scholarly journals An identifiable molluscan neuron responds to changes in earth-strength magnetic fields

1991 ◽  
Vol 161 (1) ◽  
pp. 1-24 ◽  
Author(s):  
K. J. Lohmann ◽  
A. O. Willows ◽  
R. B. Pinter
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neural Circuit ◽  
Cellular Level ◽  
Molluscan Neuron ◽  
Marine Mollusc ◽  
Neurophysiological Mechanisms ◽  
Magnetic Sense ◽  
Animal Preparation ◽  
The Brain

Diverse animals can orient using geomagnetic cues, but little is known about the neurophysiological mechanisms that underlie magnetic field detection. The marine mollusc Tritonia diomedea (Bergh) has a magnetic sense and its nervous system is amenable to cellular-level electrophysiological analysis. In a semi-intact whole-animal preparation, intracellular recordings from the large, visually identifiable neurons left pedal 5 (LPe5) and right pedal 5 (RPe5) in the brain of Tritonia revealed enhanced electrical activity in response to changes in ambient earth-strength magnetic fields. No such changes in activity were observed in approximately 50 other neurons subjected to identical magnetic stimuli. The responses of LPe5 were characterized by increases in spiking frequency occurring about 6–16 min after the ambient magnetic field had been rotated to a new position. The response was abolished when the brain had been isolated from the periphery of the animal by severing nerves, a procedure that also transected prominent neurites of LPe5. We hypothesize that LPe5 is one component of a neural circuit mediating detection of the earth's magnetic field or orientation to it.

scholarly journals Decoding of the Skin Sensations to the Low Intensive Electric and Magnetic Fields

2021 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electric Field ◽  
Human Skin ◽  
Electric And Magnetic Fields ◽  
The Brain

The article represents the ability of the human skin sensitive receptors and receptors of the proprioception to detect and code the very low intensive electric and magnetic fields. Was made the classification of the skin sensations to the electric field (EF) and magnetic field (MF) – 34 kind sensations. Was made the electrophysiology pattern of every one sensation to the electric field (EF) and magnetic field (MF) – how the skin sensitive receptors and receptors of proprioception code the electric and magnetic fields to be translate from the sensitive nerve to the brain.

Metaphors for the Effects of Weak, Sequentially Complex Magnetic Fields

1997 ◽  
Vol 85 (1) ◽  
pp. 204-206 ◽  
Author(s):  
M. A. Persinger
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Sound Pressure ◽  
Biological Information ◽  
Receptor Subtypes ◽  
Sensory Thresholds ◽  
Magnetic Field Effects ◽  
Biological Responses ◽  
Complex Magnetic Field ◽  
The Brain

Metaphors to explain the effects of weak, complex magnetic fields upon the neuromatrices of organisms are suggested. The ratio of the amplitude of the time-varying components to steady-state components for complex magnetic field for effective biological responses may display Weber values that are similar to those for the electrical activity of the brain, the detection of changes in sound pressure by the ear and for more classical sensory thresholds. The nonlinear, suprathreshold characteristic of weak magnetic field effects would be similar to the effective narrow windows of concentrations of ligands values for receptor subtypes with different affinities. Signals composed of trains of between 100 and 1000 successive, fast (1 to 3 msec.) transients, which would contain the most biological information, would require low amplitudes to which the substrates could respond and with which the neuromatrix could resonate.

scholarly journals Neuronal circuits and the magnetic sense: central questions

2020 ◽  
Vol 223 (21) ◽  
pp. jeb232371
Author(s):  
E. Pascal Malkemper ◽  
Simon Nimpf ◽  
Gregory C. Nordmann ◽  
David A. Keays
Keyword(s):  
Magnetic Field ◽  
Earth’S Magnetic Field ◽  
Magnetic Circuits ◽  
Earth's Magnetic Field ◽  
The Central Nervous System ◽  
Magnetic Sense ◽  
Behavioural Experiments ◽  
The Brain ◽  
Spatial Maps

ABSTRACTMagnetoreception is the ability to sense the Earth's magnetic field, which is used for orientation and navigation. Behavioural experiments have shown that it is employed by many species across all vertebrate classes; however, our understanding of how magnetic information is processed and integrated within the central nervous system is limited. In this Commentary, we review the progress in birds and rodents, highlighting the role of the vestibular and trigeminal systems as well as that of the hippocampus. We reflect on the strengths and weaknesses of the methodologies currently at our disposal, the utility of emerging technologies and identify questions that we feel are critical for the advancement of the field. We expect that magnetic circuits are likely to share anatomical motifs with other senses, which culminates in the formation of spatial maps in telencephalic areas of the brain. Specifically, we predict the existence of spatial cells that encode defined components of the Earth's magnetic field.

