Ryan D. Higgins

Reduced corticomotor excitability and motor skills development in children born preterm

•  Children born preterm commonly experience motor and cognitive difficulties, but the physiology underlying this dysfunction is unknown. •  We used transcranial magnetic stimulation techniques and age‐appropriate assessments of motor skills development to investigate neurodevelopment in 151 children born between 25 and 41 weeks of gestation. •  Reduced gestational age at birth was associated with a reduction in corticomotor excitability that persisted in late childhood, poorer development of manual dexterity skills and reduced hemispheric lateralization of hand preference. •  We suggest this reduced corticomotor excitability at least partly reflects reduced white matter integrity and functional connectivity in the brain regions subserving movement control. •  These findings show that preterm birth, which is increasingly common, impacts neuromotor development and related physiology into adolescence. Whether this altered neurophysiology and motor function persists in adulthood is unknown.

Male human motor cortex stimulus-response characteristics are not altered by aging

Evidence suggests that there are aging-related changes in corticospinal stimulus-response curve characteristics in later life. However, there is also limited evidence that these changes may only be evident in postmenopausal women and not in men. This study compared corticospinal stimulus-response curves from a group of young men [19.8 ± 1.6 yr (range 17-23 yr)] and a group of old men [n = 18, aged 64.1 ± 5.0 yr (range 55-73 yr)]. Transcranial magnetic stimulation (TMS) over the contralateral motor cortex was used to evoke motor potentials at a range of stimulus intensities in the first dorsal interosseous muscle of each hand separately. There was no effect of age group or hemisphere (i.e., left vs. right motor cortex) on motor evoked potential (MEP) amplitude or any other stimulus-response characteristic. MEP variability was strongly modulated by resting motor threshold but not by age. M-wave (but not F-wave) amplitude was reduced in old men, but expressing MEP amplitude as a ratio of M-wave amplitude did not reveal any age-related differences in cortically evoked stimulus-response characteristics. We conclude that male corticospinal stimulus-response characteristics are not altered by advancing age and that previously reported age-related changes in motor cortical excitability assessed with TMS are likely due to changes inherent in the female participants only. Future studies are warranted to fully elucidate the relationship between, and functional significance of, changes in circulating neuroactive sex hormones and motor function in later life.

Cutaneous afferent input does not modulate motor intracortical inhibition in ageing men

Afferent input has been shown to be a powerful modulator of cortical inhibition. Such modulation is likely to be important for the control of ongoing movement, but may also play a role in facilitating neuroplastic reorganisation. Human motor control and neuroplasticity both decline with ageing, whereas the efficacy of short‐interval intracortical inhibition (SICI) appears not to. We examined if ageing alters the efficacy of afferent modulation of SICI. Previously, electrical cutaneous stimulation of a finger has been shown to reduce SICI in the motor cortices of young adults. Paired‐pulse transcranial magnetic stimulation was used to assess SICI in the cortical representation of the first dorsal interosseous muscle. SICI was assessed separately under two conditions: with and without prior afferent input from electrical cutaneous stimulation of the index finger. Fifteen ‘young’ (20.1 ± 2.1 years) and 15 ‘old’ male humans (65.5 ± 3.9 years) were studied. SICI did not differ when young and old males were compared. However, when preceded by electrical cutaneous finger stimulation, SICI was reduced in young men but not old men. Reflex testing indicated preservation of the afferent volley to the cortex. These findings suggest that a contributing factor in the decline of motor function, and possibly neuroplasticity, with ageing is loss of SICI modulation, probably due to altered cortical sensorimotor integration of afferent input.

P17-13 Short-latency intracortical inhibition is not reduced by cutaneous afferent input in ageing men

P17-12 Electrophysiological evaluation of effects of aging on sensorimotor integration: a somatosensory evoked potential and corticomuscular coherence study N.M. Maurits1, I. Brons2, J.H. van der Hoeven1 1Department of Neurology, University Medical Center Groningen, Groningen, the Netherlands, 2Academic Medical Center, Clinical & Experimental Audiology, Amsterdam, the Netherlands Objective: This study evaluates somatosensory evoked potentials (SEPs) and corticomuscular coherence (CMC) under different conditions to investigate the effects of ageing on sensorimotor integration. Methods: During 128-channel SEP recording, periods of twenty seconds of isometric contraction of the abductor pollicis brevis at 30% maximum voluntary contraction (MVC) were alternated with relaxation periods of the same duration. Both periods started with ten seconds of (predominantly sensory) electrical stimulation of the median nerve at the wrist. This protocol was performed for twenty minutes for each hand separately. This set-up (Tecchio et al., 2006) yielded four different conditions (rest, motor activity only, sensory stimulation only, motor activity and sensory stimulation). The protocol was executed in 11 younger (23.6±3.0 years old, 5 males) and 11 older (65.0±2.8 years old, 6 males) healthy subjects. Results: SEP amplitudes and CMC were generally found to be increased in older subjects, independent of condition. SEP component amplitudes decreased during isometric contraction, to a similar extent for both groups. As a group, younger subjects only showed low coherences independent of condition, whereas older subjects showed a clear coherence peak within the beta band, which was significantly reduced in the sensorimotor condition compared to the motor condition. Maximum CMC was found for electrodes over contralateral sensorimotor areas, independent of age group. Conclusions: Elderly show a decrease in CMC during sensory stimulation, which is absent in young subjects, indicating an effect of age on sensorimotor integration. Furthermore, although earlier studies showed that beta CMC increases with age into adulthood, our study is the first to show that the increase in CMC may continue further into old age. These findings may have implications for the evaluation of disorders of sensorimotor integration, such as dystonia.

P11-15 Gestation length and fetal growth have independent effects on corticospinal development in children: the PREMOCODE study

J.B. Pitcher1, R.D. Higgins1, N.R. Burns2, J.S. Robinson1, T.J. Nettelbeck2, R.R. Haslam3, M.C. Ridding1 1Robinson Institute, School of Paediatrics & Reproductive Health, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia, 2School of Psychology, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia, 3Department of Neonatal Medicine, Womens & Childrens Hospital, Adelaide, Australia

P8.9 Cognitive processing speed is associated with motor cortex excitability but not gestational age at birth in children

P. Bocquillon1, J.-L. Bourriez2, E. Palmero-Soler3, A. Destee4, L. Defebvre5, P. Derambure1, K. Dujardin5 1Université Lille Nord de France, UDSL, Lab. Neurosciences Fonctionnelles et Pathologies, CNRS, FRE 3291, Clinical Neurophysiology Department, Lille University Medical Center, Lille, France, 2Lab. Neurosciences Fonctionnelles et Pathologies, CNRS, FRE 3291, Clinical Neurophysiology Department, Lille University Medical Center, Lille, France, 3Eemagine Medical Imaging Solutions GmbH, Berlin, Germany, 4Université Lille Nord de France, UDSL, Neurology and Movement Disorders Department, Lille University Medical Center, Lille, France, 5Université Lille Nord de France, UDSL, Lab. Neurosciences Fonctionnelles et Pathologies, CNRS, FRE 3291, Neurology and Movement Disorders Department, Lille University Medical Center, Lille, France

P11-16 Poor cognitive development is associated with reduced motor cortex excitability in children born preterm: the PREMOCODE study

J.B. Pitcher1, R.D. Higgins1, N.R. Burns2, J.S. Robinson1, T.J. Nettelbeck2, R.R. Haslam3, M.C. Ridding1 1Robinson Institute, School of Paediatrics & Reproductive Health, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia, 2School of Psychology, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia, 3Department of Neonatal Medicine, Womens & Childrens Hospital, Adelaide, Australia