Publications

Abstract

BACKGROUND: There is a growing interest in the study of the genetic origins of comorbidity, a direct consequence of the recent findings of genetic loci that are seemingly linked to more than one disorder. There are several potential causes for these shared regions of linkage, but one possibility is that these loci may harbor genes with manifold effects. The established genetic correlation between reading disability (RD) and attention-deficit/hyperactivity disorder (ADHD) suggests that their comorbidity is due at least in part to genes that have an impact on several phenotypes, a phenomenon known as pleiotropy. METHODS: We employ a bivariate linkage test for selected samples that could help identify these pleiotropic loci. This linkage method was employed to carry out the first bivariate genome-wide analysis for RD and ADHD, in a selected sample of 182 sibling pairs. RESULTS: We found evidence for a novel locus at chromosome 14q32 (multipoint LOD=2.5; singlepoint LOD=3.9) with a pleiotropic effect on RD and ADHD. Another locus at 13q32, which had been implicated in previous univariate scans of RD and ADHD, seems to have a pleiotropic effect on both disorders. 20q11 is also suggested as a pleiotropic locus. Other loci previously implicated in RD or ADHD did not exhibit bivariate linkage. CONCLUSIONS: Some loci are suggested as having pleiotropic effects on RD and ADHD, while others might have unique effects. These results highlight the utility of this bivariate linkage method to study pleiotropy.

Abstract

All accounts of communicative behaviour in general, and communicative strategies in particular, mention gesture1 in relation to language acquisition (cf. Faerch & Kasper 1983 for an overview). However, few attempts have been made to investigate how spoken language and spontaneous gesture combine to determine discourse referents. Referential gesture and referential discourse will be of particular interest, since communicative strategies in second language discourse often involve labelling problems.

This paper will focus on two issues:

1) Within a cognitive account of communicative strategies, gesture will be seen to be part of conceptual or analysis-based strategies, in that relational features in the referents are exploited;

2) It will be argued that communication strategies can be seen in terms of cue manipulation in the same sense as sentence processing has been analysed in terms of competing cues. Strategic behaviour, and indeed the process of referring in general, are seen in terms of cues, combining or competing to determine discourse referents. Gesture can then be regarded as being such a cue at the discourse level, and as a cue-based communicative strategy, in that gesture functions by exploiting physically based cues which can be recognised as being part of the referent. The question of iconicity and motivation vs. the arbitrary qualities of gesture as a strategic cue will be addressed in connection with this.

Abstract

Since listeners usually look at the speaker's face, gestural information has to be absorbed through peripheral visual perception. In the literature, it has been suggested that listeners look at gestures under certain circumstances: 1) when the articulation of the gesture is peripheral; 2) when the speech channel is insufficient for comprehension; and 3) when the speaker him- or herself indicates that the gesture is worthy of attention. The research here reported employs eye tracking techniques to study the perception of gestures in face-to-face interaction. The improved control over the listener's visual channel allows us to test the validity of the above claims. We present preliminary findings substantiating claims 1 and 3, and relate them to theoretical proposals in the literature and to the issue of how visual and cognitive attention are related.

Abstract

In speaking and comprehending language, word information is retrieved from memory and combined into larger units (unification). Unification operations take place in parallel at the semantic, syntactic and phonological levels of processing. This article proposes a new framework that connects psycholinguistic models to a neurobiological account of language. According to this proposal the left inferior frontal gyrus (LIFG) plays an important role in unification. Research in other domains of cognition indicates that left prefrontal cortex has the necessary neurobiological characteristics for its involvement in the unification for language. I offer here a psycholinguistic perspective on the nature of language unification and the role of LIFG.

