Publications

The frontal aslant tract (FAT) is a white-matter tract connecting the inferior frontal gyrus (IFG) and the supplementary motor complex (SMC). Damage to either component of the network causes spontaneous speech dysfluency, indicating its critical role in language production. However, spontaneous speech dysfluency may stem from various lower-level linguistic deficits, precluding inferences about the nature of linguistic processing subserved by the IFG-SMC network. Since the IFG and the SMC are attributed a role in conceptual and lexical selection during language production, we hypothesized that these processes rely on the IFG-SMC connectivity via the FAT. We analysed the effects of FAT volume on conceptual and lexical selection measures following frontal lobe stroke. The measures were obtained from the sentence completion (SC) task, tapping into conceptual and lexical selection, and the picture-word interference (PWI) task, providing a more specific measure of lexical selection. Lower FAT volume was not associated with lower conceptual or lexical selection abilities in our patient cohort. Current findings stand in marked discrepancy with previous lesion and neuroimaging evidence for the joint contribution of the IFG and the SMC to lexical and conceptual selection. A plausible explanation reconciling this discrepancy is that the IFG-SMC connectivity via the FAT does contribute to conceptual and/or lexical selection but its disrupted function undergoes reorganisation over the course of post-stroke recovery. Thus, our negative findings stress the importance of testing the causal role of the FAT in lexical and conceptual selection in patients with more acute frontal lobe lesions.

This chapter deals with segmentation, definition of reference units and annotation of the first corpus of Russian narratives by individuals with brain damage – people with aphasia and right hemisphere damage – and neurologically healthy speakers.  We show that such parameters as pause length and intonation contours cannot be used for segmentation of impaired speech. Instead, we use syntactic criteria for identification of the reference, or – as they are called in this paper – elementary discourse units (EDUs). The Russian CliPS (Clinical Pear Stories) corpus contains multi-layer annotation of audio- and video-recordings, performed on micro- and macro-linguistic level, and can be used as a source for qualitative and quantitative research on various aspects of speech in aphasia and right hemisphere damage.

We report results from a self-paced silent reading study and a self-paced reading-aloud study examining ambiguous forms (heteronyms) of Russian animate and inanimate nouns which are differentiated in speech through word stress, e.g. uCHItelja.TEACHER.GEN/ACC.SG and uchiteLJA.TEACHERS.NOM.PL1. During reading, the absence of the auditory cue (word stress) to word identification results in morphologically ambiguous forms since both words have the same inflectional marking, -ja. Because word inflection is a reliable cue to syntactic role assignment, the ambiguity affects the level of morphology and of syntactic structure. However, word order constraints and frequency advantage of the GEN over both the NOM and the ACC noun forms with the -a/-ja inflection should pre-empt two different syntactic parses (OVS vs SVO) when the heteronym is sentence-initial. We inquired into whether the parser is aware of the multi-level ambiguity and whether selected conflicting cues (case, word order, animacy) can prime parallel access to several structural parses. We found that animate and inanimate nouns patterned differently. The difference was consistent across the experiments. Against the backdrop of classical sentence processing dichotomies, the emergent pattern fits with the serial interactive or the parallel modular parser hypothesis.

ABSTRACT

Background: The Aphasia Rapid Test (ART) is a screening test developed for fast speech/language assessment of people in the acute stroke period. This test has been developed for French and English and was recently adapted for Portuguese and Italian. Nowadays, such a standardised screening test is in a great need at clinics with Russian-speaking patients. To fill this gap, the ART was adapted for Russian. 

Aims: The current study investigated whether the Russian ART meets all the psychometric standards, and whether it is suitable for detecting speech/language disorders and estimating their severity, as well as for the evaluation of improvement in the acute post-stroke period.

Methods & Procedure: First, we evaluated the validity, sensitivity, specificity, accuracy, test-retest reliability, inter-item consistency and inter-rater reliability of the test in a group of people with chronic speech/language disorders (N = 55) and in an age-matched control group of non-brain-damaged individuals (N = 50). Participants performed the Russian ART, and their linguistic status was confirmed by the Russian e-version of the Token Test. Second, to test the appropriateness of the Russian ART in the acute post-stroke period, a clinical group of such individuals (N = 43) performed the ART and the Token Test, as well as the Vasserman’s scale which is widely used in Russian clinics. Finally, 16 people in the acute stroke period performed the Russian ART twice to prove that the test can detect early changes in an acute patient’s linguistic status.

