No data available that match "neural conduction"

Ringo, Doty, Demeter and Simard, Cerebral Cortex 1994;4:331-343: a proof of the need for the spatial clustering of interneuronal connections to enhance cortical computation. (1/3268)

It has been argued that an important principle driving the organization of the cerebral cortex towards local processing has been the need to decrease time lost to interneuronal conduction delay. In this paper, I show for a simplified model of the cerebral cortex, using analytical means, that if interneuronal conduction time increases proportional to interneuronal distance, then the only way to increase the numbers of synaptic events occurring in a fixed finite time period is to spatially cluster interneuronal connections.  (+info)

Spinal cord-evoked potentials and muscle responses evoked by transcranial magnetic stimulation in 10 awake human subjects. (2/3268)

Transcranial magnetic stimulation (TCMS) causes leg muscle contractions, but the neural structures in the brain that are activated by TCMS and their relationship to these leg muscle responses are not clearly understood. To elucidate this, we concomitantly recorded leg muscle responses and thoracic spinal cord-evoked potentials (SCEPs) after TCMS for the first time in 10 awake, neurologically intact human subjects. In this report we provide evidence of direct and indirect activation of corticospinal neurons after TCMS. In three subjects, SCEP threshold (T) stimulus intensities recruited both the D wave (direct activation of corticospinal neurons) and the first I wave (I1, indirect activation of corticospinal neurons). In one subject, the D, I1, and I2 waves were recruited simultaneously, and in another subject, the I1 and I2 waves were recruited simultaneously. In the remaining five subjects, only the I1 wave was recruited first. More waves were recruited as the stimulus intensity increased. The presence of D and I waves in all subjects at low stimulus intensities verified that TCMS directly and indirectly activated corticospinal neurons supplying the lower extremities. Leg muscle responses were usually contingent on the SCEP containing at least four waves (D, I1, I2, and I3).  (+info)

Multiple point electrical stimulation of ulnar and median nerves. (3/3268)

A computer-assisted method of isolating single motor units (MUs) by multiple point stimulation (MPS) of peripheral nerves is described. MPS was used to isolate 10-30 single MUs from thenar and hypothenar muscles of normal subjects and patients with entrapment neuropathies, with the original purpose of obtaining a more representative mean motor unit potential for estimating the number of MUs in a muscle. The two important results that evolved from MPS however, were: (1) in the absence of 'alternation' MUs were recruited in an orderly pattern from small to large, and from longer to shorter latencies by graded electrical stimulation in both normal and pathological cases, (2) a comparison of the sizes of MUs recruited by stimulation proximal and distal to the elbow suggested that axonal branching can occur in the forearm 200 mm or more proximal to the motor point in intrinsic hand muscles.  (+info)

Acute conduction velocity changes in guinea-pigs after administration of diphenylhydantoin. (4/3268)

Motor nerve conduction velocity was measured after dosing guinea-pigs with 200-400 mumol/kg diphenylhydantoin (DPH) daily for three to four days. Conduction velocity fell by a mean value of 13% in animals that achieved plasma DPH levels over 200 mumol/l. There was no change in velocity with DPH levels below this value.  (+info)

Electrophysiological evidence for tetrodotoxin-resistant sodium channels in slowly conducting dural sensory fibers. (5/3268)

A tetrodotoxin (TTX)-resistant sodium channel was recently identified that is expressed only in small diameter neurons of peripheral sensory ganglia. The peripheral axons of sensory neurons appear to lack this channel, but its presence has not been investigated in peripheral nerve endings, the site of sensory transduction in vivo. We investigated the effect of TTX on mechanoresponsiveness in nerve endings of sensory neurons that innervate the intracranial dura. Because the degree of TTX resistance of axonal branches could potentially be affected by factors other than channel subtype, the neurons were also tested for sensitivity to lidocaine, which blocks both TTX-sensitive and TTX-resistant sodium channels. Single-unit activity was recorded from dural afferent neurons in the trigeminal ganglion of urethan-anesthetized rats. Response thresholds to mechanical stimulation of the dura were determined with von Frey monofilaments while exposing the dura to progressively increasing concentrations of TTX or lidocaine. Neurons with slowly conducting axons were relatively resistant to TTX. Application of 1 microM TTX produced complete suppression of mechanoresponsiveness in all (11/11) fast A-delta units [conduction velocity (c.v.) 5-18 m/s] but only 50% (5/10) of slow A-delta units (1.5 +info)

Diaphragm electromyogram measured with unilateral magnetic stimulation. (6/3268)

