共查询到20条相似文献,搜索用时 15 毫秒
1.
Mikhaĭlova ES Chicherov VA Ptushenko EA Shevelev IA 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2008,58(3):302-308
In 12 adult healthy subjects we studied Brain-Computer-Interface recognition of different intended letters by the square of P300 wave in the averaged VEP. Horizontal and vertical spatial gradient of this square was studied as well as tuning acuteness of visual attention to a significant letter. High acuteness of this tuning was found (width of the tuning curve at its half height was equal to 1.6 grad) independent of the letter position on the letter matrix. Horizontal and vertical gradient of P300 were found to be very similar, but in the half of cases the first one revealed some kind of the "lateral inhibition": decrease of P300 square for the columns neighboring to the meaningful one. Tuning acuteness was found to be reliable and directly interrelated with P300 square. The data are discussed in relation to selectivity of the local visual attention. 相似文献
2.
Chih-Wei Chen Ming-Shaung Ju Yun-Nien Sun Chou-Ching K. Lin 《Journal of computational neuroscience》2009,27(3):357-368
The primary goal of this study was to construct a simulation model of a biofeedback brain-computer interface (BCI) system to analyze the effect of biofeedback training on BCI users. A mathematical model of a man-machine visual-biofeedback
BCI system was constructed to simulate a subject using a BCI system to control cursor movements. The model consisted of a
visual tracking system, a thalamo-cortical model for EEG generation, and a BCI system. The BCI system in the model was realized
for real experiments of visual biofeedback training. Ten sessions of visual biofeedback training were performed in eight normal
subjects during a 3-week period. The task was to move a cursor horizontally across a screen, or to hold it at the screen’s
center. Experimental conditions and EEG data obtained from real experiments were then simulated with the model. Three model
parameters, representing the adaptation rate of gain in the visual tracking system and the relative synaptic strength between
the thalamic reticular and thalamo-cortical cells in the Rolandic areas, were estimated by optimization techniques so that
the performance of the model best fitted the experimental results. The serial changes of these parameters over the ten sessions,
reflecting the effects of biofeedback training, were analyzed. The model simulation could reproduce results similar to the
experimental data. The group mean success rate and information transfer rate improved significantly after training (56.6 to
81.1% and 0.19 to 0.76 bits/trial, respectively). All three model parameters displayed similar and statistically significant
increasing trends with time. Extensive simulation with systematic changes of these parameters also demonstrated that assigning
larger values to the parameters improved the BCI performance. We constructed a model of a biofeedback BCI system that could
simulate experimental data and the effect of training. The simulation results implied that the improvement was achieved through
a quicker adaptation rate in visual tracking gain and a larger synaptic gain from the visual tracking system to the thalamic
reticular cells. In addition to the purpose of this study, the constructed biofeedback BCI model can also be used both to
investigate the effects of different biofeedback paradigms and to test, estimate, or predict the performances of other newly
developed BCI signal processing algorithms. 相似文献
3.
N Sonenberg J Pelletier 《BioEssays : news and reviews in molecular, cellular and developmental biology》1989,11(5):128-132
All eukaryotic cellular mRNAs, and most viral mRNAs, are blocked at their 5' ends with a cap structure (m7GpppX, where X is any nucleotide). Poliovirus, along with a small number of other animal and plant viral mRNAs, does not contain a 5' cap structure. Since the cap structure functions to facilitate ribosome binding to mRNA, translation of polio-virus must proceed by a cap-independent mechanism. Consistent with this, recent studies have shown that ribosomes can bind to an internal region within the long 5' noncoding sequence of poliovirus RNA. Possible mechanisms for cap-independent translation are discussed. Cap-independent translation of poliovirus RNA is of major importance to the mechanism of shut-off of host protein synthesis after infection. Moreover, it is likely to play a role in determining poliovirus neurovirulence and attenuation. 相似文献
4.
Walter J. Freeman 《Cognitive neurodynamics》2007,1(1):3-14
Neocortical state variables are defined and evaluated at three levels: microscopic using multiple spike activity (MSA), mesoscopic
using local field potentials (LFP) and electrocorticograms (ECoG), and macroscopic using electroencephalograms (EEG) and brain
imaging. Transactions between levels occur in all areas of cortex, upwardly by integration (abstraction, generalization) and
downwardly by differentiation (speciation). The levels are joined by circular causality: microscopic activity upwardly creates
mesoscopic order parameters, which downwardly constrain the microscopic activity that creates them. Integration dominates
in sensory cortices. Microscopic activity evoked by receptor input in sensation induces emergence of mesoscopic activity in
perception, followed by integration of perceptual activity into macroscopic activity in concept formation. The reverse process
dominates in motor cortices, where the macroscopic activity embodying the concepts supports predictions of future states as
goals. These macroscopic states are conceived to order mesoscopic activity in patterns that constitute plans for actions to
achieve the goals. These planning patterns are conceived to provide frames in which the microscopic activity evolves in trajectories
that adapted to the immediate environmental conditions detected by new stimuli. This circular sequence forms the action-perception
cycle. Its upward limb is understood through correlation of sensory cortical activity with behavior. Now brain-machine interfaces
(BMI) offer a means to understand the downward sequence through correlation of behavior with motor cortical activity, beginning
with macroscopic goal states and concluding with recording of microscopic MSA trajectories that operate neuroprostheses. Part
1 develops a hypothesis that describes qualitatively the neurodynamics that supports the action-perception cycle and derivative
reflex arc. Part 2 describes episodic, “cinematographic” spatial pattern formation and predicts some properties of the macroscopic
and mesoscopic frames by which the embedded trajectories of the microscopic activity of cortical sensorimotor neurons might
be organized and controlled.
