795 research outputs found
Tonic And Phasic Inhibitory Mechanisms Mediating Sensorimotor Decision-Making In The Goldfish Auditory Startle Circuit
This work describes related studies of cellular and synaptic signaling mechanisms involved in the balance of excitation and inhibition in the goldfish auditory startle circuit. The general purpose of these experiments was to identify novel mechanisms that contribute to action selection at different stages of the motor control hierarchy. The methods applied to achieve this goal tested the effects of selective antagonists for target receptor systems on sound-evoked excitation and inhibition of startle.
Chapter 2 describes a study of a poorly-understood serotonergic mechanism, the 5-HT5A receptor, that was not previously functionally characterized in native tissues or associated with neural or behavioral processes. Treatment with a selective 5-HT5A antagonist caused a 26.41 ± 3.98% reduction in sound-evoked excitation of startle. Subsequent experiments revealed that the 5-HT5A antagonist significantly reduced post-synaptic excitability in the Mauthner-cell (M-cell) neurons that initiate startle. Despite these effects, prepulse inhibition (PPI) of the startle response remained robustly intact after treatment with the 5-HT5A antagonist. The 5-HT5A receptor is thus not a likely mechanism for PPI, but does act as a selective modulator of startle excitability. A final series of experiments confirmed that the 5-HT5A antagonist reduced M-cell excitability by increasing Cl- conductance, likely by activating Cl- channels.
Chapter 3 presents experiments focused on the inhibitory neurotransmitters that directly mediate the phasic inhibitory process elicited during PPI. Strychnine, a glycine receptor (GlyR) antagonist, caused an 87.43 ± 21.53% increase in sound-evoked excitation of startle, but PPI remained robustly intact, despite this. GlyRs thus likely mediate a tonic inhibitory process that was blocked by strychnine treatment, but glycinergic components of sound-evoked inhibition decayed too rapidly (\u3c50 \u3ems) to contribute to the prolonged time-course of PPI.
In a parallel series of experiments, treatment with bicuculline, the GABAAR antagonist, caused similar increases in sound-evoked excitation (by 133.8 ± 10.3%) of startle, but the GABAAR antagonist also significantly reduced auditory PPI at inter-stimulus intervals of 100 ms and less. In sum, these findings indicate that glycine and GABA tonically inhibit the M-cell startle circuit, but GABA is also the primary effector mechanism for inhibitory signaling during PPI.
In summary, three goals were accomplished. First, the thorough functional characterization of 5-HT5A provides a fully integrated serotonergic mechanism, and this appears to provide an ideal tool for selective potentiation of startle. Next, experiments with strychnine emphasize a short-lived role of GlyRs in sound-evoked (feed-forward) inhibition, and also act as mediators of a tonic inhibitory process that controls startle excitability. Last, experiments with bicuculline identify GABA as the inhibitory neurotransmitter that directly mediates PPI
Heavy flavor diffusion in weakly coupled N=4 Super Yang-Mills theory
We use perturbation theory to compute the diffusion coefficient of a heavy
quark or scalar moving in N=4 SU(N_c) Super Yang-Mills plasma to leading order
in the coupling and the ratio T/M<<1. The result is compared both to recent
strong coupling calculations in the same theory and to the corresponding weak
coupling result in QCD. Finally, we present a compact and simple formulation of
the Lagrangian of our theory, N=4 SYM coupled to a massive fundamental N=2
hypermultiplet, which is well-suited for weak coupling expansions.Comment: 22 pages, 4 figures; v3: error corrected in calculations, figures and
discussion modified accordingl
Mathematical Methods Applied to Digital Image Processing
Introduction: Digital image processing (DIP) is an important research area since it spans a variety of applications. Although over the past few decades there has been a rapid rise in this field, there still remain issues to address. Examples include image coding, image restoration, 3D image processing, feature extraction and analysis, moving object detection, and face recognition. To deal with these issues, the use of sophisticated and robust mathematical algorithms plays a crucial role. The aim of this special issue is to provide an opportunity for researchers to publish their latest theoretical and technological achievements in mathematical methods and their various applications related to DIP. This special issue covers topics related to the development of mathematical methods and their applications. It has a total of twenty-four high-quality papers covering various important topics in DIP, including image preprocessing, image encoding/decoding, stereo image reconstruction, dimensionality and data size reduction, and applications
Glycine and GABAA receptors mediate tonic and phasic inhibitory processes that contribute to prepulse inhibition in the goldfish startle network
Prepulse inhibition (PPI) is understood as a sensorimotor gating process that attenuates sensory flow to the startle pathway during early stages (20--1000 ms) of information processing. Here, we applied in vivo electrophysiology and pharmacology to determine if PPI is mediated by glycine receptors (GlyRs) and/or GABAA receptors (GABAARs) in the goldfish auditory startle circuit. Specifically, we used selective antagonists to dissect the contributions of target receptors on sound-evoked postsynaptic potentials (PSPs) recorded in the neurons that initiate startle, the Mauthner-cells (M-cell). We found that strychnine, a GlyR antagonist, disrupted a fast-activated (5 ms) and rapidly (\u3c50 \u3ems) decaying (feed-forward) inhibitory process that contributes to PPI at 20 ms prepulse/pulse inter-stimulus intervals (ISI). Additionally we observed increases of the evoked postsynaptic potential (PSP) peak amplitude (+87.43 ± 21.53%, N = 9) and duration (+204 ± 48.91%, N = 9). In contrast, treatment with bicuculline, a GABAAR antagonist, caused a general reduction in PPI across all tested interstimulus intervals (ISIs) (20--500 ms). Bicuculline also increased PSP peak amplitude (+133.8 ± 10.3%, N = 5) and PSP duration (+284.95 ± 65.64%, N = 5). Treatment with either antagonist also tonically increased post-synaptic excitability in the M-cells, reflected by an increase in the magnitude of antidromically-evoked action potentials (APs) by 15.07 ± 3.21%, N = 7 and 16.23 ± 7.08%, N = 5 for strychnine and bicuculline, respectively. These results suggest that GABAARs and GlyRs are functionally segregated to short- and longer-lasting sound-evoked (phasic) inhibitory processes that contribute to PPI, with the mediation of tonic inhibition by both receptor systems being critical for gain control within the M-cell startle circuit
