More bilateral, more anterior: Alterations of brain organization in the large-scale structural network in Chinese dyslexia.

Abnormalities in large-scale brain networks have been recently reported in dyslexia; however, it remains unclear whether these abnormalities are congenital (due to dyslexia per se) or arise later in development. Here, structural magnetic resonance imaging data of 17 Chinese reading disabled (RD) and 17 age-matched typically developing (TD) children were used to construct cortical thickness (sensitive to postnatal development) and surface area (sensitive to prenatal development) networks. In the thickness network, compared to TD, RD showed reduced nodal network properties (e.g., degree and betweenness) in the left hemisphere along with enhanced nodal properties mainly in the right hemisphere. As for the surface area network, compared to TD, RD demonstrated lower nodal properties in the posterior brain regions and higher nodal properties in the anterior brain regions. Furthermore, hubs in both the thickness and surface area networks in RD were more distributed in frontal areas and less distributed in parietal areas, whereas TD showed the opposite pattern. Altogether, these findings indicate that the aberrant structural connectivity in the dyslexic individuals was not only due to a late developmental effect reflected in the altered thickness network, but may also be a congenital effect during prenatal development, reflected in the altered surface network.

The dynamic nature of assimilation and accommodation procedures in the brains of Chinese-English and English-Chinese bilinguals.

The framework of assimilation and accommodation has been proposed to explain the brain mechanisms supporting second language reading acquisition (Perfetti et al. [2007]: Bilingual Lang Cogn 10:131). Assimilation refers to using the procedures of the native language network in the acquisition of a new writing system, whereas accommodation refers to using second language procedures for reading the newly acquired writing system. We investigated assimilation and accommodation patterns in the brains of bilingual individuals by recruiting a group of Chinese-English bilinguals and a group of English-Chinese bilinguals to perform lexical decision tasks in both English and Chinese. The key question was whether the assimilation/accommodation procedures supporting second language reading in the brains of Chinese-English and English-Chinese bilinguals were dynamic, i.e., modulated by proficiency in the second language and perceptual features of the second language's script. Perceptual features of the scripts were manipulated through orthographic degradation by inserting spaces between the radicals of a Chinese character or between the syllables of an English word. This manipulation disrupts the visual configuration of the orthography but does not change its more fundamental design principles. We found that for English-Chinese bilinguals, higher proficiency was associated with greater accommodation, suggesting that the accommodation procedure in a bilingual individual's brain is modulated by second language proficiency. Most interestingly, we found that the assimilation/accommodation effects vanished or diminished when orthographically degraded scripts were processed by both Chinese-English and English-Chinese bilinguals, suggesting that the assimilation/accommodation procedures in a bilingual individual's brain are modulated by perceptual features of orthography. This work therefore offers a new, dynamic perspective for our understanding of the assimilation/accommodation framework for second language acquisition.

Altered intra- and inter-regional synchronization of superior temporal cortex in deaf people.

Functional organization of the brain can be fundamentally altered by auditory deprivation. Previous studies found that the superior temporal cortex in deaf people is reorganized to process non-auditory stimuli, as revealed by the extrinsic task-induced brain activities. However, it is unknown how the intrinsic activities of this region are impacted by deafness. This study explored this issue using resting-state functional magnetic resonance imaging. We examined 60 congenitally deaf (CD) individuals, 39 acquired deaf (AD) individuals, and 38 hearing controls (HC), and focused on the effect of deafness on the intra- and inter-regional synchronization of different parts of superior temporal sulcus (STS). We found that intra-regional synchronization or regional homogeneity (ReHo) of the middle STS (mSTS) was decreased in AD compared with HC or CD, while the CD had preserved ReHo in mSTS. Greater connectivity was observed between mSTS and posterior STS in CD and HC than in AD, while both CD and AD had weaker connectivity of mSTS with the anterior STS (aSTS) compared with HC. Moreover, the connectivity of mSTS-aSTS in CD and AD was associated with their language skills. These findings confirmed our hypothesis that the intrinsic function of different parts of STS is distinctly impacted by deafness.

Neural synchronization during face-to-face communication.

