Review

The action potential of the squid giant axon is formed by just two voltage-dependent conductances in the cell membrane, yet mammalian central neurons typically express more than a dozen different types of voltage-dependent ion channels. This rich repertoire of channels allows neurons to encode information by generating action potentials with a wide range of shapes, frequencies and patterns. Recent work offers an increasingly detailed understanding of how the expression of particular channel types underlies the remarkably diverse firing behaviour of various types of neurons.

Times Cited: 1 Article English Murnane, O. D James H Quillen VA, Med Ctr, Dept Audiol 126, Mt Home, TN 37684 USA Cited References Count: 28 132RU PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS AMSTERDAM

Times Cited: 2 Article English Paolini, A. G La Trobe Univ, Sch Psychol Sci, Bundoora, Vic 3086, Australia Cited References Count: 44 855DY 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA BETHESDA

Times Cited: 0 Article English Briaire, J. J Leiden Univ, Ctr Med, ENT Dept, POB 9600, NL-2300 RC Leiden, Netherlands Cited References Count: 36 941UJ PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS AMSTERDAM

Times Cited: 480 Article English Cited References Count: 68 KG659 11 DUPONT CIRCLE, NW, STE 500, WASHINGTON, DC 20036 WASHINGTON

Although extracellular unit recording is typically used for the detection of spike occurrences, it also has the theoretical ability to report about what are typically considered intracellular features of the action potential. We address this theoretical ability by developing a model system that captures features of experimentally recorded simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons. We use the Line Source Approximation method (Holt and Koch 1999) to model the extracellular action potential (EAP) voltage resulting from the spiking activity of individual neurons. We compare the simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons recorded in vivo (Henze et al. 2000) with model predictions for the same cells reconstructed and simulated with compartmental models. The model accurately reproduces both the waveform and the amplitude of the EAP's, although it was difficult to achieve simultaneous good matches on both the intracellular and extracellular waveforms. This suggests that accounting for the EAP waveform provides a considerable constraint on the overall model. The developed model explains how and why the waveform varies with electrode position relative to the recorded cell. Interestingly, each cell's dendritic morphology had very little impact on the EAP waveform. The model also demonstrates that the varied composition of ionic currents in different cells is reflected in the features of the EAP.