What is the fine-grained topic of the following text: Two auricular acupuncture points in the ear - "Shenmen" and "Point Zero" - have been studied in post-op patients, and have shown that stimulation of these points "at both auricles increased parasympathetic nerve activity, which is consistent with [previous] studies." Only return the topic.
The effects of auricular acupuncture on post-op patients' parasympathetic nerve activity.