Publications

Agrammatism in aphasia is not a homogeneous syndrome, but a characterization of a nonuniform set of language behaviors in which grammatical markers and complex syntactic structures are omitted, simplified, or misinterpreted. In a sample of 71 left-hemisphere stroke survivors, syntactic processing was quantifiedwith theNorthwestern Assessment of Verbs and Sentences (NAVS). Classification analyses were used to assess the relation between NAVS performance and morphosyntactically reduced speech in picture descriptions. Voxel-based and connectivity-based lesion-symptom mapping were applied to investigate neural correlates of impaired syntactic processing. Despite a nonrandom correspondence between NAVS performance and morphosyntactic production deficits, there was variation in individual patterns of syntactic processing. Morphosyntactically reduced production was predicted by lesions to left-hemisphere inferior frontal cortex. Impaired verb argument structure production was predicted by damage to left-hemisphere posterior superior temporal and angular gyrus, as well as to a ventral pathway between temporal and frontal cortex. Damage to this pathway was also predictive of impaired sentence comprehension and production, particularly of noncanonical sentences. Although agrammatic speech production is primarily predicted by lesions to inferior frontal cortex, other aspects of syntactic processing rely rather on regional integrity in temporoparietal cortex and the ventral stream.

The Aphasia Rapid Test is a bedside test allowing to rate aphasia severity in the acute stroke period. This test is developed as a 26-point scale estimating the severity of both speech comprehension and production in less than 5 min. Previously, ART was used in English and French clinical practice. In Russian, there has been no analogous bedside screening scale for acute hospital units. Tests which were used before are detailed but time-consuming and effortful for individuals in the first days poststroke. ART is a reliable measure allowing to identify language and speech disorders (aphasia, dysarthria, or apraxia).

According to G. K. Zipf’s observation, there is a strong correlation between word frequency and polysemy. Yet word sense frequency distribution is a neglected area in computational linguistics. Furthermore, the study of sense frequency has theoretical interest and practical applications for lexicography and word sense disambiguation. Although WordNet and SemCor contain some information about sense frequency in English, it is not enough for either practical or research purposes. This information is even lacking in Russian. To fill this lacuna, we developed and tested an automated system based on semantic vectors, which deals with the problem of sense frequency for Russian nouns. The model is first trained unsupervised on large corpora and then supplied with contexts and collocations from the Active Dictionary of Russian. The dictionary examples are used either for supervised post-training or for automatic labeling of clusters that are learned unsupervised. This allows us to reach a frequency estimation error of 11-15 percent on different corpora without additional labeled data. Word sense frequency distributions for 440 nouns are available online.

 

 

Language processing has been suggested to be partially automatic, with some studies suggesting full automaticity and attention independence of at least early neural stages of language comprehension, in particular, lexical access. Existing neurophysiological evidence has demonstrated early lexically specific brain responses (enhanced activation for real words) to orthographic stimuli presented parafoveally even under the condition of withdrawn attention. These studies, however, did not control participants’ eye movements leaving a possibility that they may have foveated the stimuli, leading to overt processing. To address this caveat, we recorded eye movements to words, pseudowords, and non-words presented parafoveally for a short duration while participants performed a dual non-linguistic feature detection task (color combination) foveally, in the focus of their visual attention. Our results revealed very few saccades to the orthographic stimuli or even to their previous locations. However, analysis of post-experimental recall and recognition performance showed above-chance memory performance for the linguistic stimuli. These results suggest that partial lexical access may indeed take place in the presence of an unrelated demanding task and in the absence of overt attention to the linguistic stimuli. As such, our data further inform automatic and largely attention-independent theories of lexical access.

We investigated effects of crosslinguistic phonological and semantic similarity on the bilingual lexicon of late unbalanced bilinguals. Our masked priming paradigm used L1 (Russian) words as masked primes and L2 (English)  words as targets. The primes and the targets either overlapped – phonologically, semantically, both phonologically and semantically – or did not overlap. Participants maintained the targets in memory and matched them against occasionally presented catch stimuli. N170 and N400 components of the word-elicited high-density ERPs were identified and analysed in signal and source space. Crosslinguistic semantic similarity shortened the reaction times. The semantics-related N400 amplitude difference correlated with individual L2 proficiency, while phonological similarity suppressed the N400 amplitude in the semantically unrelated condition. ERP source analysis suggests that these ERP dynamics are underpinned by cortical generators in the left IFG and the temporal pole. We conclude that the semantic and phonological interplay between L1 and L2 suggest an integrated bilingual lexicon.

