Virginia Tech Carilion Research Institute, Roanoke, VA 24016, USA.
Bradley Department of Electrical and Computer Engineering, Blacksburg, VA, 24061, USA.
Sci Rep. 2016 Aug 23;6:31943. doi: 10.1038/srep31943.
Predictive coding models of brain function propose that top-down cortical signals promote efficient neural codes by carrying predictions of upcoming sensory events. We hypothesized that older brains would employ these codes more prominently given their longer repertoire of sensory experience. We measured the connectivity underlying stimulus-evoked responses in cortical visual networks using electroencephalography and dynamic causal modeling and found that in young adults with reported normal or corrected-to-normal vision, signals propagated from early visual regions and reverberated along reciprocal connections to temporal, parietal and frontal cortices, while in contrast, the network was driven by both early visual and prefrontal inputs in older adults with reported normal or corrected-to-normal vision. Previously thought of as exceptions to the rule of bottom-up signal propagation, our results demonstrate a prominent role for prefrontal inputs in driving vision in aged brains in line with lifespan-dependent predictive neural codes.
大脑功能的预测编码模型提出，自上而下的皮质信号通过携带对即将到来的感觉事件的预测，促进有效的神经编码。我们假设，由于老年人的感觉体验更为丰富，他们会更突出地利用这些编码。我们使用脑电图和动态因果建模来测量皮质视觉网络中刺激诱发反应的连接，发现在报告视力正常或矫正正常的年轻成年人中，信号从早期视觉区域传播，并沿着相互连接的回路在颞叶、顶叶和额叶皮质中回荡，而相比之下，在报告视力正常或矫正正常的老年成年人中，网络则同时受到早期视觉和前额叶输入的驱动。我们的研究结果表明，前额叶输入在驱动老年人大脑的视觉方面发挥了突出作用，与依赖寿命的预测性神经编码一致，这与之前被认为是顺向信号传播规律的例外情况相反。
