Abstract. The paper reports findings derived from three experiments examining syntactic and morphosyntactic processing in individuals with agrammatic and logopenic variants of primary progressive aphasia (PPA-G and PPA-L, respectively) and strokeinduced agrammatic and anomic aphasia (StrAg and StrAn, respectively). We examined comprehension and production of canonical and noncanonical sentence structures and production of tensed and nontensed verb forms using constrained tasks in experiments 1 and 2, using the Northwestern Assessment of Verbs and Sentences (NAVS [57]) and the Northwestern Assessment of Verb Inflection (NAVI, Thompson and Lee, experimental version) test batteries, respectively. Experiment 3 examined free narrative samples, focusing on syntactic and morphosyntactic measures, i.e. production of grammatical sentences, noun to verb ratio, open-class to closed-class word production ratio, and the production of correctly inflected verbs. Results indicate that the two agrammatic groups (i.e., PPA-G and StrAg) pattern alike on syntactic and morphosyntactic measures, showing more impaired noncanonical compared to canonical sentence comprehension and production and greater difficulties producing tensed compared to nontensed verb forms. Their spontaneous speech also contained significantly fewer grammatical sentences and correctly inflected verbs, and they produced a greater proportion of nouns compared to verbs, than healthy speakers. In contrast, PPA-L and StrAn individuals did not display these deficits, and performed significantly better than the agrammatic groups on these measures. The findings suggest that agrammatism, whether induced by degenerative disease or stroke, is associated with characteristic deficits in syntactic and morphosyntactic processing. We therefore recommend that linguistically sophisticated tests and narrative analysis procedures be used to systematically evaluate the linguistic ability of individuals with PPA, contributing to our understanding of the language impairments of different PPA variants.

Previous research has shown that comprehension of complex sentences involving wh-movement (e.g., object-relative clauses) elicits activation in the left inferior frontal gyrus (IFG) and left posterior temporal cortex. However, relatively little is known about the neural correlates of processing passive sentences, which differ from other complex sentences in terms of representation (i.e., noun phrase (NP)-movement) and processing (i.e., the time course of syntactic reanalysis). In the present study, 27 adults (14 younger and 13 older) listened to passive and active sentences and performed a sentence-picture verification task using functional Magnetic Resonance Imaging (fMRI). Passive sentences, relative to active sentences, elicited greater activation in bilateral IFG and left temporo-occipital regions. Participant age did not significantly affect patterns of activation. Consistent with previous research, activation in left temporo-occipital cortex likely reflects thematic reanalysis processes, whereas, activation in the left IFG supports processing of complex syntax (i.e., NP-movement). Right IFG activation may reflect syntactic reanalysis processing demands associated with the sentence-picture verification task.

Introduction-Neuroimaging and lesion studies indicate a left hemisphere network for verb and verb argument structure processing, involving both frontal and temporoparietal brain regions. Although their verb comprehension is generally unimpaired, it is well known that individuals with agrammatic aphasia often present with verb production deficits, characterized by an argument structure complexity hierarchy, indicating faulty access to argument structure representations for production and integration into syntactic contexts. Recovery of verb processing in agrammatism, however, has received little attention and no studies have examined the neural mechanisms associated with improved verb and argument structure processing. In the present study we trained agrammatic individuals on verbs with complex argument structure in sentence contexts and examined generalization to verbs with less complex argument structure. The neural substrates of improved verb production were examined using functional magnetic resonance imaging (fMRI).Methods-Eight individuals with chronic agrammatic aphasia participated in the study (four experimental and four control participants). Production of three-argument verbs in active sentences was trained using a sentence generation task emphasizing the verb's argument structure and the thematic roles of sentential noun phrases. Before and after training, production of trained and untrained verbs was tested in naming and sentence production and fMRI scans were obtained, using an action naming task.Results-Significant pre-to post-training improvement in trained and untrained (one-and twoargument) verbs was found for treated, but not control, participants, with between-group differences found for verb naming, production of verbs in sentences, and production of argument structure. fMRI activation derived from post-treatment compared to pre-treatment scans revealed upregulation in cortical regions implicated for verb and argument structure processing in healthy controls. Conclusions-Training verb deficits emphasizing argument structure and thematic role mapping is effective for improving verb and sentence production and results in recruitment of neural networks engaged for verb and argument structure processing in healthy individuals.

