Experience-dependent brain development as a key to understanding the language system

An influential view of the nature of the language system is that of an evolved biological system in which a set of rules is combined with a lexicon that contains the words of the language together with a representation of their context. Alternative views, usually based on connectionist modeling, attempt to explain the structure of language on the basis of complex associative processes. Here I put forward a third view that stresses experience-dependent structural development of the brain circuits supporting language as a core principle of the organization of the language system. On this view, embodied in a recent neuroconstructivist neural network of past tense development and processing, initial domain-general predispositions enable the development of functionally specialized brain structures through interactions between experience-dependent brain development and statistical learning in a structured environment. Together, these processes shape a biological adult language system that appears to separate into distinct mechanism for processing rules and exceptions, whereas in reality those subsystems co-develop and interact closely. This view puts experience-dependent brain development in response to a specific language environment at the heart of understanding not only language development but adult language processing as well

The past tense inflection project (PTIP): speeded past tense inflections, imageability ratings, and past tense consistency measures for 2,200 verbs

Abstract The processes involved in past tense verb generation have been central to models of inflectional morphology. However, the empirical support for such models has often been based on studies of accuracy in past tense verb formation on a relatively small set of items. We present the first largescale study of past tense inflection (the Past Tense Inflection Project, or PTIP) that affords response time, accuracy, and error analyses in the generation of the past tense form from the present tense form for over 2,000 verbs. In addition to standard lexical variables (such as word frequency, length, and orthographic and phonological neighborhood), we have also developed new measures of past tense neighborhood consistency and verb imageability for these stimuli, and via regression analyses we demonstrate the utility of these new measures in predicting past tense verb generation. The PTIP can be used to further evaluate existing models, to provide well controlled stimuli for new studies, and to uncover novel theoretical principles in past tense morphology. Keywords Verb processing . Megastudy . Past tense inflection . Item-level variance . Verb consistency . Verb imageability A long-standing question in language acquisition and inflectional morphology is how individuals produce the past tense form of a verb. Past tense inflection (PTI), like spelling-to-sound conversion in English, is quasiregular, meaning that a set of generally applicable descriptive rules are useful for most verbs (e.g., add -ed to the stem form), but there are also some irregular forms (e.g., dodid) and subregularities (as in the eep-ept past tense family: sleep-slept, weep-wept, keep-kept, etc.). Indeed, past tense inflection has been a central focus of the debate between parallel distributed models Although there has been extensive theoretical work in the area of past tense verb generation, experimental work examining response times (RTs) has been relatively limited. For example, in the stem inflection task, participants are asked to produce the past tense (real or hypothetical) of a target verb or novel nonword (e.g., Only a few previous studies of past tense verb inflection have used RT as a dependent variable: Joanisse and Seidenberg One way to address the discrepancies among previous studies, as well as the limitations associated with factorial designs employing relatively few stimuli, is to sample a much larger set of items from the language. Megastudies include stimuli on the order of thousands, rather than 50 to 100, and allow for the effects of variables to be modeled continuously rather than categorically (see In addition to providing a large database of response latencies and accuracies for past tense verb inflection, we also developed two new measures that are important to consider in past tense inflection, consistency and imageability. Similar to the spelling-to-sound consistency measure that has been well-studied in visual word recognition research The second variable that we measured was imageability. Imageability is a variable that reflects the extent to which 152 Behav Res (2013) 45:151-159 one is able to form a mental image of a word, and indeed many imageability norms are already available (e.g., The present study is based on 89 participants' accuracy and RTs for a past tense inflection task with 2,200 verbs. Each participant produced responses to 888 items. For each verb in the PTIP database, we included measures of RT, accuracy, and regularization errors (e.g., saying GRINDED for GRIND), along with the new imageability and consistency measures described above. The PTIP database is useful in examining the specific effects of predictor variables on RT and accuracy and allows for detailed item-level predictions. It is available as supplementary materials with this article for researchers who plan to examine other theoretical questions about past tense inflection, or are hoping to select well-controlled and well-examined stimuli for new studies. These data will serve as both a reference and an impetus for further research in the domain of past tense inflection. Experiment 1 The first experiment was conducted in order to collect imageability rating norms for the verbs in the PTIP database. Method Participants A group of 218 participants were recruited via Amazon's Mechanical Turk (AMT; see Materials The 2,200 words from the PTIP database (see below), plus another 112 words for use in another study, were divided into eight lists of 289 items each. The eight lists were presented as separate jobs in AMT. Procedure Each participant completed one list of the rating task, which was presented in Adobe Flash and appeared after a consent screen in the AMT job description. The instructions were the same as those used in Results The ratings were aggregated across participants for each item (excluding "do not know" responses), so that one mean imageability value was calculated for each verb. These values were used in Experiment 2 (see below). The mean rating across all verbs was 4.28 (SD 0 0.92), and the mean RT across all verbs was 3,191 ms (SD 0 1,695). The overall split-half reliability was r 0 .80, p < .001. Experiment 2 Method Participants A group of 113 native English-speaking college students from the Washington University subject pool participated in Behav Res (2013) 45:151-159 153 the study. After eliminating extreme outliers (less than 80 % accuracy overall; four participants) or participants whose data were subject to recording error (missing sound files from which to code accuracy-20 participants), 89 participants contributed to the final database

