Theory of current source-density analysis and determination of conductivity tensor for anuran cerebellum

1975 ◽  
Vol 38 (2) ◽  
pp. 356-368 ◽  
Author(s):  
C. Nicholson ◽  
J. A. Freeman
Keyword(s):  
Current Source ◽  
Field Potential ◽  
Mathematical Expression ◽  
Current Source Density ◽  
Conductivity Tensor ◽  
Spatial Gradients ◽  
Source Density ◽  
Principal Axes ◽  
Spatial Dimensions ◽  
Minimum Number

The theoretical basis of current source-density (CSD) analysis in the central nervous system is described. Equations relating CSD, the current flow vector, and the extracellular field potential are given. It is shown that the CSD provides superior resolution of neuronal events when compared to conventional field-potential analysis. Expressions for the CSD in rectangular Cartesian coordinates are derived, including the general case of anisotropic, inhomogeneous conductive tissue, and a coordinate system rotated with respect to the principal axes (APPENDIX). The minimum number of spatial dimensions for accurate CSD analysis is discussed. The conductivity tensor was experimentally measured in frog and toad cerebella. All three principal components of the tensor were evaluated and their spatial gradients determined to be negligible. It was also shown that the conductivity was independent of potential. Thus the anuran cerebellum is anisotropic, homogeneous, and ohmic. On the basis of these results the appropriate mathematical expression for the CSD was selected.

scholarly journals Non-homogeneous extracellular resistivity affects the current-source density profiles of up–down state oscillations

2011 ◽  
Vol 369 (1952) ◽  
pp. 3802-3819 ◽  
Author(s):  
Maxim Bazhenov ◽  
Peter Lonjers ◽  
Steven Skorheim ◽  
Claude Bedard ◽  
Alain Destexhe
Keyword(s):  
Current Source ◽  
Field Potential ◽  
Current Source Density ◽  
Frequency Filtering ◽  
Extracellular Medium ◽  
Opposite Pattern ◽  
Source Density ◽  
Deep Layers ◽  
Up And Down States ◽  
Inhomogeneous Conductivity

Rhythmic local field potential (LFP) oscillations observed during deep sleep are the result of synchronized electrical activities of large neuronal ensembles, which consist of alternating periods of activity and silence, termed ‘up’ and ‘down’ states, respectively. Current-source density (CSD) analysis indicates that the up states of these slow oscillations are associated with current sources in superficial cortical layers and sinks in deep layers, while the down states display the opposite pattern of source–sink distribution. We show here that a network model of up and down states displays this CSD profile only if a frequency-filtering extracellular medium is assumed. When frequency filtering was modelled as inhomogeneous conductivity, this simple model had considerably more power in slow frequencies, resulting in significant differences in LFP and CSD profiles compared with the constant-resistivity model. These results suggest that the frequency-filtering properties of extracellular media may have important consequences for the interpretation of the results of CSD analysis.

Experimental optimization of current source-density technique for anuran cerebellum

1975 ◽  
Vol 38 (2) ◽  
pp. 369-382 ◽  
Author(s):  
J. A. Freeman ◽  
C. Nicholson
Keyword(s):  
Current Source ◽  
Field Potential ◽  
Spatial Differentiation ◽  
Relative Magnitude ◽  
Current Source Density ◽  
Source Density ◽  
Tip Position ◽  
Vestibulocerebellar Input ◽  
Differentiation Formulas ◽  
Optimum Application

This paper represents a systematic, semirigorous attempt to optimize the technique of current source-density (CSD) analysis experimentally. We compared different spatial differentiation formulas in terms of accuracy, aliasing, and smoothing, and provide experimental and theoretical rationale for their use. Sources of error have also been investigated. Expressions were derived to enable one to estimate the relative magnitude of errors due to electrical noise, uncertainty in tip position of recording electrodes, and error in the conductivity tensor. Corresponding experiments illlustrating the validity of such estimates are also presented. Methods to determine the optimum interelectrode spacing are given, based on computations of spatial energy-density spectra in the anuran cerebellum. The application of the technique of CSD analysis developed in this, and the accompanying paper, to the vestibulocerebellar input in the toad cerebellum provided significantly better temporal and spatial resolution of neuronal events than conventional field-potential analysis. Considerations germane to the optimum application of this technique to other neural structures are also discussed.

