Publications

Abstract

Sprekers hebben een sterke neiging om syntactische structuren te hergebruiken in nieuwe zinnen. Wanneer we een situatie beschrijven met een passieve zin bijvoorbeeld: 'De vrouw wordt begroet door de man', zullen we voor de beschrijving van een nieuwe situatie gemakkelijker opnieuw een passieve zin gebruiken. Vooral bij moeilijke syntactische structuren is de neiging om ze te hergebruiken erg sterk. Voor gemakkelijke zinsconstructies geldt dat minder. Maar als deze toch hergebruikt worden dan gaat dit samen met een sneller initiëren van de beschrijving. Ook in het brein zien we dat het herhalen van syntactische structuren de verwerking ervan vergemakkelijkt. Bepaalde hersengebieden die zorgen voor de verwerking van syntactische structuren zijn zeer actief de eerste keer dat een syntactische structuur wordt verwerkt, en minder actief de tweede keer. Het gaat hier om een gebiedje in de frontaalkwab en een gebiedje in de temporaalkwab. Opvallend is ook dat deze gebieden de verwerking van syntactische structuren ondersteunen zowel tijdens het spreken als tijdens het luisteren.

Abstract

During speaking and listening syntactic processing is a crucial step. It involves specifying syntactic relations between words in a sentence. If the production and comprehension modality share the neuronal substrate for syntactic processing then processing syntax in one modality should lead to adaptation effects in the other modality. In the present functional magnetic resonance imaging experiment, participants either overtly produced or heard descriptions of pictures. We looked for brain regions showing adaptation effects to the repetition of syntactic structures. In order to ensure that not just the same brain regions but also the same neuronal populations within these regions are involved in syntactic processing in speaking and listening, we compared syntactic adaptation effects within processing modalities (syntactic production-to-production and comprehension-to-comprehension priming) with syntactic adaptation effects between processing modalities (syntactic comprehension-to-production and production-to-comprehension priming). We found syntactic adaptation effects in left inferior frontal gyrus (Brodmann's area [BA] 45), left middle temporal gyrus (BA 21), and bilateral supplementary motor area (BA 6) which were equally strong within and between processing modalities. Thus, syntactic repetition facilitates syntactic processing in the brain within and across processing modalities to the same extent. We conclude that that the same neurobiological system seems to subserve syntactic processing in speaking and listening.

Abstract

There is a substantial literature describing how infants become more sensitive to differences between native phonemes (sounds that are both present and meaningful in the input) and less sensitive to differences between non-native phonemes (sounds that are neither present nor meaningful in the input) over the course of development. Here, we review an emergent strand of literature that gives a more nuanced notion of the problem of sound category learning. This research documents infants’ discovery of phonological status, signaled by a decrease in sensitivity to sounds that map onto the same phonemic category vs. different phonemic categories. The former phones are present in the input, but their difference does not cue meaning distinctions because they are tied to one and the same phoneme. For example, the diphthong I in I’m should map to the same underlying category as the diphthong in I’d, despite the fact that the first vowel is nasal and the second oral. Because such pairs of sounds are processed differently than those than map onto different phonemes by adult speakers, the learner has to come to treat them differently as well. Interestingly, there is some evidence that infants’ sensitivity to dimensions that are allophonic in the ambient language declines as early as 11 months. We lay out behavioral research, corpora analyses, and computational work which sheds light on how infants achieve this feat at such a young age. Collectively, this work suggests that the computation of complementary distribution and the calculation of phonetic similarity operate in concert to guide infants toward a functional interpretation of sounds that are present in the input, yet not lexically contrastive. In addition to reviewing this literature, we discuss broader implications for other fundamental theoretical and empirical questions.

Abstract

Previous research showed an important association between reading and writing skills (literacy) and the phonological loop. However, the effects of literacy on other working memory components remain unclear. In this study, we investigated performance of illiterate subjects and their matched literate controls on verbal and nonverbal working memory tasks. Results revealed that the phonological loop is significantly influenced by literacy, while the visuospatial sketchpad appears to be less affected or not at all. Results also suggest that the central executive might be influenced by literacy, possibly as an expression of cognitive reserve.

