Madden D J, Turkington T G, Coleman R E, Provenzale J M, DeGrado T R, Hoffman J M
Center for the Study of Aging and Human Development, Duke University Medical Center, Durham, North Carolina 27710, USA.
Neuroimage. 1996 Apr;3(2):127-42. doi: 10.1006/nimg.1996.0015.
We used H215O PET to investigate adult age differences in regional cerebral blood flow (rCBF) during the performance of a visual word identification task. The study participants were 20 healthy, right-handed men: 10 young adults between 18 and 27 years of age, and 10 older adults between 63 and 75 years of age. The word identification task comprised six blocks of test trials representing four task conditions; subjects responded manually. The task conditions varied with regard to whether semantic retrieval was required (e.g., word/nonword discrimination vs simple response to each stimulus) and with regard to the difficulty of visual encoding (e.g., words presented normally vs words with asterisks inserted between adjacent letters). Each subject performed all six trial blocks, concurrently with each of six H215O PET scans. Analyses of quantitative CBF data obtained from the arterial time-activity curve demonstrated a significant age-related decline in global CBF rate. Analyses of the changes in rCBF between task conditions indicated that retrieval of semantic information sufficient to distinguish words from nonwords is mediated by a ventral occipitotemporal cortical pathway. Specific areas within this pathway were also associated with visual encoding processes. Several rCBF activations were significantly greater for young adults than for older adults, indicating an age-related decline in processing efficiency within this ventral occipitotemporal pathway. Although the performance data demonstrated a greater age-related slowing for visual encoding than for semantic retrieval, these age-related performance changes were not associated with corresponding changes in rCBF activation.
我们使用H215O正电子发射断层扫描（PET）来研究成年人在执行视觉单词识别任务时脑血流量（rCBF）的区域差异。研究参与者为20名健康的右利手男性：10名年龄在18至27岁之间的年轻成年人，以及10名年龄在63至75岁之间的老年人。单词识别任务由代表四种任务条件的六个测试试验块组成；受试者进行手动反应。任务条件在是否需要语义检索（例如，单词/非单词辨别与对每个刺激的简单反应）以及视觉编码的难度（例如，正常呈现的单词与相邻字母之间插入星号的单词）方面有所不同。每个受试者执行所有六个试验块，同时进行六次H215O PET扫描中的每一次。从动脉时间-活动曲线获得的定量CBF数据分析表明，整体CBF率存在与年龄相关的显著下降。任务条件之间rCBF变化的分析表明，足以区分单词与非单词的语义信息检索是由枕颞腹侧皮质通路介导的。该通路内的特定区域也与视觉编码过程相关。与老年人相比，年轻成年人的几个rCBF激活明显更大，表明该枕颞腹侧通路内的处理效率存在与年龄相关的下降。尽管性能数据表明，与语义检索相比，视觉编码的年龄相关减慢更大，但这些与年龄相关的性能变化与rCBF激活的相应变化无关。
