Search results for " neurological"
showing 10 items of 166 documents
Experimental study of electrical FitzHugh-Nagumo neurons with modified excitability
2006
International audience; We present an electronical circuit modelling a FitzHugh-Nagumo neuron with a modified excitability. To characterize this basic cell, the bifurcation curves between stability with excitation threshold, bistability and oscillations are investigated. An electrical circuit is then proposed to realize a unidirectional coupling between two cells, mimicking an inter-neuron synaptic coupling. In such a master-slave configuration, we show experimentally how the coupling strength controls the dynamics of the slave neuron, leading to frequency locking, chaotic behavior and synchronization. These phenomena are then studied by phase map analysis. The architecture of a possible ne…
Influence of the scalp thickness on the intracranial contribution to rheoencephalography
2004
In spite of the great efforts made by the scientific community, up to now there is no agreement about the rheoencephalography (REG) capability to reflect cerebral blood flow (CBF). Moreover, a standard procedure and the optimal electrode arrangement have not been established yet. In a previous study, we found, using a classical four-shell spherical model of the head and solving it by numerical methods that, theoretically, there could exist an electrode arrangement to register an REG II free of extracranial contribution. In this paper, we have studied the influence of scalp thickness on the intracranial contribution to REG II. The study has been performed by solving the head model, using in …
Expectation of sensory stimulation modulates brain activation during visual motion stimulation.
2005
The differential effects of visual hemifield motion stimulation during fixation of a stationary target were compared under two conditions: fixation straight ahead without any further instructions and fixation straight ahead with attention shifted to the "dark hemifield." Data from nine right-handed volunteers revealed that striate and extrastriate right hemispheric visual areas exhibited larger activations during left hemifield motion stimulation when attention was shifted to the right dark hemifield. Montreal Neurological Institute (MNI) coordinates (26, -98, -4) of the additional clusters activated in the latter condition corresponded best to the kinetic occipital region, which is known t…
New neuroprotective effect of lemon integropectin on neuronal cellular model
2021
Lemon IntegroPectin obtained via hydrodynamic cavitation of organic lemon processing waste in water shows significant neuroprotective activity in vitro, as first reported in this study investigating the effects of both lemon IntegroPectin and commercial citrus pectin on cell viability, cell morphology, reactive oxygen species (ROS) production, and mitochondria perturbation induced by treatment of neuronal SH-SY5Y human cells with H2O2. Mediated by ROS, including H2O2 and its derivatives, oxidative stress alters numerous cellular processes, such as mitochondrial regulation and cell signaling, propagating cellular injury that leads to incurable neurodegenerative diseases. These results, and t…
Morphological Characterization of the Entire Interneuron Population Reveals Principles of Neuromere Organization in the Ventral Nerve Cord ofDrosophi…
2011
Decisive contributions to our understanding of the mechanisms underlying the development of the nervous system have been made by studies performed at the level of single, identified cells in the fruit flyDrosophila. While all the motor neurons and glial cells in thoracic and abdominal segments of theDrosophilaembryo have been individually identified, few of the interneurons, which comprise the vast majority of cells in the CNS, have been characterized at this level. We have applied a single cell labeling technique to carry out a detailed morphological characterization of the entire population of interneurons in abdominal segments A1–A7. Based on the definition of a set of spatial parameters…
Computation of inverse functions in a model of cerebellar and reflex pathways allows to control a mobile mechanical segment.
2003
Abstract The command and control of limb movements by the cerebellar and reflex pathways are modeled by means of a circuit whose structure is deduced from functional constraints. One constraint is that fast limb movements must be accurate although they cannot be continuously controlled in closed loop by use of sensory signals. Thus, the pathways which process the motor orders must contain approximate inverse functions of the bio-mechanical functions of the limb and of the muscles. This can be achieved by means of parallel feedback loops, whose pattern turns out to be comparable to the anatomy of the cerebellar pathways. They contain neural networks able to anticipate the motor consequences …
Analysis of neuronal networks in the visual system of the cat using statistical signals--simple and complex cells. Part II.
1978
Superimposing additively a two-dimensional noise process to deterministic input signals (bars) the neurons of area 17 show a class-specific reaction for the task of signal extraction. Moving both parts of the signals simultaneously and varying the signal to noise ratio (S/N) the simple cells achieve the same performance as resulted from the psychophysical experiment. Type I complex cells extract moving deterministic signals (i.e. bars) from the stationary noise, whereas in the answers of Type II complex cells the statistical parts of the signals predominate. Considering the different cell types each as a series of a linear and a nonlinear system one obtains the cell specific space-time freq…
On localization of moving objects in the visual system of cats.
1980
In cortical areas direction-specific receptive fields occur systematically. Direction specifity is based on unsymmetric coupling of neurons. Such a coupling allows an exact localization of moved stimuli. For this task, the asymmetry in the time domain is compensated for by a spatial asymmetry.
Analysis of neuronal networks in the visual system of the cat using statistical signals
1976
If the input signals of the visual system in the cat are statistical patterns in space and time, a complete system analysis can be carried out. What counts here as a system are the neuronal networks between retina and recording site. In the case of linearity, one obtains the temporal impulse response functions at every point in the receptive field with the aid of correlation methods. The measuring time is about one minute. Some aspects of the procedure are explained in terms of examples. The method of measurement also makes it possible to determine the characteristic function of the system in time and space between different recording sites within the cortex. It is possible to specialize th…
Sparse Distributed Representation of Odors in a Large-scale Olfactory Bulb Circuit
2013
In the olfactory bulb, lateral inhibition mediated by granule cells has been suggested to modulate the timing of mitral cell firing, thereby shaping the representation of input odorants. Current experimental techniques, however, do not enable a clear study of how the mitral-granule cell network sculpts odor inputs to represent odor information spatially and temporally. To address this critical step in the neural basis of odor recognition, we built a biophysical network model of mitral and granule cells, corresponding to 1/100th of the real system in the rat, and used direct experimental imaging data of glomeruli activated by various odors. The model allows the systematic investigation and g…