Correlates of a single cortical action potential in the epidural EEG

Bartosz Teleńczuk,Richard Kempter,Gabriel Curio,Stuart N Baker

doi:10.1016/j.neuroimage.2014.12.057

Bartosz Teleńczuk, Richard Kempter + Show 2 more

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https://doi.org/10.1016/j.neuroimage.2014.12.057

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Abstract

To identify the correlates of a single cortical action potential in surface EEG, we recorded simultaneously epidural EEG and single-unit activity in the primary somatosensory cortex of awake macaque monkeys. By averaging over EEG segments coincident with more than hundred thousand single spikes, we found short-lived (≈0.5ms) triphasic EEG deflections dominated by high-frequency components >800Hz. The peak-to-peak amplitude of the grand-averaged spike correlate was 80nV, which matched theoretical predictions, while single-neuron amplitudes ranged from 12 to 966nV. Combining these estimates with post-stimulus-time histograms of single-unit responses to median-nerve stimulation allowed us to predict the shape of the evoked epidural EEG response and to estimate the number of contributing neurons. These findings establish spiking activity of cortical neurons as a primary building block of high-frequency epidural EEG, which thus can serve as a quantitative macroscopic marker of neuronal spikes.

Highlights

Electric surface potentials recorded from the scalp, from the pia mater, or from the dura mater provide access to neuronal activity in humans and animal models
Epidural EEG potentials are correlated with spikes of cortical neurons
To determine the correlate of a single spike in the epidural EEG, we recorded the local epidural EEG and single-unit activity from neurons localised in the somatosensory cortex of two Macaca mulatta monkeys (29 neurons from monkey A, 11 neurons from monkey B)

Summary

Introduction

Electric surface potentials recorded from the scalp (electroencephalography, EEG; Berger, 1929), from the pia mater (electrocorticography; Foerster and Altenburger, 1935), or from the dura mater (epidural EEG; Noachtar and Rémi, 2009) provide access to neuronal activity in humans and animal models These macroscopic signals have proven indispensable in clinical diagnostics, in research on neuronal correlates of cognitive processes (Friston, 2009) and for operating brain–computer interfaces (Birbaumer et al, 2008). If EEG activity N 400 Hz reflects spiking activity, it might inform about the output of the excitatory/inhibitory balance (Ray et al, 2013)

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