Forward modeling of extracellular potentials: Results and possibilities
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1
Norwegian University of Life Sciences, Norway
Mathematical modelling relies on experimental data to make progress, both to constrain and to test the models. A common experimental method has been in vivo single-unit extracellular recordings: when a sharp electrode is placed sufficiently close to the soma of a particular neuron, the recorded potential reliably measures the firing of individual action potentials in this neuron. This information is contained in the high-frequency part of the recorded potentials. The low-frequency part, that is, the local field potentials (LFP), has proved much more difficult to interpret and has typically been discarded.
Other experimental methods, particularly methods that measure population-level activity in vivo, are needed to facilitate development of biologically relevant neural network models. Large-scale electrical recordings using various types of multielectrodes, i.e., electrodes with many contacts, are one such option. As techniques for such recordings are rapidly improving, there is a need for new methods for extraction of relevant information from such data. Here we present results from projects in our group aimed at elucidating the link between recorded extracellular potentials and the underlying neural activity.
Extracellular potentials in the brain are in general due to complicated weighted sums of contributions from transmembrane currents in the vicinity of the recording electrode. The transmembrane currents accompanying various types of neural activity can be calculated by means of multicompartment models. Given these transmembrane currents, the extracellular potential can in turn be calculated using a electrostatic forward-modelling formula based on the quasistatic version of Maxwell’s equations (Holt & Koch, J Comp Neurosci 6:169, 1999) . Several projects where this forward-modelling scheme has been utilized will be presented: - investigation of how neural morphology and electrical parameters affect the shape and size of extracellular action potentials (Pettersen & Einevoll, Biophys J 94:784, 2008)
- investigation of how the LFP and its frequency content generated by neurons in a population depend on synaptic activity and neuronal morphologies (Pettersen et al, J Comp Neurosci 24:291,2008; Pettersen et al, J Neurosci Meth 154:116, 2006) - introduction of laminar population analysis (LPA) where stimulus-evoked laminar-electrode data from rat barrel cortex are analyzed in a scheme where the MUA and LFP are jointly modelled using physiological constraints (Einevoll et al, J Neurophysiol 97:2174, 2007)
- extraction of thalamocortical and intracortical network models based on laminar-electrode data from barrel cortex and simultaneous recording of thalamic firing activity recorded in the homologous barreloid (Blomquist et al, PLoS Comp Biol 5:e1000328, 2009)
- generation of model data aimed at facilitating the development and objective testing of spike-sorting algorithms for data recorded by multielectrodes
- investigation of the extracellular-potential footprint from synaptic activation of primary sensory cortices from individual thalamic neurons as measured by the so called spike-triggered CSD method (Swadlow et al, J Neurosci 22:7766, 2002)
Supported by the Research Council of Norway (eVita,NOTUR,NevroNor)
Conference:
Neuroinformatics 2010 , Kobe, Japan, 30 Aug - 1 Sep, 2010.
Presentation Type:
Poster Presentation
Topic:
Computational Neuroscience
Citation:
Einevoll
GT,
Linden
H,
Hagen
E,
Fossum
J,
Tetzlaff
T,
Norheim
E and
Pettersen
KH
(2010). Forward modeling of extracellular potentials: Results and possibilities.
Front. Neurosci.
Conference Abstract:
Neuroinformatics 2010 .
doi: 10.3389/conf.fnins.2010.13.00081
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Received:
14 Jun 2010;
Published Online:
14 Jun 2010.
*
Correspondence:
Gaute T Einevoll, Norwegian University of Life Sciences, Aas, Norway, Gaute.Einevoll@nmbu.no