Bashir Shahid, Perez Jennifer M, Horvath Jared C, Pena-Gomez Cleofe, Vernet Marine, Capia Anuhya, Alonso-Alonso Miguel, Pascual-Leone Alvaro
Department of Neurology, Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA, USA ; Faculty of Medicine, Department of Physiology, Autism Research and Treatment Center, King Saud University Riyadh, Saudi Arabia.
Department of Neurology, Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA, USA.
Front Aging Neurosci. 2014 Jun 10;6:111. doi: 10.3389/fnagi.2014.00111. eCollection 2014.
Aging is associated with changes in the motor system that, over time, can lead to functional impairments and contribute negatively to the ability to recover after brain damage. Unfortunately, there are still many questions surrounding the physiological mechanisms underlying these impairments. We examined cortico-spinal excitability and plasticity in a young cohort (age range: 19-31) and an elderly cohort (age range: 47-73) of healthy right-handed individuals using navigated transcranial magnetic stimulation (nTMS). Subjects were evaluated with a combination of physiological [motor evoked potentials (MEPs), motor threshold (MT), intracortical inhibition (ICI), intracortical facilitation (ICF), and silent period (SP)] and behavioral [reaction time (RT), pinch force, 9 hole peg task (HPT)] measures at baseline and following one session of low-frequency (1 Hz) navigated repetitive TMS (rTMS) to the right (non-dominant) hemisphere. In the young cohort, the inhibitory effect of 1 Hz rTMS was significantly in the right hemisphere and a significant facilitatory effect was noted in the unstimulated hemisphere. Conversely, in the elderly cohort, we report only a trend toward a facilitatory effect in the unstimulated hemisphere, suggesting reduced cortical plasticity and interhemispheric communication. To this effect, we show that significant differences in hemispheric cortico-spinal excitability were present in the elderly cohort at baseline, with significantly reduced cortico-spinal excitability in the right hemisphere as compared to the left hemisphere. A correlation analysis revealed no significant relationship between cortical thickness of the selected region of interest (ROI) and MEPs in either young or old subjects prior to and following rTMS. When combined with our preliminary results, further research into this topic could lead to the development of neurophysiological markers pertinent to the diagnosis, prognosis, and treatment of neurological diseases characterized by monohemispheric damage and lateralized motor deficits.
衰老与运动系统的变化相关，随着时间的推移，这些变化可能导致功能障碍，并对脑损伤后的恢复能力产生负面影响。不幸的是，围绕这些损伤背后的生理机制仍有许多问题。我们使用导航经颅磁刺激（nTMS），对一组年轻（年龄范围：19 - 31岁）和一组老年（年龄范围：47 - 73岁）的健康右利手个体的皮质脊髓兴奋性和可塑性进行了研究。在基线以及对右侧（非优势）半球进行一次低频（1Hz）导航重复经颅磁刺激（rTMS）后，通过生理指标[运动诱发电位（MEP）、运动阈值（MT）、皮质内抑制（ICI）、皮质内易化（ICF）和静息期（SP）]和行为指标[反应时间（RT）、捏力、9孔插钉试验（HPT）]相结合的方式对受试者进行评估。在年轻组中，1Hz rTMS对右侧半球有显著的抑制作用，在未受刺激的半球有显著的易化作用。相反，在老年组中，我们仅观察到未受刺激半球有易化作用的趋势，这表明皮质可塑性和半球间通讯减弱。为此，我们发现老年组在基线时半球间皮质脊髓兴奋性存在显著差异，与左侧半球相比，右侧半球的皮质脊髓兴奋性显著降低。相关性分析显示，在rTMS前后，年轻或老年受试者中，所选感兴趣区域（ROI）的皮质厚度与MEP之间均无显著关系。结合我们的初步结果，对该主题的进一步研究可能会导致开发出与以单半球损伤和单侧运动缺陷为特征的神经疾病的诊断、预后和治疗相关的神经生理标志物。
