Search results for "Action Potentials"
showing 10 items of 192 documents
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…
Cerebral activation in patients with somatoform pain disorder exposed to pain and stress: an fMRI study.
2006
Patients with somatoform pain disorders are supposed to suffer from an early acquired defect in stress regulation. In order to look for common alterations of the pain- and stress-responsive cortical areas, we prospectively recorded cerebral activations induced by pin-prick pain, by cognitive stress and emotional stress using functional magnetic resonance imaging (fMRI) in a group of 17 patients and an age-matched control group. In addition, the hippocampal volumes of both groups were measured. Patients showed increased activations of the known pain-processing areas (thalamus, basal ganglia, operculo-insular cortex), but also of some prefrontal, temporal and parietal regions during first pai…
The Disease-Specific Phenotype in Cardiomyocytes Derived from Induced Pluripotent Stem Cells of Two Long QT Syndrome Type 3 Patients
2013
Long QT syndromes (LQTS) are heritable diseases characterized by prolongation of the QT interval on an electrocardiogram, which often leads to syncope and sudden cardiac death. Here we report the generation of induced pluripotent stems (iPS) cells from two patients with LQTS type 3 carrying a different point mutation in a sodium channel Nav1.5 (p.V240M and p.R535Q) and functional characterization of cardiomyocytes (CM) derived from them. The iPS cells exhibited all characteristic properties of pluripotent stem cells, maintained the disease-specific mutation and readily differentiated to CM. The duration of action potentials at 50% and 90% repolarization was longer in LQTS-3 CM as compared t…
GAA trinucleotide repeat expansion in variant Friedreich's ataxia families.
1997
Phenotypic variants in Friedreich's ataxia include late onset, preservation of the lower limbs tendon reflexes, and slow progression. We describe clinical and electrophysiological features from three families with Friedreichlike phenotypes. Friedreich's ataxia diagnosis was confirmed by finding two allelic expansions of the GAA trinucleotide repeat at the X25 gene. In family 1 both patients had a late-onset phenotype with preservation of knee and ankle jerks, lack of cardiomyopathy, and preserved H reflex. One of them did not have electrophysiologic evidence of sensory axonal neuropathy. Patients from family 2 showed variability in the age of onset, and 2 out of 3 affected children had hype…
Induction of vascular endothelial growth factor release by transcutaneous frequency modulated neural stimulation in diabetic polyneuropathy
2008
Background: Pharmacological treatment for diabetic polyneuropathy (DP) has shown limited benefit; frequency-modulated electrical stimulation (FREMS) has shown positive results in pain control and nerve conduction velocity in DP. Objective: To investigate the effects of FREMS vs transcutaneous electrical nerve stimulation (TENS) on the release of vascular endothelial growth factor (VEGF) in Type 2 diabetic and in non-diabetic subjects. Methods: 10 non-diabetic [mean age 37±5 yr; females (F)/males (M): 6/4] and 10 Type 2 diabetic subjects (mean age 52±6 yr; F/M: 5/5) with DP underwent TENS (for 10 min) followed by 30 min interval without electrical stimulation, and then FREMS (for 10 min) ove…
Functional properties of motor units in motor neuron diseases and neuropathies.
1997
The relationship between the size of single motor unit (MU) action potentials and their twitch properties was estimated in patients with spinal muscular atrophy (SMA, n = 5) and amyotrophic lateral sclerosis (ALS, n = 10), as well as in patients with peripheral nerve lesions (PNL, n = 9). The data obtained from these groups were compared to normal controls (n = 8). In controls, the single MU twitch force was highly correlated to the corresponding EMG potential size in terms of macro EMG area. An enlargement of MUs, due to collateral sprouting and reflected by increased potential size and twitch force, was found in regenerating PNL and in slowly progressing SMA. Both parameters were highly c…
Extra-tympanic electrocochleography in a normal population. A descriptive study.
2015
Abstract Introduction and objectives Extra-tympanic electrocochleography is an electrophysiological register obtained after stimulating the cochlea with an audible stimulus. This stimulus is applied using an earphone over the external auditory canal, while the electrical activity is registered by surface electrodes. There are few studies that analyse normal electrocochleography in our environment. Thus, the main objective of our study was to regularise the values obtained with electrocochleography in ears without any otoneurological diseases. We explain in detail the process of obtaining the register. Methods Sixty healthy ears were studied by extratympanic electrocochleography. Statistical…
Age-related decreases in motor unit discharge rate and force control during isometric plantar flexion.
2012
Aging is related to multiple changes in muscle physiology and function. Previous findings concerning the effects of aging on motor unit discharge rate (DR) and fluctuations in DR and force are somewhat contradictory. Eight YOUNG and nine OLD physically active males performed isometric ramp (RECR) and isotonic (ISO) plantar flexions at 10 and 20% of surface EMG at MVC. Motor unit (MU) action potentials were recorded with intramuscular fine-wire electrodes and decomposed with custom build software "Daisy". DR was lower in OLD in RECR-10% (17.9%, p0.001), RECR-20% (15.8%, p0.05), ISO-10% (17.7%, p0.01) and ISO-20% (14%, n.s.). In YOUNG force fluctuations were smaller at ISO-10% (72.1%, p0.001)…