Triggered activity must be added to spontaneous activity and to circus movement as a cause for extrasystoles and tachycardias of either atrial or ventricular origin. The activity of a triggerable focus requires phase 4 depolarization caused by an afterpotential; this distinguishes it from the activity seen in circus movement. A triggerable focus becomes rhythmically active only if driven at a c...

The extent to which regenerative action potentials invade hippocampal CA1 pyramidal dendrites is dependent on both recent activity and distance from the soma. Previously, we have shown that the amplitude of back-propagating dendritic action potentials can be increased by activating either protein kinase A (PKA) or protein kinase C (PKC) and a subsequent depolarizing shift in the activation curv...

Layer V pyramidal cells of the somatosensory cortex operate with two spike initiation zones. Sub-threshold depolarizations are strongly attenuated along the apical dendrite linking the somatic and distal dendritic spike initiation zones. Sodium action potentials, on the other hand, are actively back-propagating from the axon hillock into the apical tuft. There they can interact with local excit...

We investigated the actions of dantrolene Ca(2+)-induced on Ca(2+)-release (CICR) evoked by action potentials in cultured rat sensory neurons. The effect of dantrolene on action potential after-depolarization and voltage-activated calcium currents was studied in cultured neonatal rat dorsal root ganglion cells (DRG) using the whole-cell patch-clamp technique. Depolarizing current injection evok...

The study by Sutton and colleagues in this issue is the first to measure in humans the changes in the left ventricular refractory period and the duration of the ventricular monophasic action potential during the first minutes of acute ischaemia. 1 As the authors mention, the experimental data on this subject are rather confusing. Most studies report on a shortening of the refractory period, but...

The goal of this thesis is to analyze the generation of single unit extracellular action potentials (EAPs), and to explore pertinent issues in the interpretation of EAP recordings. I use the line source approximation to model the EAP produced by individual neurons. I compare simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons in vivo with simulations using the same ...

In this project we invectigated bidirectional propagation of action potentials in giant axon of lobster Homarus americanus. We found an asymetrical propagation in the giant axons from the first two walking legs, which have claws. The backpropagating antidromic action potential decreases the conduction velocity when we increase the stimulation voltage, while the forward propagating (orthodromic)...

Individual action potentials in axons can be detected in vitro using intrinsic optical signals. The principles of this detection technique are described here. The technique has been demonstrated using neuronal axons dissected from lobster. It would also be applicable to axons and active dendrites of cultured neurons with diameters somewhat larger than an optical wavelength. Using index-matching...

Background: The time and frequency features of motor unit action potentials (MUAPs) extracted from electromyographic (EMG) signal provide discriminative information for diagnosis and treatment of neuromuscular disorders. However, the results of conventional automatic diagnosis methods using MUAP features is not convincing yet.Objective: The main goal in designing a MUAP characterization system ...