Lateral asymmetries of pupillary responses

We wanted to learn if pupillary changes induced by looking and attending to stimuli on the right and left are asymmetrical. In humans, there are hemis pheric asymmetries in the control of attention-arousal systems. Because att ention and arousal may influence pupil size, asymmetric pupillary responses may be seen when looking and attending in different directions. Twelve rig ht-handed, healthy volunteers served as subjects. Using infrared pupillogra phy, we recorded changes of pupillary diameter while subjects were looking and attending to the stimuli on the right and left sides of space. For the one second following a saccade, there are three phasic pupillary responses, an initial constriction (C1) then a dilation (DI), followed by constrictio n (C2). Evaluation of these three responses revealed right-left asymmetries with more pupil dilation (D1) when looking to the stimulus on the right. O ur results suggest that subjects are more aroused when looking to the right than when looking to the left.