Modality- and task-specific brain regions involved in Chinese lexical processing

fMRI was used to examine lexical processing in native adult Chinese speakers. A 2 task (semantics and phonology) x 2 modality (visual and auditory) within-subject design was adopted. The semantic task involved a meaning association judgment and the phonological task involved a rhyming judgment to two sequentially presented words. The overall effect across tasks and modalities was used to identify seven ROIs, including the left fusiform gyrus (FG), the left superior temporal gyrus (STG), the left ventral inferior frontal gyrus (VIFG), the left middle temporal gyrus (MTG), the left dorsal inferior frontal gyrus (DIFG), the left inferior parietal lobule (IPL), and the left middle frontal gyrus (MFG). ROI analyses revealed two modality-specific areas, FG for visual and STG for auditory, and three task-specific areas, IPL and DIFG for phonology and VIFG for semantics. Greater DIFG activation was associated with conflicting tonal information between words for the auditory rhyming task, suggesting this region's role in strategic phonological processing, and greater VIFG activation was correlated with lower association between words for both the auditory and the visual meaning task, suggesting this region's role in retrieval and selection of semantic representations. The modality- and task-specific effects in Chinese revealed by this study are similar to those found in alphabetical languages. Unlike English, we found that MFG was both modality- and task-specific, suggesting that MFG may be responsible for the visuospatial analysis of Chinese characters and orthography-to-phonology integration at a syllabic level

A brain-region-based meta-analysis method utilizing the Apriori algorithm

Background: Brain network connectivity modeling is a crucial method for studying the brain's cognitive functions. Meta-analyses can unearth reliable results from individual studies. Meta-analytic connectivity modeling is a connectivity analysis method based on regions of interest (ROIs) which showed that meta-analyses could be used to discover brain network connectivity. Results: In this paper, we propose a new meta-analysis method that can be used to find network connectivity models based on the Apriori algorithm, which has the potential to derive brain network connectivity models from activation information in the literature, without requiring ROIs. This method first extracts activation information from experimental studies that use cognitive tasks of the same category, and then maps the activation information to corresponding brain areas by using the automatic anatomical label atlas, after which the activation rate of these brain areas is calculated. Finally, using these brain areas, a potential brain network connectivity model is calculated based on the Apriori algorithm. The present study used this method to conduct a mining analysis on the citations in a language review article by Price (Neuroimage 62(2):816-847, 2012). The results showed that the obtained network connectivity model was consistent with that reported by Price. Conclusions: The proposed method is helpful to find brain network connectivity by mining the co-activation relationships among brain regions. Furthermore, results of the co-activation relationship analysis can be used as a priori knowledge for the corresponding dynamic causal modeling analysis, possibly achieving a significant dimension-reducing effect, thus increasing the efficiency of the dynamic causal modeling analysis

Temporal relation between top-down and bottom-up processing in lexical tone perception

Speech perception entails both top-down processing that relies primarily on language experience and bottom-up processing that depends mainly on instant auditory input. Previous models of speech perception often claim that bottom-up processing occurs in an early time window, whereas top-down processing takes place in a late time window after stimulus onset. In this paper, we evaluated the temporal relation of both types of processing in lexical tone perception. We conducted a series of event-related potential (ERP) experiments that recruited Mandarin participants and adopted three experimental paradigms, namely dichotic listening, lexical decision with phonological priming, and semantic violation. By systematically analyzing the lateralization patterns of the early and late ERP components that are observed in these experiments, we discovered that: auditory processing of pitch variations in tones, as a bottom-up effect, elicited greater right hemisphere activation; in contrast, linguistic processing of lexical tones, as a top-down effect, elicited greater left hemisphere activation. We also found that both types of processing co-occurred in both the early (around 200 ms) and late (around 300–500 ms) time windows, which supported a parallel model of lexical tone perception. Unlike the previous view that language processing is special and performed by dedicated neural circuitry, our study have elucidated that language processing can be decomposed into general cognitive functions (e.g., sensory and memory) and share neural resources with these functions.published_or_final_versio

Common and segregated neural substrates for automatic conceptual and affective priming as revealed by event-related functional magnetic resonance imaging

