Time-Driven Effects on Processing Relative Clauses

The present response time study investigated how a hypothesized time-based working memory constraint of 2–3 s affects the resolution of grammatical and semantic dependencies. Congruent and incongruent object relative (OR) and subject relative sentences were read at different presentation rates so that the distance between dependent words was either shorter or longer than 2–3 s. Incongruent OR sentences showed an effect of presentation rate. Experiment 1 focused on grammatical dependencies. Processing of adjectives with agreement features mismatching those of the preceding dependent word showed rapid agreement resolution at a time-interval below 2 s. Dependency intervals over 3 s reflected a different, more time-consuming process possibly due to extended search in sentence semantic representations as the grammatical form of the first word in the dependency fades away. In experiment 2, focusing on semantic dependencies, incongruent OR sentences displayed a different pattern: a gradual increase in processing time as a function of distance between dependent words. Thus, the 2–3 s long time-window seems to constrain the maintenance of grammatical forms in working memory

Cortical thickness of planum temporale and pars opercularis in native language tone processing

The present study investigated the relationship between linguistic tone processing and cortical thickness of bilateral planum temporale (PT) and pars opercularis of the inferior frontal gyrus (IFGpo). Swedish tones on word stems function as cues to upcoming endings. Correlating structural brain imaging data with participants’ response time patterns for suffixes, we found that thicker cortex in the left PT was associated with greater reliance on tones to anticipate upcoming inflections on real words. On inflected pseudoword stems, however, the cortical thickness of left IFGpo was associated with tone-suffix processing. Thus cortical thickness of the left PT might play a role in processing tones as part of stored representations for familiar speech segments, most likely when inflected forms are accessed as whole words. In the absence of stored representations, listeners might need to rely on morphosyntactic rules specifying tone-suffix associations, potentially facilitated by greater cortical thickness of left IFGpo

Cognitive and neural mechanisms of inflectional morphology processing : Studies of native speakers and second language learners of Swedish

The present dissertation investigates inflectional morphology processing in native speakers and second language (L2) learners of Swedish. Results of Study 1 suggest that two separate neural mechanisms might be available for native comprehension of inflected words, as reflected in event-related brain potentials obtained for visually presented verb forms. Overregularized verbs (e.g. *bär+de ‘bear + past tense’) yielded a left anterior negativity (LAN), indicating decompositional processing of the regular tense inflection versus whole-word retrieval of correct irregular verb forms (e.g. bär ‘bore’). Enhanced long-range neural oscillatory phase synchrony observed for familiar irregular words potentially reflected increased engagement of the ventral language processing stream during whole-word access. As Swedish is characterized by a predictive association between specific word stem tones and upcoming suffixes, facilitating speech processing, Study 2 examines the integration of tonal cues into the native morphological system. Correlational analysis was conducted between cortical thickness in selected brain regions and individual participants’ response time patterns for suffix recognition following the tonal cue in real words (e.g. hattAccent 1+en ‘hat+sg’) and pseudowords (e.g. kvutAccent 1+en ‘kvut+sg’). Results suggest that the left planum temporale might play a role when tones are accessed as part of whole-word memory representations, whereas the pars opercularis of the left inferior frontal gyrus could potentially support rule-based decompositional analysis of cued suffixes when no stored full-form representations are present. Study 3 focuses on the L2 acquisition of the tonal aspects of Swedish inflectional morphology. Response time patterns to inflected verbs indicate facilitated processing of word endings validly cued by the preceding stem tone in proficient L2 learners of Swedish, who had not received any explicit information about the tested L2 regularity. As these results suggested gradual and slow implicit acquisition of tone-suffix associations through exposure to L2 input, Study 4 explores possibilities of training the L2 feature at earlier stages of learning. Performance data collected during a two-week-period of training with a game prototype show gradually faster and more accurate responses to suffixes cued by preceding tones, indicating that low proficient learners start to integrate Swedish word accents into their L2 morphological processing system

