The video showcases a head-restrained mouse with a visible pupil reacting to external stimuli, as evidenced by changes in pupil diameter and direction of gaze. Despite the constant intensity of illumination, fluctuations in pupil diameter are observed, highlighting the role of arousal and attention states in driving these dynamics. The equipment visible in the frame facilitates the precise tracking of ocular and behavioral metrics, essential for studying the neural and physiological correlates of attention and arousal in rodents.