The neurocognitive signature of focus alternatives

Focus alternatives are words/phrases that can substitute for the focused constituent of an utterance. In "Carsten has picked [CHERRIES]_F from the tree.", (marked by pitch focus on cherries), the speaker wants to not only convey the fact that Carsten has picked cherries, but also to contrast cherries with other fruit that could have been picked, such as plums. Although focus alternatives are key to understanding the implicit aspects of an utterance, nothing is known about their neural representation. We directly contrasted neural representations of lexico-semantic similarity and focus alternative status using fMRI. Semantic relatedness was reflected in decreased activation in the bilateral superior temporal gyri. By contrast, processing of focus alternatives induced increased activations in the precuneus and the fronto-median wall, two regions previously implicated in discourse processing. These results suggest that focus alternative status is processed separately from semantic relatedness, at the level of discourse integration.

Activation Patterns throughout the Word Processing Network of L1-dominant Bilinguals Reflect Language Similarity and Language Decisions

A crucial aspect of bilingual communication is the ability to identify the language of an input. Yet, the neural and cognitive basis of this ability is largely unknown. Moreover, it cannot be easily incorporated into neuronal models of bilingualism, which posit that bilinguals rely on the same neural substrates for both languages and concurrently activate them even in monolingual settings. Here we hypothesized that bilinguals can employ language-specific sublexical (bigram frequency) and lexical (orthographic neighborhood size) statistics for language recognition. Moreover, we investigated the neural networks representing language-specific statistics and hypothesized that language identity is encoded in distributed activation patterns within these networks. To this end, German-English bilinguals made speeded language decisions on visually presented pseudowords during fMRI. Language attribution followed lexical neighborhood sizes both in first (L1) and second (L2) language. RTs revealed an overall tuning to L1 bigram statistics. Neuroimaging results demonstrated tuning to L1 statistics at sublexical (occipital lobe) and phonological (temporoparietal lobe) levels, whereas neural activation in the angular gyri reflected sensitivity to lexical similarity to both languages. Analysis of distributed activation patterns reflected language attribution as early as in the ventral stream of visual processing. We conclude that in language-ambiguous contexts visual word processing is dominated by L1 statistical structure at sublexical orthographic and phonological levels, whereas lexical search is determined by the structure of both languages. Moreover, our results demonstrate that language identity modulates distributed activation patterns throughout the reading network, providing a key to language identity representations within this shared network.

Listening to Puns Elicits the Co-Activation of Alternative Homophone Meanings during Language Production

Recent evidence suggests that lexical-semantic activation spread during language production can be dynamically shaped by contextual factors. In this study we investigated whether semantic processing modes can also affect lexical-semantic activation during word production. Specifically, we tested whether the processing of linguistic ambiguities, presented in the form of puns, has an influence on the co-activation of unrelated meanings of homophones in a subsequent language production task. In a picture-word interference paradigm with word distractors that were semantically related or unrelated to the non-depicted meanings of homophones we found facilitation induced by related words only when participants listened to puns before object naming, but not when they heard jokes with unambiguous linguistic stimuli. This finding suggests that a semantic processing mode of ambiguity perception can induce the co-activation of alternative homophone meanings during speech planning.

Processing different kinds of semantic relations in picture-word interference with non-masked and masked distractors

Spoken production requires lexical selection, guided by the conceptual representation of the to-be-named target. Currently, the question whether lexical selection is subject to competition is hotly debated. In the picture-word interference task, manipulating the visibility of written distractor words provides important insights: clearly visible categorically related distractors cause interference whereas masked distractors induce facilitation (Finkbeiner and Caramazza, 2006). Now you see it, now you don't: On turning semantic interference into facilitation in a Stoop-like task. We explored the effect of distractor masking in more depth by investigating its interplay with different types of semantic overlap. Specifically, we contrasted categorical with associatively based relatedness. For the former, we replicated the polarity reversal in semantic effects dependent on whether distractors were masked or not. Post-experimental visibility tests showed that weak semantic facilitation with masked distractors did not depend on individual variability in participants' ability to perceive the distractors. Associatively related distractors showed facilitation with non-masked presentation, but little effect when masked. Overall, the results suggest that it is primarily distractor activation strength which determines whether semantic effects are facilitatory or interfering in PWI tasks.

