Figure 6.

Responses to Fixed Sounds Are Modulated by the Spectrotemporal Contrast of their Context

(A) During each electrode penetration, the STRF of a representative unit was used as a basis for a test sound. This was inserted at random times into special DRCs in which stimulus contrast switched every 1 s between low (σ_L = 2.9 dB, c = 33%) and high contrast (σ_L = 8.7 dB, c = 92%). The test sound itself was identical within each stimulus regime; only the contrast of its context differed.

(B) Mean response to the test sound for an example unit, when presented in high-contrast (top row) or low-contrast context (bottom row). Columns delineate responses by the time since the last switch in context at which the test sounds were presented.

(C) Response to the test sound for the unit in (B), averaged within each contrast context over all postswitch delays from 150–800 ms.

(D) Peak responses to the test sound across n = 63 units, during the low- and high-contrast contexts. Red dashed line shows expected response relationship if contrast-context was irrelevant. Green circle indicates the unit in (B) and (C). Shaded region shows the confidence intervals as in Figure 4D.

(E) Peak response for unit in (B) and (C) as a function of the time after context switch at which the test sound was presented. Solid lines show exponential fits to these data, with time constant τ_L→H = 62 ms after an increase and τ_H→L = 85 ms after a decrease in the contrast of the context.

(F) Time constants for context adaptation, as in (E), for 18 units for which both τ_L→H and τ_H→L could be reliably estimated. Data are plotted both as a scatter plot and as marginal histograms of τ_L→H (red) and τ_H→L (blue). Green circle denotes unit in (B), (C), and (E). See also Figure S5.