Limits...
Decoupling action potential bias from cortical local field potentials.

David SV, Malaval N, Shamma SA - Comput Intell Neurosci (2010)

Bottom Line: This filtering procedure can be applied for well-isolated single units or multiunit activity.We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex.We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

View Article: PubMed Central - PubMed

Affiliation: Institute for Systems Research, University of Maryland, College Park, MD 20742, USA. svd@umd.edu

ABSTRACT
Neurophysiologists have recently become interested in studying neuronal population activity through local field potential (LFP) recordings during experiments that also record the activity of single neurons. This experimental approach differs from early LFP studies because it uses high impedence electrodes that can also isolate single neuron activity. A possible complication for such studies is that the synaptic potentials and action potentials of the small subset of isolated neurons may contribute disproportionately to the LFP signal, biasing activity in the larger nearby neuronal population to appear synchronous and cotuned with these neurons. To address this problem, we used linear filtering techniques to remove features correlated with spike events from LFP recordings. This filtering procedure can be applied for well-isolated single units or multiunit activity. We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex. We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

Show MeSH

Related in: MedlinePlus

Effect of removing spike-correlated activity on the frequency tuning of LFP in A1. (a) Frequency tuning curves for site shown in Figure 2. Gaussian fits are plotted with dashed lines and best frequency (peak of the Gaussian fits) is indicated by arrows. The raw LFP tuning curve was centered at a higher best frequency than the SUA4 curve (0.92 octaves above SUA4, P = .007, jackknifed t-test). After the SUA4-coupled component was removed, the LFP tuning curve was shifted to even higher frequencies (1.63 octaves above SUA4, P = .01, jackknifed t-test). Similar curves to this last case are observed for the LFP signals with SUA3 and MUA components removed. (b) Tuning curves for site shown in Figure 3 (plotted as in A). For this site, there was no significant difference between the SUA and LFP tuning curves (<0.1 octave difference), even after the spike-coupled component was removed from the LFP.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2821772&req=5

fig6: Effect of removing spike-correlated activity on the frequency tuning of LFP in A1. (a) Frequency tuning curves for site shown in Figure 2. Gaussian fits are plotted with dashed lines and best frequency (peak of the Gaussian fits) is indicated by arrows. The raw LFP tuning curve was centered at a higher best frequency than the SUA4 curve (0.92 octaves above SUA4, P = .007, jackknifed t-test). After the SUA4-coupled component was removed, the LFP tuning curve was shifted to even higher frequencies (1.63 octaves above SUA4, P = .01, jackknifed t-test). Similar curves to this last case are observed for the LFP signals with SUA3 and MUA components removed. (b) Tuning curves for site shown in Figure 3 (plotted as in A). For this site, there was no significant difference between the SUA and LFP tuning curves (<0.1 octave difference), even after the spike-coupled component was removed from the LFP.

Mentions: We compared the auditory tuning of spiking activity, raw LFP and clean LFP in order to see if coupled spiking activity significantly influences tuning of the LFP signal. Responses were measured to band-pass noise stimuli centered at logarithmically spaced frequencies (see Methods for details). Figure 6(a) compares the tuning of the onset response of each of these signals for the site shown in Figure 2. The response of the SUA4 signal was measured from the average firing rate during 150 ms after stimulus onset, and the response of the LFP signals was measured by their standard deviation during the same 150 ms period. Baseline activity (absent any stimulus) was subtracted from each tuning curve. The SUA4 tuning curve was normalized to a maximum value of 1, and all the LFP signals were normalized by the same value so that the peak of the raw L0 signal also had a maximum of 1. Each tuning curve (solid line) was overlaid with a minimum mean-square error Gaussian fit (dashed line), whose parameters indicate basic tuning properties such as BF (mean of the Gaussian) and bandwidth (width of the Gaussian). Tuning curves were centered on the BF of the SUA4 signal.


Decoupling action potential bias from cortical local field potentials.

David SV, Malaval N, Shamma SA - Comput Intell Neurosci (2010)

Effect of removing spike-correlated activity on the frequency tuning of LFP in A1. (a) Frequency tuning curves for site shown in Figure 2. Gaussian fits are plotted with dashed lines and best frequency (peak of the Gaussian fits) is indicated by arrows. The raw LFP tuning curve was centered at a higher best frequency than the SUA4 curve (0.92 octaves above SUA4, P = .007, jackknifed t-test). After the SUA4-coupled component was removed, the LFP tuning curve was shifted to even higher frequencies (1.63 octaves above SUA4, P = .01, jackknifed t-test). Similar curves to this last case are observed for the LFP signals with SUA3 and MUA components removed. (b) Tuning curves for site shown in Figure 3 (plotted as in A). For this site, there was no significant difference between the SUA and LFP tuning curves (<0.1 octave difference), even after the spike-coupled component was removed from the LFP.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821772&req=5

fig6: Effect of removing spike-correlated activity on the frequency tuning of LFP in A1. (a) Frequency tuning curves for site shown in Figure 2. Gaussian fits are plotted with dashed lines and best frequency (peak of the Gaussian fits) is indicated by arrows. The raw LFP tuning curve was centered at a higher best frequency than the SUA4 curve (0.92 octaves above SUA4, P = .007, jackknifed t-test). After the SUA4-coupled component was removed, the LFP tuning curve was shifted to even higher frequencies (1.63 octaves above SUA4, P = .01, jackknifed t-test). Similar curves to this last case are observed for the LFP signals with SUA3 and MUA components removed. (b) Tuning curves for site shown in Figure 3 (plotted as in A). For this site, there was no significant difference between the SUA and LFP tuning curves (<0.1 octave difference), even after the spike-coupled component was removed from the LFP.
Mentions: We compared the auditory tuning of spiking activity, raw LFP and clean LFP in order to see if coupled spiking activity significantly influences tuning of the LFP signal. Responses were measured to band-pass noise stimuli centered at logarithmically spaced frequencies (see Methods for details). Figure 6(a) compares the tuning of the onset response of each of these signals for the site shown in Figure 2. The response of the SUA4 signal was measured from the average firing rate during 150 ms after stimulus onset, and the response of the LFP signals was measured by their standard deviation during the same 150 ms period. Baseline activity (absent any stimulus) was subtracted from each tuning curve. The SUA4 tuning curve was normalized to a maximum value of 1, and all the LFP signals were normalized by the same value so that the peak of the raw L0 signal also had a maximum of 1. Each tuning curve (solid line) was overlaid with a minimum mean-square error Gaussian fit (dashed line), whose parameters indicate basic tuning properties such as BF (mean of the Gaussian) and bandwidth (width of the Gaussian). Tuning curves were centered on the BF of the SUA4 signal.

Bottom Line: This filtering procedure can be applied for well-isolated single units or multiunit activity.We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex.We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

View Article: PubMed Central - PubMed

Affiliation: Institute for Systems Research, University of Maryland, College Park, MD 20742, USA. svd@umd.edu

ABSTRACT
Neurophysiologists have recently become interested in studying neuronal population activity through local field potential (LFP) recordings during experiments that also record the activity of single neurons. This experimental approach differs from early LFP studies because it uses high impedence electrodes that can also isolate single neuron activity. A possible complication for such studies is that the synaptic potentials and action potentials of the small subset of isolated neurons may contribute disproportionately to the LFP signal, biasing activity in the larger nearby neuronal population to appear synchronous and cotuned with these neurons. To address this problem, we used linear filtering techniques to remove features correlated with spike events from LFP recordings. This filtering procedure can be applied for well-isolated single units or multiunit activity. We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex. We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

Show MeSH
Related in: MedlinePlus