Abstract

The central issue of this study concerns the claim that the processing of gender agreement in online sentence comprehension is a syntactic rather than a conceptual/semantic process. This claim was tested for the grammatical gender agreement in Dutch between the definite article and the noun. Subjects read sentences in which the definite article and the noun had the same gender and sentences in which the gender agreement was violated, While subjects read these sentences, their electrophysiological activity was recorded via electrodes placed on the scalp. Earlier research has shown that semantic and syntactic processing events manifest themselves in different event-related brain potential (ERP) effects. Semantic integration modulates the amplitude of the so-called N400.The P600/SPS is an ERP effect that is more sensitive to syntactic processes. The violation of grammatical gender agreement was found to result in a P600/SPS. For violations in sentence-final position, an additional increase of the N400 amplitude was observed. This N400 effect is interpreted as resulting from the consequence of a syntactic violation for the sentence-final wrap-up. The overall pattern of results supports the claim that the on-line processing of gender agreement information is not a content driven but a syntactic-form driven process.

Abstract

This study tests the recent claim that Broca’s aphasics are impaired in automatic lexical access, including the retrieval of word meaning. Subjects are required to perform a lexical decision on visually presented prime target pairs. Half of the word targets are preceded by a related word, half by an unrelated word. Primes and targets are presented with a long stimulus-onset-asynchrony (SOA) of 1400 msec and with a short SOA of 300 msec. Normal priming effects are observed in Broca’s aphasics for both SOAs. This result is discussed in the context of the claim that Broca’s aphasics suffer from an impairment in the automatic access of lexical–semantic information. It is argued that none of the current priming studies provides evidence supporting this claim, since with short SOAs priming effects have been reliably obtained in Broca’s aphasics. The results are more compatible with the claim that in many Broca’s aphasics the functional locus of their comprehension deficit is at the level of postlexical integration processes.

Abstract

Silent reading and reading aloud of German words and pseudowords were used in a PET study using (15O)butanol to examine the neural correlates of reading and of the phonological conversion of legal letter strings, with or without meaning.
The results of 11 healthy, right-handed volunteers in the age range of 25 to 30 years showed activation of the lingual gyri during silent reading in comparison with viewing a fixation cross. Comparisons between the reading of words and pseudowords suggest the involvement of the middle temporal gyri in retrieving both the phonological and semantic code for words. The reading of pseudowords activates the left inferior frontal gyrus, including the ventral part of Broca’s area, to a larger extent than the reading of words. This suggests that this area might be involved in the sublexical conversion of orthographic input strings into phonological output codes. (Pre)motor areas were found to be activated during both silent reading and reading aloud. On the basis of the obtained activation patterns, it is hypothesized that the articulation of high-frequency syllables requires the retrieval of their concomitant articulatory gestures from the SMA and that the articulation of lowfrequency syllables recruits the left medial premotor cortex.

Abstract

Morphology is the study of the internal structure of words. A vigorous ongoing debate surrounds the question of how such internal structure is best accounted for: by means of lexical entries and deterministic symbolic rules, or by means of probabilistic subsymbolic networks implicitly encoding structural similarities in connection weights. In this review, we separate the question of subsymbolic versus symbolic implementation from the question of deterministic versus probabilistic structure. We outline a growing body of evidence, mostly external to the above debate, indicating that morphological structure is indeed intrinsically graded. By allowing probability into the grammar, progress can be made towards solving some long-standing puzzles in morphological theory.

Abstract

We advance the hypothesis here that the higher-than-average vocal pitch (FO) found for speech of Broca's aphasics in experimental settings is due, in part, to increased psychological stress. Two experiments were conducted which manipulated conversational constraints and the sentence forms to be produced by aphasic patients. Our study revealed significant differences between changes in vocal pitch of agrammatic Broca's aphasics versus those of Wernicke's aphasics and normal controls. It is suggested that the greater psychological stress experienced by the Broca's aphasics, but not by the Wernicke's aphasics, accounts for these observed differences.

Abstract

When participants are presented simultaneously with spoken language and a visual display depicting objects to which that language refers, participants spontaneously fixate the visual referents of the words being heard [Cooper, R. M. (1974). The control of eye fixation by the meaning of spoken language: A new methodology for the real-time investigation of speech perception, memory, and language processing. Cognitive Psychology, 6(1), 84–107; Tanenhaus, M. K., Spivey-Knowlton, M. J., Eberhard, K. M., & Sedivy, J. C. (1995). Integration of visual and linguistic information in spoken language comprehension. Science, 268(5217), 1632–1634]. We demonstrate here that such spontaneous fixation can be driven by partial semantic overlap between a word and a visual object. Participants heard the word ‘piano’ when (a) a piano was depicted amongst unrelated distractors; (b) a trumpet was depicted amongst those same distractors; and (c), both the piano and trumpet were depicted. The probability of fixating the piano and the trumpet in the first two conditions rose as the word ‘piano’ unfolded. In the final condition, only fixations to the piano rose, although the trumpet was fixated more than the distractors. We conclude that eye movements are driven by the degree of match, along various dimensions that go beyond simple visual form, between a word and the mental representations of objects in the concurrent visual field.

