Search results for "action potential"
showing 10 items of 233 documents
Control of irregular cardiac rhythm
2018
International audience; The aim of this work is to investigate the chaos control of the one di- mensional map which modelizes the duration of the current cardiac action potential (APD) as a function of the previous one. Using OGY control method, we obtain very satisfactory numerical results to stabilize the irregular heart rhythm into the normal rhythm.
Rapid developmental switch in the mechanisms driving early cortical columnar networks
2006
The immature cerebral cortex self-organizes into local neuronal clusters long before it is activated by patterned sensory inputs. In the cortical anlage of newborn mammals, neurons coassemble through electrical or chemical synapses either spontaneously or by activation of transmitter-gated receptors. The neuronal network and the cellular mechanisms underlying this cortical self-organization process during early development are not completely understood. Here we show in an intact in vitro preparation of the immature mouse cerebral cortex that neurons are functionally coupled in local clusters by means of propagating network oscillations in the beta frequency range. In the newborn mouse, this…
The relation between neuronal chloride transporter activities, GABA inhibition, and neuronal activity
2020
Abstract The intracellular chloride concentration [Cl−]i in neurons is regulated by a set of transmembrane transporters, with the Cl−-loader NKCC1 and the Cl−-extruder KCC2 as most relevant members. The expression of these transporters is tightly regulated, with the general trend that KCC2 expression is low in immature neurons, which are thus characterized by a high [Cl−]i. As [Cl−]i is the main factor determining the polarity of GABAergic responses, such a high [Cl−]i is related to depolarizing GABAergic responses. However, depolarizing GABAergic responses are not per se excitatory, but can also contribute to shunting inhibition. The excitatory/inhibitory action of GABAergic responses is m…
Breakdown of Thalamo-Cortical Connectivity Precedes Spike Generation in Focal Epilepsies
2017
Electroencephalography (EEG) spikes and focal epileptic seizures are generated in circumscribed cerebral networks that have been insufficiently described. For precise time and spatial domain network characterization, we applied in patients with focal epilepsy dense array 256-channel EEG recordings with causal connectivity estimation by using time-resolved partial directed coherence and 3T-magnetic resonance imaging-derived cortical and thalamus integrity reconstruction. Before spike generation, significant theta and alpha bands driven information flows alterations were noted from both temporal and frontal lobes to the thalamus and from the thalamus to the frontal lobe. Medial dorsal and ven…
The relative contribution to the plantar-flexor torque of the soleus motor units activated by the H reflex and M response in humans.
2000
Abstract This study proposes a method of quantifying the relative contribution to the plantar-flexor torque of soleus H and M responses evoked by tibial nerve stimulation. For ten subjects, the amplitude of the twitch produced by the H wave was plotted against the corresponding potential, for stimuli producing H without M (i.e. in the ascending portion of the H-recruitment curve). It was then assumed that the contribution of H to twitches produced by M plus H was similar for similar H waves on the curve-descending portion. Hence, the contribution of M was estimated, for the range of M waves including those accompanying H max . The estimated mechanical contributions of H and M wave increase …
Cortico-bulbar fibers to orofacial muscles: recordings with enoral surface electrodes.
1997
A new recording technique was developed to eliminate current problems on recording transcranial evoked facial muscle responses. A fork-shaped device equipped with 2 pairs of Ag/AgCl-electrodes was inserted enorally at the buccinator muscle level. Advantages offered by this method comprise clearly defined negative deflection of the compound muscle action potential, lack of relevant volume conduction from adjacent muscles, reliability of amplitude criteria, absence of interfering stimulus artifacts, easy achievement of preactivation, and noninvasive recording by surface electrodes. In 43 healthy subjects transcranial magnetic stimulation evoked contralateral responses at a mean latency and me…
Changes in cerebellar activation pattern during two successive sequences of saccades
2002
The changes in the cerebellar activation pattern of two successive fMRI scanning runs were determined for visually guided to‐and‐fro saccades in 12 healthy volunteers familiar with the study paradigm. Group and single subject‐analyses revealed a constant activation of the paramedian cerebellar vermis (uvula, tonsils, tuber, folium/declive), which reflects constant ocular motor activity in both runs. A significant decrease in activation of the cerebellar hemispheres found in the second run is best explained by either a decrease in attention or the effects of motor optimization and learning. The significant, systematic changes of the cerebellar activation pattern in two successive runs were n…
Spontaneous brain activity and EEG microstates. A novel EEG/fMRI analysis approach to explore resting-state networks.
2009
The brain is active even in the absence of explicit input or output as demonstrated from electrophysiological as well as imaging studies. Using a combined approach we measured spontaneous fluctuations in the blood oxygen level dependent (BOLD) signal along with electroencephalography (EEG) in eleven healthy subjects during relaxed wakefulness (eyes closed). In contrast to other studies which used the EEG frequency information to guide the functional MRI (fMRI) analysis, we opted for transient EEG events, which identify and quantify brain electric microstates as time epochs with quasi-stable field topography. We then used this microstate information as regressors for the BOLD fluctuations. S…
Rifle-balancing in precision shooting:behavioral aspects and psychophysiological implication
2007
This study investigated sharpshooters' strategies to control their rifle stability during the aiming period. Six elite and six pre-elite shooters completed a simulated realistic shooting task (laser rifle), and their performance was evaluated from behavioral and psychophysiological perspectives. The analysis of the rifle's barrel movement, indexing the shooter's behavioral performance, supported the view that rifle-balancing is an essential determinant of superior shooting performance. The psychophysiological data, i.e. the brain slow potentials, suggested that the shooters applied different rifle-hold strategies; the elite shooters concentrated primarily on achieving a stable rifle positio…
Information transfer in QT-RR dynamics: Application to QT-correction
2018
ABSTRACTThe relation between the electrical properties of the heart and the beating rate is essential for the heart functioning. This relation is central when calculating the “corrected QT interval” — an important measure of the risk of potentially lethal arrhythmias. We use the transfer entropy method from information theory to quantitatively study the mutual dynamics of the ventricular action potential duration (the QT interval) and the length of the beat-to-beat (RR) interval. We show that for healthy individuals there is a strong asymmetry in the information transfer: the information flow from RR to QT dominates over the opposite flow (from QT to RR), i.e. QT depends on RR to a larger e…