Lexical ambiguity in sentence comprehension

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 involve 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. IntroductionOne 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 particularly interesting at a choice point in understanding, as is the case with lexically ambiguous words. When a word has multiple meanings, one meaning must be selected while somehow retaining the possibility of using the alternative meaning. Additionally, 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 and Duffy, 1986;MacDonald et al., 1994) leading to situations in which the likelihood of maintaining multiple meanings could be dependent on their relative frequencies. In some cases, the ultimately incorrect interpretation may initially be selected, leading to a semantically incoherent sentence representation and hence to a re-analysis of the meaning and a suppression of the misfitting interpreta-

Pathways to lexical ambiguity: fMRI evidence for bilateral fronto-parietal involvement in language processing

“…More recently, Bilenko et al (2008), showed that increased processing resources recruit areas in the inferior frontal gyrus bilaterally under conditions of competition, even when the experimental task does not impose overt selection (see also Mason andJust, 2007 andRodd et al, 2005). The present study not only provides further support to these findings, but succeeds in further delineating the specific area within the IFG that is involved in such processing.…”

“…Several neuroimaging studies (Kan & Thompson-Schill, 2004;Petrides et al, 1995;Thompson-Schill et al, 2002;Thompson-Schill, D'Esposito, & Kan, 1999 Mason andJust, 2007 andRodd et al, 2005 for similar findings in the presence of sentential context).…”

“…Several neuroimaging experiments have investigated the neural systems underlying the processing of ambiguous words (Chan, Liu, Yip, Fox, Gao, & Tan, 2004;Copland, de Zubicaray, McMahon, & Eastburn, 2007;Mason & Just, 2007;Rodd, Davis, & Johnsrude, 2005;Zempleni, Renken, Hoeks, Hoogduin, & Stowe, 2007), and although some studies have shown increased activation in the RH during the processing of lexical ambiguity (e.g., Bilenko et al, 2008;Chan et al, 2004;Mason & Just, 2007;Rodd et al, 2005;Zempleni et al, 2007), others have not (e.g., Bedny et al, 2008;Chen et al, 2008;Grindrod et al, 2008;Hoenig & Scheef, 2009;Ihara et al, 2007;Rapp et al, 2004;Rapp et al, 2007;Lee & Dapretto, 2006), leading to unanswered questions regarding the role of the RH in the processing of lexical ambiguity.…”

Behavioral and fMRI evidence that cognitive ability modulates the effect of semantic context on speech intelligibility

“…Neuroimaging studies have examined the relation between cognitive abilities (e.g., Just, Carpenter, & Miyake, 2003), speech perception and brain activity (e.g., Mason & Just, 2007;Osaka et al, 2003). These studies indicate that RSpan can explain individual differences in the efficiency of processes (attentional or lexical) relevant for understanding degraded speech.…”

The anterior left inferior frontal gyrus contributes to semantic unification

“…In the violation detection task (Ni et al, 2000), semantic processing may terminate earlier in the incongruent condition than in the congruent condition due to a specific reading strategy (Huang et al, 2012;Zhu et al, 2009). Although activation in the LIFG has been reported in a wide range of tasks, including semantic congruency judgment (Constable et al, 2004;Rueschemeyer et al, 2006;Zhu et al, 2009), meaningfulness rating (Humphries et al, 2007), reading for comprehension (Hagoort et al, 2004;Tesink et al, 2009), comprehension probe test (Just et al, 1996;Mason and Just, 2007;Newman et al, 2009;Ye and Zhou, 2009), priming (Devauchelle et al, 2009), and violation detection (Ni et al, 2000), it has been suggested that these tasks all involve explicit attentional control (Crinion et al, 2003;Van Petten and Luka, 2006). It is possible that such control processes may interact with semantic unification and constitute an alternative explanation for the LIFG activations observed in these studies.…”