Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2003 Dec 15;553(Pt 3):975-85.
doi: 10.1113/jphysiol.2003.051144. Epub 2003 Oct 3.

Contribution of ionic currents to magnetoencephalography (MEG) and electroencephalography (EEG) signals generated by guinea-pig CA3 slices

Affiliations

Contribution of ionic currents to magnetoencephalography (MEG) and electroencephalography (EEG) signals generated by guinea-pig CA3 slices

Shingo Murakami et al. J Physiol. .

Abstract

A mathematical model was used to analyse the contributions of different types of ionic currents in the pyramidal cells of longitudinal CA3 slices to the magnetic fields and field potentials generated by this preparation. Murakami et al. recently showed that a model based on the work of Traub et al. provides a quantitatively accurate account of the basic features of three types of empirical data (magnetic fields outside the slice, extracellular field potentials within the slice and intracellular potentials within the pyramidal neurons) elicited by stimulations of the soma and apical dendrites. This model was used in the present study to compute the net current dipole moment (Q) due to each of the different voltage- and ligand-gated channels in the cells in the presence of fast GABAA inhibition. These values of Q are proportional to the magnetic field and electrical potential far away from the slice. The intrinsic conductances were found to be more important than the synaptic conductances in determining the shape and magnitude of Q. Among the intrinsic conductances, the sodium (gNa) and delayed-rectifier potassium (gK(DR)) channels were found to produce sharp spikes. The high-threshold calcium channel (gCa) and C-type potassium channel (gK(C)) primarily determined the overall current waveforms. The roles of gCa and gK(C) were independent of small perturbations in these channel densities in the apical and basal dendrites. A combination of gNa, gK(DR), gCa, and gK(C) accounted for most of the evoked responses, except for later slow components, which were primarily due to synaptic channels.

PubMed Disclaimer

Figures

Figure 1
Figure 1. A CA3 model modified from the 1991 model developed by Traub et al. (1991)
A, geometry of the longitudinal hippocampal CA3 slice represented in the model. Pyramidal cells are arranged parallel to each other with their cell bodies along the cell layer and their longitudinal axis along the orthogonal direction, with basal dendrites in the striatum oriens (STR. ORIENS) and apical dendrites in the striatum radiatum (STR. RADIATUM). An array of bipolar electrodes (STIM ELEC) with an intra-pair distance of 400 μm are placed along the cell layer with a spacing of about 800 μm between pairs of electrodes. B, CA3 model of the present study. E-cells, representing the pyramidal cells in CA3, are arranged in a square array of 10 × 10 cells, spaced 20 μm apart. Twenty I-cells are arranged in a 2 × 10 grid. A bipolar stimulating electrode (STIM) is placed in columns (COL) 1–3. C, a multicompartment, equivalent single-cylinder representation of E-cells together with the distribution of channel densities of the active conductances. D, a similar model for the I-cells. E, weighting function used to represent effects of dendritic branching on the current dipole moment Q.
Figure 2
Figure 2. Dipolar current waveforms (Q values) produced by intrinsic (non-synaptic, left) and synaptic (right) channels of the excitatory E-cells in the model slice
Continuous curves in row 1: Qy produced by somatic stimulus (sti.). Continuous curves in row 2: Qy produced by apical stimulus. Dotted curves: Qy produced by the sum of all channel types.
Figure 3
Figure 3. Dipolar current waveforms (Q values) produced by all of the E-cells in the model slice (Qtotal, left), by the population of E-cells directly activated by the stimulus (Qdirect, centre), and by the population of synaptically activated E-cells (Qsynapse, right)
Row 1, Qy produced by the sum of all channel types. Rows 2–7, Q values produced by gNa, gK(DR), gCa, gK(C), gK(A) and gK(AHP), respectively.
Figure 4
Figure 4
Same as Fig. 3 for the apical stimulation condition
Figure 5
Figure 5. Relative contributions of the currents produced by the different channel types to the aggregate population current dipole moment (Q) in the somatic stimulation condition
Relative contributions of the currents produced by the different channel types to the aggregate population Q value in the somatic stimulation condition, shown separately for the Qtotal produced by the entire model slice (left), Qdirect produced by the population of E-cells directly activated by the stimulus (centre) and Qsynapse produced by the population of synaptically activated E-cells (right). In each case, the Q due to the sum of all channel types is shown by a dashed curve in each row. The continuous curves in rows 1–6 show the Q values produced by the sum of Na and K(DR) channels (row 1), the sum of the Ca and K(C) pair (row 2), the Na + K(DR) + Ca + K(C) channels (row 3), addition of the current generated by the A-channel (row 4), addition of the current generated by the K(AHP) channel (row 5) and by the addition of the synaptically mediated current (row 6).
Figure 6
Figure 6
Same as Fig. 5 for the apical stimulation condition
Figure 7
Figure 7. The Q generated by the sum of calcium and C-type potassium channels in the somatic and apical stimulation condition
The Q generated by the sum of calcium and C-type potassium channels in the somatic and apical stimulation condition, shown separately for the Q produced by basal dendrites (compartments 1–7; left), the perisomatic region (compartments 8–10; centre) and by the apical dendrites (compartments 11–19; right). In each case, the Q due to the sum of all regions is shown by a dashed curve. Row 1, somatic stimulus condition. Row 2, apical stimulus condition.
Figure 8
Figure 8. The Q generated by the sum of calcium and C-type potassium channels in the somatic (row 1) and apical (row 2) stimulation condition
The Q generated by the sum of calcium and C-type potassium channels in the somatic (row 1) and apical (row 2) stimulation condition, shown separately for (a) change in gCa density to 0.9 of that of the original in apical dendrites (continuous line) and basal dendrites (dashed line), (b) original gCa density and (c) change in the gCa density to 1.1 of that of the original in apical dendrites (continuous line) and in the basal dendrites (dashed line).
Figure 9
Figure 9
Same as Fig. 8 but for changes in the gK(C) density distribution

Similar articles

Cited by

References

    1. Barr RC, Pilkington TC, Boineau JP, Spach MS. Determining surface potentials from current dipoles, with application to electrocardiography. IEEE Trans Biomed Eng. 1966;13:88–92. - PubMed
    1. Geselowitz DB. On bioelectric potentials in an inhomogeneous volume conductor. Biophys J. 1967;7:1–11. - PMC - PubMed
    1. Geselowitz DB. On the magnetic field generated outside an in homogeneous volume conductor by internal current sources. IEEE Trans Magn. 1970;6:346–347.
    1. Hille B. Ionic Channels of Excitable Membranes. Sunderland Mass: Blackwell Science Inc; 2001.
    1. Johnston D, Magee JC, Colbert CM, Cristie BR. Active properties of neuronal dendrites. Annu Rev Neurosci. 1996;19:165–186. - PubMed

Publication types

LinkOut - more resources