Abstract

Stimulus-related changes in cerebral blood oxygenation were measured using high-resolution functional magnetic resonance imaging sequentially covering visual occipital areas in contiguous sections. During dynamic imaging, healthy subjects silently viewed pseudowords, single false fonts, or length-matched strings of the same false fonts. The paradigm consisted of a sixfold alternation of an activation and a control task. With pseudowords as activation vs single false fonts as control, responses were seen mainly in medial occipital cortex. These responses disappeared when pseudowords were alternated with false font strings as the control and reappeared when false font strings instead of pseudowords served as activation and were alternated with single false fonts. The string-length contrast alone, therefore, is sufficient to account for the activation pattern observed in medial visual cortex when word-like stimuli are contrasted with single characters.

Abstract

The aim of this paper is to discuss an inherent difficulty of PET (and fMRI) research in language production. On the one hand, language production presupposes some degree of freedom for the subject, on the other hand, interpretability of results presupposes restrictions of this freedom. This difficulty is reflected in the existing PET literature in some neglect of the general principle to design experiments in such a way that the results do not allow for alternative interpretations. It is argued that by narrowing down the scope of experiments a gain in interpretability can be achieved.

Abstract

Clahsen's characterization of nondefault inflection as based exclusively on lexical entries does not capture the full range of empirical data on German inflection. In the verb system differential effects of lexical frequency seem to be input-related rather than affecting morphological production. In the noun system, the generalization properties of -n and -e plurals exceed mere analogy-based productivity.

Abstract

In 7 experiments the authors investigated the locus of word frequency effects in speech production. Experiment 1 demonstrated a frequency effect in picture naming that was robust over repetitions. Experiments 2, 3, and 7 excluded contributions from object identification and initiation of articulation. Experiments 4 and 5 investigated whether the effect arises in accessing the syntactic word (lemma) by using a grammatical gender decision task. Although a frequency effect was found, it dissipated under repeated access to word's gender. Experiment 6 tested whether the robust frequency effect arises in accessing the phonological form (lexeme) by having Ss translate words that produced homophones. Low-frequent homophones behaved like high-frequent controls, inheriting the accessing speed of their high-frequent homophone twins. Because homophones share the lexeme, not the lemma, this suggests a lexeme-level origin of the robust effect.

Abstract

This study investigates the time-course of information processing in both visual as well as in the auditory speech as used for word identification in face-to-face communication. It extends the limited previous research on this topic and provides a valuable database for future research in audiovisual speech perception. An evaluation of models of speech perception by ear and eye in their ability to account for the audiovisual gating data shows a superior role of the fuzzy logical model of perception (FLMP) [1] over additive models of perception. A new dynamic version of the FLMP seems to be a promising model to account for the complex interplay of perceptual and cognitive information in audiovisual spoken word recognition.

