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Signal Detection and Target Gene Induction by the CpxRA Two-Component System

DiGiuseppe, Patricia A.; Silhavy, Thomas J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2003 EN
Relevância na Pesquisa
35.88%
The Cpx pathway is a two-component signal transduction system that senses a variety of envelope stresses, including misfolded proteins, and responds by upregulating periplasmic folding and trafficking factors. CpxA resides in the inner membrane and has both kinase and phosphatase activities. CpxR, the response regulator, mediates a response by activating transcription of stress-combative genes. Signal transduction is subject to feedback inhibition via regulon member CpxP and autoamplification. Recently, it was shown that the Cpx pathway is also upregulated when cells adhere to hydrophobic surfaces and that this response is dependent on the outer membrane lipoprotein NlpE. Here we show that while NlpE is required for induction of the Cpx pathway by adhesion, induction by envelope stress and during growth is NlpE independent. We show that while all of the envelope stresses tested induce the Cpx pathway in a manner that is dependent on the periplasmic domain of CpxA, induction during growth is independent of CpxA. Therefore, we propose that the Cpx pathway can sense inducing cues that enter the signaling pathway at three distinct points. Although CpxP is not required for induction of the Cpx pathway, we show that its activity as a negative regulator of CpxA is inactivated by envelope stress. Moreover...

Investigation of the Role of Electrostatic Charge in Activation of the Escherichia coli Response Regulator CheY

Smith, Jenny G.; Latiolais, Jamie A.; Guanga, Gerald P.; Citineni, Sindhura; Silversmith, Ruth E.; Bourret, Robert B.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2003 EN
Relevância na Pesquisa
35.88%
In a two-component regulatory system, an important means of signal transduction in microorganisms, a sensor kinase phosphorylates a response regulator protein on an aspartyl residue, resulting in activation. The active site of the response regulator is highly charged (containing a lysine, the phosphorylatable aspartate, two additional aspartates involved in metal binding, and an Mg2+ ion), and introduction of the dianionic phosphoryl group results in the repositioning of charged moieties. Furthermore, substitution of one of the Mg2+-coordinating aspartates with lysine or arginine in the Escherichia coli chemotaxis response regulator CheY results in phosphorylation-independent activation. In order to examine the consequences of altered charge distribution for response regulator activity and to identify possible additional amino acid substitutions that result in phosphorylation-independent activation, we made 61 CheY mutants in which residues close to the site of phosphorylation (Asp57) were replaced by various charged amino acids. Most substitutions (47 of 61) resulted in the complete loss of CheY activity, as measured by the inability to support clockwise flagellar rotation. However, 10 substitutions, all introducing a new positive charge...

Regulation of Iron Transport in Streptococcus pneumoniae by RitR, an Orphan Response Regulator

Ulijasz, Andrew T.; Andes, David R.; Glasner, Jeremy D.; Weisblum, Bernard
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
Relevância na Pesquisa
35.86%
RitR (formerly RR489) is an orphan two-component signal transduction response regulator in Streptococcus pneumoniae that has been shown to be required for lung pathogenicity. In the present study, by using the rough strain R800, inactivation of the orphan response regulator gene ritR by allele replacement reduced pathogenicity in a cyclophosphamide-treated mouse lung model but not in a thigh model, suggesting a role for RitR in regulation of tissue-specific virulence factors. Analysis of changes in genome-wide transcript mRNA levels associated with the inactivation of ritR compared to wild-type cells was performed by the use of high-density DNA microarrays. Genes with a change in transcript abundance associated with inactivation of ritR included piuB, encoding an Fe permease subunit, and piuA, encoding an Fe carrier-binding protein. In addition, a dpr ortholog, encoding an H2O2 resistance protein that has been shown to reduce synthesis of reactive oxygen intermediates, was activated in the wild-type (ritR+) strain. Microarray experiments suggested that RitR represses Fe uptake in vitro by negatively regulating the Piu hemin-iron transport system. Footprinting experiments confirmed site-specific DNA-binding activity for RitR and identified three binding sites that partly overlap the +1 site for transcription initiation upstream of piuB. Transcripts belonging to other gene categories found to be differentially expressed in our array studies include those associated with (i) H2O2 resistance...

