Impedance profiles of peripheral and central neurons

1984 ◽  
Vol 62 (4) ◽  
pp. 460-462 ◽  
Author(s):  
Boris Gimbarzevsky ◽  
Robert M. Miura ◽  
Ernest Puil
Keyword(s):  
Transfer Function ◽  
Trigeminal Ganglion ◽  
Transfer Functions ◽  
Ganglion Cells ◽  
Input Current ◽  
Frequency Range ◽  
Ca1 Neurons ◽  
Central Neurons ◽  
Hippocampal Ca1 ◽  
Rc Circuit

The electrical impedance of trigeminal ganglion cells (in vivo) and hippocampal CA1 neurons (in vitro) of guinea pigs was measured in the frequency range of 5–1250 Hz using intracellular recording techniques with single microelectrodes and computerized methodology. The transfer functions of the electrode and the electrode–neuron system were computed from the ratio of fast Fourier transforms of the output voltage response from the neuron and input current composed of sine waves with rapidly increasing frequency which displaced membrane potential by 2–5 mV. We believe these to be the first measurements of complex impedance and transfer functions in peripheral and central neurons of vertebrates and the first use of such input current functions. The majority of trigeminal ganglion cells did not exhibit electrical behaviour ascribable to a simple resistance-capacitance (RC) circuit but showed a hump at low frequencies (5–250 Hz) in the computed transfer function, probably attributable to resonance. The transfer function in less than 20% of the trigeminal neurons could be fitted approximately to a theoretical transfer function (resistance in series with a parallel RC circuit model) providing values for electrode resistance, effective input resistance, and effective input capacitance. The transfer functions measured in hippocampal CA1 neurons were characterized by a rapid fall-off in the low frequency range (<200 Hz). Impedance locus plots approximate the locus corresponding to a series RC circuit in parallel with a parallel RC circuit.

Frequency-Importance and Transfer Functions for Recorded CID W-22 Word Lists

1991 ◽  
Vol 34 (2) ◽  
pp. 427-438 ◽  
Author(s):  
Gerald A. Studebaker ◽  
Robert L. Sherbecoe
Keyword(s):  
Transfer Function ◽  
Word Recognition ◽  
Transfer Functions ◽  
Normal Hearing ◽  
Frequency Range ◽  
Word Test ◽  
Word Lists ◽  
Articulation Index ◽  
Importance Function ◽  
The Right

Frequency-importance and transfer functions for the Technisonic Studios’ recordings of the CID W-22 word test are reported. These functions may be used to calculate Articulation Index (Al) values or to predict scores on the W-22 test. The functions were derived from the word recognition scores of 8 normal-hearing listeners who were tested under 308 conditions of filtering and masking. The importance function for the W-22 test has a broader frequency range and a different shape than the importance function used in the current ANSI standard on the Articulation Index (ANSI, 1969). The transfer function is similar in slope to to the ANSI transfer function for 256 PB-words, but is shifted to the right of that function by 0.05 Al.

Phencyclidine actions measured intracellularly in hippocampal CA1 neurons

1990 ◽  
Vol 68 (10) ◽  
pp. 1351-1356 ◽  
Author(s):  
Peter W. Kujtan ◽  
Peter L. Carlen
Keyword(s):  
Potassium Conductance ◽  
Input Resistance ◽  
Ca1 Neurons ◽  
Postsynaptic Potentials ◽  
Central Neurons ◽  
Hippocampal Ca1 Neurons ◽  
Hippocampal Ca1 ◽  
Potassium Conductances ◽  
Electrophysiological Effects

The electrophysiological effects of phencyclidine (PCP) were measured intracellularly in guinea pig hippocampal CA1 neurons in vitro. At all doses tested (0.2 μM – 10 mM), PCP increased the width of action potentials (APs). Doses of 10 μM and higher were associated with decreased action potential amplitude. PCP decreased inhibitory postsynaptic potentials and excitatory postsynaptic potentials but did not alter responses to focally applied GABA. At the lowest dose (0.2 μM), PCP decreased the input resistance (Rin), while at all other doses Rin was increased. PCP decreased post-spike train afterhyperpolarizations at low and medium doses. PCP effects persisted in low calcium medium and also in medium containing 10−6 M tetrodotoxin. It is concluded that in these central neurons, PCP primarily blocks potassium conductances at all doses and, at anesthetic doses, depresses sodium-dependent spikes.Key words: phencyclidine, potassium conductance, CA1 neurons, electrophysiology.

