Are subjective language complaints in memory clinic patients informative?

To diagnose mild cognitive impairment, it is crucial to understand whether subjective cognitive complaints reflect objective cognitive deficits. This question has mostly been investigated in the memory domain, with mixed results. Our study was one of the first to address it for language. Participants were 55-to-93-year-old memory clinic patients (n = 163). They filled in a questionnaire about subjective language and memory complaints and performed two language tasks (naming-by-definition and sentence comprehension). Greater language complaints were associated with two language measures, thus showing a moderate value in predicting language performance. Greater relative severity of language versus memory complaints was a better predictor, associated with three language performance measures. Surprisingly, greater memory complaints were associated with better naming, probably due to anosognosia in further disease progression or personality-related factors. Our findings highlight the importance of relative complaint severity across domains and, clinically, call for developing self-assessment questionnaires asking specific questions about multiple cognitive functions.

Disruptions in modular structure and network integration of language-related network predict language performance in temporal lobe epilepsy: Evidence from graph-based analysis.

OBJECTIVE: Temporal lobe epilepsy (TLE) is a network disorder that alters the total organization of the language-related network. Task-based functional magnetic resonance imaging (fMRI) aimed at functional connectivity is a direct method to investigate how the network is reorganized. However, such studies are scarce and represented mostly by the resting-state analysis of the individual connections between regions. To fill this gap, we used a graph-based analysis, which allows us to cover the total language-related network changes, such as disruptions in an integration/segregation balance, during a language task in TLE. METHODS: We collected task-based fMRI data with sentence completion from 19 healthy controls and 28 people with left TLE. Using graph-based analysis, we estimated how the language-related network segregated into modules and tested whether they differed between groups. We evaluated the total network integration and the integration within modules. To assess intermodular integration, we considered the number and location of connector hubs-regions with high connectivity. RESULTS: The language-related network was differently segregated during language processing in the groups. While healthy controls showed a module consisting of left perisylvian regions, people with TLE exhibited a bilateral module formed by the anterior language-related areas and a module in the left temporal lobe, reflecting hyperconnectivity within the epileptic focus. As a consequence of this reorganization, there was a statistical tendency that the dominance of the intramodular integration over the total network integration was greater in TLE, which predicted language performance. The increase in the number of connector hubs in the right hemisphere, in turn, was compensatory in TLE. SIGNIFICANCE: Our study provides insights into the reorganization of the language-related network in TLE, revealing specific network changes in segregation and integration. It confirms reduced global connectivity and compensation across the healthy hemisphere, commonly observed in epilepsy. These findings advance the understanding of the network-based reorganizational processes underlying language processing in TLE.

Do we rely on good-enough processing in reading under auditory and visual noise?

Noise, as part of real-life communication flow, degrades the quality of linguistic input and affects language processing. According to predictions of the noisy-channel and good-enough processing models, noise should make comprehenders rely more on word-level semantics instead of actual syntactic relations. However, empirical evidence supporting this prediction is still lacking. For the first time, we investigated whether auditory (three-talker babble) and visual (short idioms appearing next to a target sentence on the screen) noise would trigger greater reliance on semantics and make readers of Russian sentences process the sentences superficially. Our findings suggest that, although Russian speakers generally relied on semantics in sentence comprehension, neither auditory nor visual noise increased this reliance. The only effect of noise on semantic processing was found in reading speed under auditory noise measured by first fixation duration: only without noise, the semantically implausible sentences were read slower than semantically plausible ones. These results do not support the predictions of the study based on the noisy-channel and good-enough processing models, which is discussed in light of the methodological differences among the studies of noise and their possible limitations.

HD-tDCS of primary and higher-order motor cortex affects action word processing.

The contribution of action-perception systems of the brain to lexical semantics remains controversial. Here, we used high-definition transcranial direct current stimulation (HD-tDCS) in healthy adults to examine the role of primary (left hand motor area; HMA) and higher-order (left anterior inferior parietal lobe; aIPL) action areas in action-related word processing (action verbs and manipulable nouns) compared to non-action-related control words (non-action verbs and non-manipulable nouns). We investigated stimulation-related effects at three levels of semantic processing: subliminal, implicit, and explicit. Broadly, we found that stimulation of HMA and aIPL resulted in relative facilitation of action-related language processing compared to non-action. HMA stimulation facilitated action verb processing in subliminal and implicit task contexts, suggesting that HMA helps represent action verbs even in semantically shallow tasks. HMA stimulation also facilitated manipulable noun comprehension in an explicit semantic task, suggesting that HMA contributes to manipulable noun comprehension when semantic demands are high. aIPL stimulation facilitated both manipulable noun and action verb processing during an implicit task. We suggest that both HMA and aIPL play a functional role in action semantics. HMA plays a general role in the semantics of actions and manipulable objects, while aIPL is important only when visuo-motor coordination is required for the action.