Coping with noise in social dilemmas: Group representatives fare worse than individuals because they lack trust in others’ benign intentions
Research on interindividual–intergroup discontinuity has illuminated distinct patterns of cognition,
motivation, and behavior in interindividual versus intergroup contexts. However, it has examined
these processes in laboratory environments with perfect transparency, whereas real-life interactions
are often characterized by noise (i.e., misperceptions and unintended errors). This research compared
interindividual and intergroup interactions in the presence or absence of noise. In a laboratory
experiment, participants played 35 rounds of a dyadic give-some dilemma, in which they acted as
individuals or group representatives. Noise was manipulated, such that players’ intentions either were
perfectly translated into behavior or could deviate from their intentions in certain rounds (resulting in
less cooperative behavior). Noise was more detrimental to cooperation in intergroup contexts than in
interindividual contexts, because (a) participants who formed benign impressions of the other player
coped better with noise, and (b) participants were less likely to form such benign impressions in
intergroup than interindividual interactions
Hard thermal loops and the entropy of supersymmetric Yang-Mills theories
We apply the previously proposed scheme of approximately self-consistent
hard-thermal-loop resummations in the entropy of high-temperature QCD to N=4
supersymmetric Yang-Mills (SYM) theories and compare with a (uniquely
determined) R[4,4] Pad\'e approximant that interpolates accurately between the
known perturbative result and the next-to-leading order strong-coupling result
obtained from AdS/CFT correspondence. We find good agreement up to couplings
where the entropy has dropped to about 85% of the Stefan-Boltzmann value. This
is precisely the regime which in purely gluonic QCD corresponds to temperatures
above 2.5 times the deconfinement temperature and for which this method of
hard-thermal-loop resummation has given similar good agreement with lattice QCD
results. This suggests that in this regime the entropy of both QCD and N=4 SYM
is dominated by effectively weakly coupled hard-thermal-loop quasiparticle
degrees of freedom. In N=4 SYM, strong-coupling contributions to the
thermodynamic potential take over when the entropy drops below 85% of the
Stefan-Boltzmann value.Comment: 14 pages, 2 figures, JHEP3. v2: revised and expanded, with unchanged
HTL results but corrected NLO strong-coupling result from AdS/CFT (which is
incorrectly reproduced in almost all previous papers comparing weak and
strong coupling results of N=4 SYM) and novel (unique) Pade approximant
interpolating between weak and strong coupling result
Non-Vacuum Bianchi Types I and V in f(R) Gravity
In a recent paper \cite{1}, we have studied the vacuum solutions of Bianchi
types I and V spacetimes in the framework of metric f(R) gravity. Here we
extend this work to perfect fluid solutions. For this purpose, we take stiff
matter to find energy density and pressure of the universe. In particular, we
find two exact solutions in each case which correspond to two models of the
universe. The first solution gives a singular model while the second solution
provides a non-singular model. The physical behavior of these models has been
discussed using some physical quantities. Also, the function of the Ricci
scalar is evaluated.Comment: 15 pages, accepted for publication in Gen. Realtiv. Gravi
Plastic recycling stripped naked – from circular product to circular industry with recycling cascade
This perspective combines various expertise to develop and analyse the concept of technology cascade for recycling waste plastics with the goal of displacing as much fossil crude oil as possible. It thereby presents archetype recycling technologies with their strengths and weaknesses. It then combines them in various cascades to process a representative plastic mix, and determines how much (fossil) naphtha could be displaced and at which energy consumption. The cascades rely on a limited number of parameters that are fully reported in supplementary information and that were used in a simple and transparent spreadsheet model. The calculated results bust several common myths in plastic recycling, e. g. by prioritizing here recycled volume over recycling efficiency, and prioritizing circular industry over circular products. It unravels the energy cost of solvent-based recycling processes, shows the key role of gasification and the possibility to displace up to 70 % of the fossil feedstock with recycled carbon, a recycling rate that compares well with that aluminium, steel or paper. It suggests that deeper naphtha displacement would require exorbitant amount of energy. It therefore argues for the need to complement recycling with the use of renewable carbon, e. g. based on biomass, to fully defossilise the plastic industry.</p
Ground-breaking: Scientific and sonic perceptions of environmental change in the African Sahel
Soils surrounding ancient settlements can hold evidence of the activities of past societies. To seek an understanding of how past societies have reacted and contributed to environmental change requires many data sources. The real-time audiovisual installation Ground-breaking problematises the presentation of such data gained through the image-analysis of soil materials. These data are used to connote environmental events and consequent human responses. Combining these data with audiovisual synthesis and environmental recordings, a basis for developing conceptualizations of new locales undergoing environmental change is presented; the visual and sonic narratives developed allowing the art-science interface to be explored
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