Institute for Neuroinformatics, Department of Theoretical Biology, Neural Plasticity Laboratory, Ruhr-University Bochum, D-44780 Bochum, Germany.
Cereb Cortex. 2010 May;20(5):1208-16. doi: 10.1093/cercor/bhp185. Epub 2009 Sep 10.
Aging affects all levels of neural processing including changes of intracortical inhibition and cortical excitability. The paired-pulse stimulation protocol, the application of 2 stimuli in close succession, is used to investigate cortical excitability. The paired-pulse behavior is characterized by the fact that the second response is significantly suppressed at short interstimulus intervals (ISIs) but approaches the first response with increasing ISIs. However, there are controversial reports about the influence of age on paired-pulse behavior. We therefore used pairs of tactile stimuli (ISIs from tens to hundreds of milliseconds) to record extracellular responses of somatosensory cortical neurons of young and aged rats. Paired-pulse behavior was quantified as the ratio of the amplitude of the second response divided by the first. For all ISIs, we found significantly higher ratios in the old animals indicating reduced paired-pulse suppression (PPS). Evaluation of the single response components revealed a significant reduction of the response to the first stimulus for old animals but no age-dependent decrement to the second. Changes in PPS are usually mediated by modulating the second response characteristics. Thus, our data demonstrate reduced PPS due to an overall reduction of the first response as a form of modified PPS developing at old age.
衰老影响所有层次的神经处理，包括皮质内抑制和皮质兴奋性的变化。双脉冲刺激方案是在紧密的刺激序列中应用两个刺激来研究皮质兴奋性的。双脉冲行为的特点是，在短的刺激间隔（ISIs）下，第二个反应明显受到抑制，但随着 ISIs 的增加，第二个反应逐渐接近第一个反应。然而，关于年龄对双脉冲行为的影响存在争议的报道。因此，我们使用一对触觉刺激（ISIs 从几十毫秒到几百毫秒）来记录年轻和老年大鼠体感皮层神经元的细胞外反应。双脉冲行为的定量表示为第二个反应的幅度与第一个反应的幅度之比。在所有的 ISIs 中，我们发现老年动物的比值明显更高，这表明双脉冲抑制（PPS）降低。对单个反应成分的评估表明，老年动物对第一个刺激的反应明显降低，但对第二个刺激没有依赖性降低。PPS 的变化通常通过调节第二个反应特征来介导。因此，我们的数据表明，由于第一个反应的整体降低，PPS 降低，这是老年时出现的一种改良的 PPS 形式。
