Lei Zhang

Shanghai Normal University, Shanghai, Shanghai Shi, China

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Publications (15)33.61 Total impact

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    ABSTRACT: The study of a new water-soluble reagent, N-allyl-N ' -(sodium p-aminobenzenesulfonate)thiourea (ASAT)'s preparation and its characteristics are described. It was found that in pH 4.0-5.5 NaAc-HAc buffer solution, ASAT forms a stable yellow soluble complex with Pd. The maximum absorption is at 296 nm, ɛ=1.33×101 mol cm. Higher sensitivity and selectivity are advantages of this method. The new method is simple and convenient and can provide satisfactory results on samples of anode mud and ore.
    Analytical Letters - ANAL LETT. 02/2008; 33(12):2533-2543.
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    ABSTRACT: A new chromogenic reagent, N-o-methylphenyl-N'-(sodium p-aminobenzenesulfonate)thiourea (MSAT), has been synthesized and characterized by elemental analysis, (1)H-NMR, FT-IR and UV-Vis spectra. Based on the absorption spectrum of the colored complex of MSAT with palladium(II), a novel spectrophotometric method for the determination of palladium has been developed. In a pH 4.0 - 5.5 HAc-NaAc buffer solution, palladium(II) reacted with MSAT to form a stable yellow water-soluble complex with an apparent molar absorptivity of epsilon = 2.04 x 10(5) L mol(-1) cm(-1) at the maximum absorption of 318.0 nm. Beer's law was obeyed in the concentration range of 1.2 - 11.8 microg per 25 mL for palladium(II) with a correlation coefficient of 0.9997. The probable interfering ions and their tolerable limits have also been investigated in detail. The proposed method is simple, rapid, and sensitive, and has been applied to the determination of palladium in anode mud and ore samples with satisfactory results.
    Analytical Sciences 08/2006; 22(7):989-92. · 1.57 Impact Factor
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    ABSTRACT: Despite numerous studies on the neural basis of numerical processing, few studies have examined the neural substrates of one of the most basic numerical processing-number sequence recitation. The present study used fMRI to investigate neural substrates of number sequence recitation, focusing on the intraparietal sulcus (IPS) and perisylvian areas. This study used a 2 (number versus alphabet) x 2 (forward versus backward recitation) design. 12 Chinese undergraduates were asked to recite overtly but gently numerical and alphabetical sequences forward and backward. Results showed that, for both numerical and alphabetic sequences, the left IPS was activated when performing backward recitation, but not when performing forward recitation. In terms of perisylvian areas, all four tasks elicited activation in bilateral superior temporal gyrus and inferior frontal gyrus, but forward recitation elicited greater activation in the left posterior superior temporal gyrus than did backward recitation, whereas backward recitation elicited greater activation in the left inferior frontal gyrus than did forward recitation. These results suggest that forward recitation of numbers and the alphabet is typically based on verbal processing of numbers implemented in the perisylvian area, whereas backward recitation would likely require additional neural resources in the IPS.
    Brain Research 08/2006; 1099(1):109-20. · 2.88 Impact Factor
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    ABSTRACT: The purpose of this study was to examine the neurocognitive network for processing visual word forms in native Chinese speakers using functional magnetic resonance imaging (fMRI). In order to compare the processing of phonological and semantic representations, we developed parallel rhyming and meaning association judgment tasks that required explicit access and manipulation of these representations. Subjects showed activation in left inferior/middle frontal gyri, bilateral medial frontal gyri, bilateral middle occipital/fusiform gyri, and bilateral cerebella for both the rhyming and meaning tasks. A direct comparison of the tasks revealed that the rhyming task showed more activation in the posterior dorsal region of the inferior/middle frontal gyrus (BA 9/44) and in the inferior parietal lobule (BA 40). The meaning task showed more activation in the anterior ventral region of the inferior/middle frontal gyrus (BA 47) and in the superior/middle temporal gyrus (BA 22,21). These findings are consistent with previous studies in English that suggest specialization of inferior frontal regions for the access and manipulation of phonological vs. semantic representations, but also suggest that this specialization extends to the middle frontal gyrus for Chinese. These findings are also consistent with the suggestion that the left middle temporal gyrus is involved in representing semantic information and the left inferior parietal lobule is involved in mapping between orthographic and phonological representations.
