Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neural Conduction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMedDate not supplied

The changes in the transmission functioning of the ulnar nerve in a high power magnetic field.

INTRODUCTION: The present study aims at exploring the changes in the functioning of the ulnar nerve in a high power magnetic field. METHODS: 12 volunteers with a healthy peripheral nervous system participated in the study. The ulnar nerve was selected from the upper organs as the site for study. The functioning of both the sensory and motor parts of the ulnar nerve in normal conditions was electromyographically tested. Then, using the same setting, the functioning of the nerve was electromyographically tested within a high power magnetic field (0.2 Tesla). With regard to the sensory function, the distal latency and the amplitude were examined. With regard to the motor section, the duration, amplitude of the evoked potentials, and latency from two sites--distal and proximal--were examined. These results of the two readings, taken in normal condition and in a high power magnetic field, as well as the motor neural conduction velocity, were compared. RESULTS: The statistical analyses indicated that the changes in both the distal latency and amplitude of the sensory part of the ulnar nerve were significant. However, the changes in the motor function of the nerve were not significant.

Adult↗
PubMedDate not supplied

Silent period(s.p.).

Explore the source record for details and available documents.

Electromyography↗
PubMed2002

Sequential pictorial presentation of neural interaction in the retina. 2. The depolarizing and hyperpolarizing bipolar cells at rod terminals.

Each rod is connected to one depolarizing and one hyperpolarizing bipolar cell. The synaptic connections of cone processes to each bipolar cell and presynaptically to the two rod-bipolar cell synapses establishes conditions for lateral interaction at this level. Thus, the cones raise the threshold for bipolar cell depolarization which is the basis for spatial brightness contrast enhancement and consequently for high visual acuity (Sjöstrand, 2001a). The cones facilitate ganglion cell depolarization by the bipolar cells and cone input prevents horizontal cell blocking of depolarization of the depolarizing bipolar cell, extending rod vision to low illumination. The combination of reduced cone input and transient hyperpolarization of the hyperpolarizing bipolar cell at onset of a light stimulus facilitates ganglion cell depolarization extensively at onset of the stimulus while no corresponding enhancement applies to the ganglion cell response at cessation of the stimulus, possibly establishing conditions for discrimination between on- vs. off-signals in the visual centre. Reduced cone input and hyperpolarization of the hyperpolarizing bipolar cell at onset of a light stimulus accounts for Granit's (1941) 'preexcitatory inhibition'. Presynaptic inhibition maintains transmitter concentration low in the synaptic gap at rod-bipolar cell and bipolar cell-ganglion cell synapses, securing proportional and amplified postsynaptic responses at these synapses. Perfect timing of variations in facilitatory and inhibitory input to the ganglion cell confines the duration of ganglion cell depolarization at onset and at cessation of a light stimulus to that of a single synaptic transmission.

Amacrine Cells↗
PubMed2002

Burst synchrony patterns in hippocampal pyramidal cell model networks.

Types of. mechanisms for and stability of synchrony are discussed in the context of two-compartment CA3 pyramidal cell and interneuron model networks. We show how the strength and timing of inhibitory and excitatory synaptic inputs work together to produce either perfectly synchronized or nearly synchronized oscillations, across different burst or spiking modes of firing. The analysis shows how excitatory inputs tend to desynchronize cells, and how common, slowly decaying inhibition can be used to synchronize them. We also introduce the concept of 'equivalent networks' in which networks with different architectures and synaptic connections display identical firing patterns.

Action Potentials↗
PubMed1975

[The relationship between the second zone of the auditory cortex and the medial geniculate body and first auditory zone].

