Weiyong Xu

Bio: Weiyong Xu is an academic researcher from University of Jyväskylä. The author has contributed to research in topics: Temporal cortex & Brain activity and meditation. The author has an hindex of 5, co-authored 10 publications receiving 60 citations. Previous affiliations of Weiyong Xu include Xi'an Jiaotong University.

Audiovisual processing of Chinese characters elicits suppression and congruency effects in MEG

Abstract: Learning to associate written letters/characters with speech sounds is crucial for reading acquisition. Most previous studies have focused on audiovisual integration in alphabetic languages. Less is known about logographic languages such as Chinese characters, which map onto mostly syllable-based morphemes in the spoken language. Here we investigated how long-term exposure to native language affects the underlying neural mechanisms of audiovisual integration in a logographic language using magnetoencephalography (MEG). MEG sensor and source data from 12 adult native Chinese speakers and a control group of 13 adult Finnish speakers were analyzed for audiovisual suppression (bimodal responses vs. sum of unimodal responses) and congruency (bimodal incongruent responses vs. bimodal congruent responses) effects. The suppressive integration effect was found in the left angular and supramarginal gyri (205-365 ms), left inferior frontal and left temporal cortices (575-800 ms) in the Chinese group. The Finnish group showed a distinct suppression effect only in the right parietal and occipital cortices at a relatively early time window (285-460 ms). The congruency effect was only observed in the Chinese group in left inferior frontal and superior temporal cortex in a late time window (about 500-800 ms) probably related to modulatory feedback from multi-sensory regions and semantic processing. The audiovisual integration in a logographic language showed a clear resemblance to that in alphabetic languages in the left superior temporal cortex, but with activation specific to the logographic stimuli observed in the left inferior frontal cortex. The current MEG study indicated that learning of logographic languages has a large impact on the audiovisual integration of written characters with some distinct features compared to previous results on alphabetic languages.

Brain Responses to Letters and Speech Sounds and Their Correlations With Cognitive Skills Related to Reading in Children.

Abstract: Letter-speech sound (LSS) integration is crucial for initial stages of reading acquisition. However, the relationship between cortical organization for supporting LSS integration, including unimodal and multimodal processes, and reading skills in early readers remains unclear. In the present study, we measured brain responses to Finnish letters and speech sounds from 29 typically developing Finnish children in a child-friendly audiovisual integration experiment using magnetoencephalography. Brain source activations in response to auditory, visual and audiovisual stimuli as well as audiovisual integration response were correlated with reading skills and cognitive skills predictive of reading development after controlling for the effect of age. Regression analysis showed that from the brain measures, the auditory late response around 400 ms showed the largest association with phonological processing and rapid automatized naming abilities. In addition, audiovisual integration effect was most pronounced in the left and right temporoparietal regions and the activities in several of these temporoparietal regions correlated with reading and writing skills. Our findings indicated the important role of temporoparietal regions in the early phase of learning to read and their unique contribution to reading skills.

Aging-related changes of EEG synchronization during a visual working memory task

Abstract: Differences of EEG synchronization between normal old and young people during a working memory (WM) task were investigated. The synchronization likelihood (SL) is a novel method to assessed synchronization in multivariate time series for non-stationary systems. To evaluate this method to study the mechanisms of WM, we calculated the SL values in brain electrical activity for both resting state and task state. EEG signals were recorded from 14 young adults and 12 old adults during two different states, respectively. SL was used to measure EEG synchronization between 19 electrodes in delta, theta, alpha1, alpha2 and beta frequency bands. Bad task performance and significantly decreased EEG synchronization were found in old group compared to young group in alpha1, alpha2 and beta frequency bands during the WM task. Moreover, significantly decreased EEG synchronization in beta band in the elder was also detected during the resting state. The findings suggested that reduced EEG synchronization may be one of causes for WM capacity decline along with healthy aging.

Assay of melamine in milk products with a pH‐mediated stacking technique in capillary electrophoresis

Abstract: A pH-mediated stacking method in capillary electrophoresis as an assay for low concentrations of melamine in milk products was established. Real samples were treated with acetone and sodium acetate and injected directly after centrifugation and filtration. Several experimental factors, such as buffer pH, buffer concentration, sample matrix, injection/sweeping ratio, sweeping time/voltages, separation voltages, as well as sample pretreatment, which affected stacking and separation, were investigated and optimized. Under the selected condition, a low LOD of 0.01 μmol/L (S/N = 5) and a wide range of linearity of 0.01∼1.0 μmol/L could be easily achieved with a good reproducibility (RSDs < 5.8% for both migration time and peak area) and an acceptable recovery of 94.0∼103.2% (for milk, infant formula, yogurt, and milk products). The proposed method was suitable for routine assay of melamine in real milk samples.