Repetitive transcranial magnetic stimulation modulates action naming over the left but not right inferior frontal gyrus.

fMRI language mapping studies report right-hemispheric contribution to language in healthy individuals. However, it remains unclear whether these right-hemispheric patterns of activity are critical for language, which is highly relevant for clinical preoperative language mapping. The available findings are controversial. In this study, we first measured individual patterns of language lateralization with an fMRI language localizer in healthy participants with different handedness (N = 31). Then, the same participants received rTMS over the individual coordinates of peak fMRI-based activation in the left and right inferior frontal gyri. During rTMS, participants performed a picture naming task. It included both objects and actions to test whether naming of nouns and verbs would be equally modulated by rTMS. Stimulation of the left inferior frontal gyrus resulted in accuracy facilitation of verb production regardless of individual language lateralization. No modulation of object naming was found at any stimulation site in terms of accuracy nor reaction time. This study causally confirmed the critical contribution of the left, but not the right hemisphere to verb production regardless of the language lateralization patterns observed with fMRI. Also, the results stress that action rather than object naming is the task of choice for mapping language in the frontal lobe.

A New Functional Magnetic Resonance Imaging Localizer for Preoperative Language Mapping Using a Sentence Completion Task: Validity, Choice of Baseline Condition, and Test-Retest Reliability.

To avoid post-neurosurgical language deficits, intraoperative mapping of the language function in the brain can be complemented with preoperative mapping with functional magnetic resonance imaging (fMRI). The validity of an fMRI "language localizer" paradigm crucially depends on the choice of an optimal language task and baseline condition. This study presents a new fMRI "language localizer" in Russian using overt sentence completion, a task that comprehensively engages the language function by involving both production and comprehension at the word and sentence level. The paradigm was validated in 18 neurologically healthy volunteers who participated in two scanning sessions, for estimating test-retest reliability. For the first time, two baseline conditions for the sentence completion task were compared. At the group level, the paradigm significantly activated both anterior and posterior language-related regions. Individual-level analysis showed that activation was elicited most consistently in the inferior frontal regions, followed by posterior temporal regions and the angular gyrus. Test-retest reliability of activation location, as measured by Dice coefficients, was moderate and thus comparable to previous studies. Test-retest reliability was higher in the frontal than temporo-parietal region and with the most liberal statistical thresholding compared to two more conservative thresholding methods. Lateralization indices were expectedly left-hemispheric, with greater lateralization in the frontal than temporo-parietal region, and showed moderate test-retest reliability. Finally, the pseudoword baseline elicited more extensive and more reliable activation, although the syllable baseline appears more feasible for future clinical use. Overall, the study demonstrated the validity and reliability of the sentence completion task for mapping the language function in the brain. The paradigm needs further validation in a clinical sample of neurosurgical patients. Additionally, the study contributes to general evidence on test-retest reliability of fMRI.

Reliance on semantic and structural heuristics in sentence comprehension across the lifespan.

People sometimes misinterpret the sentences that they read. One possible reason suggested in the literature is a race between slow bottom-up algorithmic processing and "fast and frugal" top-down heuristic processing that serves to support fast-paced communication but sometimes results in incorrect representations. Heuristic processing can be both semantic, relying on world knowledge and semantic relations between words, and structural, relying on structural economy. Scattered experimental evidence suggests that reliance on heuristics may change from greater reliance on syntactic information in younger people to greater reliance on semantic information in older people. We tested whether the reliance on structural and semantic heuristics changes with age in 137 Russian-speaking adolescents, 135 young adults, and 77 older adults. In a self-paced reading task with comprehension questions, participants read unambiguous high- versus low-attachment sentences that were either semantically plausible or implausible: i.e., the syntactic structure either matched or contradicted the semantic relations between words. We found that the use of top-down heuristics in comprehension increased across the lifespan. Adolescents did not rely on structural heuristics, in contrast to young and older adults. At the same time, older adults relied on semantic heuristics more than young adults and adolescents. Importantly, we found that top-down heuristic processing was faster than bottom-up algorithmic processing: slower reading times were associated with greater accuracy specifically in implausible sentences.

Advancing Neurolinguistics in Russia: Experience and Implications of Building Experimental Research and Evidence-Based Practices.