Although the human brain may have evolutionarily adapted to face-to-face communication, other modes of communication, e.g., telephone and e-mail, increasingly dominate our modern daily life. This study examined the neural difference between face-to-face communication and other types of communication by simultaneously measuring two brains using a hyperscanning approach. The results showed a significant increase in the neural synchronization in the left inferior frontal cortex during a face-to-face dialog between partners but none during a back-to-back dialog, a face-to-face monologue, or a back-to-back monologue. Moreover, the neural synchronization between partners during the face-to-face dialog resulted primarily from the direct interactions between the partners, including multimodal sensory information integration and turn-taking behavior. The communicating behavior during the face-to-face dialog could be predicted accurately based on the neural synchronization level. These results suggest that face-to-face communication, particularly dialog, has special neural features that other types of communication do not have and that the neural synchronization between partners may underlie successful face-to-face communication.

Evaluating word in phrase: the modulation effect of emotional context on word comprehension.

The present study aims to explore the influence of emotional context on word evaluation. Participants were asked to read an "adjective + noun" phrase, where the adjective could be a positive or negative word, and the noun could be a positive, neutral or negative word, and then to make an emotional evaluation on the emotional tone of the target noun based on a 9-point Likert scale. In a control condition, an isolated noun was presented with no context. Results showed that positive context made the evaluation of target words bias toward positive tone, while negative context shaped the evaluation of target words toward negative tone. The modulatory effect of negative context was greater than that of positive context in shaping evaluation of emotional words with opposite valence. Moreover, the modulatory effect of emotional context was constrained by the inherent meaning of target word. The present study demonstrated the flexibility as well as the relative stability of emotional meaning of word.

Second language experience modulates functional brain network for the native language production in bimodal bilinguals.

The functional brain network of a bilingual's first language (L1) plays a crucial role in shaping that of his or her second language (L2). However, it is less clear how L2 acquisition changes the functional network of L1 processing in bilinguals. In this study, we demonstrate that in bimodal (Chinese spoken-sign) bilinguals, the functional network supporting L1 production (spoken language) has been reorganized to accommodate the network underlying L2 production (sign language). Using functional magnetic resonance imaging (fMRI) and a picture naming task, we find greater recruitment of the right supramarginal gyrus (RSMG), the right temporal gyrus (RSTG), and the right superior occipital gyrus (RSOG) for bilingual speakers versus monolingual speakers during L1 production. In addition, our second experiment reveals that these regions reflect either automatic activation of L2 (RSOG) or extra cognitive coordination (RSMG and RSTG) between both languages during L1 production. The functional connectivity between these regions, as well as between other regions that are L1- or L2-specific, is enhanced during L1 production in bimodal bilinguals as compared to their monolingual peers. These findings suggest that L1 production in bimodal bilinguals involves an interaction between L1 and L2, supporting the claim that learning a second language does, in fact, change the functional brain network of the first language.

Sensitive period for white-matter connectivity of superior temporal cortex in deaf people.

Previous studies have shown that white matter in the deaf brain changes due to hearing loss. However, how white-matter development is influenced by early hearing experience of deaf people is still unknown. Using diffusion tensor imaging and tract-based spatial statistics, we compared white-matter structures among three groups of subjects including 60 congenitally deaf individuals, 36 acquired deaf (AD) individuals, and 38 sex- and age-matched hearing controls (HC). The result showed that the deaf individuals had significantly reduced fractional anisotropy (FA) values in bilateral superior temporal cortex and the splenium of corpus callosum compared to HC. The reduction of FA values in acquired deafness correlated with onset age of deafness, but not the duration of deafness. To explore the underlying mechanism of FA changes in the deaf groups, we further analyzed radial and axial diffusivities and found that (1) the reduced FA values in deaf individuals compared to HC is primarily driven by higher radial diffusivity values and (2) in the AD, higher radial diffusivity was correlated with earlier onset age of deafness, but not the duration of deafness. These findings imply that early sensory experience is critical for the growth of fiber myelination, and anatomical reorganization following auditory deprivation is sensitive to early plasticity in the brain.

The involvement of occipital and inferior frontal cortex in the phonological learning of Chinese characters.

Neural changes related to the learning of the pronunciation of Chinese characters in English speakers were examined using fMRI. We examined the item-specific learning effects for trained characters and the generalization of phonetic knowledge to novel transfer characters that shared a phonetic radical (part of a character that gives a clue to the whole character's pronunciation) with trained characters. Behavioral results showed that shared phonetic information improved performance for transfer characters. Neuroimaging results for trained characters over learning found increased activation in the right lingual gyrus, and greater activation enhancement in the left inferior frontal gyrus (Brodmann's area 44) was correlated with higher accuracy improvement. Moreover, greater activation for transfer characters in these two regions at the late stage of training was correlated with better knowledge of the phonetic radical in a delayed recall test. The current study suggests that the right lingual gyrus and the left inferior frontal gyrus are crucial for the learning of Chinese characters and the generalization of that knowledge to novel characters. Left inferior frontal gyrus is likely involved in phonological segmentation, whereas right lingual gyrus may subserve processing visual-orthographic information.

