Figure 1.

The TTI method was used to determine the BW and arrival time of inhibition. A, In this method, an excitatory tone was delayed or advanced with respect to an inhibitory tone. The intensity of the two tones was the same. Simultaneous onset of the two tones was denoted as 0 ms delay. Later (earlier) onset of the excitatory tone with respect to the inhibitory tone was denoted as positive (negative) delay. B, The TTI tuning curve shows frequency on the x-axis, and the delay of the excitatory tone on the y-axis. The gray bar shows the excitatory frequency tuning curves at the intensity at which the TTI test was performed. The vertical line shows the BF of the neuron. The filled circles were the delay–frequency combinations that caused inhibition of response to the BF tone. Inhibition occurring at negative delays arrived early, whereas inhibition occurring at positive delays arrived late. C, The 50% arrival time of inhibition was the delay of excitatory tone at which an inhibitory tone caused a 50% decrease in control response (BF tone alone response). The horizontal dashed line shows 50% of control response, and the vertical dashed lines indicate the 50% arrival time for two different inhibitory tones.