Pulvermüller F, Lutzenberger W, Preissl H
Department of Psychology, Universität Konstanz, Germany.
Cereb Cortex. 1999 Jul-Aug;9(5):497-506. doi: 10.1093/cercor/9.5.497.
Lesion evidence indicates that words from different lexical categories, such as nouns and verbs, may have different cortical counterparts. In this study, processing of nouns and verbs was investigated in the intact brain using (i) behavioral measures, (ii) stimulus-triggered event-related potentials and (iii) high-frequency electrocortical responses in the gamma band. Nouns and verbs carefully matched for various variables, including word frequency, length, arousal and valence, were presented in a lexical decision task while electrocortical responses were recorded. In addition, information about cognitive processing of these stimuli was obtained using questionnaires and reaction times. As soon as approximately 200 ms after stimulus onset, event-related potentials disclosed electrocortical differences between nouns and verbs over widespread cortical areas. In a later time window, 500-800 ms after stimulus onset, there was a significant difference between high-frequency responses in the 30 Hz range. Difference maps obtained from both event-related potentials and high-frequency responses revealed strong between-category differences of signals recorded above motor and visual cortices. Behavioral data suggest that these different physiological responses are related to semantic associations (motor or visual) elicited by these word groups. Our results are consistent with a neurobiological model of language representation postulating cell assemblies with distinct cortical topographies as biological counterparts of words. Assemblies representing nouns referring to visually perceived objects may include neurons in visual cortices, and assemblies representing action verbs may include additional neurons in motor, premotor and prefrontal cortices. Event-related potentials and high-frequency responses are proposed to indicate two different functional states of cell assemblies: initial full activation ('ignition') and continuous reverberatory activity.
损伤证据表明，来自不同词汇类别的单词，如名词和动词，可能有不同的皮质对应物。在本研究中，我们使用（i）行为测量、（ii）刺激触发的事件相关电位和（iii）伽马波段的高频皮质电反应，在完整大脑中研究了名词和动词的加工过程。在词汇判断任务中呈现经过各种变量（包括词频、长度、唤醒度和效价）仔细匹配的名词和动词，同时记录皮质电反应。此外，通过问卷和反应时间获得了有关这些刺激认知加工的信息。刺激开始后约200毫秒，事件相关电位就揭示了名词和动词在广泛皮质区域的皮质电差异。在稍后的时间窗口，即刺激开始后500 - 800毫秒，30赫兹范围内的高频反应存在显著差异。从事件相关电位和高频反应获得的差异图显示，在运动和视觉皮质上方记录的信号在类别之间存在强烈差异。行为数据表明，这些不同的生理反应与这些单词组引发的语义联想（运动或视觉）有关。我们的结果与语言表征的神经生物学模型一致，该模型假设具有不同皮质拓扑结构的细胞集合作为单词的生物学对应物。代表视觉感知对象的名词的集合可能包括视觉皮质中的神经元，而代表动作动词的集合可能包括运动、运动前区和前额叶皮质中的额外神经元。事件相关电位和高频反应被认为表明细胞集合的两种不同功能状态：初始完全激活（“点火”）和持续的回响活动。
