Neural Mechanisms Of Morpheme Integration In Chinese Two-character Word Reading

Polymorphemic word processing requires integrating semantic and syntactic information between the morphemes,and the neural mechanism of polymorphemic word reading is a hot and focused issue in cognitive neuroscience of language.However,the neural mechanism of semantic and syntactic integration in Chinese two-morpheme word reading is still not clear.Especially whether the integration processing of these two kinds of linguistic information depends on general integration processing or relatively separate neural basis is still an open question.In order to explore the neural mechanism of semantic and syntactic integration in reading Chinese words,two factors,including semantic relatedness and syntactic structure between the two morphemes in Chinese two-morpheme words,were manipulated in this study and a 2(semantic relatedness:related,unrelated)×2(syntactic structure:noun-noun,adjective-noun)repeated measurement experiment design was adopted.During the experiments,participants were asked to do lexical decision task.Both cognitive behavioral data(experiment 1)and the functional Near-Infrared Spectroscopy(fNIRS)data(experiment 2)were collected in this study.In the first experiment,behavioral results showed significant semantic relatedness main effect,reading semantic related words is faster than reading semantic unrelated words and the accuracy is also higher;the data also showed significant syntactic structure main effect,reading adjective-noun combinations is faster and the accuracy is higher than reading noun-noun combinations;besides,there is a significant interaction effect between semantic relatedness and syntactic structure.And the further analysis showed that there is a significant syntactic structure simple effect for reading semantic related words,while the semantic relatedness simple effects are significant for reading both syntactic structures of words.The behavioral results indicate that there might be a dissociated processing mechanism between semantic and syntactic integration in Chinese two-morpheme word reading.So the second experiment used slow event-related functional near-infrared spectroscopy(fNIRS)to find out the neural mechanism of semantic and syntactic integration processing in Chinese two-morpheme word reading.The results of the fNIRS study showed differential cortical participation for semantic and syntactic integration processing.Semantic relatedness main effect occurred in left superior temporal gyrus(STG),reading semantic related words showed larger change of oxyhaemoglobin concentration than semantic unrelated words.Syntactic structure main effect occurred in left inferior frontal gyrus(IFG),reading adjective-noun combinations showed significant larger change of oxyhaemoglobin concentration than noun-noun combinations.Moreover,the interaction effect between the two factors was found in left supramarginal gyrus(SMG),and the further simple effect analysis found that reading adjective-noun combinations,SMG showed semantic relatedness simple effect,that is to say,reading semantic related words showed larger change of oxyhaemoglobin concentration than semantic unrelated words;when reading noun-noun combinations,there is no semantic relatedness simple effect.Both behavioral and fNIRS results reveal that Chinese two-morpheme word reading may involve dissociated semantic and syntactic integration processing:left STG may be responsible for semantic integration and left IFG for syntactic integration,while the integration processing of these two kinds of information may need the contribution of left SMG.The results of this study provide direct evidence for the disentanglement of the relatively separate neural basis for semantic and syntactic integration processing in language comprehension.