The developmental profile of the firing patterns and construction of synapse connection were studied in LTS interneurons of prefrontal cortex (PFC) in rats with age (from P7 to P30). We used whole cell patch-clamp recordings to characterize electrophysiological properties of LTS interneurons in PFC at different age stages, including the action potentials (APs), short-term plasticity (STP), evoked excitatory postsynaptic currents (eEPSCs), spontaneous excitatory postsynaptic currents (sEPSC), and spontaneous inhibitory postsynaptic current (sIPSC). The developmental profile of LTS interneurons in our research showed two phases changes. The early phase from P7-P11 to P16-P19 during which the development of individual LTS interneuron dominated and just some simple synaptic connections formed, the synaptic inputs from pyramidal cells play a promoting role for the maturation of LTS interneurons to some extent. This was based on the changes of APs, eEPSCs, and STP such as the curtailment of time course of APs, the increasing facilitation of STP before P16-P19 group. The late phase from P20-P23 to P > 27 during which the function of inhibitory cortex network enhanced and the characters of this inhibitory cortex network continually changed although in the oldest age group (P > 27) in our research. The frequency and amplitude of sIPSC showed continually changes, and at the same age group, the frequency ratios and amplitude ratios of sIPSC was higher than that of sEPSC. Our study showed a foundation to clarify mechanisms underlying the evolution in time of intrinsic neuronal membrane properties and their important roles in balancing the cortex network, providing an academic foundation for the pathological researching on some psychiatric and neurological disorders.
    Cellular and Molecular Neurobiology 11/2009; 30(4):543-55. DOI:10.1007/s10571-009-9478-z · 2.51 Impact Factor
Show more