151 research outputs found
Emergence of Synchronous Oscillations in Neural Networks Excited by Noise
The presence of noise in non linear dynamical systems can play a constructive
role, increasing the degree of order and coherence or evoking improvements in
the performance of the system. An example of this positive influence in a
biological system is the impulse transmission in neurons and the
synchronization of a neural network. Integrating numerically the Fokker-Planck
equation we show a self-induced synchronized oscillation. Such an oscillatory
state appears in a neural network coupled with a feedback term, when this
system is excited by noise and the noise strength is within a certain range.Comment: 12 pages, 18 figure
Viewing 3D TV over two months produces no discernible effects on balance, coordination or eyesight
With the rise in stereoscopic 3D media, there has been concern that viewing stereoscopic 3D (S3D) content could have long-term adverse effects, but little data are available. In the first study to address this, 28 households who did not currently own a 3D TV were given a new TV set, either S3D or 2D. The 116 members of these households all underwent tests of balance, coordination and eyesight, both before they received their new TV set, and after they had owned it for 2 months. We did not detect any changes which appeared to be associated with viewing 3D TV. We conclude that viewing 3D TV does not produce detectable effects on balance, coordination or eyesight over the timescale studied.
Practitioner Summary: Concern has been expressed over possible long-term effects of stereoscopic 3D (S3D). We looked for any changes in vision, balance and coordination associated with normal home S3D TV viewing in the 2 months after first acquiring a 3D TV. We find no evidence of any changes over this timescale
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Analysis of spontaneous activity patterns in developing retina: algorithms and results
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Cooperative Dynamics of an Artificial Stochastic Resonant System
We have investigated cooperative dynamics of an artificial stochastic
resonant system, which is a recurrent ring connection of neuron-like signal
transducers (NST) based on stochastic resonance (SR), using electronic circuit
experiments. The ring showed quasi-periodic, tunable oscillation driven by only
noise. An oscillation coherently amplified by noise demonstrated that SR may
lead to unusual oscillation features. Furthermore, we found that the ring
showed synchronized oscillation in a chain network composed of multiple rings.
Our results suggest that basic functions (oscillation and synchronization) that
may be used in the central pattern generator of biological system are induced
by collective integration of the NST element.Comment: 13 pages, 4 figure
GABAB receptor-mediated, layer-specific synaptic plasticity reorganizes gamma-frequency neocortical response to stimulation
Repeated presentations of sensory stimuli generate transient gamma-frequency (30-80 Hz) responses in neocortex that show plasticity in a task-dependent manner. Complex relationships between individual neuronal outputs and the mean, local field potential (population activity) accompany these changes, but little is known about the underlying mechanisms responsible. Here we show that transient stimulation of input layer 4 sufficient to generate gamma oscillations induced two different, lamina-specific plastic processes that correlated with lamina-specific changes in responses to further, repeated stimulation: Unit rates and recruitment showed overall enhancement in supragranular layers and suppression in infragranular layers associated with excitatory or inhibitory synaptic potentiation onto principal cells, respectively. Both synaptic processes were critically dependent on activation of GABAB receptors and, together, appeared to temporally segregate the cortical representation. These data suggest that adaptation to repetitive sensory input dramatically alters the spatiotemporal properties of the neocortical response in a manner that may both refine and minimize cortical output simultaneously
Balance and coordination after viewing stereoscopic 3D television.
Manufacturers and the media have raised the possibility that viewing stereoscopic 3D television (S3D TV) may cause temporary disruption to balance and visuomotor coordination. We looked for evidence of such effects in a laboratory-based study. Four hundred and thirty-three people aged 4-82 years old carried out tests of balance and coordination before and after viewing an 80 min movie in either conventional 2D or stereoscopic 3D, while wearing two triaxial accelerometers. Accelerometry produced little evidence of any change in body motion associated with S3D TV. We found no evidence that viewing the movie in S3D causes a detectable impairment in balance or in visuomotor coordination
La precariedad en nuestras vidas: pensando el trabajo social desde sus condiciones de trabajo
Este artículo centra su análisis en el estudio realizado por Consejo Profesional de la CABA en torno a condiciones de trabajo, realizando una encuesta de muestra representativa de matriculadas/os activas/os. En el actual escenario, se sostiene un mercado de trabajo precarizado, así como políticas públicas que amplían sus niveles de fragmentación y sectorialidad, con características francamente empobrecidas. Para el Trabajo Social, esto redunda en un mismo conflicto: contextos y medios de trabajo (políticas sociales) precarios, en condiciones laborales del mismo tipo. De aquí que se explican las apelaciones constantes del colectivo en los diversos reclamos, de políticas públicas dotadas de mayor calidad e integralidad con presupuesto acorde a las necesidades.
El presente artículo tiene por objeto rediscutir la categoría de precarización laboral, superando su conceptualización como exclusiva expresión de deficientes modalidades de contratación, e incorporando la dimensión de precarización de nuestras vidas, para pensar los actuales contextos de trabajo en los que nos desenvolvemos profesionalmente. La intención de desentrañar algunas de estas líneas de análisis, se relaciona con la posibilidad de comprender y potenciar la organización de nuestra disciplina, en tanto “clase que vive del trabajo” (Antunes; 2001).Eje 2: Debates sobre el trabajo social y las ciencias sociales: su implicancia en el contexto actual.Facultad de Trabajo Socia
Trapping Dynamics with Gated Traps: Stochastic Resonance-Like Phenomenon
We present a simple one-dimensional trapping model prompted by the problem of
ion current across biological membranes. The trap is modeled mimicking the
ionic channel membrane behaviour. Such voltage-sensitive channels are open or
closed depending on the value taken by a potential. Here we have assumed that
the external potential has two contributions: a determinist periodic and a
stochastic one. Our model shows a resonant-like maximum when we plot the
amplitude of the oscillations in the absorption current vs. noise intensity.
The model was solved both numerically and using an analytic approximation and
was found to be in good accord with numerical simulations.Comment: RevTex, 5 pgs, 3 figure
On the Influence of Noise on the Critical and Oscillatory Behavior of a Predator-Prey Model: Coherent Stochastic Resonance at the Proper Frequency
Noise induced changes in the critical and oscillatory behavior of a
Prey-Predator system are studied using power spectrum density and Spectral
Amplification Factor (SAF) analysis. In the absence of external noise, the
population densities exhibit three kinds of asymptotic behavior, namely:
Absorbing State, Fixed Point (FP) and an Oscillatory Regime (OR) with a well
defined proper (natural) frequency. The addition of noise destabilizes the FP
phase inducing a transition to a new OR. Surprisingly, it is found that when a
periodic signal is added to the control parameter, the system responds
robustly, without relevant changes in its behavior. Nevertheless, the "Coherent
Stochastic Resonance" phenomenon is found only at the proper frequency. Also, a
method based on SAF allows us to locate very accurately the transition points
between the different regimes.Comment: RevTex, 18 pgs, 6 figures. Submitted to Physics Letters A (2000
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