Auditory Word Comprehension Is Less Incremental in Isolated Words.

Partial speech input is often understood to trigger rapid and automatic activation of successively higher-level representations of words, from sound to meaning. Here we show evidence from magnetoencephalography that this type of incremental processing is limited when words are heard in isolation as compared to continuous speech. This suggests a less unified and automatic word recognition process than is often assumed. We present evidence from isolated words that neural effects of phoneme probability, quantified by phoneme surprisal, are significantly stronger than (statistically null) effects of phoneme-by-phoneme lexical uncertainty, quantified by cohort entropy. In contrast, we find robust effects of both cohort entropy and phoneme surprisal during perception of connected speech, with a significant interaction between the contexts. This dissociation rules out models of word recognition in which phoneme surprisal and cohort entropy are common indicators of a uniform process, even though these closely related information-theoretic measures both arise from the probability distribution of wordforms consistent with the input. We propose that phoneme surprisal effects reflect automatic access of a lower level of representation of the auditory input (e.g., wordforms) while the occurrence of cohort entropy effects is task sensitive, driven by a competition process or a higher-level representation that is engaged late (or not at all) during the processing of single words.

The Binding Problem 2.0: Beyond Perceptual Features.

The "binding problem" has been a central question in vision science for some 30 years: When encoding multiple objects or maintaining them in working memory, how are we able to represent the correspondence between a specific feature and its corresponding object correctly? In this letter we argue that the boundaries of this research program in fact extend far beyond vision, and we call for coordinated pursuit across the broader cognitive science community of this central question for cognition, which we dub "Binding Problem 2.0".

A subject relative clause preference in a split-ergative language: ERP evidence from Georgian.

A fascinating descriptive property of human language processing whose explanation is still debated is that subject-gap relative clauses are easier to process than object-gap relative clauses, across a broad range of languages with different properties. However, recent work suggests that this generalization does not hold in Basque, an ergative language, and has motivated an alternative generalization in which the preference is for gaps in morphologically unmarked positions-subjects in nominative-accusative languages, and objects and intransitive subjects in ergative-absolutive languages. Here we examined whether this generalization extends to another ergative-absolutive language, Georgian. ERP and self-paced reading results show a large anterior negativity and slower reading times when a relative clause is disambiguated to an object relative vs a subject relative. These data thus suggest that in at least some ergative-absolutive languages, the classic descriptive generalization-that object relative clauses are more costly than subject relative clauses-still holds.

Electrophysiological hallmarks for event relations and event roles in working memory.

The ability to maintain events (i.e., interactions between/among objects) in working memory is crucial for our everyday cognition, yet the format of this representation is poorly understood. The current ERP study was designed to answer two questions: How is maintaining events (e.g., the tiger hit the lion) neurally different from maintaining item coordinations (e.g., the tiger and the lion)? That is, how is the event relation (present in events but not coordinations) represented? And how is the agent, or initiator of the event encoded differently from the patient, or receiver of the event during maintenance? We used a novel picture-sentence match-across-delay approach in which the working memory representation was "pinged" during the delay, replicated across two ERP experiments with Chinese and English materials. We found that maintenance of events elicited a long-lasting late sustained difference in posterior-occipital electrodes relative to non-events. This effect resembled the negative slow wave reported in previous studies of working memory, suggesting that the maintenance of events in working memory may impose a higher cost compared to coordinations. Although we did not observe significant ERP differences associated with pinging the agent vs. the patient during the delay, we did find that the ping appeared to dampen the ongoing sustained difference, suggesting a shift from sustained activity to activity silent mechanisms. These results suggest a new method by which ERPs can be used to elucidate the format of neural representation for events in working memory.

Parallel processing in speech perception with local and global representations of linguistic context.

