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581.
Corey J. Keller Christopher J. Honey Pierre Mégevand Laszlo Entz Istvan Ulbert Ashesh D. Mehta 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1653)
The cerebral cortex forms a sheet of neurons organized into a network of interconnected modules that is highly expanded in humans and presumably enables our most refined sensory and cognitive abilities. The links of this network form a fundamental aspect of its organization, and a great deal of research is focusing on understanding how information flows within and between different regions. However, an often-overlooked element of this connectivity regards a causal, hierarchical structure of regions, whereby certain nodes of the cortical network may exert greater influence over the others. While this is difficult to ascertain non-invasively, patients undergoing invasive electrode monitoring for epilepsy provide a unique window into this aspect of cortical organization. In this review, we highlight the potential for cortico-cortical evoked potential (CCEP) mapping to directly measure neuronal propagation across large-scale brain networks with spatio-temporal resolution that is superior to traditional neuroimaging methods. We first introduce effective connectivity and discuss the mechanisms underlying CCEP generation. Next, we highlight how CCEP mapping has begun to provide insight into the neural basis of non-invasive imaging signals. Finally, we present a novel approach to perturbing and measuring brain network function during cognitive processing. The direct measurement of CCEPs in response to electrical stimulation represents a potentially powerful clinical and basic science tool for probing the large-scale networks of the human cerebral cortex. 相似文献
582.
Cross-Reaction of Predominant Nitrogen-Fixing Bacteria with Enveloped, Round Bodies in the Root Interior of Kallar Grass 总被引:5,自引:0,他引:5 下载免费PDF全文
Diazotrophic rods occurring in high numbers (about 108 rods per g [dry weight] of root) in the root interior of Kallar grass were localized by indirect immunofluorescence in cross sections of the same roots. Specifically stained round bodies which were apparently covered by a nonantigenic envelope were found in the aerenchymatic tissue. 相似文献
583.
Istvan Botos Lin Liu Yan Wang David M. Segal David R. Davies 《Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms》2009,1789(9-10):667-674
Toll-like receptors (TLRs) recognize conserved molecular patterns in invading pathogens and trigger innate immune responses. TLR3 recognizes dsRNA, a molecular signature of most viruses via its ectodomain (ECD). The TLR3-ECD structure consists of a 23 turn coil bent into the shape of a horseshoe with specialized domains capping the N and C-terminal ends of the coil. TLR3-ECDs bind as dimeric units to dsRNA oligonucleotides of at least 45 bp in length, the minimal length required for signal transduction. X-ray analysis has shown that each TLR3-ECD of a dimer binds dsRNA at two sites located at opposite ends of the TLR3 “horseshoe” on the one lateral face that lacks N-linked glycans. Intermolecular contacts between the C-terminal domains of two TLR3-ECDs stabilize the dimer and position the C-terminal residues within 20–25 Å of each other, which is thought to be essential for transducing a signal across the plasma membrane in intact TLR3 molecules. Interestingly, in TLRs 1, 2 and 4, which bind lipid ligands using very different interactions from TLR3, the ligands nevertheless promote the formation of a dimer in which the same two lateral surfaces as in the TLR3-ECD:dsRNA complex face each other, bringing their C-termini in close proximity. Thus, a pattern is emerging in which pathogen-derived substances bind to TLR-ECDs, thereby promoting the formation of a dimer in which the glycan-free ligand binding surfaces face each other and the two C-termini are brought in close proximity for signal transduction. 相似文献
584.