Non-homogeneous extracellular resistivity
affects the current-source density profiles of
Up/Down state oscillations
Maxim Bazhenov, Peter Lonjers, Steven Skorheim, Claude Bedard
and Alain Destexhe
Phil. Trans. Roy. Soc. A 369: 3802-3819, 2011.
Rhythmic local field potential (LFP) oscillations observed during
deep sleep are the result of synchronized electrical activities of
large neuronal ensembles, which consist of alternating periods of
activity and silences, termed "up" and "down" states, respectively.
Current-source density (CSD) analysis indicates that the up states
of these slow oscillations are associated with current sources in
superficial cortical layers and sinks in deep layers, while the down
states display the opposite pattern of source-sink distribution. We
show here that a network model of up and down states displays this
CSD profile only if a frequency-filtering extracellular medium is
assumed. When frequency filtering was modelled as inhomogeneous
conductivity, this simple model had considerably more power in
slow frequencies, resulting in significant differences in LFP and CSD
profiles compared with the constant-resistivity model. These
results suggest that the frequency filtering properties of
extracellular media may have important consequences for the
interpretation of the results of CSD analysis.
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