Picosecond and Nanosecond Components in Bacteriorhodopsin Light-Induced Electric Response Signal

Groma, G. I.; Ráksi, F.; Szabó, G.; Váró, G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1988 EN
Relevância na Pesquisa
45.76%
Numerous investigations on the primary events of the bacteriorhodopsin photocycle indicate that the first steps of the energy transformation process take place in the 500 fs-5 ps region. These processes are known to be followed by others in the μs and ms regions. Recent observations indicate also the existence of nanosecond intermediate(s). Here we are reporting on direct measurements of the light-induced electric response signal of purple membrane carried out in the ps and ns regions. The laser flash-induced electric response of dried oriented purple membrane samples were detected by an ultrafast sampling oscilloscope. The measured kinetic curves were analyzed by exponential fitting and by a simulation-optimization method taking into account the time characteristics of the measuring setup. This analysis revealed a two phase real charge separation process. The first phase (tau = 21 ± 2 ps) coincides well with the overall bR-[unk] K transition. The second phase (tau = 6 ± 0.5 ns) can be correlated with the nanosecond optical transitions reported by several workers, or may be an optically silent charge movement inside the protein moiety or on the surface of the membrane.

Mutationally Altered Signal Output in the Nart (NarX-Tar) Hybrid Chemoreceptor

Ward, Scott M.; Bormans, Arjan F.; Manson, Michael D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2006 EN
Relevância na Pesquisa
35.91%
Signal-transducing proteins that span the cytoplasmic membrane transmit information about the environment to the interior of the cell. In bacteria, these signal transducers include sensor kinases, which typically control gene expression via response regulators, and methyl-accepting chemoreceptor proteins, which control flagellar rotation via the CheA kinase and CheY response regulator. We previously reported that a chimeric protein (Nart) that joins the ligand-binding, transmembrane, and linker regions of the NarX sensor kinase to the signaling and adaptation domains of the Tar chemoreceptor elicits a repellent response to nitrate and nitrite. As with NarX, nitrate evokes a stronger response than nitrite. Here we show that mutations targeting a highly conserved sequence (the P box) in the periplasmic domain alter chemoreception by Nart and signaling by NarX similarly. In particular, the G51R substitution converts Nart from a repellent receptor into an attractant receptor for nitrate. Our results underscore the conclusion that the fundamental mechanism of transmembrane signaling is conserved between homodimeric sensor kinases and chemoreceptors. They also highlight the plasticity of the coupling between ligand binding and signal output in these systems.

Suppression of Proinflammatory Signal Transduction and Gene Expression by the Dual Nucleic Acid Binding Domains of the Vaccinia Virus E3L Proteins

Langland, Jeffrey O.; Kash, John C.; Carter, Victoria; Thomas, Matthew J.; Katze, Michael G.; Jacobs, Bertram L.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/2006 EN
Relevância na Pesquisa
35.86%
Cells have evolved elaborate mechanisms to counteract the onslaught of viral infections. To activate these defenses, the viral threat must be recognized. Danger signals, or pathogen-associated molecular patterns, that are induced by pathogens include double-stranded RNA (dsRNA), viral single-stranded RNA, glycolipids, and CpG DNA. Understanding the signal transduction pathways activated and host gene expression induced by these danger signals is vital to understanding virus-host interactions. The vaccinia virus E3L protein is involved in blocking the host antiviral response and increasing pathogenesis, functions that map to separate C-terminal dsRNA- and N-terminal Z-DNA-binding domains. Viruses containing mutations in these domains allow modeling of the role of dsRNA and Z-form nucleic acid in the host response to virus infection. Deletions in the Z-DNA- or dsRNA-binding domains led to activation of signal transduction cascades and up-regulation of host gene expression, with many genes involved in the inflammatory response. These data suggest that poxviruses actively inhibit cellular recognition of viral danger signals and the subsequent cellular response to the viral threat.