AN INVESTIGATION OF NEURAL MECHANISMS UNDERLYING VERB MORPHOLOGY DEFICITS IN APHASIA

Agrammatic aphasia is an acquired language disorder characterized by slow, non-fluent speech that include primarily content words. It is well-documented that people with agrammatism (PWA) have difficulty with production of verbs and verb morphology, but it is unknown whether these deficits occur at the single word-level, or are the result of a sentence-level impairment. The first aim of this paper is to determine the linguistic level that verb morphology impairments exist at by using magnetoencephalography (MEG) scanning to analyze neural response to two language tasks (one word-level, and one sentence-level). It has also been demonstrated that PWA benefit from a morphosemantic intervention for verb morphology deficits, but it is unknown if this therapy induces neuroplastic changes in the brain. The second aim of this paper is to determine whether or not neuroplastic changes occur after treatment, and explore the neural mechanisms by which this improvement occurs

Semantic priming, schizophrenia and the ketamine model of psychosis

The central aim of the studies presented in my thesis was to investigate the modulation of semantic memory function and its neural correlates in relation to schizophrenia. Semantic information is stored information that is impersonal, and includes knowledge of words and their meaning, and general knowledge about the world. Semantic memory deficits are thought to underlie core symptoms of schizophrenia, including delusions, thought disorder and alogia. The semantic priming (SP) paradigm has been used extensively to assess semantic memory function. In SP experiments, healthy individuals usually respond faster to target words (e.g. atlas) when these are preceded by semantically related prime words (e.g. map) than when preceded by unrelated prime words (e.g. chess)—referred to as the SP effect. My thesis combined several approaches, using SP as the main tool. First, a behavioural study was conducted with patients with schizophrenia. Second, two neuroimaging experiments investigated modulation of neural correlates of SP in schizophrenia. Last, two studies utilised the ketamine model of psychosis in healthy volunteers to investigate: (i) the effects of acute ketamine administration on semantic memory function in drug‐naïve participants, and (ii) the effects of repeated ketamine administration, seen in those who use ketamine recreationally. In summary, three key findings indicate that the employment of conscious strategies during semantic processing is impaired (i) by acute ketamine administration to healthy volunteers, and (ii) in schizophrenia patients as indicated firstly by behavioural results, and (iii) secondly by altered prefrontal haemodynamic activation. None of my studies found any modulation of SP when strategic influences were limited i.e. under automatic conditions. My findings suggest that the disrupted semantic processing in schizophrenia is associated with the modulation of the so‐called ‘executive functions’ and prefrontal haemodynamic responses. Future research should explore whether or not this impairment is specific to semantic memory processing

The role of morpho-phonological regularity and similarity in processing italian verbs

2010 - 2011The aim of this experimental study is to investigate the representation and processing of regular, sub-regular and irregular verbal forms of Italian. In psycholinguistics, the debate on the processing of regular and irregular verbs is based on the contrast between Dual Mechanism models (Pinker and Prince, 1988; Clahsen, 1999; Caramazza, Laudanna and Romani, 1988), which claim that regular forms are processed through the application of inflectional rules, while irregular forms are retrieved as whole words from the associative memory, and Connectionist models (McClelland and Patterson, 2002; Joanisse and Seidenberg, 1999; Rumelhart and McClelland, 1986), which claim that a single associative mechanism accounts for both regular and irregular form processing. Despite Dual Mechanism models clearly support distinct mechanisms for the representation of regular and irregular verbs, several studies point out that this dichotomy is challenged by the existence of families of "sub-regular" verbs, which share morpho-phonological features and follow the same inflectional patterns. The debate on sub-regular patterns evolved especially with respect to languages like Italian, based on the organization into inflectional classes, each characterized by a specific regular paradigm, and on a varying aggregation of sub-regular families. The coexistence of multiple regular patterns and sub-regular families seems to be consistent with the Optimality Theory (Prince and Smolensky, 1993; Benua, 1997, Bernhardt and Stemberger, 1998; Smolensky, 1999), which departs from the traditional concept of inflectional rule and invokes the use of phonological constraints, based on phonological analogies between surface forms of words and on different degrees of relevance and "violability". [edited by author]X n.s

