Acetylcholine modifies neuronal acoustic rate-level functions in guinea pig auditory cortex by an action at muscarinic receptors

ABSTRACT Cholinergic modification of neuronal responsiveness in auditory cortex includes alteration of spontaneous and tone-evoked neuronal discharge. Previously it was suggested that the effects of acetylcholine (ACh) and muscarinic agonists on neuronal discharge resembled those due to increases in the intensity of acoustic stimuli Acet lcholine (ACh) modifies spontaneous and Often the effects of ACh result in systematic modification of the receptive field of the neuron (for recent reviews, see Ashe and Weinberger, 1990; Weinberger et evoke B discharge of neurons in sensory koniocortex. consist of a change in of responses to different frequencies of acoustic stimuli bethods of recordin single unit dischar e, acoustic logical agents used were similar to those previously reporte

Modification of Unit Discharges in the Medial Geniculate Nucleus by Click-Shock Pairing

The present experiment was concerned with some discharge properties of single neurons in the medial geniculate body of the locally anesthetized paralyzed cat. The effect of pairing clicks with paw shock upon discharge rate and pattern was of particular concern. Twelve neurons obtained from 11 cats were studied exhaustively for periods up to 4 hr. Under control conditions, rate stationarity for both spontaneous and click-evoked activity was found in only 3/12 of the units. Click-shock pairing produced rate changes in lo/12 of the cells; an increase in rate predominated. The pattern of discharges was altered in 9/E of the cells as a consequence of click-shock pairing. Specifically, the initial short-latency discharge was modified; there was a reduction in the proportion of spikes in the first peak to the total number of spikes in the poststimulus time histogram. This reduction was not merely a consequence of increases in over-all rate of discharge. In the case of one cell which was inhibited rather than excited by click stimulation, the click-shock pairing resulted in a reduction in the duration of inhibition. Control findings indicated that the pattern modifications were not due to a change in stimulus intensity, the unconditioned effects of the shock itself, or to an increase in arousal level

Using learning environments as a metaphor for educational change

Purpose – The purpose of this paper is to show that the online learning environment can be seen as the means by which higher education can explore the challenges and opportunities raised by online and digital society. Design/methodology/approach – The paper argues that the online learning environment can be seen as a metaphor for how universities respond to the requirements and challenges of the digital age. Current learning management systems (LMSs) are examined, and compared with the values found in web 2.0 and social media. Current thinking on pedagogy for online learning is then examined. The SocialLearn project at the Open University in the UK is then explained, which seeks to create a disaggregated, decentralised, social system for learners. Findings – The conclusion from the analysis is that there is a conflict between the centralised learning management system (LMS) and the requirements of online pedagogy. The traditional LMS can be seen as embodying the wrong metaphor, that of the traditional classroom. The paper concludes by arguing that such learning environments will be more useful to higher education in coming to understand its response to many of the changes being seen in society, which are facilitated by the new technologies. Originality/value – The paper provides a framework for considering LMSs and their relation to universities and pedagogy, and an argument for the promotion of more decentralised systems

Association learning-dependent increases in acetylcholine release in the rat auditory cortex during auditory classical conditioning

a b s t r a c t The cholinergic system has been implicated in sensory cortical plasticity, learning and memory. This experiment determined the relationship between the acquisition of a Pavlovian conditioned approach response (CR) to an auditory conditioned stimulus (CS) and the release of acetylcholine (ACh) in the primary auditory cortex in rats. Samples of ACh were collected via microdialysis during behavioral training in either an auditory classical conditioning task or in a non-associative control task. The conditioning group received daily pairings of a white noise CS with a sucrose pellet unconditioned stimulus (US), while the control group received an equal number of CS and US presentations, but with these stimuli being presented randomly. Training was conducted on three consecutive days, with microdialysis samples being collected on Days 1 and 3 in separate sub-groups. The level of ACh released in the auditory cortex during conditioning trials increased from the first to the third day of training in the conditioning group as rats acquired the CR, but did not change in the control group, which did not acquire a CR. These data provide direct evidence for the hypothesis that ACh release increases in the primary auditory cortex during natural memory formation, where cholinergic activation is known to contribute to the formation of specific associative representational plasticity in conjunction with specific memory formation

