Figure 7.

Adult oscillatory neurons appear to tonically inhibit Area X-projecting HVC neurons and control their firing through release from inhibition. Neurons were identified as α-oscillators based on peak autocovariances in the range 8–20 Hz. (A–C) Each panel shows a dot raster (top), cross-covariance (middle), and coherency (bottom) spike train relationships between an α-oscillator and HVC_X. All data in each panel are temporally aligned. Data in A–C are from three different adult animals. The top panel shows the spike times of the α-oscillators relative to the spike of an HVC_X that fired at time t = 0 ms. Note the ≥4 ms gap in activity that surrounds time t = 0 ms, which suggests that these neurons released the HVC_X from inhibition, allowing it to fire. Because each of these pairs was recorded on the same tetrode, the measure at exactly t = 0 cannot be trusted, due to overlapping waveforms. The bottom panel shows the coherency and thin gray error traces that indicate 3× jackknife STD. The insets show data on an expanded time scale near zero. Note the dip below the error, indicating signifi-cant negative coherency, at time zero. Bin size for the dot rasters and cross-covariance/coherency calculations was 1 ms.