An Introduction To The Event Related Potential Technique

Abstract: Thank you for downloading an introduction to the event related potential technique. Maybe you have knowledge that, people have look hundreds times for their favorite readings like this an introduction to the event related potential technique, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they are facing with some malicious bugs inside their laptop.

Learning to Read

Abstract: In 2012, I left radiology residency to pursue internal medicine training As a medical student, I had been drawn to radiology’s diagnostic challenges and its attention to detail But it wasn’t long after beginning radiology training that I realized I missed treating patients When I broke news of my decision to leave, my colleagues were skeptical: after more than a year away from clinical medicine, was I sure I wanted to do this? Nevertheless, my first morning back as a senior medical resident went well I had spent the night before excitedly reading about the patients I’d be caring for Morning rounds felt at once novel and suddenly familiar—the easy cadence of conversation as our team walked down the hospital corridor; the expectant look on patients’ faces as we entered their rooms Around early evening, after my attending (and, it seemed, everyone else in the hospital) had left for the day, doubt crept in Less than 3 weeks prior, I had been comfortably reading X-rays and CTs Now I was on call and supervising two newly minted interns My pager beeped interminably Sure, I could interpret a stat portable chest radiograph…but a 12-lead EKG in a patient with atypical chest pain? Or an arterial blood gas? Before, from the relative isolation of a leather office chair and a darkened room, I had a faint sense of what it meant to be a clinician This—being a medical resident on call—was something else entirely I thought of the final lines of Sinclair Lewis’ Arrowsmith, which so ably captured that feeling that all physicians, facing a seemingly insurmountable body of knowledge, must know well: I feel as if I were really beginning to work now In that moment, however, Lewis’ words took on an ominous tone Mr H was my first admission that night He had come to the emergency room because over the preceding few months, he had noticed a steady decline in his exercise tolerance He had always been active (he was a roofer by trade), but now, walking more than a block required him to pause and hunch over, hands on his knees, to catch his breath Mr H hadn’t seen a doctor since he was in the military Hadn’t had to, he said “I’ve always been healthy” The ability to discern “sick” from “not sick,” I had heard so many times, is among the more valuable things that one learns during internship and residency In the case of Mr H, however, he didn’t look sick—not in the way that I had grown accustomed to seeing: on a stretcher, being wheeled into the scanner for a trauma survey Instead, he sat upright and proudly recounted how he had never smoked a day in his life, and how last year he and his wife had joined a gym But Mr H’s placid exterior belied ominous findings—namely, his oxygen saturation, which was 93 % at rest and dropped to below 80 % when I walked with him up and down the corridor Breathing heavily, he steadied himself against the wall about ten feet from his room He looked scared If there had been any doubt about whether Mr H was sick, it had since evaporated I pored over the chest X-ray he had received in the ED Was that a nodule? Were those reticular markings at the bases? I agonized over what to do next The list of possible diagnostic tests seemed endless I finally settled on a CT, convincing myself that if Mr H had something catastrophic in his chest, a CT would surely pick it up By the time Mr H received his scan, it was well past midnight I scrolled through the images, afraid of what the next slice would reveal My mind raced through the possibilities Sarcoid Interstitial lung disease Lymphoma Finally, after what seemed like an eternity staring at the screen (and after calling the nighthawk radiologist for reassurance), I sat back in my chair and rubbed my eyes Nothing His scan was clean It was late Rounds were in a few hours I walked back into Mr H’s room to give him the results of his CT “Well, Doc?” he asked with a wan smile He hadn’t slept I froze, struggling to find a way to tell him that about a thousand dollars and 20 millisieverts of radiation later, I was no closer to figuring out what was wrong I mumbled something about waiting on more results and left his room His gaze trailed after me In the hall, I steadied myself against the same wall that Mr H had leaned on hours earlier The next few days would reveal that he suffered from pulmonary arterial hypertension He received an echocardiogram and underwent right heart catheterization His disease was pretty advanced I kept telling myself that his was an illness that no conventional radiologic study could reliably detect, and that another resident would have done the same thing overnight But truthfully, during those next few days, I was in a fog While the pulmonologists exchanged terms like “endothelin” and “nitric oxide,” I perseverated on the events of the night I met Mr H, replaying them in a continuous loop: my less-than-thorough social history (had I asked about pet birds?), my (no doubt incomplete) physical exam I had re-entered medical residency with rusty clinical skills, to be sure; but I thought this deficit might be counterbalanced by my ability to read images Yet, had my reliance on this ability caused me to overlook Mr H’s diagnosis? When I was a radiology resident, my attendings would sometimes tell me that becoming adept at interpreting images required learning how to read all over again For instance, when looking at a chest X-ray, forget what you learned in medical school—ie, “A is for airway, B is for bones”—instead, look at the study as a whole The scan comprises a map, or better yet, words on a page; it’s up to you to glean their meaning Now, as I approach the end of internal medicine residency, I know that the same can be said of patients, their stories, their faces Looking back, I think I know why: to acquire that sine qua non characteristic that the best medicine doctors possess—the ability to elicit a patient’s history and arrive at a diagnosis—one has to learn to read patients with the same level of nuance The etiology of patients’ illnesses can be found in poring through their images, but it’s also buried in their histories and etched in their expressions Now and then I’ll hear a bit about how Mr H is doing He wears continuous oxygen The word “transplant” is frequently mentioned Hearing these updates always grounds me, reminds me how far I’ve come since that night—and also how far there is to go It’s all part of learning to read