Abstract

Identifying genetic variants influencing human brain structures may reveal new biological mechanisms underlying cognition and neuropsychiatric illness. The volume of the hippocampus is a biomarker of incipient Alzheimer's disease and is reduced in schizophrenia, major depression and mesial temporal lobe epilepsy. Whereas many brain imaging phenotypes are highly heritable, identifying and replicating genetic influences has been difficult, as small effects and the high costs of magnetic resonance imaging (MRI) have led to underpowered studies. Here we report genome-wide association meta-analyses and replication for mean bilateral hippocampal, total brain and intracranial volumes from a large multinational consortium. The intergenic variant rs7294919 was associated with hippocampal volume (12q24.22; N = 21,151; P = 6.70 × 10(-16)) and the expression levels of the positional candidate gene TESC in brain tissue. Additionally, rs10784502, located within HMGA2, was associated with intracranial volume (12q14.3; N = 15,782; P = 1.12 × 10(-12)). We also identified a suggestive association with total brain volume at rs10494373 within DDR2 (1q23.3; N = 6,500; P = 5.81 × 10(-7)).

Abstract

In this paper, we present two novel perspectives on the function of the left inferior frontal gyrus (LIFG). First, a structured sequence processing perspective facilitates the search for functional segregation within the LIFG and provides a way to express common aspects across cognitive domains including language, music and action. Converging evidence from functional magnetic resonance imaging and transcranial magnetic stimulation studies suggests that the LIFG is engaged in sequential processing in artificial grammar learning, independently of particular stimulus features of the elements (whether letters, syllables or shapes are used to build up sequences). The LIFG has been repeatedly linked to processing of artificial grammars across all different grammars tested, whether they include non-adjacent dependencies or mere adjacent dependencies. Second, we apply the sequence processing perspective to understand how the functional segregation of semantics, syntax and phonology in the LIFG can be integrated in the general organization of the lateral prefrontal cortex (PFC). Recently, it was proposed that the functional organization of the lateral PFC follows a rostro-caudal gradient, such that more abstract processing in cognitive control is subserved by more rostral regions of the lateral PFC. We explore the literature from the viewpoint that functional segregation within the LIFG can be embedded in a general rostro-caudal abstraction gradient in the lateral PFC. If the lateral PFC follows a rostro-caudal abstraction gradient, then this predicts that the LIFG follows the same principles, but this prediction has not yet been tested or explored in the LIFG literature. Integration might provide further insights into the functional architecture of the LIFG and the lateral PFC.

Abstract

A recent hypothesis in empirical brain research on language is that the fundamental difference between animal and human communication systems is captured by the distinction between finite-state and more complex phrase-structure grammars, such as context-free and context-sensitive grammars. However, the relevance of this distinction for the study of language as a neurobiological system has been questioned and it has been suggested that a more relevant and partly analogous distinction is that between non-adjacent and adjacent dependencies. Online memory resources are central to the processing of non-adjacent dependencies as information has to be maintained across intervening material. One proposal is that an external memory device in the form of a limited push-down stack is used to process non-adjacent dependencies. We tested this hypothesis in an artificial grammar learning paradigm where subjects acquired non-adjacent dependencies implicitly. Generally, we found no qualitative differences between the acquisition of non-adjacent dependencies and adjacent dependencies. This suggests that although the acquisition of non-adjacent dependencies requires more exposure to the acquisition material, it utilizes the same mechanisms used for acquiring adjacent dependencies. We challenge the push-down stack model further by testing its processing predictions for nested and crossed multiple non-adjacent dependencies. The push-down stack model is partly supported by the results, and we suggest that stack-like properties are some among many natural properties characterizing the underlying neurophysiological mechanisms that implement the online memory resources used in language and structured sequence processing.

