			Home About us Contact

Electrophysiological Differences (electrophysiological + difference)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Electrophysiological Differences of the Spontaneous Onset of Paroxysmal and Persistent Atrial Fibrillation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2007
STEFAN WEBER M.D.
Background: Information about the spatiotemporal organization of atrial activity at the onset of atrial fibrillation (AF) is still limited. Methods: AF mapping was performed in 30 patients with AF (mean age 53 ± 9 years, 26 males) by deploying a noncontact mapping balloon in the left atrium (LA). Twenty-four patients had paroxysmal AF and six patients had persistent AF. Three types of AF episodes were analyzed: nonsustained AF (lasting , 30 seconds), sustained AF (lasting > 30 seconds, with spontaneous conversion or requiring internal cardioversion and subsequent stable sinus rhythm), and persistent AF episodes (stable sinus rhythm lasting , 1 minute after cardioversion). Results: A total of 101 spontaneous AF onset episodes were analyzed. Analysis of AF onset showed that there was a progressive shortening of the initial cycle lengths from nonsustained episodes to sustained episodes and to persistent AF episodes. There was an earlier and more rapid reduction in the cycle lengths from persistent episodes to sustained episodes and to nonsustained episodes of AF (P < 0.05 for persistent vs sustained and for sustained vs nonsustained episodes). The development of multiwavelet activity and disorganization of conduction occurred earlier in persistent and sustained episodes than in nonsustained AF episodes. LA size was greater in patients with persistent AF episodes compared with patients with sustained or nonsustained AF episodes. Conclusions: Electrophysiological events that develop at the onset of AF seem to be different in different types of AF. A more rapid degeneration into the fibrillatory activity was observed in persistent and sustained AF than in nonsustained AF episodes. [source]

Binge Drinking Affects Attentional and Visual Working Memory Processing in Young University Students

ALCOHOLISM, Issue 11 2009
Alberto Crego
Background:, Binge Drinking (BD) typically involves heavy drinking over a short time, followed by a period of abstinence, and is common among young people, especially university students. Animal studies have demonstrated that this type of alcohol consumption causes brain damage, especially in the nonmature brain. The aim of the present study was to determine how BD affects brain functioning in male and female university students, during the performance of a visual working memory task. Methods:, Event-related potentials (ERPs) were recorded, with an extensive set of 32 scalp electrodes, in 95 first-year university students (age range 18 to 20 years), comprising 42 binge drinkers (BD) and 53 controls, in a visual "identical pairs" continuous performance task. Principal components analysis was used to identify and analyze the N2 (negative waveform with a latency around 200 to 300 ms related to attentional processes) and P3 (positive waveform with a latency around 300 to 600 ms related to working memory processes) components of the ERPs. Results:, In the matching condition of the task, the N2 component in central and parietal regions was significantly larger in the BD than in the control group. In the control group, the P3 component was larger in the matching than in the nonmatching condition in the frontal, central, and parietal regions, whereas the BD group did not show any significant differences between conditions in any region. Conclusions:, The results of this study confirm the presence of electrophysiological differences between young university student binge drinkers and controls during the execution of a visual task with a high working memory load. The larger N2 in the BD group suggests higher levels of attentional effort required by this group to perform the task adequately. The absence of any differences in the P3 component in the different conditions (matching and nonmatching stimuli) in the BD group suggests a deficiency in the electrophysiological differentiation between relevant and irrelevant information, which may reflect some impairment of working memory processes. [source]

Plasticity and ambiguity of the electrophysiological phenotypes of enteric neurons

NEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2009
K. Nurgali
Abstract, Advances in knowledge of enteric neurons electrophysiological characteristics have led to the realisation that the properties of the neurons are dependent on the state of the intestine, the region, the method of recording and the species. Thus, under different experimental conditions, electrophysiological studies cannot provide a reliable signature that identifies the functional type of neuron. In the normal guinea-pig small intestine, taken as a model tissue, neurons can be separated into two electrophysiological groups, S and AH neurons. Combined morphological and physiological studies place several classes of motor and interneurons in the S group, and intrinsic primary afferent neurons in the AH group. There is some evidence for subgroups of S neurons, in which electrophysiological differences are correlated with functional subtypes, but these subgroups have been incompletely investigated. Morphologically characterized Dogiel type II (DII) neurons are recognisable in many species, from mouse to human, but their electrophysiological characteristics are only partly conserved across species or cannot be satisfactorily defined due to technical difficulties. There is a strong need for a comprehensive analysis of channels and currents of S/Dogiel type I neuron subtypes, similar to the comprehensive analysis of AH/DII neurons in the guinea-pig, and similar studies need to be conducted in human and other species. The purpose of this review is to highlight that criteria used for electrophysiological definition of enteric neurons might not be sufficient to distinguish between functional classes of neurons, due to intrinsic properties of neuronal subpopulations, plasticity in pathological conditions and differences in recording techniques. [source]

Ionic Mechanisms and Vectorial Model of Early Repolarization Pattern in the Surface Electrocardiogram of the Athlete

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2008
Eduardo C. Barbosa M.D.
Background: The electrocardiogram (ECG) of the athlete displays particular characteristics as a consequence of both electrophysiological and autonomic remodeling of the heart that follows continued physical training. However, doubts persist on how these changes directly interact during ventricular activation and repolarization ultimately affecting surface ECG waveforms in athletes. Objective: This article considers an in deep rationale for the electrocardiographic pattern known as early repolarization based on both electrophysiological mechanisms at cellular level and the vectorial theory of the cardiac activation. Methods: The mechanism by which the autonomic remodeling influences the cardiac electrical activation is reviewed and an insight model of the ventricular repolarization based on ionic models and the vectorial theory of the cardiac activation is proposed. Results: Considering the underlying processes related to ventricular electrical remodeling, we propose that, in athletes' heart: 1) vagal modulation increases regional electrophysiological differences in action potential phases 1 and 2 amplitudes, thus enhancing a voltage gradient between epicardial and endocardial fibers; 2) this gradient affects depolarization and repolarization timing sequences; 3) repolarization wave front starts earlier on ventricular wall and partially overcomes the end of depolarization causing an upward displacement of the J-point, ST segment elevation, and inscription of magnified T-waves amplitudes leading to characteristic surface ECG waveform patterns. Conclusions: In athletes, the association between epicardial to endocardial electrophysiological differences and early repolarization ECG pattern can be demonstrated by the vectorial theory of the ventricular activation and repolarization. [source]