Figure 2.
Extracellular signatures of phase-modulated spiking in a pyramidal cell population. A, Illustration of the model. The 9416 pyramidal cells were randomly distributed with their soma centers in a 40-μm-thick circular disk with 1 mm diameter. Ve values were calculated along a virtual electrode shank oriented along the central axes of the disk. Layer abbreviations: o, Stratum oriens; p, stratum pyramidale; r, stratum radiatum; lm, stratum lacunosum-moleculare. B, Extracellular potentials in stratum pyramidale arising from AP currents in randomly and rhythmically spiking populations with varying modulation frequency and three different average firing rates (2, 4, 6% per 10 ms). Histograms of APs are shown above the corresponding voltage traces. C, Averaged FFT power spectra over 25 trials for Ve in stratum pyramidale. Spectra are shown for each case from B and for two additional frequencies (250 and 350 Hz). Note that the unmodulated spiking spectra (grayscale in B) are not visible because the maximum value in the most active case shown is 2.2 × 10−7. Power spectral densities (psds) throughout this manuscript were estimated using the multitaper method with a time-bandwidth product of 4 and an 8192-point FFT (Percival and Walden, 1993), so the arbitrary psd units (a.u.) are consistent in all figures.