Modeling response signal and response time data⋆

Ratcliff, Roger
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.97%
The diffusion model (Ratcliff, 1978) and the leaky competing accumulator model (LCA, Usher & McClelland, 2001) were tested against two-choice data collected from the same subjects with the standard response time procedure and the response signal procedure. In the response signal procedure, a stimulus is presented and then, at one of a number of experimenter-determined times, a signal to respond is presented. The models were fit to the data from the two procedures simultaneously under the assumption that responses in the response signal procedure were based on a mixture of decision processes that had already terminated at response boundaries before the signal and decision processes that had not yet terminated. In the latter case, decisions were based on partial information in one variant of each model or on guessing in a second variant. Both variants of the diffusion model fit the data well and both fit better than either variant of the LCA model, although the differences in numerical goodness-of-fit measures were not large enough to allow decisive selection between the models.

Modeling Aging Effects on Two-Choice Tasks: Response Signal and Response Time Data

Ratcliff, Roger
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/2008 EN
Relevância na Pesquisa
46%
In the response signal paradigm, a test stimulus is presented, and then at one of a number of experimenter-determined times, a signal to respond is presented. Response signal, standard response time (RT), and accuracy data were collected from 19 college-age and 19 60- to 75-year-old participants in a numerosity discrimination task. The data were fit with 2 versions of the diffusion model. Response signal data were modeled by assuming a mixture of processes, those that have terminated before the signal and those that have not terminated; in the latter case, decisions are based on either partial information or guessing. The effects of aging on performance in the regular RT task were explained the same way in the models, with a 70- to 100-ms increase in the nondecision component of processing, more conservative decision criteria, and more variability across trials in drift and the nondecision component of processing, but little difference in drift rate (evidence). In the response signal task, the primary reason for a slower rise in the response signal functions for older participants was variability in the nondecision component of processing. Overall, the results were consistent with earlier fits of the diffusion model to the standard RT task for college-age participants and to the data from aging studies using this task in the standard RT procedure.

A Novel Endoplasmic Reticulum Export Signal: PROLINE AT THE +2-POSITION FROM THE SIGNAL PEPTIDE CLEAVAGE SITE*

Tsukumo, Yoshinori; Tsukahara, Satomi; Saito, Sakae; Tsuruo, Takashi; Tomida, Akihiro
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.86%
NUCB1 (nucleobindin 1) is a Golgi-localized soluble protein with a signal peptide and multiple functional domains. We reported recently that NUCB1 is a negative regulator of the unfolded protein response that activates various endoplasmic reticulum (ER)-originating signaling pathways. In that report, we also showed that Golgi localization of NUCB1 was essential to regulate the unfolded protein response. However, the localization mechanism of NUCB1 is still unknown. Here, we report that the proline residue at the +2-position (Pro+2) from the signal peptide cleavage site is the determinant of NUCB1 protein export from the ER and subsequent transport to the Golgi. Fusion of the N-terminal amino acids 1–35 peptide region, including both signal peptide (amino acids 1–26) and Pro+2, was sufficient for enhanced green fluorescent protein to localize in the Golgi, whereas single amino acid mutation of Pro+2 resulted in defective export from the ER without affecting the protein maturation process. Furthermore, we demonstrated that Pro+2 was important for the enhanced green fluorescent protein fusion protein to concentrate at a transport vesicle formation site within the ER, often termed the ER exit site. Interestingly, such a Pro+2 has also been functionally conserved in other Golgi-localized soluble proteins...

Neural Networks Associated with the Speed-Accuracy Tradeoff: Evidence from the Response Signal Method

Blumen, Helena M.; Gazes, Yunglin; Habeck, Christian; Kumar, Arjun; Steffener, Jason; Rakitin, Brian C.; Stern, Yaakov
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.71%
This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covarying neural activity) associated with the speed-accuracy tradeoff (SAT) in younger adults. The response signal method was used to systematically increase probe duration (125, 250, 500, 1,000 2,000 ms) in a nonverbal delayed-item recognition task. A covariance-based multivariate approach identified three networks that varied with probe duration – indicating that the SAT is driven by three distributed neural networks.