Speech processing is highly incremental. It is widely accepted that human listeners continuously use the linguistic context to anticipate upcoming concepts, words, and phonemes. However, previous evidence supports two seemingly contradictory models of how a predictive context is integrated with the bottom-up sensory input: Classic psycholinguistic paradigms suggest a two-stage process, in which acoustic input initially leads to local, context-independent representations, which are then quickly integrated with contextual constraints. This contrasts with the view that the brain constructs a single coherent, unified interpretation of the input, which fully integrates available information across representational hierarchies, and thus uses contextual constraints to modulate even the earliest sensory representations. To distinguish these hypotheses, we tested magnetoencephalography responses to continuous narrative speech for signatures of local and unified predictive models. Results provide evidence that listeners employ both types of models in parallel. Two local context models uniquely predict some part of early neural responses, one based on sublexical phoneme sequences, and one based on the phonemes in the current word alone; at the same time, even early responses to phonemes also reflect a unified model that incorporates sentence-level constraints to predict upcoming phonemes. Neural source localization places the anatomical origins of the different predictive models in nonidentical parts of the superior temporal lobes bilaterally, with the right hemisphere showing a relative preference for more local models. These results suggest that speech processing recruits both local and unified predictive models in parallel, reconciling previous disparate findings. Parallel models might make the perceptual system more robust, facilitate processing of unexpected inputs, and serve a function in language acquisition.

Towards Understanding Sustained Neural Activity Across Syntactic Dependencies.

Sustained anterior negativities have been the focus of much neurolinguistics research concerned with the language-memory interface, but what neural computations do they actually reflect? During the comprehension of sentences with long-distance dependencies between elements (such as object wh-questions), prior event-related potential work has demonstrated sustained anterior negativities (SANs) across the dependency region. SANs have been traditionally interpreted as an index of working memory resources responsible for storing the first element (e.g., wh-phrase) until the second element (e.g., verb) is encountered and the two can be integrated. However, it is also known that humans pursue top-down approaches in processing long-distance dependencies-predicting units and structures before actually encountering them. This study tests the hypothesis that SANs are a more general neural index of syntactic prediction. Across three experiments, we evaluated SANs in traditional wh-dependency contrasts, but also in sentences in which subordinating adverbials (e.g., although) trigger a prediction for a second clause, compared to temporal adverbials (e.g., today) that do not. We find no SAN associated with subordinating adverbials, contra the syntactic prediction hypothesis. More surprisingly, we observe SANs across matrix questions but not embedded questions. Since both involved identical long-distance dependencies, these results are also inconsistent with the traditional syntactic working memory account of the SAN. We suggest that a more general hypothesis that sustained neural activity supports working memory can be maintained, however, if the sustained anterior negativity reflects working memory encoding at the non-linguistic discourse representation level, rather than at the sentence level.

Ratiometric imaging of extracellular pH in Streptococcus mutans biofilms exposed to different flow velocities and saliva film thicknesses.

Introduction: Fluid flow has a prominent influence on the metabolism of surface-attached biofilms. Dental biofilms are covered by a thin saliva film that flows at different rates in different locations under stimulated and unstimulated conditions. Methods:The present study employed pH ratiometry to study the impact of different flow velocities, saliva film thicknesses and saliva concentrations on microscale pH developments in Streptococcus mutans biofilms of different age. Results:While saliva flow at a velocity of 0.8 mm/min (unstimulated flow) had little impact on biofilm pH, stimulated flow (8 mm/min; 80 mm/min) affected vertical pH gradients in the biofilms and raised the average pH in 48-h biofilms, but not in 72-h and 168-h biofilms. The saliva film thickness had a strong impact on biofilm pH under both static and dynamic conditions. pH drops were significantly higher in biofilms exposed to a thin saliva film (≤ 50 µm) than a thick saliva film (> 50 µm). pH drops in the biofilms were also strongly dependent on the saliva concentration and thus the buffer capacity of the salivary medium. For 48-h and 72-h biofilms, but not for 168-h biofilms, pH drops in distinct microenvironments were more pronounced when the local biofilm thickness was high.

International Committee on Systematics of Prokaryotes: Subcommittee on the Taxonomy of Aerobic Bacteroidetes (formerly Flavobacterium and Cytophaga-like bacteria).

Minutes of the meeting: 15 November 2017 (Skype meeting).

fMRI evidence that left posterior temporal cortex contributes to N400 effects of predictability independent of congruity.

Previous electrophysiological work argues that predictability and semantic incongruity rapidly impact comprehension, as indicated by modulation of the N400 component between ~300 and 500 ms. An ongoing question is whether effects of predictability in fact reflect pre-activation in long-term memory as opposed to modulating the kind of integration processes triggered by incongruity. Using fMRI, we compared the impact of predictability and incongruity in adjective-noun phrases, in regions identified with lexical and phrasal localizer scans. We found that predictability impacted activity in left posterior middle temporal gyrus (pMTG), while incongruity impacted activity in left precentral gyrus. Together with parallel data from ERP, these data are consistent with the hypothesis that left pMTG activity is a key contributor to N400 effects of predictability and that the relevant mechanism is reduced activation of stored lexical representations. We tentatively suggest that the left precentral region may play a role in reanalysis when incongruity is encountered.

