Pupillary oscillations accompany hand movement planning in naturalistic scenes

Pupil diameter changes may be a useful signal source for noninvasive studies of motion planning. However, the pupil is also sensitive to luminance changes, making it difficult to study pupillary signals under natural conditions. Here we used pupillary hippus, a luminance-insensitive measure of high-frequency pupil dynamics while human participants planned naturalistic reaches in virtual reality. We found that hippus is significantly increased during planning compared to both rest and movement execution epoch. This finding shows pupillary dynamics change during motion planning reflecting preparatory processes. Most importantly, we demonstrate the potential of a new pupillometric method to study motion planning in natural conditions.