The brain activity associated with automatic semantic priming has been extensively studied. Thus far there has been no prior study that directly contrasts the neural mechanisms of semantic and affective priming. The present study employed event-related fMRI to examine the common and distinct neural bases underlying conceptual and affective priming with a lexical decision task. A special type of emotional word. a dual-meaning word containing both conceptual meaning and affective meaning, was adopted as target. Short stimulus onset asynchrony (SOA) (50 ms) was used to emphasize automatic processing. Fifteen participants were scanned in the present study. We found that the left middle/superior temporal gyrus was the brain region involved in both automatic conceptual and affective priming effects, suggesting general lexical-semantic processing that share in the two types of priming. The left inferior frontal gyrus and right superior temporal gyrus were found to be the conceptual-specific areas in automatic priming effect, consistent with the role of these areas in more extensive within-category semantic processes. The results also revealed that the left fusiform gyrus and left insula were the affective-specific regions in automatic priming effect, demonstrating the involvement of the left fusiform gyrus in automatic affective priming effect, and clarifying the role of the insula in emotional processing rather than conceptual processing. Despite comparable behavioral effects of automatic conceptual priming and affective priming, the present study revealed a neural dissociation of the two types of priming, as well as the shared neural bases

Visual and auditory vocabulary acquisition in learning Chinese as a second language : the impact of modality-specific working memory training