Top-down task effects overrule automatic multisensory responses to letter-sound pairs in auditory association cortex

Abstract: In alphabetic scripts, letters and speech sounds are the basic elements of correspondence between spoken and written language. In two previous fMRI studies using blocked stimulus presentation and passive perception, we found a cross-modal modulation of the response to speech sounds in the auditory association cortex by letters, expressed as response enhancement by congruent letters and suppression by incongruent letters. Interestingly, temporal proximity was critical for this congruency effect to occur. In the present study, we used fMRI to investigate the effect of stimulus presentation mode (blocked vs. event-related) and task instruction (passive perception vs. active matching) on the neural integration of letters and speech sounds. The principle findings are 1) a replication of the previous results on passive integration using event-related fMRI, and 2) the absence of the effects of congruency and temporal proximity in the auditory association cortex during active matching. Finding 1 shows the suitability of event-related fMRI for studying letter-sound integration. Finding 2 indicates that the task demands overruled the automatic multisensory responses to letters and speech sounds, most likely because the task changed the behavioral relevance of the stimuli.

Contemporary sample stacking in analytical electrophoresis: CE and CEC

Abstract: Sample stacking is a term denoting a multifarious class of methods and their names that are used daily in CE for online concentration of diluted samples to enhance separation efficiency and sensitivity of analyses. The essence of these methods is that analytes present at low concentrations in a large injected sample zone are concentrated into a short and sharp zone (stack) in the separation capillary. Then the stacked analytes are separated and detected. Regardless of the diversity of the stacking electromigration methods, one can distinguish four main principles that form the bases of nearly all of them: (i) Kohlrausch adjustment of concentrations, (ii) pH step, (iii) micellar methods, and (iv) transient ITP. This contribution is a continuation of our previous reviews on the topic and brings an overview of papers published during 2010–2012 and relevant to the mentioned principles (except the last one which is covered by another review in this issue).

A Review of Methods for Detecting Melamine in Food Samples.

Abstract: Melamine is a synthetic chemical used in the manufacture of resins, pigments, and superplasticizers. Human beings can be exposed to melamine through various sources such as migration from related products into foods, pesticide contamination, and illegal addition to foods. Toxicity studies suggest that prolonged consumption of melamine could lead to the formation of kidney stones or even death. Therefore, reliable and accurate detection methods are essential to prevent human exposure to melamine. Sample preparation is of critical importance, since it could directly affect the performance of analytical methods. Some methods for the detection of melamine include instrumental analysis, immunoassays, and sensor methods. In this paper, we have summarized the state-of-the-art methods used for food sample preparation as well as the various detection techniques available for melamine. Combinations of multiple techniques and new materials used in the detection of melamine have also been reviewed. Finally, future perspectives on the applications of microfluidic devices have also been provided.