Elsevier

NeuroImage

Volume 109, 1 April 2015, Pages 357-367
NeuroImage

Correlates of a single cortical action potential in the epidural EEG

https://doi.org/10.1016/j.neuroimage.2014.12.057Get rights and content
Under a Creative Commons license
open access

Highlights

  • Cortical spikes are coincident with short-lived (~ 0.5 ms) EEG deflections.

  • Cortical spikes produce ~  80 nV epidural EEG deflections at a distance of ~ 5 mm.

  • EEG potentials due to spikes are dominated by high-frequency (> 800 Hz) components.

  • High-frequency (> 800 Hz) EEG is a genuine macroscopic marker of spiking activity.

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 (≈ 0.5 ms) triphasic EEG deflections dominated by high-frequency components > 800 Hz. The peak-to-peak amplitude of the grand-averaged spike correlate was 80 nV, which matched theoretical predictions, while single-neuron amplitudes ranged from 12 to 966 nV. 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.

Keywords

Single-unit activity
EEG
Spike-triggered average
Somatosensory cortex

Cited by (0)