Outcomes & Results: The results showed that the Russian ART can be considered as a valid, sensitive, specific, and accurate screening tool with the high test-retest reliability, inter-item consistency, and inter-rater reliability. In the acute post-stroke group, the correlation between the ART and the Token Test was high and significant; a moderate correlation and no significant correlation were found between the Vasserman’s scale and the Russian ART and the Token Test correspondingly. The Russian ART also allowed us to detect the improvement in speech/language status in the acute post-stroke period.

Conclusion: The study confirmed that the Russian ART meets all required standards to be suggested for usage in a Russian-speaking clinical population. This test was relevant for detecting the presence and severity of speech/language disorders and to measure the improvement in the acute post-stroke period.

Many aphasia assessments and therapies select and/or sequence verbs based on linguistic complexity of their verb argument structure (VAS). However, further empirical testing is needed to fully understand whether and how VAS parameters affect the cognitive difficulty of verb processing in different tasks and contexts. The study investigated whether more linguistically complex VAS universally implies more cognitively difficult verb processing, as predicted by the Argument Structure Complexity Hypothesis (Thompson, 2003). We hypothesized that this would only be the case at sentence level, whereas in single-word tasks more linguistically complex VAS would facilitate lexical access via lexico-semantic associations with potential arguments, contrary to the Argument Structure Complexity Hypothesis.

The effects of three VAS parameters (number of arguments, number of valency frames, canonicity of thematic role marking) were tested in two tasks (single- word naming and cued sentence production) in two aphasia types (fluent and non-fluent, 20 participants per group). We analyzed how VAS parameters affected accuracy and latency in naming and canonicity and well-formedness in sentence production. As hypothesized, VAS effects were different at the sentence versus single-word level. In sentence production, one VAS parameter (the number of arguments) showed the expected negative effect of greater linguistic complexity on sentence canonicity. No other comparisons were significant, likely due to ceiling effects. In contrast, in single-word naming, VAS effects were mixed. The number of valency frames showed the predicted facilitatory effect of linguistic complexity. The number of arguments showed a non-significant statistical trend in the same direction. For canonicity of thematic role marking, greater complexity had a negative effect on naming, possibly because it does not affect the number of lexico-semantic associates of the verb. All findings pertained to both non-fluent and fluent aphasia. When accounting for VAS parameters in selection or sequencing of verbs for assessment or therapy, the cognitive difficulty of verb processing should be estimated for a particular task. In sentence-level grammatical processing, most cognitively difficult verbs are those with more linguistically complex VAS. In contrast, in single verb retrieval, verbs with more linguistically complex VAS may be cognitively simpler if their richer lexico-semantic associations with potential arguments provide extra routes of lexical access.

Previous research on Russian nominal inflection reports a processing advantage for the Nominative case, the citation form, in native and highly proficient nonnative speakers (Gor, Chrabaszcz, & Cook, 2017). However, it remains unclear whether this advantage is present only in single-word presentation, or it is a fundamental property of lexical storage and access. Moreover, it is unknown whether the processing costs for different cases in native and nonnative word recognition reflect the hierarchical structure of the nominal paradigm where cases have different functional load and type frequency. We report two lexical decision experiments with cross-modal morphosyntactic priming, which compare the processing of case-inflected noun targets preceded by adjective primes with ambiguous oblique-case inflections by native speakers, early (heritage) and late learners of Russian. While all groups showed a processing advantage for the citation form, only native speakers and highly proficient late learners were sensitive to the oblique-case type frequency hierarchy.

