Biomedical subjects

Ming Meng

Publications and source records attributed to Ming Meng.

7 recordsLinked to original sources

PubMed2006

Neural bases of binocular rivalry.

During binocular rivalry, conflicting monocular images compete for access to consciousness in a stochastic, dynamical fashion. Recent human neuroimaging and psychophysical studies suggest that rivalry entails competitive interactions at multiple neural sites, including sites that retain eye-selective information. Rivalry greatly suppresses activity in the ventral pathway and attenuates visual adaptation to form and motion; nonetheless, some information about the suppressed stimulus reaches higher brain areas. Although rivalry depends on low-level inhibitory interactions, high-level excitatory influences promoting perceptual grouping and selective attention can extend the local dominance of a stimulus over space and time. Inhibitory and excitatory circuits considered within a hybrid model might account for the paradoxical properties of binocular rivalry and provide insights into the neural bases of visual awareness itself.

Animals↗

PubMed2005

Filling-in of visual phantoms in the human brain.

The constructive nature of perception can be demonstrated under viewing conditions that lead to vivid subjective impressions in the absence of direct input. When a low-contrast moving grating is divided by a large gap, observers report seeing a 'visual phantom' of the real grating extending through the blank gap region. Here, we report fMRI evidence showing that visual phantoms lead to enhanced activity in early visual areas that specifically represent the blank gap region. We found that neural filling-in effects occurred automatically in areas V1 and V2, regardless of where the subject attended. Moreover, when phantom-inducing gratings were paired with competing stimuli in a binocular rivalry display, subjects reported spontaneous fluctuations in conscious perception of the phantom accompanied by tightly coupled changes in early visual activity. Our results indicate that phantom visual experiences are closely linked to automatic filling-in of activity at the earliest stages of cortical processing.

Attention↗

PubMed2005

[The study on the relationship between the tumor-like proliferation of synoviocytes and the expression of c-myc and ODC genes in adjuvant arthritis rats].

AIM: To investigate the mechanism of the tumor-like proliferation of synoviocytes in adjuvant arthritis (AA) rats. METHODS: Wistar rats were randomly divided into 2 groups, AA group and control group. Freund's complete adjuvant was injected into AA group rats to induce adjuvant arthritis. The knee synovial tissues of the rats were taken and synoviocytes were separated and cultured in vitro. The proliferation of cultured synoviocytes was measured by MTT colorimetry. Meanwhile, the mRNAs of C-myc and ODC genes in synovial tissues of the rats were detected by semi-quantitative RT-PCR. RESULTS: (1)Synoviocytes of AA rats proliferated more markedly than those of control rats (P<0.01), and exhibited a tumor-like proliferation. (2)The mRNAs of C-myc and ODC genes were obviously higher in synovial tissues of AA rats than those of control rats. CONCLUSION: The tumor-like proliferation of synoviocytes from AA rat joint might be related to the increased mRNAs of C-myc and ODC genes.

Animals↗

PubMed2005

[Experimental study on anti-arthritis effect of jiawei mufangji decoction in rats].

OBJECTIVE: To explore the therapeutic effect of Jiawu Mufangji Decoction (JMD) in treating rats with adjuvant arthritis (AA) and its mechanism. METHODS: AA model rats induced by Freund's complete adjuvant were treated with JMD by gastrogavage starting from 18 days after modeling. On the 39th day, body weight, spleen and thymus index, and swelling degree of paw of the AA rats were measured, pathological changes of the ankle joint tissue were observed using HE staining, and serum levels of interleukin-1beta (IL-1beta) and tumor necrosis factor a (TNF-alpha) were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: JMD could relieve the symptoms of AA rats, decrease the paw swelling, improve the weight and spleen and thymus index, reduce the dropsy of joints and lymphocytes infiltration, inhibit the proliferation of synovium, and obviously lower the serum levels of interleukin-1beta and TNF-alpha. CONCLUSION: The therapeutic effect of JMD might be related to its action in down-regulating the serum levels of IL-1beta and tumor necrosis factor alpha.

Animals↗

PubMed2004

Can attention selectively bias bistable perception? Differences between binocular rivalry and ambiguous figures.

It is debated whether different forms of bistable perception result from common or separate neural mechanisms. Binocular rivalry involves perceptual alternations between competing monocular images, whereas ambiguous figures such as the Necker cube lead to alternations between two possible pictorial interpretations. Previous studies have shown that observers can voluntarily control the alternation rate of both rivalry and Necker cube reversal, perhaps suggesting that bistable perception results from a common mechanism of top-down selection. However, according to the biased competition model of selective attention, attention should be able to enhance the attended percept and suppress the unattended percept. Here, we investigated selective attentional modulation of dominance durations in bistable perception. Observers consistently showed much weaker selective attentional control for rivalry than for Necker cube reversal, even for rivalry displays that maximized the opportunities for feature-, object-, or space-based attentional selection. In contrast, nonselective control of alternation rate was comparably strong for both forms of bistable perception and corresponded poorly with estimates of selective attentional control. Our results support the notion that binocular rivalry involves a more automatic, stimulus-driven form of visual competition than Necker cube reversal, and as a consequence, is less easily biased by selective attention.

Attention↗

PubMed2004

Adsorption and thermal condensation mechanisms of amino acids on oxide supports. 1. Glycine on silica.

Glycine was adsorbed on the surface of a well-defined silica from aqueous solutions of variable concentrations and pHs. The adsorbed molecules were characterized using middle-IR and UV-vis-NIR spectroscopies. Except at the lowest pH (2.0), they were predominantly present on the surface as zwitterions. Two successive deposition mechanisms were evidenced with increasing glycine concentration. At low concentrations, glycine is specifically adsorbed on silica surface sites, probably through its NH3+ moiety. The pH dependence suggests that these sites may be silanolate groups (approximately equal to Si-O-). At higher concentrations, specific adsorption sites are saturated and surface-induced precipitation of beta-glycine is observed. The thermal reactivity of adsorbed/deposited glycine was then investigated by thermogravimetric analysis, in situ diffuse reflectance IR spectroscopy, and thermoprogrammed desorption coupled with mass spectrometry. Adsorbed glycine molecules react to form peptide bonds at a temperature considerably lower than that for bulk crystalline alpha-glycine. The main reaction product is the cyclic dimer diketopiperazine, with no evidence of the linear dimer. The activation mechanism is not diffusionally limited; the formation of "surface acyls", previously proposed for related systems, has not been evidenced here. These findings are of relevance for the evaluation of prebiotic peptide synthesis scenarios.

Adsorption↗

PubMed2003

Contributions of the visual ventral pathway to long-range apparent motion.

Objects displaced intermittently across the visual field will nonetheless give an illusion of continuous motion [called apparent motion (AM)] under many common conditions. It is believed that form perception is of minor importance in determining AM, and that AM is mediated by motion-sensitive areas in the "where" pathway of the cortex. However, form and motion typically interact in specific ways when natural objects move through the environment. We used functional magnetic resonance imaging to measure cortical activation to long-range AM, compared to short-range AM and flicker, while we varied stability of structural differences between forms. Long-range AM activated the anterior-temporal lobe in the visual ventral pathway, and the response varied according to the form stability. The results suggest that long-range AM is associated with neural systems for form perception.

Brain Mapping↗