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. 2012 Aug 1;32(31):10594–10608. doi: 10.1523/JNEUROSCI.6045-11.2012

Figure 2.

Figure 2.

Examples of response properties to call stimuli in the primary auditory area L2 and the secondary auditory area CMM. L2 and CMM sites in these examples have been recorded simultaneously. The gray bars indicate call occurrences. A, High-pass-filtered raw recordings (gray lines) are rectified and decimated to yield an AMUA signal (black lines) with a sampling period of 2.5 ms, which reflects the strength of local action potential activity. This signal has been used for most analyses in this study; in some analysis, an AMUA activity threshold was used (see Materials and Methods; here indicated with a dashed line). Shown are two consecutive response epochs, with time relative to the start of the first call in the example, not relative to the start of the call series. The inset shows two action potentials from the CMM signal. B, Raster plots of a random 200 call epochs sorted on presentation order from top to bottom. Note that between-epoch response patterns are stereotypic in L2, and more variable in CMM. The dynamic range of these and other raster plots in this paper has been clipped for visual presentation only. C, Responses during call epochs and silent control epochs (in which no calls were played). Raster plots are sorted on response strength from top to bottom. The call epochs are from the same events as in B, but the sorting order is different. Note that approximately the lower third of the call epochs do not contain any response activity at the CMM sites, whereas the L2 site always shows response activity. Also note that control epochs may contain spontaneous activity. D, Probability density plot of response strengths of call epochs and silent control epochs at the L2 and CMM sites of B and C (n = 200 epochs). In the L2 example, the curves do not overlap, which indicates that this site always responded to call stimulation. In the CMM example, there is a considerable overlap (0.48; the area under each curve is 1.0), which is caused by the site not always responding, as well as by spontaneous activity during silent control epochs.