Suppressing contextually irrelevant meanings of homophonic versus heterophonic homographs: A tDCS study targeting LIFG.

Readers frequently encounter homographs (e.g., bank) whose resolution requires selection-suppression processes: selecting the contextually relevant meaning, while suppressing the irrelevant one. In two experiments, we investigated how these processes are modulated by the phonological status of the homograph (homographs with one vs. two possible pronunciations); and what is the involvement of the left inferior frontal gyrus (LIFG, including Broca's area) in these processes. To these ends, Experiment 1 utilized the context verification task with two types of Hebrew homographs: homophonic (e.g., bank) and heterophonic (e.g., tear). In the task, participants read sentences ending either with a homograph (e.g., bank) or an unambiguous word (e.g., shore). The sentences were biased towards the homograph's subordinate meaning (e.g., The fisherman sat on the bank/shore), and were followed by a target word related to the homograph's dominant meaning (e.g., MONEY). The participants were asked to judge whether the target was related to the overall meaning of the sentence. An ambiguity effect was observed for both types of homographs, reflecting interference from the irrelevant dominant meaning. However, this ambiguity effect was larger for heterophonic than for homophonic homographs, indicating that dominant meanings of heterophonic homographs are more difficult to suppress. Experiment 2 was identical, except that the procedure was coupled with transcranial direct current stimulation (tDCS) over the LIFG (including Broca's area). We found that stimulating the LIFG abolished the ambiguity effect, but only in the case of heterophonic homographs. Together, these findings highlight the distinction between phonological and semantic levels of selection-suppression processes, and the involvement of the LIFG in the phonological level of these processes.

Inter- and intra- hemispheric interactions in reading ambiguous words.

The present study investigated how the brain processes words with multiple meanings. Specifically, we examined the inter- and intra-hemispheric connectivity of unambiguous words compared to two types of ambiguous words: homophonic homographs, which have multiple meanings mapped to a single phonological representation and orthography, and heterophonic homographs, which have multiple meanings mapped to different phonological representations but the same orthography. Using a semantic relatedness judgment task and effective connectivity analysis via Dynamic Causal Modeling (DCM) on previously published fMRI data (Bitan et al., 2017), we found that the two hemispheres compete in orthographic processing during the reading of unambiguous words. For heterophonic homographs, we observed increased connectivity within the left hemisphere, highlighting the importance of top-down re-activation of orthographic representations by phonological ones for considering alternative meanings. For homophonic homographs, we found a flow of information from the left to the right hemisphere and from the right to the left, indicating that the brain retrieves different meanings using different pathways. These findings provide novel insights into the complex mechanisms involved in language processing and shed light on the different communication patterns within and between hemispheres during the processing of ambiguous and unambiguous words.

Interactions of lexical and conceptual representations: Evidence from EEG.

We examined whether meanings automatically activate linguistic forms, and whether these forms affect semantic decisions. Participants were presented sequentially with pairs of pictures and decided whether the objects in the pictures were related. At no point did they name the pictures. The object names of the experimental stimuli were ambiguous either in orthography (homographs), phonology (homophones), or both (homonyms), or unambiguous. We show that the lexical characteristics of the name of the objects affect a semantic decision about real world relations, in an online measure (N400), in addition to offline behavioral measures. We show a dissociation between conceptual and lexical recognition, where an earlier component (N230), was affected by relatedness, but was not sensitive to the lexical characteristics. We interpret this as supporting the hypothesis that semantic recognition occurs before the automatic lexical activation of the object name, but that once linguistic representations are activated, they affect semantic integration.

Visual simulations in the two cerebral hemispheres: A bilingual perspective.

The ability of each hemisphere to construct visual simulations during first language (L1) and second language (L2) sentence reading was investigated. Late bilinguals read L1 and L2 sentences and decided after each sentence whether a pictured object was mentioned in the sentence. Target pictures were presented laterally in the left/right visual field (LVF/RVF) to the right/left hemisphere (RH/LH), respectively. 'Yes' responses were faster when the pictured object's shape matched, rather than mismatched, the sentence-implied shape, irrespective of the language involved. Critically, this visual shape effect was significant only under LVF/RH presentation, indicating that visual simulations are more likely to occur in the RH than in the LH. The fact that a similar experiment with central picture presentation has produced a significant shape effect only in the L1 (Norman & Peleg, 2022), suggests that under normal (central) reading conditions, the RH may be less involved in L2 than in L1 reading.

