FIGURE 3.

The strength of auditory response in individual HVC_X neurons typically declined with progressively more accelerated trill rates, but different cells within the same bird could express different types of response (N = 14 cells, 6 birds). a) The response of this cell, also shown in figure 2b–d, was typical of the HVC_X population, with decreasing responses at higher trill rates (top: response raster for each song presentation; middle: histogram of aggregate auditory response; bottom: oscillogram of song stimulus). b) The response of the same cell as in panel a retained its precise relation to specific song features, revealing that reduced peaks in panel a reflect a lower probability of response to each syllable (top: raster of responses to each syllable; middle: histogram of aggregate auditory response; bottom: spectrogram of song syllable). Exceptions to this typical response were also evident. c) A different cell from a different bird maintained its response strength even at maximally accelerated trills. This was the only cell in which such maintenance of response was observed. d) A different cell from the same bird as in panel c expressed strong decrement in response to accelerated trills. The presence of the response in this panel and in panel c among cells in the same bird reveals that the HVC_X population response comprises a diversity of responses to accelerated trills.