An auditory lexical decision task tests morphological decomposition and sensitivity to violations in inflection in late second language learners, early learners (heritage speakers), and native speakers of Russian. Two datasets compared reaction times and error rates to real Russian inflected nouns and nonce nouns. Two parameters of real nouns were manipulated: case (the nominative, or the oblique case), and inflection (overt or zero). Nonce nouns had (a) real stems and inflections combined in an illegal way (lemoning), and (b) inflected nonce stems (lemosing). Results suggest that heritage and late learners process inflectional morphology; however, their processing of inflected words is unreliable: they are willing to accept words with incongruent inflections. While no major differences were found in the processing patterns of early and late learners, a developmental trajectory was observed in both groups of learners: their sensitivity to violations in inflection improved with proficiency.

Background: There is growing evidence that verbs are often more difficult to process than nouns and that verb retrieval is more commonly affected in aphasia. However, existing observations are largely based on naming and semantic judgment tasks. The extent to which this processing difficulty is modality-general has yet to be established. In addition, most of the present language batteries do not allow direct comparison between noun and verb comprehension deficits. To fill this gap, a test was developed for the assessment of noun and verb lexical-semantic comprehension.

Aims: The current study investigates whether verb processing difficulties are modality-general by administering novel balanced noun and verb comprehension tasks to participants with and without aphasia.

Method: In this study we directly compare the difficulty of comprehension of verbs versus nouns in a group of participants with aphasia (PWA, n = 32) and non-brain-damaged, age-matched participants (NBD, n = 20). The word comprehension task was implemented on a tablet measuring accuracy and reaction times (RTs). Participants were required to listen to an aurally presented word and match it to one of four pictures (a target and three distractors: semantic, phonological and irrelevant) by tapping on it with the non-dominant hand. In total, 30 nouns and 30 verbs were presented.  The verbal stimuli in the two tasks were matched on relevant psychometric properties such as familiarity, age of acquisition, subjective visual complexity, imageability, image agreement and frequency.

Results: Both groups experienced more difficulties in the verb comprehension task, indicated by lower accuracy and longer RTs in PWA and longer RTs in NBD. PWA who were performing the task within normal limits (i.e., demonstrated no difference in accuracy compared to the control group) still showed significantly longer RTs in the verb task than controls.  Also, PWA who demonstrated similar accuracy in both tasks had longer RTs in the verb task relative to the noun task. The pattern was general and no differences were observed in performance between participants with fluent and non-fluent aphasia types. Moreover, the observed dissociations in RTs were greater for PWA than for NBD, indicating that a damaged language system experiences even more difficulties in processing verbs.  

Conclusions: Overall, the study demonstrated the relative difficulty of verb processing in a comprehension task, supporting the hypothesis that verb processing difficulties are modality-general. The new test allows researchers to compare performance on noun and verb comprehension and registers even subtle differences by measuring RTs. Background: There is growing evidence that verbs are often more difficult to process than nouns and that verb retrieval is more commonly affected in aphasia. However, existing observations are largely based on naming and semantic judgment tasks. The extent to which this processing difficulty is modality-general has yet to be established. In addition, most of the present language batteries do not allow direct comparison between noun and verb comprehension deficits. To fill this gap, a test was developed for the assessment of noun and verb lexical-semantic comprehension.

Aims: The current study investigates whether verb processing difficulties are modality-general by administering novel balanced noun and verb comprehension tasks to participants with and without aphasia.

Method: In this study we directly compare the difficulty of comprehension of verbs versus nouns in a group of participants with aphasia (PWA, n = 32) and non-brain-damaged, age-matched participants (NBD, n = 20). The word comprehension task was implemented on a tablet measuring accuracy and reaction times (RTs). Participants were required to listen to an aurally presented word and match it to one of four pictures (a target and three distractors: semantic, phonological and irrelevant) by tapping on it with the non-dominant hand. In total, 30 nouns and 30 verbs were presented.  The verbal stimuli in the two tasks were matched on relevant psychometric properties such as familiarity, age of acquisition, subjective visual complexity, imageability, image agreement and frequency.