The purpose of this study was to establish the phrenic nerve conduction time (PNCT) for magnetic stimulation and further assess the relatively new technique of anterior unilateral magnetic stimulation (UMS) of the phrenic nerves in evaluating the diaphragm electromyogram (EMG). An oesophageal electrode was used to record the diaphragm compound muscle action potential (CMAP) elicited by supramaximal percutaneous electrical phrenic nerve stimulation (ES) and UMS from eight normal subjects. The oesophageal electrode used for recording the CMAP was positioned at the level of the hiatus and 3 cm below. The diaphragm CMAP was also recorded from chest wall surface electrodes in five subjects. All of the phrenic nerves could be maximally stimulated with UMS. A clear plateau of the amplitude of the CMAP was achieved for the right and left phrenic nerves. The mean amplitudes of the CMAP recorded from the oesophageal electrode were, for the right side, 0.74+/-0.29 mV (mean+SD) for ES and 0.76+/-0.30 mV for UMS with maximal power output, and for the left side 0.88+/-0.33 mV for ES and 0.80+/-0.24 mV for UMS. PNCT measured by the oesophageal electrode with ES and UMS with maximal output were, for the right side, 7.0+/-0.8 ms and 6.9+/-0.8 ms, respectively, and for the left side 7.8+/-1.2 ms and 7.7+/-1.3 ms, respectively. However, the CMAP recorded from chest wall surface electrodes with UMS was unsuitable for the measurement of PNCT. The results suggest that unilateral magnetic stimulation of the phrenic nerves combined with an oesophageal electrode can be used to assess diaphragmatic electrical activity and measure the phrenic nerve conduction time.  (+info)

Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin. (7/3268)

1. The effects of impulse activity on conduction in cutaneous C fibres have been examined in 46 microneurographic recordings from 11 normal subjects and 11 diabetic patients with normal nerve conduction. A tungsten microelectrode was inserted into a cutaneous nerve, usually the superficial peroneal close to the ankle, and intraneural microstimulation was used to identify an area of skin innervated. Three minute trains of 0.25 ms stimuli at 1, 2 and 4 Hz were then delivered to the surface of the skin, separated by intervals of 6 min with stimulation at 0.25 Hz. Slowing and block of conduction were measured from the nerve responses for up to seven C units per stimulation sequence. 2. Three types of C unit were distinguished by their responses to repetitive stimulation: type 1 units slowed progressively during the 3 min trains; slowing of type 2 units reached a plateau within 1 min; while type 3 units hardly slowed at all. Data from normal and diabetic subjects did not differ and were pooled. After 3 min at 2 Hz, the percentage increases in latency were for type 1, 28.3 +/- 9.7 (n = 63 units, mean +/- s.d.); for type 2, 5.2 +/- 1.6 (n = 14); and for type 3, 0.8 +/- 0.5 (n = 5), with no overlap. After 3 min at 4 Hz, 58 % of type 1 units (but no type 2 or 3 units) blocked intermittently. Recovery of latency after stimulation was faster for type 2 than for type 1 units, but conduction velocities of the three types were similar. 3. Type 1 units were identified as nociceptors and 7 type 2 units were identified as 'cold' fibres, activated by non-noxious cold, with no overlap in modality. None of the units tested was activated by weak mechanical stimuli or reflex sympathetic activation. 4. Spike waveforms were averaged for 18 type 1, 10 type 2 and 6 type 3 units. All units had predominantly triphasic action potentials with a major negative peak, but those of type 3 units were on average both smaller and briefer than those of type 1 and type 2 units. 5. It is concluded that repetitive electrical stimulation reliably differentiates nociceptive from cold-specific C fibres innervating human hairy skin, as has previously been shown for the rat. Cold fibres can propagate impulses continuously at much higher rates than nociceptive fibres. The nature of the type 3 units is unclear.  (+info)

Thapsigargin inhibits a potassium conductance and stimulates calcium influx in the intact rat lens. (8/3268)