Extracellular and intracellular responses of the second auditory (AII) cortical neurons to stimulation of geniculocortical fibres and first auditory cortex (AI) were studied in experiments carried out on cats immobilized with d-tubocurarine. It is shown that in these neurons there appear antidromic, mono-, di- and polysynaptic spike potentials to geniculate and AI stimulation. The number of antidromic reactions was about twice as low as in AI under the same conditions. Di- and polysynaptic responses predominated among orthodromic reactions. Intracellular recording revealed EPSP, EPSP-IPSP and primary IPSP in AII neurons. Response latencies in AII neurons to AI stimulation were in the range of 0.75-6.0, 6.1-16.0, 18.0-23.0 and 60.100 ms. After the medial geniculate body was removed, the number of responses with a latency of 6.1-16.0 ms decreased considerably. In some neurons spike pontentials appeared both to geniculate and AI stimulation. Comparison of the response latencies at both types of stimulation showed that impulses from AI come in AII not only to the neurons that are inputs for MGB impulses but also to neurons in the sebsequent link of intracortical neuronal chain. In most AII neurons disynaptic IPSP appeared at AI stimulation. Only in one case IPSP with a latency of 1.0 ms was recorded being probably monosynaptic.

Animals↗
PubMed2002

Hypocretins (orexins) regulate serotonin neurons in the dorsal raphe nucleus by excitatory direct and inhibitory indirect actions.

The hypocretins (hcrt1 and hcrt2) are expressed by a discrete population of hypothalamic neurons projecting to many regions of the CNS, including the dorsal raphe nucleus (DRN), where serotonin (5-HT) neurons are concentrated. In this study, we investigated responses to hcrts in 216 physiologically identified 5-HT and non-5-HT neurons of the DRN using intracellular and whole-cell recording in rat brain slices. Hcrt1 and hcrt2 induced similar amplitude and dose-dependent inward currents in most 5-HT neurons tested (EC50, approximately 250 nm). This inward current was not blocked by the fast Na+ channel blocker TTX or in a Ca2+-free solution, indicating a direct postsynaptic action. The hcrt-induced inward current reversed near -18 mV and was primarily dependent on external Na+ but not on external or internal Ca2+, features typical of Na+/K+ nonselective cation channels. At higher concentrations, hcrts also increased spontaneous postsynaptic currents in 5-HT neurons (EC50, approximately 450-600 nm), which were TTX-sensitive and mostly blocked by the GABA(A) antagonist bicuculline, indicating increased impulse flow in local GABA interneurons. Accordingly, hcrts were found to increase the basal firing of presumptive GABA interneurons. Immunolabeling showed that hcrt fibers projected to both 5-HT and GABA neurons in the DRN. We conclude that hcrts act directly to excite 5-HT neurons primarily via a TTX-insensitive, Na+/K+ nonselective cation current, and indirectly to activate local inhibitory GABA inputs to 5-HT cells. The greater potency of hcrts in direct excitation compared with indirect inhibition suggests a negative feedback function for the latter at higher levels of hcrt activity.

Action Potentials↗
PubMed2003

Oral citicoline treatment improves visual pathway function in glaucoma.

BACKGROUND: Increased latency and reduced amplitude of visual evoked potentials (VEP), frequently encountered in ocular hypertension or open-angle glaucoma, suggest slowed neural conduction in the visual pathways. An improvement in VEP latency and amplitude has been reported following repeated intramuscular injections of citicoline, a neuroprotective drug. Our aim was to find whether citicoline given orally would produce a similar effect. MATERIAL/METHODS: VEP latency and amplitude were measured in 21 glaucomatous eyes prior to and after two bi-weekly courses of citicoline taken orally in a dose of 1 gram/day. The treatment courses were separated by a two-week break; post-treatment VEP measurement was performed two weeks after the end of the second treatment. RESULTS: 62% of the eyes showed a response to the treatment, with VEP latency reduced from 123.5 (3.9 SEM) ms to 111.9 (1.9 SEM) ms (P=0.0008), and VEP amplitude increased from 6.56 (1.39 SEM) to 7.88 (1.16 SEM) (P=0.04). CONCLUSIONS: Citicoline given orally improves visual evoked potentials in some glaucoma patients.

