Direct Current Potential Research Articles

Direct-current potentials in the human brain evoked during timed cognitive performance.

WALTER et al.1 observed that when a human subject is presented with two sequentially paired stimuli so that the first serves to signal the occurrence of the second, a negative d.c. shift occurs during the interval between the stimuli in an averaged scalp EEG recording; he termed this phenomenon the “contingent negative variation” (CNV). CNV is frequently elicited with fixed foreperiod decision tasks, which may be said to include a “hold” phase, from the warning signal (WS) to the task stimulus (TS), and an “operate” phase, following the TS and terminating with the subject's response (R) to the TS (Fig. 1). CNV definitely occurs during the hold phase, so long as the subject is motivated and the task is sufficiently difficult2–6, but it has not been demonstrated that CNV is present during the operate phase. The tasks used in previous experiments have been so simple that TS and R occurred virtually simultaneously, and it could not be determined whether the termination of CNV covaries with the TS (the end of the hold phase) or with R (the end of the operate phase). In these experiments CNV was averaged during several complex cognitive tasks with considerably longer operate phases, and found to persist throughout the operate phase, for periods ranging up to 8 s after the TS.

Electrical transmission among neurons in the buccal ganglion of a mollusc, Navanax inermis.

The opisthobranch mollusc, Navanax, is carnivorous and cannibalistic. Prey are swallowed whole by way of a sudden expansion of the pharynx. The buccal ganglion which controls this sucking action was isolated and bathed in seawater. Attention was focused upon 10 identifiable cells visible on the ganglion's rostral side. Two cells were observed simultaneously, and each was penetrated with two glass microelectrodes, one for polarizing the membrane and the other for recording membrane potential variations. The coupling coefficients for direct current flow and action potentials of several identified cells were tabulated. Attenuation was essentially independent of the direction of current flow, but depended upon the relative size of the directly and indirectly polarized cells. The attenuation of subthreshold sinusoidally varying voltages increased with frequency above about 1 Hz. The coupling coefficient for spikes was lower than for DC due to greater high frequency attenuation. There is considerable similarity in the spontaneous PSP's of all cells, which is not due to the electrical coupling but to input from a common source. The 10 cells were not chemically interconnected but some were electrically connected to interneurons which fed back chemically mediated PSP's. The feedback can be negative or positive depending upon the membrane potential of the postsynaptic cell. We conclude that electrical coupling among the 10 cells plays a minor role in sudden pharyngeal contractions but that the dual electrical-chemical coupling with interneurons may be important in this respect.

Attention reduction and suppressed direct-current potentials in the human brain.

Distraction suppresses direct-current potentials (contingent negative variation) recorded from the human scalp. This reduction is accompanied by retarded reaction time. Contingent negative variation and reaction time appear to reflect a common process, attention.

Schizophrenic hallucinations and the transcephalic DC potential.

THE TRANSCEPHALIC direct current (TCDC) potential is the slowly changing aperiodic voltage recorded between the frontal and occipital emissary vein distributions on the midline surface of the head. 1-3 It now appears that a negative frontal shift reflects a lowered activation threshold of the subjacent frontal cortex, 4-6 and is related to the physiological substrate of the orienting reflex. 7 At an elementary level, a brief negative shift occurs when the subject attends to an exteroceptive or nonvestibular proprioceptive stimulus, and a positive shift is promoted by interoceptive stimuli. 2 Hunger and other externally oriented drive states promote a negative frontal baseline, and satiety states a positive one. 1,2,8 At a more complex functional level, anxiety increases the TCDC variance of a group without imparting a specific polarity to the potential. 2,8 An attempt to inhibit perception of an exteroceptive stimulus correlates

Tetraethylammonium and tetrodotoxin: effects on cochlear potentials.

Tetraethylammonium chloride, which is believed to decrease potassium conductance, and tetrodotoxin, which apparently decreases sodium conductance in nerve fibers, were introduced iontophoretically into the organ of Corti or the scala media of guinea pig cochlea. The former depressed the direct-current endocochlear potential and also the alternating-current cochlear microphonics (the receptor potential of the ear), but tetrodotoxin was ineffective except on the nerve impulses.

Elevation in brain temperature during paradoxical sleep.

