Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Electrical conductivity of the hippocampal CA1 layers and application to current-source-density analysis

Summary

The microstructure of the layers in the hippocampal CA1 area suggests that differences may exist between the electrical conductivities of these layers. In order to quantify these differences a sinusoidal current was applied to hippocampal slices in a bathing medium and potential differences were measured between pairs of neighbouring electrodes from an array. The maximum relative conductivity (100%) was found in the middle part of str. radiatum, with a gradual decrease towards the fissure (84%). There was also a gradual decrease towards the alveus (70%), but in str. pyramidale the relative conductivity was only 42%. No differences were observed between the laminar conductivities of normal hippocampal slices and slices generating spontaneous interictal bursts. These results were used to carry out a one-dimensional CSD analysis of field potentials evoked by Schaffer collateral stimulation. Despite the differences in conductivity, the homogeneous and the inhomogeneous CSD approximations did not lead to differences in the spatial distribution of sources and sinks and only gave some differences in the current density, especially at the pyramidal layer and its close environment.

This is a preview of subscription content, log in to check access.

References

  1. Andersen P, Bliss TYP, Skrede KK (1971) Unit analysis of hippocampal population spikes. Exp Brain Res 13: 208–221

  2. Bingmann D, Kolde G (1982) PO2-profiles in hippocampal slices of the guinea pig. Exp Brain Res 48: 89–96

  3. Dietzel I, Heinemann U, Hofmeier C, Lux HD (1980) Transient changes in the size of the extracellular space in the sensorimotor cortex of cats in relation to stimulus-induced changes in potassium concentration. Exp Brain Res 40: 432–439

  4. Fisher RS, Pedley TA, Moody WJ, Prince DA (1976) The role of extracellular potassium in hippocampal epilepsy. Arch Neurol 33: 76–83

  5. Freeman JA, Stone J (1969) A technique for current density analysis of field potentials and its application to the frog cerebellum. In: Llinás R (ed) Neurobiology of cerebellar evolution and development. Am Med Assoc, Chicago, pp 421–430

  6. Gardner-Medwin AR (1980) Membrane transport and solute migration affecting the brain cell microenvironment. Neurosci Res Progr Bull 18: 208–226

  7. Geddes LA, Baker LE (1967) The specific resistance of biological material —a compendium of data for the biomedical engineer and physiologist. Med Biol Eng 5: 271–293

  8. Haberly LB, Shepherd GM (1973) Current-density analysis of summed evoked potentials in opossum prepyriform cortex. J Neurophysiol 36: 789–802

  9. Hoeltzell PB, Dykes RW (1979) Conductivity in the somatosensory cortex of the cat —evidence for cortical anisotropy. Brain Res 177: 61–82

  10. Kwan HC, Murphy JT (1974) A basis for extracellular current density analysis in cerebellar cortex. J Neurophysiol 37: 170–180

  11. Lang J, Sances A, Larson SJ (1969) Determination of specific cerebral impedance and cerebral current density during the application of diffuse electrical currents. Med Biol Eng 7: 517–526

  12. Leung LS (1979) Orthodromic activation of hippocampal CA1 region of the rat. Brain Res 176: 49–63

  13. Mitzdorf U (1985) Current source-density method and application in cat cerebral cortex: investigation of evoked potentials and EEG phenomena. Physiol Rev 65: 37–100

  14. Mitzdorf U, Singer W (1978) Prominent excitatory pathways in the cat visual cortex (A17 and A18): a current source density analysis of electrically evoked potentials. Exp Brain Res 33: 371–394

  15. Nicholson Ch, Freeman JA (1975) Theory of current source density analysis and determination of conductivity tensor for anuran cerebellum. J Neurophysiol 38: 356–368

  16. Rappelsberger P, Pockberger H, Petsche H (1981) Current source density analysis: methods and application to simultaneously recorded field potentials of the rabbit's visual cortex. Pflügers Arch 389: 159–170

  17. Schwartzkroin PA, Prince DA (1978) Cellular and field potential properties of epileptogenic hippocampal slices. Brain Res 147: 117–130

  18. Verloop AJ, Holsheimer J (1984) A simple method for the construction of electrode arrays. J Neurosci Methods 11: 173–178

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Holsheimer, J. Electrical conductivity of the hippocampal CA1 layers and application to current-source-density analysis. Exp Brain Res 67, 402–410 (1987). https://doi.org/10.1007/BF00248560

Download citation

Key words

  • Hippocampus
  • CA1 area
  • Laminar conductivity
  • Current source density
  • In vitro hippocampal slice