Fig. 4.
Definition of tilt tuning and generalization to conjunctive azimuth and tilt tuning. A: model cell tuned to azimuth only. Top: azimuth tuning curve of the model cell when upright (κ = 3.7 and kG = 0.51 where κ is the von Mises function’s parameter and kG is maximum tuning gain). Bottom: tilt-dependent azimuth tuning curve of a model cell tuned to azimuth only as in Fig. 3A, with the tilt axis ranging from 0° to 360°). B: model cell tuned to tilt only. Top: tilt tuning curve. In this example, the baseline and peak firing as well as the cell’s tuning width are identical as in A (λ = 3.7, kTilt = 0.51, where λ is the coefficient of the von Mises distribution and kTilt a gain factor). Bottom: simulated response as a function of azimuth and tilt angle. Tilt tuning is independent of azimuth and peaks at 135°. C and D: model cell tuned conjunctively to both azimuth and tilt. Conjunctive tuning curve, assuming that tilt and azimuth tuning interact either multiplicatively (C) or additively (D). Note that, for simplicity, we express tilt along one axis only here (e.g., pitch or roll). For better readability, all two-dimensional firing rate maps have been scaled to a peak value of 1. a.u., Arbitrary units; FR, firing rate.