Context updating during sentence comprehension: the effect of aboutness topic

To communicate efficiently, speakers typically link their utterances to the discourse environment and adapt their utterances to the listener's discourse representation. Information structure describes how linguistic information is packaged within a discourse to optimize information transfer. The present study investigates the nature and time course of context integration (i.e., aboutness topic vs. neutral context) on the comprehension of German declarative sentences with either subject-before-object (SO) or object-before-subject (OS) word order using offline comprehensibility judgments and online event-related potentials (ERPs). Comprehensibility judgments revealed that the topic context selectively facilitated comprehension of stories containing OS (i.e., non-canonical) sentences. In the ERPs, the topic context effect was reflected in a less pronounced late positivity at the sentence-initial object. In line with the Syntax-Discourse Model, we argue that these context-induced effects are attributable to reduced processing costs for updating the current discourse model. The results support recent approaches of neurocognitive models of discourse processing.

The association of the BDNF Val66Met polymorphism and the hippocampal volumes in healthy humans: a joint meta-analysis of published and new data

BACKGROUND

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (refSNP Cluster Report: rs6265) is a common and functionally relevant single nucleotide polymorphism (SNP). The gene itself, as well as the SNP rs6265, have been implicated in hippocampal learning and memory. However, imaging genetic studies have produced controversial results about the impact of this SNP on hippocampal volumes in healthy subjects.

METHODS

We examined the association between the rs6265 polymorphism and hippocampal volume in 643 healthy young subjects using automatic segmentation and subsequently included these data in a meta-analysis based on published studies with 5298 healthy subjects in total.

RESULTS

We found no significant association between SNP rs6265 and hippocampal volumes in our sample (g=0.05, p=0.58). The meta-analysis revealed a small, albeit significant difference in hippocampal volumes between genotype groups, such that Met-carriers had slightly smaller hippocampal volumes than Val/Val homozygotes (g=0.09, p=0.04), an association that was only evident when manual (g=0.22, p=0.01) but not automatic tracing approaches (g=0.04, p=0.38) were used. Studies using manual tracing showed evidence for publication bias and a significant decrease in effect size over the years with increasing sample sizes.

CONCLUSIONS

This study does not support the association between SNP rs6265 and hippocampal volume in healthy individuals. The weakly significant effect observed in the meta-analysis is mainly driven by studies with small sample sizes. In contrast, our original data and the meta-analysis of automatically segmented hippocampal volumes, which was based on studies with large samples sizes, revealed no significant genotype effect. Thus, meta-analyses of the association between rs6265 and hippocampal volumes should consider possible biases related to measuring technique and sample size.

A genome-wide survey and functional brain imaging study identify CTNNBL1 as a memory-related gene

Unbiased genome-wide screens combined with imaging data on brain function may identify novel molecular pathways related to human cognition. Here we performed a dense genome-wide screen to identify episodic memory-related gene variants. A genomic locus encoding the brain-expressed beta-catenin-like protein 1 (CTNNBL1) was significantly (P=7 × 10(-8)) associated with verbal memory performance in a cognitively healthy cohort from Switzerland (n=1073) and was replicated in a second cohort from Serbia (n=524; P=0.003). Gene expression studies showed CTNNBL1 genotype-dependent differences in beta-catenin-like protein 1 mRNA levels in the human cortex. Functional magnetic resonance imaging in 322 subjects detected CTNNBL1 genotype-dependent differences in memory-related brain activations. Converging evidence from independent experiments and different methodological approaches suggests a role for CTNNBL1 in human memory.

Does word length affect speech onset latencies when producing single words?