Error-Driven Retrieval in Agreement Attraction Rarely Leads to Misinterpretation.

Previous work on agreement computation in sentence comprehension motivates a model in which the parser predicts the verb's number and engages in retrieval of the agreement controller only when it detects a mismatch between the prediction and the bottom-up input. It is the error-driven second stage of this process that is prone to similarity-based interference and can result in the illusory licensing of a subject-verb number agreement violation in the presence of a structurally irrelevant noun matching the number marking on the verb ('The bed by the lamps were…'), giving rise to an effect known as 'agreement attraction'. Here we ask to what extent the error-driven retrieval process underlying the illusory licensing alters the structural and thematic representation of the sentence. We use a novel dual-task paradigm that combines self-paced reading with a speeded forced choice task to investigate whether agreement attraction leads comprehenders to erroneously interpret the attractor as the thematic subject, which would indicate structural reanalysis. Participants read sentence fragments ('The bed by the lamp/lamps was/were undoubtedly quite') and completed the sentences by choosing between two adjectives ('comfortable'/'bright') which were either compatible with the subject's head noun or with the attractor. We found the expected agreement attraction profile in the self-paced reading data but the interpretive error occurs on only a small subset of attraction trials, suggesting that in agreement attraction agreement checking rarely matches the thematic relation. We propose that illusory licensing of an agreement violation often reflects a low-level rechecking process that is only concerned with number and does not have an impact on the structural representation of the sentence. Interestingly, this suggests that error-driven repair processes can result in a globally inconsistent final sentence representation with a persistent mismatch between the subject and the verb.

World Workshop on Oral Medicine VII: Targeting the oral microbiome Part 2: Current knowledge on malignant and potentially malignant oral disorders.

OBJECTIVE: The World Workshop on Oral Medicine VII chose the oral microbiome as a focus area. Part 1 presents the methodological state of the science for oral microbiome studies. Part 2 was guided by the question: What is currently known about the microbiome associated with oral squamous cell carcinoma and potentially malignant disorders of the oral mucosa? MATERIALS AND METHODS: A scoping review methodology was followed to identify and analyse relevant studies on the composition and potential functions of the oral microbiota using high-throughput sequencing techniques. The authors performed searches in PubMed and EMBASE. After removal of duplicates, a total of 239 potentially studies were identified. RESULTS: Twenty-three studies on oral squamous cell carcinoma, two on oral leukoplakia and four on oral lichen planus were included with substantial differences in diagnostic criteria, sample type, region sequenced and sequencing method utilised. The majority of studies focused on bacterial identification and recorded statistically significant differences in the oral microbiota associated with health and disease. However, even when comparing studies of similar methodology, the microbial differences between health and disease varied considerably. No consensus on the composition of the microbiomes associated with these conditions on genus and species level could be obtained. Six studies on oral squamous cell carcinoma had included in silico predicted microbial functions (genes and/or pathways) and found some similarities between the studies. CONCLUSIONS: Attempts to reveal the microbiome associated with oral mucosal diseases are still in its infancy, and the studies demonstrate significant clinical and methodological heterogeneity across disease categories. The immense richness and diversity of the microbiota clearly illustrate that there is a need for additional methodologically comparable studies utilising deep sequencing approaches in significant cohorts of subjects together with functional analyses. Our hope is that following the recipe as outlined in our preceding companion paper, that is Part 1, will enhance achieving this in the future and elucidate the role of the oral microbiome in oral squamous cell carcinoma and potentially malignant disorders of the oral mucosa.

World Workshop on Oral Medicine VII: Targeting the microbiome for oral medicine specialists-Part 1. A methodological guide.

