A Model of Spatial Reach in LFP Recordings
The measurement of local field potentials (LFP), the low-frequency part of extracellularly recorded potentials, is one of the most commonly used methods for probing hippocampal and cortical activity in vivo. It offers the possibility to monitor the activity of many neurons close to the recording electrode simultaneously but has the limitation that it may be difficult to interpret and relate to the underlying neuronal activity. The recording electrode picks up activity from proximal neurons, but what about more distant neurons? An important piece of information for a correct interpretation of the LFP is to decide the size of the tissue that substantially contributes to the LFP, i.e., the reach of the LFP signal. In this chapter we present a simple model that describes how population geometry, spatial decay of single-cell LFP contributions, and correlation between LFP sources determine the relation between LFP amplitude and population size and use it to study the spatial reach of the LFP. The model can also be used to study different frequency bands of the LFP separately as well as the spatial decay outside the active neuronal population.
This work was done with financial support from the Danish Council for Independent Research and FP7 Marie Curie Actions – COFUND (grant id: DFF – 1330-00226), the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 604102 (Human Brain Project, HBP) and grant agreement 269912 (BrainScaleS), the Helmholtz Association through the Helmholtz Portfolio Theme “Supercomputing and Modeling for the Human Brain” (SMHB), Jülich Aachen Research Alliance (JARA), and the Research Council of Norway (NFR, through ISP, NOTUR -NN4661K).
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