Figure 3.

Nonlinear response interactions. A, Schematic of stimulus triplet. For the sequence C₂→C₁→T, the test response is measured under two scenarios. First, delay u₁ was fixed at 60 ms, and u₂ varied over the range 0–200 ms in 10 ms increments. Next, u₂ was fixed at 60 ms as u₁ varied over the same range. B, PSTH responses for the sequence C₂→C₁→T (specifically, PV→AV→PV) for different values of delay u₂. The leftmost plot shows the first-order test (PV) response. To its right, the response to the pairwise sequence AV→PV is shown (u₁ = 60 ms). The next three plots show the response to the third-order sequence PV→AV→PV as the delay u₁ was fixed at 60 ms, whereas u₂ equaled 200, 70, and 10 ms, respectively. C, The third-order normalized spike counts (fractional test response curves) for the cell shown in B are shown as functions of u₂ (left, ▪; u₁ = 60 ms) and of u₁ (right, ▪; u₂ = 60 ms). Error bars show ±1 SEM. The gray bands represent the corresponding measurements (and their associated uncertainties) for the second-order sequence C₁→T over the same delay range u₁ and u₂ (mean ± 1 SEM).