Analysis of synaptic events in the opossum piriform cortex with improved current source-density techniques

1989 ◽  
Vol 61 (4) ◽  
pp. 702-718 ◽  
Author(s):  
R. Rodriguez ◽  
L. B. Haberly
Keyword(s):  
Piriform Cortex ◽  
Current Source ◽  
Field Potential ◽  
Pyramidal Cells ◽  
Superficial Layer ◽  
Current Source Density ◽  
Membrane Currents ◽  
Source Density ◽  
Potential Component ◽  
Association Fibers

1. The piriform cortex of the opossum was studied by current source-density (CSD) analysis of field potentials to determine the laminar and temporal distribution of synaptic currents evoked by lateral olfactory tract (LOT) stimulation. 2. Extracellular conductivity was measured as a function of depth at high resolution and incorporated into CSD computations. Inclusion of the conductivity term resulted in relatively subtle changes in the shapes of CSD profiles. Resolution and accuracy of CSD computations was further improved by use of a new smoothing approach and averaging of multiple potential profiles obtained at the same site. 3. The CSD depth profile resulting from LOT stimulation revealed six major synaptic events that were consistently present at anterior, middle, and posterior sites: one during the first (A1) peak of the initial surface negative dichrotic field potential component, three during the second (B1) peak, one during the surface positive field potential component (period 2), and one during the second surface negative component (period 3). In addition, CSD profiles were computed for the population spike generated by synchronous discharge of action potentials. Depths of the net inward and outward membrane currents underlying these events were correlated with the cortical lamination as determined histologically by placement of small dye marks. 4. In agreement with previous reports it is concluded that the large inward membrane current in layer Ia during the A1 wave underlies a monosynaptic EPSP evoked in distal apical dendritic segments of pyramidal cells by afferent fibers. This EPSP displays a marked paired shock facilitation. 5. Based on anatomic and physiological considerations it is concluded that the three spatially and temporally distinct inward membrane currents (sinks) that were observed in layers III, superficial Ib, and mid- to deep-Ib during the B1 wave, underlie disynaptic EPSPs resulting from direct synaptic interactions between pyramidal cells. It is postulated that the layer III sink is generated in basal dendrites largely via local axon collaterals, the superficial layer Ib sink in intermediate apical dendritic segments by association fibers originating in the anterior piriform cortex, and the deep Ib sink in proximal apical segments by association fibers originating largely in the posterior piriform cortex. 6. The latencies of the layer Ia and superficial layer Ib sinks (presumed mono- and large disynaptic EPSPs, respectively) increased from anterior to posterior. Amplitude of the superficial Ib sink relative to the Ia sink increased from anterior to posterior.(ABSTRACT TRUNCATED AT 400 WORDS)

Converging Inputs to the Entorhinal Cortex From the Piriform Cortex and Medial Septum: Facilitation and Current Source Density Analysis

1997 ◽  
Vol 78 (5) ◽  
pp. 2602-2615 ◽  
Author(s):  
C. Andrew Chapman ◽  
Ronald J. Racine
Keyword(s):  
Entorhinal Cortex ◽  
Piriform Cortex ◽  
Current Source ◽  
Field Potential ◽  
Medial Septum ◽  
Current Source Density ◽  
Short Term ◽  
Source Density ◽  
Potential Component ◽  
Stimulation Of

Chapman, C. Andrew and Ronald J. Racine. Converging inputs to the entorhinal cortex from the piriform cortex and medial septum: facilitation and current source density analysis. J. Neurophysiol. 78: 2602–2615, 1997. The entorhinal cortex receives sensory inputs from the piriform cortex and modulatory inputs from the medial septum. To examine short-term synaptic facilitation effects in these pathways, current source density (CSD) analysis was used first to localize the entorhinal cortex membrane currents, which generate field potentials evoked by stimulation of these afferents. Field potentials were recorded at 50-μm intervals through the medial entorhinal cortex in urethan-anesthetized rats and the one-dimensional CSD was calculated. Piriform cortex stimulation evoked a surface-negative, deep-positive field potential component in the entorhinal cortex with mean onset and peak latencies of 10.4 and 18.4 ms. The component followed brief 100-Hz stimulation, consistent with a monosynaptic response. CSD analysis linked the component to a current sink, which often began in layer I before peaking in layer II. A later, surface-positive field potential component peaked at latencies near 45 ms and was associated with a current source in layer II. Medial septal stimulation evoked positive and negative field potential components which peaked at latencies near 7 and 16 ms, respectively. A weaker and more prolonged surface-negative, deep-positive component peaked at latencies near 25 ms. The early components were generated by currents in the hippocampal formation, and the late surface-negative component was generated by currents in layers II to IV of the entorhinal cortex. Short-term facilitation effects in conscious animals were examined using electrodes chronically implanted near layer II of the entorhinal cortex. Paired-pulse stimulation of the piriform cortex at interpulse intervals of 30 and 40 ms caused the largest facilitation (248%) of responses evoked by the second pulse. Responses evoked by medial septal stimulation also were facilitated maximally (59%) by a piriform cortex conditioning pulse delivered 30–40 ms earlier. Paired pulse stimulation of the medial septum caused the largest facilitation (149%) at intervals of 70 ms, but piriform cortex evoked responses were facilitated maximally (46%) by a septal conditioning pulse 100–200 ms earlier. Frequency potentiation effects were maximal during 12- to 18-Hz stimulation of either the piriform cortex or medial septum. Occlusion tests suggested that piriform cortex and medial septal efferents activate the same neurons. The CSD analysis results show that evoked field potential methods can be used effectively in chronically prepared animals to examine synaptic responses in the converging inputs from the piriform cortex and medial septum to the entorhinal cortex. The short-term potentiation phenomena observed here suggest that low-frequency activity in these pathways during endogenous oscillatory states may enhance entorhinal cortex responsivity to olfactory inputs.