A search for steep spectrum radio relics and halos with the GMRT

Context: Diffuse radio emission, in the form of radio halos and relics, traces regions in clusters with shocks or turbulence, probably produced by cluster mergers. Some models of diffuse radio emission in clusters indicate that virtually all clusters should contain diffuse radio sources with a steep spectrum. External accretion shocks associated with filamentary structures of galaxies could also accelerate electrons to relativistic energies and hence produce diffuse synchrotron emitting regions. Here we report on Giant Metrewave Radio Telescope (GMRT) observations of a sample of steep spectrum sources from the 74 MHz VLSS survey. These sources are diffuse and not associated with nearby galaxies. Aims: The main aim of the observations is to search for diffuse radio emission associated with galaxy clusters or the cosmic web. Methods: We carried out GMRT 610 MHz continuum observations of unidentified diffuse steep spectrum sources. Results: We have constructed a sample of diffuse steep spectrum sources, selected from the 74 MHz VLSS survey. We identified eight diffuse radio sources probably all located in clusters. We found five radio relics, one cluster with a giant radio halo and a radio relic, and one radio mini-halo. By complementing our observations with measurements from the literature we find correlations between the physical size of relics and the spectral index, in the sense that smaller relics have steeper spectra. Furthermore, larger relics are mostly located in the outskirts of clusters while smaller relics are located closer to the cluster center.Comment: 20 pages, 26 figures, accepted for publication in A&A on October 7, 200

Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1 integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let

Search for the standard model Higgs boson decaying to a bb pair in events with one charged lepton and large missing transverse energy using the full CDF data set

We present a search for the standard model Higgs boson produced in association with a W boson in sqrt(s) = 1.96 TeV p-pbar collision data collected with the CDF II detector at the Tevatron corresponding to an integrated luminosity of 9.45 fb-1. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a neutrino, we set 95% credibility level upper limits on the WH production cross section times the H->bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125 GeV/c2 we observe (expect) a limit of 4.9 (2.8) times the standard model value.Comment: Submitted to Phys. Rev. Lett (v2 contains clarifications suggested by PRL

Search for the standard model Higgs boson decaying to a bbˉb\bar{b} pair in events with no charged leptons and large missing transverse energy using the full CDF data set

We report on a search for the standard model Higgs boson produced in association with a vector boson in the full data set of proton-antiproton collisions at $\sqrt{s} = 1.96$ TeV recorded by the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45 fb$^{-1}$. We consider events having no identified charged lepton, a transverse energy imbalance, and two or three jets, of which at least one is consistent with originating from the decay of a $b$ quark. We place 95% credibility level upper limits on the production cross section times standard model branching fraction for several mass hypotheses between 90 and $150 \mathrm{GeV}/c^2$. For a Higgs boson mass of $125 \mathrm{GeV}/c^2$, the observed (expected) limit is 6.7 (3.6) times the standard model prediction.Comment: Accepted by Phys. Rev. Let

Search for Pair Production of Scalar Top Quarks Decaying to a tau Lepton and a b Quark in ppbar Collisions at sqrt{s}=1.96 TeV

We search for pair production of supersymmetric top quarks (~t_1), followed by R-parity violating decay ~t_1 -> tau b with a branching ratio beta, using 322 pb^-1 of ppbar collisions at sqrt{s}=1.96 TeV collected by the CDF II detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section sigma(~t_1 ~tbar_1)*beta^2 as a function of the stop mass m(~t_1). Assuming beta=1, we set a 95% confidence level limit m(~t_1)>153 GeV/c^2. The limits are also applicable to the case of a third generation scalar leptoquark (LQ_3) decaying LQ_3 -> tau b.Comment: 7 pages, 2 eps figure