Kroll N E A, Yonelinas A P, Kishiyama M M, Baynes K, Knight R T, Gazzaniga M S
Department of Psychology, University of California-Davis, 95616, USA.
J Cogn Neurosci. 2003 Aug 15;15(6):833-42. doi: 10.1162/089892903322370753.
Identification of visually presented words is facilitated by implicit memory, or visual priming, for past visual experiences with those words. There is disagreement over the neuro-anatomical substrates of this form of implicit memory. Several studies have suggested that this form of priming relies on a visual word-form system localized in the right occipital lobe, whereas other studies have indicated that both hemispheres are equally involved. The discrepancies may be related to the types of priming tasks that have been used because the former studies have relied primarily on word-stem completion tasks and the latter on tasks like word-fragment completion. The present experiments compared word-fragment and word-stem measurements of visual implicit memory in patients with right occipital lobe lesions and patients with complete callosotomies. The patients showed normal visual implicit memory on fragment completion tests, but essentially no visual priming on standard stem completion tests. However, when we used a set of word stems that had only one correct solution for each test item, as was true of the items in the fragment completion tests, the patients showed normal priming effects. The results indicate that visual implicit memory for words is not solely dependent upon the right hemisphere, rather it reflects changes in processing efficiency in bilateral visual regions involved in the initial processing of the items. However, under conditions of high lexical competition (i.e., multiple completion word stems), the lexical processes, which are dominant in the left hemisphere, overshadow the visual priming supported by the left hemisphere.
对那些单词过去的视觉体验所形成的内隐记忆，即视觉启动效应，有助于对视觉呈现单词的识别。对于这种形式的内隐记忆的神经解剖学基础存在分歧。几项研究表明，这种启动效应形式依赖于位于右枕叶的视觉词形系统，而其他研究则表明两个半球同等程度地参与其中。这些差异可能与所使用的启动任务类型有关，因为前者主要依赖于词干补全任务，而后者依赖于诸如单词片段补全之类的任务。本实验比较了右枕叶病变患者和完全胼胝体切开术患者在单词片段和词干方面的视觉内隐记忆测量。患者在片段补全测试中表现出正常的视觉内隐记忆，但在标准词干补全测试中基本没有视觉启动效应。然而，当我们使用一组每个测试项目只有一个正确答案的词干时，就像片段补全测试中的项目一样，患者表现出正常的启动效应。结果表明，对单词的视觉内隐记忆并不完全依赖于右半球，相反，它反映了参与项目初始处理的双侧视觉区域处理效率的变化。然而，在高词汇竞争条件下（即多个补全词干），左半球占主导的词汇加工过程掩盖了左半球支持的视觉启动效应。