    Brain Research 03/2006; 1071(1):197-207. · 2.88 Impact Factor
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    ABSTRACT: Neuropsychologists have debated over whether the processing of segmental and suprasegmental units involves different neural mechanisms. Focusing on the production of Chinese lexical tones (suprasegmental units) and vowels (segmental units), this study used the adaptation paradigm to investigate a possible neural dissociation for tone and vowel production. Ten native Chinese speakers were asked to name Chinese characters and pinyin (Romanized phonetic system for Chinese language) that varied in terms of tones and vowels. fMRI results showed significant differences in the right inferior frontal gyrus between tone and vowel production (more activation for tones than for vowels). Brain asymmetry analysis further showed that tone production was less left-lateralized than vowel production, although both showed left-hemisphere dominance.
    NeuroImage 02/2006; 29(2):515-23. · 6.25 Impact Factor
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    ABSTRACT: Functional magnetic resonance imaging (fMRI) was used to detect the cerebral cortical somatotopy during maximum voluntary clenching with and without soft splint in patients with hemimasticatory spasms (HMS) and the central mechanisms of HMS and the rule of the splint therapy. Four HMS patients were selected and the spasms sides were right in two cases and left in the other two cases. FMRI images were obtained on Elscint/GE 2.0 Tesla MR system. Block design was used and the movement pattern was the onset of spasms after maximum voluntary clenching with and without soft splint. The fMRI data were analyzed by SPM99 software. With the onset of spasms after maximum voluntary clenching, the activation of motor cortex in 3 HMS patients was found lateral dominance on the left side, and the other one showed bilateral activation. All the 4 patients were found activation in cingulate area. With the onset of spasms after maximum clenching wearing soft splints, the activation of motor cortex showed no lateral dominance on the left side, and 3 patients were not found activation in cingulate area. The changes of the activation in motor cortex and cingulate area during the onset of spasms after clenching with and without soft splint might be the central mechanisms of the rule of splint therapy, through which the soft splint might function in alleviating muscle pain.
    Zhonghua kou qiang yi xue za zhi = Zhonghua kouqiang yixue zazhi = Chinese journal of stomatology 02/2006; 41(1):37-40.
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    ABSTRACT: Using event-related functional magnetic resonance imaging to study the Stroop effect on both behavioral and brain activation of ADHD children off or on methylphenidate (MPH). Nine ADHD boys (aged 9.8-14.5 years) and 9 age-matched normal controls were included. A Stroop-like paradigm was used. AFNI (Analysis of Functional NeuroImaging) and its Deconvolution Analysis were used in a descriptive comparison between ADHD and control groups. (1) Both behavioral reaction time and brain activation showed Stroop effect in controls but neither was found in ADHD children off MPH. When MPH was administered, the Stroop effect tended to appear. (2) The activation volume (AV) of prefrontal cortex (PFC) in both the neutral (NC) and interference conditions (IC) in ADHD children off MPH was smaller than in controls. AV of anterior cingulate cortex in the IC in ADHD children off MPH was smaller than that in controls, but was similar in the NC to that in controls. AV of the basal ganglia, insula and cerebellum was also smaller in the IC, but was larger in the NC for ADHD children off MPH compared with controls. These findings are consistent with prior findings of hypofrontality in ADHD children and implicate a compensatory network including basal ganglia, insula and cerebellum for relative lower cognitive load tasks.
    Brain and Development 01/2006; 27(8):544-50. · 1.67 Impact Factor
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    ABSTRACT: Using functional magnetic resonance imaging (fMRI) to detect the cerebral cortical somatotopy during maximum voluntary clenching with soft occlusal pad in healthy adults. By comparing with the cerebral cortical activation during clenching with and without soft occlusal pad we try to detect the central mechanism of the rule of the occlusal pad. Ten healthy subjects were selected and scanned by Elscint/GE 2.0 Tesla MR system. Block design was used and the movement pattern was maximum voluntary clenching with soft occlusal pad. The fMRI data were analyzed by SPM99 software and group map analysis was done. The activation areas were found in bilateral or unilateral motor cortex, somatosensory cortex, prefrontal cortex, temporal cortex, premotor cortex, insula, frontal operculum, basal ganglia (putamen), parietal cortex and cingulate. Group map analysis showed activation in bilateral motor cortex, right somatosensory cortex, bilateral basal ganglia, and bilateral insula. The activation of left motor cortex was significantly higher than right side. Compared with cortical activation without occlusal pad, the motor and somatosensory cortex changed a lot. The changes of the activation of motor and somatosensory cortex during clenching after wearing the soft occlusal pad might be the central mechanism of the rule of the occlusal pad.
    Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 03/2005; 23(1):57-9.
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    ABSTRACT: Functional magnetic resonance imaging was used to investigate whether people generate the phonology of briefly presented words that they do not attend. This was done in Chinese by examining the effect of orthography-phonology regularity (i.e., how predictable the phonology of a word is from its components rather than whole-word form) with high- and low-frequency words, and by using a task that diverted participants' attention to a mask, rather than the words. The results showed that there was a significant interaction between regularity and word frequency in blood oxygen level-dependent (BOLD) signal, which mirrored the pattern found in behavioral data. Specifically, for low-frequency characters, bilateral fusiform gyri, the posterior superior temporal gyrus, and inferior parietal regions were more active when using irregular compared to regular characters. There were no significant differences when high-frequency characters were used. These results support the possibility that at least for low-frequency words, phonology is automatically generated when reading, even when people do not attend to the words and even in a language where the orthography-phonology mapping is extremely irregular.
    Cognitive Brain Research 08/2004; 20(2):156-64. · 3.77 Impact Factor
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    ABSTRACT: Brain activity was measured with fMRI in twelve 10- to 12-year-old Chinese children who began learning English when they were 8 years old in order to find out whether there is a common or a distinct neural semantic system for native language (L1) and second language (L2) in low proficiency bilingual subjects. Although they performed less well in L2 in the semantic decision task administered during fMRI measurement, these subjects showed similar robust activation, for both languages, in brain areas involved in semantic processing (e.g. the left inferior frontal cortex). Within-subject and group analyses revealed no significant difference in the activation patterns for L1 and L2 in these regions. These results suggest that at least at single-word level, there are shared neural substrates for semantic processing of L1 and L2 even when one is at a very low L2 proficiency level.
    Neuroreport 05/2004; 15(5):791-6. · 1.40 Impact Factor
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    ABSTRACT: We tested whether the stimulation of acupoints in the same spinal segments could induce different central responses with functional magnetic resonance imaging (fMRI) study. Stimulation of acupoints ST36/SP6 (Zusanli/Sanyinjiao) or GB34/BL57 (Yanglingquan/Chengshan) both activated primary and secondary somatosensory area, insula, ventral thalamus, parietal Brodmann Area 40, temporal lobe, putamen, and cerebellum, while de-activated amygdala. Nevertheless, ST36/SP6 stimulation specifically activated orbital frontal cortex and de-activated hippocampus. Alternatively, stimulation of GB34/BL57 activated dorsal thalamus and inhibited those of primary motor area and premotor cortex. Thus, stimulation of acupoints in the same spinal segments induced distinct though overlapped cerebral response patterns, which indicated the existence of acupoint specificity.
    Neuroscience Letters 02/2004; 354(1):50-3. · 2.03 Impact Factor
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    ABSTRACT: The purpose of this study is to investigate the modulation of pain responses in the human brain by electric acupoint stimulation (EAS). Eight healthy subjects were enrolled; each received real or mock EAS treatment in separate sessions. Cool (18 degrees C) and cold (2 degrees C) stimuli were delivered, during which functional magnetic resonance imaging scans were performed, before and after treatment. Real EAS specifically increased the pain-specific activation in bilateral secondary somatosensory area, medial prefrontal cortex, and Brodmann area (BA) 32, while it decreased the activation in contralateral primary somatosensory area, BA7, and BA24. We suggest that EAS may induce an analgesic effect via modulation of both the sensory and the emotional aspect of pain processing.
    Neuroreport 09/2003; 14(12):1591-6. · 1.40 Impact Factor
