Figure 4.

Temporal coding properties of pyramidal cells. A, Mean firing in response to SAM stimuli. Mean firing rate (±SE) for both ON (red, n = 19) and OFF (cyan, n = 15) cells in both stimulation configurations (global: pink and pale blue; local: red and cyan) peaks at 5 Hz. B, Phase locking to AM sinusoids is also best at low frequencies. Maximum phase locking is seen at 15 Hz, with the exception of locally stimulated OFF cells, which peak at 5 Hz. C, Mean coherence to noise stimulation is also low pass. ON-cell coherence is shown in red, OFF-cell in cyan. The upper-bound coherence measure (solid line) is based on the response–response correlations between multiple presentations of the stimulus, while the lower bound (dashed line) is based on stimulus–response correlations. Shaded areas indicate SE; darker shading indicates local stimulation. Mean global lower-bound maximums: ON cells, 23.1 Hz (±0.86 SE); OFF cells, 11.6 Hz (±0.75 SE; Wilcoxon rank-sum test, p = 0.04). D, Coding of low-frequency envelopes is poor. Mean (±SE) lower-bound coherence between responses and the low-frequency (0–20 Hz) envelope of a bandpass RAM stimulus (40–60 Hz) are displayed for both local and global stimulus configurations. Both ON and OFF cells exhibit peak envelope tuning at 10.10 Hz (±1.52 SE; Wilcoxon rank-sum test, p = 0.21). OFF cells have noticeably lower coherence to low envelopes than ON cells.