Information Transmission in the Auditory Brainstem Figure 12. Responses of high-sync neurons and ANFs to the whispered /i/ sound. Panel A display the result of the PSD analysis of the whispered /i/ vowel. F1, F2 and F3 represent the approximate location of the respective formants. Panels B and D show dot raster plots of the responses of a high-sync neuron and an ANF, respectively. SACs obtained from responses in B and C are shown in panel C (thin line: high-sync neuron; red thick line: ANF). SACs in panel E were obtained from data from another high-sync/ANF pair, with same CF ( = 900 Hz). doi:10.1371/journal.pone.0044286.g012 neurons and ANFs [7]. The enhancement in temporal processing was quantified using the ‘‘higher peak height or CI’’ [7]. Figures 13A and 13B show the Fourier transform amplitudes of the shuffled autocorrelograms (i.e., PSDs) shown in Figs. 12C and 12E, respectively, using the same conventions of color and line thickness. Maximum values of the two PSDs shown in Fig. 13A happen at frequencies near the frequency of F1. PSDs displayed in Fig. 13B, however, have maximum values occurring at approx- imately 900 Hz—near the units’ CFs. Amplitudes of the largest spectral peaks relative to the second largest ones are lower for the responses of high-sync neurons than for ANFs (Figs. 13A and 13B). This indicates a larger distortion in the representation provided by high-sync neurons than the one provided by ANFs. Figure 13C contains a scatter plot of the frequencies of the maximum values of the PSDs—i.e., the ‘‘dominant components’’ [32]—as a function of CF. For units with CF,700–800 Hz, dominant components in the responses of ANFs and high-sync neurons are ‘‘locked’’ to the F1 frequency. Dominant components in the response of neurons with CFs.800 Hz, however, are similar to the neuron’s CF. PLOS ONE | www.plosone.org 16 September 2012 | Volume 7 | Issue 9 | e44286