Grady C L
Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ann N Y Acad Sci. 1996 Jan 17;777:14-21. doi: 10.1111/j.1749-6632.1996.tb34396.x.
Although many cognitive functions are affected by age, some are relatively maintained. There also are numerous age-related changes in brain structure, but not much is known about how these changes impact upon the alterations seen in cognition. In order to understand the basis for the reductions and sparings of cognitive function in the aged, experiments were carried out to compare regional cerebral blood flow (rCBF) and performance in young and old subjects on visual perceptual and memory tasks. In the first experiment, which examined the perception of faces and spatial locations, old subjects were as accurate as young subjects, and both groups had rCBF activation in fusiform gyrus during face matching and in superior parietal cortex during location matching. However, old subjects had less activation of prestriate cortex and more activation of frontal and lateral temporal cortex than did young subjects. The second experiment tested recognition memory for faces, a task on which old subjects were impaired. Young subjects had rCBF activation in left prefrontal and inferior temporal cortex and in right hippocampus during encoding of the faces, and in right prefrontal and parietal cortex during recognition. Old subjects showed no significant activation of the areas involved in encoding, but did have increased rCBF in right prefrontal cortex during recognition. These results suggest that the aging brain can demonstrate alterations of the functional systems involved in some cognitive processes, such as perception, that may serve as a compensatory mechanism to maintain performance. Failure to show such compensation, coupled with dysfunction of the areas primarily involved in processing may lead to more marked deficits in performance.
尽管许多认知功能会受到年龄的影响，但有些功能相对得以维持。大脑结构也存在众多与年龄相关的变化，但对于这些变化如何影响认知方面所观察到的改变，我们却知之甚少。为了理解老年人认知功能减退和保留的基础，我们开展了实验，比较年轻和老年受试者在视觉感知和记忆任务中的局部脑血流量（rCBF）及表现。在第一个实验中，研究面部和空间位置的感知，老年受试者与年轻受试者一样准确，并且两组在面部匹配时梭状回以及位置匹配时顶上叶皮质均有rCBF激活。然而，与年轻受试者相比，老年受试者纹状前皮质的激活较少，而额叶和颞叶外侧皮质的激活较多。第二个实验测试对面部的识别记忆，在这项任务中，老年受试者表现受损。年轻受试者在对面部进行编码时，左前额叶和颞下回皮质以及右海马体有rCBF激活，在识别时右前额叶和顶叶皮质有rCBF激活。老年受试者在编码所涉及的区域未显示出明显激活，但在识别过程中右前额叶皮质的rCBF确实增加了。这些结果表明，衰老的大脑在某些认知过程（如感知）中所涉及的功能系统可能会发生改变，这可能是一种维持表现的补偿机制。未能表现出这种补偿，再加上主要参与处理的区域功能失调，可能会导致表现上更明显的缺陷。