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    ABSTRACT: Two- or 100-Hz electrical acupoint stimulation (EAS) can induce analgesia via distinct central mechanisms. It has long been known that the extent of EAS analgesia showed tremendous difference among subjects. Functional MRI (fMRI) studies were performed to allocate the possible mechanisms underlying the frequency specificity as well as individual variability of EAS analgesia. In either frequencies, the averaged fMRI activation levels of bilateral secondary somatosensory area and insula, contralateral anterior cingulate cortex and thalamus were positively correlated with the EAS-induced analgesic effect across the subjects. In 2-Hz EAS group, positive correlations were observed in contralateral primary motor area, supplementary motor area, and ipsilateral superior temporal gyrus, while negative correlations were found in bilateral hippocampus. In 100-Hz EAS group, positive correlations were observed in contralateral inferior parietal lobule, ipsilateral anterior cingulate cortex, nucleus accumbens, and pons, while negative correlation was detected in contralateral amygdala. These results suggest that functional activities of certain brain areas might be correlated with the effect of EAS-induced analgesia, in a frequency-dependent dynamic. EAS-induced analgesia with low and high frequencies seems to be mediated by different, though overlapped, brain networks. The differential activations/de-activations in brain networks across subjects may provide a neurobiological explanation for the mechanisms of the induction and the individual variability of analgesic effect induced by EAS, or that of manual acupuncture as well.
    Brain Research 09/2003; 982(2):168-78. · 2.88 Impact Factor
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    ABSTRACT: The neural basis of the automatic activation of words was investigated in an fMRI study. In the study, words were presented briefly (51 or 151 msec) followed by a mask. To prevent attentional processing, subjects attended to the masks and not the words, and were required to make perceptual judgment about the masks. We found that a distributed neural network (including the frontal, temporal, occipital, parietal lobes, and the cerebellum) was activated during non-attentional processing of words in both exposure durations. A significant main effect of presentation duration was found in bilateral cerebellum and the right fusiform gyrus, suggesting their role in the later (151 msec) processing of words. In addition, a significant interaction between presentation duration and word frequency was obtained. When the presentation duration was 151 msec, no significant difference in activation was found between high- and low-frequency words. Alternatively, when the presentation duration was 51 msec, high-frequency words evoked significantly greater activation in bilateral fusiform gyri, cerebellum, right inferior parietal lobe, medial frontal gyrus (BA 45/46/9), and the right temporal-occipital junction (BA 21/37). These results suggest that these regions are sensitive to word frequency, and are related to both the attentional and non-attentional access of lexical representations.
    Human Brain Mapping 04/2003; 18(3):215-21. · 6.88 Impact Factor
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    ABSTRACT: The neural basis of the automatic activation of words was investigated in an fMRI study. In the study, words were presented briefly (51 or 151 msec) followed by a mask. To prevent attentional processing, subjects attended to the masks and not the words, and were required to make perceptual judgment about the masks. We found that a distributed neural network (including the frontal, temporal, occipital, parietal lobes, and the cerebellum) was activated during non-attentional processing of words in both exposure durations. A significant main effect of presentation duration was found in bilateral cerebellum and the right fusiform gyrus, suggesting their role in the later (151 msec) processing of words. In addition, a significant interaction between presentation duration and word frequency was obtained. When the presentation duration was 151 msec, no significant difference in activation was found between high- and low-frequency words. Alternatively, when the presentation duration was 51 msec, high-frequency words evoked significantly greater activation in bilateral fusiform gyri, cerebellum, right inferior parietal lobe, medial frontal gyrus (BA 45/46/9), and the right temporal-occipital junction (BA 21/37). These results suggest that these regions are sensitive to word frequency, and are related to both the attentional and non-attentional access of lexical representations. Hum. Brain Mapping 18:215--221, 2003. 2003 Wiley-Liss, Inc.
    03/2003;

Publication Stats

417 Citations
33.61 Total Impact Points

Institutions

  • 2006
    • Shanghai Normal University
      Shanghai, Shanghai Shi, China
  • 2005
    • Peking University School of Stomatology
      Peping, Beijing, China
  • 2003–2004
    • Peking University
      • Neuroscience Research Institute
      Beijing, Beijing Shi, China