While different researchers agree that the acquisition of Russian nominal cases proceeds somewhat sequentially, there is no consensus about the exact order of case acquisition in the literature on L1 acquisition (see Ceitlin, 2000; Gvozdev, 1981, 2007; Gagarina & Voeikova, 2009). Besides, accumulated longitudinal data are sparse and disparate, coming from children of different ages, socio-economic statuses, and language acquisition backgrounds. We adopt a psycholinguistic approach to examine acquisition of Russian nominal case inflections by Russian monolingual children (2-5 years old). The goal of the study is twofold: it sets out 1) to examine at what age children learn to generalize rules of noun case usage, and 2) to identify the order of acquisition of Russian oblique case inflections. Children perform a picture-based sentence completion task in which they have to finish the sentence by naming real or nonexisting objects in the pictures. Five sentence frames are constructed to bias the children’s responses towards the use of a noun form in one of the five oblique Russian cases, across three declensions plus plural forms. Data collection is in progress, but interim results show that monolingual Russian-speaking children learn to generalize morphological rules to novel nouns by the age of 2 and that nouns in the plural form are acquired later in language development compared to singular forms. Within the singular forms, 3rd declension cases, especially the instrumental case, present most difficulty. Additionally, 2-3-year-old children tend to substitute oblique cases with the nominative case forms. The results corroborate some of the previous findings and add additional insights into the acquisition of Russian case.

The impact of second language (L2) on first language (L1), known as L2 transfer, has been suggested as a fundamental driving force of L1 attrition. The goal of this study was to test the differential attrition of verb aspect and tense in L1 (Russian) under the influence of L2 (German) grammatical properties. We also investigated whether the age of bilingualism onset and the amount of exposure to L1 modulate this L2 transfer effect.

We tested sentence processing in 30 adult Russian monolingual participants and 30 L1 attritors – Russian-German bilingual speakers – with early versus late bilingualism onset and with low versus high amounts of exposure to L1. Participants heard grammatically correct sentences, sentences with aspect violations and sentences with tense violations, and were asked to detect errors. The accuracy of participants’ responses was analysed using generalized linear mixed-effects modelling in R.

The L2 transfer effect was found, but was strongly modulated by the amount of L1 exposure: only bilinguals with little exposure to L1 showed greater attrition of L1 aspect compared to L1 tense. Moreover, the age of bilingualism onset proved to be more critical than the L2 transfer effect: an earlier bilingualism onset resulted in greater attrition of both aspect and tense in L1. The study provided new evidence about the differential impact of the grammatical similarity between L1 and L2, the age of bilingualism onset and the amount of L1 exposure on aspect and tense processing in L1 attritors.

Our findings suggest that greater L1 use after immigration helps bilingual speakers to be less susceptible to L2 transfer and prevents attrition of L1-specific grammatical categories. Also, a general decline in processing verbal morphology is more likely to occur in speakers with an early rather than a late onset of bilingualism.

People with aphasia frequently have difficulties understanding semantically reversible sentences presented in derived word order. This impairment may be related to the inconsistent processing of morphological information, as well as to difficulties inhibiting the inverse interpretation of the sentence. Studies on bilingual aphasia may contribute to our understanding of these issues by shedding light on i) differences in processing of morphology across languages; ii) enhanced control mechanisms. We studied early Basque- Spanish bilingual speakers with aphasia and monolingual Spanish speakers with aphasia, as well as unimpaired individuals. Using comparable sets of materials across languages, we combined behavioural and eye-tracking methods. Results indicate that i) at the group level, bilingual speakers perform better in Spanish than in Basque, particularly in sentences with Theme-Agent argument order. Individual case analysis shows a pattern of weak dissoci- ation across languages in several participants; ii) bilingual people with aphasia do not outperform monolingual people with aphasia in comprehension accuracy, although gaze data suggests that bilingual speakers exhibit higher inhibition and monitoring abilities.

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.

This paper re-examines theoretical constructs used in the analysis of Russian word stress employing data from speakers with acquired surface dyslexia, a symptom which is characterized by an impaired lexical access and preserved grapheme-phoneme correspondence rules. Russian stems have been traditionally analysed as lexically accented or unaccented, with a default rule deriving surface stress in the latter. In the present study, we found no differences in the production of accented and unaccented stems. Instead, the analysis of errors revealed that the significant factors determining stress placement include stress neighbourhood and stress position. The speakers produced fewer errors in consistently spelled words, and there was a strong tendency to shift stress to the final syllable in consonant-final words and to the penultimate syllable in vowel-final words. These results indicate that the distributional properties play an important role in stress assignment in both accented and unaccented stem types.

