The Meeting Point: Where Language Production and Working Memory Share Resources.

The interaction between working memory and language processing is widely discussed in cognitive research. However, those studies often explore the relationship between language comprehension and working memory (WM). The role of WM is rarely considered in language production, despite some evidence suggesting a relationship between the two cognitive systems. This study attempts to fill that gap by using a complex span task during language production. We make our predictions based on the reorganization of elementary functions neurocognitive model, a usage based theory about grammatical status, and language production models. In accordance with these theories, we expect an overlap between language production and WM at one or more levels of language planning. Our results show that WM is involved at the phonological encoding level of language production and that adding WM load facilitates language production, which leads us to suggest that an extra task-specific storage is being created while the task is performed.

Prepositions and pronouns in connected discourse of individuals with aphasia.

The lexical-grammatical divide has been a widely addressed topic in aphasia. Speech parts are generally classified as either belonging to a lexical or a grammatical category based on the frequency of acquisition of new members in their paradigms (open vs. closed classes), thus neglecting heterogeneity within categories. Such an approach has led to contradictory findings. First, prepositions form closed classes, but are classically taken as lexical items. Pronouns, also belonging to a closed class, are analyzed as grammatical elements. Second, both within the group of prepositions and pronouns, forms with different syntactic and semantic properties co-exist. Following the theoretical notions granted by a usage-based theory of grammar, the ProGram theory, and taking focalizability as the classification criteria, we hypothesize that individuals with non-fluent aphasias will experience more severe problems with grammatical prepositions and pronouns, given that these elements are secondary and dependent, whereas informants in the fluent group will experience more severe trouble with lexical forms, potentially primary and independent. We focused on the performance of nine Spanish-speaking individuals with aphasia from the Rosell (2005) corpus. Samples of 300 words were transcribed and analyzed. As predicted, grammatical prepositions were found to be more severely compromised in the speech output of individuals with deficits of motor predominance, whereas lexical prepositions are more severely affected in individuals with deficits of sensory predominance. Although less conclusively, the same tendency holds in the case of pronouns. Our results, consistent with previous findings, confirm the heterogeneity of prepositions and pronouns, which should no longer be analyzed en bloc.

Contrasting Grammatical and Lexical Determiners.

This paper investigates the difference between the production of grammatical determiners and lexical determiners in the production of adjective-noun phrases (NPs) in Danish. Models of sentence processing (Garrett in Psychology of learning and motivation, Academic press, New York, pp 133-177, 1975; Bock in J Mem Lang 26(2):119-137, 1987) suggest that the phonological encoding stage of grammatical items can only be specified once lexical items have been phonologically encoded. In their usage-based linguistic theory of the grammar-lexicon distinction, Boye and Harder (Lang 88(1):1-44, 2012) propose that this later encoding of grammatical elements is motivated by two specific features of grammatical elements. The first feature, dependence, is that grammatical items (morphemes, words, constructions) cannot be produced in isolation, but are always dependent on a lexical host item. This feature entails a more complex processing which might lead to longer reaction times when comparing the production of NPs with a grammatical determiner to a lexical one. Additionally, a more complex processing might lead to a lower accuracy rate for the grammatical condition relative to the lexical one. The second feature, low prominence, is that grammatical items code background information and therefore cannot convey the main point of a linguistic message. Less focus on grammatical elements might lead to a lower accuracy rate for the production of grammatical elements relative to lexical ones. Those predictions were tested in a task comparing the production of Danish grammatical determiners (indefinite articles) with the production of lexical ones (numerals, which are homonymous with the articles except for a stress difference) in similar contexts. Group-based analyses were performed in order to take inter-individual differences into account. The results show that the two features as proposed by Boye and Harder (2012) are only revealed for the fastest speakers group but not the slower ones.

Anterior and Posterior Left Inferior Frontal Gyrus Contribute to the Implementation of Grammatical Determiners During Language Production.

The left inferior frontal gyrus (IFG) is a key region for language comprehension and production. Previous studies point to a preferential involvement of left anterior IFG (aIFG) in lexical and semantic processes, while the posterior IFG (pIFG) has been implicated in supporting syntactic and phonological processes. Here we used focal neuronavigated transcranial magnetic stimulation (TMS) to probe the functional involvement of left IFG in lexical and grammatical processing at the sentence level. We applied 10 Hz TMS effective or sham bursts to left aIFG and pIFG, while healthy volunteers performed an adjective-noun production task contrasting grammatical and lexical determiners. For each trial, we measured the time from the stimulus onset to the moment of articulation (response time) and the time from articulation onset to the end of articulation (duration). Focal TMS of IFG generally delayed response times. The TMS-induced delay in response times was relatively stronger for the grammatical condition compared to the lexical condition, when TMS targeted aIFG. Articulation of the determiner was generally shorter in trials presenting grammatical determiners relative to lexical determiners. The shorter articulation time for grammar determiners was facilitated by effective TMS to pIFG. Together, the effects of TMS on task performance provide novel evidence for a joint involvement of anterior and posterior parts of left IFG in implementing grammatical determiners during language production, suggesting an involvement of aIFG in the initiation and pIFG in the production of grammatically appropriate verbal responses at the sentence level.

Planning and production of grammatical and lexical verbs in multi-word messages.

Grammatical words represent the part of grammar that can be most directly contrasted with the lexicon. Aphasiological studies, linguistic theories and psycholinguistic studies suggest that their processing is operated at different stages in speech production. Models of sentence production propose that at the formulation stage, lexical words are processed at the functional level while grammatical words are processed at a later positional level. In this study we consider proposals made by linguistic theories and psycholinguistic models to derive two predictions for the processing of grammatical words compared to lexical words. First, based on the assumption that grammatical words are less crucial for communication and therefore paid less attention to, it is predicted that they show shorter articulation times and/or higher error rates than lexical words. Second, based on the assumption that grammatical words differ from lexical words in being dependent on a lexical host, it is hypothesized that the retrieval of a grammatical word has to be put on hold until its lexical host is available, and it is predicted that this is reflected in longer reaction times (RTs) for grammatical compared to lexical words. We investigated these predictions by comparing fully homonymous sentences with only a difference in verb status (grammatical vs. lexical) elicited by a specific context. We measured RTs, duration and accuracy rate. No difference in duration was observed. Longer RTs and a lower accuracy rate for grammatical words were reported, successfully reflecting grammatical word properties as defined by linguistic theories and psycholinguistic models. Importantly, this study provides insight into the span of encoding and grammatical encoding processes in speech production.