Most models of spoken production predict that shorter utterances should be initiated faster than longer ones. However, whether word-length effects in single word production exist is at present controversial. A series of experiments did not find evidence for such an effect. First, an experimental manipulation of word length in picture naming showed no latency differences. Second, Dutch and English speakers named 2 sets of either objects or words (monosyllabic names in Dutch and disyllabic names in English or vice versa). A length effect, which should manifest itself as an interaction between object set and response language, emerged in word naming but not in picture naming. Third, distractors consisting of the final syllable of disyllabic object names speeded up responses, but at the same time, no word-length effect was found. These results suggest that before the response is initiated, an entire word has been phonologically encoded, but only its initial syllable is placed in an articulatory buffer.

A genetic variation of the noradrenergic system is related to differential amygdala activation during encoding of emotional memories

Emotionally arousing events are typically well remembered, but there is a large interindividual variability for this phenomenon. We have recently shown that a functional deletion variant of ADRA2B, the gene encoding the alpha2b-adrenergic receptor, is related to enhanced emotional memory in healthy humans and enhanced traumatic memory in war victims. Here, we investigated the neural mechanisms of this effect in healthy participants by using fMRI. Carriers of the ADRA2B deletion variant exhibited increased activation of the amygdala during encoding of photographs with negative emotional valence compared with noncarriers of the deletion. Additionally, functional connectivity between amygdala and insula was significantly stronger in deletion carriers. The present findings indicate that the ADRA2B deletion variant is related to increased responsivity and connectivity of brain regions implicated in emotional memory.

A purple giraffe is faster than a purple elephant: inconsistent phonology affects determiner selection in English

The form of a determiner is dependent on different contextual factors: in some languages grammatical number and grammatical gender determine the choice of a determiner variant. In other languages, the phonological onset of the element immediately following the determiner affects selection, too. Previous work has shown that the activation of opposing determiner forms by a noun's grammatical properties leads to slower naming latencies in a picture naming task, as does the activation of opposing forms by the interaction between a noun's gender and the phonological context. The present paper addresses the question of whether phonological context alone is sufficient to evoke competition between determiner forms. Participants produced English phrases in which a noun phrase's phonology required a determiner that was the same as or differed from the determiner required by the noun itself (e.g., apurple giraffe; an orange giraffe). Naming latencies were slower when the phrase-initial determiner differed from the determiner required by the noun in isolation than when the phrase-initial determiner matched the isolated-noun determiner. This was true both for definite and indefinite determiners. The data show that during the production of a determiner-noun phrase, nouns automatically activate the phonological forms of their determiners, which can compete with the phonological forms that are generated by an assimilation rule.

Task-dependent semantic interference in language production: an fMRI study

We used fMRI to investigate competition during language production in two word production tasks: object naming and color naming of achromatic line drawings. Generally, fMRI activation was higher for color naming. The line drawings were followed by a word (the distractor word) that referred to either the object, a related object, or an unrelated object. The effect of the distractor word on the BOLD response was qualitatively different for the two tasks. The activation pattern suggests two different kinds of competition during lexical retrieval: (1) Task-relevant responses (e.g., red in color naming) compete with task-irrelevant responses (i.e., the object's name). This competition effect was dominant in prefrontal cortex. (2) Multiple task-relevant responses (i.e., target word and distractor word) compete for selection. This competition effect was dominant in ventral temporal cortex. This study provides further evidence for the distinct roles of frontal and temporal cortex in language production, while highlighting the effects of competition, albeit from different sources, in both regions.

Phonological regularities and grammatical gender retrieval in spoken word recognition and word production

Two experiments investigate whether native speakers of French can use a noun's phonological ending to retrieve its gender and that of a gender-marked element. In Experiment 1, participants performed a gender decision task on the noun's gender-marked determiner for auditorily presented nouns. Noun endings with high predictive values were selected. The noun stimuli could either belong to the gender class predicted by their ending (congruent) or they could belong to the gender class that was different from the predicted gender (incongruent). Gender decisions were made significantly faster for congruent nouns than for incongruent nouns, relative to a (lexical decision) baseline task. In Experiment 2, participants named pictures of the same materials as used in Experiment 1 with noun phrases consisting of a gender-marked determiner, a gender-marked adjective and a noun. In this Experiment, no effect of congruency, relative to a (bare noun naming) baseline task, was observed. Thus, the results show an effect of phonological information on the retrieval of gender-marked elements in spoken word recognition, but not in word production.