A Digital Signal Processing Approach for Affective Sensing of a Computer User through Pupil Diameter Monitoring

Gao, Ying
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
35.86%
Recent research has indicated that the pupil diameter (PD) in humans varies with their affective states. However, this signal has not been fully investigated for affective sensing purposes in human-computer interaction systems. This may be due to the dominant separate effect of the pupillary light reflex (PLR), which shrinks the pupil when light intensity increases. In this dissertation, an adaptive interference canceller (AIC) system using the H∞ time-varying (HITV) adaptive algorithm was developed to minimize the impact of the PLR on the measured pupil diameter signal. The modified pupil diameter (MPD) signal, obtained from the AIC was expected to reflect primarily the pupillary affective responses (PAR) of the subject. Additional manipulations of the AIC output resulted in a processed MPD (PMPD) signal, from which a classification feature, PMPDmean, was extracted. This feature was used to train and test a support vector machine (SVM), for the identification of stress states in the subject from whom the pupil diameter signal was recorded, achieving an accuracy rate of 77.78%. The advantages of affective recognition through the PD signal were verified by comparatively investigating the classification of stress and relaxation states through features derived from the simultaneously recorded galvanic skin response (GSR) and blood volume pulse (BVP) signals...

Serotonergic modulation and its influence on signal processing at cellular level in deep cerebellar nuclei neurons; Serotonergic modulation and its influence on signal processing at cellular level in deep cerebellar nuclei neurons; Serotonerge Modulation und ihr Einfluss auf die Signalverarbeitung auf zellulärer Ebene in Neuronen der tiefen Kleinhirnkerne

Lee, Meng-Larn
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
35.91%
Deep cerebellar nuclei (DCN) neurons generate the final output of cerebellum and receive abundant modulatory serotonergic inputs from brainstem neurons. The aim of this present study was to elucidate the influence of serotonin on signal processing performed by DCN neurons. Since signal processing is determined by the interplay between intrinsic and synaptic properties, the impact of serotonin on intrinsic as well as synaptic properties was investigated. To this end whole-cell patch clamp recordings were performed in rat cerebellar slices. Serotonin caused a persistent membrane depolarization at current clamp recordings, which was mediated by an increase of tonic cationic currents and a concomitant decrease of tonic potassium currents. At the same time, serotonin influenced the waveform of action potentials that showed a reduced depolarization slope and peak amplitude, both indicating a reduced availability of voltage-gated sodium channels. However, serotonin showed a complicated effect at dynamic clamp recordings where the neuronal response depended on the average activity level before drug application. Spike rate was reduced by serotonin for depolarized high activity states and unaltered or slightly increased for hyperpolarized low activity states. The spike timing precision was not altered...

Generalized likelihood ratio detection for fMRI using complex data

Nan, F.Y.; Nowak, Robert David; Nan, F.Y.; Nowak, Robert David
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
45.77%
Journal Paper; The majority of fMRI studies obtain functional information using statistical tests based on the magnitude image reconstructions. Recently, a complex correlation (CC) test was proposed based on teh complex image data in order to take advantage of phase information in teh signal. However, the CC test ignores additional phase information in the baseline component of the data. In this paper, a new detector for fMRI based on a Generalized Likelihood Ration Test (GLRT) is proposed. The GLRT exploits the fact that the fMRI response signal as well as the baseline component of the data share a common phase. Theoretical analysis and Monte Carlo simulation are used to explore the performance of the new detector. At relatively low signal intensities, the GLRT outperforms both the standard magnitude data test and the CC test. At high signal intensities, the GLRT performs as well as teh standard magnitude data test and significantly better than the CC test.