1. An increase in lens cell calcium has long been associated with cortical cataract. Recently, it has been shown that thapsigargin induces a rise in lens cell calcium by release from endoplasmic reticulum stores. The effects of this rise on the optical and membrane characteristics of the lens were studied in the isolated rat lens. 2. The electrical characteristics of the isolated, perifused rat lens were measured using a two-internal microelectrode technique that permits measurement of plasma membrane conductance (Gm), membrane potential (Vm) and junctional conductance in the intact lens. 3. Thapsigargin (1 microM) induced a rapid overall depolarization of Vm that was accompanied by first a decrease and then an increase in Gm. 4. Replacing external Na+ with tetraethylammonium (TEA) abolished the decrease in Gm. However, a transient increase phase was still observed. 5. The changes in conductance were further characterized by measuring 22Na+ and 45Ca2+ influxes into the isolated lens. Thapsigargin (1 microM) induced a transient increase in 45Ca2+, but did not affect Na+ influx. 6. The Ca2+ channel blocker La3+ (10 microM) totally inhibited the thapsigargin-induced Ca2+ influx. It also blocked the increase in Gm observed in control and in Na+-free-TEA medium. In the absence of external calcium, thapsigargin induced a small depolarization in Vm. 7. These data indicate that thapsigargin induces both a decrease in K+ conductance and an increase in Ca2+ conductance. These probably result from release of stored Ca2+ and subsequent activation of store-operated Ca2+ channels (capacitative Ca2+ entry). 8. Thapsigargin application over the time course of these experiments (24 h) had no effect on junctional conductance or on the transparency of the lens.  (+info)

