Mathematical medeling of extracellular potentials in the brain: results and possibilities
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 contacts. However, with morphologically reconstructed neurons a straightforward computational scheme can be used to calculate the extracellular potential generated by a single neuron at any point in space, and due to the linearity of the electrostatic equations, the scheme directly generalizes to extracellular potentials generated by populations of neurons. 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 (Pettersen and Einevoll 2008), (B) the frequency spectra and spatial range of the local field potential (LFP; Linden et al. 2010), 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 (Pettersen et al. 2008). Next, examples of developments aided by this scheme of new analysis methods for data from multielectrode recordings such as laminar population analysis (LPA; Einvoll et al. 2007), and population firing-rate model extraction (Blomquist et al. 2009), will be briefly presented. Finally, example results from a project involving generation of test data to stimulate and aid the development and testing of automated spike-sorting algorithms for tetrode data will be shown and discussed.
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