Naccarato M, Calautti C, Jones P S, Day D J, Carpenter T A, Baron J-C
Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Box 83, Cambridge CB2 2QQ, UK.
Neuroimage. 2006 Sep;32(3):1250-6. doi: 10.1016/j.neuroimage.2006.05.003. Epub 2006 Jun 27.
Normal aging is generally associated with declining performance in cognitive and fine motor tasks. Previous functional imaging studies have been inconsistent regarding the effect of aging on primary motor cortex (M1) activation during finger movement, showing increased, unchanged or decreased activation contralaterally, and more consistently increased activation ipsilaterally. Furthermore, no study has addressed the effect of age on M1 hemispheric activation balance. We studied 18 optimally healthy right-handed subjects, age range 18-79 years (mean +/- SD: 47 +/- 17) using 3 T fMRI and right index finger-thumb tapping auditory-paced at 1.25 Hz. The weighted Laterality Index (wLI) for M1 was obtained according to Fernandez et al. (2001) [Fernandez, G., de Greiff, A., von Oertzen, J., Reuber, M., Lun, S., Klaver, P., et al. 2001. Language mapping in less than 15 min: real-time functional MRI during routine clinical investigation. Neuroimage 14 585-594], with some modifications. The wLI, as well as the total activation on each side, were assessed against age using non-parametric correlation. There was a highly significant negative correlation between age and wLI such that the older the subjects, the lower the wLI. Furthermore, there was a highly significant positive correlation between total activation for ipsilateral M1 and age, and a nearly significant trend for contralateral M1. This study documents that during execution of a simple paced motor task, the older the subject the less lateralized the M1 activation balance as a result of increasing amount of activation on both sides, more significantly so ipsilaterally. Thus, in aging, enhanced M1 recruitment bilaterally is required to produce the same motor performance, suggesting a compensatory process. These findings are in line with cognitive studies indicating a tendency for the aging brain to reduce its functional lateralization, perhaps from less efficient transcallosal connections.
正常衰老通常与认知和精细运动任务表现下降有关。先前的功能成像研究在衰老对手指运动过程中初级运动皮层（M1）激活的影响方面存在不一致的结果，显示对侧激活增加、不变或减少，而同侧激活更一致地增加。此外，尚无研究探讨年龄对M1半球激活平衡的影响。我们使用3T功能磁共振成像（fMRI）对18名年龄在18 - 79岁（平均±标准差：47±17）的最佳健康右利手受试者进行了研究，让他们以1.25Hz的频率在听觉节拍下进行右手食指 - 拇指轻敲。根据费尔南德斯等人（2001年）[费尔南德斯，G.，德格雷夫，A.，冯·厄尔岑，J.，鲁伯，M.，伦，S.，克拉弗，P.等。2001年。在不到15分钟内进行语言映射：常规临床研究期间的实时功能磁共振成像。《神经影像学》14 585 - 594]的方法，并做了一些修改，获得了M1的加权利手指数（wLI）。使用非参数相关性分析wLI以及每侧的总激活与年龄的关系。年龄与wLI之间存在高度显著的负相关，即受试者年龄越大，wLI越低。此外，同侧M1的总激活与年龄之间存在高度显著的正相关，对侧M1也有近乎显著的趋势。这项研究表明，在执行简单的节拍运动任务时，受试者年龄越大，由于两侧激活量增加，M1激活平衡的侧化程度越低，同侧更为明显。因此，在衰老过程中，需要双侧增强M1的募集才能产生相同的运动表现，这表明存在一种代偿过程。这些发现与认知研究一致，表明衰老大脑有减少其功能侧化的趋势，这可能是由于胼胝体连接效率降低所致。
