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The ipsilateral corticospinal responses to cross-education are dependent upon the motor-training intervention.
Leung, M, Rantalainen, T, Teo, WP, Kidgell, D
Experimental brain research. 2018;(5):1331-1346
Abstract
This study aimed to identify the ipsilateral corticospinal responses of the contralateral limb following different types of unilateral motor-training. Three groups performing unilateral slow-paced strength training (SPST), non-paced strength training (NPST) or visuomotor skill training (VT) were compared to a control group. It was hypothesised that 4 weeks of unilateral SPST and VT, but not NPST, would increase ipsilateral corticospinal excitability (CSE) and reduce short-interval cortical inhibition (SICI), resulting in greater performance gains of the untrained limb. Tracking error of the untrained limb reduced by 29 and 41% following 2 and 4 weeks of VT. Strength of the untrained limb increased by 8 and 16% following 2 and 4 weeks of SPST and by 6 and 13% following NPST. There was no difference in cross-education of strength or tracking error. For the trained limb, SPST and NPST increased strength (28 and 26%), and VT improved by 47 and 58%. SPST and VT increased ipsilateral CSE by 89 and 71% at 2 weeks. Ipsilateral CSE increased 105 and 81% at 4 weeks following SPST and VT. The NPST group and control group showed no changes at 2 and 4 weeks. SPST and VT reduced ipsilateral SICI by 45 and 47% at 2 weeks; at 4 weeks, SPST and VT reduced SICI by 48 and 38%. The ipsilateral corticospinal responses are determined by the type of motor-training. There were no differences in motor performance between SPST, NPST and VT. The data suggests that the corticospinal responses to cross-education are different and determined by the type of motor-training.
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2.
Cross-education of wrist extensor strength is not influenced by non-dominant training in right-handers.
Coombs, TA, Frazer, AK, Horvath, DM, Pearce, AJ, Howatson, G, Kidgell, DJ
European journal of applied physiology. 2016;(9):1757-69
Abstract
PURPOSE Cross-education of strength has been proposed to be greater when completed by the dominant limb in right handed humans. We investigated whether the direction of cross-education of strength and corticospinal plasticity are different following right or left limb strength training in right-handed participants. METHODS Changes in strength, muscle thickness and indices of corticospinal plasticity were analyzed in 23 adults who were exposed to 3-weeks of either right-hand strength training (RHT) or left-hand strength training (LHT). RESULTS Maximum voluntary wrist extensor strength in both the trained and untrained limb increased, irrespective of which limb was trained, with TMS revealing reduced corticospinal inhibition. CONCLUSIONS Cross-education of strength was not limited by which limb was trained and reduced corticospinal inhibition was not just confined to the trained limb. Critically, from a behavioral perspective, the magnitude of cross-education was not limited by which limb was trained.
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3.
Induction of cortical plasticity and improved motor performance following unilateral and bilateral transcranial direct current stimulation of the primary motor cortex.
Kidgell, DJ, Goodwill, AM, Frazer, AK, Daly, RM
BMC neuroscience. 2013;:64
Abstract
BACKGROUND Transcranial direct current stimulation (tDCS) is a non-invasive technique that modulates the excitability of neurons within the primary motor cortex (M1). Research shows that anodal-tDCS applied over the non-dominant M1 (i.e. unilateral stimulation) improves motor function of the non-dominant hand. Similarly, previous studies also show that applying cathodal tDCS over the dominant M1 improves motor function of the non-dominant hand, presumably by reducing interhemispheric inhibition. In the present study, one condition involved anodal-tDCS over the non-dominant M1 (unilateral stimulation) whilst a second condition involved applying cathodal-tDCS over the dominant M1 and anodal-tDCS over non-dominant M1 (bilateral stimulation) to determine if unilateral or bilateral stimulation differentially modulates motor function of the non-dominant hand. Using a randomized, cross-over design, 11 right-handed participants underwent three stimulation conditions: 1) unilateral stimulation, that involved anodal-tDCS applied over the non-dominant M1, 2) bilateral stimulation, whereby anodal-tDCS was applied over the non-dominant M1, and cathodal-tDCS over the dominant M1, and 3) sham stimulation. Transcranial magnetic stimulation (TMS) was performed before, immediately after, 30 and 60 minutes after stimulation to elucidate the neural mechanisms underlying any potential after-effects on motor performance. Motor function was evaluated by the Purdue pegboard test. RESULTS There were significant improvements in motor function following unilateral and bilateral stimulation when compared to sham stimulation at all-time points (all P < 0.05); however there was no difference across time points between unilateral and bilateral stimulation. There was also a similar significant increase in corticomotor excitability with both unilateral and bilateral stimulation immediately post, 30 minutes and 60 minutes compared to sham stimulation (all P < 0.05). Unilateral and bilateral stimulation reduced short-interval intracortical inhibition (SICI) immediately post and at 30 minutes (all P < 0.05), but returned to baseline in both conditions at 60 minutes. There was no difference between unilateral and bilateral stimulation for SICI (P > 0.05). Furthermore, changes in corticomotor plasticity were not related to changes in motor performance. CONCLUSION These results indicate that tDCS induced behavioural changes in the non-dominant hand as a consequence of mechanisms associated with use-dependant cortical plasticity that is independent of the electrode arrangement.
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4.
Corticomotor plasticity following unilateral strength training.