Advances in high-throughput sequencing technologies have allowed for a rapid increase in knowledge about the human microbiome in both healthy and diseased states, which is expected to increase our understanding of multifactorial diseases. The World Workshop on Oral Medicine VII chose the microbiome as one of its topics of focus. Part 1 of this review provides updated knowledge in the field of microbiome research, describes the advantages and disadvantages of currently available sequencing technologies, and proposes a seven-step "recipe" for designing and performing studies that is supported by contemporary evidence. Part 2 of this review in a companion paper discusses the results of high-throughput sequencing studies published to date on the microbiota associated with oral mucosal diseases. The goal of this collective enterprise is to encourage more oral medicine specialists to become engaged in multidisciplinary collaborations to investigate the role of the microbiome in relation to oral diseases, which could potentially lead to enhanced diagnosis, risk assessment and treatment of these patients.

Same words, different structures: An fMRI investigation of argument relations and the angular gyrus.

In fMRI, increased activation for combinatorial syntactic and semantic processing is typically observed in a set of left hemisphere brain areas: the angular gyrus (AG), the anterior temporal lobe (ATL), the posterior superior temporal sulcus (pSTS), and the inferior frontal gyrus (IFG). Recent work has suggested that semantic combination is supported by the ATL and the AG, with a division of labor in which AG is involved in event concepts and ATL is involved in encoding conceptual features of entities and/or more general forms of semantic combination. The current fMRI study was designed to refine hypotheses about the angular gyrus processes in question. In particular, we ask whether the AG supports the computation of argument structure (a linguistic notion that depends on a verb taking other phrases as arguments) or the computation of event concepts more broadly. To distinguish these possibilities we used a novel, lexically-matched contrast: noun phrases (NP) (the frightened boy) and verb phrases (VP) (frightened the boy), where VPs contained argument structure, denoting an event and assigning a thematic role to its argument, and NPs did not, denoting only a semantically enriched entity. Results showed that while many regions showed increased activity for NPs and VPs relative to unstructured word lists (AG, ATL, pSTS, anterior IFG), replicating evidence of their involvement in combinatorial processing, neither AG or ATL showed differences in activation between the VP and NP conditions. These results suggest that increased AG activity does not reflect the computation of argument structure per se, but are compatible with a view in which the AG represents event information denoted by words such as frightened independent of their grammatical context. By contrast, pSTS and posterior IFG did show increased activation for the VPs relative to NPs. We suggest that these effects may reflect differences in syntactic processing and working memory engaged by different structural relations.

Neural evidence for Bayesian trial-by-trial adaptation on the N400 during semantic priming.

When semantic information is activated by a context prior to new bottom-up input (i.e. when a word is predicted), semantic processing of that incoming word is typically facilitated, attenuating the amplitude of the N400 event related potential (ERP) - a direct neural measure of semantic processing. N400 modulation is observed even when the context is a single semantically related "prime" word. This so-called "N400 semantic priming effect" is sensitive to the probability of encountering a related prime-target pair within an experimental block, suggesting that participants may be adapting the strength of their predictions to the predictive validity of their broader experimental environment. We formalize this adaptation using a Bayesian learning model that estimates and updates the probability of encountering a related versus an unrelated prime-target pair on each successive trial. We found that our model's trial-by-trial estimates of target word probability accounted for significant variance in trial-by-trial N400 amplitude. These findings suggest that Bayesian principles contribute to how comprehenders adapt their semantic predictions to the statistical structure of their broader environment, with implications for the functional significance of the N400 component and the predictive nature of language processing.

Multimodal neuroimaging evidence for looser lexico-semantic networks in schizophrenia:Evidence from masked indirect semantic priming.

It has been hypothesized that schizophrenia is characterized by overly broad automatic activity within lexico-semantic networks. We used two complementary neuroimaging techniques, Magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI), in combination with a highly automatic indirect semantic priming paradigm, to spatiotemporally localize this abnormality in the brain. Eighteen people with schizophrenia and 20 demographically-matched control participants viewed target words ("bell") preceded by directly related ("church"), indirectly related ("priest"), or unrelated ("hammer") prime words in MEG and fMRI sessions. To minimize top-down processing, the prime was masked, the target appeared only 140 ms after prime onset, and participants simply monitored for words within a particular semantic category that appeared in filler trials. Both techniques revealed a significantly larger automatic indirect priming effect in people with schizophrenia than in control participants. MEG temporally localized this enhanced effect to the N400 time window (300-500 ms) - the critical stage of accessing meaning from words. fMRI spatially localized the effect to the left temporal fusiform cortex, which plays a role in mapping of orthographic word-form on to meaning. There was no evidence of an enhanced automatic direct semantic priming effect in the schizophrenia group. These findings provide converging neural evidence for abnormally broad highly automatic lexico-semantic activity in schizophrenia. We argue that, rather than arising from an unconstrained spread of automatic activation across semantic memory, this broader automatic lexico-semantic activity stems from looser mappings between the form and meaning of words.