Abstract

In this thesis I approach language as a neurobiological system. I defend a sequence processing perspective on language and on the function of Broca's region in the left inferior frontal gyrus (LIFG). This perspective provides a way to express common structural aspects of language, music and action, which all engage the LIFG. It also facilitates the comparison of human language and structured sequence processing in animals. Research on infants, song-birds and non-human primates suggests an interesting role for non-adjacent dependencies in language acquisition and the evolution of language. In a series of experimental studies using a sequence processing paradigm called artificial grammar learning (AGL), we have investigated sequences with adjacent and non-adjacent dependencies. Our behavioral and transcranial magnetic stimulation (TMS) studies show that healthy subjects successfully discriminate between grammatical and non-grammatical sequences after having acquired aspects of a grammar with nested or crossed non-adjacent dependencies implicitly. There were no indications of separate acquisition/processing mechanisms for sequence processing of adjacent and non-adjacent dependencies, although acquisition of non-adjacent dependencies takes more time. In addition, we studied the causal role of Broca‟s region in processing artificial syntax. Although syntactic processing has already been robustly correlated with activity in Broca's region, the causal role of Broca's region in syntactic processing, in particular syntactic comprehension has been unclear. Previous lesion studies have shown that a lesion in Broca's region is neither a necessary nor sufficient condition to induce e.g. syntactic deficits. Subsequent to transcranial magnetic stimulation of Broca‟s region, discrimination of grammatical sequences with non-adjacent dependencies from non-grammatical sequences was impaired, compared to when a language irrelevant control region (vertex) was stimulated. Two additional experiments show perturbation of discrimination performance for grammars with adjacent dependencies after stimulation of Broca's region. Together, these results support the view that Broca‟s region plays a causal role in implicit structured sequence processing.

Abstract

This study provides ERP and oscillatory dynamics data associated with the comprehension of narratives involving counterfactual events. Participants were given short stories describing an initial situation (“Marta wanted to plant flowers in her garden…”), followed by a critical sentence describing a new situation in either a factual (“Since she found a spade, she started to dig a hole”) or counterfactual format (“If she had found a spade, she would have started to dig a hole”), and then a continuation sentence that was either related to the initial situation (“she bought a spade”) or to the new one (“she planted roses”). The ERPs recorded for the continuation sentences related to the initial situation showed larger negativity after factuals than after counterfactuals, suggesting that the counterfactual's presupposition – the events did not occur – prevents updating the here-and-now of discourse. By contrast, continuation sentences related to the new situation elicited similar ERPs under both factual and counterfactual contexts, suggesting that counterfactuals also activate momentarily an alternative “as if” meaning. However, the reduction of gamma power following counterfactuals, suggests that the “as if” meaning is not integrated into the discourse, nor does it contribute to semantic unification processes.

Abstract

When an adult claims he cannot sleep without his teddy bear, people tend to react surprised. Language interpretation is, thus, influenced by social context, such as who the speaker is. The present study reveals inter-individual differences in brain reactivity to social aspects of language. Whereas women showed brain reactivity when stereotype-based inferences about a speaker conflicted with the content of the message, men did not. This sex difference in social information processing can be explained by a specific cognitive trait, one’s ability to empathize. Individuals who empathize to a greater degree revealed larger N400 effects (as well as a larger increase in γ-band power) to socially relevant information. These results indicate that individuals with high-empathizing skills are able to rapidly integrate information about the speaker with the content of the message, as they make use of voice-based inferences about the speaker to process language in a top-down manner. Alternatively, individuals with lower empathizing skills did not use information about social stereotypes in implicit sentence comprehension, but rather took a more bottom-up approach to the processing of these social pragmatic sentences.

Abstract

Introduction: What’s happening in the brains of two people having a conversation? One reasonable guess is that in the fMRI scanner we’d see most of their brains light up. Another is that their EEG will be a total mess, reflecting dozens of interacting neuronal systems. Conversation recruits all of the basic language systems reviewed in this book. It also heavily taxes cognitive systems more likely to be found in handbooks of memory, attention and control, or social cognition (Brownell & Friedman, 2001). With most conversations going beyond the single utterance, for instance, they place a heavy load on episodic memory, as well as on the systems that allow us to reallocate cognitive resources to meet the demands of a dynamically changing situation. Furthermore, conversation is a deeply social and collaborative enterprise (Clark, 1996; this volume), in which interlocutors have to keep track of each others state of mind and coordinate on such things as taking turns, establishing common ground, and the goals of the conversation.

