Reynaldo D Pinto | Universidade de São Paulo (original) (raw)

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Papers by Reynaldo D Pinto

Central pattern generators (CPGs) controlling motor function are among the best-understood exampl... more Central pattern generators (CPGs) controlling motor function are among the best-understood examples of oscillatory networks found in virtually every nervous system. The pyloric CPG of the crustacean stomatogastric nervous system has long been a remarkable model of such oscillatory networks and is one of the best described and understood neural circuits presently available. The biophysical and neuromodulatory factors shaping the

Neuroscience, 2004

Spectrally broadband stimulation of neurons has been an effective method for studying their dynam... more Spectrally broadband stimulation of neurons has been an effective method for studying their dynamic responses to simulated synaptic inputs. Previous studies with such stimulation were mostly based upon the direct intracellular injection of noisy current waveforms. In the present study we analyze and compare the firing output of various identified molluscan neurons to aperiodic, broadband current signals using three types of stimulus paradigms: 1. direct injection in current clamp mode, 2. conductance injection using electrotonic coupling of the input waveform to the neuron, and 3. conductance injection using a simulated chemical excitatory connection. The current waveforms were presented in 15 successive trials and the trial-to-trial variations of the spike responses were analyzed using peri-stimulus spike density functions. Comparing the responses of the neurons to the same type of input waveforms, we found that conductance injection resulted in more reliable and precise spike resp...

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1996

We studied the drop formation in a dripping faucet at room temperature by the direct observation ... more We studied the drop formation in a dripping faucet at room temperature by the direct observation of the drop growing which was recorded with a VHS camera, from a drop rate of f=0.24 drop/s up to f~=10 drops/s, approximately, simultaneously with the measurement of the interdrops time intervals. It is shown that the appearance of satellites drops the number of

BMC Neuroscience, 2011

We developed a method based on Information Theory [1] to the analysis of discrete time series app... more We developed a method based on Information Theory [1] to the analysis of discrete time series applied to spike and pulse sequences in two different systems: Central Pattern Generator (CPG) motor neurons in the crustacean stomatogastric ganglion (biological and model neurons) and electrocommunication in weakly electric fish interacting with an artificial fish. CPG motor neurons [4][5] in the nervous systems

Physical Review E, 2000

A sequence of attractors, reconstructed from interdrops time series data of a leaky faucet experi... more A sequence of attractors, reconstructed from interdrops time series data of a leaky faucet experiment, is analyzed as a function of the mean dripping rate. We established the presence of a saddle point and its manifolds in the attractors and we explained the dynamical changes in the system using the evolution of the manifolds of the saddle point, as suggested by the orbits traced in first return maps. The sequence starts at a fixed point and evolves to an invariant torus of increasing diameter (a Hopf bifurcation) that pushes the unstable manifold towards the stable one. The torus breaks up and the system shows a chaotic attractor bounded by the unstable manifold of the saddle. With the attractor expansion the unstable manifold becomes tangential to the stable one, giving rise to the sudden disappearance of the chaotic attractor, which is an experimental observation of a so called chaotic blue sky catastrophe.

Physical Review E, 1994

Two types of sudden changes in chaotic attractors were observed in a leaky-faucet experiment. One... more Two types of sudden changes in chaotic attractors were observed in a leaky-faucet experiment. One of them is consistent with a boundary crisis interpretation. Intermittent behaviors of two kinds were also observed. One type is related to a tangent bifurcation with odd periodic attractors and bursts of chaos, and the other type takes place between two even periodic attractors.

Physical Review E, 1995

ABSTRACT In a leaky faucet experiment an inverse Hopf bifurcation was observed, as one increases ... more ABSTRACT In a leaky faucet experiment an inverse Hopf bifurcation was observed, as one increases the water flux, before the occurrence of the continuous flow. For values of the drop rate smaller than the critical drop rate, the movement is periodic or quasiperiodic with a finite amplitude of the time series. At the critical point the amplitude of the time series vanishes and it suggests the bifurcation point as the threshold of the continuous flow. (c) 1995 The American Physical Society

Physical Review E, 1998

The existence of a spiraling saddle point and its manifolds in attractors of a leaky faucet exper... more The existence of a spiraling saddle point and its manifolds in attractors of a leaky faucet experiment is topologically shown. Two interior crises concerning a subtle expansion of the attractor that collides with a stable manifold of this saddle point are reported.

We report on experimental studies of synchronization phenomena in a pair of analog electronic neu... more We report on experimental studies of synchronization phenomena in a pair of analog electronic neurons (ENs). The ENs were designed to reproduce the observed membrane voltage oscillations of isolated biological neurons from the stomatogastric ganglion of the California spiny lobster Panulirus interruptus. The ENs are simple analog circuits which integrate four-dimensional differential equations representing fast and slow subcellular mechanisms that produce the characteristic regular/chaotic spiking-bursting behavior of these cells. In this paper we study their dynamical behavior as we couple them in the same configurations as we have done for their counterpart biological neurons. The interconnections we use for these neural oscillators are both direct electrical connections and excitatory and inhibitory chemical connections: each realized by analog circuitry and suggested by biological examples. We provide here quantitative evidence that the ENs and the biological neurons behave similarly when coupled in the same manner. They each display well defined bifurcations in their mutual synchronization and regularization. We report briefly on an experiment on coupled biological neurons and four-dimensional ENs, which provides further ground for testing the validity of our numerical and electronic models of individual neural behavior. Our experiments as a whole present interesting new examples of regularization and synchronization in coupled nonlinear oscillators.