Zhuangwei Xiao

Differential activity in left inferior frontal gyrus for pseudowords and real words: An event-related fMRI study on auditory lexical decision

After Newman and Twieg ([ 2001 ]: Hum Brain Mapp 14:39–47) and others, we used a fast event‐related functional magnetic resonance imaging (fMRI) design and contrasted the lexical processing of pseudowords and real words. Participants carried out an auditory lexical decision task on a list of randomly intermixed real and pseudo Chinese two‐character (or two‐syllable) words. The pseudowords were constructed by recombining constituent characters of the real words to control for sublexical code properties. Processing of pseudowords and real words activated a highly comparable network of brain regions, including bilateral inferior frontal gyrus, superior, middle temporal gyrus, calcarine and lingual gyrus, and left supramarginal gyrus. Mirroring a behavioral lexical effect, left inferior frontal gyrus (IFG) was significantly more activated for pseudowords than for real words. This result disconfirms a popular view that this area plays a role in grapheme‐to‐phoneme conversion, as such a conversion process was unnecessary in our task with auditory stimulus presentation. An alternative view was supported that attributes increased activity in left IFG for pseudowords to general processes in decision making, specifically in making positive versus negative responses. Activation in left supramarginal gyrus was of a much larger volume for real words than for pseudowords, suggesting a role of this region in the representation of phonological or semantic information for two‐character Chinese words at the lexical level. Hum Brain Mapp 25:212–221, 2005.

Peripheral pulmonary nodules: Relationship between multi-slice spiral CT perfusion imaging and tumor angiogenesis and VEGF expression

BackgroundThe aim of this study is to investigate the relationship between16-slice spiral CT perfusion imaging and tumor angiogenesis and VEGF (vascular endothelial growth factor) expression in patients with benign and malignant pulmonary nodules, and differential diagnosis between benign and malignant pulmonary nodules.MethodsSixty-four patients with benign and malignant pulmonary nodules underwent 16-slice spiral CT perfusion imaging. The CT perfusion imaging was analyzed for TDC (time density curve), perfusion parametric maps, and the respective perfusion parameters. Immunohistochemical findings of MVD (microvessel density) measurement and VEGF expression was evaluated.ResultsThe shape of the TDC of peripheral lung cancer was similar to those of inflammatory nodule. PH (peak height), PHpm/PHa (peak height ratio of pulmonary nodule to aorta), BF (blood flow), BV (blood volume) value of peripheral lung cancer and inflammatory nodule were not statistically significant (all P > 0.05). Both showed significantly higher PH, PHpm/PHa, BF, BV value than those of benign nodule (all P < 0.05). Peripheral lung cancer showed significantly higher PS (permeability surface) value than that of inflammatory nodule and benign nodule (all P < 0.05). BV, BF, PS, MTT, PH, PHpm/PHa, and MVD among three groups of peripheral lung cancers were not significantly (all P > 0.05). In the case of adenocarcinoma, BV, BF, PS, PHpm/PHa, and MVD between poorly and well differentiation and between poorly and moderately differentiation were statistically significant (all P < 0.05). The peripheral lung cancers with VEGF positive expression showed significantly higher PH, PHpm/PHa, BF, BV, PS, and MVD value than those of the peripheral lung cancer with VEGF negative expression, and than those of benign nodule with VEGF positive expression (all P < 0.05). When investigating VEGF negative expression, it is found that PH, PHpm/PHa, and MVD of inflammatory nodule were significantly higher than those of peripheral lung cancer, PS of inflammatory nodule were significantly lower than that of peripheral lung cancer (all P < 0.05). PH, PHpm/PHa, BF, and BV of benign nodule were significantly lower than those of inflammatory nodule (all P < 0.05), rather than PS and MTT (mean transit time) (all P > 0.05). PH, PHpm/PHa, BV, and PS of benign nodule were significantly lower than those of peripheral lung cancer (all P < 0.05). In the case of VEGF positive expression, MVD was positively correlated with PH, PHpm/PHa, BF, BV, and PS of peripheral lung cancer and PS of benign nodule (all P < 0.05).ConclusionMulti-slice spiral CT perfusion imaging closely correlated with tumor angiogenesis and reflected MVD measurement and VEGF expression. It provided not only a non-invasive method of quantitative assessment for blood flow patterns of peripheral pulmonary nodules but also an applicable diagnostic method for peripheral pulmonary nodules.

Involvement of left inferior frontal gyrus in sentence-level semantic integration

Using event-related functional MRI, we examined the involvement of the left inferior frontal gyrus (LIFG) in semantic integration in reading Chinese sentences. During scanning, Chinese readers read individually presented sentences and judged whether or not a sentence was semantically acceptable. Behaviorally, those sentences with a small degree of semantic violation were found to be more difficult to reject relative to sentences with a large degree of semantic violation, indicating that more semantic integration occurred in the former than in the latter condition. Direct contrast revealed significantly greater brain activity in the LIFG for sentences with a small violation, relative to those with a large violation, but no differences in any anterior temporal cortical areas between the two types of anomalous sentences. The results are in line with the idea that the LIFG plays a critical role in integrating individual word meanings to coherent sentence-level messages, but not with the idea that semantic integration depends on anterior temporal cortex in language comprehension.