Results: Both groups experienced more difficulties in the verb comprehension task, indicated by lower accuracy and longer RTs in PWA and longer RTs in NBD. PWA who were performing the task within normal limits (i.e., demonstrated no difference in accuracy compared to the control group) still showed significantly longer RTs in the verb task than controls.  Also, PWA who demonstrated similar accuracy in both tasks had longer RTs in the verb task relative to the noun task. The pattern was general and no differences were observed in performance between participants with fluent and non-fluent aphasia types. Moreover, the observed dissociations in RTs were greater for PWA than for NBD, indicating that a damaged language system experiences even more difficulties in processing verbs.  

Conclusions: Overall, the study demonstrated the relative difficulty of verb processing in a comprehension task, supporting the hypothesis that verb processing difficulties are modality-general. The new test allows researchers to compare performance on noun and verb comprehension and registers even subtle differences by measuring RTs. 

Background: The relationship between spontaneous speech and formal language testing in people with brain tumors (gliomas) has been rarely studied. In clinical practice, formal testing is typically used, while spontaneous speech is less often evaluated quantitatively. However, spontaneous speech is quicker to sample and may be less prone to test/retest effects, making it a potential candidate for assessing language impairments when there is restricted time or when the patient is unable to undertake prolonged testing.

Aim: To assess whether quantitative spontaneous speech analysis and formal testing detect comparable language impairments in people with gliomas. Specifically, we addressed (a) whether both measures detected comparable language impairments in our patient sample; and (b) which language levels, assessment times, and spontaneous speech variables were more often impaired in this subject group.

Method: Five people with left perisylvian gliomas performed a spontaneous speech task and a formal language assessment. Tests were administered before surgery, within a week after surgery, and seven months after surgery. Performance on spontaneous speech was compared with that of 15 healthy speakers.

Results: Language impairments were detected more often with both measures than with either measure independently. Lexical–semantic impairments were more common than phonological and grammatical impairments, and performance was equally impaired across assessment time points. Incomplete sentences and phonological paraphasias were the most common error types.

Conclusions: In our sample both spontaneous speech analysis and formal testing detected comparable language impairments. Currently, we suggest that formal testing remains overall the better option, except for cases in which there are restrictions on testing time or the patient is too tired to undergo formal testing. In these cases, spontaneous speech may provide a viable alternative, particularly if automated analysis of spontaneous speech becomes more readily available in the future. These results await replication in a bigger sample and/or other populations.

Previous research showed that polysemous and homonymous words are processed differently. However, mechanisms underlying processing of ambiguous words are still unclear. The goal of the present study was to investigate comprehension of metonymies, metaphors, and homonyms using priming paradigm and the method of event-related potentials (ERPs). We asked participants to read two-word phrases with ambiguous words and make a sensicality judgement. The results demonstrated the difference between metonymic and metaphorical senses of polysemous words in the amount of priming for the literal sense. The priming effect between metonymic and literal senses supports the idea that these senses share a single representation in the mental lexicon. In contrast, metaphorical senses of polysemous words showed a very limited priming effect on literal senses of the same words. Similar results were observed for different meanings of homonymous words. We conclude that metaphorical senses should have separate representations in the mental lexicon similarly to homonyms.

Patient studies and brain stimulation evidence suggest that language processing can be enhanced by altering the interhemispheric balance: namely, preferentially enhancing left-hemisphere activity while suppressing right-hemisphere activity. To our knowledge, no study has yet compared the effects of such bilateral brain stimulation to both logically necessary control conditions (separate left- and right-hemisphere stimulation). This study did so in a between-group sham-controlled design, applying transcranial direct current stimulation over Broca’s area and/or its homologue in 72 healthy participants. The effects were measured not only in a single-word-level task but also in a sentence-level task, rarely tested previously. We did not find either any significant overall effects of stimulation or greater stimulation effects in the bilateral compared to control groups. This null result, obtained in a large sample, contributes to the debate on whether tDCS can modulate language processing in healthy individuals.

