Hemispheric Contributions to Lexical Ambiguity Resolution: Evidence from Individuals with Complex Language Impairment Following Left-Hemisphere Lesions

Abstract

Nine individuals with complex language deficits following left-hemisphere cortical lesions and a matched control group (n ϭ 9) performed speeded lexical decisions on the third word of auditory word triplets containing a lexical ambiguity. The critical conditions were concordant (e.g., coin-bank-money), discordant (e.g., river-bank-money), neutral (e.g., day-bankmoney), and unrelated (e.g., river-day-money). Triplets were presented with an interstimulus interval (ISI) of 100 and 1250 ms. Overall, the left-hemisphere-damaged subjects appeared able to exhaustively access meanings for lexical ambiguities rapidly, but were unable to reduce the level of activation for contextually inappropriate meanings at both short and long ISIs, unlike control subjects. These findings are consistent with a disruption of the proposed role of the left hemisphere in selecting and suppressing meanings via contextual integration and a sparing of the right-hemisphere mechanisms responsible for maintaining alternative meanings. The study of lexical ambiguity processing in normals and individuals with unilateral lesions can provide insights into how the cerebral hemispheres make unique and possibly complementary contributions to language processing. With regard to language in general, it has been postulated that the right hemisphere coarsely codes a broad selection of semantic information, whereas the left hemisphere is involved in a finer processing of strongly related information possibly based on intentional selection and integration operations (Beeman & Chiarello, 1998). Other hemispheric differences documented in normals include the time course of semantic activation, the form of attentional/controlled processing conducted in each hemisphere, and differential sensitivity to certain forms of linguistic information (Collins, 1999;Federmeier & Kutas, 1999;Koivisto, 1999).These hemispheric processing capacities have been revealed, in part, through the study of lexical ambiguity. The structure of lexical ambiguities has provided a critical platform for investigating the functional architecture of the language processing system; specifically, speaking to the issue of whether lexical processing is modular We thank two anonymous reviewers for their helpful comments on an earlier version of this article.

The effects of context, meaning frequency, and associative strength on semantic selection: Distinct contributions from each cerebral hemisphere

“…For example, when words are embedded in sentences that are biased toward one meaning of a homonym, there is evidence to suggest that the LH is more likely to select the contextually-consistent meaning (Faust and Gernsbacher, 1996), regardless of meaning frequency (Faust and Chiarello, 1998), whereas the RH fails to select (but see also Coney and Evans, 2000). These VF studies with neurologically-intact participants thus seem to indicate that the LH controls meaning selection processes, and, in support of this conclusion, LH damage has been linked to meaning selection deficits (Copland, Chenery, and Murdoch, 2002;Swaab, Brown, and Hagoort, 1998). However, participants with unilateral RH damage have also been found to exhibit deficits in context-based meaning selection (McDonald et al, 2005;Tompkins et al, 2000), suggesting that the RH contributes essential functions as well.…”

The divided visual world paradigm: Eye tracking reveals hemispheric asymmetries in lexical ambiguity resolution

“…These studies, along with evidence suggesting that LH damage is associated with meaning selection deficits (Copland et al, 2002;Swaab et al, 1998), point to a critical role for the LH in the control of meaning selection. However, deficits in context-based meaning selection have also been observed in patients with unilateral RH damage (McDonald et al, 2005;Tompkins et al, 2000).…”

“…When sentence context information is available to constrain the possible meaning of homonyms, VF studies with neurologically-intact participants suggest that the LH is more likely to select the meaning that is consistent with context (Faust and Gernsbacher, 1996;Faust and Chiarello, 1998), whereas the RH fails to select (but see also Coney and Evans, 2000). These studies, along with evidence suggesting that LH damage is associated with meaning selection deficits (Copland et al, 2002;Swaab et al, 1998), point to a critical role for the LH in the control of meaning selection. However, deficits in context-based meaning selection have also been observed in patients with unilateral RH damage (McDonald et al, 2005;Tompkins et al, 2000).…”

Mental Lexicon Research in the New Millennium

“…One study (29) used Filipino-English bilinguals to investigate cross-linguistic effects in the processing of English phonology. The seven studies of aphasia (3,10,14,19,34,48,50) represented in the special issue uncovered a variety of new phenomena and were distinguished by their use of diverse assessment techniques. Finally, one study (39) reported on the manner in which developmental dysphasia impacts the processing of verbs.…”