Figure 5.

Asymmetric ENV responses of an OC unit, with BF = 10.1 kHz, SR = 0.9 spikes/s, T = 47 dB SPL. A, Pure tone PSTH (50 dB above threshold). B, Receptive field, with a green arrow indicating direction of preference (for the downward-going part of the SFM). C, PSTHs in response to 55 dB SPL SFM presented at BF at 3 modulation depths: 8, 16, and 32% (indicated in different columns) and 3 modulation rates: 2, 5, and 10 Hz (indicated in different rows). D, Period histograms to the modulation rate (similar experimental conditions as in C). Significant vector strength values are indicated by asterisks according to Rayleigh's criterion. E, DSI for all units (SFM at modulation rate = 10 Hz across all modulation depths). Three categories of units are described in the legend: (1) primary-likes and low-frequency (including PL, PN, and LF units), in white circles; (2) choppers (including CS and CT units), in gray triangles; and (3) onsets (including OC, O, OL, and OI units), in squares (OC are represented in black, OL in red, and O and OI in blue). The BFs of OC units varied between 4.1 and 22.3 kHz, whereas those of OL units varied between 1.9 and 14.7 kHz and those of O and OI varied between 2.2 and 9.1 kHz. Individual DSI values are plotted for all units, as well as box plots for the three unit categories. A DSI value of 0 corresponds to a symmetric response to both upward- and downward-going frequencies. A positive DSI value corresponds to a preference for upward-going sweep and a negative DSI value corresponds to a downward-going preference. Significant differences are indicated by asterisks (here, p < 0.0001 in both cases).