Information Transmission in the Auditory Brainstem Figure 3. Single-tone responses of two chinchilla neurons. Panels A, C and E display, respectively, a dot raster plot, a period histogram and a family of iso-intensity curves computed from the responses of a VCN neuron (CF = 350 Hz, Group 1). Similar results for another VCN neuron (CF = 700 Hz, Group 2) are in panels B, D and F. Insets in C and D show PSTHs from responses to tones whose frequency is indicated in the panels. The binwidth of each PSTH is 0.25 ms. Insets in E and F illustrate dot raster plots of the responses of the neuron to 500 and 400 Hz tone stimuli, respectively, at levels indicated in the ordinates (5 presentations per level; each ordinate tick indicates an increment of 10 dB). Stimulus level in E and F is indicated for only certain iso-intensity curves. DR in E and F indicate the increment in maximum firing rate of the neuron relative to the maximum firing rate at CF. Df represents the frequency shift (in octaves) of the CF frequency toward the frequency of the maximum firing rate. Firing rates, except for those indicated by the red dashed lines, were measured during the stimulus duration (0–50 ms). Red dashed lines represent onset firing rate evoked by 90-dB tones. doi:10.1371/journal.pone.0044286.g003 neurons with CFs up to 1 kHz. Open triangles in Fig. 7A represent r values of Group 2 neurons (i.e., neurons with r.0.9 in their responses to single tones at certain off-CF frequencies, but not for stimulus frequencies equal to CF). Open circles in Fig. 7A display maximum r values as a function of CF (i.e., the stimulus frequency that elicits rmax is not necessarily equal to CF) for neurons in Groups 1 and 2. (Values indicated by the open circles in Fig. 7A represent rmax obtained from receptive field data.) Red dots in Fig. 7A represent rmax values for a population of chinchilla ANFs [9] and are analogous to the aforementioned open circles. That is, each red dot in Fig. 7A represents the largest vector strength measured from a family of responses of a neuron to single tones in PLOS ONE | www.plosone.org 7 September 2012 | Volume 7 | Issue 9 | e44286