Phonological Ambiguity Modulates Resolution of Semantic Ambiguity During Reading: An fMRI Study of Hebrew
Objectives: The current fMRI study examined the role of phonology in the extraction of meaning from print in each hemisphere by comparing homophonic and heterophonic homographs (ambiguous words in which both meanings have the same or different sounds respectively, e.g. bank or tear) The analysis distinguished between the first phase, in which participants read ambiguous words without context, and the second phase in which the context resolves the ambiguity. Method: Native Hebrew readers were scanned during semantic relatedness judgments on pairs of words in which the first word was either a homophone or a heterophone and the second word was related to its dominant or subordinate meaning. Results: In Phase 1 there was greater activation for heterophones in left inferior frontal gyrus (IFG) pars opercularis, and more activation for homophones in bilateral IFG pars orbitalis, suggesting that resolution of the conflict at the phonological level has abolished the semantic ambiguity for heterophones. Reduced activation for all ambiguous words in temporo parietal regions suggests that although ambiguity enhances controlled lexical selection processes in frontal regions it reduces reliance on bottom up mapping processes. After presentation of the context, a larger difference between the dominant and subordinate meaning was found for heterophones in all reading related regions, suggesting a greater engagement for heterophones with the dominant meaning. Conclusions: Altogether these results are consistent with the prominent role of phonological processing in visual word recognition. Finally, despite differences in hemispheric asymmetry between homophones and heterophones, ambiguity resolution, even toward the subordinate meaning, is largely left lateralized.
Neuropsychology