Solid bars show schematic illustrations of some of the stimuli used in this and other studies. Only the first seven pulses in each train are shown. The open bars in part (c) illustrate a possible pattern of CAP responses.
Psychometric functions showing the percentage of trials in which the isochronous comparison sound, whose period is given on the abscissa, was judged higher than 3.5–5.5 (diamonds), 4–6 (squares), and 4.5–6.5 (triangles) standard stimuli. Data are averaged across the NH listeners of experiment 1.
Part (a) shows the Point of Subjective Equality (“PSE”) derived from the psychometric functions of experiment 1, for 7 NH listeners. The abscissa shows mean interval in each of the three standard sounds tested. Mean data are shown by the heavy dashed line joining squares. The prediction of Carlyon et al.’s (2002) model is shown by the heavy dashed line joining “plus” signs. These two heavy curves overlap, testifying to the success of the model. Part (b) shows the same data, with the PSEs divided by the mean interval in each standard. In both parts of the figure, predictions based on the recovery function described by Fitzpatrick et al. (1999) are shown by filled circles.
As in Fig. 3 , except for the five CI listeners of experiment 2.
Part (a) shows the CAP to a single pulse from one GP of experiment 3a. Part b) shows the response to a SPL 4–6 pulse train in the same animal. The area shown by the dashed box is expanded and illustrated in part (c).
Part (a): Lines connecting symbols show the ratio of CAP amplitudes after 6- vs. 4-ms intervals in a 4–6 pulse train, for each GP of experiment 3a, as a function of stimulus level. The heavy line without symbols shows the mean data. Parts (b) and (c) show the level independence of the modulation in the AN response by plotting the CAP waveform for GP2 at levels of 88 and SPL, respectively.
Part (a) shows the CAP to a stimulus consisting of the first pulse of a 4–6 pulse train, in listener NH2. Part (b) shows the response to part of a 4–6 pulse train in listener NH7. Part (c) shows a zoomed-in portion of part (b). The vertical gridlines are spaced, alternately, by 4 and .
The squares show the recovery function, expressed as response amplitude re that at , necessary for the neural model to account for the NH pitch data from experiment 1. The solid line passing through these points represents the best fit to these data using a logarithmic function. The triangles show the points derived from the GP data of experiment 3b: the ratio between the amplitudes at 5.5 vs 3.5, 6 vs 4, and 6.5 vs reflect the depth of AM in the CAP response to the 3.5–5.5, 4–6, and 4.5–6.5 stimuli, respectively. The vertical distances between other delays (e.g., 3.5 vs. ) were adjusted to provide the best logarithmic fit to the data, shown by the bold solid line. The ratio between these first two curves (faint and bold solid lines) is shown by the dot-dashed line. The bold dashed line shows the two-pulse recovery functions for the cat AN described by Fitzpatrick et al. (1999) , as fit by Carlyon et al. (2002) . The dotted line shows the CAP amplitude to the second pulse in each train as a proportion of that to the first, using data obtained from experiment 3b.
Details of the cochlear implant patients who took part in experiment 2. CSOM refers to chronic serous otitis media. NI refers to noise-induced hearing loss.
(a) Percentage difference between the amplitudes of CAPs measured after the shorter vs. longer intervals for the unmodulated stimuli of experiment 3b. Data from are shown, and are averaged across conditions where the stimulus started with the shorter of the two possible intervals (e.g., in the “4–6” pulse train) and where it started with longer interval (e.g., ). An exception occurred for GP7 in the 8–12 condition, where, due to an error, only stimuli starting with the 8-ms interval were used. Part (b) is similar to (a) but for the 4–6 stimuli of experiment 3b in which the pulses occurring after the longer or shorter intervals could be attenuated by 2 or , thereby producing amplitude modulation. When modulated, only stimuli starting with the shorter of the two intervals were used, and for consistency analysis of the unmodulated stimuli was restricted to those starting with the shorter interval. (This is why the data for the unmodulated stimuli can differ slightly from those shown for the same stimuli in part a). (c) is similar to (b) except for the 8–12 stimuli.
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