Processing filler-gap dependencies in an L2: An Event-Related Potential study

The present study investigated second language (L2) learners’ processing of filler-gap dependencies and tested the implications of Clahsen and Felser’s (2006) shallow structure hypothesis according to which L2 learners underuse syntactic information during the processing of these sentence types. Advanced L2 learners of English (native Swedish speakers) listened to English sentences with object-relative, subject-relative and finite complement clauses. Event-related potentials were recorded at the word that, the embedded verb and the following word: a prepositional phrase, a semantically congruent or incongruent noun phrase or an extra noun phrase ungrammatically occupying the canonical object position after the verb in object-relative clauses. Compared to correct sentences, the extra noun phrase elicited a late positivity with a central-posterior distribution (P600). No increased negativity indicating problems with semantic processing (N400) was observed, suggesting that the extra noun phrase was initially interpreted as the object of the verb, and the integration of the clause-initial noun phrase (the filler) with the verb was delayed. The syntactic violation involved in this interpretation led to syntactic repair processes reflected in the P600 effect. The relative pronoun that in object-relative clauses gave rise to an enhanced negativity over anterior and central sites probably indexing storage of the filler in working memory. Finally, semantically anomalous nouns yielded a P600 but no N400 effect in grammatically correct complement clauses, which was interpreted to reflect the conflict between the relations dictated by the syntactic structure and the alternative thematic relationships that might be established to make sense of these sentences. The observation that participants relied on both syntactic and semantic information during sentence comprehension is not consistent with Clahsen and Felser’s proposal. The results of this study suggest that learners might differ from native speakers in terms of processing speed, which potentially affects the relative order and nature of interaction of different subprocesses involved in sentence comprehension

Brain responses to syntax constrained by time-driven implicit prosodic phrases

Previous research suggests that time-based working memory limits of 2-3 s constrain the integration of verbal information, and that speakers tend to parse sentences into prosodic phrases that do not extend beyond this time window. The present study used Event-Related Potentials (ERPs) to investigate how time-driven implicit prosodic phrasing influences the syntactic processing of embedded clauses. Participants read Swedish sentences in which the first embedded clause had a subordinate, main or neutral clause structure cued by the position of the sentence adverb. The presentation rate was manipulated so that either one or two clauses were read within 2.7 s. When the 2.7 s time limit was reached before the onset of the embedded clause, the sentence adverb indicating subordinate clause structure elicited a posterior negativity and a late positivity. These effects were interpreted to reflect the detection of unexpected word order, followed by the revision of the anticipated main clause structure. A positive shift that correlated with individual working memory span was also seen at the clause-final word after 2.7 s, possibly indicating closure of an implicit prosodic phrase. These results suggest that prosodic phrasing was influenced by time-based working memory limits, which in turn affected syntactic analysis: readers were more likely to interpret an embedded clause as a main clause if it could be associated with the beginning of a new prosodic phrase

Cortical thickness of Planum Temporale in native language tone processing

INTRODUCTION: Non-native linguistic tone learning ability has been found to be influenced by the anatomy of primary auditory regions in the left hemisphere (Wong et al., 2008). In native speakers, however, where phonemic categories are firmly established, variations in the macrostructure of more secondary auditory processing areas might be expected to affect performance. The present study investigated the relationship between cortical thickness of the Planum Temporale (PT) and the processing of tones in natural language stimuli by Swedish native speakers. PT has previously been found to be involved in processing Thai (Xu et al., 2006) and Swedish tones (Roll et al., 2015), and in phonological processing generally (Graves et al., 2008). In Swedish, tones on word stems function as predictive cues to upcoming morphosyntactic structure, due to associations between stem tone patterns and specific grammatical suffixes. The degree to which listeners evidence anticipatory behaviour in their responses to such cued suffixes thus can be assumed to be mediated by individual variation in processing preceding tonal cues. METHODS: Magnetic resonance imaging scans were collected from native speakers of Swedish. Participants listened to sentences in which the inflectional suffix on the target word was either validly or invalidly cued by the preceding tone. The time it took to decide on suffix meaning (singular/plural) after suffix onset was measured. Cortical reconstruction and volumetric segmentation was performed using the FreeSurfer image analysis suite (http://surfer.nmr.mgh.harvard.edu/). Each processed subject was transformed into common space (fsaverage) and the average cortical thickness of PT was extracted in FreeSurfer after transformation of estimation of PT as defined in the Harvard-Oxford cortical and subcortical structural atlases in FMRIB Software Library (FSL) into common space. RESULTS: Individual participants’ response time advantage for valid over invalidly cued suffixes positively correlated with cortical thickness in the left PT, but not in the right PT. Thus, thicker left PT cortex was associated with relatively greater disruption in speech comprehension caused by an invalid tonal cue. Subgroup comparison also showed generally faster response times for participants with relatively thicker left PT cortex compared to individuals with thinner cortex in the same area. CONCLUSION: The results suggest that the cortical anatomy of the left PT affects native linguistic tone processing. The PT has been proposed to constitute a computational interface between incoming sound patterns, analysed into components, and stored auditory objects (Griffiths & Warren, 2002). From this perspective, the present results might indicate that the cortical thickness of the left PT plays a facilitating role in the extraction of linguistic tone patterns from stimuli and their matching with stored representations in memory

Brain responses to morphologically complex verbs : An electrophysiological study of Swedish regular and irregular past tense forms