URL: http://sulcus.berkeley.edu 相似文献
5.
Bobrov PD Korshakov AV Roshchin VIu Frolov AA 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2012,62(1):89-99
This paper proposes Bayesian approach to classification of EEG patterns on the basis of imaginary movements of extremities based on analysis ofcovariance matrices of native EEG recordings. An efficacy of a Brain-Computer Interface (BCI) based on the proposed classifier is evaluated. Bayesian classifier is shown to be competitive with the MCSP (Multiclass Common Spatial Patterns) classifier known from the literature as one of the efficient variant for BCI implementation. The influence of eye movement and blinking artifacts on the BCI performance is investigated. It is shown that the presence of such artifacts does not affect the classification accuracy. 相似文献
6.
The P300 brain-computer interface (BCI) is currently the most efficient BCI. This interface is based on detection of the P300 wave of the brain potentials evoked when a symbol related to the intended input is highlighted. To increase operation speed of the P300 BCI, reduction of the number of stimuli repetitions is needed. This reduction leads to increase of the relative contribution to the input symbol detection from the reaction to the first target stimulus. It is known that the event-related potentials (ERP) to the first stimulus presentations can be different from the ERP to stimuli presented latter. In particular, the amplitude of responses to the first stimulus presentations is often increased, which is beneficial for their recognition by the BCI. However, this effect was not studied within the BCI framework. The current study examined the ERP obtained from healthy participants (n = 14) in the standard P300 BCI paradigm using 10 trials, as well as in the modified P300 BCI with stimuli presented on moving objects in triple-trial (n = 6) and single-trial (n = 6) stimulation modes. Increased ERP amplitude was observed in response to the first target stimuli in both conditions, as well as in the single-trial mode comparing to triple-trial. We discuss the prospects of using the specific features of the ERP to first stimuli and the single-trial ERP for optimizing the high-speed modes in the P300 BCIs. 相似文献
7.
Continuous three-dimensional control of a virtual helicopter using a motor imagery based brain-computer interface 总被引:1,自引:0,他引:1
Brain-computer interfaces (BCIs) allow a user to interact with a computer system using thought. However, only recently have devices capable of providing sophisticated multi-dimensional control been achieved non-invasively. A major goal for non-invasive BCI systems has been to provide continuous, intuitive, and accurate control, while retaining a high level of user autonomy. By employing electroencephalography (EEG) to record and decode sensorimotor rhythms (SMRs) induced from motor imaginations, a consistent, user-specific control signal may be characterized. Utilizing a novel method of interactive and continuous control, we trained three normal subjects to modulate their SMRs to achieve three-dimensional movement of a virtual helicopter that is fast, accurate, and continuous. In this system, the virtual helicopter's forward-backward translation and elevation controls were actuated through the modulation of sensorimotor rhythms that were converted to forces applied to the virtual helicopter at every simulation time step, and the helicopter's angle of left or right rotation was linearly mapped, with higher resolution, from sensorimotor rhythms associated with other motor imaginations. These different resolutions of control allow for interplay between general intent actuation and fine control as is seen in the gross and fine movements of the arm and hand. Subjects controlled the helicopter with the goal of flying through rings (targets) randomly positioned and oriented in a three-dimensional space. The subjects flew through rings continuously, acquiring as many as 11 consecutive rings within a five-minute period. In total, the study group successfully acquired over 85% of presented targets. These results affirm the effective, three-dimensional control of our motor imagery based BCI system, and suggest its potential applications in biological navigation, neuroprosthetics, and other applications. 相似文献
8.
9.
Balzarini J 《Nature reviews. Microbiology》2007,5(8):583-597
Several chronic viral infections (such as HIV and hepatitis C virus) are highly prevalent and are a serious health risk. The adaptation of animal viruses to the human host, as recently exemplified by influenza viruses and the severe acute respiratory syndrome coronavirus, is also a continuous threat. There is a high demand, therefore, for new antiviral lead compounds and novel therapeutic concepts. In this Review, an original therapeutic concept for suppressing enveloped viruses is presented that is based on a specific interaction of carbohydrate-binding agents (CBAs) with the glycans present on viral-envelope glycoproteins. This approach may also be extended to other pathogens, including parasites, bacteria and fungi. 相似文献
10.