Current-Source Density Analysis in the Rat Olfactory Bulb: Laminar Distribution of Kainate/AMPA- and NMDA-Receptor-Mediated Currents

1999 ◽  
Vol 81 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Vassiliki Aroniadou-Anderjaska ◽  
Matthew Ennis ◽  
Michael T. Shipley
Keyword(s):  
Nmda Receptor ◽  
Olfactory Bulb ◽  
Granule Cell ◽  
Granule Cells ◽  
Current Source ◽  
Field Potential ◽  
Current Source Density ◽  
Source Density ◽  
Tufted Cells ◽  
Apical Dendrites

Aroniadou-Anderjaska, Vassiliki, Matthew Ennis, and Michael T. Shipley. Current-source density analysis in the rat olfactory bulb: laminar distribution of kainate/AMPA- and NMDA-receptor-mediated currents. J. Neurophysiol. 81: 15–28, 1999. The one-dimensional current-source density method was used to analyze laminar field potential profiles evoked in rat olfactory bulb slices by stimulation in the olfactory nerve (ON) layer or mitral cell layer (MCL) and to identify the field potential generators and the characteristics of synaptic activity in this network. Single pulses to the ON evoked a prolonged (≥400 ms) sink (S1ON) in the glomerular layer (GL) with corresponding sources in the external plexiform layer (EPL) and MCL and a relatively brief sink (S2ON) in the EPL, reversing in the internal plexiform and granule cell layers. These sink/source distributions suggested that S1ON and S2ON were generated in the apical dendrites of mitral/tufted cells and granule cells, respectively. The kainate/AMPA-receptor antagonist CNQX (10 μM) reduced the early phase of S1ON, blocked S2ON, and revealed a low amplitude, prolonged sink at the location of S2ON in the EPL. Reduction of Mg2+, in CNQX, enhanced both the CNQX-resistant component of S1ON and the EPL sink. This EPL sink reversed below the MCL, suggesting it was produced in granule cells. The NMDA-receptor antagonist APV (50 μM) reversibly blocked the CNQX-resistant field potentials in all layers. Single pulses were applied to the MCL to antidromically depolarize the dendrites of mitral/tufted cells. In addition to synaptic currents of granule cells, a low-amplitude, prolonged sink (S1mcl) was evoked in the GL. Corresponding sources were in the EPL, suggesting that S1mcl was generated in the glomerular dendritic tufts of mitral/tufted cells. Both S1mcl and the granule cell currents were nearly blocked by CNQX (10 μM) but enhanced by subsequent reduction of Mg2+; these currents were blocked by APV. S1mcl also was enhanced by γ-aminobutyric acid-A-receptor antagonists applied to standard medium; this enhancement was reduced by APV. ON activation produces prolonged excitation in the apical dendrites of mitral/tufted cells, via kainate/AMPA and NMDA receptors, providing the opportunity for modulation and integration of sensory information at the first level of synaptic processing in the olfactory system. Granule cells respond to input from the lateral dendrites of mitral/tufted cells via both kainate/AMPA and NMDA receptors; however, in physiological concentrations of extracellular Mg2+, NMDA-receptor activation does not contribute significantly to the granule cell responses. The glomerular sink evoked by antidromic depolarization of mitral/tufted cell dendrites suggests that glutamate released from the apical dendrites of mitral/tufted cells may excite the same or neighboring mitral/tufted cell dendrites.

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