Background: Functional and usage-based theories of language are gaining increasing influence in linguistics. These theories understand language structure as underpinned by domain-general neurocognitive capacities and as shaped by usage patterns and the function of language as a means for communication. Accordingly, they entail an approach to aphasia which differs markedly from established ones based on formal theories.

Aims: Based on an outline of central claims in functional and usage-based theories, we aim to show how such theories can cast new light on aphasia.

Methods & Procedures: We focus on two strands of functional and usage-based aphasiological research: 1) research on frequency effects in aphasic speech, 2) and research on the grammatical-lexical distinction and its significance for the description of aphasic speech and the understanding of the causes of aphasia. We review available studies that fall within the two aforementioned strands of research, assessing their strengths and limitations.

Outcomes & Results: Usage-based methodologies are currently being developed that allow for fast quantification of the degree of formulaicity of a language sample and may thus be helpful in ascertaining the role of fossilized multiword expressions in aphasia. In line with central claims in usage-based linguistics, the first results of studies employing these methodologies have shown that frequency and collocation strength facilitate the retrieval of multiword expressions in a way that resembles the way in which lexical frequency facilitate retrieval of isolated words.

A recent functional and usage-based theory understands the grammatical-lexicon distinction as a means for prioritizing parts of complex linguistic messages. Defining grammatical items as items that are discursively secondary (background) and dependent on host items, this theory entails an account of grammatical deficits which bridges the gap between existing structure-oriented and processing-oriented accounts. The theory entails word-class general criteria that allow fine-grained classification of linguistic items as grammatical or lexical. Cross-linguistic studies of verb, pronoun and preposition production show that this classification is significant for the description of aphasic language.

Conclusions: Functional and usage-based studies of aphasia are still sparse, but show promising results. This approach seems especially qualified for understanding 1) the neurocognitive causes of various types of aphasia, 2) the variability across languages, communicative settings (including tasks and modalities), groups of individuals and individuals, which is characteristic of aphasic speech, and 3) the link between aphasia symptoms and the basic need and challenge for people with aphasia: to remain a social being by communicating with other social beings.

According to modern syntactic theories, sentence comprehension can rely not only on grammatically driven algorithmic parsing of grammatical structure but also on good-enough processing, according to which we establish relations between words based on their meanings and our world knowledge without building accurate syntactic relations. Therefore, a good-enough processing strategy may lead to forming incorrect syntactic representations. In a self-paced reading experiment, we investigated how Russian-speaking adolescents (13–17 years old) and adults (20–40 years old) used good-enough vs. algorithmic parsing when reading grammatically complex sentences in a no-noise condition and in the presence of auditory linguistic noise (babble of voices). We found that adolescents relied on good-enough processing less than adults did. At the same time, we found that noise had no effect on reading speed neither in adolescents nor in adults but it speeded up question response time in adolescents.

Despite a persistent interest in verb processing, data on the neural underpinnings of verb retrieval are frag- mentary. The present study is the first to analyze the contributions of both grey and white matter damage affecting verb retrieval through action naming in stroke. We used voxel-based lesion-symptom mapping (VLSM) with an action naming task in 40 left-hemisphere stroke patients. Within the grey matter, we revealed the critical involvement of the left precentral and inferior frontal gyri, insula, and parts of basal ganglia. An overlay of white matter tract probability masks on the VLSM lesion map revealed involvement of left-hemisphere long and short association tracts with terminations in the frontal areas; and several projection tracts. The involvement of these structures is interpreted in the light of existing picture naming models, semantic control processes, and the embodiment cognition framework. Our results stress the importance of both cortico-cortical and cortico-sub- cortical networks of language processing.