Effect of nonidentical signal phases on signal amplification of two coupled excitable neurons

Liang, Xiaoming; Liang, Zhao
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.95%
In this paper, we study the response of two coupled excitable neurons to external subthreshold periodic signals. We find that the neurons' response to the subthreshold signals can be enhanced when the signal phases are nonidentical. Moreover, we find that the response can be strongly improved if the level of nonidentical signal phases is at an intermediate value and thus resulting in a resonance-like phenomenon. Furthermore, under the influence of nonidentical signal phases, the response also exhibits a resonance-like dependency on the coupling coefficient. Moreover, we give an analysis to understand the mechanism of these two types of resonance behaviors. Finally, we discuss the robustness of the resonances induced by nonidentical signal phases to neuronal diversity, noise perturbation and different neuron model. We believe that the phenomena found in this paper will be useful for understanding neural information processing.; NNSF of China (Grants 11305078, 11175150 and 11105025); Research Fund of Jiangsu Normal University (Grant 12XLR028); CNPq of Brazil (Grants 306227/2011-8 and 560031/2010-6); FAPESP of Brazil (Grant 2011/50151-0); Selected papers from the XII Brazilian Symposium on Neural Networks (SBRN 2012). Curitiba, Brazil. 20-25 october 2012.

A Model for How Signal Duration Can Determine Distinct Outcomes of Gene Transcription Programs

Fowler, Kevin D.; Chakraborty, Arup K.; Kuchroo, Vijay Kumar
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
35.95%
The reason why IL-6 induces a pro-inflammatory response, while IL-10 induces an anti-inflammatory response, despite both cytokines activating the same transcription factor, STAT3, is not well understood. It is known that IL-6 induces a transient STAT3 signal and that IL-10 induces a sustained STAT3 signal due to the STAT3-induced inhibitor SOCS3's ability to bind to the IL-6R and not the IL-10R. We sought to develop a general transcriptional network that is capable of translating sustained signals into one response, while translating transient signals into a second response. The general structure of such a network is that the transcription factor STAT3 can induce both an inflammatory response and an anti-inflammatory response by inducing two different genes. The anti-inflammatory gene can bind to and inhibit the inflammatory gene's production and the inflammatory gene can bind to its own promoter and induce its own transcription in the absence of the signal. One prediction that can be made from such a network is that in SOCS3−/− mice, where IL-6 induces a sustained STAT3 signal, that IL-6 would act as an anti-inflammatory cytokine, which has indeed been observed experimentally in the literature.

Improving Indwelling Glucose Sensor Performance: Porous, Dexamethasone-Releasing Coatings that Modulate the Foreign Body Response

Vallejo-Heligon, Suzana Gabriela
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2015
Relevância na Pesquisa
35.9%

Inflammation and the formation of an avascular fibrous capsule have been identified as the key factors controlling the wound healing associated failure of implantable glucose sensors. Our aim is to guide advantageous tissue remodeling around implanted sensor leads by the temporal release of dexamethasone (Dex), a potent anti-inflammatory agent, in combination with the presentation of a stable textured surface.

First, Dex-releasing polyurethane porous coatings of controlled pore size and thickness were fabricated using salt-leaching/gas-foaming technique. Porosity, pore size, thickness, drug release kinetics, drug loading amount, and drug bioactivity were evaluated. In vitro sensor functionality test were performed to determine if Dex-releasing porous coatings interfered with sensor performance (increased signal attenuation and/or response times) compared to bare sensors. Drug release from coatings monitored over two weeks presented an initial fast release followed by a slower release. Total release from coatings was highly dependent on initial drug loading amount. Functional in vitro testing of glucose sensors deployed with porous coatings against glucose standards demonstrated that highly porous coatings minimally affected signal strength and response rate. Bioactivity of the released drug was determined by monitoring Dex-mediated...