Goodwill, AM, Pearce, AJ, Kidgell, DJ
Muscle & nerve. 2012;(3):384-93
Abstract
INTRODUCTION We used transcranial magnetic stimulation (TMS) to investigate 3 weeks of unilateral leg strength training on ipsilateral motor cortex (iM1) excitability, and short-latency intracortical inhibition (SICI). METHODS Right leg dominant participants (n = 14) were randomly divided into either a strength training (ST) or control group. The ST group completed 9 training sessions (4 sets of 6 to 8 repetitions of single right leg squats). RESULTS We observed a 41% increase in right leg strength, and a 35% increase in strength of the untrained left leg (P < 0.01). There was a significant increase in motor evoked potential (MEP) amplitude recruitment curve for the untrained left leg (P < 0.01). SICI of the iM1 decreased by 21% for the untrained left leg (P < 0.01). CONCLUSIONS The findings provide evidence for corticomotor adaptation for unilateral leg strength training within the iM1 that is modulated by changes in interhemispheric inhibition.
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5.
Evidence for developmental programming of cerebral laterality in humans.
Jones, A, Osmond, C, Godfrey, KM, Phillips, DI
PloS one. 2011;(2):e17071
Abstract
Adverse fetal environments are associated with depression, reduced cognitive ability and increased stress responsiveness in later life, but underlying mechanisms are unknown. Environmental pressures on the fetus, resulting from variations in placental function and maternal nutrition, health and stress might alter neurodevelopment, promoting the development of some brain regions over others. As asymmetry of cerebral activity, with greater right hemisphere activity, has been associated with psychopathology, we hypothesized that regional specialization during fetal life might be reflected persistently in the relative activity of the cerebral hemispheres. We tested this hypothesis in 140 healthy 8-9 year-old children, using tympanic membrane temperature to assess relative blood flow to the cerebral hemispheres at rest and following psychosocial stress (Trier Social Stress Test for Children). Their birth weight and placental weight had already been measured when their mothers took part in a previous study of pregnancy outcomes. We found that children who had a smaller weight at birth had evidence of greater blood flow to the right hemisphere than to the left hemisphere (r = -.09, P = .29 at rest; r = -.18, P = .04 following stress). This finding was strengthened if the children had a relatively low birth weight for their placental weight (r = -.17, P = .05 at rest; r = -.31, P = .0005 following stress). Our findings suggest that lateralization of cerebral activity is influenced persistently by early developmental experiences, with possible consequences for long-term neurocognitive function.
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6.
The influence of partial implant-supported restorations on chewing side preference.
Nissan, J, Berman, O, Gross, O, Haim, B, Chaushu, G
Journal of oral rehabilitation. 2011;(3):165-9
Abstract
This study aimed at determining whether the individual's chewing side preference is affected by local effects, produced by the presence of implant-supported restorations. The test group included 81 patients with partial implant-supported prosthesis. The control group included 108 subjects with no implants. All subjects went through a series of laterality tests for chewing and tasks (hand, foot, eye and ear) side preference. The preferred chewing side (PCS) was determined by observing the first stroke of the chewing cycle during chewing a gum. A positive and significant correlation between the chewing side preference and the subject's sidedness during the different tasks was examined, by performing four Phi correlation tests for: chewing and handedness(r = 0·54; P < 0·001); chewing and footedness (r = 0·49; P < 0·001); chewing and eyedness (r = 0·65; P < 0·001) and chewing and earedness (r = 0·66, P < 0·001). Of the subjects, 78·3% preferred the right side for chewing, 19·1% preferred the left and 2·1% had no clear side preference. There was no statistical difference in chewing side preference distribution between genders. The distribution of chewing side preference was not significantly affected by the location of missing teeth or implants. In conclusion, implant placement will not affect PCS. Therefore, information on chewing side preference should be part of the routine preoperative examination for implant-supported restorations to provide a better treatment plan in those cases that the implant-supported restoration will be on the PCS.
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7.
Amelioration by mecobalamin of subclinical carpal tunnel syndrome involving unaffected limbs in stroke patients.
Sato, Y, Honda, Y, Iwamoto, J, Kanoko, T, Satoh, K
Journal of the neurological sciences. 2005;(1-2):13-8
Abstract
Our previous study showed that overuse of the nonparetic hand and wrist of the nonparetic side following stroke result in significantly more abnormal on the nonparetic side than on the hemiparetic side in terms of electrophysiologic indices of median nerve function. The purpose of this study was to evaluate the effects of the orally administered mecobalamin, an analogue of vitamin B12, for carpal tunnel syndrome (CTS) in the nonparetic side in patients following stroke. In a randomized open label and prospective study of stroke patients, 67 received of 1500 mug mecobalamin daily for 2 years, and the remaining 68 (untreated group) did not. At baseline, sensory nerve conduction velocity, motor nerve conduction velocity, sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency, palm-to-wrist SNAP, motor nerve conduction velocity compound motor action potentials, and distal motor latency of median nerve were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Before the treatment 21 patients (31%) of untreated and 20 patients (30%) of treated group met electrophysiologic criteria for CTS. Sensory impairment of the nonparetic side had lessened in the treated group. After 2 years, all electrophysiologic indices of nonparetic side were significantly improved in the treated group compared with those in the untreated group. The improvement from baseline of electrophysiologic parameters in sensory nerve in the treated group was greater than the improvement measured in motor nerve. There were no side effects. Oral mecobalamin treatment is a safe and potentially beneficial therapy for CTS in stroke patients.