The Neural Mechanism Of Semantic Integration In Natural Language Understanding

For readers and listeners,an important goal of language comprehension beyond single word processing is deriving new and complex meaning from small pieces of word-level information,which is referred as semantic integration.One of the challenges for cognitive neuroscience of language is to account for the functional and neuroanatomical underpinnings of semantic integration.Insights into the functional characteristics of semantic integration have been especially gained through a series of fMRI studies.Most studies focused on the processing of combining word meanings into sentence context with semantic violation.Several brain areas were found to be activated for the manipulation,like left inferior frontal gyrus(lIFG),left superior and middle temporal gyrus(left STG/MTG)and angular gyrus(AG).While it remains unclear which of these regions account for semantic integration.Previous studies explored the neural basis of semantic integration with word or sentence materials.The discrepancy of the brain areas related with semantic integration might be due to the vary tasks and surface features of language materials.It is therefore necessary to identify brain regions that are responsible to semantic integration in a naturalistic language using situation with no explicit task demanded.To this end,we constructed an fMRI experiment to examine the neural basis of semantic integration in a natural situation.Participants read the stories in which three different scales of semantic units were inserted,including connected sentences,scrambled sentences and scrambled words.With the manipulation of integration scale,we could see if the same core semantic integration were shared across processing level or different patterns would show between levels.Data were analyzed in general linear model,with comprehension of normal stories as baseline.The results showed that brain activation changes with gradients from word level to paragraph.The left angular gyrus showed higher activation with the inserted materials closer to natural story.Similar pattern was also found in anterior temporal lobe.The two areas are consistently believed as the comprehension center in previous studies.With our results,these two regions might be related with combing processing,building high level semantic representation with lower level semantic block.In the meantime,superior parietal sulcus,precentral gyrus and inferior showed the inverse pattern,which means that these regions might be related with general cognitive processing in word level computation,like cognitive control.The functional connectivity analyzes showed similar results.In summary,the present study indicates that,with the materials being closer to natural story,the neural circuit of semantic integration relied more on the language comprehension center(angular gyrus and superior temporal sulcus).Along with the control view,these results also suggested that the domain-general mechanisms of executive control may be recruited to control conflicts arising from linguistic inputs and these control processes are mediated by a network of frontal-parietal structures.The current research supplied empirical evidences for the neurobiology model of reading,also brought inspiration to the language rehabilitation and training.