The temporal dynamics of structure and content in sentence comprehension: Evidence from fMRI-constrained MEG.

Humans have a striking capacity to combine words into sentences that express new meanings. Previous research has identified key brain regions involved in this capacity, but little is known about the time course of activity in these regions, as hemodynamic methods such as fMRI provide little insight into temporal dynamics of neural activation. We performed an MEG experiment to elucidate the temporal dynamics of structure and content processing within four brain regions implicated by fMRI data from the same experiment: the temporo-parietal junction (TPJ), the posterior temporal lobe (PTL), the anterior temporal lobe (ATL), and the anterior inferior frontal gyrus (IFG). The TPJ showed increased activity for both structure and content near the end of the sentence, consistent with a role in incremental interpretation of event semantics. The PTL, a region not often associated with core aspects of syntax, showed a strong early effect of structure, consistent with predictive parsing models, and both structural and semantic context effects on function words. These results provide converging evidence that the PTL plays an important role in lexicalized syntactic processing. The ATL and IFG, regions traditionally associated with syntax, showed minimal effects of sentence structure. The ATL, PTL and IFG all showed effects of semantic content: increased activation for real words relative to nonwords. Our fMRI-guided MEG investigation therefore helps identify syntactic and semantic aspects of sentence comprehension in the brain in both spatial and temporal dimensions.

The role of the IFG and pSTS in syntactic prediction: Evidence from a parametric study of hierarchical structure in fMRI.

Sentences encode hierarchical structural relations among words. Several neuroimaging experiments aiming to localize combinatory operations responsible for creating this structure during sentence comprehension have contrasted short, simple phrases and sentences to unstructured controls. Some of these experiments have revealed activation in the left inferior frontal gyrus (IFG) and posterior superior temporal sulcus (pSTS), associating these regions with basic syntactic combination. However, the wide variability of these effects across studies raises questions about this interpretation. In an fMRI experiment, we provide support for an alternative hypothesis: these regions underlie top-down syntactic predictions that facilitate sentence processing but are not necessary for building syntactic structure. We presented stimuli with three levels of structure: unstructured lists, two-word phrases, and simple, short sentences; and two levels of content: natural stimuli with real words and stimuli with open-class items replaced with pseudowords (jabberwocky). While both the phrase and sentence conditions engaged syntactic combination, our experiment only encouraged syntactic prediction in the sentence condition. We found increased activity for both natural and jabberwocky sentences in the left IFG (pars triangularis and pars orbitalis) and pSTS relative to unstructured word lists and two-word phrases, but we did not find any such effects for two-word phrases relative to unstructured word lists in these areas. Our results are most consistent with the hypothesis that increased activity in IFG and pSTS for basic contrasts of structure reflects syntactic prediction. The pars opercularis of the IFG showed a response profile consistent with verbal working memory. We found incremental effects of structure in the anterior temporal lobe (ATL), and increased activation only for sentences in the angular gyrus (AG)/temporal-parietal junction (TPJ) - both regions showed these effects for stimuli with all real words. These findings support a role for the ATL in semantic combination and the AG/TPJ in thematic processing.

Coreference and antecedent representation across languages.

Previous studies have shown that speakers of languages such as German, Spanish, and French reactivate the syntactic gender of the antecedent of a pronoun to license gender agreement. As syntactic gender is assumed to be stored in the lexicon, this has motivated the claim that pronouns in these languages reactivate the lexical entry of their antecedent noun. In contrast, in languages without syntactic gender such as English, lexical retrieval might be unnecessary. We used eye-tracking while reading to examine whether antecedent retrieval involves rapid semantic and phonological reactivation. We compared German and English. In German, we found early sensitivity to the semantic but not to the phonological features of the pronoun's antecedent. In English, readers did not immediately show either semantic or phonological effects specific to coreference. We propose that early semantic facilitation arises due to syntactic gender reactivation, and that antecedent retrieval varies cross-linguistically depending on the type of information relevant to the grammar of each language. (PsycINFO Database Record