Evidence for frequency-dependent extracellular impedance from the transfer function between extracellular and intracellular potentials

Bédard, Claude; Rodrigues, Serafim; Roy, Noah; Contreras, Diego; Destexhe, Alain

doi:10.1007/s10827-010-0250-7

Cited by 58 publications

(63 citation statements)

References 33 publications

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“…This work provides the first direct experimental proof of effects related to these microscale inhomogeneities, as we show that electrically as well as physically, extracellular space in the brain indeed is not homogenous. Our results are in general agreement with those of Bédard et al (2004) in that we find that inhomogeneity of the extracellular space leads to additional filtering and amplitude attenuation of the extracellular signal, though here we do not address the issue of the frequency dependence of extracellular signal propagation.…”

Section: Discussionsupporting

confidence: 91%

“…Typically this has been modeled as electrically homogenous (Gold et al, 2006;Nunez and Srinivasan, 2006;Lindén et al, 2011), although the effect of the inhomogeneity of the extracellular space has been considered by some (Bédard et al, 2004;Bazhenov et al, 2011). This work provides the first direct experimental proof of effects related to these microscale inhomogeneities, as we show that electrically as well as physically, extracellular space in the brain indeed is not homogenous.…”

Section: Discussionmentioning

confidence: 99%

“…Other issues are also presently under debate and topics of current research. Such issues include the frequency dependence of signal propagation in the extracellular space (Bédard et al, 2004;Logothetis et al, 2007;Bédard and Destexhe, 2009), the overall relation between the extracellular voltage and intracellular events (Trevelyan, 2009;Bédard et al, 2010;Lindén et al, 2010), the degree of physical spread of LFPs from their neural sources (Katzner et al, 2009;Xing et al, 2009;Kajikawa and Schroeder, 2011;Lindén et al, 2011), and the role of electrode properties in measuring LFPs (Nunez andSrinivasan, 2006, Kay andLazzara, 2010;Nelson andPouget, 2010, 2012).…”

Section: Discussionmentioning

confidence: 99%

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Microscale Inhomogeneity of Brain Tissue Distorts Electrical Signal Propagation

et al. 2013

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Interpretationsoflocalfieldpotentials(LFPs)aretypicallyshapedonanassumptionthatthebrainisahomogenousconductivemilieu.However, microscale inhomogeneities including cell bodies, dendritic structures, axonal fiber bundles and blood vessels are unequivocally present and have different conductivities and permittivities than brain extracellular fluid. To determine the extent to which these obstructions affect electrical signal propagation on a microscale, we delivered electrical stimuli intracellularly to individual cells while simultaneously recording the extracellular potentials at different locations in a rat brain slice. As compared with relatively unobstructed paths, signals were attenuated across frequencies when fiber bundles were in between the stimulated cell and the extracellular electrode. Across group of cell bodies, signals were attenuated at low frequencies, but facilitated at high frequencies. These results show that LFPs do not reflect a democratic representation of neuronal contributions, as certain neurons may contribute to the LFP more than others based on the local extracellular environment surrounding them.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Microscale Inhomogeneity of Brain Tissue Distorts Electrical Signal Propagation

et al. 2013

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“…Taking into account ionic diffusion requires to revise the "forward" approach, because the attenuation law does not follow a 1/r 2 law but rather a Yukawa-type law, while the extracellular medium is associated to a Warburg-type impedance. In a previous study, we showed that indeed a Warburg-type impedance could account for the transfer function between intracellular and extracellular potentials [19] (for frequencies comprised between 3 and 300 Hz). It is also consistent with measurements of conductivity and permittivity [12] (but see Ref.…”

Section: Discussionmentioning

confidence: 89%

Generalized theory for current-source-density analysis in brain tissue

Bédard

Destexhe

2011

Phys. Rev. E

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The current-source density (CSD) analysis is a widely used method in brain electrophysiology, but this method rests on a series of assumptions, namely that the surrounding extracellular medium is resistive and uniform, and in some versions of the theory, that the current sources are exclusively made by dipoles. Because of these assumptions, this standard model does not correctly describe the contributions of monopolar sources or of nonresistive aspects of the extracellular medium. We propose here a general framework to model electric fields and potentials resulting from current source densities, without relying on the above assumptions. We develop a mean-field formalism that is a generalization of the standard model and that can directly incorporate nonresistive (nonohmic) properties of the extracellular medium, such as ionic diffusion effects. This formalism recovers the classic results of the standard model such as the CSD analysis, but in addition, we provide expressions to generalize the CSD approach to situations with nonresistive media and arbitrarily complex multipolar configurations of current sources. We found that the power spectrum of the signal contains the signature of the nature of current sources and extracellular medium, which provides a direct way to estimate those properties from experimental data and, in particular, estimate the possible contribution of electric monopoles.

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“…Despite this, questions surrounding their interpretation still remain unanswered, but they have been a recent topic of renewed interest in the literature (Bedard et al 2010;Katzner et al 2009;Logothetis et al 2007;Xing et al 2009). …”

mentioning

confidence: 99%

Physical model of coherent potentials measured with different electrode recording site sizes

Nelson

Pouget

2012

Journal of Neurophysiology

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A question that still complicates interpretation of local field potentials (LFPs) is how electrode properties like impedance, size, and shape affect recorded LFPs. In addition, how any such effects should be considered when comparing LFP, electroencephalogram (EEG), or electrocorticogram (ECoG) data has not been clearly described. A generally accepted concrete physical model describes that an electrode records the spatial average of the voltage across its uninsulated tip, yet the effects of this spatial averaging on recorded coherence have never been modeled. Using simulations based on this physical model, we show here that for any effects to occur, a spatial voltage gradient on a scale smaller than an electrode's recording site must exist over the site's surface. When this occurs, larger electrodes on average report higher coherence between locations, with the effect continuously increasing as the voltage profile over the extent of the recording site is increasingly nonuniform. We quantitatively compared published coherence estimates of LFP, ECoG, and EEG data across a range of studies and found a possible modest effect of electrode size in published ECoG data only. We used the model to quantify the expected coherence for any electrode size in relation to any given spatial frequency of a voltage profile. From this and existing estimates of the spread of voltages underlying each of these data types, our simulations quantitatively agree with the published data and importantly suggest that LFP coherence will be independent of recording site size within the range of microelectrodes typically used for extracellular recordings.

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Evidence for frequency-dependent extracellular impedance from the transfer function between extracellular and intracellular potentials

Cited by 58 publications

References 33 publications

Microscale Inhomogeneity of Brain Tissue Distorts Electrical Signal Propagation

Microscale Inhomogeneity of Brain Tissue Distorts Electrical Signal Propagation

Generalized theory for current-source-density analysis in brain tissue

Physical model of coherent potentials measured with different electrode recording site sizes

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