Russia has rich theoretical and behavioral research traditions in neurolinguistics and neuropsychology, but at the beginning of the twenty-first century contemporary experimental research in these disciplines remained limited, leading to proliferation of non-evidence-based approaches in education, healthcare, and public beliefs. An academic response to this was the establishment of the Center for Language and Brain at the HSE University, Moscow, which focused on experimental psycho- and neurolinguistic research and related evidence-based practices. The Center has grown from a small group of young researchers to a large interdisciplinary unit that conducts cutting-edge research utilizing multi-site settings and novel structural and functional neuroimaging methods. The overarching aim of the Center's research is to promote scientifically grounded treatment of the language-brain relationship in the educational, clinical, and industry settings. Specifically, translational research at the Center is contributing to the advancement of clinical practice in Russia: from providing the first standardized aphasia language test to implementing protocols for intraoperative language mapping in neurosurgery departments across the country. Within research projects, a new generation of scientists is successfully being fostered, while a broader student audience is reached via courses taught by staff of the Center to students of different majors. Notable examples of public outreach programs at the Center are the Annual Summer Neurolinguistics School attracting hundreds of attendees from different countries each year, and community projects focused on raising awareness about aphasia. Together, these efforts aim to increase scientific knowledge in a multi-professional audience. In this paper, we will share our joint experiences in establishing, building, and promoting a neurolinguistics research center in Russia and the impact that this work has had on the broader public. We will delineate specific milestones of this journey and focus on the main pillars that have contributed to our progress: research, clinical work, teaching, and public outreach programs. We hope that this critical appraisal of our experiences can serve simultaneously as an inspiration and a practical guide for other groups developing research, clinical, and educational programs in different neuroscientific disciplines across the globe and aiming to improve the quality of the neuroscientific information available to the public.

HD-tDCS over motor cortex facilitates figurative and literal action sentence processing.

The extent to which action and perception systems of the brain are involved in semantic comprehension remains controversial. Whether figurative language, such as metaphors and idioms, is grounded in sensory-motor systems is especially contentious. Here, we used high-definition transcranial direct current stimulation (HD-tDCS) in healthy adults to examine the role of the left-hemisphere motor cortex during the comprehension of action sentences, relative to comprehension of sentences with visual verbs. Action sentences were divided into three types: literal, metaphoric, or idiomatic. This allowed us to ask whether processing of action verbs used in figurative contexts relies on motor cortex. The results revealed that action sentence comprehension response times were facilitated relative to the visual sentence control. Significant interaction relative to visual sentences was observed for literal, metaphoric, and idiomatic action sentences with HD-tDCS of the motor cortex. These results suggest that the left motor cortex is functionally involved in action sentence comprehension. Furthermore, this involvement exists when the action content of the sentences is figurative, for both idiomatic and metaphoric cases. The results provide evidence for functional links between conceptual and action systems of the brain.

Left frontal aslant tract and lexical selection: Evidence from frontal lobe lesions.

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 task, tapping into conceptual and lexical selection, and the picture-word interference 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.

Cortical and structural-connectivity damage correlated with impaired syntactic processing in aphasia.

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 quantified with the Northwestern 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.

No evidence for strategic nature of age-related slowing in sentence processing.

Older adults demonstrate a slower speed of linguistic processing, including sentence processing. In nonlinguistic 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. On the basis of 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. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Modulating the interhemispheric balance in healthy participants with transcranial direct current stimulation: No significant effects on word or sentence processing.

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.

Task-dependent neural and behavioral effects of verb argument structure features.

Understanding which verb argument structure (VAS) features (if any) are part of verbs' lexical entries and under which conditions they are accessed provides information on the nature of lexical representations and sentence construction. We investigated neural and behavioral effects of three understudied VAS characteristics (number of subcategorization options, number of thematic options and overall number of valency frames) in lexical decision and sentence well-formedness judgment in healthy adults. VAS effects showed strong dependency on processing conditions. As reflected by behavioral performance and neural recruitment patterns, increased VAS complexity in terms of subcategorization options and thematic options had a detrimental effect on sentence processing, but facilitated lexical access to single words, possibly by providing more lexico-semantic associations and access routes (facilitation through complexity). Effects of the number of valency frames are equivocal. We suggest that VAS effects may be mediated semantically rather than by a dedicated VAS module in verbs' representations.

Verb Argument Structure in Narrative Speech: Mining AphasiaBank.

