Prolegomena to a neurocomputational architecture for human grammatical encoding and decoding

The study develops a neurocomputational architecture for grammatical processing in language production and language comprehension (grammatical encoding and decoding, respectively). It seeks to answer two questions. First, how is online syntactic structure formation of the complexity required by natural-language grammars possible in a fixed, preexisting neural network without the need for online creation of new connections or associations? Second, is it realistic to assume that the seemingly disparate instantiations of syntactic structure formation in grammatical encoding and grammatical decoding can run on the same neural infrastructure? This issue is prompted by accumulating experimental evidence for the hypothesis that the mechanisms for grammatical decoding overlap with those for grammatical encoding to a considerable extent, thus inviting the hypothesis of a single “grammatical coder.” The paper answers both questions by providing the blueprint for a syntactic structure formation mechanism that is entirely based on prewired circuitry (except for referential processing, which relies on the rapid learning capacity of the hippocampal complex), and can subserve decoding as well as encoding tasks. The model builds on the “Unification Space” model of syntactic parsing developed by Vosse & Kempen (2000, 2008, 2009). The design includes a neurocomputational mechanism for the treatment of an important class of grammatical movement phenomena

The role of memory and language ability in children’s production of two-clause sentences containing before and after

We assessed 3- to 6-year-olds’ production of two-clause sentences linked by before or after. In two experiments, children viewed an animated sequence of two actions, and were asked to describe the order of events in specific target sentence structures. We manipulated whether the target sentence structure matched the chronological order of events, for example: ‘He finished his homework, before he played in the garden’ (chronological order) or not, for example: ‘Before he played in the garden, he finished his homework’ (reverse order). Children produced fewer accurate target sentences when the presentation order of the two clauses did not match the chronological order of events, specifically for target sentences linked by after. Independent measures of vocabulary and memory were both related to performance, but vocabulary was the stronger predictor. We conclude that developmental improvements in children’s ability to produce two-clause sentences linked by a sequential temporal connective is driven primarily by language ability, rather than memory capacity per se. The work also highlights the advantages of using both sentence repetition (Experiment 1) and blocked elicited production (Experiment 2) paradigms to elicit sentence production in young children

Investigating the language of time: Evaluating the use and comprehension of before and after

Before-initial sentences are thought to be more difficult to comprehend than after-initial sentences because they structurally mismatch the temporal order of real-world events (Münte et al., 1998). Although event knowledge is known to affect how people understand before/after-initial sentences, little is known about the role of language knowledge in comprehending these sentences. A corpus analysis of before/after-initial sentences revealed that before typically is paired with a pronoun (Before he…) whereas after is paired with verb-ing (After leaving…). Participants\u27 eyes were tracked while they read Before/After-pronoun/verbing sentences. Reading times did not match the corpus statistics. The beginning of verbing-sentences was read faster than pronoun-sentences regardless of whether they began with before or after. Reading times were similar for before- and after-initial sentences. The results suggest that when people read natural sounding sentences, they do not have difficulty with sentences in which the order of events mismatches real world temporal order

Linking sentence production and comprehension: The neural mechanisms underlying production and comprehension control processes

This thesis investigated the relationship between sentence production and comprehension. A combination of behavioural and neuroimaging techniques were used to examine the extent to which sentence production and comprehension engage common or distinct mechanisms, with specific focus on the processes engaged by semantic/syntactic competition. Behavioural studies in Chapter 2 indicated that high-competition cases were more difficult to understand and produce than low-competition cases, and that difficulty varied as a function of the number of alternative associations entertained during performance in both tasks. In Chapter 3, an fMRI study indicated that production and comprehension shared a common competition mechanism within left inferior frontal gyrus (LIFG). However, they engage distinctive networks that interact with LIFG, with production eliciting a larger network including areas involved in sentence planning and memory retrieval. Further asymmetries across tasks were revealed in Chapter 4, in which behavioural results and neural networks were compared across adults and adolescents. This study also demonstrated the occurrence of shifts in the neural networks involved in competition resolution throughout development, thereby providing a strong link between poor behavioural performance and the underdevelopment of pre-frontal inhibitory mechanisms in adolescents. Chapter 5 used an improved experimental paradigm from that in Chapters 3 and 4. The results showed that production elicits more activity than comprehension in the dorsal language route thus confirming the engagement of task-specific control processes. Interestingly, this study also revealed a common area of LIFG involved in both tasks, but also differences within LIFG, suggesting the possibility of task-specific circuitry. Together, the findings suggest that production and comprehension share fronto-temporal areas that store and manage abstract linguistic associations between words and structures. However, they differ in the manner in which linguistic information is used, as is evident by the recruitment of distinct networks. Implications for models of language processing are discussed

