Presynaptic mechanisms contribute to STD differences along the tonotopic axis. A, Ten representative traces of a recording of a low CF cell. B, Expanded time base for pulses 1 and 15, with calculated CV. C, Calculated CV of populations for 50 (i), 100 (ii), and 200 (iii) Hz. High CF cells had a lower rested CV than their low CF counterparts (n = 17 and 16 for high and low CF, means = 0.079 ± 0.021 and 0.140 ± 0.179, p = 0.029, Student's t test).