Error Performance of a Channel of Known Impulse Response

Teal, Paul D; Williamson, Robert; Kennedy, Rodney
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
45.81%
It has long been known that the performance of a channel with intersymbol interference (ISI) not only depends on the signal to noise ratio, but on the actual impulse response coefficients as well. In this paper, a technique for approximating the performance of a communications channel in the presence of ISI is presented. It is assumed that the finite length impulse response of the channel is known, and that a maximum likelihood sequence estimation (MLSE) technique is used for equalisation. The technique consists of identifying for the modulation and impulse response duration, those few error events which are most likely to occur. This selection process is computationally intensive, but once it has been performed for a given modulation, the results can be used to enable very efficient approximation. Results are presented for some common modulation schemes.

Contrast response of temporally sparse dichoptic multifocal visual evoked potentials

Maddess, Ted; James, Andrew; Bowman, Elizabeth
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.91%
Temporally sparse stimuli have been found to produce larger multifocal visual evoked potentials than rapid contrast-reversal stimuli. We compared the contrast-response functions of conventional contrast-reversing (CR) stimuli and three grades of temporally sparse stimuli, examining both the changes in response amplitude and signal-to-noise ratio (SNR). All stimuli were presented dichoptically to normal adult human subjects. One stimulus variant, the slowest pattern pulse, had interleaved monocular and binocular stimuli. Response amplitudes and SNRs were similar for all stimuli at contrast 0.4 but grew faster with increasing contrast for the sparser stimuli. The best sparse stimulus provided an SNR improvement that corresponded to a recording time improvement of 2,6 times relative to that required for contrast reversing stimuli. Multiple regression of log-transformed response metrics characterized the contrast-response functions by fitting power-law relationships. The exponents for the two sparsest stimuli were significantly larger (P < 0.001) than for the CR stimuli, as were the mean response amplitudes and signal-to-noise ratios for these stimuli. The contrast-dependent response enhancement is discussed with respect to the possible influences of rapid retinal contrast gain control...

Absence of lipopolysaccharide high-dose paralysis in B-cell responses: Implications for the one-signal theory

Mamchak, A; Hodgkin, Phillip D
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.88%
Over 20 years ago, Coutinho and Moller reported that high concentrations of LPS were paralytic for the development of antibody secreting cells (ASC). This data was used to explain bell-shaped dose-response curves observed for antihapten antibody formation in response to haptenated LPS. In turn, this bell curve was used to formulate the one-signal model of B cell activation, which argued that antigen signalling was generally unimportant to B cell responses. The present paper re-examines LPS dose-response curves and finds results that do not support the view that high doses of LPS inhibit B cell differentiation to ASC. If high-dose paralysis is not an attribute of LPS stimulation, then the bell-shaped dose curve for hapten-specific ASC originally observed by Coutinho and Moller required an alternative explanation. Through the use of haptenated Ficoll, it was possible to show that the generation of LPS-induced antitrinitrophenol ASC could be inhibited by antigen presented on an inert substrate. Thus, the transmission of surface Ig-mediated (antigen) signals at higher concentrations can explain the antihapten bell-shaped dose curves, in contradiction to the conclusions of the one-signal model.

Effects of Signal Duration on Response Acquisition with Delayed Reinforcement under Temporally Defined Schedules of Reinforcement

Pulido Rull,Marco Antonio; Rubí Gonzalez,Mariana; Backer Hoekstra,Cornelie
Fonte: Sociedad Mexicana de Análisis de la Conducta Publicador: Sociedad Mexicana de Análisis de la Conducta
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
Relevância na Pesquisa
35.86%
This study assessed the effects of signal duration and t d duration on response acquisition of lever-pressing by rats. Thirty naïve male Wistar rats were exposed to one of ten different 32-s temporally defined schedules of delayed, signaled reinforcement. Reinforcement cycles were divided into two temporal time windows, t d and t delta; responses emitted during t d produced reinforcement at the end of the cycle; responses emitted during t delta had no programmed consequences. t d was located at the beginning of the reinforcement cycle and was fixed at one of two different values (4-s or 8-s). The first response emitted during td produced an audible tone of different duration; tone duration was varied across groups Results showed variability, however evidence of response acquisition was more apparent with the long t d duration and with the longer signals. This effect could probably be attributed to the interaction of Pavlovian, and mnemic variables with stimulus discrimination processes.