During sentence processing, comprehenders form expectations regarding upcoming material, and may even predict a specific word. Previous event-related potential (ERP) studies have shown that disconfirmed predictions elicit a post-N400-positivity (PNP) with two distinct distributions. A frontal-PNP (f-PNP) is elicited when an unexpected but congruent word appears instead of a highly predictable word, whereas an anomalous word elicits a posterior-PNP. The current study tested the hypothesis that during the processing of a sentence, the predicted word is inhibited to enable the integration of unexpected but congruent material, and that this inhibitory process is reflected in the f-PNP component. In contrast, anomalous continuations, which are not compatible with the preceding context, do not induce inhibition. Experiment 1 used cross-modal lexical priming to test inhibition patterns of predicted words, demonstrating inhibition when integration of a congruent-unexpected word was needed, but not when an anomaly was encountered. Experiment 2 showed that the inhibition observed in Experiment 1 is specific to the predicted word and does not stem from competition between two congruent continuations. In Experiment 3 we recorded ERPs using the same materials, and found that the f-PNP component is elicited under the same conditions giving rise to behavioral inhibition, and that the two are correlated, thus providing preliminary support for the hypothesis that this component reflects an inhibitory process. (PsycINFO Database Record

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It was recently proposed that lexical prediction in sentence context encompasses two qualitatively distinct prediction mechanisms: "preactivation," namely activating representations stored in long-term memory, and "preupdating," namely updating the sentence's representation, built online in working memory (WM), to include the predicted content [Lau, E. F., Holcomb, P. J., & Kuperberg, G. R. Dissociating N400 effects of prediction from association in single-word contexts. Journal of Cognitive Neuroscience, 25, 484-502, 2013]. The current study sought to find evidence for preupdating and test the influence of individual differences in WM capacity on the tendency to engage in this process. Participants read strongly and weakly constraining sentences. ERPs were measured on the predictable noun as well as on the preceding verb, where the prediction is generated. Increased P600 amplitude was observed at the verb in the strongly constraining sentences, reflecting integration of the predicted upcoming argument, thus providing evidence for preupdating. This effect was greater for participants with higher WM capacity, indicating that the tendency to engage in preupdating is highly affected by WM capacity. The opposite effect was observed at the noun, that is, for participants with higher WM span, a greater decrease in P600 amplitude in the strongly constraining sentences was observed, indicating that the integration of a preupdated word was easier. We discuss these results in light of previous literature and propose a plausible architecture to account for the interplay between preactivation and preupdating, mediating the influence of factors such as WM capacity.

Verbs are central to sentence processing, as they encode argument structure (AS) information, i.e., information about the syntax and interpretation of the phrases accompanying them. The behavioral and neural correlates of AS processing have primarily been investigated in sentence-level tasks, requiring both verb processing and verb-argument integration. In the current functional magnetic resonance imaging (fMRI) study, we investigated AS processing using a lexical decision task requiring only verb processing. We examined three aspects of AS complexity: number of thematic roles, number of thematic options, and mapping (non)canonicity (unaccusative vs. unergative and transitive verbs). Increased number of thematic roles elicited greater activation in the left posterior perisylvian regions claimed to support access to stored AS representations. However, the number of thematic options had no neural effects. Further, unaccusative verbs elicited longer response times and increased activation in the left inferior frontal gyrus, reflecting the processing cost of unaccusative verbs and, more generally, supporting the role of the IFG in noncanonical argument mapping.

Naming and word-retrieval deficits, which are common characteristics of primary progressive aphasia (PPA), differentially affect production across word classes (e.g., nouns, verbs) in some patients. Individuals with the agrammatic variant (PPA-G) often show greater difficulty producing verbs whereas those with the semantic variant (PPA-S) show greater noun deficits and those with logopenic PPA (PPA-L) evince no clear-cut differences in production of the two word classes. To determine the source of these production patterns, the present study examined word-finding pauses as conditioned by lexical variables (i.e., word class, frequency, length) in narrative speech samples of individuals with PPA-S (n=12), PPA-G (n=12), PPA-L (n=11), and cognitively healthy controls (n=12). We also examined the relation between pause distribution and cortical atrophy (i.e., cortical thickness) in nine left hemisphere regions of interest (ROIs) linked to word production. Results showed higher overall pause rates for PPA compared to unimpaired controls; however, greater naming severity was not associated with increased pause rate. Across all groups, more pauses were produced before lower vs. higher frequency words, with no independent effects of word length after controlling for frequency. With regard to word class, the PPA-L group showed a higher rate of pauses prior to production of nouns compared to verbs, consistent with noun-retrieval deficits arising at the lemma level of word production. Those with PPA-G and PPA-S, like controls, produced similar pause rates across word classes; however, lexical simplification (i.e., production of higher-frequency and/or shorter words) was evident in the more-impaired word class: nouns for PPA-S and verbs for PPA-G. These patterns are consistent with conceptual and/or lemma-level impairments for PPA-S, predominantly affecting objects/nouns, and a lemma-level verb-retrieval deficit for PPA-G, with a concomitant impairment in phonological encoding and articulation affecting overall pause rates. The greater tendency to pause before nouns was correlated with atrophy in the left precentral gyrus, inferior frontal gyrus and inferior parietal lobule, whereas the greater tendency to pause before less frequent and longer words was associated with atrophy in left precentral and inferior parietal regions.