Form, meaning and context in lexical access: MEG and behavioral evidence

One of the main challenges in the study of cognition is how to connect brain activity to cognitive processes. In the domain of language, this requires coordination between two different lines of research: theoretical models of linguistic knowledge and language processing on the one side and brain sciences on the other. The work reported in this dissertation attempts to link these two lines of research by focusing on one particular aspect of linguistic processing, namely lexical access. The rationale for this focus is that access to the lexicon is a mandatory step in any theory of linguistic computation, and therefore findings about lexical access procedures have consequences for language processing models in general. Moreover, in the domain of brain electrophysiology, past research on event-related brain potentials (ERPs) - electrophysiological responses taken to reflect processing of certain specific kinds of stimuli or specific cognitive processes - has uncovered different ERPs that have been connected to linguistic stimuli and processes. One particular ERP, peaking at around 400 ms post-stimulus onset (N400) has been linked to lexico-semantic processing, but its precise functional interpretation remains controversial: The N400 has been proposed to reflect lexical access procedures as well as higher order semantic/pragmatic processing. In a series of three MEG experiments, we show that access to the lexicon from print occurs much earlier than previously thought, at around 200 ms, but more research is needed before the same conclusion can be reached about lexical access based on auditory or sign language input. The cognitive activity indexed by the N400 and its MEG analogue is argued to constitute predictive processing that integrates information from linguistic and non-linguistic sources at a later, post-lexical stage

Learning, Consolidating, and Generalising Novel Morphology

Despite a central role for morphological knowledge in supporting linguistic generalisation, the neural representations supporting its learning remain largely unexplored. This thesis addressed this gap by exploring the role of memory consolidation in morphological learning and generalisation. In three experiments, adult participants learned an artificial language in which stems (e.g. gleet, shiln) combined with plural affixes (e.g. –aff, -opp; gleetaff, shilnopp) to refer to the occupation of multiple male and female characters. Mimicking properties of morphological systems in natural languages, the plurals varied in their phonological consistency/ambiguity and type/token frequency. Two sets of plurals, distinguished by gender, were trained on two successive days. Experiment 1 revealed that generalisation to novel phonologically ambiguous forms measured on the second day showed a greater influence of token frequency for plurals trained on the previous day, suggesting overnight changes in their underlying representations. Experiment 2 examined this effect further by using fMRI to compare the neural representations underlying plurals learned on the day of scanning or on the previous day. Representational Similarity Analysis revealed increased similarity structure among high type frequency plurals and reduced similarity structure among high token frequency plurals following overnight consolidation in the left superior temporal gyrus (STG). These results are consistent with a Complementary Learning Systems (CLS) model in which overnight consolidation supports the development of overlapping representations among several items sharing the same feature (here, an affix; type frequency) and strengthens item-specific representations for frequently occurring items (token frequency). Additionally, connectivity analyses showed that the functional coupling between the left STG and the left dorsolateral prefrontal cortex was weaker for high type frequency plurals and stronger for high token frequency plurals following overnight consolidation. These results suggest that the engagement of prefrontal control processes in retrieving the newly-learned plurals is subject to overnight consolidation and sensitive to the similarity structure underlying the plurals to be retrieved. However, the overnight changes in similarity structure and functional networks observed in Experiment 2 were not mirrored by changes in generalisation to novel forms as were observed in Experiment 1. Experiment 3 aimed to address the discrepancy in consolidation-related changes in generalisation behaviour between the first two experiments. Type/token frequencies were manipulated to bias learning, consolidation, and generalisation towards high token frequency plurals. Despite this manipulation, no consolidation-related changes in generalisation were observed. Findings from all three experiments are interpreted in the context of the CLS model and a role for overnight consolidation in morphological learning and generalisation is discussed.Economic and Social Research Counci

Sukzessiv-bilinguale Kinder : der Erwerb von Partizipien in der frühen Zweitsprache Deutsch

The study focuses on the acquisition of past participle inflection by children acquiring German as a second language. Two issues are addressed: the relevance of age of onset (AO) and critical periods, and the status of regular and irregular inflection. Longitudinal data from two Italian adult L2 learners and from seven successive bilingual Turkish children acquiring German (AO 3-4) are investigated. The main findings confirm that the adults acquire past participles unlike monolinguals and unlike the investigated bilingual children, indicating an effect of critical periods. The successive bilingual children behave basically like monolinguals. The bilingual children overgeneralize the regular suffix -t more often than the irregular suffix -n, which cannot be explained by frequency. This indicates the different representational status of these two inflections and strengthens dual mechanism accounts. Differences with respect to error frequencies can be explained on the phonological level