Information Transmission in the Auditory Brainstem Figure 2. Receptive field maps of ANFs and VCN neurons. Top two rows display iso-intensity curves collected in chinchillas. Panels E and F show iso-intensity curves measured in cats. Data from ANFs are in panels A, C and E. VCN units data are in panels B, D and F. Stimulus levels are indicated in some of the curves (e.g., 1 = 10 dB SPL; 4 = 40 dB SPL). Insets in every panel show dot raster plots at several stimulus levels (5 repetitions per level) indicated in the ordinates. Stimulus frequencies are indicated above each dot raster plot. Firing rates, except for those indicated by the red dashed lines, were measured during the stimulus duration (0–50 ms). Red dashed lines represent firing rate evoked by 90-dB tones during the first 20 ms of the response. doi:10.1371/journal.pone.0044286.g002 action potentials are fired only near the onset. This period of activity is followed by a ‘‘quiet’’ period, during which even the spontaneous activity is inhibited. Dot raster plots in Figs. 2B and 2D in responses to 650-Hz and 1200-Hz tones, respectively, display a similar pattern. Red dashed lines in Fig. 2 indicate firing rates computed during the initial 20 ms of the response to 90-dB tones of different frequencies. For VCN units, firing rates computed during the response onset (0–20 ms) resemble those measured during the complete stimulus duration (0–50 ms) for stimulus frequencies below CF. For stimulus frequencies above CF, onset responses are larger than responses measured during the stimulus duration. PLOS ONE | www.plosone.org 5 September 2012 | Volume 7 | Issue 9 | e44286