Functional properties of neurons in the barn owl Ipc. A) Switch-like suppression of unit responses by a distant, competing stimulus. The stimulus inside the receptive field (RF) was a looming dot (4°/s at 50% contrast). The stimulus outside the RF (Sout), presented simultaneously at a location 30° to the side of the RF center, was either a second 50% contrast looming dot of various speeds (red), a 4°/s looming dot of various contrasts (blue), or a broadband noise burst of various sound levels (green). B) Periodic burst responses of an Ipc unit to a looming dot centered in the RF. Gray zone: duration of the visual stimulus; dashed lines: analysis window for response periodicity. C) Distribution of the peaks in the response power spectrum for 57 Ipc units. Dashed line: mean frequency of response periodicity = 36 Hz. Data from Asadollahi et al., 2010.