Fig. 3

Typical representation of a hippus kinetic in each duration category from the same participant. The raw hippus kinetics in the supine position with (a) short-, (b) intermediate-, and (c) long-durations are shown in orange, and the modeled kinetics are superimposed in brick red dashed lines. (d-f) The same analysis in the standing position, with raw kinetics shown in green. Note the good fit quality, with r² values ranging from 0.88 (c) to 0.99 (b) for this participant, despite the measurement noise inherent to the small amplitudes of spontaneous pupil variations present in more than half of the hippus. Moreover, the duration of the constriction phase was systematically shorter in the supine than in the standing position.  Blue rectangle = parasympathetic impulse (\(\:Imp1\)),  orange rectangle = parasympathetic-sympathetic co-activation impulse (\(\:Imp2\)),  green rectangle = sympathetic impulse (\(\:Imp3\)).