The Time-course Of Verbal Metaphor Comprehension

The verbal metaphor is a sentence in which the verb is metaphorically used,that is to say,the concept of a specific verb is used to understand the abstract concept.For example,"love barrier is difficult to cross",we use the specific "cross" concept of action to express the abstract "spend" concept.There are lots of studies about nominal metaphor comprehension before.Nominal metaphor is as an indicator of entity but verbal metaphor is an indicator of event,so verbal metaphor is different from nominal metaphor in essence.It is necessary to do research about the time-course of verbal metaphor comprehension.Therefore,the purpose of this study is to explore the time course of semantic processing in verbal metaphor comprehension based on ERP technology with high temporal resolution.Recently,a large number of studies showed that there exist the activation of the sensorimotor system in semantic process of verbal metaphor.but the time-course of activation of the sensorimotor system did not draw a unified conclusion.This study aims to investigate the time course of activation of the sensorimotor system in semantic processing of metaphor.According to the Career of Metaphor model,the familiarity of metaphor influences the comprehension of metaphor,so this study also aims to do research on the difference of semantic processing and the activation of sensorimotor system between familiar metaphor and novel metaphor.This study used the last word paradigm which is presented word by word with ERPs recorded,employing sensicality judgement task,constructing four types of sentences such as literal verbal sentence,familiar verbal metaphor sentence,novel verbal metaphor sentence and meaningless sentences to do research about the time-course of semantic comprehension and the activation of sensorimotor system and how they are affected by familiarity of verbal metaphor.In the traditional metaphor study,three kinds of electroencephalogram components(P200,N400 and LPC)were used to represent the different stages of semantic processing in metaphorical understanding.EEG mu(about 10Hz)and β(about 20Hz)rhythms recorded at fronto-central electrodes were generally considered as markers of motor corticalactivity in humans.So this study intended to use these EEG indicators as a symbol of semantic processing and the activation of sensorimotor system.As a result,in the process of semantic activation,compared with literal and meaningless sentences,both familiar and unfamiliar metaphor sentences causeed the smaller P200 component;Compared with the literal sentence,familiar metaphor sentences caused the N400 component which exists the 270-350 ms time window.The novel metaphor sentences and the meaningless sentences caused a wider N400 component which existed 270-500 ms time window;Compared to literal and meaningless sentences,novel and familiar metaphor sentences activated larger LPC components.In the time-course of activation of sensorimotor system,compared to the baseline before the verb appeared,both familiar and novel metaphor cause mu(10-12Hz)and beta(16-20Hz)significantly desynchronization in 200-600 ms time window which belongs to verb conceptual representation stage.EEG source localization results showed that the novel metaphor caused the Paracentral Lobule greater activation than the familiar metaphor;Both familiar and novel metaphor caused mu(10-12Hz)significantly desynchronization in 600-1200 ms time window which belonged to the formation stage of mental imagery of the sentences;In the whole 200-1200 ms time window,EEG source localization results showed that compared with familiar metaphor,novel metaphor cause the Precentral Gyrus greater activation.As is suggested by the above results:(1)The time-course of semantic activation of verbal metaphor comprehension includes three stages: about 200 ms after the verb appears,the paticipants makes a preliminary semantic analysis;about 400 ms,the literal meaning of the metaphor keywords is firstly activated,and within a very short time,metaphorical meanings of keywords is secondly activated,and the paticipants select the metaphorical meaning of keywords successfully;In the 600 ms time window,because of the conflict between the literal meaning of sentence,metaphorical meaning of keywords and the metaphorical context,so the paticipants makes reanalysis,mapping the metaphorical meaning of the keywords to the metaphorical context andfinally understand the metaphor sentences.(2)In the processing of verbal metaphor sentences,the activation of the sensorimotor system begins from 200 ms and continues to 1200 ms after the verb appears.That is to say,in the process of verbal metaphor,the sensorimotor system is not only activated in the initial stage of semantic analysis,but also plays a role in the two stages of conceptual representation and sentence mental imagery formation.(3)In the process of verbal metaphor sentences,the semantic processing and the activation of the sensorimotor system are regulated by the familiarity of metaphor.The semantic process of familiar metaphor is between the indirect access model and the graded salience model;However,the process of novel metaphor sentences supports the graded salience model model,that is to say,the literal meaning of metaphor keywords is firstly activated,and the meaning of metaphorical keywords is activated secondly,and the literal meaning is not suppressed before the activation of metaphorical meaning.In the process of semantic comprehension,either in the stage of conceptual representation or in the stage of movement imagery formation,novel metaphors cause larger activation of sensorimotor system than familiar metaphors.This result supports weaker embodied cognition theory,and also supports the neural career model of metaphor comprehension.