Frequency domain of renal autoregulation in the conscious dog

1995 ◽  
Vol 269 (3) ◽  
pp. F317-F322 ◽  
Author(s):  
U. Wittmann ◽  
B. Nafz ◽  
H. Ehmke ◽  
H. R. Kirchheim ◽  
P. B. Persson
Keyword(s):  
Blood Flow ◽  
Phase Shift ◽  
Transfer Function ◽  
Arterial Pressure ◽  
Dynamic Range ◽  
Transfer Functions ◽  
Driving Pressure ◽  
Acute Administration ◽  
Frequency Range ◽  
Renal Autoregulation

The dynamic range in which renal blood flow (RBF) autoregulation occurs was determined in eight conscious foxhounds chronically catheterized in the abdominal aorta and implanted with a transit-time flow probe over the renal artery. Sinusoidal driving pressures (amplitude of 10 mmHg) were forced on the renal arterial pressure at different frequencies by a servo-control device, and transfer functions were calculated. Only one frequency range was found below which the gain of the transfer function declined and in which the phase angle increased (n = 8). This indicates the presence of a potent mechanism for renal autoregulation in the examined frequency range between 0.0031 and 0.08 Hz, which buffers changes in blood flow < 0.02 Hz. After furosemide treatment, one indicator for autoregulation (phase shift of transfer function) was significantly blunted at low frequencies (n = 6). Furosemide, however, did not reduce the phase shift to zero, suggesting that some autoregulation still remained in the frequency range between 0.04 and 0.08 Hz. In conclusion, autoregulation of RBF during sinusoidal changes in driving pressure between 0.0031 and 0.02 Hz is mediated by a single mechanism, which can be blocked by the acute administration of furosemide. The residual phase shift between arterial pressure and RBF in the transfer function observed during sinusoidal changes in driving pressure between 0.04 and 0.08 Hz suggests the presence of a second mechanism for RBF autoregulation.

Analytic integration of contrast transfer functions

1988 ◽  
Vol 46 ◽  
pp. 822-823
Author(s):  
Peter Rez
Keyword(s):  
Wave Function ◽  
Transfer Function ◽  
Transfer Functions ◽  
Spherical Aberration ◽  
Continuous Distribution ◽  
Objective Lens ◽  
Direction Parallel ◽  
Scattering Angle ◽  
Analytic Integration ◽  
Image Position

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is1where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by2where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Ischemic preconditioning protects the hippocampal CA1 neurons by inhibiting synaptic activity in rat

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S300-S300
Author(s):  
Thomas J Sick ◽  
Ami P Raval ◽  
Isabel Saul ◽  
Kunjan R Dave ◽  
Raul Busto ◽  
...  
Keyword(s):  
Ischemic Preconditioning ◽  
Synaptic Activity ◽  
Ca1 Neurons ◽  
Hippocampal Ca1 Neurons ◽  
Hippocampal Ca1

Trombone Transfer Functions: Comparison Between Frequency-Swept Sine Wave and Human Performer Input

2012 ◽  
Vol 37 (4) ◽  
pp. 447-454
Author(s):  
James W. Beauchamp
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Cutoff Frequency ◽  
Sine Wave ◽  
Nonlinear Propagation ◽  
Linear Filter ◽  
Wave System ◽  
General Effect ◽  
Filter Characteristic ◽  
High Pass

Abstract Source/filter models have frequently been used to model sound production of the vocal apparatus and musical instruments. Beginning in 1968, in an effort to measure the transfer function (i.e., transmission response or filter characteristic) of a trombone while being played by expert musicians, sound pressure signals from the mouthpiece and the trombone bell output were recorded in an anechoic room and then subjected to harmonic spectrum analysis. Output/input ratios of the signals’ harmonic amplitudes plotted vs. harmonic frequency then became points on the trombone’s transfer function. The first such recordings were made on analog 1/4 inch stereo magnetic tape. In 2000 digital recordings of trombone mouthpiece and anechoic output signals were made that provide a more accurate measurement of the trombone filter characteristic. Results show that the filter is a high-pass type with a cutoff frequency around 1000 Hz. Whereas the characteristic below cutoff is quite stable, above cutoff it is extremely variable, depending on level. In addition, measurements made using a swept-sine-wave system in 1972 verified the high-pass behavior, but they also showed a series of resonances whose minima correspond to the harmonic frequencies which occur under performance conditions. For frequencies below cutoff the two types of measurements corresponded well, but above cutoff there was a considerable difference. The general effect is that output harmonics above cutoff are greater than would be expected from linear filter theory, and this effect becomes stronger as input pressure increases. In the 1990s and early 2000s this nonlinear effect was verified by theory and measurements which showed that nonlinear propagation takes place in the trombone, causing a wave steepening effect at high amplitudes, thus increasing the relative strengths of the upper harmonics.

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