Broca's area plays a role in syntactic processing during Chinese reading comprehension

Event-related functional magnetic resonance imaging (ER-fMRI) was adopted to examine brain activation of syntactic processing in reading logographic Chinese. While fMRI data were obtained, 15 readers of Chinese read individually presented sentences and performed semantic congruency judgments on three kinds of sentences: Congruous sentences (CON), sentences with a semantic violation (SEM), and sentences with both semantic and syntactic violations (SEM+SYN). The two types of incongruous sentences were matched in the degree of semantic plausibility. Three brain regions were identified showing significantly different levels of percent signal change across the three conditions, including BA44 in the left inferior frontal gyrus (IFG) and both BA9 and BA10/46 in the left middle frontal gyrus (MFG). Furthermore, the mean percent signal change in the left BA44 observed in the SEM+SYN condition was significantly stronger than that in either the SEM or the CON condition, while the latter two conditions were at a similar level, implying an important role of this area in Chinese syntactic processing. These results, in conjunction with those found in alphabetic scripts, suggest that there are some common neural substrates underlie syntactic processing across distinctive writing systems such as the logographic Chinese and the alphabetic English.

Acute effects of sublingual buprenorphine on brain responses to heroin-related cues in early-abstinent heroin addicts: an uncontrolled trial

Replacement therapy with buprenorphine is clinically effective in reducing withdrawal and craving for heroin during detoxification but not in decreasing the probability of relapse after detoxification. This study examined the acute effects of buprenorphine on brain responses to heroin-related cues to reveal the neurobiological and therapeutic mechanisms of addiction and relapse. Fifteen heroin addicts at a very early period of abstinence, were studied in two separate periods 10-15 min apart: an early period (5-45 min) and a later period (60-105 min) after sublingual buprenorphine, roughly covering the onset and peak of buprenorphine plasma level. During both periods, fMRI scanning with heroin-related visual stimuli were performed followed by questionnaires. Under effect of buprenorphine, brain responses to heroin-related cues showed decrease in amygdala, hippocampus, ventral tegmental area (VTA) and thalamus but no changes in ventral striatum and orbital-prefrontal-parietal cortices. As an uncontrolled trial, these preliminary results suggest that buprenorphine has specific brain targets in reducing withdrawal and craving during early abstinence, and that ventral striatum and orbital-prefrontal-parietal cortices may be the key targets in developing therapy for drug addiction and relapse.

An electrophysiological signature for proactive interference resolution in working memory

We used event-related potentials (ERPs) to study the temporal dynamics of proactive interference in working memory. Participants performed a Sternberg item-recognition task to determine whether a probe was in a target memory set. Familiar negative probes were found to be more difficult to reject than less familiar ones. A fronto-central N2 component peaking around 300 ms post-probe-onset differentiated among target probes, familiar and less familiar non-target probes. The study identifies N2 as the ERP signature for proactive interference resolution. It also indicates that the resolution process occurs in the same time window as target/non-target discrimination and provides the first piece of electrophysiological evidence supporting a recent interference resolution model based on localization data [Jonides, J., Nee, D.E., 2006. Brain mechanisms of proactive interference in working memory. Neuroscience 139, 181-193].

Neural systems and time course of proactive interference in working memory

The storage of information in working memory suffers as a function of proactive interference. Many works using neuroimaging technique have been done to reveal the brain mechanism of interference resolution. However, less is yet known about the time course of this process. Event-related potential method(ERP) and standardized low resolution brain electromagnetic tomography method (sLORETA) were used in this study to discover the time course of interference resolution in working memory. The anterior P2 was thought to reflect interference resolution and if so, this process occurred earlier in working memory than in long-term memory.

Neural evidence for direct meaning access from orthography in Chinese word reading

A fundamental issue in the study of reading is to understand the processes involved in determining word meaning from print. We used functional magnetic resonance imaging (fMRI) and scanned participants performing lexical decision tasks to discriminate between real Chinese words and non-words, presented either visually or auditorily. For the visual task, two left inferior frontal cortical regions were significantly more activated for non-words than for words, one in BA (Brodmanns area) 44/45 implied in phonological processing, and one in BA47 implied in semantic processing. For the auditory task, stronger neural activity for non-words, relative to words, was only found in BA44/45 but not in BA47. The results were interpreted to suggest that printed words in Chinese can directly activate their semantic representations, independent of an indirect, mediated pathway through phonology. In reference to related imaging studies on English, our finding implies a greater reliance on orthography in Chinese reading.

Similar brain activation patterns for writing logographic and phonetic symbols in Chinese

This event-related functional MRI study examined the neural correlates for Chinese writing, by comparing the writing of logographic characters and that of pinyin, a phonetic notation system for Chinese characters. The temporal profile of the activations indicated that the middle frontal gyrus, superior parietal lobule, and posterior inferior temporal gyrus reflected more central processes for writing. Although pinyin writing elicited greater activity overall than character writing, the critical finding is that the two types of symbols recruited essentially the same brain regions. The results were compared with studies in Japanese showing dissociation between logographic kanji and phonetic kana writing and frequency of use was suggested to be an important factor in accounting for result differences across the two writing systems.

Abnormal auditory sensory gating-out in first-episode and never-medicated paranoid schizophrenia patients: an fMRI study.

Abstract Numerous electrophysiological studies have showed auditory sensory gating-out abnormalities in chronic schizophrenia with antipsychotic medication. Previous research has used functional magnetic resonance imaging (fMRI) with excellent spatial resolution to identify the neural substrates of sensory gating-out deficits revealing increased hemodynamic response in the hippocampus, thalamus and prefrontal cortex. However, such results obtained from medicated patients may be confounded by antipsychotic medication. The present study scanned 15 first-episode schizophrenia patients not yet receiving any medical treatment and 15 healthy controls matched in gender, age and education when they performed a sensory gating-out task adapted for fMRI. The symptoms of the patients were assessed with the positive and negative syndrome scale. Different from previous findings, the schizophrenia patients showed decreased activation in hippocampus and thalamus during sensory gating-out, compared with the normal controls. The results support the theory attributing abnormal sensory gating-out in schizophrenia patients to the dysfunction of hippocampus and thalamus.