Abstract

During spoken language interpretation, listeners rapidly relate the meaning of each individual word to what has been said before. However, spoken words often contain spurious other words, like 'day' in 'daisy', or 'dean' in 'sardine'. Do listeners also relate the meaning of such unintended, spurious words to the prior context? We used ERPs to look for transient meaning-based N400 effects in sentences that were completely plausible at the level of words intended by the speaker, but contained an embedded word whose meaning clashed with the context. Although carrier words with an initial embedding ('day' in 'daisy') did not elicit an embedding-related N400 effect relative to matched control words without embedding, carrier words with a final embedding ('dean' in 'sardine') did elicit such an effect. Together with prior work from our lab and the results of a Shortlist B simulation, our findings suggest that listeners do semantically interpret embedded words, albeit not under all conditions. We explain the latter by assuming that the sense-making system adjusts its hypothesis for how to interpret the external input at every new syllable, in line with recent ideas of active sampling in perception.

Abstract

Research from the past decade has shown that understanding the meaning of words and utterances (i.e., abstracted symbols) engages the same systems we used to perceive and interact with the physical world in a content-specific manner. For example, understanding the word “grasp” elicits activation in the cortical motor network, that is, part of the neural substrate involved in planned and executing a grasping action. In the embodied literature, cortical motor activation during language comprehension is thought to reflect motor simulation underlying conceptual knowledge [note that outside the embodied framework, other explanations for the link between action and language are offered, e.g., Mahon, B. Z., & Caramazza, A. A critical look at the embodied cognition hypothesis and a new proposal for grouding conceptual content. Journal of Physiology, 102, 59–70, 2008; Hagoort, P. On Broca, brain, and binding: A new framework. Trends in Cognitive Sciences, 9, 416–423, 2005]. Previous research has supported the view that the coupling between language and action is flexible, and reading an action-related word form is not sufficient for cortical motor activation [Van Dam, W. O., van Dijk, M., Bekkering, H., & Rueschemeyer, S.-A. Flexibility in embodied lexical–semantic representations. Human Brain Mapping, doi: 10.1002/hbm.21365, 2011]. The current study goes one step further by addressing the necessity of action-related word forms for motor activation during language comprehension. Subjects listened to indirect requests (IRs) for action during an fMRI session. IRs for action are speech acts in which access to an action concept is required, although it is not explicitly encoded in the language. For example, the utterance “It is hot here!” in a room with a window is likely to be interpreted as a request to open the window. However, the same utterance in a desert will be interpreted as a statement. The results indicate (1) that comprehension of IR sentences activates cortical motor areas reliably more than comprehension of sentences devoid of any implicit motor information. This is true despite the fact that IR sentences contain no lexical reference to action. (2) Comprehension of IR sentences also reliably activates substantial portions of the theory of mind network, known to be involved in making inferences about mental states of others. The implications of these findings for embodied theories of language are discussed.

Abstract

Processing non-adjacent dependencies is considered to be one of the hallmarks of human language. Assuming that sequence-learning tasks provide a useful way to tap natural-language-processing mechanisms, we cross-modally combined serial reaction time and artificial-grammar learning paradigms to investigate the processing of multiple nested (A1A2A3B3B2B1) and crossed dependencies (A1A2A3B1B2B3), containing either three or two dependencies. Both reaction times and prediction errors highlighted problems with processing the middle dependency in nested structures (A1A2A3B3_B1), reminiscent of the ‘missing-verb effect’ observed in English and French, but not with crossed structures (A1A2A3B1_B3). Prior linguistic experience did not play a major role: native speakers of German and Dutch—which permit nested and crossed dependencies, respectively—showed a similar pattern of results for sequences with three dependencies. As for sequences with two dependencies, reaction times and prediction errors were similar for both nested and crossed dependencies. The results suggest that constraints on the processing of multiple non-adjacent dependencies are determined by the specific ordering of the non-adjacent dependencies (i.e. nested or crossed), as well as the number of non-adjacent dependencies to be resolved (i.e. two or three). Furthermore, these constraints may not be specific to language but instead derive from limitations on structured sequence learning.

