Figure 7.3i Adaptation Curves. Data from recordings such as those in Figure 7.2i are fit with exponential equations, R_t = R_∞ + R₀e^−t/τ, where R_t is the firing rate at time t, R_∞ is the calculated firing rate if this degree of stretch were maintained infinitely, R_∞ + R₀ is the calculated “initial” peak firing rate at time 0, and τ is the adaptation rate. Thus the inverse of the exponent is the adaptation rate, approximately 4 s in this example.