Swaab T Y, Brown C, Hagoort P
Center for Neuroscience, University of California, Davis 95616, USA.
Neuropsychologia. 1998 Aug;36(8):737-61. doi: 10.1016/s0028-3932(97)00174-7.
This study investigates whether spoken sentence comprehension deficits in Broca's aphasics results from their inability to access the subordinate meaning of ambiguous words (e.g. bank), or alternatively, from a delay in their selection of the contextually appropriate meaning. Twelve Broca's aphasics and twelve elderly controls were presented with lexical ambiguities in three context conditions, each followed by the same target words. In the concordant condition, the sentence context biased the meaning of the sentence-final ambiguous word that was related to the target. In the discordant condition, the sentence context biased the meaning of the sentence-final ambiguous word that was incompatible with the target. In the unrelated condition, the sentence-final word was unambiguous and unrelated to the target. The task of the subjects was to listen attentively to the stimuli. The activational status of the ambiguous sentence-final words was inferred from the amplitude of the N400 to the targets at two inter-stimulus intervals (ISIs) (100 ms and 1250 ms). At the short ISI, the Broca's aphasics showed clear evidence of activation of the subordinate meaning. In contrast to elderly controls, however, the Broca's aphasics were not successful at selecting the appropriate meaning of the ambiguity in the short ISI version of the experiment. But at the long ISI, in accordance with the performance of the elderly controls, the patients were able to successfully complete the contextual selection process. These results indicate that Broca's aphasics are delayed in the process of contextual selection. It is argued that this finding of delayed selection is compatible with the idea that comprehension deficits in Broca's aphasia result from a delay in the process of integrating lexical information.
本研究调查了布罗卡失语症患者的口语句子理解缺陷是源于他们无法理解歧义单词（如“bank”）的次要含义，还是源于他们在选择上下文合适含义时的延迟。研究人员向12名布罗卡失语症患者和12名老年对照组人员呈现了三种语境条件下的词汇歧义，每种条件后都跟着相同的目标单词。在一致条件下，句子语境使句末歧义单词的含义偏向于与目标相关的含义。在不一致条件下，句子语境使句末歧义单词的含义偏向于与目标不兼容的含义。在无关条件下，句末单词是明确的且与目标无关。受试者的任务是仔细聆听刺激。通过在两个刺激间隔（ISI）（100毫秒和1250毫秒）时对目标的N400波幅来推断歧义句末单词的激活状态。在短ISI时，布罗卡失语症患者表现出明显激活次要含义的证据。然而，与老年对照组相比，布罗卡失语症患者在实验的短ISI版本中未能成功选择歧义的合适含义。但在长ISI时，与老年对照组的表现一致，患者能够成功完成上下文选择过程。这些结果表明布罗卡失语症患者在上下文选择过程中存在延迟。有人认为，这种延迟选择的发现与布罗卡失语症的理解缺陷源于词汇信息整合过程延迟的观点相符。