Currently, a distributed bilateral network of frontal-parietal areas is regarded as the neural substrate of working memory (WM), with the verbal WM network being more left-lateralized. This conclusion is based primarily on functional magnetic resonance imaging (fMRI) data that provides correlational evidence for brain regions involved in a task. However, fMRI cannot differentiate the areas that are fundamentally required for performing a task. These data can only come from brain-injured individuals who fail the task after the loss of specific brain areas. In addition to the lack of complimentary data, is the issue of the variety in the WM tasks used to assess verbal WM. When different tasks are assumed to measure the same behavior, this may mask the contributions of different brain regions. Here, we investigated the neural substrate of WM by using voxel-based lesion symptom mapping (VLSM) in 49 individuals with stroke-induced left hemisphere brain injuries. These participants completed two different verbal WM tasks: complex listening span and a word 2-back task. Behavioral results indicated that the two tasks were only slightly related, while the VLSM analysis revealed different critical regions associated with each task. Specifically, significant detriments in performance on the complex span task were found with lesions in the inferior frontal gyrus, while for the 2-back task, significant deficits were seen after injury to the superior and middle temporal gyri. Thus, the two tasks depend on the structural integrity of different, non-overlapping frontal and temporal brain regions, suggesting distinct neural and cognitive mechanisms triggered by the two tasks: rehearsal and cue-dependent selection in the complex span task, versus updating/auditory recognition in the 2-back task. These findings call into question the common practice of using these two tasks interchangeably in verbal WM research and undermine the legitimacy of aggregating data from studies with different WM tasks. Thus, the present study points out the importance of lesion studies in complementing functional neuroimaging findings and highlights the need to consider task demands in neuroimaging and neuropsychological investigations of WM.

Older adults demonstrate a slower speed of linguistic processing, including sentence processing. In non-linguistic cognitive domains such as memory, research suggests that age- related slowing of processing speed may be a strategy adopted in order to avoid potential error and/or to spare “cognitive resources". So far, very few studies have tested whether older adults’ slower processing speed in the linguistic domain has a strategic nature as well. To fill this gap, we tested whether older adults can maintain language processing accuracy when a faster processing speed is enforced externally. Specifically, we compared sentence comprehension accuracy in younger and older adults when sentences were presented at the participant’s median self-paced reading speed versus twice as fast. We hypothesized that an external speed increase will cause a smaller accuracy decline in older than younger adults because older adults tend to adopt self-paced processing speeds “further away” from their performance limits. The hypothesis was not confirmed: the decline in accuracy due to faster presentation did not differ by age group. Thus, we found no evidence for strategic nature of age-related slowing of sentence processing. Based on our experimental design, we suggest that the age-related slowing of sentence processing is caused not only by motor slowdown, but also by a slowdown in cognitive processing.

Phonological neighbourhood density (PND) refers to the number of words which can be formed from a given word by substituting, adding or deleting one phoneme. Thus, word with many similar sounding neighbours has a dense neighbourhood, whereas a word with few neighbours or without neighbors has a sparse neighbourhood. Previous studies have shown that dense and sparse neighbourhoods influence word production in different ways. Research in English-speaking adults demonstrated that words with dense neighbourhood are produced faster than words with sparse neighbourhood, facilitating lexical access. At the same time, sparse neighbourhood inhibits word production. Interestingly, studies in Spanish adults showed the reverse effect: dense neighbourhood inhibits word production whereas sparse neighbourhood facilitates it. This cross-linguistic difference in the PND pattern was explained in terms of morphological complexity of Spanish in comparison to English. Although there are numerous studies of the PND effect in adults, some questions remain unknown. For example, how does PND influence word production in morphologically more complex language than Spanish? Or, how does the PND pattern develop in children? The present paper aims to explore these questions.

n the current experiment, participants read word-by-word sentences containing gender (adjective-noun) and number (article-noun) disagreement in Dutch while EEG was recorded. Number and gender disagreement were expected to elicit different responses due to several reasons. Firstly, gender is a lexical feature whose value (e.g., masculine or feminine) is stored in the lexicon, whereas number value is assigned depending on conceptual knowledge (numerosity). Also, Dutch marks number but not gender on the noun. Finally, due to the morphological nature of number, number disagreement provides more repair options than gender disagreement, thereby increasing the processing load. Both gender and number disagreement elicited a P600, but no LAN. The P600 effect was larger for number than gender disagreement in the late P600 stage. Since the observed effect was in the late P600 stage, we suggest that the most salient difference between the two types of disagreement lies in the increased repair complexity for number disagreement compared to gender disagreement.