Phonology and orthography in deaf readers: Evidence from a lateralized ambiguity resolution paradigm.

This study explored differences between the two hemispheres in processing written words among deaf readers. The main hypothesis was that impoverished phonological abilities of deaf readers may lead to atypical patterns of hemispheric involvement. To test this, deaf participants completed a metalinguistic awareness test to evaluate their orthographic and phonological awareness. Additionally, they were asked to read biased or neutral target sentences ending with an ambiguous homograph, with each sentence followed by the request to make a rapid lexical decision on a target word presented either to the left (LH) or right hemisphere (RH). Targets were either related to the more frequent, dominant, meaning of the homograph, to the less frequent, subordinate, meaning of the homograph or were not related at all. An Inverse Efficiency Score based on both response latency and accuracy was calculated and revealed that deaf readers' RH perform better than their LH. In contrast to hearing readers who in previous studies manifested left hemisphere dominance when completed the same research design. The apparent divergence of deaf readers' hemisphere lateralization from that of hearing counterparts seems to validate previous findings suggesting greater reliance on RH involvement among deaf individuals during visual word recognition.

Orthographic, Phonological, and Semantic Dynamics During Visual Word Recognition in Deaf Versus Hearing Adults.

Purpose Studies on reading in individuals with severe-to-profound hearing loss (deaf) raise the possibility that, due to deficient phonological coding, deaf individuals may rely more on orthographic-semantic links than on orthographic-phonological links. However, the relative contribution of phonological and semantic information to visual word recognition in deaf individuals was not directly assessed in these studies. The aim of the present study, therefore, was to examine the interplay between orthographic, phonological, and semantic representations during visual word recognition, in deaf versus hearing adults. Method Deaf and hearing participants were asked to perform a visual lexical decision task in Hebrew. The critical stimuli consisted of three types of Hebrew words, which differ in terms of their relationship between orthography, phonology, and semantics: unambiguous words, homonyms, and homographs. Results In the hearing group, phonological effects were more pronounced than semantic effects: Homographs (multiple pronunciations) were recognized significantly slower than homonyms or unambiguous words (one pronunciation). However, there was no significant difference between homonyms (multiple meanings) and unambiguous words (one meaning). In contrast, in the deaf group, there was no significant difference among the three word types, indicating that visual word recognition, in these participants, is driven primarily by orthography. Conclusion While visual word recognition in hearing readers is accomplished mainly via orthographic-phonological connections, deaf readers rely mainly on orthographic-semantic connections.

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. (PsycINFO Database Record

Controlled semantic processes within and between the two cerebral hemispheres.

To test the separate and combined abilities of the two cerebral hemispheres to perform controlled semantic selection and integration processes, Hebrew readers saw pairs of words and had to decide whether the two words were semantically related. The first word in each pair was presented centrally. The second word was presented in the left, right, or central visual field (LVF, RVF, and CVF). We compared response latencies for related pairs in two conditions: In the ambiguous condition, the first word was a homograph (either homophonic or heterophonic) and the second word was related to either its dominant or subordinate meaning. In the unambiguous condition, homographs were replaced with unambiguous control words. Irrespective of VF or homograph type, response times for ambiguous pairs were significantly longer than for unambiguous pairs only when targets were related to the subordinate meaning of the homograph. In the left hemisphere (RVF/LH), this ambiguity effect was larger for heterophones than for homophones, whereas in the right hemisphere (LVF/RH), similar patterns were observed for both types of homographs. Finally, performance patterns in the CVF revealed the same patterns as those in the RVF/LH, and were different from those in the LVF/RH. The implications of these results are discussed.

Lexical factors in conceptual processes: The relationship between semantic representations and their corresponding phonological and orthographic lexical forms.