Administration, Oral↗
PubMed1992

[Hereditary sensory-motor polyneuropathy. Case report and problems in differential diagnosis].

The study reports a family in which three children were found to have marked sensory-motor polyneuropathy. Clinical investigations revealed a recessive hereditary form of highly progredient mostly motor polyneuropathy with atrophy and weakness of distal muscle groups and electrophysiologic evidence of neurogenic lesion-delayed neural conduction. Apart from the peripheral nerves, clinical examination and additional investigations showed that the degenerative process encompassed central nerve system structures, posterior bundles of the spinal cord, spinal cerebral pathways, cerebellum and cerebrum (cerebral sings, mental retardation, epilepsy, brain atrophy on CT, increased IGG in the liquor are present). Although clinical and electrophysiological analyses suggest type III HSMN, muscle and nerve biopsy, as well as additional diagnostic methods broaden the differential diagnostic range toward other forms of hereditary polyneuropathy, whose differentiation in practice is, in spite of clear diagnostic criteria, rather difficult, due to the presence of its transitive forms.

Adolescent↗
PubMed1992

[Brain-stem auditory pathways: effects of atropine].

The efferent pathways exert a control action on the function of the cochlear nucleus and hair cells. Acetylcholine is the neurotransmitter of the centrifugal system and its action can be blocked by Atropine. In order to give a contribution to the knowledge of the function of the efferent bundle, Auditory Brainstem Responses (ABRs) and Acoustic Reflex Latencies (ARLs) have been examined in 10 young normal subjects there was also a decrease in latency greater than or equal to 100 microseconds by at least other two waves. The only statistically significant difference was relative to the latency mean value of the wave III recorded in contralateral derivation at 11 pps. The ARLs, after the infusion of atropine, showed a statistically significant increase in 7 of the 10 cases; no change was recorded in the AR amplitude. It can be concluded that the pharmacological block of the olivo-cochlear bundle determines a delay in the neural conduction of the acoustic impulses; this finding means that the atropine can inhibit the facilitating activity of the efferent system on the brainstem afferent pathways.

Acetylcholine↗
PubMed2003

TMS in stroke.

Explore the source record for details and available documents.

Brain Mapping↗
PubMed2004

Convergence of forelimb afferent actions on C7-Th1 propriospinal neurones bilaterally projecting to sacral segments of the cat spinal cord.

Propriospinal neurones located in the cervical enlargement and projecting bilaterally to sacral segments of the spinal cord were investigated electrophysiologically in eleven deeply anaesthetized cats. Excitatory or inhibitory postsynaptic potentials from forelimb afferents were recorded following stimulation of deep radial (DR), superficial radial (SR), median (Med) and ulnar (Uln) nerves. 26 cells were recorded from C7, 22 from C8 and 3 from Th1 segments. The majority of the cells were located in the Rexed's laminae VIII and the medial part of the lamina VII. In 10 cases no afferent input from the forelimb afferents was found. In the remaining neurones effects were evoked mostly from DR (88%) and Med (63%), less often from SR (46%) and Uln (46%). Inhibitory actions were more frequent than excitatory. The highest number of IPSPs was evoked from high threshold flexor reflex afferents (FRA)--all connections were polysynaptic. However, inhibitory actions were often evoked from group I or II muscle afferents (polysynaptic or disynaptic) and, less frequently, from cutaneous afferents (mostly polysynaptic). Di- or polysynaptic IPSPs often accompanied monosynaptic EPSPs from group I or II muscle afferents. Disynaptic or polysynaptic EPSPs from muscle and cutaneous afferents were also recorded in many neurones, while polysynaptic EPSPs from FRA were observed only exceptionally. Various patterns of convergence in individual neuronal subpopulations indicate that they integrate different types of the afferent input from various muscle and cutaneous receptors of the distal forelimb. They transmit this information to motor centers controlling hind limb muscles, forming a part of the system contributing to the process of coordination of movements of fore--and hind--limbs.