During ordinary sleep, the temperature of the rabbit brain tended to drop, but during paradoxical sleep it rose sharply 0.1 degrees to 0.4 degrees C, a greater elevation than was observed during arousal. Changes in body temperature generally did not parallel the alterations in brain temperature. Shifts of direct-current potential in the brain are basically independent of the changes in brain temperature.

Some behavioural correlates of the transcephalic d.c. potential in cats.

NEURAL direct current (d.c.) potentials have recently received much attention1. A steady d.c. potential across amphibian cortex in a fronto-occipital plane has been observed2. These measurable exterior surface potentials are correlated with anaesthesia and sleep3,4. High correlations have been reported between transcephalic d.c. potential (measured between mid-forehead to low union), level of anaesthesia and electro-encephalograph (EEG)5. In the awake state the surface-recorded steady potentials are frontally negative, while in anaesthesia the frontal negativity decreases, that is, the forehead becomes more positive with respect to the occiput. The general relationship between EEG activity and behaviour (sleep–wakefulness) of humans and animals is, of course, well known6,7. This correlation of behaviour and EEG breaks down following the administration of anticholinergics such as atropine8. The EEG activity is slowed, whereas the animal appears excited. Such dissociation of EEG and behaviour under atropine has been observed in cat9, dog10 and rabbit11.

Progress in Brain Research , Vol. I: Brain Mechanisms Edited by Giuseppe Moruzzi, Alfred Fessard, and Herbert H. Jasper (review)

microscopy, microradiography, autoradiography ofbone-seeking radioisotopes, and the localization in bone of certain fluorescent compounds. (However, even though I have taken a rather active interest in radiation, isotopes, bone, abstract art, and symbolic logic, the illustration on the dustcover escapes my interpretation: it is a view from above ofa decapitated skeleton, the right shoulder joint ofwhich harbors a cluster of 13 giant-sized leadshots.) To summarize, then, the authors have been remarkably successful in their attempt to present a readable account ofa number ofsubjects related to radiation, isotopes, and bone and at the same time provide a clue to the specialized literature on these subjects. Goran C. H. Bauer, M.D. The Hospitalfor Special Surgery New York, New York Progress in Brain Research, Vol. I: Brain Mechanisms. Edited by Giuseppe Moruzzi, Alfred Fessard, and Herbert H.Jasper. New York: Elsevier, 1963. Pp. 493. $25.00. Psychology badly needs aparallel scientific discipline with which it can play conceptual leapfrog. Such symbiotic relationship undoubtedly contributes to the cognitive thrust of modern chemistry and physics, and quite probably to some areas in biology. The hypothetico -deductive stratagem of inquiry exposes relationships both within and across such disciplines. The generic syllogism takes the form: Given N facts of Discipline A, what follows in particular for Discipline B, or vice versa? The appearance ofBrain Mechanisms as Volume I in Elsevier's series called Progress in Brain Research provides an occasion for cognitive leapfrog with a behavioral discipline. An international colloquium sponsored by the International Brain Research Organization was held in Pisa in the summer of 1961. The general topic was "Specific and Unspecific Mechanisms of Sensory-Motor Integration." The meeting brought together a distinguished group of contributors, including F. Bremer of Belgium, to whom the present volume is dedicated;J. C. Eccles ofAustralia; R. Granit ofSweden; R. Jung of Germany; and J. M. Brookhart, J. L. O'Leary, and M. A. B. Brazier of the United States representing neurophysiology. The book has been carefully edited as to content and style by the triumvirate of Moruzzi (Italy), Fessard (France), andJasper (Canada). The meat is to be found in its nineteen chapters arranged in a somewhat ascending order from the spinal cord to the cerebral cortex. Eccles presents an authoritative discussion ofpostsynaptic and presynaptic inhibitory actions in the spinal cord. J. L. O'Leary covers the matter of direct current potentials as they arise in the pyramid, in muscle, and in the cortex. Current concepts of sleep mechanisms occupy one section as organized byJ. M. Brookhart. Reference citation tends to be generous throughout. Both author and subject indexes are provided. But especially enriching for the reader are the rather full discussions which accompany the topical contributions. Any student ofthe central nervous system will welcome the knowl136 Book Reviews Perspectives in Biology and Mediente · Autumn 1964 edgeable discussion ofinhibition with which the volume closes. The publishers as well as the contributors merit our thanks for underwriting and producing a workmanlike job. In view ofthe many illustrations, quality ofpaper, binding, etc., the price ofthis volume may be realistic, but it is priced beyond the reach ofmost students entering the field. Apparently this aspect of central inhibition, if considered, was edited out of the closing chapter. But could this be a serendipity? Thereader will gain the impression that some progress has been made over the years in neurophysiology, especially in the quality and range ofinstrumentation. Smaller electric currents can today be measured more accurately and more conveniently than in the day of Sherrington. Some recurrent electrical events can now be detected by in-line computer averaging techniques, but even here the direct correlations with behavior remain obscure. The craft ofneurophysiologyhas indeed made progress. But thethoughtfulreader cannot help wondering about the essentially non-quantitative communications ofthis supposedly scientific discipline. The problem ofvariation tends to be ignored both as to statistical and conceptual restraints. Since the neuronal brain is a primary source ofelectricity, both at rest and under stimulation, it has commanded direct attention. But what ofthe glial brain, the biochemical brain, and the intimately associated vascular brain? Somewhere among these structural domains ofthe nervous system arises a principle ofenergy transformation that, triggered by a few quanta ofradiant energy, makes possible the...