Abstract

Rhyme processing is reflected in the electrophysiological signals of the brain as a negative deflection for non-rhyming as compared to rhyming stimuli around 450 ms after stimulus onset. Studies have shown that this N450 component is not solely sensitive to rhyme but also responds to other types of phonological overlap. In the present study, we examined whether the N450 component can be used to gain insight into the global similarity effect, indicating that rhyme judgment skills decrease when participants are presented with word pairs that share a phonological overlap but do not rhyme (e.g., bell–ball). We presented 20 adults with auditory rhyming, globally similar overlapping and unrelated word pairs. In addition to measuring behavioral responses by means of a yes/no button press, we also took EEG measures. The behavioral data showed a clear global similarity effect; participants judged overlapping pairs more slowly than unrelated pairs. However, the neural outcomes did not provide evidence that the N450 effect responds differentially to globally similar and unrelated word pairs, suggesting that globally similar and dissimilar non-rhyming pairs are processed in a similar fashion at the stage of early lexical access.

Abstract

Background. Rhyme awareness is one of the earliest forms of phonological awareness to develop and is assessed in many developmental studies by means of a simple rhyme task. The influence of more demanding experimental paradigms on rhyme judgment performance is often neglected. Addressing this issue may also shed light on whether rhyme processing is more global or analytical in nature. Aims. The aim of the present study was to examine whether lexical status and global similarity relations influenced rhyme judgments in kindergarten children and if so, if there is an interaction between these two factors. Sample. Participants were 41 monolingual Dutch-speaking preliterate kindergartners (average age 6.0 years) who had not yet received any formal reading education. Method. To examine the effects of lexical status and phonological similarity processing, the kindergartners were asked to make rhyme judgements on (pseudo) word targets that rhymed, phonologically overlapped or were unrelated to (pseudo) word primes. Results. Both a lexicality effect (pseudo-words were more difficult than words) and a global similarity effect (globally similar non-rhyming items were more difficult to reject than unrelated items) were observed. In addition, whereas in words the global similarity effect was only present in accuracy outcomes, in pseudo-words it was also observed in the response latencies. Furthermore, a large global similarity effect in pseudo-words correlated with a low score on short-term memory skills and grapheme knowledge. Conclusions. Increasing task demands led to a more detailed assessment of rhyme processing skills. Current assessment paradigms should therefore be extended with more demanding conditions. In light of the views on rhyme processing, we propose that a combination of global and analytical strategies is used to make a correct rhyme judgment.

Abstract

The relationship between the evoked responses (ERPs/ERFs) and the event-related changes in EEG/MEG power that can be observed during sentence-level language comprehension is as yet unclear. This study addresses a possible relationship between MEG power changes and the N400m component of the event-related field. Whole-head MEG was recorded while subjects listened to spoken sentences with incongruent (IC) or congruent (C) sentence endings. A clear N400m was observed over the left hemisphere, and was larger for the IC sentences than for the C sentences. A time–frequency analysis of power revealed a decrease in alpha and beta power over the left hemisphere in roughly the same time range as the N400m for the IC relative to the C condition. A linear regression analysis revealed a positive linear relationship between N400m and beta power for the IC condition, not for the C condition. No such linear relation was found between N400m and alpha power for either condition. The sources of the beta decrease were estimated in the LIFG, a region known to be involved in semantic unification operations. One source of the N400m was estimated in the left superior temporal region, which has been related to lexical retrieval. We interpret our data within a framework in which beta oscillations are inversely related to the engagement of task-relevant brain networks. The source reconstructions of the beta power suppression and the N400m effect support the notion of a dynamic communication between the LIFG and the left superior temporal region during language comprehension.