The present electrophysiological study investigated irregular versus regular verb form processing in Swedish during reading. In line with previous results from other languages, overregularized verbs, i.e. incorrect irregular stem + regular past tense suffix combinations (e.g. *stjäl + de ‘steal + past tense’), elicited a left-lateralized negativity (LAN) relative to correct irregulars (stal ‘stole’), suggesting rule-based decomposition of regularly inflected words. Lack of a similar effect for misapplication of the irregular stem formation pattern on regular verbs (e.g. *löft ‘lifted’ instead of lyfte) suggests the involvement of different processing mechanisms, possibly whole word access, for irregular items, at least to some degree. A P600 showing reprocessing was seen for all incorrect forms. The results add cross-linguistic support for morphological decomposition in the verbal inflection of a language where results from previous neurolinguistic studies of nominal inflection have only suggested the use of full-form access to words

Cortical thickness and surface area of left anterior temporal areas affects processing of phonological cues to morphosyntax

Lack of methods to experimentally assess the perceptual processing of sound features and allow one to measure differences in phonological proficiency has been a limitation for speech processing studies in native speakers. Tonal features associated with Swedish word-stems, word accents, which cue grammatical suffixes, constitute, however, such sound features that can be exploited to generate measures of reliance on morphosyntactically relevant phonological information during word processing. Specifically, there is a natural variance between native speakers in response time (RT) difference between phonologically valid and invalid word accent-suffix combinations that can be used to quantify perceptual phonological proficiency. This study uses ultra-high field magnetic resonance imaging (MRI) to investigate word accents as phonological cues to morphosyntactic meaning. The study adds to the understanding of the neural basis for both morphosyntactically relevant phonological cues by reporting correlations between differences in listeners’ RT for validly and invalidly cued suffixes and cortical thickness in left anterior and middle temporal gyrus, and the left anterior superior temporal sulcus as well as cortical surface area in the left middle and inferior temporal gyri. The cortical areas studied are known constituents of the ventral speech processing stream, necessary for word and phrase recognition

Brain responses to morphologically complex words: an electrophysiological study on Swedish past tense forms

Dual system models postulate two distinct neural mechanisms for the processing of inflected words: irregular forms (e.g. ‘went’) are assumed to be directly accessed as whole word representations, whereas regularly inflected items (e.g. ‘played’) might undergo rule-based decomposition (Pinker & Ullman, 2002). Irregular verb stems incorrectly carrying a regular inflectional suffix have been reported to elicit a left anterior negativity (LAN), commonly interpreted as indexing violation of morphosyntactic regularities, and thus indicating rule application associated with the regular inflection (e.g. Penke et al., 1997). In the first electrophysiological study on Swedish regular/irregular verb morphology, we recorded brain responses to correct versus incorrect past tense verbs visually presented in sentences. Irregular verb stems incorrectly inflected with the regular suffix generated an increased left-lateralized negativity, interpreted as a LAN for misapplication of the morphological inflection rule. No negativity was observed for regular verb stems incorrectly containing a stem vowel change on analogy to irregular verb patterns. These findings are in line with previous results suggesting that a rule-based processing route is available for regularly inflected items. Alternatively, the observed waveforms might be interpreted in terms of a decreased negativity for correct irregular verbs. Such verbs would then be directly accessed in the lexicon while the other conditions would involve morphological analysis, eliciting increased left-lateralized negativities, including incorrect regular verbs where rule-based processing might have been triggered by regularities in the stem vowel change. From this perspective, LAN might signal morphological rule application instead of detection of rule violation (Krott & Lebib, 2013)

The influence of the cortical thickness of Planum Temporale on word tone processing in Swedish native speakers

In Swedish, tones on word stems function as predictive cues to upcoming grammatical suffixes. Invalid matching of these linguistic tonal cues to suffixes affects native speakers of Swedish in their linguistic processing (Roll et al., 2010). Planum Temporale (PT) has previously been found to be involved in processing Thai (Xu et al., 2006) and Swedish tones (Roll et al., 2015), and in phonological processing generally (Graves et al., 2008). The present study investigated the relationship between cortical thickness (CT) of PT and the processing of tones in suffixed word stimuli by Swedish native speakers using magnetic resonance imaging (MRI). The average CT of PT was extracted from each participant using the Freesurfer analysis suite on T1-weighted image volumes. The results show that individual participants’ response time advantage for valid over invalidly cued suffixes positively correlated with CT in the left PT which suggests that the CT of left PT affects native linguistic tone processing. Interestingly, comparing responses to real word (stem + suffix) stimuli with comparable pseudoword test stimuli (pseudostem + suffix), similar results for CT are found, albeit not in PT, but instead in Broadmann Area 44. This might suggest that suffixed pseudowords cannot be processed in the same way as existing inflected words. PT has been proposed to play a role in lexical phonological access (Graves et al., 2007, 2008). Thus, the present results might indicate that the CT of the left PT facilitates accessing stored whole-word phonological representations of inflected word forms, not available for pseudowords