To examine phonological and orthographic effects on semantic processing, the present study utilized a semantic task with nonverbal stimuli. In Experiment 1, Hebrew speakers were asked to decide whether 2 pictorial targets are semantically related or not. In Experiment 2, Hebrew speakers and non-Hebrew speakers were asked to rate the semantic relatedness of the same targets on a 5-point scale. Experiment 3 was identical to the first experiment except that the 2 pictures were presented simultaneously rather than sequentially. In all experiments, we compared responses to semantically unrelated pairs in 2 conditions: In the ambiguous condition, each pair represented 2 distinct meanings of an ambiguous Hebrew word. In the unambiguous condition, the first picture was replaced with an unambiguous control. To disentangle phonological and orthographic effects, three types of Hebrew ambiguous words were used: homonyms, homophones, and homographs. Ambiguous pairs were more difficult to be judged as semantically unrelated in comparison to their unambiguous controls. Moreover, while non-Hebrew speakers did not distinguish between the 2 lexical conditions, Hebrew speakers rated ambiguous pairs as significantly more related than their unambiguous controls. Importantly, in general, the ambiguity effect was stronger for homonyms, where both lexical forms are shared, than for either homophones or homographs, which are only phonologically or orthographically related. Thus, consistent with interactive "triangle" models, the results suggest that (a) conceptual-semantic representations automatically activate both their corresponding phonological and orthographic lexical forms, and (b) these lexical forms, once activated, may in turn affect semantic-conceptual processes via feedback connections.

Hemispheric asymmetries in meaning selection: evidence from the disambiguation of homophonic vs. heterophonic homographs.

Research investigating hemispheric asymmetries in meaning selection using homophonic homographs (e.g., bank), suggests that the left hemisphere (LH) quickly selects contextually relevant meanings, whereas the right hemisphere (RH) maintains a broader spectrum of meanings including those that are contextually irrelevant (e.g., Faust & Chiarello, 1998). The present study investigated cerebral asymmetries in maintaining the multiple meanings of two types of Hebrew homographs: homophonic homographs and heterophonic homographs (e.g., tear). Participants read homographs preceded by a biasing, or a non-biasing sentential context, and performed a lexical decision task on targets presented laterally, 1000ms after the onset of the sentence-final ambiguous prime. Targets were related to either the dominant or the subordinate meaning of the preceding homograph, or unrelated to it. When targets were presented in the LVF/RH, dominant and subordinate meanings, of both types of homographs, were retained only when they were supported by context. In a non-biasing context, only dominant meanings of homophonic homographs were retained. Alternatively, when targets were presented in the RVF/LH, priming effects for homophonic homographs were only evident when meanings were supported by both context and frequency (i.e., when context favored the dominant meaning). In contrast, heterophonic homographs resulted in activation of dominant meanings, in all contexts, and activation of subordinate meanings, only in subordinate-biasing contexts. The results challenge the view that a broader spectrum of meanings is maintained in the right than in the left hemisphere and suggest that hemispheric differences in the time course of meaning selection (or decay) may be modulated by phonology.

Semantic asymmetries are modulated by phonological asymmetries: evidence from the disambiguation of homophonic versus heterophonic homographs.

The present study investigated cerebral asymmetries in accessing multiple meanings of two types of homographs: homophonic homographs (e.g., bank) and heterophonic homographs (e.g., tear). Participants read homographs preceded by either a biasing or a non-biasing sentential context and performed a lexical decision on lateralized targets presented 150 ms after onset of the sentence-final ambiguous prime. Targets were either related to the dominant or the subordinate meaning of the preceding homograph or were unrelated to it. In the case of homophonic homographs--our results converge with previous findings: both activation and selection processes are faster in the LH than in the RH. Importantly, however, in the case of heterophonic homographs--opposite asymmetries were found. These results suggest that semantic asymmetries are modulated by phonology. They are discussed in the context of a model of functional architecture of reading in the two hemispheres in which orthography, phonology and semantics are fully interconnected in the LH, whereas in the RH, orthography and phonology are not directly connected, such that phonological processes are mediated by semantics.

Hemispheric sensitivities to lexical and contextual information: evidence from lexical ambiguity resolution.

The present study examined the manner in which both hemispheres utilize prior semantic context and relative meaning frequency during the processing of homographs. Participants read sentences biased toward the dominant or the subordinate meaning of their final homograph, or unbiased neutral sentences, and performed a lexical decision task on lateralized targets presented 250ms after the onset of the sentence-final ambiguous prime. Targets were either related to the dominant or the subordinate meaning of the preceding homograph, or unrelated to it. Performance asymmetry was found in the absence of a biasing context: dominant-related targets were exclusively facilitated in the RVF/LH, whereas both dominant- and subordinate-related targets were facilitated in the LVF/RH. Performance symmetry was found in the presence of a biasing context: dominant-related targets were exclusively activated in dominant-biasing contexts, whereas both dominant- and subordinate-related targets were facilitated in subordinate-biasing contexts. The implications of the results for both general and hemispheric models of word processing are discussed.