Salisbury Dean F
Cognitive Neuroscience Laboratory, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
J Neurolinguistics. 2010 May 1;23(3):240. doi: 10.1016/j.jneuroling.2009.10.001.
Disordered thinking in schizophrenia may be a consequence of the selection of conceptual associates of dominant meanings of ambiguous words despite contextual information suggesting subordinate meanings are more appropriate. Previous work using short sentences showed a large N400 event-related potential to subordinate meaning associates and a behavioral semantic bias, but results were variable. The current experiment used word pairs to simplify the procedure and to less tax memory maintenance. Furthermore, hemispheric responses were compared, as evidence suggests the left hemisphere may select dominant meanings, while the right hemisphere may keep all possible meanings active. Subjects indicated whether two words (CUE, TARGET) were related. The CUE, presented for 1 second, could be an ambiguous or an unambiguous noun, and the TARGET, presented 1.25 seconds after the onset of the CUE, was a dominant or subordinate associate, or a related or an unrelated word, respectively. The N400-effect was calculated from difference waveforms over 400-600 msec. Groups (23 schizophrenia, 25 matched controls) showed significantly different N400-effects to the words (group x word, p =.04). Controls showed a graded response, with dominant < subordinate < unrelated. Schizophrenia patients showed the largest N400-effect to subordinate associates, with less activity to dominant meaning associates and unrelated words. Both groups showed a right hemisphere distribution to unrelated words and substantial left hemisphere activation to subordinate associates (word x hemisphere, p <.001). These data support a semantic bias in schizophrenia. They also demonstrate a special role of the right hemisphere in maintaining broad homograph meaning hierarchies. This hemispheric specialization appears to be intact in schizophrenia.
精神分裂症中的思维紊乱可能是由于尽管上下文信息表明从属意义更合适，但却选择了具有歧义性词语的主导意义的概念关联项。先前使用短句的研究表明，对于从属意义关联项会出现较大的N400事件相关电位以及行为语义偏差，但结果存在差异。当前实验使用词对来简化程序并减少对记忆维持的要求。此外，还比较了半球反应，因为有证据表明左半球可能选择主导意义，而右半球可能使所有可能的意义都保持活跃。受试者指出两个词（线索词、目标词）是否相关。线索词呈现1秒，可能是一个歧义性或非歧义性名词，目标词在线索词出现1.25秒后呈现，分别是主导关联项或从属关联项，或者是相关词或不相关词。N400效应是根据400 - 600毫秒期间的差异波形计算得出的。两组（23名精神分裂症患者、25名匹配的对照组）对这些词的N400效应存在显著差异（组×词，p = 0.04）。对照组呈现出分级反应，主导关联项＜从属关联项＜不相关词。精神分裂症患者对从属关联项的N400效应最大，对主导意义关联项和不相关词的活动较少。两组对不相关词均表现出右半球分布，对从属关联项则有大量左半球激活（词×半球，p＜0.001）。这些数据支持了精神分裂症中的语义偏差。它们还证明了右半球在维持宽泛的同形异义词意义层级方面的特殊作用。这种半球特化在精神分裂症中似乎是完整的。
