Buckner R L, Koutstaal W, Schacter D L, Rosen B R
Department of Radiology, Massachusetts General Hospital, Nuclear Magnetic Resonance Center, Charlestown, USA.
Brain. 2000 Mar;123 Pt 3:620-40. doi: 10.1093/brain/123.3.620.
Changes in human brain activity associated with repetition priming during word generation were characterized across a series of neuroimaging and behavioural studies. Repetition priming was consistently observed behaviourally as a decrease in response latency for repeated items, and was found for both visually and aurally cued word-generation tasks. Brain imaging using whole-brain functional MRI identified neural correlates of these effects. The principal effect of priming was to reduce neural activity within regions that were already being used to perform the word-generation tasks. Repeated word generation in response to visual cues was correlated with anatomically selective reductions in activity within the left frontal cortex along the inferior frontal gyrus and inferior temporal regions and, to a lesser degree, in specific earlier visual regions. These reductions were reversed when new items were presented, indicating that they were item-specific. Repeated word generation in response to aural cues also showed anatomically selective activity reductions within the left frontal and inferior temporal regions, indicating that these activity reductions were not dependent on the perceptual modality of the cue. The auditory cortex showed minimal repetition-related reductions. The presence of activity within left frontal regions that decreases as a function of item repetition for both visual and auditory cues suggests that these reductions may underlie an amodal repetition-priming effect existing at processing stages involving lexical/semantic search and access. The surprising finding that activity reductions in the inferior temporal cortex can be linked to repetition of either visual or auditory cues further suggests that these regions may be modulated in a top-down fashion during repetition priming, independent of (or in parallel with) stimulus-driven perceptual processes. Taken collectively, the data converge on a neural correlate of lexical/semantic priming. Amodal lexical/semantic processes, which may be triggered initially by modality-specific cues, proceed via an interaction between frontal and posterior brain regions. These interdependent regions show activity reductions that correlate with facilitated task performance when items are repeated.
在一系列神经影像学和行为学研究中，对与单词生成过程中重复启动相关的人类大脑活动变化进行了表征。行为学上始终观察到重复启动表现为重复项目的反应潜伏期缩短，并且在视觉和听觉提示的单词生成任务中均有发现。使用全脑功能磁共振成像的脑成像确定了这些效应的神经关联。启动的主要作用是减少已经用于执行单词生成任务的区域内的神经活动。对视觉提示做出反应的重复单词生成与沿额下回和颞下区域的左额叶皮质内活动的解剖学选择性减少相关，在较小程度上与特定的早期视觉区域相关。当呈现新项目时，这些减少会逆转，表明它们是特定于项目的。对听觉提示做出反应的重复单词生成也显示出左额叶和颞下区域内解剖学选择性活动减少，表明这些活动减少不依赖于提示的感知方式。听觉皮层显示出与重复相关的最小减少。对于视觉和听觉提示，左额叶区域内的活动随着项目重复而减少，这表明这些减少可能是涉及词汇/语义搜索和访问的处理阶段存在的一种非模态重复启动效应的基础。颞下皮质活动减少可与视觉或听觉提示的重复相关这一惊人发现进一步表明，在重复启动期间，这些区域可能以自上而下的方式受到调节，独立于（或与）刺激驱动的感知过程并行。总体而言，数据汇聚于词汇/语义启动的神经关联。非模态词汇/语义过程最初可能由特定模态的提示触发，通过额叶和后脑区域之间的相互作用进行。当项目重复时，这些相互依赖的区域显示出与任务表现促进相关的活动减少。