Sources of magnetic sensory input to identified neurons active during crawling in the marine mollusc Tritonia diomedea

1999 ◽  
Vol 202 (21) ◽  
pp. 3029-3036 ◽  
Author(s):  
I.R. Popescu ◽  
A.O. Willows
Keyword(s):  
Magnetic Field ◽  
Action Potential ◽  
Action Potentials ◽  
Anatomical Site ◽  
Marine Mollusc ◽  
Tritonia Diomedea ◽  
Peripheral Locus ◽  
Ganglion Neurons ◽  
The Brain ◽  
Potential Rate

Although the nudibranch mollusc Tritonia diomedea orients to the geomagnetic field, the anatomical site and the mechanism of the geomagnetic transducer are not known. Previous work on semi-intact preparations of Tritonia diomedea in which the brain is intact and nerve connections to the periphery are maintained showed that identifiable pedal ganglion neurons Pd5 fired an increased number of action potentials when the horizontal component of the ambient magnetic field was rotated. This response disappeared when all nerves emerging from the brain were cut, suggesting a peripheral locus for the geomagnetic transducer. In the present work, we recorded intracellularly from Pd5 in preparations in which all peripheral nerves were cut except those containing the axons of neurons Pd5 (pedal nerves 2 and 3). These uncut, mixed, sensory-motor trunks innervate the locomotory epithelium of the foot upon which the animal crawls. In this further-reduced preparation, Pd5 again responded to magnetic field rotations with action potentials. To determine the direction of this action potential transmission in response to magnetic field rotations, we analyzed extracellular recordings from nerves containing the Pd5 axons and found that action potentials elicited in Pd5 by magnetic stimuli originate centrally and are transmitted peripherally. In addition, we have explored the behavioral function of Pd5 neurons by simultaneously recording intracellular electrical activity and crawling rate of the semi-intact animal. A significant correlation was found between crawling rate and Pd5 action potential rate. We also found that action potentials in dorsal swim interneurons depolarized both Pd5 and the established locomotion motoneuron Pd21.

Static magnetic field modulates rhythmic activities of a cluster of large local interneurons in Drosophila antennal lobe

2011 ◽  
Vol 106 (5) ◽  
pp. 2127-2135 ◽  
Author(s):  
Ying Yang ◽  
Ying Yan ◽  
Xiaolu Zou ◽  
Chuchu Zhang ◽  
Heng Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Antennal Lobe ◽  
Neural Circuit ◽  
Superconducting Magnets ◽  
Projection Neurons ◽  
Field Exposure ◽  
Magnetic Field Exposure ◽  
Local Interneurons ◽  
Spontaneous Activities

With the development of superconducting magnets, the chances of exposure to intense static magnetic fields (SMFs) have increased. Therefore, safety concerns related to magnetic field exposure need to be studied, especially the effects of magnetic field exposure on the central nervous system. Only a limited number of studies prove a direct connection between magnetic fields and electrophysiological signal processing. Here we described a cluster of large local interneurons (LNs) located laterally to each antennal lobe of Drosophila melanogaster, which exhibit extensive arborizations throughout the whole antennal lobe. Dual recordings showed that these large LNs demonstrated rhythmic spontaneous activities that correlated with other LNs and projection neurons (PNs) in the olfactory circuit. The results suggest that 3.0-T SMF can interfere with the properties of the action potential, rhythmic spontaneous activities of large LNs, and correlated activity in pairs of ipsilateral large LN/LN in the olfactory circuit. This indicates that Drosophila can be an ideal intact neural circuit model and that the activities of the olfactory circuit can be used to evaluate the effects of magnetic field stimulations.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

Peculiarity Parameters

1976 ◽  
Vol 32 ◽  
pp. 233-254
Author(s):  
H. M. Maitzen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Theoretical Work ◽  
Observational Evidence ◽  
Rotator Model ◽  
Peculiar Behaviour ◽  
Field Spectrum ◽  
Oblique Rotator ◽  
Ap Stars ◽  
The Way

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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