  • Salsano E, Fancellu R, Di Fede G, Ciano C, Scaioli V, Nanetti L, Politi LS, Tagliavini F, Mariotti C, Pareyson D. Lower limb areflexia without central and peripheral conduction abnormalities is highly suggestive of Gerstmann-Sträussler-Scheinker disease Pro102Leu. (
  • Neural Conduction" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (
  • This graph shows the total number of publications written about "Neural Conduction" by people in this website by year, and whether "Neural Conduction" was a major or minor topic of these publications. (
  • An EMG records electrical patterns as a graph, which your specialist can use to identify the cause of the abnormal neural activity and recommend a course of treatment. (
  • However, recent evidence suggests that neurons can change their conduction properties to send gradated signals. (
  • Once the researchers sorted the recorded spikes-signals of neural firing-by the axon from which they originated, they confirmed that spontaneous bursting activity lead to delays in axon conduction, particularly in more mature neurons. (
  • Neural progenitor cells (NPCs) emerged as a potential therapeutic approach for repairing and regenerating neurons after spinal cord injury. (
  • If the goal is to study neural behaviour that depends on physiological parameters, on the other hand, then use the Hodgkin-Huxley model, keeping in mind that only a small number (tens) of coupled neurons can be simulated in real-time. (
  • A recurrent neural network (RNN) is any network whose neurons send feedback signals to each other. (
  • 2004) from Chiba University reported that transplanted hematopoietic bone marrow stem cells in mice improved function recovery and differentiated into a number of cells including astrocytes, oligodendroglia, and neural precursors but not neurons. (
  • Computational neuroscience focuses on the description of biologically plausible neurons (and neural systems ) and their physiology and dynamics, and it is therefore not concerned with biologically unrealistic disciplines such as connectionism , machine learning , artificial neural networks , artificial intelligence and computational learning theory . (
  • 2. A method for inducing the in situ proliferation or differentiation of neural stem cells or neural progenitor cells located in a neural tissue of a human, the method comprising administering an amount of PDGF-BB of between 0.5 ng/kg/day to 500 ng/kg/day, to the neural tissue to induce the proliferation or differentiation of the neural stem cells or neural progenitor cells. (
  • In addition to the iPSC technology, the first reports about the possibility for direct transdifferentiation of somatic cells (including those of mesodermal origin) into neural stem/progenitor cells have appeared [5, (
  • In an attempt to address these questions, I first briefly describe the nature of species from which data derives and then evaluate whether what we now know of the molecules, tissues and physiology of sponges best reflects elements of a potential (pre)nervous system, loss of one, or elements of a distinct system specialized for non-neural functions. (
  • the neural control of development and physiology is often sidelined or omitted in favour of an exclusive focus on behaviour. (
  • Towards a Multifactorial Approach PART I the BASIS for ADVERSE NEURAL TENSION: Functional Anatomy and Physiology of the Nervous System. (
  • 11. The neural modulation system of claim 10, wherein the signal processing portion is configured to generate the blocking stimulus control signal for driving production of a magnetic field blocking stimulus configured to reversibly block conduction in the peripheral neural structure of the subject substantially immediately upon detecting the onset of the first activity state in the subject. (
  • 6. The method as set forth in claim 1 , wherein at least one of said first and second amplitude are increased over time to block conduction of said action potential in progressively smaller nerve fibers. (
  • These electrophysiological findings suggest that in vitamin B12 deficiency the higher segments of the cervical cord are usually affected first and that central sensory and motor conduction studies are sensitive methods for detecting such damage. (
  • The purpose of this study is to determine the extent of nerve involvement and to study the effect of corticosteroids combined with multidrug therapy on nerve damage in leprosy patients using sensory and motor nerve conduction studies. (
  • A cohort of 365 untreated multibacillary leprosy patients were prospectively studied using sensory and motor nerve conduction studies on upper and lower limb nerves. (
  • With central neural blockade these changes may be attributable to block of autonomic fibers, a direct depressant effect of the local anesthetic agent on various components of the cardiovascular system and/or the beta-adrenergic receptor stimulating action of epinephrine when present. (
  • Hyperkalemia, by affecting conduction in Purkinje fibers of ventricular muscle, or both, disturbed the normal sequence of septal and anterior wall depolarization and resulted in an ECG pattern that mimicked that of anteroseptal myocardial infarction. (
  • Onset latency is the time it takes for the stimulus to initiate an evoked potential and reflects the conduction along the fastest fibers. (
  • These data indicate, that Q-switched Nd:YAG laser irradiation can selectively impair neural conduction and axoplasmic transport in small sensory nerve fibers as compared to fast conducting fibers. (
  • Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). (
  • 2. The neural modulation system of claim 1, including a sensor operatively connected to the signal input structure and configured to generate the signal indicative of the activity state of the at least a portion of the body of the subject innervated by the peripheral neural structure responsive to an activity of the at least a portion of the body of the subject. (
  • 9. The neural modulation system of claim 1, wherein the blocking stimulus source includes a magnetic field source. (
  • 13. The neural modulation system of claim 10, wherein the signal processing portion is configured to:initiate a release period during which no blocking stimulus control signal is generated after an interval determined relative to the onset of generation of the blocking stimulus control signal. (
  • Therefore, saltatory conduction is thought as the hallmark of myelinated axons, which enables faster and more reliable propagation of signals than in unmyelinated axons of same outer diameter. (
  • This localized concentration of Na + channels resembles in structure the ion channel organization at the nodes of Ranvier, yet it is currently unknown whether this translates into an equivalent phenomenon of saltatory conduction or related-functional benefits and efficiencies. (
  • Sensory nerve conduction studies are performed via stimulation of a nerve (ie, sufficient to produce an action potential) at one point and measurement of the action potential at another point along the course of the nerve. (
  • But because an action potential alters the axonal membrane potential and thus the axon's conductivity, the finding that spontaneous high-frequency activity (as opposed to that induced by electrical stimulation) produces a similar effect suggests that that conduction slowing may be a more general phenomenon. (
  • The filter has a transfer response to attenuate a frequency of a neural stimulation signal. (
  • The switch is adapted to place the filter in the signal path when the neural stimulation signal is applied and to remove the filter from the signal path when the neural stimulation signal is not applied. (
