Abstract
An event-related fMRI paradigm was used to investigate brain activity during the reading of sentences containing either a lexically ambiguous word or an unambiguous control word. Higher levels of activation occurred during the reading of sentences containing a lexical ambiguity. Furthermore, the activated cortical network differed, depending on: (1) whether the sentence contained a balanced (i.e., both meanings equally likely) or a biased (i.e., one meaning more likely than other meanings) ambiguous word; and, (2) the working memory capacity of the individual as assessed by reading span. The findings suggest that encountering a lexical ambiguity is dealt with by activating multiple meanings utilizing processes involving both hemispheres. When an early interpretation of a biased ambiguous word is later disambiguated to the subordinate meaning, the superior frontal cortex activates in response to the coherence break and the right inferior frontal gyrus and the insula activate, possibly to suppress the incorrect interpretation. Negative correlations between reading span scores and activation in the right hemisphere for both types of ambiguous words suggest that readers with lower spans are more likely to show right hemisphere involvement in the processing of the ambiguity. A positive correlation between reading span scores and insula activation appearing only for biased sentences disambiguated to the subordinate meaning indicates that individuals with higher spans were more likely to initially maintain both meanings and as a result had to suppress the unintended dominant meaning.
Highlights
One of the building blocks of language comprehension is the ability to access the meaning of words as they are encountered, and to develop an interpretation that is consistent with the context
By examining how the cortical networks change in the processing of different types of ambiguity, it should be possible to fractionate some of the component processes of ambiguity resolution and relate them to individual differences in working memory capacity
For the majority of the balanced ambiguous words, one would expect that when the ambiguous word is first encountered, multiple meanings are accessed maintained to some degree during the reading of the remainder of the sentence
Summary
One of the building blocks of language comprehension is the ability to access the meaning of words as they are encountered, and to develop an interpretation that is consistent with the context This process becomes interesting at a choice point in understanding, as is the case with lexically ambiguous words. The working memory capacity of individual readers affects their ability to maintain various representations in the process of understanding a sentence (Miyake et al, 1994) Further complicating this phenomenon, ambiguous words vary in the strength or frequency of their alternative meanings (e.g., Swinney, 1979; Rayner & Duffy, 1986; MacDonald et al, 1994) leading to situations in which the likelihood of maintaining multiple. By examining how the cortical networks change in the processing of different types of ambiguity, it should be possible to fractionate some of the component processes of ambiguity resolution and relate them to individual differences in working memory capacity
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