Cognitive Neurology and Alzheimer's Disease Center, Northwestern University, Chicago, Illinois 60611, USA.
J Neurosci. 2012 Apr 4;32(14):4848-55. doi: 10.1523/JNEUROSCI.5984-11.2012.
Primary progressive aphasia (PPA) is a neurodegenerative syndrome that causes a gradual atrophy of the left hemisphere language network, leading to impairments of object naming (anomia) and word comprehension. In 33 human subjects with PPA, object naming and word comprehension were explored with N400 potentials elicited by picture-word or picture-picture matching tasks. Two mechanisms of impairment were identified. In one group of patients, where the object name could be recognized but not retrieved during verbal naming, N400s in picture-word trials were also abnormal, revealing an associative basis for retrieval anomia. In these patients, a putative prephonological signal (i.e., lemma) evoked by the object picture appears to have become too weak to elicit retrieval, but not necessarily too weak to support the informationally less taxing process of recognition. A second group of PPA patients showed more severe naming deficits-the object name was neither verbalized nor recognized. Furthermore, nouns of the same category (but not those of other object categories) could not be identified as mismatches. This blurring of intracategory but not intercategory differentiation of word meaning was correlated with anterior temporal atrophy, predominantly in the left hemisphere, especially along the superior temporal gyrus. Although not part of the classic language network, this area appears critical for proceeding from generic to specific levels of word comprehension and object naming. N400 abnormalities emerged for lexical (picture-word) but not nonverbal (picture-picture) associations, supporting a dual-route rather than amodal organization of object concepts.
原发性进行性失语症（PPA）是一种神经退行性综合征，导致左半球语言网络逐渐萎缩，导致物体命名（命名障碍）和单词理解受损。在 33 名 PPA 患者中，通过图片-文字或图片-图片匹配任务引发的 N400 电位来探索物体命名和单词理解。确定了两种损伤机制。在一组患者中，物体名称在口头命名时可以识别但无法检索，图片-文字试验中的 N400 也异常，揭示了检索命名障碍的联想基础。在这些患者中，物体图片引发的假定的语音前信号（即词干）似乎变得太弱，无法引发检索，但不一定太弱，无法支持信息负担较小的识别过程。第二组 PPA 患者表现出更严重的命名缺陷-物体名称既未口头化也未识别。此外，同一类别的名词（但不是其他物体类别的名词）不能被识别为不匹配。这种单词含义的类内但不是类间区分的模糊与颞前萎缩有关，主要在左半球，尤其是沿上颞回。尽管不在经典语言网络中，但该区域对于从一般到特定水平的单词理解和物体命名至关重要。N400 异常出现在词汇（图片-文字）而不是非语言（图片-图片）关联中，支持物体概念的双通路而不是模态组织。
