David-Jürgens Marianne, Churs Lydia, Berkefeld Thomas, Zepka Roberto F, Dinse Hubert R
Institute for Neuroinformatics, Department of Theoretical Biology, Neural Plasticity Lab, Ruhr-University Bochum, Bochum, Germany.
PLoS One. 2008;3(10):e3399. doi: 10.1371/journal.pone.0003399. Epub 2008 Oct 14.
Getting older is associated with a decline of cognitive and sensorimotor abilities, but it remains elusive whether age-related changes are due to accumulating degenerational processes, rendering them largely irreversible, or whether they reflect plastic, adaptational and presumably compensatory changes. Using aged rats as a model we studied how aging affects neural processing in somatosensory cortex. By multi-unit recordings in the fore- and hindpaw cortical maps we compared the effects of aging on receptive field size and response latencies. While in aged animals response latencies of neurons of both cortical representations were lengthened by approximately the same amount, only RFs of hindpaw neurons showed severe expansion with only little changes of forepaw RFs. To obtain insight into parallel changes of walking behavior, we recorded footprints in young and old animals which revealed a general age-related impairment of walking. In addition we found evidence for a limb-specific deterioration of the hindlimbs that was not observed in the forelimbs. Our results show that age-related changes of somatosensory cortical neurons display a complex pattern of regional specificity and parameter-dependence indicating that aging acts rather selectively on cortical processing of sensory information. The fact that RFs of the fore- and hindpaws do not co-vary in aged animals argues against degenerational processes on a global scale. We therefore conclude that age-related alterations are composed of plastic-adaptive alterations in response to modified use and degenerational changes developing with age. As a consequence, age-related changes need not be irreversible but can be subject to amelioration through training and stimulation.
衰老与认知和感觉运动能力的衰退相关，但与年龄相关的变化是由于累积的退行性过程（使其在很大程度上不可逆转），还是反映了可塑性、适应性以及可能的代偿性变化，目前仍不清楚。我们以老年大鼠为模型，研究衰老如何影响体感皮层的神经处理。通过在前爪和后爪皮层图谱中进行多单元记录，我们比较了衰老对感受野大小和反应潜伏期的影响。在老年动物中，两个皮层表征的神经元反应潜伏期延长的幅度大致相同，但只有后爪神经元的感受野出现严重扩大，前爪感受野变化很小。为了深入了解步行行为的平行变化，我们记录了年轻和老年动物的足迹，结果显示出与年龄相关的普遍步行障碍。此外，我们发现后肢存在肢体特异性退化的证据，而在前肢未观察到这种情况。我们的结果表明，与年龄相关的体感皮层神经元变化呈现出区域特异性和参数依赖性的复杂模式，这表明衰老对感觉信息的皮层处理具有选择性作用。老年动物前爪和后爪的感受野不协同变化这一事实，反驳了整体范围内的退行性过程。因此，我们得出结论，与年龄相关的改变是由对使用方式改变的可塑性适应改变以及随年龄发展的退行性变化组成的。因此，与年龄相关的变化不一定是不可逆转的，而是可以通过训练和刺激得到改善。
