Fig. 6.

Afferent compressive nonlinearity. The first plus second harmonic discharge rate (spk/s) modulation of semicircular canal afferent neurons is shown as a function of stimulus strength for sinusoidal motion at 2 Hz (three animals, 14 neurons). Afferent data were normalized by their responses at 7°/s to allow multiple units to be compared using a single vertical axis. The solid blue line with a slope of 1 (log-log scale) illustrates the response of a linear system in which doubling the stimulus doubles the response. For stimuli below ∼7°/s, most afferent responses fell above the blue line and were more sensitive than would be expected from linear theory. Results for low-strength stimuli exhibited a compressive nonlinearity as demonstrated by a slope significantly <1.