Longitudinal direct-current gradients of spinal nerves.

IN a previous publication1 some evidence was presented for the existence of a steady-state longitudinal charge carrier flow in the peripheral nerves of Amphibia. At that time this flow of current was considered to be unidirectional in the nerves with the necessary circuit completion path through some non-neural tissue. This concept required the presence of measurable longitudinal direct-current potential gradients along the peripheral nerves with a uniform polarity. The return path would then be evidenced by a gradient of opposite polarity in some other tissue. This communication presents the results of an evaluation of this hypothesis.

Direct current potentials in hypnoanalgesia.

Hypnoanalgesia has intrigued and plagued investigators in clinical and experimental hypnosis from the very beginnings of scientific inquiry into the general area of hypnosis. Adequate reviews of the experimental evidence bearing on the validity of the phenomenon have been presented by Weitzenhoffer 12 and Barber. 2 In view of the equivocal results from investigations of hypnoanalgesia and alterations of involuntary physiological correlates of pain, and given the more positive evidence of changes in voluntary function with hypnotic suggestion, Weitzenhoffer has indicated that there is no evidence that the alterations brought about are anything more than functional in nature. Barber, in his development of a theory of pain, has emphasized the role of central psychological, as against peripheral and neurophysiological, factors in the mitigation of discomfort caused by noxious stimuli. He arrives at a formulation in which the salient factor in pain, in terms of

Activation of latent foci of spreading cortical depression in rats.

ArticlesACTIVATION OF LATENT FOCI OF SPREADING CORTICAL DEPRESSION IN RATSJ. Bureš, and O. BurešováJ. Bureš, and O. BurešováPublished Online:01 May 1960https://doi.org/10.1152/jn.1960.23.3.225MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByPersisting Depletion of Brain Glucose following Cortical Spreading Depression, despite Apparent Hyperaemia: Evidence for Risk of an Adverse Effect of Leão's Spreading Depression24 September 2008 | Journal of Cerebral Blood Flow & Metabolism, Vol. 29, No. 1Spreading Depression Can Be Elicited in Brain Stem of Immature But Not Adult RatsFrank Richter, Sven Rupprecht, Alfred Lehmenkühler, and Hans-Georg Schaible1 October 2003 | Journal of Neurophysiology, Vol. 90, No. 4Characterization of Cortical Depolarizations Evoked in Focal Cerebral Ischemia28 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 13, No. 4Influence of Plasma Glucose Concentration on Rat Brain Extracellular Calcium Transients during Spreading Depression29 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 13, No. 1Infarct Rim: Effect of Hyperglycemia on Direct Current Potential and [ 14 C]2-Deoxyglucose Phosphorylation28 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 6, No. 5Cerebral Extracellular Calcium Activity in Severe Hypoglycemia: Relation to Extracellular Potassium and Energy State28 June 2016 | Journal of Cerebral Blood Flow & Metabolism, Vol. 4, No. 2Potassium activity in cerebral cortex in rats during progressive severe hypoglycemiaBrain Research, Vol. 103, No. 2Metabolic responses of the awake cerebral cortex to anoxia hypoxia spreading depression and epileptiform activityBrain Research, Vol. 98, No. 1Facilitation of Leão's spreading depression by a pyrrolopyrimidine derivativeNeuropharmacology, Vol. 14, No. 8Membrane potential of cerebral cortical cells during spreading depression and asphyxiaExperimental Neurology, Vol. 15, No. 4 More from this issue > Volume 23Issue 3May 1960Pages 225-236 https://doi.org/10.1152/jn.1960.23.3.225PubMed13806042History Published online 1 May 1960 Published in print 1 May 1960 Metrics