Structural changes in the brain take place throughout one’s life. Changes related to cognitive decline may delay the stages of the speech production process in the aging brain. For example, semantic memory decline and poor inhibition may delay the retrieval of a concept from the mental lexicon. Electroencephalography (EEG) is a valuable method for identifying the timing of speech production stages. So far, studies using EEG mainly focused on a particular speech production stage in a particular group of subjects. Differences between subject groups and between methodologies have complicated identifying time windows of the speech production stages. For the current study, the speech production stages lemma retrieval, lexeme retrieval, phonological encoding, and phonetic encoding were tracked using a 64-channel EEG in 20 younger adults and 20 older adults. Picture-naming tasks were used to identify lemma retrieval, using semantic interference through previously named pictures from the same semantic category, and lexeme retrieval, using words with varying age of acquisition. Non-word reading was used to target phonological encoding (using non-words with a variable number of phonemes) and phonetic encoding (using non-words that differed in spoken syllable frequency). Stimulus-locked and response-locked cluster-based permutation analyses were used to identify the timing of these stages in the full time course of speech production from stimulus presentation until 100 ms before response onset in both subject groups. It was found that the timing of each speech production stage could be identified. Even though older adults showed longer response times for every task, only the timing of the lexeme retrieval stage was later for the older adults compared to the younger adults, while no such delay was found for the timing of the other stages. The results of a second cluster-based permutation analysis indicated that clusters that were observed in the timing of the stages for one group were absent in the other subject group, which was mainly the case in stimulus-locked time windows. A z-score mapping analysis was used to compare the scalp distributions related to the stages between the older and younger adults. No differences between both groups were observed with respect to scalp distributions, suggesting that the same groups of neurons are involved in the four stages, regardless of the adults’ age, even though the timing of the individual stages is different in both groups.

Purpose: The current study investigates how individual differences in cochlear implant (CI) users’ sensitivity to word–nonword differences, reflecting lexical uncertainty, relate to their reliance on sentential context for lexical access in processing continuous speech. 

Method: Fifteen CI users and 14 normal-hearing (NH) controls participated in an auditory lexical decision task (Experiment 1) and a visual-world paradigm task (Experiment 2). Experiment 1 tested participants’ reliance on lexical statistics, and Experiment 2 studied how sentential context affects the time course and patterns of lexical competition leading to lexical access.

Results: In Experiment 1, CI users had lower accuracy scores and longer reaction times than NH listeners, particularly for nonwords. In Experiment 2, CI users’ lexical competition patterns were, on average, similar to those of NH listeners, but the patterns of individual CI users varied greatly. Individual CI users’ word–nonword sensitivity (Experiment 1) explained differences in the reliance on sentential context to resolve lexical competition, whereas clinical speech perception scores explained competition with phonologically related words.

Conclusions: The general analysis of CI users’ lexical competition patterns showed merely quantitative differences with NH listeners in the time course of lexical competition, but our additional analysis revealed more qualitative differences in CI users’ strategies to process speech. Individuals’ word–nonword sensitivity explained different parts of individual variability than clinical speech perception scores. These results stress, particularly for heterogeneous clinical populations such as CI users, the importance of investigating individual differences in addition to group averages, as they can be informative for clinical rehabilitation.

Intensive language-action therapy combined with anodal tDCS leads to verb generation improvements in non-fluent post-stroke aphasia

Disorders of language and/or communicative abilities in neurodegenerative diseases are a common phenomenon. Over the past few decades, there has been a growing interest in language performance connected to these diseases. To date, studies in the field of language impairments in Alzheimer’s disease (AD), Parkinson’s disease (PD), and frontotemporal lobar degeneration (FTLD) have focused mainly on particular aspects of language processing in the isolated disease or on comparing certain language tasks in two neurodegenerative diseases. To enable a better understanding and comparison of the underlying linguistic deficits in all three disorders, this paper focuses on phonological, semantic, and grammatical processing in each of the disorders. A review of the literature on language processing deficits reveals that phonological, semantic, and grammatical processing is impaired in the early stages of AD, PD, and FTLD, and that the underlying deficits are some- times linguistic in nature. Language disorders, however, may also reflect cognitive deficits, such as short-term verbal memory impairments, attention deficits, and reduced switching capacities, all of which have an impact on language processing.