Abstract

Information structure facilitates communication between interlocutors by highlighting relevant information. It has previously been shown that information structure modulates the depth of semantic processing. Here we used event-related potentials to investigate whether information structure can modulate the depth of syntactic processing. In question-answer pairs, subtle (number agreement) or salient (phrase structure) syntactic violations were placed either in focus or out of focus through information structure marking. P600 effects to these violations reflect the depth of syntactic processing. For subtle violations, a P600 effect was observed in the focus condition, but not in the non-focus condition. For salient violations, comparable P600 effects were found in both conditions. These results indicate that information structure can modulate the depth of syntactic processing, but that this effect depends on the salience of the information. When subtle violations are not in focus, they are processed less elaborately. We label this phenomenon the Chomsky illusion.

Abstract

Gamma-band neuronal synchronization during sentence-level language comprehension has previously been linked with semantic unification. Here, we attempt to further narrow down the functional significance of gamma during language comprehension, by distinguishing between two aspects of semantic unification: successful integration of word meaning into the sentence context, and prediction of upcoming words. We computed event-related potentials (ERPs) and frequency band-specific electroencephalographic (EEG) power changes while participants read sentences that contained a critical word (CW) that was (1) both semantically congruent and predictable (high cloze, HC), (2) semantically congruent but unpredictable (low cloze, LC), or (3) semantically incongruent (and therefore also unpredictable; semantic violation, SV). The ERP analysis showed the expected parametric N400 modulation (HC < LC < SV). The time-frequency analysis showed qualitatively different results. In the gamma-frequency range, we observed a power increase in response to the CW in the HC condition, but not in the LC and the SV conditions. Additionally, in the theta frequency range we observed a power increase in the SV condition only. Our data provide evidence that gamma power increases are related to the predictability of an upcoming word based on the preceding sentence context, rather than to the integration of the incoming word’s semantics into the preceding context. Further, our theta band data are compatible with the notion that theta band synchronization in sentence comprehension might be related to the detection of an error in the language input.

Abstract

Many people speak a second language next to their mother tongue. How do they learn this language and how does the brain process it compared to the native language? A second language can be learned without explicit instruction. Our brains automatically pick up grammatical structures, such as word order, when these structures are repeated frequently during learning. The learning takes place within hours or days and the same brain areas, such as frontal and temporal brain regions, that process our native language are very quickly activated. When people master a second language very well, even the same neuronal populations in these language brain areas are involved. This is especially the case when the grammatical structures are similar. In conclusion, it appears that a second language builds on the existing cognitive and neural mechanisms of the native language as much as possible.

Abstract

Recent years have seen a large amount of empirical studies related to ‘embodied cognition’. While interesting and valuable, there is something dissatisfying with the current state of affairs in this research domain. Hypotheses tend to be underspecified, testing in general terms for embodied versus disembodied processing. The lack of specificity of current hypotheses can easily lead to an erosion of the embodiment concept, and result in a situation in which essentially any effect is taken as positive evidence. Such erosion is not helpful to the field and does not do justice to the importance of embodiment. Here we want to take stock, and formulate directions for how it can be studied in a more fruitful fashion. As an example we will describe few example studies that have investigated the role of sensori-motor systems in the coding of meaning (‘embodied semantics’). Instead of focusing on the dichotomy between embodied and disembodied theories, we suggest that the field move forward and ask how and when sensori-motor systems and behavior are involved in cognition.

Abstract

We carried out the first study on the relationship between individual language aptitude and structural connectivity of language pathways in the adult brain. We measured four components of language aptitude (vocabulary learning, VocL; sound recognition, SndRec; sound-symbol correspondence, SndSym; and grammatical inferencing, GrInf) using the LLAMA language aptitude test (Meara, 2005). Spatial working memory (SWM), verbal working memory (VWM) and IQ were also measured as control factors. Diffusion Tensor Imaging (DTI) was employed to investigate the structural connectivity of language pathways in the perisylvian language network. Principal Component Analysis (PCA) on behavioural measures suggests that a general ability might be important to the first stages of L2 acquisition. It also suggested that VocL, SndSy and SWM are more closely related to general IQ than SndRec and VocL, and distinguished the tasks specifically designed to tap into L2 acquisition (VocL, SndRec,SndSym and GrInf) from more generic measures (IQ, SWM and VWM). Regression analysis suggested significant correlations between most of these behavioural measures and the structural connectivity of certain language pathways, i.e., VocL and BA47-Parietal pathway, SndSym and inter-hemispheric BA45 pathway, GrInf and BA45-Temporal pathway and BA6-Temporal pathway, IQ and BA44-Parietal pathway, BA47-Parietal pathway, BA47-Temporal pathway and inter-hemispheric BA45 pathway, SWM and inter-hemispheric BA6 pathway and BA47-Parietal pathway, and VWM and BA47-Temporal pathway. These results are discussed in relation to relevant findings in the literature.