Improved application of independent component analysis to functional magnetic resonance imaging study via linear projection techniques.

Spatial Independent component analysis (sICA) has been widely used to analyze functional magnetic resonance imaging (fMRI) data. The well accepted implicit assumption is the spatially statistical independency of intrinsic sources identified by sICA, making the sICA applications difficult for data in which there exist interdependent sources and confounding factors. This interdependency can arise, for instance, from fMRI studies investigating two tasks in a single session. In this study, we introduced a linear projection approach and considered its utilization as a tool to separate task-related components from two-task fMRI data. The robustness and feasibility of the method are substantiated through simulation on computer data and fMRI real rest data. Both simulated and real two-task fMRI experiments demonstrated that sICA in combination with the projection method succeeded in separating spatially dependent components and had better detection power than pure model-based method when estimating activation induced by each task as well as both tasks.

Developmental differences of neurocognitive networks for phonological and semantic processing in Chinese word reading.

Developmental differences in the neurocognitive networks for phonological and semantic processing in Chinese word reading were examined in 13 adults and 13 children using functional magnetic resonance imaging (fMRI). Rhyming and semantic association judgments were made to two-character words that were presented sequentially in the visual modality. These lexical tasks were compared with a nonlinguistic control task involving judgment of line patterns. The first main finding was that adults showed greater activation than children in right middle occipital gyrus on both the meaning and rhyming task, suggesting adults more effectively engage right hemisphere brain regions involved in the visual-spatial analysis of Chinese characters. The second main finding was that adults showed greater activation than children in left inferior parietal lobule for the rhyming as compared with the meaning task, suggesting greater specialization of phonological processing in adults. The third main finding was that children who had better performance in the rhyming task on characters with conflicting orthographic and phonological information relative to characters with nonconflicting information showed greater activation in left middle frontal gyrus, suggesting greater engagement of brain regions involved in the integration of orthography and phonology.

Item-specific and generalization effects on brain activation when learning Chinese characters.

Neural changes related to learning of the meaning of Chinese characters in English speakers were examined using functional magnetic resonance imaging (fMRI). We examined item specific learning effects for trained characters, but also the generalization of semantic knowledge to novel transfer characters that shared a semantic radical (part of a character that gives a clue to word meaning, e.g. water for lake) with trained characters. Behavioral results show that acquired semantic knowledge improves performance for both trained and transfer characters. Neuroimaging results show that the left fusiform gyrus plays a central role in the visual processing of orthographic information in characters. The left superior parietal cortex seems to play a crucial role in learning the visual-spatial aspects of the characters because it shows learning related decreases for trained characters, is correlated with behavioral improvement from early to late in learning for the trained characters, and is correlated with better long-term retention for the transfer characters. The inferior frontal gyrus seems to be associated with the efficiency of retrieving and manipulating semantic representations because there are learning related decreases for trained characters and this decrease is correlated with greater behavioral improvement from early to late in learning.

Dynamic Influence of Emotional States on Novel Word Learning.

Many researchers realize that it's unrealistic to isolate language learning and processing from emotions. However, few studies on language learning have taken emotions into consideration so far, so that the probable influences of emotions on language learning are unclear. The current study thereby aimed to examine the effects of emotional states on novel word learning and their dynamic changes with learning continuing and task varying. Positive, negative or neutral pictures were employed to induce a given emotional state, and then participants learned the novel words through association with line-drawing pictures in four successive learning phases. At the end of each learning phase, participants were instructed to fulfill a semantic category judgment task (in Experiment 1) or a word-picture semantic consistency judgment task (in Experiment 2) to explore the effects of emotional states on different depths of word learning. Converging results demonstrated that negative emotional state led to worse performance compared with neutral condition; however, how positive emotional state affected learning varied with learning task. Specifically, a facilitative role of positive emotional state in semantic category learning was observed but disappeared in word specific meaning learning. Moreover, the emotional modulation on novel word learning was quite dynamic and changeable with learning continuing, and the final attainment of the learned words tended to be similar under different emotional states. The findings suggest that the impact of emotion can be offset when novel words became more and more familiar and a part of existent lexicon.

Brain development in Chinese children and adolescents: a structural MRI study.