Why young children fail to understand ‘before’ and ‘after’

The goals of the thesis were to identify the development of 3- to 7-year-old children’s comprehension and production of two contrasting temporal connectives - before and after - that signal the order of events in two-clause sentences, and to establish the reasons for difficulties with these linguistic devices. Chapter 1 reviews the literature that is considered relevant to the experimental work. In the experimental work (Chapters 2 to 4), children’s comprehension and production of two-clause sentences containing before and after was examined in separate groups of children aged 3 to 7 years. The sentence structures differed in their memory and also language demands. Independent measures of memory and language were related to performance. The design enabled a contrast of traditional memory capacity accounts (e.g., Just & Carpenter, 1992) versus more recent language-based accounts (e.g., Van Dyke, Johns, & Kukona, 2014) of why working memory explains variance in the processing of complex sentences. A capacity account predicts a direct relation between memory and sentence processing: specifically, that some sentence structures are more difficult to process than others because they require more information to be held in working memory than others. Alternatively, a language-based account proposes an indirect relation between memory and sentence processing, such that good language skills modulate the influence of memory on sentence processing, by influencing the accurate representation of information in verbal working memory. Experiment 1 (Chapter 2) was a touch-screen comprehension paradigm. Children listened to two-clause sentences linked by a temporal connective, before or after, while viewing animations of the actions in each clause. After each sentence, they were asked to select the event that happened first to assess their understanding of the temporal connective. The pattern of results suggested that the memory demands of specific sentence structures limited children’s comprehension of sentences containing temporal connectives, supporting a memory capacity account. Experiment 2 (Chapter 3) further investigated comprehension of these sentences focusing on how memory and language influence the ease of processing. Children were trained to make speeded responses to the sentence structures investigated in Experiment 1. The findings support Experiment 1: memory capacity best predicted comprehension of these sentence structures. Experiments 3 and 4 (Chapter 4) examined production of the same sentence types. In two experiments (elicited production with blocked conditions, and sentence repetition), separate groups of children viewed an animated sequence of two actions, and were asked to describe the order of events. Instructions and practice trials were used to model the target sentence structures. In contrast to the comprehension experiments (Experiments 1 and 2), this work showed that children’s individual differences in the production of two-clause sentences linked by before or after were related to variability in language skills, rather than poor memory capacity. In Chapter 5, I conclude that Experiments 1-4 reveal a differential influence of working memory and language on children’s comprehension and production of two-clause sentences containing before and after. I argue that the existing theoretical accounts of the influence of memory and language on sentence processing (e.g., Just & Carpenter, 1992; Van Dyke et al., 2014) require much more detailed investigation within the sentence structures examined here, and across other complex sentences that are also considered to differ in their memory and language demands. I present several suggestions as to how this might be accomplished in future work

Neural basis of linearization in speech production

An initial stage of speech production is conceptual planning, where a speaker determines which information to convey first (the linearization problem). This fMRI study investigated the linearization process during the production of "before" and "after" sentences. In "after" sentences, a series of events is expressed in the order of event occurrence. In "before" sentences, however, the order of event mention is achieved by reversing the chronological order. We suggested that the linearization process may be supported by a neural network connecting the leftmiddle temporal gyrus (MTG) with the medial superior frontal gyrus, left middle frontal gyrus, and left angular gyrus/inferior parietal gyrus. Within this network, regions were more activated and interregional interactions were strongly enhanced for producing "before" than "after" sentences. The left MTG was also functionally connected with the left orbital inferior frontal gyrus, contributing to the retrieval of necessary world knowledge and linguistic knowledge. Connectivity between these two regions was not different between conditions