Abstract

In recent decades, neuroimaging studies on the neural infrastructure of language are usually (or mostly) conducted with certain on-line language processing tasks. These functional neuroimaging studies helped to localize the language areas in the brain and to investigate the brain activity during explicit language processing. However, little is known about what is going on with the language areas when the brain is ‘at rest’, i.e., when there is no explicit language processing running. Taking advantage of the fcMRI and DTI techniques, this thesis is able to investigate the language function ‘off-line’ at the neuronal network level and the connectivity among language areas in the brain. Based on patient studies, the traditional, classical model on the perisylvian language network specifies a “Broca’ area – Arcuate Fasciculus – Werinicke’s area” loop (Ojemann 1991). With the help of modern neuroimaging techniques, researchers have been able to track language pathways that involve more brain structures than are in the classical model, and relate them to certain language functions. In such a background, a large part of this thesis made a contribution to the study of the topology of the language networks. It revealed that the language networks form a topographical functional connectivity pattern in the left hemisphere for the right-handers. This thesis also revealed the importance of structural hubs, such as Broca’s and Wernicke’s areas, which have more connectivity to other brain areas and play a central role in the language networks. Furthermore, this thesis revealed both functionally and structurally lateralized language networks in the brain. The consistency between what is found in this thesis and what has been known from previous functional studies seems to suggest, that the human brain is optimized and ‘ready’ for the language function even when there is currently no explicit language-processing running.

Abstract

Semantic unification, the process by which small blocks of semantic information are combined into a coherent utterance, has been studied with various types of tasks. However, whether the brain activations reported in these studies are attributed to semantic unification per se or to other task-induced concomitant processes still remains unclear. The neural basis for semantic unification in sentence comprehension was examined using event-related potentials (ERP) and functional Magnetic Resonance Imaging (fMRI). The semantic unification load was manipulated by varying the goodness of fit between a critical word and its preceding context (in high cloze, low cloze and violation sentences). The sentences were presented in a serial visual presentation mode. The participants were asked to perform one of three tasks: semantic congruency judgment (SEM), silent reading for comprehension (READ), or font size judgment (FONT), in separate sessions. The ERP results showed a similar N400 amplitude modulation by the semantic unification load across all of the three tasks. The brain activations associated with the semantic unification load were found in the anterior left inferior frontal gyrus (aLIFG) in the FONT task and in a widespread set of regions in the other two tasks. These results suggest that the aLIFG activation reflects a semantic unification, which is different from other brain activations that may reflect task-specific strategic processing.

Abstract

This paper explores the expression of multiple entities in Turkish Sign Language (Türk İşaret Dili; TİD), a less well-studied sign language. It aims to provide a comprehensive description of the ways and frequencies in which entity plurality in this language is expressed, both within and outside the noun phrase. We used a corpus that includes both elicited and spontaneous data from native signers. The results reveal that most of the expressions of multiple entities in TİD are iconic, spatial strategies (i.e. localization and spatial plural predicate inflection) none of which, we argue, should be considered as genuine plural marking devices with the main aim of expressing plurality. Instead, the observed devices for localization and predicate inflection allow for a plural interpretation when multiple locations in space are used. Our data do not provide evidence that TİD employs (productive) morphological plural marking (i.e. reduplication) on nouns, in contrast to some other sign languages and many spoken languages. We relate our findings to expression of multiple entities in other signed languages and in spoken languages and discuss these findings in terms of modality effects on expression of multiple entities in human language.