Afferent Pathways↗
PubMedDate not supplied

Cortical silent period prolongation in spinocerebellar ataxia type 2 (SCA2).

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder mapped on chromosome 12. Different results have been reported in spinocerebellar ataxias following transcranial magnetic stimulation (TMS). TMS-induced cortical silent period (CSP) was prolonged in different cerebellar disorders. Here we evaluate the duration of the TMS-induced CSP following a single magnetic stimulus in a large homogeneous group of SCA2 patients compared with idiopathic cerebellar ataxia (IDCA) patients with similar disease duration and severity, and in 20 healthy controls. The CSP duration in both arm and leg muscles was significantly (p<0.005) longer in patients than in controls. A significant positive correlation between disease duration and CSP prolongation in both SCA2 and IDCA was found. No correlation between age, onset and CSP duration emerged in either group. This study shows a prolongation of the TMS-induced silent period in both SCA2 and IDCA indicating that the cortical inhibitory mechanism is dependent on the disease duration and severity. Thus, the cerebellum seems to exert a pliable physiological influence on the cortico-spinal system through control of inhibitory cortical interneurons.

Adult↗
PubMed2004

Neural network model to generate head swing in locomotion of Caenorhabditis elegans.

Computer simulation of the neural network composed of the head neurons of Caenorhabditis elegans was performed to reconstruct the realistic changes in the membrane potential of motoneurons in swinging the head for coordinated forward locomotion. The model neuron had ion channels for calcium and potassium, whose parameters were obtained by fitting the experimental data. Transmission properties of the chemical synapses were set as graded. The neural network involved in forward movement was extracted by tracing the neuronal activity flow upstream from the motoneurons connected to the head muscles. Simulations were performed with datasets, which included all combinations of the excitatory and inhibitory properties of the neurons. In this model, a pulse input entered only from motoneuron VB1, and activation of the stretch receptors on SAA neurons was necessary for the periodic bending. The synaptic output property of each neuron was estimated for the alternate contraction of the dorsal and ventral muscles. The AIB neuron was excitatory, RIV and SMD neurons seemed to be excitatory and RMD and SAA neurons seemed to be inhibitory. With datasets violating Dale's principle for the SMB neuron, AIB neuron was excitatory and RMD neuron was inhibitory. RIA, RIV and SMD neurons seemed to be excitatory.

Animals↗
PubMed1992

Segmental reflex organization in endurance-trained athletes and untrained subjects.

In an effort to investigate the effects of training on spinal reflex pathways in humans, we measured the isometric force-time curve of the patellar (PTR) and Achilles (ATR) tendon-tap reflex in 12 endurance-trained (ET) athletes and 12 control (C) subjects. We also conditioned the tendon jerk with a contralateral or ipsilateral tendon-tap stimulus, to ascertain the effects of segmental inputs on crossed-spinal reflex activity. The conditioning stimulus preceded the test reflex by 25, 40, 55, 70, 85, 100, 115, 130, or 145 ms. The results demonstrated significant differences in control reflexes and conditioned reflexes between the two groups. A contralateral patellar tendon-tap produced a significantly greater excitatory effect to the contralateral quadriceps motoneurons for the ET group, whereas a contra- or ipsilateral conditioning caused a significantly greater inhibitory effect to the triceps surae motoneurons for the ET athletes. These results demonstrate that motoneuron excitability changes can be produced as a result of ipsi- and contralateral segmental inputs, and raise the possibility that trained athletes demonstrate different reflex recovery profiles. Several neurophysiological mechanisms are proposed to contribute to these changes.

Achilles Tendon↗
PubMed1975

[Work dominance and its age-related development].

When studying working industrial processes, peculiar displays of the dominant corresponding to common signs of the Ukhtomsky dominant, were revealed. Some physiological processes characteristic of the dominant were studied in their developing in children of different age and in adolescents.

Adolescent↗