Layer V pyramidal cells action potentials are coherent with and phase-locked to LFPs.

<p>(A) membrane potential (Vm) recording (without DC current injection), with spontaneous action potentials (spikes), together with concurrent (unfiltered) records of LFPs. (B), left panels: Power spectral densities in LFPs are significant (99% above red lines) in beta range, but for Vm are close to spontaneous spike firing rate. Right panels: coherence between Vm and layers V and II LFP is seen in beta range, and harmonics thereof (same recordings as A). (C), upper panel: spike-triggered averages of LFPs from layer V (red) and II (blue), time-locked to each of 84 spikes occurring over a 10 s period (at t = 0 on x-axis). Spikes precede by 2–3 ms the trough, and peak, of the layer V and II oscillations respectively, both of which display a period of around 40 ms. Taken from same cell as in A and B. Lower panel: pooled, normalised, layer V LFP spike-triggered average data (mean ± SEM) from all the 10 recordings that showed significant coherence in the 15–40 Hz range between layer V LFP and Vm (during spontaneous firing). The layer V LFP peak follows the spike by approximately 20 ms. (D), upper panels: Records of (Vm) recorded at rest, during spontaneous spike firing, and of layer V and II LFPs, in absence (left) and presence (right) of bicuculline (10 µM). While spikes persist in bicuculline, LFP oscillations are abolished. Lower panels: significant beta range coherence between Vm and both layer V and II LFP (left) is abolished in bicuculline (right). Different preparation from panels A–C. (E), data pooled from all recordings showing the distribution of frequencies at which significant coherence between LFPs in layer II and layer V, and spikes, was detected, grouped into 3 frequency bands (mean ± SEM in red, n in parentheses).