Abstract

In face-to-face communication, information from the face as well as from the voice contributes to the identification of spoken words. This dissertation investigates the time-course of the evaluation and integration of visual and auditory speech in audiovisual word identification. A large-scale audiovisual gating study extends previous research on this topic by (1) using a set of words that includes all possible initial consonants in English in three vowel contexts, (2) tracking the information processing for individual words not only across modalities, but also over time, and (3) testing quantitative models of the time-course of multimodal word recognition. There was an advantage in accuracy for audiovisual speech over auditory-only and visual-only speech. Auditory performance was, however, close to ceiling while performance on visual-only trials was near the floor of the scale, but well above chance. Visual information was used at all gates to identify the presented words. Information theoretic feature analyses of the confusion matrices revealed that the auditory signal is highly informative about voicing, manner, frication, duration, and place of articulation. Visual speech is mostly informative about place of articulation, but also about frication and duration. The auditory signal provides more information about the place of articulation for back consonants, whereas the visual signal provides more information for the labial consonants. The data were sufficient to discriminate between models of audiovisual word recognition. The Fuzzy Logical Model of Perception (FLMP; Massaro, 1998) gave a better account of the confusion matrix data than additive models of perception. A dynamic version of the FLMP was expanded to account for the evaluation and integration of information over time. This dynamic FLMP provided a better description of the data than dynamic additive competitor models. The present study builds a good foundation to investigate the role of the complex interplay between stimulus information and the structure of the lexicon. It provides an important step in building a formal representation of a lexical dynamic FLMP that can account not only for the time-course of speech information and its perceptual processing, but also for lexical influences.

Abstract

Mutations of the epidermal growth factor receptor (EGFR) gene are found at a relatively high frequency in glioma, with the most common being the de2-7 EGFR (or EGFRvIII). This mutation arises from an in-frame deletion of exons 2–7, which removes 267 amino acids from the extracellular domain of the receptor. Despite being unable to bind ligand, the de2-7 EGFR is constitutively active at a low level. Transfection of human glioma cells with the de2-7 EGFR has little effect in vitro, but when grown as tumor xenografts this mutated receptor imparts a dramatic growth advantage. We have now mapped the phosphorylation pattern of de2-7 EGFR, both in vivo and in vitro, using a panel of antibodies unique to the different phosphorylated tyrosine residues. Phosphorylation of de2-7 EGFR was detected constitutively at all tyrosine sites surveyed both in vitro and in vivo, including tyrosine 845, a known target in the wild-type EGFR for src kinase. There was a substantial upregulation of phosphorylation at every tyrosine residue of the de2-7 EGFR when cells were grown in vivo compared to the receptor isolated from cells cultured in vitro. Upregulation of phosphorylation could be mimicked in vitro by the addition of specifi c components of the ECM such as collagen via an integrin-dependent mechanism. Since this increase in in vivo phosphorylation enhances de2-7 EGFR signaling, this observation explains why the growth enhancement mediated by de2-7 EGFR is largely restricted to the in vivo environment. In a second set of experiments we analyzed the interaction between EGFRvIII and ErbB2. Co-expression of these proteins in NR6 cells, a mouse fi broblast line devoid of ErbB family members, dramatically enhanced in vivo tumorigenicity of these cells compared to cells expressing either protein alone. Detailed analysis of these xenografts demonstrated that EGFRvIII could heterodimerize and transphosphorylate the ErbB2. Since both EGFRvIII and ErbB2 are commonly expressed at gliomas, this data suggests that the co-expression of these two proteins may enhance glioma tumorigenicity.

Abstract

Retaining detailed representations of unstressed syllables is a logical prerequisite for infants' use of probabilistic phonotactics to segment iambic words from fluent speech. The head-turn preference study was used to investigate the nature of English- learners' representations of iambic word onsets. Fifty-four 10.5-month-olds were familiarized to passages containing the nonsense iambic word forms ginome and tupong. Following familiarization, infants were either tested on familiar (ginome and tupong) or near-familiar (pinome and bupong) versus unfamiliar (kidar and mafoos) words. Infants in the familiar test group (familiar vs. unfamiliar) oriented significantly longer to familiar than unfamiliar test items, whereas infants in the near-familiar test group (near-familiar vs. unfamiliar) oriented equally long to near-familiar and unfamiliar test items. Our results provide evidence that infants retain fairly detailed representations of unstressed syllables and therefore support the hypothesis that infants use phonotactic cues to find words in fluent speech.

Abstract

Day-to-day interpretations of “space” are enmeshed in specific cultural and linguistic practices. For example, many cultures have an association between vertical height and social standing; more powerful people may be placed literally higher than others at social gatherings, and be spoken of as having higher status. This questionnaire is a guide for exploring relationships between space, language, and social structure. The goal is to better understand how space is organised in the focus community, and to investigate the extent to which space is used as a model for reproducing social forms.