11.
Urmas Kõljalg R. Henrik Nilsson Kessy Abarenkov Leho Tedersoo Andy F. S. Taylor Mohammad Bahram Scott T. Bates Thomas D. Bruns Johan Bengtsson‐Palme Tony M. Callaghan Brian Douglas Tiia Drenkhan Ursula Eberhardt Margarita Dueñas Tine Grebenc Gareth W. Griffith Martin Hartmann Paul M. Kirk Petr Kohout Ellen Larsson Björn D. Lindahl Robert Lücking María P. Martín P. Brandon Matheny Nhu H. Nguyen Tuula Niskanen Jane Oja Kabir G. Peay Ursula Peintner Marko Peterson Kadri Põldmaa Lauri Saag Irja Saar Arthur Schüßler James A. Scott Carolina Senés Matthew E. Smith Ave Suija D. Lee Taylor M. Teresa Telleria Michael Weiss Karl‐Henrik Larsson 《Molecular ecology》2013,22(21):5271-5277
The nuclear ribosomal internal transcribed spacer (ITS) region is the formal fungal barcode and in most cases the marker of choice for the exploration of fungal diversity in environmental samples. Two problems are particularly acute in the pursuit of satisfactory taxonomic assignment of newly generated ITS sequences: (i) the lack of an inclusive, reliable public reference data set and (ii) the lack of means to refer to fungal species, for which no Latin name is available in a standardized stable way. Here, we report on progress in these regards through further development of the UNITE database ( http://unite.ut.ee ) for molecular identification of fungi. All fungal species represented by at least two ITS sequences in the international nucleotide sequence databases are now given a unique, stable name of the accession number type (e.g. Hymenoscyphus pseudoalbidus|GU586904|SH133781.05FU), and their taxonomic and ecological annotations were corrected as far as possible through a distributed, third‐party annotation effort. We introduce the term ‘species hypothesis’ (SH) for the taxa discovered in clustering on different similarity thresholds (97–99%). An automatically or manually designated sequence is chosen to represent each such SH. These reference sequences are released ( http://unite.ut.ee/repository.php ) for use by the scientific community in, for example, local sequence similarity searches and in the QIIME pipeline. The system and the data will be updated automatically as the number of public fungal ITS sequences grows. We invite everybody in the position to improve the annotation or metadata associated with their particular fungal lineages of expertise to do so through the new Web‐based sequence management system in UNITE. 相似文献
12.
13.
Moran D 《Current opinion in neurobiology》2010,20(6):741-745
Brain computer interfaces (BCIs) were originally developed to give severely motor impaired patients a method to communicate and interact with their environment. Initially most BCI systems were based on non-invasive electroencephalographic recordings from the surface of the scalp. To increase control speed, accuracy and complexity, researchers began utilizing invasive recording modalities. BCIs using multi-single unit action potentials have provided elegant multi-dimensional control of both computer cursors and robotic limbs in the last few years. However, long-term stability issues with single-unit arrays has lead researchers to investigate other invasive recording modalities such as high-frequency local field potentials and electrocorticography (ECoG). Although ECoG originally evolved as a replacement for single-unit BCIs, it has come full circle to become an effective tool for studying cortical neurophysiology. 相似文献
14.
15.
Contemporary knowledge of impressive neurophysiology and behavior in cetaceans, combined with increasing opportunities for studying free-ranging cetaceans who initiate sociable interaction with humans, are converging to highlight serious ethical considerations and emerging opportunities for a new era of progressive and less-invasive cetacean research. Most research on cetacean cognition has taken place in controlled captive settings, e.g., research labs, marine parks. While these environments afford a certain amount of experimental rigor and logistical control they are fraught with limitations in external validity, impose tremendous stress on the part of the captive animals, and place burdens on populations from which they are often captured. Alternatively, over the past three decades, some researchers have sought to focus their attention on the presence of free-ranging cetacean individuals and groups who have initiated, or chosen to participate in, sociable interactions with humans in the wild. This new approach, defined as Interspecies Collaborative Research between cetacean and human, involves developing novel ways to address research questions under natural conditions and respecting the individual cetacean's autonomy. It also offers a range of potential direct benefits to the cetaceans studied, as well as allowing for unprecedented cognitive and psychological research on sociable mysticetes. Yet stringent precautions are warranted so as to not increase their vulnerability to human activities or pathogens. When conducted in its best and most responsible form, collaborative research with free-ranging cetaceans can deliver methodological innovation and invaluable new insights while not necessitating the ethical and scientific compromises that characterize research in captivity. Further, it is representative of a new epoch in science in which research is designed so that the participating cetaceans are the direct recipients of the benefits. 相似文献
16.