  • the filter of the filter module includes a low pass filter to attenuate frequencies approximately equal to and higher than the frequency of the neural stimulation signal. (
  • 3. The filter module of claim 1 , wherein the filter includes a notch filter having a center frequency corresponding to the frequency of the neural stimulation. (
  • 5. The filter module of claim 3 , wherein the filter further includes a plurality of notch filters, each having a center frequency corresponding to a unique one of a plurality of harmonic frequencies for the frequency of the neural stimulation signal. (
  • 7. The filter module of claim 6 , wherein the adjustable notch filter includes a switched capacitor filter, the switched capacitor filter to receive a clock signal having a clock frequency corresponding to the frequency of the neural stimulation signal to provide a desired center frequency. (
  • 8. The filter module of claim 7 , further including a neural stimulation frequency detector to extract the clock signal from the neural stimulation signal. (
  • mister omfang efterhånden som det bevæger sig (højest nogle mm og når dermed aldrig ret langt ned langs en axon inden det fader ud). (
  • Gorza L, Saggin L, Sartore S, Ausoni S. An embryonic-like myosin heavy chain is transiently expressed in nodal conduction tissue of the rat heart. (
  • 2003) found that bone marrow cells, when transplanted with fetal neural stem cells, enhanced tissue repair and regeneration in injured spinal cords. (
  • We had also previously demonstrated that pharmaceutically or genetically blocking neprilysin activity improved vascular and neural deficits in diabetic rodents ( 4 - 9 , 14 ). (
  • In the present study, we investigated the therapeutic effects of EPO on the neurological function deficits and neural pathology caused by chronic alcoholism and the regulatory mechanisms. (
  • APT-II], when applied in the context of a multiple baseline ABA design, would improve the attention abilities of RW, a patient with mild conduction aphasia and concomitant attention and working memory deficits. (
  • The final section outlines the impact of individual congenital heart defects on the anatomy and function of the conduction system. (
  • By understanding the detailed anatomy of the neural manipulation, one can clearly see the potential for pathological change when nerves are restricted. (
  • This new scenario could mean there have been independent origins of complex neural signalling, or that sponges have lost nerves and the ability to send rapid directed signals. (
  • The evolution of extensive dendritic trees, coupled with branching axons, has led to the development of neural "wiring diagrams" of enormous complexity. (
  • The antibodies start to destroy the myelin insulation around the axons that assists with neural conduction. (
  • 2002) from the Kocsis laboratory and also in the Univeristy of Hokkaido found that bone marrow cells remyelinated spinal axons that had been demyelinated by x-radiation, in a manner similar to Schwann cells and neural precursor cells (Kocsis, et al. (
  • Mechanism of action: Lidocaine stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action. (
  • Nerve conduction studies and needle EMG are commonly performed by physical medicine and rehabilitation or neurology specialists to assess the ability of the nervous system to conduct electrical impulses and to evaluate nerve/muscle function to determine if neuromuscular disease is present. (
  • These may result in a conduction block to nerve impulses (due to MYELIN SHEATH dysfunction) or axonal loss. (
  • Eric Cherry]'s implant, designed to anchor a bone-conduction hear aid, turned out to be a great place to mount a low-cost Bluetooth speaker for his phone - at least when he's not storing paperclips behind his ear. (
  • A quick teardown and replacement of the stock speaker with a bone-conduction transducer from Adafruit took care of the electronics, which were installed in a 3D printed enclosure compatible with the implant. (
  • Evaluates hearing loss by comparing air conduction to bone conduction. (
  • reported a paper comprising six protocols for the reprogramming of bone marrow-derived human mesenchymal stem cells (MSCs) into neural stem cells by adding a cocktail of factors to the cell medium. (
  • Bursting is a high frequency but relatively short-lived firing pattern, thought to aid in neural maturation and plasticity. (
  • The sponge genomic 'toolkit' either reflects a simple, pre-neural system used to protect the sponge filter or represents the remnants of a more complex signalling system and sponges have lost cell types, tissues and regionalization to suit their current suspension-feeding habit. (
  • But the current genomic data forces us to ask hard questions: what do sponges really have in terms of a 'neural toolkit' and could it reflect the remnants of a more-sophisticated coordination system? (
  • Numerical Simulations of Dynamics Behaviour of the Action Potential of the Human Heart's Conduction System, Numerical Simulation Ricardo Lopez-Ruiz, IntechOpen, DOI: 10.5772/63017. (
  • Patterning of the mouse conduction system. (
  • Gorza L, Schiaffino S, Vitadello M. Heart conduction system: a neural crest derivative? (
  • Concepts from linear system theory were adapted to represent some aspects of neural dynamics, including solutions of simultaneous linear equations \(Y = AX\) using matrix theory, and concepts about cross-correlation. (
  • Understanding how the nervous system and its components fare as individuals age, how agerelated neural changes are manifested behaviorally, and how this knowledge may be used to improve the quality of life is an immensely daunting task because, irrespective of aging, the nervous system is bafflingly complex. (
  • 4. The method of claim 1 wherein said method induces the differentiation, migration, proliferation or survival of neural stem cells or neural progenitor cell in said patient. (
  • In this review, we will focus on the key signal cascades involved in the acquisition and maintenance of pluripotency and also analyze the current protocols for obtaining neural stem cells from iPSCs as well as through direct transdifferentiation. (
  • Recent progress in genomics, phylogenetics, developmental biology and the study of simple nervous systems has provided a wealth of new empirical information that bears on the earliest stages in neural evolution. (
  • The aim of this paper is to organize ideas and hypotheses in this area in a global way by charting the 'option space' for hypotheses about early neural evolution, making explicit the entire range of functions that early nervous systems may have played. (
  • Neural Conduction" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (
  • This article aims to summarize the scientific knowledge accumulated to date on the action potential and neural adaptation in the process of applying a constant stimulus. (
  • The definition has been expanded from congenital permanent bilateral, unilateral sensory, or permanent conductive hearing loss to include neural hearing loss (eg, "auditory neuropathy/dyssynchrony") in infants admitted to the NICU. (
  • The results demonstrated efficacy of sacubitril/valsartan in improving vascular and neural function was superior to valsartan alone. (
  • Increased expression of neprilysin could compromise vascular and neural function, and blocking activity of both angiotensin II and neprilysin would be expected to reduce oxidative stress and protect biologically active peptides necessary for normal vascular and neural function ( 14 ). (
  • Anderson (1968) initially described his intuitions about neural pattern recognition using a spatial cross-correlation function. (