Abstract

Comments on a study by Frazier and others on Dutch-language lexical processing. Claims that the control condition in the experiment was inadequate and that an assumption made by Frazier about closed class verbal items is inaccurate, and proposes an alternative account of a subset of the data from the experiment

Abstract

Raises objections to L. Frazier et al's (see record 1994-32229-001) report of an experimental study intended to test Schreuder's (1990) Morphological Integration (MI) model concerning the processing of separable and inseparable verbs and shows that the logic of the experiment is flawed. The problem is rooted in the notion of a separable complex verb. The conclusion is drawn that Frazier et al's experimental data cannot be taken as evidence for the theoretical propositions they develop about the MI model.

Abstract

[Seven one-page psycholinguistic sketches]

Abstract

Previous work has shown that Dutch listeners use prosodic information in the speech signal to optimise morphological processing: Listeners are sensitive to prosodic differences between a noun stem realised in isolation and a noun stem realised as part of a plural form (in which the stem is followed by an unstressed syllable). The present study, employing a lexical decision task, provides an additional demonstration of listeners' sensitivity to prosodic cues in the stem. This sensitivity is shown for two languages that differ in morphological productivity: Dutch and English. The degree of morphological productivity does not correlate with listeners' sensitivity to prosodic cues in the stem, but it is reflected in differential sensitivities to the word-specific log odds ratio of encountering an unshortened stem (i.e., a stem in isolation) versus encountering a shortened stem (i.e., a stem followed by a suffix consisting of one or more unstressed syllables). In addition to being sensitive to the prosodic cues themselves, listeners are also sensitive to the probabilities of occurrence of these prosodic cues.

Abstract

It has recently been shown that listeners use systematic differences in vowel length and intonation to resolve ambiguities between onset-matched simple words (Davis, Marslen-Wilson, & Gaskell, 2002; Salverda, Dahan, & McQueen, 2003). The present study shows that listeners also use prosodic information in the speech signal to optimize morphological processing. The precise acoustic realization of the stem provides crucial information to the listener about the morphological context in which the stem appears and attenuates the competition between stored inflectional variants. We argue that listeners are able to make use of prosodic information, even though the speech signal is highly variable within and between speakers, by virtue of the relative invariance of the duration of the onset. This provides listeners with a baseline against which the durational cues in a vowel and a coda can be evaluated. Furthermore, our experiments provide evidence for item-specific prosodic effects.

Abstract

In Dutch, high-frequency words with the suffix -lijk are often highly reduced in spontaneous unscripted speech. This study addressed socio-geographic variation in the reduction of such words against the backdrop of the variation in their use in written and spoken Dutch. Multivariate analyses of the frequencies with which the words were used in a factorially contrasted set of subcorpora revealed signi ficant variation involving the speaker's country, sex, and education level for spoken Dutch, and involving country and register for written Dutch. Acoustic analyses revealed that Dutch men reduced most often, while Flemish highly educated women reduced least. Two linguistic context effects emerged, one prosodic, and the other pertaining to the flow of information. Words in sentence final position showed less reduction, while words that were better predictable from the preceding word in the sentence(based on mutual information) tended to be reduced more often. The increased probability of reduction for forms that are more predictable in context, combined with the loss of the suffix in the more extremely reduced forms, suggests that highfrequency words in -lijk are undergoing a process of erosion that causes them to gravitate towards monomorphemic function words.

Abstract

This paper reports on an investigation of children's (aged 3;5–9;8) comprehension of sentences containing ambiguity of prepositional phrase (PP) attachment. Results from a picture selection study (N=90) showed that children use verb semantics and preposition type to resolve the ambiguity, with older children also showing sensitivity to the definiteness of the object NP as a cue to interpretation. Study 2 investigated three- and five-year-old children's (N=47) ability to override an instrumental interpretation of ambiguous PPs in order to process attributes of the referential scene. The results showed that while five-year-olds are capable of incorporating aspects of the referential scene into their interpretations, three-year-olds are not as successful. Overall, the results suggest that children are attuned very early to the lexico-semantic co-occurrences that have been shown to aid ambiguity resolution in adults, but that more diffuse cues to interpretation are used only later in development