The global aim of this thesis was to investigate underlying working memory processes and neural correlates of visual and auditory vocabulary acquisition in Chinese. As an additional question and pre-condition for examining the main goal I questioned whether visual working memory can be trained separately from auditory and whether intra-modal can be distinguished from across-modal training effects in visual working memory on the behavioral and on the neural level. The Working Memory Training Study was designed to test whether visual working memory processes can be trained specifically on the behavioral and neural level and whether those effects can be separated from across-modal training effect. Decidedly larger training gains after visual working memory training compared with auditory or no training on a visual 2-back task were found. These effects were accompanied by specific training-related decreases in the right middle frontal gyrus arising from visual training only. Likewise, visual and auditory training led to decreased activations in the superior portion of the right middle frontal gyrus and the right posterior parietal lobule. I infer that the combination of effects resulted from increased neural efficiency of intra-modal (visual) processes on the one hand and of across-modal (general control) processes on the other hand. Therefore, visual processes of working memory can be trained specifically, and these effects can be functionally dissociated from alterations in general control processes common to both working memory trainings. These results offered a good starting point to use the training paradigm in the Language Training Study. As exemplified for the visual modality, the working memory training paradigm was successful in training a modality-specific process. Thus, the paradigm was applicable to investigate different transfer effects of visual and auditory working memory training on visual and auditory vocabulary learning in Chinese. The Language Training Study aimed at investigating whether visual working memory training exerts unique influence on learning Chinese visual words (orthographic learning) due to the greater complexity of the Chinese writing system, and, conversely, whether auditory working memory training has a specific impact on learning Chinese auditory words (phonological learning). In addition, training induced modulations in language-related brain networks were examined using fMRI in a pretest-training-posttest design. Both working memory trainings led to positive transfer effects on orthographic learning as compared to no training, whereas for phonological learning no transfer effects were obtained. Differential activation changes after visual and auditory working memory training were found in areas engaged in visual and auditory word processing: Activation sustained/decreased after intra-modal (visual) training in the left mid-fusiform gyrus in the orthographic task. Similarly, activation decreased after intra-modal (auditory) training in the anterior insula in the phonological task. These findings are consistent with the view that working memory training in the equivalent modality enhances the efficiency of perceptual encoding in the orthographic task and incorporating novel sound patterns into long-term phonological representations in the phonological task. Surprisingly, activation increases after across-modal training emerged in both tasks within the same brain regions: Activation increased after auditory training in the mid-fusiform gyrus in the orthographic task and likewise after visual training in the anterior insula in the phonological task, suggesting that working memory training in the complementary modality reflects selective attention to the respective tasks presumably guided by modality-unspecific improvements in executive components of working memory. Moreover, visual training led to additional recruitment of brain regions in the orthographic task, i.e. the right precuneus, presumably mirroring the generation of a mental visual image of the to-be-retrieved character.Das Ziel dieser Arbeit war es zugrundeliegende Arbeitsgedächtnisprozesse und neuronale Korrelate visuellen und auditiven Vokabellernens im Chinesischen zu untersuchen. Als zusätzliche Fragestellung und Voraussetzung um der Hauptforschungsfrage nachzugehen wurde außerdem untersucht, ob visuelles Arbeitsgedächtnis separat von auditivem trainiert werden kann und ob intra-modale von cross-modalen Trainingseffekten auf der Verhaltens- und der neuralen Ebene unterschieden werden können. In der Arbeitsgedächtnistrainingsstudie wurde getestet, ob visuelle Arbeitsgedächtnisprozesse auf der Verhaltens- und der neuronalen Ebene spezifisch trainiert werden und ob solche Effekte von cross-modalen Trainingseffekten separiert werden können. In einer visuellen 2-back Aufgabe zeigten sich deutlich größere Leistungszuwächse nach visuellem im Vergleich zu auditivem oder keine Training. Diese Effekte gingen mit spezifischen trainingsinduzierten Aktivierungsreduktionen im rechten Gyrus frontalis medius einher, die nur auf das visuelle Training zurückgingen. In gleicher Weise führten visuelles und auditives Training zu Aktivierungsreduktionen im superioren Teil des rechten Gyrus frontalis medius und im rechten superioren Parietallappen. Ich schließe daraus, dass die Kombination dieser Effekte durch erhöhte neuronale Effizienz intra-modaler (visueller) Prozesse einerseits und cross-modaler (genereller Kontroll-) Prozesse andererseits zustande kamen. Folglich scheinen visuelle Arbeitsgedächtnisprozesse spezifisch trainierbar zu sein und können funktionell von Veränderungen in generellen Kontrollprozessen, die beide Arbeitsgedächtnistraining gleichermaßen zeigten, dissoziiert werden. Diese Ergebnisse waren einen gute Ausgangsbasis, um das Trainingsparadigma in der Sprachtrainingsstudie anzuwenden. Wie für die visuelle Modalität exemplarisch dargestellt, konnte mit dem Arbeitsgedächtnisparadigma erfolgreich ein modalitäts-spezifischer Prozess trainiert werden. Demnach war das Paradigma geeignet um unterschiedliche Transfereffekte des visuellen und auditiven Arbeitsgedächtnistrainings auf visuelles und auditives Vokabellernen im Chinesischen zu untersuchen. Mit der Sprachtrainingsstudie sollte untersucht werden, ob visuelles Arbeitsgedächtnistraining spezifisch das Lernen chinesischer visueller Wörter (orthographisches Lernen) aufgrund der hohen Komplexität des chinesischen Schriftsystems beeinflusst und in umgekehrter Weise, ob auditives Arbeitsgedächtnistraining spezifisch das Lernen chinesischer auditiver Wörter (phonologisches Lernen) verbessert. Darüber hinaus wurden trainingsinduzierte Aktivierungsveränderungen in sprachrelevanten Gehirnnetzwerken mittels funktioneller Magnetresonanztomographie in einem Pretest-Training-Posttest-Design untersucht. Beide Arbeitsgedächtnistrainings führten zu positiven Transfereffekten beim orthographischen Lernen im Vergleich zu keinem Arbeitsgedächtnistraining, während für phonologisches Lernen keine Transfereffekte gefunden wurden. Unterschiedliche Aktivierungsveränderungen nach visuellem und auditivem Arbeitsgedächtnistraining wurden in Arealen gefunden, die auch bei visueller und auditiver Wortverarbeitung rekrutiert werden: Die Aktivierung wurde nach intra-modalem (visuellem) Training in der orthographischen Aufgabe im linken Gyrus fusiformis aufrechterhalten bzw. fiel ab. In ähnlicher Weise fiel die Aktivierung nach intra-modalem (auditiven) Training in der phonologischen Aufgabe in der linken anterioren Insel ab. Diese Ergebnisse weisen darauf hin, dass Arbeitsgedächtnistraining in der äquivalenten Modalität die Effizienz perzeptuellen Enkodieren in der orthographischen Aufgabe und die Einspeicherung neuer Klangmuster in Langzeitgedächtnisrepräsentation in der phonologischen Aufgabe verstärkt hat. Überraschenderweise wurden Aktivierungserhöhungen nach cross-modalem Training innerhalb derselben Gehirnregionen gefunden: Die Aktivierung im Gyrus fusiformis nahm nach auditivem Training in der orthographischen Aufgabe zu genauso wie die Aktivierung in der anterioren Insel nach visuellem Training in der phonologischen Aufgabe. Dies weist darauf hin, dass Arbeitsgedächtnistraining in der komplementären Modalität zu selektiver Aufmerksamkeitsallokation auf die entsprechende Aufgabe führt, was vermutlich auf modalitätsunspezifische Verbesserungen in exekutiven Arbeitsgedächtnisprozessen zurückzuführen ist. Darüber hinaus führte visuelles Arbeitsgedächtnistraining zu einer zusätzlichen Rekrutierung von Hirnarealen in der orthographischen Aufgabe, dem rechten Precuneus, was wahrscheinlich die Generierung eines visuellen mentalen Bildes des abzurufenden Schriftzeichens widerspiegelt