This is the first systematic study of Chinese children's brain development. Using optimized voxel-based morphometry, we investigated age-related changes in gray and white matter in Chinese children and adolescents aged 7 to 23 years. Results showed mostly linear reductions, but also some linear increases, in gray matter in many regions of the brain. Gray matter changes were more evident in the parietal and temporal regions than in the frontal and occipital regions. White matter showed significant linear increases in internal capsule, arcuate fasciculus, superior and inferior longitudinal fasciculus, and cingulate fasciculus.

An event-related potential study on perceptual learning in grating orientation discrimination.

This study aims to investigate the neural mechanism of visual perceptual learning in grating orientation discrimination. We recorded event-related potentials of human adults when they were trained with a grating orientation discrimination task. Although psychophysical thresholds decreased significantly across training sessions, event-related potentials showed larger P2 and P3 amplitudes and smaller N1 amplitudes over the parietal/occipital areas with more practice. In line with the psychophysical thresholds, the training effect on the P2 and P3 were specific to stimulus orientation. The N1 effect, however, was generalized over differently oriented gratings. Our findings show that several stages of visual processing are involved in perceptual learning and provide an illustration of the temporal relationship between specific and generalized perceptual learning in human adults.

Speaking words in the second language: From semantics to phonology in 170 ms.

The temporal course of semantic and phonological retrieval when producing words in the second language was investigated using ERP technique. In the experiment, less proficient Chinese-English bilinguals were required to name pictures in their second language. Before performing this task, they carried out a dual choice go/nogo task on the basis of a picture's semantic information (i.e., whether the picture was of an object or an animal) and phonological information (e.g., whether the picture's English name starts with the letter C or F). During the time window of 200-600ms after stimulus onset, nogo trials generated a more negative ERP profile relative to go trials. A clear-cut N200 was obtained from their difference waves. Overall, the peak latency of N200 elicited by semantic information is earlier than that by phonological information. It takes unbalanced bilinguals approximate 170ms to retrieve phonological information after semantic information becomes available in the second language production. These findings suggest that the semantic information is encoded earlier than the phonological information during the second language production.

Local bias and local-to-global interference without global deficit: a robust finding in autism under various conditions of attention, exposure time, and visual angle.

A wide variety of paradigms have shown that autistic individuals present with superior performance on visual tasks. Here, the impact of task constraints on visual hierarchical processing in autism was investigated. By employing free- and forced-choice procedures, global and local processing of Navon-type hierarchical numerals was examined in 15 autistic persons (13 males, 2 females) and a comparison group. In the free-choice condition, autistics chose global and local targets randomly, though they were faster responding to local than to global targets, regardless of visual angle and exposure duration. In contrast, the comparison group exhibited a global advantage in naming time, which was evident only for shorter exposures, as well as effects of visual angle. In the forced-choice condition, autistics presented with a more important local-to-global interference than global-to-local interference, whereas the comparison group exhibited global advantage and bidirectional interference. Overall, the autistic participants presented with atypical local-to-global interference and local advantage in incongruent conditions (where global and local targets differ), in naming time as well as accuracy. The relative insensitivity of local bias to task constraints in autistics, in comparison to nonautistic participants, indicates that local bias, with local-to-global interference, is a key and characteristic feature of autistic visual cognition and a strong candidate for the "endophenotype" of autism.

[Gray matter abnormalities in developmental stuttering determined with voxel-based morphometry].

OBJECTIVE: To investigate the differences of regional grey matter volume between adults with persistent developmental stuttering and fluent speaking adults, and to determine whether stutterers have anomalous anatomy of speech-relevant brain areas that possibly affect speech fluency. METHODS: High-resolution magnetic resonance imaging (MRI) scanning was performed on 10 adults with developmental stuttering, aged 26 (21 - 35) with the onset age of 4 (3 - 7) and 12 age, sex, hand preference, and education-matched controls. The customized brain templates were created in order to improve spatial normalization and segmentation. Then automated preprocessing of MRI data was conducted using an optimized version of VBM, a fully automated unbiased and objective whole-brain MRI analysis technique. RESULTS: VBM analysis revealed that compared with the controls, the stuttering adults had significant clusters of locally gray matter volume increased in the superior temporal, middle temporal, precentral and postcentral gyrus, and inferior parietal lobule of the bilateral hemisphere (P < 0.001), the numbers of increased gray matter volume in the right and left hemispheres were 60,247 and 48,782 voxels respectively. The, Grey matter decrease was shown with an overall decreased gray matter volume of 32 394 voxels, mainly in the bilateral cerebella posterior lobe and dorsal part of medulla, especially inferior semi-lunar lobule, followed by cerebellar tonsil and bilateral medulla in comparison with the controls (P < 0.001). CONCLUSION: The reduction of the regional gray matter volume of bilateral cerebella and medulla is related to the neural mechanism of the controlling disorder of speech production and may be the essential cause of stuttering. Some areas with increased gray matter volume in temporal lobe, parietal lobe, and frontal lobe, may be the result of long term functional compensation for the cerebella and medulla function deficiency.

