Department of Psychology, Tufts University, United States; Department of Psychiatry and the Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, United States.
Department of Psychology, Tufts University, United States.
Neuroimage Clin. 2017 Dec 21;18:74-85. doi: 10.1016/j.nicl.2017.12.026. eCollection 2018.
Lexico-semantic disturbances are considered central to schizophrenia. Clinically, their clearest manifestation is in language production. However, most studies probing their underlying mechanisms have used comprehension or categorization tasks. Here, we probed automatic semantic activity prior to language production in schizophrenia using event-related potentials (ERPs).
19 people with schizophrenia and 16 demographically-matched healthy controls named target pictures that were very quickly preceded by masked prime words. To probe automatic semantic activity prior to production, we measured the N400 ERP component evoked by these targets. To determine the origin of any automatic semantic abnormalities, we manipulated the type of relationship between prime and target such that they overlapped in (a) their semantic features (semantically related, e.g. "cake" preceding a < picture of a pie >, (b) their initial phonemes (phonemically related, e.g. "stomach" preceding a < picture of a starfish >), or (c) both their semantic features and their orthographic/phonological word form (identity related, e.g. "socks" preceding a < picture of socks >). For each of these three types of relationship, the same targets were paired with unrelated prime words (counterbalanced across lists). We contrasted ERPs and naming times to each type of related target with its corresponding unrelated target.
People with schizophrenia showed abnormal N400 modulation prior to naming identity related (versus unrelated) targets: whereas healthy control participants produced a smaller amplitude N400 to identity related than unrelated targets, patients showed the opposite pattern, producing a larger N400 to identity related than unrelated targets. This abnormality was specific to the identity related targets. Just like healthy control participants, people with schizophrenia produced a smaller N400 to semantically related than to unrelated targets, and showed no difference in the N400 evoked by phonemically related and unrelated targets. There were no differences between the two groups in the pattern of naming times across conditions.
People with schizophrenia can show abnormal neural activity associated with automatic semantic processing prior to language production. The specificity of this abnormality to the identity related targets suggests that that, rather than arising from abnormalities of either semantic features or lexical form alone, it may stem from disruptions of mappings (connections) between the meaning of words and their form.
词汇语义障碍被认为是精神分裂症的核心。临床上，它们最明显的表现是在语言产生中。然而，大多数探究其潜在机制的研究都使用了理解或分类任务。在这里，我们使用事件相关电位（ERP）在精神分裂症患者语言产生之前探测自动语义活动。
19 名精神分裂症患者和 16 名在人口统计学上匹配的健康对照者命名了目标图片，这些图片很快被掩蔽的启动词所引导。为了探测产生之前的自动语义活动，我们测量了这些目标引发的 N400 ERP 成分。为了确定任何自动语义异常的起源，我们操纵了启动词和目标词之间的关系类型，使它们在（a）语义特征上重叠（语义相关，例如“蛋糕”之前是“<一个馅饼的图片>”），（b）它们的初始音素上重叠（音位相关，例如“胃”之前是“<一个海星的图片>”），或（c）它们的语义特征和正字法/音位词形上重叠（身份相关，例如“袜子”之前是“<袜子的图片>”）。对于这三种关系类型中的每一种，都将相同的目标与不相关的启动词配对（在列表之间平衡）。我们将每个关系类型的相关目标和不相关目标的 ERP 和命名时间进行了对比。
精神分裂症患者在命名身份相关（与不相关）目标之前表现出异常的 N400 调制：与健康对照组相比，患者对身份相关目标的 N400 振幅较小，而对不相关目标的 N400 振幅较大。这种异常是身份相关目标特有的。与健康对照组一样，精神分裂症患者对语义相关目标的 N400 比不相关目标小，对音位相关和不相关目标的 N400 没有差异。两组在各条件下的命名时间模式没有差异。
精神分裂症患者在语言产生之前可以表现出与自动语义处理相关的异常神经活动。这种异常对身份相关目标的特异性表明，它不是源于语义特征或词汇形式的异常，而是源于词的意义与其形式之间的映射（连接）的中断。
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