Stria vascularis as source of endocochlear potential.

Stria vascularis as source of endocochlear potential.

Analysis of Corrosion Conditions Using Cable Sheath Current Measurements

Abstract The technique of current loss analysis using structure to earth potential measurements is wholly in-adequate for use with large cable networks in multiple conduct systems. Duct surveys also have limited application. A newly developed method of making large numbers of sheath current measurements is described. This system is known as the “Zero Resistance Am-meter Method.” When it is employed the potential drop over the test section of cable sheath is observed with a galvanometer which is used to determine the direction of current flow and as a null indicator. In making the measurement a direct current potential of opposite polarity to the potential appearing across two points is applied across two other points under control of resistance and adjusted until the galvanometer indicates a null. At this condition of balance there is no potential drop across the first two points. The current indicated by the ammeter is the current required to produce the zero potential drop and therefore is equal to the ...

Surface resistivity or nonporous ceramic and organic insulating materials at high humidity with observations of associated silver migration

An investigation was made of the behavior of the surface resistivity of a number of ceramic and organic materials during exposure to high relative humidity. Particular emphasis was given to glazed high alumina ceramics from commercial sources. The effects of variables such as contamination, standing direct current potential, firing atmosphere, surface finish and electrodes of different metals were investigated. The uncontaminated specimens of the materials examined can be listed in the order of diminishing surface resistivity as follows: High molecular weight polymers, glazed high alumina ceramics, glasses and glazed ceramics, unglazed ceramics and glass bonded mica. All of the materials are very sensitive to contamination, which tends to reduce them to a nearly common level of surface resistivity. Severe and rapid migration of silver from silver electrodes under the test conditions were observed. Electrodes of solder, tin, copper and platinum showed no discernible migration. The necessity for the development of better means for avoiding contamination and its effects, maintaining high surface resistivity and eliminating silver migration is emphasized by the results of this work.

Broad and Narrow Beam Attenuation of 500- to 1,400-Kv. X-Rays in Lead and Concrete

There have been numerous papers over the past ten years dealing with x-ray protection in the range from 500 to 2,000 kv. (1). The data from these papers vary somewhat because the conditions of the experiments were not always the same and could not readily be correlated. Part of this variance has been attributed to differences in the high-voltage wave form and inherent filtration for the various experimental arrangements. Preliminary data (1) have indicated that the size of the irradiated area of the barrier may also be an important variable. The magnitude and limits for this variable have not, however, been explored quantitatively. The present report will deal with x-ray beams of various sizes produced by direct current potentials of 500, 600, 800, 1,000, and 1,400 kv. with a transmission target. Barriers of lead and concrete will be considered. Concrete has been generally accepted in the energy range above about 500 kv. where space is not important, because it is structurally self-supporting and relatively inexpensive. However, for applications requiring a minimum of thickness for a given protection, lead is still the most popular. In the voltage range under consideration, x-rays are principally absorbed by the photoelectric and the Compton processes, since pair production is still relatively unimportant, even in lead for 1,400 kv. All of the photoelectric absorption and that part of the energy transferred to the Compton electrons are considered to be truly absorbed, since the electrons so produced have small likelihood of producing another x-ray photon. The part of the energy given to the scattered photon leaves the site of the encounter in a different direction from that of the incident photon. The amount of this energy retained by the scattered photon decreases with increase of the angle between the scattered and incident photons. Thus, if the beam is of small cross section, the scattered photons leave the incident bundle and will not be measured. If, however, the beam is of considerable width, the photons scattered from its sides may enter a measuring volume situated near the center of the beam. The apparent attenuation of the beam, measured by the reduction in dosage rate in the barrier, may thus be greatly influenced by the inclusion of this scattered radiation. One may think of the ionization produced in the ionization chamber placed on the far side of a protective barrier as being due to two different sources of radiation. (a) Part of the radiation comes directly from the target of the x-ray tube. (The target is essentially a point source for all practical dimensions used in protective studies.) (b) The remainder of the measured dosage may come from a distributed source composed of the entire irradiated volume of the protective barrier. Several factors serve to limit the volume which acts as this secondary source.