Previous research has found that verb argument structure characteristics (such as the number of participant roles in the situation described by the verb) can facilitate or hinder aphasic language production and comprehension in constrained laboratory tasks. This research needs to be complemented by studies of narrative or unrestricted speech, which can capture the spontaneous selection of verbs and grammatical structures by people with aphasia and may be particularly sensitive to the relative cost of access to different verb types in more natural conditions. Focusing on the number of subcategorization options, we investigated verb argument structure effects in a large sample of narratives from AphasiaBank, by speakers with aphasia, as well as control speakers without brain damage. Verb argument structure complexity did not negatively affect verb selection in any type of aphasia. However, people with aphasia, particularly with Broca's aphasia, used verbs in less complex and diverse ways, with fewer arguments and less diverse subcategorization options. In line with previous research, this suggests that deficits in verb use in aphasia are likely due to difficulties with the online application of or partial damage to verb argument structure knowledge.

What is it that lingers? Garden-path (mis)interpretations in younger and older adults.

Previous research has shown that comprehenders do not always conduct a full (re)analysis of temporarily ambiguous "garden-path" sentences. The present study used a sentence-picture matching task to investigate what kind of representations are formed when full reanalysis is not performed: Do comprehenders "blend" two incompatible representations as a result of shallow syntactic processing or do they erroneously maintain the initial incorrect parsing without incorporating new information, and does this vary with age? Twenty-five younger and 15 older adults performed a multiple-choice sentence-picture matching task with stimuli including early-closure garden-path sentences. The results suggest that the type of erroneous representation is affected by linguistic variables, such as sentence structure, verb type, and semantic plausibility, as well as by age. Older adults' response patterns indicate an increased reliance on inferencing based on lexical and semantic cues, with a lower bar for accepting an initial parse and with a weaker drive to reanalyse a syntactic representation. Among younger adults, there was a tendency to blend two representations into a single interpretation, even if this was not licensed by the syntax.

On the Use of the Terms Anodal and Cathodal in High-Definition Transcranial Direct Current Stimulation: A Technical Note.

BACKGROUND: The terms "anodal" and "cathodal" are widely used to describe transcranial direct current stimulation (tDCS) of opposing polarities, often interpreted as excitatory and inhibitory, respectively. However, high-definition tDCS allows for complex electrode configurations that may not be characterized accurately as "anodal" and "cathodal." METHOD: To illustrate challenges to data interpretation that may result from unclarity about the neuromodulatory effects of different field orientations, we present two high-definition tDCS experiments in the language domain, with different electrode configurations. We also present the modeled electric fields for a traditional tDCS setup, showing how brain stimulation may far exceed target regions. CONCLUSIONS: More research is warranted on the hypothesized inhibitory or excitatory effects of different electrode configurations. Moreover, conventional bicephalic 1 × 1 configurations using sponges or HD electrodes may not be accurately described by the terms "anodal" and "cathodal" either, as these terms only pertain to the desired effects over an area of interest, but not any other areas affected. Therefore, design and interpretation of (HD-)tDCS and conventional tDCS research studies should not be constrained by the anodal/cathodal dichotomy.

Russian normative data for 375 action pictures and verbs.

The present article introduces a Russian-language database of 375 action pictures and associated verbs with normative data. The pictures were normed for name agreement, conceptual familiarity, and subjective visual complexity, and measures of age of acquisition, imageability, and image agreement were collected for the verbs. Values of objective visual complexity, as well as information about verb frequency, length, argument structure, instrumentality, and name relation, are also provided. Correlations between these parameters are presented, along with a comparative analysis of the Russian name agreement norms and those collected in other languages. The full set of pictorial stimuli and the obtained norms may be freely downloaded from http://neuroling.ru/en/db.htm for use in research and for clinical purposes.

Effects of representational distance between meanings on the neural correlates of semantic ambiguity.

Psycholinguistic research demonstrates that representational distance between meanings influences recognition of ambiguous words. Our goal was to investigate whether the neural correlates of ambiguity are also modulated by representational distance as a function of syntactic similarity (i.e., grammatical class) and meaning dominance. In an event-related fMRI experiment, participants completed a visual lexical decision task that included balanced and unbalanced noun-noun and noun-verb homonyms, unambiguous words, and nonwords. Syntactic similarity effects were observed in left inferior frontal regions, with greater activation for noun-verb than noun-noun homonyms. Meaning dominance effects were observed in left middle and superior temporal regions, with greater activation for balanced than unbalanced homonyms. These findings indicate that the behavioral cost associated with processing ambiguous word meanings, modulated by syntactic similarity and meaning dominance, is reflected in the neural systems underlying ambiguity processing, as frontal and temporal regions are recruited by increased competition as a function of representational distance.