Figure 5.

Local field potentials show selective increases in fast gamma power following vocal offset. A, Top, average LFP power spectra during Baseline and Post-Vocal periods from an exemplar site. Bottom, A modulation (Mod.) spectrum for this site shows the percentage increase or decrease in fast gamma power during the Post-Vocal period relative to Baseline. This procedure controls for the uneven distribution of power across frequencies in the LFP. B, Average modulation spectra for all sites in each bird are plotted in thin gray lines. The grand average across all five birds is also plotted (thick black line, SEM in dark gray). Note that the grand average spans the entire fast gamma range, but power increases in individual birds only span a portion of the full range. C, Premotor activity and Post-Vocal fast gamma power are correlated across sites within NIf. Data are plotted from five sites recorded from the same electrode. The depth of each recording site is plotted on the x-axis. The average multiunit firing rate during the last 1 s of songs immediately preceding Post-Vocal periods is plotted in solid black. The dotted line represents the average normalized Post-Vocal fast gamma power calculated from LFPs at each site. Standard deviations are indicated with vertical lines.