What can we learn from extracellular potentials recorded in the brain?

Abstract:

While extracellular electrical recordings have been the work horse in electrophysiology, the interpretation of such recordings is not trivial. In general, the recorded potentials stem from a weighted sum of contributions from all transmembrane currents in all active neurons in the vicinity of the electrode contact [1]. However, with morphologically reconstructed neurons a straightforward computational scheme can be used to calculate the extracellular potential from a single neuron at any point in space [2-4], and due to the linearity of the electrostatic equations, the scheme directly generalizes to extracellular potentials generated by populations of neurons [5]. In this two-step computational scheme, morphologically reconstructed neurons are first simulated with compartmental modeling using a simulation program such as NEURON to provide transmembrane currents, and then the extracellular potentials are calculated based on these [2-5].

In the talk I will briefly discuss some results from our group where this scheme has been used to illuminate (A) frequency filtering and size variation of extracellular signatures of action potentials [3], (B) the frequency spectra and spatial range of the local field potential (LFP) [4], and (C) the relationship between the LFP and multi-unit activity (MUA) with the underlying neural activity in an activated columnar population of pyramidal neurons [5]. Next, examples of developments aided by this scheme of new analysis methods for data from multielectrode recordings such as iCSD [6], laminar population analysis (LPA) [7], and population firing-rate model extraction [8], will be briefly presented.

[1] C Nicholson and JA Freeman, J Neurophsyiol 38:356 (1975)
[2] G Holt, C Koch, J Comp Neurosci 6:169 (1999)
[3] KH Pettersen, GT Einevoll, Biophys J 94:784 (2008)
[4] H Linden et al, J Comp Neurosci (2010)
[5] KH Pettersen et al, J Comp Neurosci 24:291 (2008)
[6] KH Pettersen et al, J Neurosci Meth 154:116 (2006)
[7] GT Einevoll et al, J Neurophysiol 97:2174 (2007)
[8] P Blomquist et al, PLoS Comp Biol 5:e1000328 (2009)
 
back