Ovulation studies with direct current potentials

With the Schorr-Lamport millivoltmeter method of registering potential, ovulation could not be determined in the human being.

The Effect of a Direct Current Potential on the Initiation of a Radiofrequency Discharge

The Effect of a Direct Current Potential on the Initiation of a Radiofrequency Discharge

Effect of Direct-Current Potential on Initiation of Radiofrequency Discharge

Effect of Direct-Current Potential on Initiation of Radiofrequency Discharge

A Direct-Current and Audio-Frequency Amplifier

An amplifier suitable for the amplification of small direct-current and low-frequency transient potentials to a usable level is described. In this amplifier two multielement tubes are used as balanced modulators. A carrier voltage is applied in push-pull to two of the grids of these modulators. The plates of these modulator tubes, operating in parallel, are connected to a high-gain amplifier designed for the carrier frequency. Any carrier unbalance appearing in the modulator is amplified to a sufficient level in the carrier-frequency amplifier and applied to a linear detector. The amount of carrier unbalance is determined by the magnitude of the direct-current or low audio-frequency voltage applied to the control grid of one of the modulator tubes. By proper choice of operating conditions a linear relationship between impressed signal voltage and detector output voltage can be obtained. The amplifier is quite stable in its operation and is capable of amplifying signal voltages of the order of a few microvolts.

The Measurement of X-rays with Liquid Ionization Chambers

TWO years ago, we reported2 some preliminary measurements on the ionization produced in liquid carbon disulphide by x-rays. Our interest in the problem lies in its possible application to medical dosage in cases in which we wish to measure the total number of ions produced in tissue-equivalent material. While it is impossible to attain saturation conditions in liquids, as is common with gases, we have shown that the saturation current may be deduced by plotting the reciprocal of the current against the reciprocal of the applied voltage, V, and extrapolating linearly to 1/V = 0. For high fields the plot is nearly linear in accord with Jaffé's theory of columnar ionization (1, 2). However, when a steady direct current potential is applied to a liquid ionization chamber, a barrier potential arising from a space charge or surface layer is built up, which quickly reduces the field in the liquid to roughly 45 per cent of the applied value. This barrier potential reaches an appreciable value in a small fraction of a second but does not attain its maximum magnitude for about ten minutes, during which interval the measured ionization current decreases exponentially. Figure 1 shows the measured ionization current, as a function of the lapse of time for a succession of different potentials applied to the plates of the ionization chamber—with and without x-radiation. It is seen that for each increase in voltage, with x-rays on, the ionization current rises to a high value, then falls off, rapidly at first, to an essentially steady value in about ten minutes. As indicated, this is caused by the building up within the cell of a barrier potential. If, on the other hand, the applied potential be decreased, the ionization current drops abruptly to a low value, then gradually rises again to a considerably higher steady value in about the same ten-minute period. This second sequence results from the partial dissipation of the barrier potential set up by the higher applied voltage and consequently increases the field strength within the liquid. Finally, if the applied potential be removed and the circuit closed, the ionization chamber becomes itself a transient source of current. It is interesting to note, also, how the space charge depends upon other factors associated with the use of a liquid ionization chamber. In Figure 2 the barrier potential is plotted against the potential actually applied to the plates of the chamber. Curves A show that, without x-rays, the barrier potential is proportional to—about 45 per cent of—the applied potential. That is, the barrier potential, in the steady state, makes the field strength within the liquid about half that to be expected from the applied voltage. Curves B show that for a definite applied voltage, the barrier potential decreases with increase in the intensity of the x-rays producing the ionization. Contrary, perhaps, to expectations, this decrease in barrier potential is due to the increased conductivity of the liquid which permits a more rapid dissipation of the space charge.