The paper describes the results of the first shared task on word sense induction (WSI) for the Russian language. While similar shared tasks were conducted in the past for some Romance and Germanic languages, we explore the performance of sense induction and disambiguation methods for a Slavic language that shares many features with other Slavic languages, such as rich morphology and virtually free word order. The participants were asked to group contexts of a given word in accordance with its senses that were not provided beforehand. For instance, given a word “bank” and a set of contexts for this word, e.g. “bank is a financial institution that accepts deposits” and “river bank is a slope beside a body of water”, a participant was asked to cluster such contexts in the unknown in advance number of clusters corresponding to, in this case, the “company” and the “area” senses of the word “bank”. For the purpose of this evaluation campaign, we developed three new evaluation datasets based on sense inventories that have different sense granularity. The contexts in these datasets were sampled from texts of Wikipedia, the academic corpus of Russian, and an explanatory dictionary of Russian. Overall, 18 teams participated in the competition submitting 383 models. Multiple teams managed to substantially outperform competitive state-of-the-art baselines from the previous years based on sense embeddings.

The article introduces the new corpus of eye-movements in silent reading – the Russian Sentence Corpus (RSC). Russian uses Cyrillic script that has not yet been investigated in cross-linguistic eye-movement research. As in every language studied so far, we have confirmed the expected effects of low-level parameters, such as word length, frequency, and predictability, on the eye-movements of skilled Russian readers. These findings allow us to add Slavic languages using Cyrillic script (exemplified by Russian) to the growing number of languages with different orthographies ranging from the Roman-based European languages to logographic Asian ones whose basic eye-movement benchmarks conform to the universal comparative science of reading (Share 2008). We additionally report basic descriptive corpus statistics, and three exploratory investigations of the effects of Russian morphology on the basic eye-movement measures that illustrate the kinds of questions researchers can answer using the RSC. The annotated corpus is freely available from the project page at Open Science Framework: https://osf.io/x5q2r/.

Classical models of speech production have primarily focused on the psycholinguistic aspects of the process, identifying its components (i. e., meaning generation, lexical selection, functional assignment, phonological encoding and articulation) and how they interact [Bock, Levelt 1994; Dell, Change, Griffin 1999; Fromkin 1973; Garrett 1975 et al.]. This integral approach has pro- vided us with a solid conceptual understanding of the various processes involved at every stage of speech production, suggesting, however, that each of these stages is likely to have its own unique operational mechanisms. Thus, a more detailed exploration of each of these individual components of the speech production system is now required to build more refined and realis- tic models of speech production, reflecting how this multicomponent task of communication is orchestrated by the brain. For example, the articulation of speech needs to be studied separately from the lexical selection process because each relies on its own specific set of neuroanatomical structures and has its individual mechanisms of functioning and pathogenesis. “Neural Control of Speech” by F. H. Guenther is a brilliant attempt to tackle the problem using the “divide and conquer” approach. 

Experimental studies on polysemy have come to contradictory conclusions on whether words with multiple senses are stored as separate or shared mental representations. The present study examined the semantic relatedness and semantic similarity of literal and non-literal (metonymic and metaphorical) senses of three word classes: nouns, verbs, and adjectives. Two methods were used: a psycholinguistic experiment and a distributional analysis of corpus data. In the experiment, participants were presented with 6–12 short phrases containing a polysemous word in literal, metonymic, or metaphorical senses and were asked to classify them so that phrases with the same perceived sense were grouped together. To investigate the impact of professional background on their decisions, participants were controlled for linguistic vs. non-linguistic education. For nouns and verbs, all participants preferred to group together phrases with literal and metonymic senses, but not any other pairs of senses. For adjectives, two pairs of senses were often grouped together: literal with metonymic, and metonymic with metaphorical. Participants with a linguistic background were more accurate than participants with non-linguistic backgrounds, although both groups shared principal patterns of sense classification. For the distributional analysis of corpus data, we used a semantic vector approach to quantify the similarity of phrases with literal, metonymic, and metaphorical senses in the corpora. We found that phrases with literal and metonymic senses had the highest degree of similarity for the three word classes, and that metonymic and metaphorical senses of adjectives had the highest degree of similarity among all word classes. These findings are in line with the experimental results. Overall, the results suggest that the mental representation of a polysemous word depends on its word class. In nouns and verbs, literal and metonymic senses are stored together, while metaphorical senses are stored separately; in adjectives, metonymic senses significantly overlap with both literal and metaphorical senses.