Talelli P, Ewas A, Waddingham W, Rothwell J C, Ward N S
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College, London, UK.
Neuroimage. 2008 May 1;40(4):1772-81. doi: 10.1016/j.neuroimage.2008.01.039. Epub 2008 Feb 7.
Functional imaging studies of cortical motor systems in humans have demonstrated age-related reorganisation often attributed to anatomical and physiological changes. In this study we investigated whether aspects of brain activity during a motor task were influenced not only by age, but also by neurophysiological parameters of the motor cortex contralateral to the moving hand. Twenty seven right-handed volunteers underwent functional magnetic resonance imaging whilst performing repetitive isometric right hand grips in which the target force was parametrically varied between 15 and 55% of each subject's own maximum grip force. For each subject we characterised two orthogonal parameters, B(G) (average task-related activity for all hand grips) and B(F) (the degree to which task-related activity co-varied with peak grip force). We used transcranial magnetic stimulation (TMS) to assess task-related changes in interhemispheric inhibition from left to right motor cortex (IHIc) and to perform measures relating to left motor cortex excitability during activation of the right hand. Firstly, we found that B(G) in right (ipsilateral) motor cortex was greater with increasing values of age(2) and IHIc. Secondly, B(F) in left ventral premotor cortex was greater in older subjects and in those in whom contralateral M1 was less responsive to TMS stimulation. In both cases, neurophysiological parameters accounted for variability in brain responses over and above that explained by ageing. These results indicate that neurophysiological markers may be better indicators of biological ageing than chronological age and point towards the mechanisms by which reconfiguration of distributed brain networks occurs in the face of degenerative changes.
对人类皮质运动系统的功能成像研究表明，与年龄相关的重组现象通常归因于解剖学和生理学变化。在本研究中，我们调查了运动任务期间大脑活动的各个方面是否不仅受年龄影响，还受与运动手对侧的运动皮质神经生理参数的影响。27名右利手志愿者在进行重复性等长右手握力测试时接受了功能磁共振成像，其中目标力在每个受试者自身最大握力的15%至55%之间参数化变化。对于每个受试者，我们确定了两个正交参数，B(G)（所有握力的平均任务相关活动）和B(F)（任务相关活动与峰值握力的共变程度）。我们使用经颅磁刺激（TMS）来评估从左到右运动皮质的半球间抑制（IHIc）中与任务相关的变化，并在右手激活期间进行与左运动皮质兴奋性相关的测量。首先，我们发现随着年龄(2)和IHIc值的增加，右侧（同侧）运动皮质中的B(G)更大。其次，在老年受试者以及对侧M1对TMS刺激反应较小的受试者中，左侧腹侧运动前皮质中的B(F)更大。在这两种情况下，神经生理参数解释了大脑反应中的变异性，其程度超过了由衰老所解释的变异性。这些结果表明，神经生理标志物可能比实际年龄更好地指示生物衰老，并指出了面对退行性变化时分布式脑网络重新配置的机制。