Musso Munyeme John B Muma Hetron M Munang'andu Clovice Kankya Eystein Skjerve Morten Tryland 《BMC veterinary research》2010,6(1):21
Background
Awareness of bovine tuberculosis (BTB) by cattle owners is of extreme importance to policy makers when considering mitigation. However, to our knowledge, little is known on cattle owners' awareness of BTB in Zambia. Similarly, such knowledge is uncommon within and outside Africa. The current study investigates the epidemiological characteristics of BTB in Zambian cattle in relation to awareness by cattle owners in high and low cattle BTB prevalence settings. A cross sectional study was designed and data was gathered based on 106 cattle owners and cattle herds; subjected to an interviewer-administered questionnaire and comparative intradermal tuberculin test using a cut-off for positivity of 4 mm, respectively. 相似文献17.
Sowmyalakshmi Srinivasan Raj Kumar Srinivas Koduru Aaditya Chandramouli Chendil Damodaran 《Apoptosis : an international journal on programmed cell death》2010,15(2):153-161
The tumor necrosis factor (TNF) receptor super family comprises of members that induce two distinct signaling cascades, leading
to either cell survival or apoptosis. However, in prostate cancer (PCa), TNF-mediated prosurvival signaling is the predominant
pathway that leads to cell survival and resistance to therapy. Although inhibition of TNF signaling by pharmacological agents
or monoclonal antibodies has gained importance in the field of cancer therapy, toxicity to normal cells has impaired their
extensive use for cancer treatment. We previously identified a natural, nontoxic compound psoralidin that inhibited viability
and induced apoptosis in androgen independent prostate cancer (AIPC) cells. Thus, the goal of our study is to investigate
whether psoralidin inhibits TNF-mediated prosurvival signaling in AIPC cells. Our results suggest that psoralidin inhibits
constitutive and TNF-induced expression of TNF-α and its downstream prosurvival signaling molecules such as NF-κB and Bcl-2
in AIPC cells. On the other hand, psoralidin simultaneously induces the death receptor (DR)-mediated apoptotic signaling eventually
causing the activation of caspase cascade and resultant induction of apoptosis. Oral administration of psoralidin inhibits
expression of TNF-α and NF-κB/p65 in tumor sections, resulting in tumor regression in PC-3 xenografts. Our results suggest
that psoralidin inhibits TNF-mediated survival signaling in AIPC and thus is a potent therapeutic agent for prostate cancer. 相似文献
18.
Vladislav Strmiska Petr Michalek Tomas Eckschlager Marie Stiborova Vojtech Adam Sona Krizkova Zbynek Heger 《生物化学与生物物理学报:癌评论》2019,1871(2):248-258
So far multiple differences in prostate cancer-specific amino acids metabolism have been discovered. Moreover, attempts to utilize these alterations for prostate cancer diagnosis and treatment have been made. The prostate cancer metabolism and biosynthesis of amino acids are particularly focused on anaplerosis more than on energy production. Other crucial requirements on amino acids pool come from the serine, one?carbon cycle, glycine synthesis pathway and folate metabolism forming major sources of interproducts for synthesis of nucleobases necessary for rapidly proliferating cells. Considering the lack of some amino acids biosynthetic pathways and/or their extraordinary importance for prostate cancer cells, there is a widespread potential for targeted therapeutic applications with no effect on non-malignant cells. This review summarizes the up-to-date knowledge of the importance of amino acids for prostate cancer pathogenesis with a special emphasis on potential applications of metabolic variabilities in the new oncologic paradigm of precision medicine. 相似文献
19.
O Shatursky A P Heuck L A Shepard J Rossjohn M W Parker A E Johnson R K Tweten 《Cell》1999,99(3):293-299
Perfringolysin O (PFO), a water-soluble monomeric cytolysin secreted by pathogenic Clostridium perfringens, oligomerizes and forms large pores upon encountering cholesterol-containing membranes. Whereas all pore-forming bacterial toxins examined previously have been shown to penetrate the membrane using a single amphipathic beta hairpin per polypeptide, cysteine-scanning mutagenesis and multiple independent fluorescence techniques here reveal that each PFO monomer contains a second domain involved in pore formation, and that each of the two amphipathic beta hairpins completely spans the membrane. In the soluble monomer, these transmembrane segments are folded into six alpha helices. The insertion of two transmembrane hairpins per toxin monomer and the major change in secondary structure are striking and define a novel paradigm for the mechanism of membrane insertion by a cytolytic toxin. 相似文献
20.
Klompas M Khan Y Kleinman K Evans RS Lloyd JF Stevenson K Samore M Platt R;CDC Prevention Epicenters Program 《PloS one》2011,6(3):e18062