Speech Timing Deficit of Stuttering: Evidence from Contingent Negative Variations.

The aim of the present study was to investigate the speech preparation processes of adults who stutter (AWS). Fifteen AWS and fifteen adults with fluent speech (AFS) participated in the experiment. The event-related potentials (ERPs) were recorded in a foreperiod paradigm. The warning signal (S1) was a color square, and the following imperative stimulus (S2) was either a white square (the Go signal that required participants to name the color of S1) or a white dot (the NoGo signal that prevents participants from speaking). Three differences were found between AWS and AFS. First, the mean amplitude of the ERP component parietal positivity elicited by S1 (S1-P3) was smaller in AWS than in AFS, which implies that AWS may have deficits in investing working memory on phonological programming. Second, the topographic shift from the early phase to the late phase of contingent negative variation occurred earlier for AWS than for AFS, thus suggesting that the motor preparation process is promoted in AWS. Third, the NoGo effect in the ERP component parietal positivity elicited by S2 (S2-P3) was larger for AFS than for AWS, indicating that AWS have difficulties in inhibiting a planned speech response. These results provide a full picture of the speech preparation and response inhibition processes of AWS. The relationship among these three findings is discussed. However, as stuttering was not manipulated in this study, it is still unclear whether the effects are the causes or the results of stuttering. Further studies are suggested to explore the relationship between stuttering and the effects found in the present study.

Reorganization of brain function after a short-term behavioral intervention for stuttering.

This study investigated changes in brain function that occurred over a 7-day behavioral intervention for adults who stutter (AWS). Thirteen AWS received the intervention (AWS+), and 13 AWS did not receive the intervention (AWS-). There were 13 fluent controls (FC-). All participants were scanned before and after the intervention. Whole-brain analysis pre-intervention showed significant differences in task-related brain activation between AWS and FC- in the right inferior frontal cortex (IFC) and left middle temporal cortex, but there were no differences between the two AWS groups. Across the 7-day period of the intervention, AWS+ alone showed a significant increase of brain activation in the left ventral IFC/insula. There were no changes in brain function for the other two groups. Further analysis revealed that the change did not correlate with resting-state functional connectivity (RSFC) that AWS showed in the cerebellum (Lu et al., 2012). However, both changes in task-related brain function and RSFC correlated with changes in speech fluency level. Together, these findings suggest that functional reorganization in a brain region close to the left IFC that shows anomalous function in AWS, occurs after a short-term behavioral intervention for stuttering.

Dynamic spatial organization of the occipito-temporal word form area for second language processing.

Despite the left occipito-temporal region having shown consistent activation in visual word form processing across numerous studies in different languages, the mechanisms by which word forms of second languages are processed in this region remain unclear. To examine this more closely, 16 Chinese-English and 14 English-Chinese late bilinguals were recruited to perform lexical decision tasks to visually presented words in both their native and second languages (L1 and L2) during functional magnetic resonance imaging scanning. Here we demonstrate that visual word form processing for L1 versus L2 engaged different spatial areas of the left occipito-temporal region. Namely, the spatial organization of the visual word form processing in the left occipito-temporal region is more medial and posterior for L2 than L1 processing in Chinese-English bilinguals, whereas activation is more lateral and anterior for L2 in English-Chinese bilinguals. In addition, for Chinese-English bilinguals, more lateral recruitment of the occipito-temporal region was correlated with higher L2 proficiency, suggesting higher L2 proficiency is associated with greater involvement of L1-preferred mechanisms. For English-Chinese bilinguals, higher L2 proficiency was correlated with more lateral and anterior activation of the occipito-temporal region, suggesting higher L2 proficiency is associated with greater involvement of L2-preferred mechanisms. Taken together, our results indicate that L1 and L2 recruit spatially different areas of the occipito-temporal region in visual word processing when the two scripts belong to different writing systems, and that the spatial organization of this region for L2 visual word processing is dynamically modulated by L2 proficiency. Specifically, proficiency in L2 in Chinese-English is associated with assimilation to the native language mechanisms, whereas L2 in English-Chinese is associated with accommodation to second language mechanisms.