Information transmission and recovery in neural communications channels

Fil:Eguia, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Spike timing and synaptic plasticity in the premotor pathway of birdsong

The neural circuits of birdsong appear to utilize specific time delays in their operation. In particular, the anterior forebrain pathway (AFP) is implicated in an approximately 40- to 50- ms time delay, ΔT, playing a role in the relative timing of premotor signals from the nucleus HVc to the nucleus robust nucleus of the archistratium (RA) and control/learning signals from the nucleus lateral magnocellular nucleus of the anterior neostratium (lMAN) to RA. Using a biophysical model of synaptic plasticity based on experiments on mammalian hippocampal and neocortical pyramidal neurons, we propose an understanding of this ≈ 40- to 50- ms delay. The biophysical model describes the influence of Ca2+ influx into the postsynaptic RA cells through NMDA and AMPA receptors and the induction of LTP and LTD through complex metabolic pathways. The delay, ΔT, between HVc → RA premotor signals and lMAN → RA control/learning signals plays an essential role in determining if synaptic plasticity is induced by signaling from each pathway into RA. If ΔT is substantially larger than 40 ms, no plasticity is induced. If ΔT is much less than 40 ms, only potentiation is expected. If ΔT≈ 40 ms, the sign of synaptic plasticity is sensitive to ΔT. Our results suggest that changes in ΔT may influence learning and maintenance of birdsong. We investigate the robustness of this result to noise and to the removal of the Ca2+ contribution from lMAN → RA NMDA receptors. © Springer-Verlag 2004.Fil: Abarbanel, Henry D. I.. University of California at San Diego; Estados UnidosFil: Gibb, Leif. University of California at San Diego; Estados UnidosFil: Mindlin, Bernardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Rabinovich, M.I.. University of California at San Diego; Estados UnidosFil: Talathi, Sachin. University of California at San Diego; Estados Unido

Validity of physical activity monitors during daily life in patients with COPD.

Symptoms during physical activity (PA) and physical inactivity are COPD. Our aim was to evaluate the validity and usability of six activity in patients with COPD against the doubly labelled water (DLW) indirect calorimetry method.Eighty COPD patients (age 68+/-6 years, FEV1 57+/-19% predicted) recruited in four centres each wore simultaneously three or six commercially available monitors validated in chronic conditions for consecutive days. A priori validity criteria were defined. These ability to explain total energy expenditure (TEE) variance through regression analysis, using TEE as the dependent variable with total body (TBW) plus several PA monitors outputs as independent variables; and with DLW measured activity energy expenditure (AEE).The Actigraph GT3X DynaPort MoveMonitor best explained the majority of the TEE variance not explained by TBW (53% and 70% respectively) and showed the most correlations with AEE (r=0.71 p<0.001, r=0.70 p<0.0001, of this study should guide users in choosing valid activity monitors for or for clinical use in patients with chronic diseases such as COPD

Heteroclinic Ratchets in a System of Four Coupled Oscillators

We study an unusual but robust phenomenon that appears in an example system of four coupled phase oscillators. We show that the system can have a robust attractor that responds to a specific detuning between certain pairs of the oscillators by a breaking of phase locking for arbitrary positive detunings but not for negative detunings. As the dynamical mechanism behind this is a particular type of heteroclinic network, we call this a 'heteroclinic ratchet' because of its dynamical resemblance to a mechanical ratchet

Frozen spatial chaos induced by boundaries

We show that rather simple but non-trivial boundary conditions could induce the appearance of spatial chaos (that is stationary, stable, but spatially disordered configurations) in extended dynamical systems with very simple dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion equation in a two-dimensional undulated domain. Concepts from the theory of dynamical systems, and a transverse-single-mode approximation are used to describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit http://www.imedea.uib.es/~victo

Voluntary sport and highway risks in adolescents and youths (following current French and Canadian periodical publications of 2000th)

In this article we discuss some personal traits of adolescents and young people, disposed to different types of risky behavior. We describe correlations between different types of risky behavior in one individual. We discuss also the gender aspect of risk taking in adolescents and youth. Some modern theories of risk taking are recapitulated. Finally, we discuss the organizational question about the preventive work with adolescents and youth, aimed on minimization of sportive and highway risk

Information transmission and recovery in neural communications channels

Fil:Eguia, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Dynamics of two electrically coupled chaotic neurons: experimental observations and model analysis

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