Fig. 3: γ-Phase-dependent ESA and LFP response of V4 neurons to ICM pulses.

A The heatmap shows the time course of the ICM-evoked ESA exceeding the corresponding unperturbed ESA depending on the phase of the γ-oscillatory excitability cycle at 10 ms (vertical dashed line) after the ICM pulse. The x-axis indicates the time after the ICM pulse, and the y-axis the γ-phase at 10 ms. The average z-transformed ESA values are color-coded (only positive values are shown for clarity). The only significant response is a short peak (highlighted and encircled by a dashed line; p = 0.0017, n = 10,000, bootstrap hypothesis testing, one-sided) that only occurs when the phase of the excitability cycle immediately preceding the response lies within a narrow phase range. Top panel: The blue curve illustrates the time course of the strongest average response observed at an excitability phase of −15°, as indicated in the heatmap by the horizontal thin blue line crossing the peak. The comparatively flat, black dashed line represents the average time course after the ICM pulse across all ESA responses, regardless of the relation between the ICM pulse and the phase of the γ-oscillatory excitability cycle 10 ms later. Right panel: the dependence of response strength on the excitability phase, taken as the mean value across a 2 ms window centered at the peak response (highlighted by the vertical blue area in the heatmap). B Same as in (A), but for the LFP. The heatmap shows the deviation of the LFP in trials following ICMs and the LFP of trials without ICMs, but taken from the same times as a function of the phase of the γ-oscillatory excitability cycle at 10 ms. The area with a significant difference is encircled by a dashed line (p = 0.0005, n = 10.000, bootstrap hypothesis testing, one-sided). Top panel: the dark blue curve shows the time course of the strongest z-scored LFP response at the γ-phase of 0° at 10 ms as indicated by the horizontal dark blue line. Right panel: same as in (A) but for the average z-scored LFP response. All other conventions are equal to (A). C Schematic illustration of the phase progression of the V4 population’s γ-oscillatory excitability cycle (ExC) associated with the strongest ESA response (light blue line), the strongest LFP response (dark blue line), and the strongest RT delay (dark gray line). The red dashed line indicates the excitability phases during which the synaptic input caused by the ICM-evoked V2 spikes is expected to arrive. During these phases, near the excitability peak and shortly before the ESA response onset, the synaptic input causes the maximal effects. Source data are provided as a Source Data file.