Figure 3.

Modulation depth (r₁/r₀) and phase-shift Φ of the response to a noisy oscillatory input. The instantaneous firing rate r(t) evoked by small sinusoidal currents over a noisy background revealed sinusoidal oscillations with amplitude r₁ and phase-shift Φ, around a mean r₀ (quantified as in Fig. 2c,d). Surprisingly, pyramidal neurons can relay fast input modulations, up to several hundred cycles per second. The high-frequency response behavior matches a power-law relationship (i.e., r₁ ∼ f^α) with a linear phase-shift (i.e., Φ ∼ f). These plots were obtained for 67 cells, averaging across available repetitions and distinguishing between offset-currents I₀ above (suprathreshold regime) and below (subthreshold regime) the DC rheobase of the corresponding cell (as in Fig. 5). Data points corresponding to distinct input modulation frequencies were pooled together in nonoverlapping bins with size 0.1–10 Hz (low frequencies) and 100–200 Hz (high frequencies). Error bars represent the SE across the data points available (32 ± 25) for each bin. Markers shape and color identify the suprathreshold or weak-noise regime (black) and the subthreshold or strong-noise regime (red), characterized by distinct values for I₀ and s², adapted to yield a similar mean rate r₀ ∼ 20 Hz (i.e., 19.7 ± 1.5 Hz).